Standard Test Procedure RHD.bd

Government of the People’s Republic of Bangladesh Ministry of Communications Roads and Highways Department

STANDARD TEST PROCEDURES

MAY 2001

GaziSharif

Digitally signed by GaziSharif DN: CN = GaziSharif, C = BD, O = RHD, OU = NRD Reason: I agree to 'specified' portions of this document Date: 2009.10.23 16:29:59 +06'00'

INSERT THE NEW

FOREWARD

SIGNED BY

FAZLUL HAQUE

STANDARD TEST PROCEDURES (STP) Introduction To enable roads and bridges to be built in accordance with the Roads and Highways Department’s Technical Specifications (Volume 3 of 4 of the Standard Tender Documents), it is necessary for quality control tests to be carried out at both construction sites and regional testing centres. The results of these tests are intended to assist the Engineer in deciding whether or not a particular item of work is satisfactory and to provide a permanent record to show the work has been carried out in accordance with the Contract Specification. To be of use to the field engineer the results of many of the tests detailed must be submitted as soon as possible after completion of the particular item of work, as any work which does not conform with the Contract Specification may be rejected by the Engineer. The Standard Test Procedures detailed in this document are mandatory for the quality control of roads constructed by the Roads and Highways Department. The RHD Technical Specifications when including a test make reference to this document and the tests are referred to by their section number and title, for example, STP 4.3 – Standard Compaction of Soil. Standard Laboratory Test forms have been produced for the tests detailed in this document. Sample calculations are shown using these forms in the relevant sections of the document and copies of the blank forms are available for downloading from the Roads and Highways Department’s Internet Web Site at www.rhdbangladesh.org under the section covering Standard Test Procedures. Alternatively a computer ‘ floppy disc’ containing copies of the forms can be purchased from the Procurement Circle at RHD Sarak Bhaban, Ramna, Dhaka. This manual covers all tests which are needed to be carried out at site or regional laboratories; however, other more specialist or complex tests may be required and these can be carried out at the Bangladesh Road Research Laboratory and in this respect, or other matters concerning these Standard Test Procedures, queries should be referred in the first instance to the Director, Bangladesh Road Research Laboratory, Paikpara, Mirpur, Dhaka.

Roads and Highways Department Bangladesh Road Research Laboratory Table of Contents CHAPTER 1 : DEFINITIONS, SYMBOLS AND UNITS 1.1 1.2 1.3 1.4 1.5

Scope...............................................................................................................1.1 Terminology......................................................................................................1.1 Definitions ........................................................................................................1.1 Greek Alphabet.................................................................................................1.5 Symbols and Units............................................................................................1.6

1.6

Conversion Factors and Useful Data .................................................................1.6

CHAPTER 2 : SAMPLING 2.1. 2.2 2.3

General ............................................................................................................2.1 Sampling of Soils..............................................................................................2.1 Sampling of Bricks............................................................................................2.6

2.4 2.5 2.6 2.7 2.8

Sampling of Aggregates....................................................................................2.9 Sampling of Cement .......................................................................................2.12 Sampling of Concrete .....................................................................................2.13 Sampling of Bitumen.......................................................................................2.16 Sampling of Bituminous Materials ...................................................................2.17

2.9 2.10 2.11

Preparing and Transporting Samples..............................................................2.17 Sample Reception ..........................................................................................2.19 Sample Drying................................................................................................2.19

CHAPTER 3 : CLASSIFICATION TESTS 3.1 3.2 3.3 3.4

Determination of Moisture Content....................................................................3.1 Determination of Atterberg Limits ....................................................................3.11 Particle Size Distribution .................................................................................3.22 Determination of Organic Content...................................................................3.32

3.5

Standard Description and Classifications ........................................................3.34

CHAPTER 4 : DRY DENSITY - MOISTURE CONTENT RELATIONSHIPS 4.1

General Requirements ......................................................................................4.1

4.2 4.3 4.4 4.5

Sample Preparation..........................................................................................4.2 Standard Compaction using 2.5 kg Rammer .....................................................4.8 Heavy Compaction using 4.5 kg Rammer........................................................4.19 Vibrating Hammer Method ..............................................................................4.19

I

CHAPTER 5 : STRENGTH TESTS: CALIFORNIA BEARING RATIO AND DYNAMIC CONE PENETROMETER TEST 5.1

California Bearing Ratio (CBR) Test..................................................................5.1

5.2

Dynamic Cone Penetrometer (DCP) Test........................................................5.21

CHAPTER 6 : DETERMINATION OF IN-SITU DENSITY 6.1 6.2 6.3

Introduction.......................................................................................................6.1 Sand Replacement Method...............................................................................6.1 Core Cutter Method ........................................................................................6.10

CHAPTER 7 : TESTS FOR AGGREGATES AND BRICKS 7.1 7.2 7.3 7.4

Determination of Clay and Silt Contents in Natural Aggregates .........................7.1 Particle Size Distribution of Aggregates.............................................................7.5 Shape Tests for Aggregates .............................................................................7.9 Fine Aggregate : Density and Absorption Tests ...............................................7.15

7.5 7.6 7.7 7.8

Coarse Aggregate : Density and Absorption Tests ..........................................7.21 Aggregate Impact Value .................................................................................7.26 Aggregate Crushing Value and 10% Fines Value ............................................7.32 Tests for Bricks...............................................................................................7.39

CHAPTER 8 : TESTS OF CEMENT 8.1 8.2 8.3

Fineness of Cement..........................................................................................8.1 Setting Time of Cement ....................................................................................8.2 Compressive Strength of Cement .....................................................................8.5

CHAPTER 9 : TESTS ON CONCRETE 9.1

Slump Test .......................................................................................................9.1

9.2

Crushing Strength of Concrete ..........................................................................9.5

CHAPTER 10 : TEST FOR BITUMEN AND BITUMINOUS MATERIALS 10.1 10.2 10.3 10.4

Bitumen Penetration Test ...............................................................................10.1 Bitumen Softening Test ..................................................................................10.6 Specific Gravity Test of Bitumen ..................................................................10.12 Bitumen Extraction Tests .............................................................................10.16

10.5 10.6 10.7 10.8

Flash Point and Fire Point Tests of Bitumen .................................................10.33 Viscosity Test of Bitumen .............................................................................10.41 Distillation of Cut-Back Asphaltic (Bituminous) Products ...............................10.51 Float Test of Bitumen ...................................................................................10.57 II

CHAPTER 10 : TEST FOR BITUMEN AND BITUMINOUS MATERIALS 10.9 10.10 10.11 10.12

Marshall Stability and Flow ..........................................................................10.60 Bulk Specific Gravity of Compacted Bituminous Mixtures Test .....................10.76 Maximum Theoretical Specific Gravity of Paving ..........................................10.81 Spray Rate of Bitumen .................................................................................10.86

CHAPTER 11 : STEEL REINFORCEMENT TESTS 11.1

General Requirements ...................................................................................11.1

11.2 11.3

Tension Test of Steel Reinforcing Bar ............................................................11.8 Bend Test of Reinforcing Bar .......................................................................11.14

III

Standard Test Procedures

CHAPTER 1

Definitions, Symbols and Units

CHAPTER 1 DEFINITIONS, SYMBOLS AND UNITS

1.1

Scope

This standard sets out the basic terminology, definitions, symbols and units used in the various parts of the manual, and refers specifically to soils, although some terms may also be applicable when testing other materials. Only the terms commonly in use and most likely to be met in the more routine tests on soils have been included. Conversion factors and other useful data are also included. 1.2

Terminology

The following terminology applies to the soil testing standards. 1.2.1

Soil. An assemblage or mixture of separate particles, usually of mineral composition but sometimes of organic origin, which can be separated by gentle mechanical means and which includes variable amounts of water and air (and sometimes other gases). A soil commonly consists of a naturally occurring deposit, but the term is also applied to made ground consisting of replaced natural soil or man-made materials exhibiting similar behaviour, e.g. crushed brick, crushed rock, pulverised fuel ash or crushed blast-furnace slag.

1.2.2

Cohesive soil. Soil which because of its fine-grained content will form a mass which sticks together at suitable moisture contents.

1.2.3

Cohesionless soil. Granular soil consisting of particles which can be identified individually by the naked eye or by using a magnifying glass, e.g. gravel, sand.

1.3

Definitions

1.3.1

Sample. A portion of soil taken as being representative of a particular deposit or stratum.

1.3.2

Specimen. A portion of a sample on which a test is carried out.

1.3.3

Sampling. The selection of a representative portion of a material.

1.3.4

Quartering. Reducing the size of a large sample of material to the quantity required for test by dividing a circular heap, by diameters at right angles, into four more or less equal portions, removing two diagonally opposite quarters, and thoroughly mixing the two remaining quarters together so as to obtain a truly representative half of the original mass. The process is repeated until a sample of the required size is obtained.

1.3.5

Riffling. The reduction in quantity of a large sample of material by dividing the mass into two approximately equal portions by passing the sample through an appropriately sized sample divider (“riffle box”). The process is repeated until a sample of the required size is obtained. When dividing some coarse-grained materials a combination of quartering and riffling methods may be necessary on different sized fractions of the sample.

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Definitions, Symbols and Units 1.3.6

Dry soil. Soil that has been dried to constant mass at a temperature of 1050C to 1100C. Other drying temperatures. e.g. 600C, may be specified for particular tests.

1.3.7

Moisture content (w). The mass of water which can be removed from the soil, usually by heating at 105 0C, expressed as a percentage of the dry mass. The term water content is also widely used.

1.3.8

Liquid limit (LL). The moisture content at which a soil passes from the liquid to the plastic state, as determined by the liquid limit test.

1.3.9

Plastic limit (PL). The moisture content at which a soil on losing water passes from plastic state to semi-brittle solid state and becomes too dry to be in a plastic condition as determined by the plastic limit.

1.3.10

Plasticity index (PI). The numerical difference between the liquid limit and the plastic limit of a soil : PI = LL – PL

1.3.11

Non-plastic. A soil with a plasticity index of zero or one on which the plastic limit cannot be determined.

1.3.12

Liquidity index (IL). The ratio of the difference between moisture content and plastic limit of a soil, to the plasticity index :

IL =

w - PL PI

1.3.13

Shrinkage limit (ws). The moisture content at which a soil on being dried ceases to shrink.

1.3.14

Linear shrinkage (LS). The change in length of a bar sample of soil when dried from about its liquid limit, expressed as a percentage of the initial length.

1.3.15

Bulk density (ρ). The mass of material (including solid particles and any contained water) per unit volume including voids.

1.3.16

Dry density (ρd ). The mass of the dry soil contained in unit volume of undried material :

ρd =

100ρ 100 + w

1.3.17

Particle density (ρ s). The average mass per unit volume of the solid particles in a sample of soil where the volume includes any sealed voids contained within the solid particles.

1.3.18

Particle size distribution. The percentages of the various grain sizes present in a soil as determined by sieving and sedimentation.

1.3.19

Test sieve. A sieve complying with a recognised Standard.

1.3.20

Cobble fraction. Solid particles of sizes between 200 mm and 60 mm.

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Definitions, Symbols and Units 1.3.21

Gravel fraction. The fraction of a soil composed of particles between the sizes of 60 mm and 2 mm. The gravel fraction is subdivided as follows : Coarse gravel Medium gravel Fine gravel

1.3.22

Sand fraction. The fraction of a soil composed of particles between the sizes of 2.0 mm and 0.06 mm. The sand fraction is subdivided as follows : Coarse sand Medium sand Fine sand

1.3.23

60 mm to 20 mm 20 mm to 6 mm 6 mm to 2 mm

2.0 mm to 0.6 mm 0.6 mm to 0.2 mm 0.2 mm to 0.06 mm

Silt fraction. The fraction of a soil composed of particles between the sizes of 0.06 mm and 0.002 mm. The silt fraction is subdivided as follows : Coarse silt Medium silt Fine silt

0.06 mm to 0.02 mm 0.02 mm to 0.006 mm 0.006 mm to 0.002 mm

1.3.24

Clay fraction. The fraction of a soil composed of particles smaller in size than 0.002 mm.

1.3.25

Fines fraction. The fraction of a soil composed of particles passing a 63 µm test sieve. Note that this includes all material of silt and clay sizes, and a little fine sand. For most practical purposes, the limiting sieve size can be taken to be 75 µm.

1.3.26

Voids. The spaces between solid particles of soil.

1.3.27

Voids ratio (e). The ratio between the volume of voids (air and water) and the volume of solid particles in a mass of soil:

e = 1.3.28

ρs - 1 ρd

(see 1.3.16 and 1.3.17)

Porosity (n). The volume of voids (air and water) expressed as a percentage of the total volume of a mass of soil.

n =

e x 100 (%) l + e

1.3.29

Saturation. The condition in which all the voids in a soil are completely filled with water.

1.3.30

Degree of saturation (Sr ). The volume of water contained in the void spaces between soil particles, expressed as a percentage of the total voids:

Sr =

w ρs (%) e

(see 1.3.7; 1.3.17; 1.3.27)

1.3.31

Compaction. The process of packing soil particles more closely together by rolling or other mechanical means, thus increasing the dry density of the soil.

1.3.32

Optimum moisture content. The moisture content at which a specified amount of compaction will produce the maximum dry density. MAY 2001

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Definitions, Symbols and Units 1.3.33

Maximum compacted dry density. The dry density obtained using a specified amount of compaction at the optimum moisture content.

1.3.34

Relative compaction. The percentage ratio of the dry density of the soil to the maximum compacted dry density of a soil when a specified amount of compaction is used.

1.3.35

Dry density / moisture content relationship. The relationship between dry density and moisture content of a soil when a specified amount of compaction is used.

1.3.36

Percentage air voids (Va). The volume of air voids in the soil expressed as a percentage of the total volume of the soil :

 ρ ρ w  Va = 1 - d  w +   100 (%) ρ w  ρs 100    (see 1.3.7; 1.3.16; 1.3.17; 1.3.37) 1.3.37

Air voids line. A line on a graph showing the dry density / moisture content relationship for soil containing a constant percentage of air voids. The line can be calculated from the equation :

ρd = ρw

where,

ρd ρw Va ρs w

Va   1 - 100  1 w  +   100   ρs

is the dry density of the soil (Mg/m3); is the density of water (Mg/m3); is the volume of air voids in the soil, expressed as a percentage of the total volume of the soil; is the particle density (Mg/m3); is the moisture content, expressed as a percentage of the mass of dry soil.

1.3.38

Saturation line (zero air voids line). A line on a graph showing the dry density / moisture content relationship for soil containing no air voids. It is obtained by putting Va = 0 in the equation given in definition 1.3.37.

1.3.39

Limiting densities. The dry densities corresponding to the extreme states of packing (loosest and densest) at which the particles of a granular soil can be placed.

1.3.40

Maximum density (ρdmax). The maximum dry density at the densest practicable state of packing of particles of a granular soil.

1.3.41

Minimum density (ρdmin). The minimum dry density at the loosest state of packing of dry particles which can be sustained in a granular soil.

1.3.42

Maximum (minimum) porosity or voids ratio. The porosity or voids ratio corresponding to the minimum (maximum) dry density as defined above.

1.3.43

California bearing ratio (CBR). The ratio (expressed as a percentage) of the force required to cause a circular piston of 1935 mm2 cross-sectional area to penetrate the soil from the surface at a constant rate of 1 mm/min, to the force required for similar penetration into a standard sample of crushed rock. The ratio is determined at penetrations of 2.5 mm and 5.0 mm, and the higher value is used. MAY 2001

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Definitions, Symbols and Units

1.3.44

Penetration resistance. The force required to maintain a constant rate of penetration of a probe, e.g. a CBR piston, into the soil.

1.3.45

Consolidation. The process whereby soil particles are packed more closely together over a period of time by application of continued pressure. It is accompanied by drainage of water from the voids between solid particles.

1.3.46

Pore water pressure (u w). The pressure of the water in the voids between solid particles.

1.3.47

Excess pore pressure. The increase in pore water pressure due to the application of an external pressure or stress.

1.3.48

Swelling. The process opposite to consolidation, i.e. expansion of a soil on reduction of pressure due to water being drawn into the voids between particles.

1.3.49

Swelling pressure. The pressure required to maintain constant volume, i.e. to prevent swelling, when a soil has access to water.

1.3.50

Permeability. The ability of a material to allow the passage of a fluid. (Also known as hydraulic conductivity.)

1.3.51

Piping. Movement of soil particles carried by water eroding channels through the soil, leading to sudden collapse of soil.

1.3.52

Erosion. Removal of soil particles by the movement of water.

1.3.53

Dispersive (erodible) clays. Clays from which individual colloidal particles readily go into suspension in particularly still water.

1.3.54

Shear strength. The maximum shear resistance which a soil can offer under defined conditions of effective stress and drainage.

1.4

Greek Alphabet

A number of the symbols traditionally used in soils testing are taken from the Greek alphabet. This is reproduced below for reference purposes: Capital A B Γ ∆ Ε Z H Θ I K Λ M

Small α β γ δ ε ζ η θ ι κ λ µ

Name alpha beta gamma delta epsilon zeta eta theta iota kappa lambda mu

Capital N Ξ O Π P Σ T Y Φ X ψ Ω

MAY 2001

Small ν ξ ο π ρ σ τ υ φ χ ψ ω

Name nu xi omicron pi rho sigma tau upsilon phi chi psi omega

Page 1.5

Standard Test Procedures

CHAPTER 1

Definitions, Symbols and Units 1.5

Symbols and Units

The following symbols are used in the standards in the manual. The symbols generally conform to international usage. The units are those generally used. An asterisk indicates that no unit is used. Term Moisture content Liquid limit Plastic limit Shrinkage limit Plasticity index Liquidity index Bulk density Dry density Particle density Density of water Voids ratio Porosity Degree of saturation Percentage air voids Maximum dry density Minimum dry density Maximum voids ratio Minimum voids ratio California bearing ratio Mean particle diameter Percentage by mass finer than D Elapsed time Unconfined compressive strength

Symbol w LL PL ws PI IL ρ ρd ρs ρw e n Sr Va ρdmax . ρdmin. emax . emin. CBR D K t qu

Unit % % % % % * Kg/m3 Kg/m3 Kg/m3 Kg/m3 * % % % Kg/m3 Kg/m3 * * % mm or µm % minutes or second kPa

1.6

Conversion Factors and Useful Data

1.6.1

General. The modern form of the metric system is known as the SI system. SI is the accepted abbreviation for Systeme International d’Unites (International System of Units), the system finally agreed at an international conference in 1960.

1.6.2

Conversion factors. Conversion factors for SI and imperial units are given in Table 1.6.1.

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Definitions, Symbols and Units Table 1.6.1

CONVERSION FACTORS, IMPERIAL AND SI UNITS.

Imperial to SI Length

Area

Volume

Mass

Density Force Pressure

1.609 0.3048 25.4 0.4045 0.09590 645.2 0.764 0.02832 4.546 3.785 28.32 16.39 16387 1.016 0.4536 453.6 28.35 0.01602 9.964 4.448 0.04788 6.895 47.88

km m mm hectare (ha) m2 mm2 m3 m3 litre litre litre ml mm3 Mg (tonne) kg g g Mg/m3 (g/cm3) kN N kN/m2 (kPa) kN/m2 N/m2 (Pa)

: : : : : : : : : : : : : : : : : : : : : : :

mile foot (ft) inch (in) acre square foot square inch cubic yard cubic foot gallon (UK) gallon (USA) cubic foot cubic inch cubic inch ton pound (lb) pound ounce (oz) pound per cubic foot ton force pound force lb f/sq ft lb f/sq in lb f/sq ft

SI to Imperial 0.6215 3.281 0.03937 2.471 10.76 0.001550 1.3089 35.34 0.2200 0.2642 0.03531 0.06102 0.9842 2.205 0.03527 62.43 0.1004 0.2248 20.89 0.1450 0.02089

NOTE 1 litre (L) = 1,000 cm3 = 1,000 mL 1 kN = 1,000 N 1MN/m2 = 1 N/mm2

1 tonne = 1,000 kilograms (kg) 1 kg = 1,000 grams (g) 1 kgf = 9.81 N 1 tonne f = 9.81 kN

1 Megagram (Mg)/m3 = 1,000 kg/m3 1 Megagram/m3 = 1 g/cc

Examples To convert imperial to SI, e.g. to convert feet to metres, multiply number of feet by 0.3048. To convert SI to imperial, e.g. to convert metres to feet, multiply number of metres by 3.281. 1.6.3

Useful data and information

1.6.3.1

Standard gravity. The international standard acceleration due to the earth’s gravity is accepted as; g = 9.80665 m/s2 although it varies slightly from place to place. For practical purposes g = 9.81 m/s2, the conventional reference value used as a common basis for measurements made on the Earth.

1.6.3.2

Mass. The kilogram (kg) is equal to the mass of the international platinum prototype kept by Bureau International des Poids et Measures (BIPM) at Sevres. It is the only basic quantity to be a multiple unit : 1 kg = 1,000 g (grams) MAY 2001

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Standard Test Procedures

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Definitions, Symbols and Units

There is no SI unit of ‘weight’. When ‘weight’ is used to mean the force due to gravity acting on a mass, the mass (kg) must be multiplied by g(9.81 m/s2) to give the force in Newton’s (N). 1.6.3.3

Density. The megagram per cubic metre (Mg/m3) is the density unit adopted for soil mechanics. It is 1000 times larger than the kilogram per cubic metre, the basic SI unit, and is equal to one gram per cubic centimetre : 1 Mg/m3

= 1 g/cm3 = 1,000 kg/m3

The density of soil particles (particle density) is expressed in Mg/m3, which is numerically equal to the specific gravity (now obsolete). Using Mg/m3, the density of water is unity. 1.6.3.4

Force. The Newton (N) is that force which, applied to a mass of 1 kilogram, gives it an acceleration of 1 metre per second per second. 1 N = 1 kg m/s2 The kilonewton (kN) is the force unit most used in soil mechanics: 1 kN = 1,000 N = approximately 0.1 tonne f or 0.1 ton f

1.6.3.5

Pressure and stress. The Pascal (Pa) is the pressure produced by a force of 1 Newton applied, uniformly distributed, over an area of 1 square metre. The Pascal has been introduced as the pressure and stress unit, and is exactly equal to the Newton per square metre: 1 Pa = 1 N/m2 In dealing with soils the usual unit of pressure is kilonewton per square metre (kN/ m2), or kilopascal: 1 kN/m2 = 1 k Pa = 1,000 N/m2 The bar is not an SI unit but is sometimes encountered in fluid pressure: 1 bar = 100 kN/m2 = 100 k Pa = 1000 mb (millibars)

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Definitions, Symbols and Units 1.6.3.6

Comparison of BS and ASTM sieve sizes BS sieve aperture size 75 mm 63 50 37.5 28 20 14 10 6.3 5 3.35 2 1.18 600 µm 425 300 212 150 75 63

Sieves to ASTM D422 Nearest designation Aperture size 3 inch 75 mm 21/2 inch 63.5 2 inch 50.8 11/2 inch 38.1 1 inch 25.4 ¾ inch 19.05 3 /8 inch 9.52 No. 4 4.75 No. 6 3.35 No. 8 2.36 No. 10 2.00 No. 16 1.18 No. 20 850 µm No. 30 600 No. 40 425 No. 50 300 No. 60 250 No. 70 212 No. 100 150 No. 140 106 No. 200 75 No. 230 63

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CHAPTER 2

Sampling

CHAPTER 2 SAMPLING

2.1

General

This standard deals with the sampling of soils, bricks, aggregates, cement, concrete, bitumen and bituminous materials. A sample is a small quantity of material which represents in every way, a much larger quantity of material. In taking a sample we are not usually attempting to select the best or worst examples of the materials used but the typical material as used in the works. Sampling should therefore be done on a completely random basis and personal preferences should not be allowed to interfere with the selection. 2.2

Sampling of Soils

Samples are of one of two main types: disturbed or undisturbed. 2.2.1

Disturbed samples. Usually taken with a pick and shovel, scoop or other appropriate hand tool, care should be taken to prevent coarse material from rolling off the sides of the tool, which will leave behind too fine a sample. Disturbed samples can be taken in test pits, trenches or similar excavations, auger holes and boreholes. Disturbed samples can also be taken from stockpiles of material and from material laid during road construction. Small disturbed samples can also be available as the result of carrying out other work, e.g. samples from the Standard Penetration Test (SPT) shoe, and samples from the cutting shoe of undisturbed sample tubes.

2.2.1.1

Techniques. The sampling technique employed will be influenced by factors such as the type and quantity of material being sampled, the equipment available, physical constraints of the sampling location, the intended use of the material being sampled.

2.2.1.1.1 Test pits. Based upon the changes in moisture condition, colour consistency, soil type, structure etc., the sides of the test pit are inspected to their full depth and any observable change is recorded with depth. Any vegetation growing around the upper edge of the test pit should be removed. Now every distinguishable gravel, soil or sand layer should separately sampled by holding a spade or canvas sheet at the lower level of the layer against the side of the pit and by cutting a sheer groove to the full depth of the layer with a pick or spade. If the test pit had been dug sometimes before, then weathered material should be removed from the surface before sampling. The material obtained in this way should be placed in sample bags. The canvas sheet may also be spread out on the floor of the test pit if this is more convenient. Once all the layers have been sampled, all of the material from a particular layer must be combined on either a clean, hard, even surface or on a canvas sheet and properly mixed with a spade. The material sampled should not be contaminated with other material. Samples should preferably be sealed in airtight tins and should fill the tin completely. Duplicate or even triplicate samples should be taken. If the bulk sample is too large, quarter or riffle out into sample bags a representative sample of the layer as explained earlier. The sample bags must be clearly and indelibly marked, so that the samples can be identified in the laboratory. All test pits should be properly fenced to safeguard villagers and animals.

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Sampling Caution: It is recommended that in any case no excavation deeper than 1.5m should be made unless: a) It is properly propped and braced b) The gradient of the sides is at least equal to the natural angle of repose of the soil. c) It is in firm rock. 2.2.1.1.2 Stockpiles. When sampling from a stockpile the material on the top and sides of the pile must not be used as this is generally coarser than the interior of the stockpile. The correct procedure is to dig small holes in the stockpile (Figure 2.2.1) and sample the material from the base of these holes. At least ten holes must be made at different places on the stockpile and the materials obtained should be thoroughly mixed together. However, stockpiles are often scraped together in natural material with bulldozers, in which case it is better to wait until the stockpile has been completed before taking samples. Samples will be carried out using hand tools. Sampling can also be done using a mechanical loader-digger (in large stockpiles). Samples may be collected by using two shovels perpendicularly, one to prevent material falling on to the samples and one to clean off and take the sample (Figure 2.2.2). Samples may also be collected by digging a groove from the top to the bottom of the stockpile (Figure 2.2.3). Table 2.2.1 Type of Test Moisture content Atterberg limits Particle size distribution (sieving) Particle size distribution (sedimentation) Particle density MDD test California bearing ratio pH value

Finegrained 50 g 1 kg 150 g 250 g 1.5 kg 80 kg 6 kg 150 g

Soil Group* MediumCoarse-grained grained 350 g 4 kg 1.5 kg 2.5 kg 2.5 kg 17 kg 100 g** 100 g** 2 kg 4 kg 80 kg 80 kg 6 kg 12 kg 600 g 3.5 kg

Mass of sample required for each test on disturbed samples is given in Table 2.2.1. These masses include some allowance for drying, wastage and rejection of stones where required. Multiply these masses by the number of tests required. Where appropriate, these masses assume that soils are susceptible to crushing. ** Sufficient to give the stated mass of fine-grained material. * Soil group i) Fine-grained soils: Soils containing not more than 10% retained on a 2 mm test sieve. ii) Medium-grained soils: Soils containing more than 10% retained on a 2 mm test sieve but not more than 10% retained on a 20 mm test sieve. iii) Coarse-grained soils: Soils containing more than 10% retained on a 20 mm test sieve but not more than 10% retained on a 37.5 mm test sieve. A soil shall be regarded as belonging to the finest-grained group as appropriate under the above definitions. 2.2.1.1.3 Road pavement layers. When sampling from a partly constructed road pavement, for example in crushed brick consolidation work, several small areas should be marked out and all the material must be collected from the excavated holes or trenches of each area. Care must be taken to ensure all the fine material is collected by using small tools like brushes. Undisturbed samples are not generally taken in roadwork layers. Corecutters used primarily in fine grained soils for in-situ density determination can also provide an undisturbed sample.

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Sampling 2.2.2

Undisturbed samples. It is extremely difficult to obtain a truly “undisturbed” sample. Samples generally described as undisturbed can be taken in the form of excavated blocks, from which test specimens are later prepared, or in metal tubes fitted with sharpened cutting shoes. Sample tubes of this type are driven or jacked into the ground using a variety of methods and the sample are more frequently taken in boreholes using machine-operated equipment, but can also be obtained in test pits using handoperated equipment.

2.2.2.1

Techniques

2.2.2.1.1 Block samples. Cohesive material in test pits or other locations can be sampled in blocks by carefully cutting away surrounding material and then undercutting the block to remove it. 2.2.2.1.2 Samples in moulds and tubes. Metal tubes for taking undisturbed samples are commonly 75 mm or 100 mm φ and 450 mm long (known as U3 or U4 tubes) or 38 mm φ and 230 mm long. The latter are convenient for use in test pits, when they can be driven by using a hammer or preferably by a driving dolly. On ejection and trimming, the samples are suitable sizes for triaxial testing. The larger sample tubes are fitted with detachable cutting shoes and are generally driven using mechanised equipment or hand-operated hammering device. Considerable care is required to maintain the verticality of the tube when driving it. Samples in tubes or block sample should be carefully waxed after removing just enough of the top of the sample with a palette knife to form a flat surface. 2.2.3

Labeling sample. The sample must be comprehensively labeled. The label should include information from the following list, as appropriate; a) b) c) d) e) f) g) h) i) j) k) l) m) n)

Name of the project Name of the sampler Date and time of sampling Location within project: chainage; offset; carriageway; construction area, etc. Depth of sample below reference datum, e.g. finished road level Sample number Description of the layer Description of the material Test pit; borehole; auger hole number Type of sample Sampling method Supplier’s name Source of material Number and type of container(s), and the number(s) with which the containers are marked o) How samples are being sent p) Registration number of sampled truck q) Additional information, e.g. how the material was processed before sampling. Metal tubes should be labeled on the side of the tube and not on the end cap. The end of the metal tube marking the top of the stratum should be so marked (i.e. with a T). The present system uses pre-printed ‘Sample Record Cards’, shown as Form 2.2.1.

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Sampling 2.3

Sampling of Bricks

2.3.1

Scope. The scope of this standard is to provide methods of sampling bricks without bias and to give guidance as to the frequency and size of samples required for testing. The physical form of the consignment of bricks will normally dictate the choice and method of sampling. No special equipment is required for sampling bricks.

2.3.2

Sampling methods. The sample may be drawn either by a) random sampling; or b) stratified sampling. 1.

Sampling in motion

Whenever practicable a sample shall be taken whilst the bricks are being moved for example during loading or unloading. The lot shall be divided into a number of convenient portions (not less than ten) such that when equal number of bricks are drawn from each of these portions the number of bricks required for the inspection and testing is provided. 2.

Stacked materials

The number of bricks required for the tests should be sampled from a consignment of not more than 15,000 units for machine-made bricks and 5,000 units for hand-made bricks. The number of bricks required for all the various tests is detailed in Table 2.2. The bricks should be sampled at random so that each brick in the stack or stacks has an equal chance of being chosen, including those bricks within the stacks. This may require the dismantling of part of the stack in order to reach the bricks inside. This will be difficult unless the stacks are small. If possible, an equal sub-sample of not more than 4 bricks should be taken from at least 6 real or imaginary similarly-sized sections of the consignment. 3.

Brick soling

Bricks laid as whole bricks such as in herring bone paving or in shoulder work should be sampled from an area of one square metre marked on the road. All whole bricks within the marked area should be returned to the laboratory as one sample. Several such areas may require to be marked out in order to collect the number of bricks required for the various tests. 4.

Crushed brick

Crushed brick laid as a road pavement layer should be sampled in accordance with 2.2.1.1.3. It is most important that all fine material is removed from the test hole. 2.3.3

Treatment of samples. When the sample is to provide bricks for more than one tests the total number shall be collected together and then divided by taking bricks at random from within the total sample to form each successive sub-sample. Crushed bricks may be riffled or quartered if necessary before transportation, provided that the requirements for minimum test sample weights are met.

2.3.4

Number of bricks required Table 2.3.1 gives a guide as to the number of brick required against the specified test.

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Sampling Table 2.3.1 Number of bricks required for testing Purpose

Number of bricks required for sample

Dimensional checks Soluble salt content Compressive strength Water absorption 2.3.5

24 10 12 10

Sample identification. The following information should be clearly indicated on the sampling certificate by the sampling personnel. a) b) c) d) e) f) g) h) i)

Sampling agent Contract name / work name Client name Where the bricks will be used Supplier of bricks Date of manufacture Type of brick Size of consignment Type of test required.

A sampling certificate is shown as Form 2.3.1.

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Form 2.3.1

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Sampling 2.4

Sampling of Aggregates

2.4.1

Definitions a) Batch. A definite quantity of some commodity manufactured or produced under conditions which are presumed uniform. b) Sampling increment. A quantity of material taken at one time from a larger body of material. When sampling aggregates, the material taken by single operation of a scoop should be treated as a sampling increment. c) Bulk sample. An aggregation of the sampling increments. d) Laboratory sample. A sample intended for laboratory inspection or testing. e) Test portion. The material used as a whole in testing or inspection.

2.4.2

Equipment a) A small scoop, to hold a volume of at least 1 L (about 1.5 kg). This scoop is used for sampling aggregates of nominal sizes less than 5mm. b) A large scoop, to hold a volume of at least 2 L (about 3 kg.). This scoop is used for sampling any grading of aggregate but is required particularly for aggregates of nominal sizes greater than 5mm. c) Containers, clean and non-absorbent for collecting the increments of a sample. d) Containers, clean and impervious for collecting samples for sending to the laboratory. They should be durable and at least 100 micron thick. e) A sample divider, appropriate to the maximum size to be handled. A riffle box is suitable or a flat shovel and a flat metal tray for use in quartering.

2.4.3

Procedure for sampling coarse, fine and all-in aggregate a) Only an experienced person should be allowed to sample. b) Obtain a bulk sample by collecting, in the clean containers, sufficient number of increments to provide the required quantity of aggregate for all the tests to be made. However, the number of increments should be not less than those given in Table 2.4.1. Table 2.4.1 Minimum number of sampling increments Nominal size of aggregate

28 mm and larger 5 mm to 28 mm 5 mm and smaller

Nominal size of sampling increments Large scoop 20 10 10 half scoops

Nominal size of sampling increments Small scoop 10

Approximate minimum mass for normal density aggregate kg. 50 25 10

c) Take increment from different parts of the batch in such a way as to represent the average quality. d) When sampling from heaps of aggregates, take the required number of increments from positions evenly distributed over the whole surface of the heap. e) When sampling from ground level, care should be taken to avoid contamination of the material. f) When sampling form material in motion, calculate the sampling times to give the required number of sampling increments, ensuring that they are randomly distributed throughout the batch of aggregate. g) When sampling from a falling stream of aggregate, take increments from the whole width of the stream. h) When sampling from a conveyor belt, stop the conveyor at appropriate times and take all the material from a fixed length of the conveyor. MAY 2001

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Sampling i) j)

Combine all the increments and either dispatch the bulk sample or reduce it and then dispatch the smaller sample for testing. Never sample manually form a moving conveyor.

2.4.4

Reduction of sample. It is sometimes necessary to reduce the mass of bulk sample at site substantially. This shall be done in such a way to preserve at each stage a representative part of the bulk sample. The reduction of sample should be done in accordance with 2.9.1.1.

2.4.5

Dispatching of samples. The samples should be transferred completely to containers which shall then be sealed for dispatch. Individual packages should preferably not exceed 30 kg. a) Information accompanying the samples. Each sample should contain a card, suitably protected from damage by moisture and abrasion, giving details of the dispatcher and the description of the material. b) Sampling certificate Each sample, or group of samples from a single source, shall be accompanied by a certificate, from the person responsible for taking the sample. The certificate shall include as much as is appropriate of the following information. i.) ii.) iii.) iv.) v.) vi.) vii.) viii.) ix.) x.) xi.) xii.)

Name of testing agent Client name Contractor’s name Contract name Name and location of source Date and time of sampling Method of sampling Identification number Description of sample Tests required Any other information that may be useful to the tester Name and signature of sampler

A sampling certificate is shown as Form 2.4.1.

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Sampling 2.5 2.5.1

Sampling of Cement Introduction. In a general sense of the word, cement can be described as a material with adhesive and cohesive properties which make it capable of bonding mineral fragment into a compact whole mass. The main components of cement are compounds of lime. One of the properties of cements is to be able to set under water by virtue of a chemical reaction with the water. In civil engineering cement is normally confined to calcareous, hydraulic cement. The variability of the proportions of the individual mineral content in the cement renders it to different behaviours in both chemical and physical. Table 2.5.1 lists a number of cements and their designation. Table 2.5.1 Main types of Portland cement General description Ordinary Portland Rapid-hardening Portland Extra rapid-hardening Portland Low heat Portland Modified cement Sulphate-resisting cement White Portland Slag cement

ASTM description Type I Type III Type IV Type II Type V Type S

2.5.2

Scope. This test provides methods for sampling hydraulic cements for testing. The importance of sampling has already been underlined in the introduction.

2.5.3

Equipment. No special equipment is required for sampling cements other than the following: a) Square mouthed shovel; size 2 in accordance with BS 3388. b) Suitable flexible container capable of collecting cement from the nozzle of a pump. c) Other suitable sealable containers. Note. Containers to be used for sampling cement should be watertight and water resistant in order to prevent water ingressing into the sample.

2.5.4

Methods

2.5.4.1

Sampling from concrete batch plant 2.5.4.1a

Bulk cement

a.1 The flexible container is fitted around the discharge nozzle of the silo and cement is allowed to flow into it. a.2 The flexible container is fitted around the discharge nozzle of the cement haulage truck and cement is allowed to flow into it before discharge into the silo. 2.5.4.1b

Bagged cement

Using the random numbers method of sampling decide on the size of a lot and take at random one bag of cement to represent that lot. 2.5.5

Rate of sampling. The rate of sampling is governed by the particular tests required by the specification. Normally the manufacturer delivers cement in batches. One sample is normally taken from each batch.

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Sampling 2.5.6

Test type requirement. For pre-construction approval of cement all tests such as chemical composition, physical properties of: fineness, setting times and compressive strengths are normally required. Upon approval of the cement type, the supplier and manufacturer, cement is procured. The tests required to be carried out to confirm continuous quality during construction are limited due to the length of the tests, however, samples from each batch, for each type of cement, from each supplier from each delivery are taken for routine testing: a) compressive strength b) initial and final setting times c) fineness modulus Other physical tests and chemical tests are normally required once per month from each manufacturer, for each type of cement.

2.5.7

Sampling certificates. A sampling certificate should be issued every time samples of cement are delivered or collected for sampling. The certificate should include at least the following information: a) b) c) d) e) f) g) h) i) j) k)

Name of testing agency Client Manufacturer Client Cement type Location of sample Sample unique identification number Name and signature of sampler Purpose of sampling (test types to be performed) Date of sampling Any other relevant information

2.6

Sampling of Concrete

2.6.1

Scope. The purpose of this test is to provide methods which could be used on site for obtaining from a batch of fresh concrete, representative samples of the quantity required for carrying out the required tests and for making test specimens.

2.6.2

Definitions a) Batch. The quantity of concrete mixed in one cycle of operations of a batch mixer, or the quantity of concrete conveyed ready-mixed in a vehicle, or the quantity of concrete discharged during 1 min. From a continuous mixer. b) Sample. The quantity of concrete, consisting of a number of standard scoopfuls, taken from a batch of concrete. c) Standard scoopful. The quantity of concrete taken by a single operation of the scoop, approximately 5 kg mass of normal weight concrete.

2.6.3

Apparatus a) Scoop, made from minimum 0.8 mm thick non-corrodible metals suitable for taking standard scoopfuls of concrete. b) Container for receiving concrete from a scoop, made of plastic or metal, of 9L minimum capacity. c) Sampling tray, minimum dimensions 900 mm x 900 mm x 50 mm deep, of rigid construction made from a non-absorbent material not readily attacked by cement paste. d) Square mouthed shovel; size 2 in accordance with BS 3388. MAY 2001

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Sampling 2.5.6

Test type requirement. For pre-construction approval of cement all tests such as chemical composition, physical properties of: fineness, setting times and compressive strengths are normally required. Upon approval of the cement type, the supplier and manufacturer, cement is procured. The tests required to be carried out to confirm continuous quality during construction are limited due to the length of the tests, however, samples from each batch, for each type of cement, from each supplier from each delivery are taken for routine testing: a) compressive strength b) initial and final setting times c) fineness modulus Other physical tests and chemical tests are normally required once per month from each manufacturer, for each type of cement.

2.5.7

Sampling certificates. A sampling certificate should be issued every time samples of cement are delivered or collected for sampling. The certificate should include at least the following information: a) b) c) d) e) f) g) h) i) j) k)

Name of testing agency Client Manufacturer Client Cement type Location of sample Sample unique identification number Name and signature of sampler Purpose of sampling (test types to be performed) Date of sampling Any other relevant information

2.6

Sampling of Concrete

2.6.1

Scope. The purpose of this test is to provide methods which could be used on site for obtaining from a batch of fresh concrete, representative samples of the quantity required for carrying out the required tests and for making test specimens.

2.6.2

Definitions a) Batch. The quantity of concrete mixed in one cycle of operations of a batch mixer, or the quantity of concrete conveyed ready-mixed in a vehicle, or the quantity of concrete discharged during 1 min. From a continuous mixer. b) Sample. The quantity of concrete, consisting of a number of standard scoopfuls, taken from a batch of concrete. c) Standard scoopful. The quantity of concrete taken by a single operation of the scoop, approximately 5 kg mass of normal weight concrete.

2.6.3

Apparatus a) Scoop, made from minimum 0.8 mm thick non-corrodible metals suitable for taking standard scoopfuls of concrete. b) Container for receiving concrete from a scoop, made of plastic or metal, of 9L minimum capacity. c) Sampling tray, minimum dimensions 900 mm x 900 mm x 50 mm deep, of rigid construction made from a non-absorbent material not readily attacked by cement paste. d) Square mouthed shovel; size 2 in accordance with BS 3388. MAY 2001

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2.6.4

Sampling procedure. Estimate the number of scoopfuls required for the test(s) by reference to Table 2.6.1. Note. If a shovel is used or other defined apparatus, correlate between the quantity of the scoop and the quantity of the shovel. Note. When sampling from a batch mixer or ready-mixed concrete truck disregard the very first part and the very last part of the discharge. Preferably sample from the middle third of the batch. Note. If the batch to be sampled has been deposited in a heap or heaps of concrete, the parts should whenever possible be distributed through the depth of the concrete as well as over the exposed surface. Table 2.6.1 Quantities of concrete required Test specimen Slump Compacting factor Vebe time Flow index Air content Density 2 cubes 100mm x 100mm 2 cubes 150mm x 150mm 2 beams 100mm x 100 mm x 500mm 2 beams 150mm x 150 mm x 750mm 2 cylinders 150mm x 300mm

2.6.5

number of standard scoopfuls 4 6 4 4 4 6 4 4 6 18 6

Obtaining a sample. Ensure that the equipment is clean. Using the scoop obtain a scoopful of concrete from the central portion of each part of the batch and place it in the container or containers. When sampling from a falling stream pass the scoop through the whole width and thickness of the stream in a single operation. Take the container(s) to the area where the sample is to be prepared for testing or moulding. Sampling from a heap of concrete. Ensure that the shovel is driven into the heap and that concrete is taken to represent the whole mass of the heap by taking a sub-sample from different areas of the heap well spaced over its entire surface area. Combine all sub-samples, agitate and mix well and prepare the sample for testing or moulding.

2.6.6

Protection of samples. At all stages of sampling, transport and handling, the fresh concrete shall be protected against gaining or loosing water and against excessive temperatures.

2.6.7

Certificate of sampling. Each sample shall be accompanied by a certificate of sampling from the person responsible for taking the sample and the certificate shall include at least the following information: a) b) c) d) e) f) g)

Testing agency Client Contract name Location within the structure of concrete Sample identification number Delivery batch note number or any other means of identifying the batch Concrete temperature MAY 2001

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Sampling h) Ambient temperature and weather conditions i) Name of sampler j) Signature of sampler A sampling certificate is shown as Form 2.6.1.

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Sampling 2.7

Sampling of Bitumen Bitumen is normally contained either in metal drums or heated bulk tanks and different methods should be used for sampling each type.

2.7.1

From metal drums the sample must be taken by cutting holes in the side of the drum and removing a sample of bitumen from these holes. Samples should not be taken from the top and bottom of the drum as this may be contaminated during storage and transport.

2.7.2

From a heated bulk tank it is necessary to obtain a sample from the full depth of the tank. This is best done from the top access opening using a purpose-made tube with a closing plug at the bottom, as shown in Figure 2.7.1. The tube is pushed into the full depth of the bitumen, the flap closed and the tube withdrawn. The sample obtained from the tube must be fully mixed before removing a portion for test.

Handle

Cone

Figure 2.7.1

Bitumen Sampling Tube

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Sampling 2.8

Sampling of Bituminous Materials Pre-mixed bituminous materials may be sampled at the asphalt plant or at the site where the material is being laid.

2.8.1

When sampling at the asphalt plant, the whole batch should be discharged into a lorry and then a sample taken from the material in the lorry. This is done in a similar way to sampling from a stockpile with fractions of the sample being taken from at least five different points of the material.

2.8.2

Sampling at the laying site may either be from the paving machine or the laid material. a) When sampling from a paving machine, material should never be taken from the front hopper as segregation often takes place here. Samples should always be taken from the rear screws, a scoop being used to collect material from the ends of the screw. Samples must only be taken when the screws are fully loaded and samples should be taken from both ends. b) When sampling the as laid material, an area to be sampled is marked out and all the material within that area, to the full layer thickness should be removed. Generally it is better to obtain a sample from a number of smaller areas than one big area. On completion of sampling, care must be taken to ensure the areas are repaired to the standard of the original material. Samples of bituminous materials are best transported in a closed tin or small drum. The details of the sample should be recorded, including sample number, date, origin of material, type of material, time of mixing, time of laying, chainage of laid material and weather conditions. It is also necessary to record the temperature after mixing, the temperature at the time of laying and the temperature at the time of rolling.

2.9

Preparing and Transporting Samples

2.9.1

Sample preparation Many samples will require some preparation before being sent to the laboratory for testing, particularly if their large sizes makes them difficult to handle or because they require special protection.

2.9.1.1

Sample reduction. If the sample is delivered larger than required for a particular testing programme, it must be divided to obtain a sample of the required size. In order to ensure the test sample represents the original material, it is necessary to divide the original sample either by quartering or by using a sample divider (Riffle box).

2.9.1.1.1 Quartering. In this method the original sample is placed on a hard clean surface (preferably concrete) and made into a neat circular pile. Using a shovel, this pile is then separated into quarters by making two lines at right angles through the centre of the pile. Two opposite quardrants should then be put aside and the remaining two quadrants should be mixed together to give a smaller sample. If the divided sample is still too large, the procedure should be repeated. Figure 2.9.1 shows the procedure diagrammatically. 2.9.1.1.2 Sample divider. A sample divider, or riffle box, is a purpose-made tool for splitting samples and a riffle box is shown in Figure 2.9.2. The box consists of a number of slots or chutes, alternate ones leading to two separate containers. The total sample is placed into the top hopper and passes down the chutes, half of the sample being collected in each container. The width of the chutes shall be appropriate to the maximum particle

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Sampling 2.8

Sampling of Bituminous Materials Pre-mixed bituminous materials may be sampled at the asphalt plant or at the site where the material is being laid.

2.8.1

When sampling at the asphalt plant, the whole batch should be discharged into a lorry and then a sample taken from the material in the lorry. This is done in a similar way to sampling from a stockpile with fractions of the sample being taken from at least five different points of the material.

2.8.2

Sampling at the laying site may either be from the paving machine or the laid material. a) When sampling from a paving machine, material should never be taken from the front hopper as segregation often takes place here. Samples should always be taken from the rear screws, a scoop being used to collect material from the ends of the screw. Samples must only be taken when the screws are fully loaded and samples should be taken from both ends. b) When sampling the as laid material, an area to be sampled is marked out and all the material within that area, to the full layer thickness should be removed. Generally it is better to obtain a sample from a number of smaller areas than one big area. On completion of sampling, care must be taken to ensure the areas are repaired to the standard of the original material. Samples of bituminous materials are best transported in a closed tin or small drum. The details of the sample should be recorded, including sample number, date, origin of material, type of material, time of mixing, time of laying, chainage of laid material and weather conditions. It is also necessary to record the temperature after mixing, the temperature at the time of laying and the temperature at the time of rolling.

2.9

Preparing and Transporting Samples

2.9.1

Sample preparation Many samples will require some preparation before being sent to the laboratory for testing, particularly if their large sizes makes them difficult to handle or because they require special protection.

2.9.1.1

Sample reduction. If the sample is delivered larger than required for a particular testing programme, it must be divided to obtain a sample of the required size. In order to ensure the test sample represents the original material, it is necessary to divide the original sample either by quartering or by using a sample divider (Riffle box).

2.9.1.1.1 Quartering. In this method the original sample is placed on a hard clean surface (preferably concrete) and made into a neat circular pile. Using a shovel, this pile is then separated into quarters by making two lines at right angles through the centre of the pile. Two opposite quardrants should then be put aside and the remaining two quadrants should be mixed together to give a smaller sample. If the divided sample is still too large, the procedure should be repeated. Figure 2.9.1 shows the procedure diagrammatically. 2.9.1.1.2 Sample divider. A sample divider, or riffle box, is a purpose-made tool for splitting samples and a riffle box is shown in Figure 2.9.2. The box consists of a number of slots or chutes, alternate ones leading to two separate containers. The total sample is placed into the top hopper and passes down the chutes, half of the sample being collected in each container. The width of the chutes shall be appropriate to the maximum particle

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Sampling size of the sample and in general should not be smaller than 1.5 times the maximum particle size of the sample If the sample is still too large, one of the containers may be put aside and the material from the other container is passed through the sample divider again. 2.9.2

Sample transportation All samples should be carefully packed and labeled before transporting them to the laboratory. Sample bags must be strong enough to withstand rough handling and be of a type which prevents loss of fines or moisture from the sample, e.g. thick polythene bags inside jute bags. The use of steel drums for large bulk samples could also be considered. Water samples in glass or plastic containers will require particular care in handling. Undisturbed samples should be placed in wooden boxes and packed in sawdust or similar material to provide added protection. Collision between tubes in transit can easily damage sensitive samples.

2.10

Sample Reception

2.10.1

Registration. Full details of the sample, as written on the label is checked and amended and weighed and must be entered in the laboratory register. A unique number is allocated to the sample and this number is used subsequently on all test sheets for the sample. A copy of the formalised testing programme should accompany the sample through the various stages of testing.

2.10.2

Initial treatment a) Natural moisture content samples should be taken first, as quickly as possible. b) Air drying should be done by leaving the soil spread out in trays or on a hard, clean floor in the laboratory for 2-3 days. c) Oven drying must be done at the correct temperature (110±50C). d) No attempt should be made to quarter down or riffle material which is in lumps or is larger than the size of the riffle-box chutes.

2.10.3

Storage. Storage of all samples should be in an orderly and systematic manner so that they can be subsequently located easily. The storage facility itself should be a secure area, free from the risk of contamination or other harmful influences. Undisturbed samples may be damaged by vibration or corrosion of tubes and should be stored with especial care. Tubes containing wet sandy or silty soils should be stored upright (suitably protected against being knocked over), to prevent possible slumping and segregation of water. The end caps of tube samples which are to be stored for long periods should be sealed with wax, in addition to the wax seal next to the sample itself. Samples which have been tested should not be disposed of without the authority of the laboratory section head.

2.11

Sample Drying Many tests require the material to be drier at the start of the test than the sample as obtained from the field. Some means of drying the sample must, therefore, be utilised. In the case of liquid and plastic limit tests, it is essential that the material is air dried and, as a general rule, it is preferable to dry samples in the air as opposed to drying in

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Sampling size of the sample and in general should not be smaller than 1.5 times the maximum particle size of the sample If the sample is still too large, one of the containers may be put aside and the material from the other container is passed through the sample divider again. 2.9.2

Sample transportation All samples should be carefully packed and labeled before transporting them to the laboratory. Sample bags must be strong enough to withstand rough handling and be of a type which prevents loss of fines or moisture from the sample, e.g. thick polythene bags inside jute bags. The use of steel drums for large bulk samples could also be considered. Water samples in glass or plastic containers will require particular care in handling. Undisturbed samples should be placed in wooden boxes and packed in sawdust or similar material to provide added protection. Collision between tubes in transit can easily damage sensitive samples.

2.10

Sample Reception

2.10.1

Registration. Full details of the sample, as written on the label is checked and amended and weighed and must be entered in the laboratory register. A unique number is allocated to the sample and this number is used subsequently on all test sheets for the sample. A copy of the formalised testing programme should accompany the sample through the various stages of testing.

2.10.2

Initial treatment a) Natural moisture content samples should be taken first, as quickly as possible. b) Air drying should be done by leaving the soil spread out in trays or on a hard, clean floor in the laboratory for 2-3 days. c) Oven drying must be done at the correct temperature (110±50C). d) No attempt should be made to quarter down or riffle material which is in lumps or is larger than the size of the riffle-box chutes.

2.10.3

Storage. Storage of all samples should be in an orderly and systematic manner so that they can be subsequently located easily. The storage facility itself should be a secure area, free from the risk of contamination or other harmful influences. Undisturbed samples may be damaged by vibration or corrosion of tubes and should be stored with especial care. Tubes containing wet sandy or silty soils should be stored upright (suitably protected against being knocked over), to prevent possible slumping and segregation of water. The end caps of tube samples which are to be stored for long periods should be sealed with wax, in addition to the wax seal next to the sample itself. Samples which have been tested should not be disposed of without the authority of the laboratory section head.

2.11

Sample Drying Many tests require the material to be drier at the start of the test than the sample as obtained from the field. Some means of drying the sample must, therefore, be utilised. In the case of liquid and plastic limit tests, it is essential that the material is air dried and, as a general rule, it is preferable to dry samples in the air as opposed to drying in

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Sampling an oven or by other artificial means. The frequent need to dry samples quickly is more often a sign of bad planning than of an efficient laboratory. 2.11.1

Air drying. This is essential for liquid and plastic limit tests and is the preferred procedure for all other tests. The sample should be spread out in a thin layer on a hard clean floor or on a suitable metal sheet. Ordinary corrugated galvanised roofing sheets are perfectly satisfactory for this purpose. The material should be exposed to the sunlight and should be in a layer not more than 20 mm thick. Cohesive materials such as clays, require breaking by hand or with a rubber mallet into small pieces, to allow drying to take place without too much delay. The soil should periodically be turned over and a careful check should be made to ensure the material is removed to a sheltered place if it starts to rain. In the case of soft stone or gravels, care should be taken to ensure only lumps of cohesive fines are broken up and that the actual stone particles are not destroyed. In the case of fine-grained materials, it is generally beneficial to the later stages of testing to pass the dried particles through a No. 4 sieve. Air drying should not normally take longer than 2 to 3 days if carried out correctly.

2.11.2

Oven drying. Oven drying should only be employed where air drying is not possible. Oven drying will not normally have any detrimental effect on the results for sound granular materials such as sand and gravel, but may change the structure of clay soils and thus lead to incorrect test results. Oven drying must never be used in the case of liquid and plastic limit tests. In oven drying the temperature should not exceed 1100C and the material should be dried as quickly as possible by spreading in thin layers on metal trays. Periodically, the material should be allowed to cool before testing is commenced.

2.11.3

Sand-bath drying. In certain cases an oven may not be available but the sample must be dried quickly; sand bath drying may then be utilised. The sand-bath consists simply of a strong metal tray or dish which is filled with clean coarse sand. The sand bath is placed on some form of heater such as a kerosene stove, a gas ring or an electric ring. The sample to be dried is placed in a heatproof dish which is embedded in the surface of the sand. A low heat should be applied so that the sand becomes heated without causing damage to the bath. The sample should be stirred and turned frequently to ensure the material at the base does not become too hot. The material should be allowed to cool before testing is commenced.

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CHAPTER 3 CLASSIFICATION TESTS

3.1

Determination of Moisture Content

3.1.1

General requirements

3.1.1.1

Scope. Water is present in most naturally occurring soils and has a profound effect in soil behaviour. A knowledge of the moisture content is used as a guide to the classification. It is also used as a subsidiary to almost all other field and laboratory tests of soil. The oven-drying method is the definitive method of measuring the moisture contents of soils. The sand-bath method is used, where oven drying is not possible, mainly on site.

3.1.1.2

Definition. The moisture content of a soil sample is defined as the mass of water in the sample expressed as a percentage of the dry mass, usually heating at 1050C, i.e. moisture content, w = M W

x 100 (%)

MD where,

M W = mass of water M D = dry mass of sample

3.1.1.3

Sample requirements

3.1.1.3.1 Sample mass. The mass required for the test depends on the grading of the soil, as follows; a) Fine-grained soils*, not less than 30 grams b) Medium-grained soils*, not less than 300 grams c) Coarse-grained soils*, not less than 3 kg *Soils group i) Fine-grained soils: Soils containing not more than 10% retained on a 2 mm test sieve. ii) Medium-grained soils: Soils containing more than 10% retained on a 2 mm test sieve but not more than 10% retained on a 20 mm test sieve. iii) Coarse-grained soils: Soils containing more than 10% retained on a 20 mm test sieve but not more than 10% retained on a 37.5 mm test sieve. 3.1.1.4

Accuracy of weighing. The accuracy of weighing required for test samples is as follows; a) Fine-grained soils: within 0.01 g. b) Medium-grained soils: within 0.1 g. c) Coarse-grained soils: within 1g.

3.1.1.5

Safety aspects a) Heat-resistant gloves and / or suitable tongs should be used to avoid personal injury and possible damage to samples. MAY 2001

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b) If glass weighing bottles are used they should be placed on a high shelf away from heating elements. c) A heat-insulated pad should always be used to place hot glassware of any description. 3.1.2

Oven-drying method (standard method)

3.1.2.1

Apparatus 1) Thermostatically controlled drying oven capable of operating to 105±50C. 2) Glass weighing bottles or suitable metal containers (corrosion-resistant tins or trays). 3) Balance (to the required sensitivity). 4) Dessicator containing anhydrous silica gel. 5) Scoop, other small tools as appropriate. Optional: Test sieves - 2 mm, 20 mm, 37.5 mm (to check classification of sample, in order to confirm required sample size).

3.1.2.2

Test procedure a) One clean container with the lid (if fitted) is taken and the mass in grams is recorded (m1) together with container number. Note:

The container plus lid or bottle plus stopper should have the same number and be used together.

b) The sample of wet soil is crumbled and placed in the container. The container with the lid on is weighed in grams (m2). c) The lid is removed and both lid and container are placed in the oven. The sample is then dried in a thermostatically controlled drying oven which is maintained at a temperature of 105±50C. A period of 16 to 24 hours is usually sufficient, but this varies with soil type. It will also vary if the oven contains a large number of samples or very wet samples. The soil is considered dry when the differences in successive weighings of the cooled soil at 4 hour intervals do not exceed 0.1% of the original mass. Note. 1) For peats and soils containing organic matter a drying temperature of 600C is to be preferred to prevent oxidation of organic matter. 2) For soils containing gypsum a maximum drying temperature of 80 0C is preferred. The presence of gypsum can be confirmed by heating a small quantity of soil on a metal plate. Grains of gypsum will turn white within a few minutes, but most other mineral grains will remain unaltered. d) The container is removed from the oven. For medium and coarse-grained soils, the lid should be replaced (if fitted) and the sample allowed to cool. For fine-grained soils, the container and lid, or bottle and stopper if used, should preferably be placed in a dessicator and allowed to cool. After cooling, the lids or stoppers should be replaced and the container plus dry soil weighed in grams (m3). 3.1.2.3

Calculation and expression of results Moisture content, w =

=

mass of moisture x 100% mass of dry soil

( mass of container + wet soil) - (mass of container + dry soil) x 100% (mass of container + dry soil) - (mass of container) MAY 2001

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w=

i.e.

m2 − m 3 x 100% m3 − m1

For values up to 10% the moisture content should be expressed to two significant figures, e.g. 1.9%, 4.3%, 9.8%. For moisture contents above 10% express the result to the nearest whole number, e.g. 11%, 27%. Note. If the moisture content is to be related to the Atterberg limits, e.g. for determining the liquidity index, and the soil contains material retained on a 425 µm sieve, the measured moisture content, w (in %), can be corrected to give the equivalent moisture content, wa (in %), of the fraction passing the 425 µm sieve, using the equation :

 100  wa = w   pa  where,

pa is the percentage by dry mass of the portion of the soil sample passing the 425 µm test sieve.

If the particles retained on the 425 µm sieve are porous and absorb water, the amount of absorption should be determined and the value of water calculated from the equation.

wa =

 100 − p a  100 w − wr  pa  pa 

where; wr, is the moisture content of the fraction retained on the 425 µm test sieve. 3.1.2.4

Report. The test report shall contain the following information: a) b) c) d) e)

the method of test used; the moisture content; the temperature at which the soil was dried, if less than 105 0C; the comparison with Atterberg limits, if required (see Note to 3.1.2.3); full details of the sample origin.

The operator should sign and date test sheet. An example of the calculations made is shown in Form 3.1.1. 3.1.3

Sand-bath (subsidiary method)

3.1.3.1

Apparatus i)

Strong metal heatproof tray or dish containing clean sand to a depth of at least 25mm (sand-bath). ii) Moisture content containers for fine soils (excluding glass containers), as used for oven drying. For coarser soils heat-resistant trays 200-250 mm square and 50-70 mm deep, the size depending on the quantity of soil required for test. iii) Heating equipment, such as a bottled gas burner or paraffin pressure stove, or electric hot plate if mains electricity is available. iv) Scoop, spatula, appropriate small tools.

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Standard Test Procedures

Test procedure a) A clean dry container with the lid (if fitted) is weighed, in grams (m1). The number of the container is recorded. b) The sample of wet soil is crumbled, placed in the container and weighed in grams (m2). c) The sand-bath is placed on some form of heater such as a kerosene stove, a gas burner or an electric heater. The sample in its container is embedded in the surface of the sand in the sand-bath. Care should be taken to ensure that the container is not heated too much. The sample should be stirred and turned frequently so that the sample does not burn. Small pieces of white paper will act as an indicator and turn brown if over-heated. To check that the sample is completely dry it should be weighed and returned to the sand-bath for another 15 minutes. If the loss in mass after heating for a further period of 15 min does not exceed the following, the sample may be considered to be dry : Fine-grained soils Medium-grained soils Coarse-grained soils

0.1g 0.5g 5g

d) After drying, the sample is removed from the sand-bath, the container lid (if fitted) is firmly secured in place and the sample is allowed to cool. When cool, the container and the dry soil is weighed in grams (m3). Note. Do not place hot trays onto the unprotected pan of a balance. e) Normally, more than one determination of moisture content is made and the average value is taken. 3.1.3.3

Calculation and expression of results. Calculation and expression of results are identical to those for oven-drying method.

3.1.3.4

Report. Report is also identical to that for oven-drying method.

3.1.4

Speedy Moisture Test

3.1.4.1

General

3.1.4.1.1 Introduction. A rapid test method for determination of moisture in soils is by the use of a calcium carbide gas pressure moisture tester - commonly called the Speedy moisture tester. Soil samples are used in 6, 26 and 200 gram sizes. 3.1.4.1.2 Apparatus. The basic apparatus includes the moisture tester, a scale for weighing the sample, a cleaning brush, a scoop for measuring the calcium carbide reagent and a sturdy carrying case. For the 26 gm sample test, steel balls are used to break down cohesive materials. Calcium carbide reagent is available in cans. This may be a finely pulverized material and should be of a grade capable of producing at least 2.25 cu.ft. of acetylene gas per pound of calcium carbide. In performing the test, in the 26 gram sample unit, three scoops of reagent (approximately 24 grams) and two balls are placed in the large chamber of the tester. When using the 6 gram sample tester, place on level scoopful (approximately 8 grams) of calcium carbide in the larger chamber of the tester. Steel balls are not used with the 6 gm sample tester. MAY 2001

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Speed moisture tester is shown in Figure 3.1.1. 3.1.4.1.3 Preparation of the material. The speedy moisture test gives consistently accurate results in approximately 3 minutes. The material should be prepared for test as follows: a) Sands and fine powders : No preparation necessary. b) Clays, soils and other coarse materials: Use steel ball speedy moisture test. c) Aggregates: No preparation necessary. 3.1.4.1.4 Pre-caution. Five rules should be noted before testing. Make sure that: a) The body or cap, whichever is being used for the material, is perfectly clean and contains no active absorbent from a previous test. b) The material is truly representative of the bulk and carefully weighed. c) The material and the absorbent are kept separate until the cap is tightly secured to the body. d) The material has been thoroughly prepared – ground or pulverized or mixed with sand (if necessary) so that the absorbent can act freely on the material. e) Make sure that the steel ball pulverizes are used when testing clays, soils etc. 3.1.4.2

Procedure a) Weight the desired 6, 26, or 200 gram test sample on the scale. b) Place the soil sample in the cap of the tester. Then, with the pressure vessel in approximately horizontal position, insert the cap in the pressure vessel and seal the unit by tightening the clamp, taking care that no calcium carbide comes in contact with the soil sample until a seal is achieved. c) Raise the moisture tester to a vertical position so that the soil in the cap falls into the pressure vessel. d) Then shake the tester vigorously so that all the lumps will be broken up, permitting the calcium carbide to react with all the available free moisture. When steel balls are used in the tester, the instrument should be shaken with a rotating motion. This will prevent damage to the instrument and eliminate the possibility of soil particles becoming embedded in the orifice leading to the pressure diaphragm. e) Continue shaking for approximately one minute for granular soils and up to three minutes for other soils, to allow for complete reaction between the calcium carbide reagent and free moisture. Time should be permitted to allow dissipation of the heat generated by the chemical reaction. f) When the dial indicator stops moving, read the dial while holding the instrument in a horizontal position at eye level. g) Record the sample weight and the dial reading. h) With the cap of the instrument pointed away from the operator, slowly release the gas pressure. Empty the pressure vessel and examine the material for lumps. If the sample is not completely pulverized, the test should be repeated using a new sample. i) The dial reading is the percent of moisture by wet weight and must be converted to dry weight percent.

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Clamping screw Small weight Helicol

Small brush

Stirrup

Measuring scoop

Cap Large wire handled brush

Rubber cap gasket

Bushing to hold

Stirrup side screw

Adapter nut and filter

Nylon washer

Rubber gauge gasket Standard tester body

Gauges

Figure 3.1.1

a) Speedy moisture tester

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Knife-edge(square shape)

Scale pan

Knife edge (pear shape) Scale link

Scale cradle Agates

Platform base

Figure 3.1.1

b) Speedy moisture tester

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Standard Test Procedures

Expression of results and report Moisture content should be expressed to two significant figures, e.g. 1.9%, 4.3%. Wet weight / dry weight conversion Chart (when steel ball pulverizes are not used) is presented in Table 3.1.1 and the conversion chart (when using steel ball pulverizes) is shown in Figure 3.1.2. The test report shall contain the following information: a) Method of test used, b) The moisture content c) Full details of the sample origin. Table 3.1.1

Wet Weight / Dry Weight Conversion Chart Not Applicable When Steel Ball Pulverizes Used – See Figure 3.1.2 With Calibration Curves on Reverse Side SPEEDY READING Wet Weight Dry Weight 1.0% 1.0% 2.0% 2.1% 3.0% 3.2% 4.0% 4.3% 5.0% 5.4% 6.0% 6.5% 7.0% 7.6% 8.0% 8.7% 9.0% 9.8% 10.0% 11.0% 10.5% 11.7% 11.0% 12.3% 11.5% 13.0% 12.0% 13.6% 12.5% 14.2% 13.0% 14.9% 13.5% 15.6% 14.0% 16.3% 14.5% 16.9% 15.0% 17.6% 15.5% 18.3% 16.0% 19.0% 16.5% 19.7% 17.0% 20.4% 17.5% 21.2% 18.0% 21.9% 18.5% 22.7% 19.0% 23.4% 19.5% 24.2% 20.0% 25.0%

SPEEDY READING Wet Weight Dry Weight 20.5% 25.8% 21.0% 26.5% 21.5% 27.4% 22.0% 28.2% 22.5% 29.0% 23.0% 29.8% 23.5% 30.7% 24.0% 31.5% 24.5% 32.4% 25.0% 33.3% 25.5% 34.2% 26.0% 35.3% 26.5% 36.0% 27.0% 36.9% 27.5% 37.9% 28.0% 38.8% 28.5% 39.8% 29.0% 40.8% 29.5% 41.8% 30.0% 42.8% 30.5% 43.9% 31.0% 44.9% 31.5% 45.9% 32.0% 47.0% 32.5% 48.1% 33.0% 49.2% 33.5% 50.3% 34.0% 51.5% 34.5% 52.6% 35.0% 53.8%

MAY 2001

SPEEDY READING Wet Weight Dry Weight 35.5% 55.0% 36.0% 56.2% 36.5% 57.4% 37.0% 58.7% 37.5% 60.0% 38.0% 61.2% 38.5% 62.6% 39.0% 63.9% 39.5% 65.2% 40.0% 66.6% 40.5% 68.0% 41.0% 69.4% 41.5% 70.9% 42.0% 72.4% 42.5% 73.8% 43.0% 75.4% 43.5% 76.9% 44.0% 78.5% 44.5% 80.1% 45.0% 81.8% 45.5% 83.4% 46.0% 85.1% 46.5% 86.9% 47.0% 88.6% 47.5% 90.6% 48.0% 92.3% 48.5% 94.1% 49.0% 96.0% 49.5% 98.0% 50.0% 100.0%

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3.2

Determination of Atterberg Limits

3.2.1

Scope. As the moisture content of a soil decreases the soil passes from the liquid state to the plastic state to the solid state. The range of moisture contents over which the soil is plastic is used as a measure of the plasticity index. The points at which a soil changes from one state to another are arbitrarily defined by simple tests called the liquid limit test and plastic limit test. These tests are known as the Atterberg limits. The Atterberg limits are empirical tests which are used to indicate the plasticity of fine grained soil by the differentiation between highly plastic, moderately plastic and nonplastic soils. The tests enable classification and identification of the soil to be carried out and give a rough guide to the engineering properties.

3.2.2

Sample preparation. It is preferable not to dry the soil before preparation for the test. Two preferred methods of preparation are described, depending on whether the soil contains a significant proportion of particles larger than the 425 µm sieve.

3.2.2.1

Method for fine soils. If the soils contains few or no particles retained on a 425 µm sieve, take a representative sample weighing about 500 g, chop it up and mix thoroughly for at least 10 minutes with distilled water to form a thick homogeneous paste. Seal in an airtight container (e.g. a corrosion-resistant tin or a polythene bag) for 24 hours before testing. Mixing should be carried out on a glass plate with two palette knives. The required 24 hour maturing period may be shortened for soils with low clay contents. If only a few particles larger than 425 µm are present, these can be removed by fingers or with tweezers during mixing. If coarse particles are present determine their mass and the mass of the sample used. These weighings enable the approximate proportion of coarse material to be reported if required.

3.2.2.2

Wet preparation method. This is the preferred method for soil containing coarse particles, and should be used for all such soils that are sensitive to the effects of drying. Procedure 1. Take a representative specimen that will give at least 350 g passing a 425 µm sieve, and weigh it (m grams). This quantity should be sufficient for a liquid limit and a plastic limit test. Weighings should be carried out to an accuracy of within 0.01 g. 2. Take another representative sample for determination of moisture content (w %). Calculate and record the mass of dry soil in the test sample (mD ) from the equation:

mD =

100m 100 + w

3. Cut up the weighed sample in a beaker and just cover with distilled water. Stir to form a slurry. Do not use a dispersant. 4. Pour the slurry through a 2 mm sieve nested on a 425 µm sieve. Use the minimum amount of distilled water to wash clean the particles retained on both sieves. Continue until the water passing the 425 µm sieve is virtually clear. Collect all the washings. 5. Dry (at 1050C to 1100C) and weigh the retained material (mR grams) to an accuracy of within 0.01 g. 6. Allow the collected wash water to stand undisturbed, and pour or siphon off any clear water. A settling time of several hours may be required. It is important no to lose any soil particles during the siphoning procedure (see Note).

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7. Allow the suspension to partially dry in warm air, or in an oven at not more than 500C, or by filtration under vacuum or pressure, until it forms a stiff paste. But prevent local drying at the surface or edges, by repeated stirring. Note 1.

A suitable consistency for the paste corresponds to not less than 50 blows of the Casagrande apparatus.

Note 2.

When using this method, care should be taken with samples containing soluble salts. These samples should be allowed to dry by evaporation only, and not by siphoning or pouring off excess water.

3.2.2.3

Dry preparation method. If the use of a dry preparation method is unavoidable then the procedure should be followed as shown schematically in Figure 3.2.1.

3.2.3

Liquid limit test (Casagrande method) 1.

Apparatus a) b) c) d) e)

2.

Equipment for the determination of moisture content (weighing to 0.01 g). Soil mixing equipment (glass plate, spatulas, distilled water). Timer clock. Casagrande liquid limit device (Figure 3.2.2). Grooving tool and height gauge (Figure 3.2.3).

Calibration of apparatus The height of the underneath of the cup when fully lifted should be such that the 10 mm gauge will just pass between it and the base. Some grooving tools incorporate a block of the correct thickness. The locking nuts must be adjusted to maintain the correct height of drop. The device should be checked to make sure that the cup falls freely, that there is no side play in the cup, that the screws are tight, that the cup and base are not worn and that the blow counter works correctly and is set to zero. Details of the liquid limit device and how the cup fall is set are shown in Figure 3.2.4. The dimensions of the grooving tool are important and a reference (unused) tool should be available to check the tool being used against. When the tip of the tool being used becomes worn to a width of 3 mm it should be re-ground to the correct dimensions.

3.

Test Procedure a) Mix about 300 g of the prepared soil (after 24 hours maturing) with a little distilled water if necessary, using two spatulas, for at least 10 minutes. At this point the first blow count should be about 50 blows. If a plastic limit test is required it is convenient to set aside a portion of soil for this purpose. b) With the cup resting on the base, press soil into the cup being careful to avoid trapping air. Form a smooth level surface parallel to the base giving a maximum thickness of 10 mm (see Figure 3.2.5). c) Beginning at the hinge, and with the chamfered edge of the tool facing the direction of movement, make a smooth groove with a firm stroke of the grooving tool, dividing the sample into two equal parts. The tip of the grooving tool should lightly scrape the inside of the bowl, but do not press hard.

When using the tool, apply a circular motion so that it is always normal to the surface of the cup (see Figure 3.2.5).

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locking screw

locknut

pivot adjusting screw cam follower 10 mm

cup

direction or rotation

base handle a)

b)

Figure 3.2.4

a) The parts of the Casagrande device. b) The fully raised cup set to the specified height.

position of grooving tool

level surface

2

3

when cutting

thickness 10 mm

Figure 3.2.5

1

a) Soil placed in Casagrande bow

b) Use of the grooving tool

d) Rotate the handle at a speed of two turns per second – check with a seconds timer. Stop turning when the bottom of the groove closes along a continuous length of 13 mm (use the back of the grooving tool as a gauge). Record the number of blows. e) Add a little more soil from the mixture on the glass plate to the cup and mix in the cup. Repeat stages (b) to (d) stated above until two consecutive runs give the same number of blows for closer. Record the number of blows. f) Remove a portion of about 10 g of the soil adjacent to the closed gap with a clean spatula, transfer to a weighed container and fit the lid immediately. Record the container number and determine the moisture content. g) Repeat steps (b) to (f) stated above after adding increments of distilled water, mixing the water well in. At least two determinations should give more than 25 blows, and two less than 25, in the range of about 10 to 50 blows. Do not add dry soil to the soil paste. Protect the soil on the glass plate from drying out at all times. Each time the soil is removed from the cup for the addition of water, wash and dry the cup and grooving tool.

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4.

Standard Test Procedures

Calculation and Expression of Results After determining the moisture contents plot each moisture content against the number of blows on the printed test sheet. A line of best fit is drawn through the plotted points. This is called the ‘flow curve’. The liquid limit is defined as the percentage moisture content that corresponds to 25 blows as determined from where the ordinate at 25 blows intersects the flow curve. Record this value of moisture content to the nearest 0.1%. An example is given on the attached test sheet (see Form 3.2.1)

5.

Report The full report will include the sample details, method of preparation of the sample and the percentage passing the 425 µm sieve. The operator should sign and date the test form.

3.2.4

Plastic limit test 1.

Apparatus a) b) c) d)

2.

Equipment for the determination of moisture content (weighing to 0.01 g). Soil mixing equipment (glass plate, spatulas, distilled water). Smooth glass plate free from scratches, for rolling threads on. A length of rod, 3 mm in diameter and about 100 mm long.

Test Procedure a) Prepare and mature the test sample using wet or dry preparation method or take the sample previously set aside from the liquid limit test. b) Take about 20 g of the soil and allow it to lose moisture until it is plastic enough to be shaped into a ball without sticking to the fingers. Mould into a ball between the fingers and roll between the palms of the hands until slight cracks appear on the surface. Moulding and kneading is necessary throughout the test to preserve a uniform distribution of moisture and to prevent excessive drying of the surface only. c) Divide the sample into two roughly equal portions and carry out a separate test on each portion. d) Divide the first portion into four pieces. Mould one piece into a cylinder about 6 mm diameter between the first finger and thumb. e) Roll the cylinder under the fingers of one hand on a smooth glass surface, applying enough pressure to reduce the diameter to about 3 mm in about 5 to 10 complete forward and backward movements. Maintain a uniform pressure. Do not reduce pressure as the 3 mm diameter is approached. Use a metal rod of 3 mm diameter to judge the thread diameter. f) Pick up the soil thread, mould further and repeat the above. Repeat until the thread shears both longitudinally and transversely at a diameter of 3mm. Crumbling may consist of one of the forms shown in Figure 3.2.6 depending on the nature of the soil. g) Crumbling can usually be felt by the fingers. The crumbling condition must be achieved, even if greater than 3 mm diameter. If smooth threads of 3 mm diameter (like noodles) are formed, the soil is not dry enough, as illustrated in Figure 3.2.5. The first crumbling point is the plastic limit, do not attempt to continue reforming and rolling beyond this point.

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i) ii) iii) iv)

v)

Standard Test Procedures

Shearing and cracking both longitudinally and transversely. Falling apart in small pieces. Forming an outside tubular layer which splits at both ends. Breaking into barrel-shaped pieces. Heavy clay requires considerable pressure to reduce the diameter to 3 mm. No crumbling – soil too wet (like noodles).

Figure 3.2.6

3 mm

Some forms of crumbling in the plastic limit test

h) Gather the crumbled soil quickly, place in a small weighed container, and fit the lid immediately. Repeat the above process on second, third and fourth pieces of soil and place all fragments in the same container. Weigh it as soon as possible. i) Carry out the same operations on four pieces from the second portion, placing the fragments in a second container, and weigh. 3.

Calculation and Expression of Results Dry the specimens at 1050C – 1100C, weigh and calculate the moisture contents to the nearest 0.1%. If the two values differ by more than 0.5% moisture content repeat the whole test on another portion of soil. Otherwise, the average of the two values is the plastic limit. If it is not possible to determine the plastic limit this fact should be reported.

4.

Report The plastic limit is reported to the nearest whole number. The test sheet must be completed in full to give sample details, method of preparation and the percentage of material passing the 425 µm sieve. The test sheet should be signed and dated by the test operator. An example of a completed test sheet is attached (Form 3.2.1).

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3.2.5

Standard Test Procedures

Determination of the plasticity index 1.

Procedure The Procedure is a simple calculation and requires the determination of the liquid and plastic limits for the soil. The Casagrande method is to be used to determine the liquid limit. The plasticity index of a soil is the numerical difference between the liquid limit and the plastic limit: PI = LL – PL

2.

Report The plasticity index is reported to the nearest whole number. If both the liquid and plastic limits cannot be determined the soil is described as non-plastic (NP). Two special cases may be found. If it is possible to determine the liquid limit but not the plastic limit, the soil is reported as non-plastic. If the plastic limit is found to be equal to or greater than the liquid limit (as with some highly micaceous soils), the sample is also reported as non-plastic.

Determination of linear shrinkage 1.

Apparatus a) A drying oven capable of operating at 600C – 650C and 1050C – 1100C. b) Soil mixing equipment (glass plate, spatulas, distilled water). c) Vernier calipers measuring up to 150 mm and reading to 0.1 mm. Alternatively, a steel rule graduated to 0.5 mm. d) Silicone grease or petroleum jelly. e) Evaporating dish (approx. 150 mm ∅). f) Moulds made of brass or other non-corrodible material. They shall be semicircular in cross section with an internal radius of 12.5 ± 0.5 mm and 140 mm long, with square end pieces attached as supports which also serve to confine the soil (see Figure 3.2.7).

20

3 40

3.2.6

R=12.5± 0.5

140± 1.0 6 All dimensions are in millimetres.

Figure 3.2.7 2.

Mould for linear shrinkage test

Test Procedure a) Preparation of apparatus. Clean the mould thoroughly and apply a thin film of silicone grease or petroleum jelly to its inner faces to prevent the soil adhering to the mould.

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b) Prepare and mature the test sample using wet or dry preparation method. Place a sample of about 150 g on the flat glass plate or in the evaporating dish. c) Add distilled water if necessary and mix thoroughly using the palette knives until the mass becomes a smooth homogeneous paste with a moisture content at about the liquid limit of the soil. Note. The required consistency will require about 25 bumps of the Casagrande apparatus. This moisture content is not critical to within a few percent. d) Place the soil / water mixture in the mould such that it is slightly proud of sides of the mould. Gently jar the mould to any air pockets in the mixture. e) Level the soil along the top of the mould with the palette knife and remove all soil adhering to the rim of the mould by wiping with a damp cloth. f) Place the mould where the soil / water can air-dry slowly in a position free from draughts until the soil has shrunk away from the walls of the mould. Then complete the drying, first at a temperature not exceeding 65 0C until shrinkage has largely ceased, and then at 1050C to 1100C to complete the drying. g) Cool the mould and soil and measure the mean length of the soil bar. If the specimen has become curved during drying, remove it carefully from the mould and measure the lengths of the top and bottom surfaces. The mean of these two lengths shall be taken as the length of the oven dry specimen. Note. Should a specimen crack badly, or break, such that measurement is difficult, the test should be repeated at a slower drying rate. 3.

Calculation and expression of results Calculate the linear shrinkage of the soil as a percentage of the original length of the specimen, LO (in mm), from the equation:



Percentage of linear shrinkage =  1 -



LD   100 LO 

Where, L D is the length of the oven-dry specimen (in mm). 4.

Report The linear shrinkage is reported to the nearest whole percentage. The test sheet (see Form 3.2.2) must be completed in full to give sample details, method of preparation and the percentage of material passing the 425 µm sieve. The test sheet should be signed and dated by the test operator. An example of the calculation is shown in Form 3.2.2.

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3.3

Particle Size Distribution

3.3.1

Introduction. The determination of the particle size distribution of soil is an important part of classification. The particle size distribution of a granular material such as road base or a concrete aggregate, is an essential guide to the stability of the material for use in the works, as the engineering properties of the material are strongly dependent upon the grading. In the case of fine grained cohesive soils which contain only a small percentage of sand and silt, it is not generally necessary to carry out a particle size distribution, as the Atterberg limits will provide sufficient guide to the properties of the soil. Particle size distribution can be done by dry sieving or wet sieving. Wet sieving may be used on any material and is more accurate than dry sieving but takes slightly longer to perform.

3.3.2

General requirements

3.3.2.1

Sample mass. Mass of soil sample required for sieving is shown in the Table 3.3.1. Table 3.3.1 Mass of soil sample for sieving Maximum size of material present in substantial proportion (more than 10%) Test sieve aperture mm 63 50 37.5 28 20 14 10 6.3 5 3.35 2 or smaller

3.3.2.2

kg 50 35 15 6 2 1 0.5 0.2 0.2 0.15 0.1

Accuracy of weighing. The accuracy of weighing required depends on the size of the sample or sub-sample and the following values should be used.

Fine grained soils Medium grained soils Coarse grained soils 3.3.2.3

Minimum mass of sample to be taken for sieving

Minimum accuracy of weighing 0.1 gms 1 gms 10 gms

System of sieve sizes. Different systems of sieves are used at present time. Anyone of these sieve systems may be used in the test, provided all sieves in one set are of the same system. Slight differences in aperture (mesh) sizes can easily be accounted for when the results are plotted on a logarithmic grading chart. Sieves designation and their sizes are shown in the Table 3.3.2.

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Table 3.3.2 Sieves designation and their sizes BS sieve aperture size

Sieves to ASTM D422 Nearest designation Aperture size 75 mm 3 inch 75 mm 63 21/2 inch 63.5 50 2 inch 50.8 37.5 11/2 inch 38.1 28 1 inch 25.4 3 20 /4 inch 19.05 14 3 10 /8 inch 9.52 6.3 5 No. 4 4.75 3.35 No. 6 3.35 No. 8 2.36 2 No. 10 2.00 1.18 No. 16 1.18 No. 20 850 µm No. 30 600 µm 600 No. 40 425 425 No. 50 300 300 No. 60 250 No. 70 212 212 No. 100 150 150 No. 140 106 No. 200 75 75 No. 230 63 63 * Sieves marked with * have been proposed as an International (ISO) Standard. It is recommended to include, if possible, these sieves in all sieve analysis data or reports. 3.3.2.4

Care and use of sieves a) If too much material is placed on a sieve at any one time, some of the fine material will not reach the mesh and will be retained on the sieve, thus giving errors. It is therefore important to ensure the sieves are never overloaded. Table 3.3.3 gives the maximum mass of material to be retained on each sieve at the completion of sieving.

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Table 3.3.3 Maximum mass of material to be retained on each sieve at the Completion of sieving Test sieve Aperture size

Maximum mass on sieve of diameter

mm 50 37.5 28 20 14 10 6.3 5 3.35 2 1.18 µm 600 425 300 212 150 75

(3/8 in) (1/4 in) (4) (6) (10) (16)

450 mm kg 10 8 6 4 3 2 1.5 1.0 -

300 mm kg 4.5 3.5 2.5 2.0 1.5 1.0 0.75 0.5 -

200 mm g 1000* 500* 350* 300 200 100

(30) (40) (50) (70) (100) (200)

-

-

75 75 50 50 40 30

(2 in) (11/2 in) (3/4 in)

Note 1. Numbers in brackets indicate equivalent ASTM sieve sizes or numbers. Note 2. *It may be more appropriate to use a larger diameter sieve for material of this size, depending on the size of the fraction in the sample. 1 mm = 1000 microns (1000 µm) b) The fine sieves must not be overloaded, because this not only leads to inaccuracy but also reduces the life of the sieve. c) It is very difficult to prevent overloading, when using mechanical sieve shakers and mechanical sieve shakers are not recommended except for coarse grained materials. d) Particles larger than 20 mm may be placed through the sieve by hand, but must not be forced through. All smaller sizes must be shaken through the sieves. e) The sieves must be kept clean by brushing with a brass or camel hair brush and washing through all sieving. Fine sieves should be inspected for holes in the mesh before use. Care in the use of sieves and prevention of overloading will lead to longer lives. 3.3.3

Wet sieving method

3.3.3.1

Scope. When a perceptible amount of clay or silt or if fine particles are found connected with the larger particles, then wet sieving must always be used.

3.3.3.2

Apparatus. (1)

A typical range of aperture or mesh sizes would be : 75 mm, 63 mm, 50 mm, 37.5 mm, 28 mm, 20 mm, 14 mm, 10 mm, 6.3 mm, 5 mm, 3.35 mm, 2 mm, 1.18 mm, 600 ± = µm, 425 µm, 300 µm, 212 µm, 150 µm, 75 µm. Lids and receives of appropriate size are required.

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Notes a) The aperture sizes to be used will vary from sample to sample. Only the necessary aperture sizes should be used, except that, for convenience or to prevent overloading, additional sieves may be used so that the requirements of Table 3.3.3 are complied with. b) The defining size separating fine sand and silt grades is 60 µm. The aperture size normally found closest to this is 63 µm. However, in practice the 75 µm sieve is more commonly used because it is more robust and less time-consuming to use. This standard suggests the continued use of the 75 µm sieve as the washing sieve. Some manufacturers’ offer a special ‘washing’ sieve which is of 200 mm diameter and 200 mm deep with a 75 µm mesh. c) It can be useful to have two sets of sieves, one for the wet sieving and one for the dry sieving processes. (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) 3.3.3.3

A balance readable to 1.0 g. A balance readable to 0.1 g. Sample divider(s) of appropriate slot width (riffle boxes). Thermostatically controlled drying oven capable of maintaining 105±50C. An evaporating dish about 150 mm diameter. A corrosion-resistant tray, a convenient size being about 300 mm square and 40 mm deep. Two or more large corrosion-resistant metal or plastics watertight trays with sides about 80 mm deep, or a bucket of about 12 L capacity. A scoop. Sieve brushes, and a wire brush or similar brush. Sodium hexametaphosphate (dispersing agent). A quantity of rubber tubing about 6 mm bore. A sprayer such as a small watering can use. Appropriate number of enamel or porcelain dishes. A mechanical sieve shaker (optional).

Test procedure (1)

(2) (3)

The representative riffled sample is oven-dried at 105±50C to give a minimum mass complying with Table 3.3.3. If separation of the silt and clay fractions is to be carried out, or if the particle size distribution is to be extended below 75 µm, a second riffled sample shall be obtained for a fine analysis. Weigh the cooled oven-dried sample to 0.1% of its total mass (m1). Sieve the sample through all required sieve sizes of 20 mm size and larger. The mass retained is recorded on the test sheet in each case. Any fine particles adhering to the retained material should be removed with a stiff brush during sieving. The brushing should be done carefully to avoid losing material. Take care with soft materials to ensure that the brushing does not remove parts of the large particles. Note.

If adhering fine material cannot be removed easily by brushing, the following procedure may be followed.

a) Remove the fine material from the coarse particles by washing. b) Dry and weigh the coarse particles to 0.1% of their mass. c) Dry the washings, add them to the material passing the 20 mm test sieve, and mix thoroughly. (4)

The mass passing the 20 mm sieve is determined to 0.1% of its total mass (m2) and the sample is then divided (riffled) so that about 2 kg of material remains. The mass of this sub-sample is then determined to 0.1% of its total mass (m3).

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(6) (7)

The sample shall then be placed in a large tray, enamel or porcelain bowl or in the bucket, and covered with water. If the soil is cohesive add sodium hexametaphosphate first at the rate of 2 grams per litre of water and stir until dissolved. Sodium hexametaphosphate is a dispersing agent and helps to prevent fine particles sticking together. The sample should be soaked for a minimum of 1 hour and frequent stirring should be given during this time. The sample is then washed through the 75 µm (No. 200) sieve with a 2 mm mesh sieve placed on top of it to protect it. Washing is most easily done by the decantation method. In this method, water is slowly added to the bowl or tray and the contents are vigorously stirred. Allow the contents to settle for a few seconds before pouring. The excess water is decanted carefully over the side of the bowl through the 2 mm sieve and into the 75 µm sieve, making sure all the water passes through the 75 µm sieve before running to waste. This process is continued until the water leaving the bowl is perfectly clear and all clay and silt particles have been washed through the sieve. Make sure that the fine sieve does not become overloaded, either by retained soil or by water. Note.

(8) (9) (10)

(12)

(13)

During this process DO NOT rub the material on the 75 µm sieve with your fingers or otherwise. This is likely to damage the sieve and give errors in the test results.

On completion of washing place the washed sample in a tray or evaporating dish and place in the oven to be dried at 105±50C. After drying and cooling, weigh the sample to 0.1% of its total mass before commencing sieving (m4). Fit the largest size test sieve appropriate to the maximum size of material present to the receiver and place the sample on the sieve. Fit the lid to the sieve. Note.

(11)

Standard Test Procedures

If the sieve and receiver assembly is not too heavy to handle, several sieves, in order of size, may be fitted together and used at the same time.

Agitate the test sieve so that the sample rolls about in an irregular motion over the sieve. Particles may be placed by hand to see if they will fall through but they must not be pushed through. Make sure that only individual particles are retained. Weigh the amount retained on the test sieve to 0.1% of its total mass. Keep each fraction separate so that check weighings may be carried out at a later date if required. Transfer the material retained in the receiver to a tray and fit the receiver to the next largest sized sieve. Place the contents of the tray on the sieve and repeat the operation in (11). Be careful not to lose fine material by using a brush to clean the sieve mesh and the receiver. Use of the lid helps to reduce loss of fines. Sieving is then continued through progressively smaller sizes until the sample has been passed through the 6.3 mm sieve. The mass of soil passing the 6.3 mm sieve is determined to 0.1% of its total mass (m5). If the mass of material passing the 6.3 mm sieve is too big (i.e. substantially more than 150 grams), the actual mass passing should be recorded and the sample divided again by riffling to give a reduced sample of about 100 to 150 grams. The mass of the sub-sample is then determined to 0.1% of its total mass (m6). Sieving is now continued through the remaining sieve sizes. The mass retained on each sieve is recorded to 0.1% of its total mass. The mass passing the 75 µm sieve should be determined (ME). This mass will be very small if washing has been carried out thoroughly. If any of the sieves are in danger of becoming overloaded the sample should be sieved a little at a time and the material MAY 2001

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retained each time placed in a clean porcelain or enamel dish ready for weighing. Note 1. If a mechanical sieve shaker is available this may be used to perform the sieving operation provided that all the sieves are the same diameter and that they are not overloaded during the process. A minimum shaking time of 10 minutes is required. 2. Sample dividing is carried out to prevent having to sieve large amounts of material through the fine sieve sizes with the consequent risk of overloading. If only one or two fine sieves are to be used it may be quicker not to divide the sample and to sieve the total sample through these sieves a little at a time. If 20 mm or 6.3 mm sieves are not being used, dividing may be carried out for convenience at the sieve closest to 20 mm and 6.3 mm. 3.3.3.4

Calculation and expression of results (1)

Summation Check. The first stage in the calculation is to check that all the weights retained add up to those of the original sample or sub-samples making due allowance for the weights passing the smallest sieve and any sieve where the sample has been divided. If these weights are not close to the correct total (i.e. within 1%) it is then possible to re-weigh the containers and to locate any errors before the sample is discarded. If this check is left until a later date it will be necessary to repeat the complete test if any error is found.

(2)

Calculation of correction factors a) It is necessary to calculate the correction or riffle factor for the first sieve size where the sample has been divided: Correction factor, f1 =

Original mass passing sieve size Mass of sub - sample after dividing =

m2 m3

b) The correction factor is then applied to each sieve smaller than the one where the sample was divided until the sample is again sub-divided. Where a second sub-division takes place the new correction factor is given by : New correction factor, f2 = f1 x

=

Original mass passing sieve size Mass of sub - sample after dividing

m2 m x 5 m3 m6

c) The adjusted mass retained MAR is then obtained for each sieve size by multiplying the actual mass retained MR by the respective correction factor. Adjusted mass retained MAR = f x MR d) The percentage retained is obtained by dividing the adjusted weight retained by the total sample weight and expressing the result as a percentage: MAY 2001

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M

% Retained =

AR x 100% m1

e) The cumulative percentage passing is then obtained by deducting the percentage retained on the largest sieve size from 100% and then deducting the percentage retained for each smaller size from the previous cumulative percentage. f) The percentages retained on each sieve and cumulative percentages passing each sieve should be calculated to the nearest 0.1%. The values can be expressed in tabular form and / or in graphical form. An example of a sieve test calculation is shown in Form 3.3.1, and the results are shown plotted on a semi-logarithmic chart in Form 3.3.3. 3.3.3.5

Report. The report should include the tabulated results of the test calculated as cumulative percentages passing to the nearest whole number. The results should be plotted on a semi-logarithmically form (see Form 3.3.3). The method of test should be reported and the operator should sign and date the test sheet.

3.3.4

Dry sieving method

3.3.4.1

Scope. This method covers the quantitative determination of the particle size distribution of a soil down to the fine sand size. It should only be used with clean, free running or washed sands and gravels.

3.3.4.2

Apparatus. The apparatus used in the wet sieving method are also used in the dry sieving method.

3.3.4.3

Test procedure

3.3.4.4

(1) Oven dry the riffled sample at 105±50C to give a specified minimum mass and then cool and weigh to 0.1% of its total mass (m1). (2) Sieve the sample through all required sieve sizes of 20 mm size and larger. The mass retained is recorded on the test sheet in each case. (3) The mass passing the 20 mm sieve is determined to 0.1% of its total mass (m2) and the sample is then divided so that about 2 kg of material remains. The mass of this sub-sample is then determined to 0.1% of its total mass (m3). (4) Then sieve the dried and weighed sample through the largest sieve size required and the mass of the sample retained is recorded on the data sheet. Use of the lid will help to reduce loss of fines. (5) Sieving is then continued through progressively smaller sizes until the sample has been passed through the 6.3 mm sieve (m4). If the weight of the material passing the 6.3 mm sieve is too big (more than 150 gms). The actual mass passing should be recorded and the sample is divided to give a reduced sample of about 100 to 150 gms. The mass of the sub-sample is then determined to 0.1% of its total mass (m5). (6) Sieving is now continued through the remaining sieve sizes. The mass retained on each sieve is recorded to 0.1% of its total mass. The mass passing the 75 µm sieve should be determined (ME). If any of the sieves are in danger of becoming overloaded the sample should be sieved a little at a time and the material retained each time is placed in a clean porcelain or enamel dish ready for weighing. If a mechanical sieve shaker is used, a minimum shaking time of 10 minutes is required. Calculation and expression of results. The procedure is the same as of wet sieving method (section 3.3.3.4). An example of a sieve test calculation is shown in Form 3.3.2. MAY 2001

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Form 3.3.1

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Standard Test Procedures Form 3.3.2

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Standard Test Procedures Form 3.3.3

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3.4

Determination of Organic Content

3.4.1

Scope. The “Loss on Ignition”: method for the determination of organic content is most applicable to those materials identified as peats, organic mucks, and soils containing relatively undecayed or undecomposed vegetative matter or fresh plant materials such as wood, roots, grass or carbonaceous materials such as lignite, coal, etc. This method determines the quantitative oxidation of organic matter in these materials and gives a valid estimate of organic content.

3.4.2

Apparatus

3.4.2.1

3.4.2.5 3.4.2.6 3.4.2.7

Oven-Drying oven capable of maintaining temperatures of 110±5 C (230±9 F). Gravity, instead of blower convection may be necessary when drying lightweight material. Balance-(to required sensitivity) Muffle Furnace-The furnace shall be capable of maintaining a continuous temperature of 445±10 C (833±18 F) and have a combustion chamber capable of accommodating the designated container and sample. Pyrometer recorder shall indicate temperature while in use. Crucibles or Evaporating Dishes-High silica, alundum, porcelain or nickel crucibles of 30 to 50 ml capacity or Coors porcelain evaporating dishes approximately 100 mm top diameter. Desiccator-A desiccator of sufficient size containing an effective dessicant. Containers-Suitable rustproof metal, porcelain, glass or plastic coated containers. Miscellaneous Supplies-Asbestos gloves, tongs, spatulas, etc.

3.4.3

Sample preparation

3.4.3.1

A representative sample weighing at least 100 grams shall be taken from the thoroughly mixed portion of the material passing the 2.00 mm (No. 10) sieve. Place the sample in a container and dry in the oven at 110±5 C (230±9 F) to constant weight. Remove the sample from the oven, place in the desiccator and allow to cool.

3.4.2.2 3.4.2.3

3.4.2.4

3.4.3.2

Note 1.

This sample can be allowed to remain in the oven until ready to proceed with the remainder of the test.

3.4.4

Ignition procedure

3.4.4.1

Select a sample weighing approximately 10 to 40 grams, place into tared crucibles or porcelain evaporating dishes and weigh to the nearest 0.01 gram. Note 2.

3.4.4.2

3.4.4.3

Sample weights for lightweight materials such as peat may be less than 10 grams but should be of sufficient amount to fill the crucible to at least ¾ depth. A cover may initially be required over the crucible during initial phase of ignition to decrease possibility sample being “blow out” from the container.

Place the crucible or dish containing the sample into the muffle furnace for six hours at a temperature of 445±10 C. Remove the sample from the furnace, place into the desiccator and allow to cool. Remove the cooled sample from the desiccator and weigh to the nearest 0.01 gram.

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3.4.5

Calculation

3.4.5.1

The organic content shall be expressed as a percentage of the mass of the oven dried soil and shall be calculated as follows:

Percent Organic Matter =

A - B x 100 A - C

where: A = Weight of crucible or evaporating dish and oven dried soil, before ignition B = Weight of crucible or evaporating dish and dried soil, after ignition. C = Weight of crucible or evaporating dish, to the nearest 0.01 gram. 3.4.5.2

Calculate the percentage of organic content to the nearest 0.1 percent.

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3.5

Standard Description and Classifications

3.5.1

Scope. The description of soils is an important stage in the process of sampling and testing of soils for civil engineering purposes. In order to be readily understood, the descriptions should be carried out in a standard and methodical manner. The terms “soil description” and “soil classification” are sometimes confused. Although interconnected, the use of the two terms can be separated and definitions are given in 3.5.2 below. Given individually, both a description and a classification may be useful. When used together, a greater understanding of the likely engineering characteristics of the soil can be obtained.

3.5.2

Definitions

3.5.2.1

Soil description. A full description gives detailed information on the grading, plasticity, colour, moisture and particle characteristics of a soil, as well as on the fabric and strength condition in which it occurs in a sample, borehole or exposure.

3.5.2.2

Soil classification. A classification places a soil in a limited number of groups on the basis of grading and plasticity of a disturbed sample. These characteristics are independent of the particular condition in which a soil occurs, and disregard the influence of the structure, including fabric, of the soil mass.

3.5.3

Soil groups and field identification methods

3.5.3.1

Coarse soils (over 65% sand and gravel sizes) (1) (2) (3) (4) (5)

3.5.3.2

Sands and gravels are coarse soils. Cobbles and boulders are very coarse soils. Coarse soils are visible to the naked eye. A small hand-lens may be useful for the examination of finer sands or the surface of larger particles. If required, a set of sieves may be used to determine approximate proportions (as judged by eye) of gravel sizes, e.g. 60 mm 20 mm, 6 mm and 2 mm. Sands, particularly those mixed with clay or silt fines, may usefully be examined mixed with a little water in the palm of the hand or in a small enamel bowl. Observations on the ease of excavation will be helpful. Whether the soil can be easily excavated with a spade, or requires a pickaxe or hoe for excavation will determine the consistency aspect of its description. If may also be useful to have available a wooden peg approximately 50 mm square with one sharpened end. The ease with which this can be hammered into the ground is an indication of the density of the soil.

Fine soils (over 35% silt and clay sizes) (1)

(2)

(3)

Fine soils require to be examined by hand to obtain an adequate description, preferably with the aid of a plastic was bottle containing water. This should readily aid the distinction of the soil between a clay and a silt. Silts can be detected by carrying out a test for dilatancy. A small sample of soil is mixed with water so that it is soft but not sticky, and held in the palm of the hand. The edge of the hand is jarred gently with the other hand and the sample observed. The appearance of a shiny film of water on the surface indicates dilatancy. Squeeze the soil by pressing with the fingers, and the surface will go dull again as the sample stiffens and finally crumbles. These reactions indicate the presence of predominantly silt-sized material or very fine sand, provided that the amount of moisture is not excessive. Moist silt is difficult to roll into threads since it crumbles easily. The most significant properties of clay are its cohesion and plasticity. If when pressed together in the hands at a suitable moisture content the particles stick MAY 2001

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(4)

(5)

3.5.3.3

Standard Test Procedures

together in a relatively firm mass, the soil shows cohesion. If it can be deformed without rupture (i.e. without losing its cohesion), it shows plasticity. Clay dries more slowly than silt and sticks to the fingers; it cannot be brushed off dry. It has a smooth feel, and shows a greasy appearance when cut with a blade. Dry lumps can be broken, sometimes with difficulty, between the fingers, but cannot be powdered. A lump placed in water remains intact for a considerable time. Clay does not exhibit dilatancy. Lumps shrink appreciably on drying, and show cracks which are the more pronounced the higher the plasticity of the clay. At a moisture content within the plastic range, clay can easily be rolled into threads of 3 mm diameter (as in the plastic limit test) which for a time can support their own weight. Threads of high - plasticity clay are quite tough; those of low-plasticity clay are softer and more crumbly. If it is important to know the composition of fine soils accurately then a particle size distribution test should be carried out subsequently in the laboratory.

Organic soils (1) (2)

Organic soils may be organic clay, silt or sand, or may be a form of peat. Examination in the field will be by visual and manual inspection in the same way as for other soils, paying particular attention to compactness and structure. Peat often has a distinctive smell and low bulk density. Laboratory testing will be necessary to accurately determine relative proportions of organic and mineral matter.

3.5.4

Methodology of description

3.5.4.1

General. In describing a soil, attention is given to a number of different aspects in a methodical manner, determined using the techniques outlined in Section 3.5.3 above. These aspects are summarised as follows, and are used in the order given, as far as is practicable. Descriptions made in the field may require to be modified subsequently in the light of the results of laboratory tests, or when better facilities are available for inspection. The preferred order of description is conveniently remembered as MCCSSO : a) b) c) d) e) f)

Moisture condition Consistency (compactness/strength) Colour Structure Soil type Origin

Examples of test forms 3.5.1 and 3.5.2 for use in the field are included at the end of this section. The test forms refer to the various elements of description as explained in detail in 3.5.4.2 below. 3.5.4.2

Descriptive terms (1)

Moisture condition. The moisture condition of the sample can be indicted by use of the following terms:

a) b)

Dry Slightly moist

: :

c) d) e)

Moist Very moist Wet

: : :

Soil will require the addition of water to attain the optimum moisture content for compaction (OMC). Near OMC for compaction Will require drying to achieve OMC From below water table.

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(2)

Standard Test Procedures

Consistency. Consistency or compactness/strength of the soil is described using different terms for different soil types. These terms and the field tests for them are given in Tables 3.5.1 to 3.5.5. Table 3.5.1 Very coarse soils -boulders and cobbles Term Field test Loose By inspection of voids and Dense particle packing Table 3.5.2 Coarse soils - gravels and sands Term Field test Very loose Crumbles very easily when scraped with geological pick. Loose Can be excavated with a spade; 50 mm wooden peg can be easily driven. Medium dense Between loose and dense. Dense Requires pickaxe or hoe for excavation; 50 mm wooden peg hard to drive. Slightly cemented For sands. Visual examination; pickaxe or hoe removes soil in lumps which can be abraded. Table 3.5.3 Fine soils - silts Term

Field test Easily moulded or crushed in the fingers. Can be moulded or crushed by strong pressure in the fingers. Exudes between fingers when squeezed in hand (like toothpaste).

Soft or loose Firm or dense Very soft

Table 3.5.4 Fine soils - clays Term Very soft Soft Firm Stiff Very stiff or hard

Field test Comes out between fingers (like toothpaste) when squeezes in hand. Moulded by light finger pressure. Can be moulded by strong finger pressure. Cannot be moulded by fingers. Can be indented by thumb. Can be indented by thumbnail.

Table 3.5.5 Organic soils Basic Soil Type Organic Clay, silt or sand

Term Firm Spongy

Field test Fibres already compressed together Very compressible and open structure

Peats Plastic

MAY 2001

Can be moulded in hand, and smears fingers.

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Chapter 3 Classification Tests (3)

Standard Test Procedures

Colour. The colour of soil samples should be assessed in a freshly excavated condition. This colour may be different from a dried sample, and from the sample mixed with water. Under some circumstances it may be important to know these differences. It is preferable to use a standard colour chart such as that developed by Munsell. If standard colour charts are not available, use colour descriptions which are readily understood, e.g. red, brown, green, yellow, white black, pink etc. These can be supplemented by the use of words like: light, dark etc. Soils can also be one colour mottled with another, or one colour blotched or veined with another.

(4)

Structure. The soil being sampled may have a distinct structure and if so this should be recorded in the description. Tables 3.4.6 to 3.4.10 present guidelines for the descriptive terms to be used. Table 3.5.6 Coarse and very coarse soils. Boulders, cobbles, gravels and sands Term Homogeneous Interstratified

Heterogeneous Weathered

Field identification Deposit consists essentially of one type. Alternating layers of varying types or with bands or lenses of other materials. Interval scale for bedding spacing may be used (see Table 3.5.7). A mixture of types. Particles may be weakened and may show concentric layering.

Table 3.5.7 Scale of bedding spacing (see Table 3.5.6) Term Very thickly bedded Thickly bedded Medium bedded Thinly bedded Very thinly bedded Thickly laminated Thinly laminated

Mean spacing, mm Over 2000 2000 to 600 600 to 200 200 to 60 60 to 20 20 to 6 Under 6

Table 3.5.8 Fine soils – silts and clays Term Fissured

Intact Homogeneous Interstratified Weathered Slicken sided

Field identification Break into polyhedral fragments along fissures. Interval scale for spacing of discontinuities may be used (see Table 3.5.9). No fissures or joints. Deposit consists essentially of one type. Alternating layers of varying types. Interval scale for thickness of layers may be used (see Table 3.5.7). Usually has crumb or columnar structure. Indicates the presence of fissures with polished or scratched surfaces.

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Chapter 3 Classification Tests

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Table 3.5.9 Scale of spacing of other discontinuities (see Table 3.5.8) Term Very widely spaced Widely spaced Medium spaced Closely spaced Very closely spaced Extremely closely spaced

Mean spacing, mm Over 2000 2000 to 600 600 to 200 200 to 60 60 to 20 under 20

Table 3.5.10 Organic soils – peats Term Fibrous Amorphous (form is lacking) (5)

Field identification Plant remains recognizable. Recognizable plant remains absent.

Soil type a) The basic soil type to be described, their limiting sizes and visual identification are given in Table 3.5.11. In the description the predominant soil type is written in capital letters, e.g. GRAVEL. Typical grading curves which would be obtained on well graded, uniformly graded and gap graded coarse soils are shown in Figure 3.5.1.

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Chapter 3 Classification Tests

Standard Test Procedures

Table 3.5.11 Soil types

Very Coarse soils

Basic soil type BOULDERS

Particle size, mm

Visual identification Only seen complete in pit or exposures.

200 COBBLES

Often difficult to recover from boreholes. 60 coarse

Easily visible to naked eye; particle shape can be described; grading can be described. 20

Coarse soils (over 65% sand and gravel sizes)

GRAVELS

medium

6

Well graded : wide range of grain sizes, well distributed. Poorly graded : not well graded. (May be uniform : size of most particles lies between narrow limits; or gap graded : an intermediate size of particle is markedly underrepresented.

fine 2 coarse SANDS

Visible to naked eye; very little or no cohesion when dry; grading can be described. 0.6

medium

0.2

Well graded : wide range of grain sizes, well distributed. Poorly graded : not well graded. (May be uniform : size of most particles lies between narrow limits; or gap graded : an intermediate size of particle is markedly underrepresented.

fine 0.06 SILTS

coarse

Organic soils

Fine soils (over 35% silt and clay sizes)

0.02

Only coarse silt barely visible to naked eye; exhibits little plasticity and marked dilatancy : slightly granular or silky to the touch. Disintegrates in water; lumps dry quickly; possess cohesion but can be powdered easily between fingers.

medium 0.006 fine 0.002 CLAYS

ORGANIC CLAY, SILT or SAND

varies

PEATS

varies

Dry lumps can be broken but not powdered between the fingers; they also disintegrate under water but more slowly than silt; smooth to the touch; exhibits plasticity but no dilatancy; sticks to the fingers and dries slowly; shrinks appreciably on drying usually showing cracks. Intermediate and high plasticity clays show these properties to a moderate and high degree, respectively. Descriptions should include an indication of plasticity if possible. Contains substantial amounts of organic vegetable matter. Predominantly plant remains usually dark brown or black in colour, often with distinctive smell; low bulk density.

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Chapter 3 Classification Tests

Standard Test Procedures

b) Many (most) soils exist as composite soil types, i.e. mixtures of basic soil types. Examples would be a slightly clayey GRAVEL, or a silty SAND. In these examples the clay and silt are secondary constituents. The secondary constituents are included in the description according to a set scale. This scale of proportions for secondary constituents for secondary constituents for coarse soils is set out in Table 3.5.12 and for fine soils in Table 3.5.13. Table 3.5.12 Scale of secondary constituents with coarse

soils

Term

% of clay

Remarks

or silt slightly clayey

GRAVEL or SAND

slightly silty - clayey

GRAVEL or

- silty

10.5

very clayey

GRAVEL or SAND

very silty Sandy GRAVEL Gravelly SAND

under 5

5 to 15

Percentage of clay

or silt has to be estimated in the field.

15 to 35

Sand or gravel and important second constituent of the coarse fraction

Note : For composite types described as: clayey : fines are plastic, cohesive: silty : fines non-plastic or of low plasticity Table 3.5.13 Scale of secondary constituents with fine soils Term sandy gravelly

% of sand or gravel

CLAY or SILT

35 to 65 (Assessed by eye)

- CLAY : SILT

under 35 (Assessed by eye)

c) Coarse and very coarse soils can be given a supplementary description for their shape and for the texture of their surface. Standard descriptive terms for shape are given in Table 3.5.14, and for texture in Table 3.5.15. Figure 3.5.2 shows typical shapes for descriptive purposes.

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Chapter 3 Classification Tests

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Chapter 3 Classification Tests

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Table 3.5.14 Angularity and form of coarse particles

Angularity

Term Angular Subangular Subrounded Rounded

Form

Equidimensional Flat (flaky) Elongated Flat and elongated Irregular

Remarks Possessing well-defined edges formed at the intersection of roughly planar faces. Corners slightly bevelled. All corners rounded off. Fully water-worn or completely shaped by attrition. All dimensions roughly equal. Having one dimension significantly smaller than the other two dimensions. Having one dimension significantly larger than the other two dimensions. See Figure 3.5.2. Naturally irregular, or partly shaped by attrition and having rounded edges.

Table 3.5.15 Surface texture of coarse soils Typical descriptive terms rough smooth honeycombed pitted glassy (6)

Origin. This part of the description consists of information on the geological formation, age and type of deposit. This information may not always be available to persons carrying out field descriptions but should be included where it is available. Examples of the kind of information to be included would be: a) b) c) d) e) f)

Girujan Clay Dihing Formation Tippam Group River deposit (alluvium) Beach deposit (littoral) Lake deposit (lacustrine)

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Chapter 3 Classification Tests 3.5.4.3

Standard Test Procedures

Examples (1)

Coarse soils An example of a completed test sheet for coarse soils is shown as Form 3.5.1. Two further examples of descriptions for coarse soils are given below: Example 1

Example 2

(a) Moisture condition :

damp

moist

(b) Consistency :

loose

dense

dark brown

yellow

homogeneous

+ thin lenses of soft

(c) Colour : (d) Structure :

grey silty CLAY (e) Soil Type :

sandy rounded smooth textured fine medium

Fine and medium (FM) SAND

and coarse (FMC) GRAVEL (f) Origin :

beach deposit

Recent Alluvium

Composite description for Example 1 : Damp loose dark brown homogeneous sandy smooth textured rounded fine medium and coarse GRAVEL. Beach Deposit. Composite description for Example 2 : Moist dense yellow fine and medium SAND with thin lenses of soft grey silty CLAY. (2)

Fine soils An example of a completed test sheet for fine soils is shown as Form 3.5.2. Two further examples of descriptions for fine soils are given below: Example 1

Example 2

(a) Moisture condition :

wet

dry

(b) Consistency :

soft

firm to stiff

blue-grey

grey mottled brown

(d) Structure :

+ closely spaced partings of firm brown SILT

widely fissured

(e) Soil Type :

sandy CLAY

silty CLAY

(c) Colour :

(high plasticity) (f) Origin :

Recent Alluvium

-

Composite description for Example 1 : Wet soft blue-grey sandy CLAY of high plasticity with closely spaced partings of firm brown SILT. Recent Alluvium. Composite description for Example 2 : Dry firm to stiff grey mottled brown widely fissured silty CLAY. MAY 2001

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Chapter 3 Classification Tests

3.5.4.4

Standard Test Procedures

Standard symbols. Soils descriptions carried out as part of a site investigation programme can be shown in borehole and trial pit records in the form of symbols. Standard symbols for soils are presented in Figure 3.5.3.

Made ground

Boulders and cabbles

Gravel

Sand

Silt

Clay

Peat Note. Comsite soil types will be signified by combined symbols, e.g. Silty sand

Figure 3.5.3 Note.

Standard soils symbols

Made ground means a soil which is artificially placed, e.g. in embankment.

An example of how these symbols might be used in a borrow area investigation is shown in Figure 3.5.4. Representing soil types in this manner should enable a clearer picture to be obtained of the soils in the area being investigated. Such a representation should be accompanied by a scaled plan to enable available quantities to be calculated. A second example of the use of standard symbols is shown in Figure 3.5.5. This is taken from a site investigation report for a road project.

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Chapter 3 Classification Tests

Standard Test Procedures

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Chapter 3 Classification Tests

Standard Test Procedures

MAY 2001

Page 3.47

Chapter 3 Classification Tests

Standard Test Procedures

MAY 2001

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Chapter 3 Classification Tests

Standard Test Procedures

MAY 2001

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

CHAPTER 4 DRY DENSITY – MOISTURE CONTENT RELATIONSHIP

4.1

General Requirements

4.1.1

Introduction. Compaction is defined as the process of increasing soil unit weight by forcing soil solids into a tighter state and reducing the air voids and thus increasing the stability and supporting capacity of soil. This is accomplished by applying static or dynamic loads to the soil. Laboratory compaction tests provide the basis for control procedures used on earthworks, sub-grades and also for pavement works on site.

4.1.2

Scope. Based upon the site conditions, nature of the works, the type of soil and the type of compaction equipment used, two types of tests are applied (1) Using rammer methods of compaction and (2) using vibrating methods of compaction.

4.1.3

Definitions and terminology. Definitions for the terminology used in compaction tests are given in Chapter 1. The terminology used in compaction tests is illustrated in Figure 4.1.1.

0% 5%

Air void lines for a given particle density

% 10

Dry density Mg/m

3

Maximum dry density

Compaction curve

0

Optimum moisture content

Saturation line

Moisture Content

Figure 4.1.1 Terminology used in compaction tests 4.1.4

Choice of compaction procedure A 1L internal volume compaction mould is used when not more than 5% of the soil particles are retained on a 20 mm sieve. Both the 2.5 kg and 4.5 kg rammer methods may be used. If there is a limited amount of particles up to 37.5 mm equivalent tests are carried out in the larger California Bearing Ratio (CBR) mould. The second type of test makes use of a vibrating hammer and is intended mainly for granular soils passing 37.5 mm test sieve, with not more than 30% retained on a 20 mm test sieve. The soil is compacted into a CBR mould. MAY 2001

Page 4.1

Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

4.2

Sample Preparation

4.2.1

General. For soils containing particles not susceptible to crushing, one sample is required for test and it can be used several times after progressively increasing the amount of water. For soils containing particles which are susceptible to crushing it is necessary to prepare separate batches of soil at different moisture contents. Consequently, a much larger sample is required. It may be necessary to carry out a trial compaction to determine whether the soil is susceptible to crushing. For stiff, cohesive soils, suggested methods are to shred the soil so that it could pass through a 5 mm test sieve, or to chop it into pieces, e.g. to pass a 20 mm sieve.

4.2.2

Preliminary assessment of soil. An assessment of the soil is required in order to determine which method of compaction should be used and the sample size required. The first assessment is to decide if the soil is susceptible to crushing, i.e. whether it contains weak particles which will crush during compaction with a 2.5 kg rammer. If sufficient sample is available it is preferable to use a method which assumes that the soil susceptible to crushing. The second assessment is to decide the approximate percentages (to an accuracy of ±5%) by mass of particles passing the 20 mm and 37.5 mm sieves. Having determined the approximate percentages passing the 37.5 mm and 20 mm sieves, the compaction test sample can be assigned to one of six grading zones. These are numbered 1 to 5 and (x) and defined in Table 4.2.1.

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

Table 4.2.1 Summary of sample preparation methods Grading zone

Minimum percentage passing test sieves

Preparation procedure Table reference

Minimum mass of prepared soil required

20 mm

37.5

(a)

(a)

(1)

100%

100%

(2)

95

100

(3)

70

100

(4)

70

95

(5) (X)

70 Less

90 Less

) ) ) ) ) ) ) ) ) )

(b)

) ) 4.2

4.4

Type of

(b)

kg 6

kg 15

1L

4.3

) ) 4.5 ) 16 40 ) ) (Tests not applicable)

CBR

(a) Soil particles not susceptible to crushing during compaction. (b) Soil particles susceptible to crushing during compaction. 1L = one-litre compaction mould. CBR = CBR mould. Table 4.2.1 also gives the method of sample preparation, the minimum mass of soil required and the type of mould to be used for the compaction test. 4.2.3

Preparation procedure. The procedure to be adopted depends on the grading zone into which the sample falls (see Table 4.2.1) and whether the soil is susceptible to crushing. The procedures are given hereafter in a series of tables, detailed as follows; a) Table 4.2.2. Using 1L compaction mould for soils not susceptible to crushing. Grading Zones : 1 and 2. b) Table 4.2.3. Using 1L compaction mould for soils susceptible to crushing. Grading Zones : 1 and 2. c) Table 4.2.4. Using CBR compaction mould for soils not susceptible to crushing. Grading Zones : 3, 4 and 5. d) Table 4.2.5. Using CBR compaction mould for soils susceptible to crushing. Grading Zones : 3, 4 and 5. MAY 2001

Page 4.3

Chapter 4 Dry Density – Moisture Content Relationship

Table 4.2.2

Sample preparation procedure

Standard Test Procedures

Using 1L mould

1 2 Min. % passing 37.5 mm = 100% Min. % passing 37.5 mm = 100% Min. % passing 20mm = 100% Min. % passing 20mm = 95% If soil is too wet to process, air or oven dry at not more than 500 C. Avoid drying completely. Gently break aggregation of soil. Determine moisture content. Weigh to 0.1% by mass the whole sample and record the mass. Riffle/quarter to about 6 kg Remove and weigh to 0.1% by passing 20 mm. mass the material retained on 20 mm sieve. Discard the material. Calculate additional water required Determine moisture content. for 1st compaction point, e.g. sandy and gravelly soils start at Riffle/quarter to about 6 kg 4%-6%, for cohesive soils start at passing 20 mm. 8%-10% below plastic limit. Add required water and mix thoroughly. Store mixed material in sealed container for minimum 24 h before compaction (particularly for cohesive soils). Note : Care should be taken in drying samples which may suffer irreversible changes as a result.

Soils not susceptible to crushing Grading zone 3 4 Min. % passing 37.5 mm = 100% Min. % passing 37.5 mm = 95% Min. % passing 20mm = 70% Min. % passing 20mm = 70%

5 Min. % passing 37.5 mm = 90% Min. % passing 20mm = 70%

1L mould not suitable for this soil grading

1L mould not suitable for this soil grading

1L mould not suitable for this soil grading

Calculate additional water required for 1st compaction point, e.g. sandy and gravelly soils start at 4%-6%, for cohesive soils start at 8%-10% below plastic limit. Add required water and mix thoroughly Store mixed material in sealed container for minimum 24 h before compaction (particularly for cohesive soils) Note : Care should be taken in drying samples which may suffer irreversible changes as a result. Note : As an alternative, the whole sample could be compacted in a CBR mould. In this case, material retained on 20 mm is not discarded.

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Chapter 4 Dry Density – Moisture Content Relationship

Table 4.2.3

Sample preparation procedure

Standard Test Procedures

Using 1L mould

1 2 Min. % passing 37.5 mm = 100% Min. % passing 37.5 mm = 100% Min. % passing 20mm = 100% Min. % passing 20mm = 95% If soil is too wet to process, air or oven dry at not more than 500 C. Avoid drying completely. Gently break aggregations of soil. Determine moisture content. Weigh to 0.1% by mass the whole sample and record the mass. Riffle/quarter sample into 5 or Remove and weigh to 0.1% by more representative samples, mass the material retained on 20 each of about 2.5 kg. mm sieve. Discard the material. Add required water and mix Determine moisture content. thoroughly (see individual test methods). Increments of 1%-2% Riffle/quarter sample into 5 or are appropriate for sandy and more representative samples, gravelly soils, and of 2%-4% for each of about 2.5 kg. cohesive soils. Store mixed material in sealed Add required water and mix container for minimum 24 h before thoroughly (see individual test compaction (particularly for methods). Increments of 1%-2% cohesive soils). are appropriate for sandy and gravelly soils, and of 2%-4% for Note : Care should be taken in cohesive soils. drying samples which may suffer irreversible changes as a result. Store mixed material in sealed container for minimum 24 h before compaction (particularly for cohesive soils) Note : Care should be taken in drying samples which may suffer irreversible changes as a result. Note : As an alternative, the whole sample could be compacted in a CBR mould. In this case, material retained on 20 mm is not discarded.

MAY 2001

Soils not susceptible to crushing Grading zone 3 4 Min. % passing 37.5 mm = 100% Min. % passing 37.5 mm = 95% Min. % passing 20mm = 70% Min. % passing 20mm = 70%

5 Min. % passing 37.5 mm = 90% Min. % passing 20mm = 70%

1L mould not suitable for this soil grading

1L mould not suitable for this soil grading

1L mould not suitable for this soil grading

Page 4.5

Chapter 4 Dry Density – Moisture Content Relationship

Table 4.2.4

Sample preparation procedure

Standard Test Procedures

Using CBR mould

1 Min. % passing 37.5 mm = 100% Min. % passing 20mm = 100%

2 Min. % passing 37.5 mm = 100% Min. % passing 20mm = 95%

Soils of this grading are more usually compacted in 1L moulds, except when CBR tests are to be carried out.

Soils of this grading are more usually compacted in 1L moulds, except when CBR tests are to be carried out.

Soils not susceptible to crushing Grading zone 3 4 5 Min. % passing 37.5 mm = 100% Min. % passing 37.5 mm = 95% Min. % passing 37.5 mm = 90% Min. % passing 20mm = 70% Min. % passing 20mm = 70% Min. % passing 20mm = 70% If soil is too wet to process, air or oven dry at not more than 500 C. Avoid drying completely. Gently break aggregation of soil. Determine moisture content Weigh to 0.1% by mass the whole sample and record the mass. Riffle/quarter to about 15 kg. Remove and weigh the material Remove and weigh the material retained on 37.5 mm. Discard this retained on 37.5 mm. Discard this material. material. Calculate additional water required for 1st compaction point, e.g. sandy and gravelly soils start at 4%-6%, for cohesive soils start at 8%-10% below plastic limit.

Determine moisture content.

Add required water and mix thoroughly.

Calculate additional water required for 1st compaction point, e.g. sandy and gravelly soils start at 4%-6%, for cohesive soils start at 8%-10% below plastic limit.

Determine moisture content.

Add required water and mix thoroughly.

Calculate additional water required for 1st compaction point, e.g. sandy and gravelly soils start at 4%-6%, for cohesive soils start at 8%-10% below plastic limit.

Store mixed material in sealed container for minimum 24 h before compaction (particularly for cohesive soils)

Note : Care should be taken in drying samples which may suffer irreversible changes as a result.

Riffle/quarter to about 25 kg.

Store mixed material in sealed container for minimum 24 h before compaction (particularly for cohesive soils) Note : Care should be taken in drying samples which may suffer irreversible changes as a result.

Replace this material by the same quantity of material of similar characteristics which passes 37.5 mm and is retained on 20 mm.

Riffle/quarter to about 15 kg.

Add required water and mix thoroughly. Store mixed material in sealed container for minimum 24 h before compaction (particularly for cohesive soils) Note : Care should be taken in drying samples which may suffer irreversible changes as a result.

MAY 2001

Page 4.6

Chapter 4 Dry Density – Moisture Content Relationship

Table 4.2.5

Sample preparation procedure

Standard Test Procedures

Using CBR mould

1 Min. % passing 37.5 mm = 100% Min. % passing 20mm = 100%

2 Min. % passing 37.5 mm = 100% Min. % passing 20mm = 95%

Soils of this grading are more usually compacted in 1L moulds, except when CBR tests are to be carried out.

Soils of this grading are more usually compacted in 1L moulds, except when CBR tests are to be carried out.

MAY 2001

Soils not susceptible to crushing Grading zone 3 4 5 Min. % passing 37.5 mm = 100% Min. % passing 37.5 mm = 95% Min. % passing 37.5 mm = 90% Min. % passing 20mm = 70% Min. % passing 20mm = 70% Min. % passing 20mm = 70% If soil is too wet to process, air or oven dry at not more than 500 C. Avoid drying completely. Gently break aggregation of soil. Determine moisture content Weigh to 0.1% by mass the whole sample and record the mass. Riffle/quarter sample into 5 or Remove and weigh the material Replace this material by the same more representative samples each retained on 37.5 mm. Discard this quantity of material of of about 6 kg. material. similar characteristics which passes 37.5 mm and is retained on 20 mm. Add required water and mix Determine moisture content. Determine moisture content. thoroughly (see individual test methods). Increments of 1%-2% Riffle/quarter sample into 5 or Riffle/quarter sample into 5 or are appropriate for sandy and more representative samples each more representative gravelly soils, and of 2%-4% for of about 6 kg. samples each of about cohesive soils. 6 kg. Store mixed material in sealed Add required water and mix Add required water and mix container for minimum 24 h before thoroughly (see individual test thoroughly (see compaction (particularly for methods). Increments of 1%-2% individual test cohesive soils) are appropriate for sandy and methods). Increments gravelly soils, and of 2%-4% for of 1%-2% are cohesive soils. appropriate for sandy and gravelly soils, and of 2%-4% for cohesive soils. Note : Care should be taken in Store mixed material in sealed Store mixed material in sealed drying samples which may suffer container for minimum 24 h before container for minimum irreversible changes as a result. compaction (particularly for 24 h before cohesive soils) compaction (particularly for cohesive soils) Note : Care should be taken in Note : Care should be taken in drying samples which may suffer drying samples which irreversible changes as a result. may suffer irreversible changes as a result.

Page 4.7

Chapter 4 Dry Density – Moisture Content Relationship 4.2.4

Standard Test Procedures

Modifying soil moisture content. When carrying out compaction tests it may be necessary to change the moisture content of the soil, either to a lower value, or to a higher value. The required calculations are: a) To decrease the moisture content from a value of x% to a value of y%, the mass of water required to be lost is;

x-y x M grams 100 + x where, M is the mass of the wet soil b) To increase the moisture content from a value of x% to a value of z%, the mass of water to be added is;

z- x x M grams 100 + x 4.3

Standard Compaction using 2.5 kg Rammer

4.3.1

Scope. This test method determines the optimum moisture content and maximum dry density of a soil when compacted into a mould in three layers using a 2.5 kg rammer falling through a height of 300 mm. In this method, 1L mould is used for soils passing 20 mm sieve and CBR mould is used for soils containing not more than 30% by mass of material on the 20 mm sieve which may include some particles retained on the 37.5 mm sieve.

4.3.2

Apparatus. The following general apparatus is required for the test : a) b) c) d)

2.5 kg compaction rammer (see Figure 4.3.1). Sieves of 20 mm and 37.5 mm, with receiver. Spatula or palette knife. Straight edge, e.g. a steel strip about 300 mm long, 25 mm wide, and 3 mm thick, with one beveled edge. e) Sample tray of plastics or corrosion-resistant metal with sides, e.g. about 80 mm deep. f) Apparatus for the determination of moisture content. g) Scoop. h) Additionally for test using 1L mould : a compaction mould similar to the one shown in Figure 4.3.2; a balance readable to 1 g. i) Additionally for test using CBR mould : a compaction mould similar to the one shown in Figure 4.3.3; a balance readable to 5 g.

MAY 2001

Page 4.8

Chapter 4 Dry Density – Moisture Content Relationship 4.2.4

Standard Test Procedures

Modifying soil moisture content. When carrying out compaction tests it may be necessary to change the moisture content of the soil, either to a lower value, or to a higher value. The required calculations are: a) To decrease the moisture content from a value of x% to a value of y%, the mass of water required to be lost is;

x-y x M grams 100 + x where, M is the mass of the wet soil b) To increase the moisture content from a value of x% to a value of z%, the mass of water to be added is;

z- x x M grams 100 + x 4.3

Standard Compaction using 2.5 kg Rammer

4.3.1

Scope. This test method determines the optimum moisture content and maximum dry density of a soil when compacted into a mould in three layers using a 2.5 kg rammer falling through a height of 300 mm. In this method, 1L mould is used for soils passing 20 mm sieve and CBR mould is used for soils containing not more than 30% by mass of material on the 20 mm sieve which may include some particles retained on the 37.5 mm sieve.

4.3.2

Apparatus. The following general apparatus is required for the test : a) b) c) d)

2.5 kg compaction rammer (see Figure 4.3.1). Sieves of 20 mm and 37.5 mm, with receiver. Spatula or palette knife. Straight edge, e.g. a steel strip about 300 mm long, 25 mm wide, and 3 mm thick, with one beveled edge. e) Sample tray of plastics or corrosion-resistant metal with sides, e.g. about 80 mm deep. f) Apparatus for the determination of moisture content. g) Scoop. h) Additionally for test using 1L mould : a compaction mould similar to the one shown in Figure 4.3.2; a balance readable to 1 g. i) Additionally for test using CBR mould : a compaction mould similar to the one shown in Figure 4.3.3; a balance readable to 5 g.

MAY 2001

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

4 holes 6 mm dia RAMMER mass = 2.5 kg±25 g

GUIDE length of travel of rammer = 300 mm 330 mm 350 mm

25 mm dia

12 holes 6 mm dia 2 mm rubber gasket 48 mm 52 mm dia

50 mm dia

50 mm dia

Figure 4.3.1 BS 2.5 kg compaction rammer 118 mm dia extension collar

50 mm

three lugs

10 mm push fit mould body

105 mm dia

three pins

115.5 mm 10 mm 13 mm

baseplate 180 mm dia or 150 mm square

Figure 4.3.2 BS 1 L compaction mould

MAY 2001

Page 4.9

MAY 2001 10 mm

13 mm

Two lugs

three pins

three lugs

screw thread

230 mm dia or 200 mm square

127 mm

152 mm dia

10 mm

50 mm

165 mm dia

10 mm

127 mm

152 mm dia

168 mm dia 162 mm dia

50 mm

152 mm dia

Figure 4.3.3 Types of BS CBR compaction moulds

baseplate

mould body

push fit

extension collar

detachable base plate

mould body

extension collar

580 mm

128 mm

510 mm

50 mm dia

Figure 4.4.1 BS 4.5 kg compaction rammer

60 mm dia

52 mm dia

12 holes 6 mm dia

GUIDE length of travel of rammer = 450 mm

4 holes 6 mm dia

2 mm rubber gasket

25 mm dia

RAMMER total mass 4.5 kg±50 kg

Chapter 4 Dry Density – Moisture Content Relationship Standard Test Procedures

Page 4.10

Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

4.3.3

Calibration of apparatus

4.3.3.1

Types of moulds. The standard sizes for compaction moulds are detailed in Table 4.3.1. Table 4.3.1. Standard sizes for compaction moulds Type of mould

Nominal dimensions Diamet Height Volume mm mm cm3 105 115.5 1000

‘One litre’ CBR

152

127

2305

Height of extension, mm 50 minimum 50 minimum

4.3.3.2. Mould factors. The volume of the mould can be determined using vernier calipers. Measure its internal diameter (D mm) and length (L mm) in places to 0.1 mm. Calculate the mean dimensions, and the volume of the mould (V cm3) from the equation.

V =

π x D2 x L 4

If necessary, mould factors can be determined. The use of these factors may make calculations easier. Since the factors depend on physical measurements it is necessary to recalculate the values whenever changes in the measurements are suspected. 4.3.3.2.1 Mould area factors. The mould area factor, F is the reciprocal of the cross-sectional area in square meters, i.e.

F =

4 (1000)2 sq.m -1 2 π (D )

where, D = mould diameter in millimeters Example For the 1L compaction mould the mould area factor is :

F =

4 (1000)2 = 1273 . x 90.703 = 115.49 sq.m-1 π (105)2

4.3.3.2.2 Mould height factors. The mould height factor. H, is the same as the height of the mould in millimetres. For the 1L mould, the mould height factor is 115.5. 4.3.3.2.3 Mould factor ratio The mould factor ratio is calculated as

F H

For the 1L mould this is calculated as 1.000 4.3.4

Preparation of sample. The sample should be prepared in accordance with the requirements of Tables 4.2.2 or 4.2.3 for soils with particles up to medium gravel size 4.2.4 or 4.2.5 for soils with some coarse gravel size particles depending on whether the MAY 2001

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

soil is susceptible to crushing. When using Table 4.2.3 or 4.2.5, it can be useful to have more than 5 prepared sub-samples, in case further points need to be established on the compaction curve. 4.3.5

Test procedure

4.3.5.1

The mould including the base-plate is first weighed to an accuracy of 1 gm for medium gravel and 5 gms for coarse gravel (m1). Measure the internal dimensions to 0.1 mm for medium gravel and 0.5 mm for coarse gravel size.

4.3.5.2

Attach the extension (collar) to the mould and place the mould assembly on a solid base, e.g. a concrete floor.

4.3.5.3

The prepared sample of moist material is divided into three approximately equal portions.

4.3.5.4

Sufficient material from the first portion is then placed in the mould so that the mould is about a third full when the soil has been compacted. This first layer is then compacted using 27 blows for 1L mould and 62 blows for CBR mould of the 2.5 kg rammer dropping from a controlled height of 300 mm. The blows should be evenly distributed over the surface of the material and care should be taken to ensure that soil does not stick to the face of the hammer, thus reducing the height of fall.

4.3.5.5

Material from the second and third portions is then placed in the mould, each portion being compacted as above. The purpose of this procedure is to compact the soil in three equal layers and on completion, the mould should be completely filled. On removal of the collar, the top surface of the soil should be proud of the top rim of the mould body by an amount not exceeding 6 mm. If the soil is below the top rim of the mould or is proud of the mould by more than 6 mm, the test must be repeated.

4.3.5.7

The soil above the mould rim should then be struck off level with a metal straight edge. With some coarse-grained materials it may be difficult to obtain a smooth surface. Replace any coarse particles, removed in the leveling process, by finer material from the sample, well pressed in.

4.3.5.7

The mould, base-plate and soil are then weighed, to an accuracy of 1 gram for 1L mould and 5 gram for CBR mould (m2).

4.3.5.8

Remove the compacted soil from the mould and place it on the metal tray. Take a representative sample for determination of moisture content.

4.3.5.9

For soils not susceptible to crushing break up the remainder of the soil, rub it through the 20 mm sieve and mix with the remainder of the prepared test sample. In case of soils susceptible to crushing, discard the remaining soil from each of the 5 approximately 2.5 kg representative sub-samples.

4.3.5.10 Increase moisture 1% to 2% for sandy or gravelly soils and 2% to 4% for cohesive soils and mix thoroughly into the soil. As the test progresses, the size of the increments can be decreased to increase accuracy in determining the optimum moisture content. 4.3.5.11 Repeat steps 4.3.5.3 to 4.3.5.10 to give a total of at least 5 determinations. The moisture contents shall include the optimum moisture content, at which the maximum dry density occurs, this point being as near to the middle of the range as is practicable to achieve. Note.

Tables 4.2.2 to 4.2.5 recommend that samples of prepared soil be allowed to “cure” for 24 h before test, particularly if they are cohesive. Good laboratory MAY 2001

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Standard Test Procedures

soil is susceptible to crushing. When using Table 4.2.3 or 4.2.5, it can be useful to have more than 5 prepared sub-samples, in case further points need to be established on the compaction curve. 4.3.5

Test procedure

4.3.5.1

The mould including the base-plate is first weighed to an accuracy of 1 gm for medium gravel and 5 gms for coarse gravel (m1). Measure the internal dimensions to 0.1 mm for medium gravel and 0.5 mm for coarse gravel size.

4.3.5.2

Attach the extension (collar) to the mould and place the mould assembly on a solid base, e.g. a concrete floor.

4.3.5.3

The prepared sample of moist material is divided into three approximately equal portions.

4.3.5.4

Sufficient material from the first portion is then placed in the mould so that the mould is about a third full when the soil has been compacted. This first layer is then compacted using 27 blows for 1L mould and 62 blows for CBR mould of the 2.5 kg rammer dropping from a controlled height of 300 mm. The blows should be evenly distributed over the surface of the material and care should be taken to ensure that soil does not stick to the face of the hammer, thus reducing the height of fall.

4.3.5.5

Material from the second and third portions is then placed in the mould, each portion being compacted as above. The purpose of this procedure is to compact the soil in three equal layers and on completion, the mould should be completely filled. On removal of the collar, the top surface of the soil should be proud of the top rim of the mould body by an amount not exceeding 6 mm. If the soil is below the top rim of the mould or is proud of the mould by more than 6 mm, the test must be repeated.

4.3.5.7

The soil above the mould rim should then be struck off level with a metal straight edge. With some coarse-grained materials it may be difficult to obtain a smooth surface. Replace any coarse particles, removed in the leveling process, by finer material from the sample, well pressed in.

4.3.5.7

The mould, base-plate and soil are then weighed, to an accuracy of 1 gram for 1L mould and 5 gram for CBR mould (m2).

4.3.5.8

Remove the compacted soil from the mould and place it on the metal tray. Take a representative sample for determination of moisture content.

4.3.5.9

For soils not susceptible to crushing break up the remainder of the soil, rub it through the 20 mm sieve and mix with the remainder of the prepared test sample. In case of soils susceptible to crushing, discard the remaining soil from each of the 5 approximately 2.5 kg representative sub-samples.

4.3.5.10 Increase moisture 1% to 2% for sandy or gravelly soils and 2% to 4% for cohesive soils and mix thoroughly into the soil. As the test progresses, the size of the increments can be decreased to increase accuracy in determining the optimum moisture content. 4.3.5.11 Repeat steps 4.3.5.3 to 4.3.5.10 to give a total of at least 5 determinations. The moisture contents shall include the optimum moisture content, at which the maximum dry density occurs, this point being as near to the middle of the range as is practicable to achieve. Note.

Tables 4.2.2 to 4.2.5 recommend that samples of prepared soil be allowed to “cure” for 24 h before test, particularly if they are cohesive. Good laboratory MAY 2001

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practice should allow this is most cases. However, and in particular when testing sandy or gravelly soils, it may be possible to reduce or omit this requirement altogether. In the latter case, an estimate can be made of the likely optimum moisture content, and the first sub-sample made up and compacted immediately at that moisture content, following the procedures in 4.3.5.1 to 4.3.5.8.. The necessary weighings and calculations should be recorded on the test sheet. The compaction procedure is then repeated on two further sub-samples, at appropriate moisture contents above and below the estimated optimum. At this stage an estimate can be made of the dry densities of the specimens, using the calculated bulk densities and the assumption that the moisture contents are in fact what they were made up to be. From this information it can be determined where the three points are likely to lie on the final moisture content / dry density relationship curve, and the remaining specimens can then be moistened and compacted accordingly. This method can achieve reliable results on suitable soils if carefully carried out. 4.3.6

Calculation and expression of results

4.3.6.1

Calculate the internal volume of the mould. V (in cm3).

4.3.6.2 Calculate the bulk density, ρ (in Mg/m3) of each of the compacted specimens from the equation

ρ =

m2 − m1 V

where, m1 is the mass of mould and base-plate (in g); m2 is the mass of mould, base-plate and compacted soil (in g). Note.

Where the height of the compacted soil specimen is the same as the height of the compaction mould body, e.g. in the case of the 2.5 kg and 4.5 kg rammer methods, the mould factors can be used to calculate the bulk density of the soil as;

 F ρ = m 2 − m1 x    H In the vibrating hammer test, where the height of the compacted soil specimen may be different from the height of the compaction mould body the calculation then becomes

ρ =

m2 − m1 x F H - h

Refer to Part 4.5 and Forms 4.3.1 to 4.3.4. The dry density ρd of each compacted specimen is then calculated (in kg/m3) using the formula; Dry density,

ρd = ρ x

100 100 + w

Where, w is the moisture content of the soil.

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Chapter 4 Dry Density – Moisture Content Relationship

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practice should allow this is most cases. However, and in particular when testing sandy or gravelly soils, it may be possible to reduce or omit this requirement altogether. In the latter case, an estimate can be made of the likely optimum moisture content, and the first sub-sample made up and compacted immediately at that moisture content, following the procedures in 4.3.5.1 to 4.3.5.8.. The necessary weighings and calculations should be recorded on the test sheet. The compaction procedure is then repeated on two further sub-samples, at appropriate moisture contents above and below the estimated optimum. At this stage an estimate can be made of the dry densities of the specimens, using the calculated bulk densities and the assumption that the moisture contents are in fact what they were made up to be. From this information it can be determined where the three points are likely to lie on the final moisture content / dry density relationship curve, and the remaining specimens can then be moistened and compacted accordingly. This method can achieve reliable results on suitable soils if carefully carried out. 4.3.6

Calculation and expression of results

4.3.6.1

Calculate the internal volume of the mould. V (in cm3).

4.3.6.2 Calculate the bulk density, ρ (in Mg/m3) of each of the compacted specimens from the equation

ρ =

m2 − m1 V

where, m1 is the mass of mould and base-plate (in g); m2 is the mass of mould, base-plate and compacted soil (in g). Note.

Where the height of the compacted soil specimen is the same as the height of the compaction mould body, e.g. in the case of the 2.5 kg and 4.5 kg rammer methods, the mould factors can be used to calculate the bulk density of the soil as;

 F ρ = m 2 − m1 x    H In the vibrating hammer test, where the height of the compacted soil specimen may be different from the height of the compaction mould body the calculation then becomes

ρ =

m2 − m1 x F H - h

Refer to Part 4.5 and Forms 4.3.1 to 4.3.4. The dry density ρd of each compacted specimen is then calculated (in kg/m3) using the formula; Dry density,

ρd = ρ x

100 100 + w

Where, w is the moisture content of the soil.

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

The determined moisture content should be within 1% of the required moisture content if the mixing and testing has been carried out correctly. The graph of dry density vs moisture content is then plotted as in Figure 4.1.1. The points should be joined by a curve of best fit. The maximum dry density (MDD) and corresponding optimum moisture content (OMC) are then determined from the graph. Read off these values to three significant figures. Note.

4.3.6.3

The maximum on the curve may lie between two points, but when drawing the curve, care should be taken not to exaggerate its peak.

If required, curves corresponding to air void contents can be plotted on the same graph (see Figure 4.1.1). These are calculated from the equation

Va 100 ρd = 1 w ρs 100 ρ w 1 -

where,

ρd ρs ρw Va w

4.3.7

is the dry density (in kg/m3); is the particle density (in kg/m3); is the density of water (in kg/m3), assumed equal to 1; is the volume of air voids in the soil expressed as a percentage of the total volume of the soil (equal to 0%, 5%, 10% for the purpose of the example); is the moisture content (in %).

Report. The test report shall contain the following information : a) the method of test used; b) the sample preparation procedure, and whether a single sample or separate samples were used. In the case of stiff, cohesive soil the size of pieces to which the soil was broken down shall be stated; c) the experimental points and the smooth curve drawn through them showing the relationship between moisture content and dry density; d) the dry density corresponding to the maximum dry density on the moisture content / dry density curve, reported as the maximum dry density to the nearest 0.01 (in Mg/m3); e) the percentage moisture content corresponding to the maximum dry density on the moisture content / dry density curve, reported as the optimum moisture content to two significant figures; f) the amount of stone retained on the 20 mm and 37.5 mm test sieves reported to the nearest 1% by dry mass; g) the particle density and whether measured (and if so the method used) or assumed. Examples of completed test sheets are given in Forms 4.3.1 to 4.3.4. In addition to the information above, the test sheets should contain full details of the sample description and location etc. The operator should sign and date the test sheets.

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

The determined moisture content should be within 1% of the required moisture content if the mixing and testing has been carried out correctly. The graph of dry density vs moisture content is then plotted as in Figure 4.1.1. The points should be joined by a curve of best fit. The maximum dry density (MDD) and corresponding optimum moisture content (OMC) are then determined from the graph. Read off these values to three significant figures. Note.

4.3.6.3

The maximum on the curve may lie between two points, but when drawing the curve, care should be taken not to exaggerate its peak.

If required, curves corresponding to air void contents can be plotted on the same graph (see Figure 4.1.1). These are calculated from the equation

Va 100 ρd = 1 w ρs 100 ρ w 1 -

where,

ρd ρs ρw Va w

4.3.7

is the dry density (in kg/m3); is the particle density (in kg/m3); is the density of water (in kg/m3), assumed equal to 1; is the volume of air voids in the soil expressed as a percentage of the total volume of the soil (equal to 0%, 5%, 10% for the purpose of the example); is the moisture content (in %).

Report. The test report shall contain the following information : a) the method of test used; b) the sample preparation procedure, and whether a single sample or separate samples were used. In the case of stiff, cohesive soil the size of pieces to which the soil was broken down shall be stated; c) the experimental points and the smooth curve drawn through them showing the relationship between moisture content and dry density; d) the dry density corresponding to the maximum dry density on the moisture content / dry density curve, reported as the maximum dry density to the nearest 0.01 (in Mg/m3); e) the percentage moisture content corresponding to the maximum dry density on the moisture content / dry density curve, reported as the optimum moisture content to two significant figures; f) the amount of stone retained on the 20 mm and 37.5 mm test sieves reported to the nearest 1% by dry mass; g) the particle density and whether measured (and if so the method used) or assumed. Examples of completed test sheets are given in Forms 4.3.1 to 4.3.4. In addition to the information above, the test sheets should contain full details of the sample description and location etc. The operator should sign and date the test sheets.

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Chapter 4 Dry Density – Moisture Content Relationship

MAY 2001

Standard Test Procedures

Page 4.15

Chapter 4 Dry Density – Moisture Content Relationship

MAY 2001

Standard Test Procedures Form 4.3.2

Page 4.16

Chapter 4 Dry Density – Moisture Content Relationship

MAY 2001

Standard Test Procedures

Page 4.17

Chapter 4 Dry Density – Moisture Content Relationship

MAY 2001

Standard Test Procedures

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

4.4

Heavy Compaction using 4.5 kg Rammer

4.4.1

Scope. This type of compaction is widely used for pavement materials and also for earthworks and sub-grades if a high standard of compaction is specified. This method may be carried out in the 1L compaction mould or in a CBR mould.

4.4.2

Apparatus, sample preparation and test procedure. The test is similar to the standard compaction (2.5 kg rammer) as described earlier, the only differences being that the sample is compacted in 5 equal layers with the 4.5 kg rammer dropping from a controlled height of 450 mm. The 4.5 kg rammer is shown in Figure 4.4.1. As previously each layer still receives 27 blows / layer for a 1L mould and 62 blows / layer for a CBR mould. Calculation and reporting of results are identical to those for 2.5 kg rammer compaction test.

4.5

Vibrating Hammer Method

4.5.1

Scope. This test is applicable to granular soils containing no more than 30% by mass of material retained on the 20 mm sieve, which may include some particles retained on the 37.5 mm sieve. It is not generally suitable for cohesive soils. The principle is similar to that of the rammer procedures except that a vibrating hammer is used instead of a drop-weight rammer, and a larger mould (the standard CBR mould) is necessary.

4.5.2

Apparatus a) Cylindrical metal mould, internal dimensions 152 mm diameter and 127 mm high (CBR mould). The mould can be fitted with an extension collar and base-plate. The mould is shown in Figure 4.3.3. b) Electric vibrating hammer, power consumption 600-800 W, operating at a frequency in the range 25-60 Hz. For safety reasons the hammer should operate on 110V and an earth-leakage circuit breaker (ELCB) should be included in the line between the hammer and the mains supply. c) Steel tamper for attaching to the vibrating hammer with a circular foot 145 mm diameter (see Figure 4.5.1 a) and b)). d) A balance readable to 5 g. e) 20 mm and 37.5 mm BS sieves and receiver. f) A straightedge, e.g. a steel strip about 300 mm long, 25 mm wide and 3 mm thick, with one beveled edge. g) Depth gauge or steel rule reading to 0.5 mm. h) Apparatus for the determination of moisture content. i) Laboratory stop-clock reading to 1 s. j) A corrosion-resistant metal or plastic trays with sides, e.g. about 80 mm deep of a size suitable for the quantity of material to be used. k) A scoop. l) Apparatus for extracting compacted specimens from the mould (optional).

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

4.4

Heavy Compaction using 4.5 kg Rammer

4.4.1

Scope. This type of compaction is widely used for pavement materials and also for earthworks and sub-grades if a high standard of compaction is specified. This method may be carried out in the 1L compaction mould or in a CBR mould.

4.4.2

Apparatus, sample preparation and test procedure. The test is similar to the standard compaction (2.5 kg rammer) as described earlier, the only differences being that the sample is compacted in 5 equal layers with the 4.5 kg rammer dropping from a controlled height of 450 mm. The 4.5 kg rammer is shown in Figure 4.4.1. As previously each layer still receives 27 blows / layer for a 1L mould and 62 blows / layer for a CBR mould. Calculation and reporting of results are identical to those for 2.5 kg rammer compaction test.

4.5

Vibrating Hammer Method

4.5.1

Scope. This test is applicable to granular soils containing no more than 30% by mass of material retained on the 20 mm sieve, which may include some particles retained on the 37.5 mm sieve. It is not generally suitable for cohesive soils. The principle is similar to that of the rammer procedures except that a vibrating hammer is used instead of a drop-weight rammer, and a larger mould (the standard CBR mould) is necessary.

4.5.2

Apparatus a) Cylindrical metal mould, internal dimensions 152 mm diameter and 127 mm high (CBR mould). The mould can be fitted with an extension collar and base-plate. The mould is shown in Figure 4.3.3. b) Electric vibrating hammer, power consumption 600-800 W, operating at a frequency in the range 25-60 Hz. For safety reasons the hammer should operate on 110V and an earth-leakage circuit breaker (ELCB) should be included in the line between the hammer and the mains supply. c) Steel tamper for attaching to the vibrating hammer with a circular foot 145 mm diameter (see Figure 4.5.1 a) and b)). d) A balance readable to 5 g. e) 20 mm and 37.5 mm BS sieves and receiver. f) A straightedge, e.g. a steel strip about 300 mm long, 25 mm wide and 3 mm thick, with one beveled edge. g) Depth gauge or steel rule reading to 0.5 mm. h) Apparatus for the determination of moisture content. i) Laboratory stop-clock reading to 1 s. j) A corrosion-resistant metal or plastic trays with sides, e.g. about 80 mm deep of a size suitable for the quantity of material to be used. k) A scoop. l) Apparatus for extracting compacted specimens from the mould (optional).

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

Vibrating Hammer Assembly Figure 4.5.1 (a)

Tamper for Vibrating Hammer Compaction Test Figure 4.5.1 (b)

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

4.5.3

Calibration of apparatus

4.5.3.1

General. The vibrating hammer shall be maintained in accordance with the manufacturer’s instructions. Its working parts shall not be badly worn. The calibration test described in 4.5.3.3 below shall be carried out to determine whether the vibrating hammer is in satisfactory working order, and able to comply with the requirements of the test.

4.5.3.2

Material. Clean, dry silica sand, from the (geological) Woburn Beds of the Lower Greensand in the Leighton Buzzard district of the UK. The grading shall be such that at least 75% passes the 600 µm sieve and is retained on the 425 µm sieve. Dry and not previously used sand shall be used. This sand shall be sieved through 1 600 µm test sieve and the coarse fraction shall be discarded. Note.

4.5.3.3

This is the standard sand as described in the British Standard. Advice on suitable suppliers can be obtained from BSI in the UK. Advice should be sought from BRRL as to whether a suitable sand is available locally, to reduce dependence on costly imports.

Calibration test a) Take a 5±0.1 kg sample of the specified in 4.5.3.2, which has not been used previously and mix it with water in order to raise its moisture content to 2.5±0.5%. b) Compact the wet sand in a cylindrical metal mould of 152 mm diameter and 127 mm depth, using the vibrating hammer as specified in the section on apparatus above. c) Carry out a total of three tests, all on the same sample of sand, and determine the mean dry density. Determine the dry density values to the nearest 0.002 Mg/m3. Note.

The operator can usually judge the required pressure to apply with sufficient accuracy after carrying out the check described in 4.5.4 below.

d) If the range of values in the three tests exceeds 0.01 Mg/ m3, repeat the procedure. Consider the vibrating hammer suitable for use in the vibrating compaction test if the mean dry density of the sand exceeds 1.74 Mg/m3. Note.

Advice should be sought from BRRL if a locally available replacement for the Leighton Buzzard sand is used and the replacement does not achieve a mean dry density of 1.74 Mg/m3.

4.5.3.3

Calibration of operator. Before being allowed to carry out the test the operator must practise with the apparatus in order to achieve the correct downward pressure required in the test. The downward force, including that resulting from the mass of the hammer and tamper should be 300-400 N. This force is sufficient to prevent the hammer bouncing up and down on the soil. The correct force can be determined by standing the hammer, without vibration, on a platform scale and pressing down until a mass of 30-40 kg is indicated. With experience the pressure to be applied can be judged, but an occasional check on the platform scale is advisable. If the hammer-supporting frame is used, the hand pressure required is much less but should be carefully checked.

4.5.5

Sample preparation. The procedure to be adopted depends on the grading zone into which the sample falls (see Table 4.2.1), and whether the soil is susceptible to crushing. Full details of sample preparation methods are given in Tables 4.2.2 to 4.2.5. The quantities of soil required are indicated in Table 4.2.1.

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Chapter 4 Dry Density – Moisture Content Relationship 4.5.6

Standard Test Procedures

Preparation of apparatus. See that the component parts of the mould are clean and dry. Assemble the mould, base-plate and collar securely, and weigh to the nearest 5 g (m1). Measure the internal dimensions of the assembly to 0.5 mm and calculate the internal volume. The nominal dimensions of the mould give an area of cross-section of 18, 146 mm2 and a volume of 2304.5 cm3 (say 2305 cm3) but these may change slightly with wear. The inside height of the mould with collar is recorded (h 1 mm). It is particularly important to ensure the lugs and clamps holding the mould assembly together are secure and in good condition, in order to withstand the effects of vibration. If the mould has screw-on fittings, the threads must be kept clean and undamaged. Avoid cross-threading when fitting the base-plate and extension collar, and make sure that they are tightened securely as far as they will go without leaving any threads exposed. Screw threads and mating surfaces should be lightly oiled before tightening. Ensure that the vibrating hammer is working properly, in accordance with the manufacturer’s instructions. See that it is properly connected to the mains supply, and that the connecting cable is in sound condition. The supporting frame if used, must move freely without sticking. The hammer should have been verified as described in 4.5.3.3. The tamper stem must fit properly into the hammer adapter, and the foot must fit inside the CBR mould with the necessary clearance (3.5 mm all round).

4.5.7

Test procedure

4.5.7.1

Place the mould assembly on a solid base, such as a concrete floor or plinth. If the test is to be performed out of doors because of noise and vibration problems place the mould on a concrete paved area, not on unpaved ground or on thin asphalt. Any resilience in the base results in inadequate compaction.

4.5.7.2

For soils susceptible to crushing, prepare the soil to provide a sample of about 40 kg from which 5 (or more) separate batches of about 8 kg are obtained and made up to different moisture contents. It is not necessary, for soils not susceptible to crushing, to be divided into 5 separate batches. Add a quantity of soil to the mould, such that after compaction the mould is one-third filled. A preliminary trial may be necessary to ascertain the correct amount of soil. A disc of polyethylene sheet, of a diameter equal to the internal diameter of the mould, may be placed on top of the layer of soil. This will help to prevent sand particles moving up through the annular gap between the tamper and the mould.

4.5.7.3

Compact the layer with the vibrating hammer, fitted with the tamper for 60±2 s, applying a firm pressure vertically downwards throughout. The downward force of 300-400 N should only be applied by a practised operator (see 4.5.4 above). Repeat the above compaction procedure with a second layer of soil, and then with a third layer. The final thickness of the compacted specimen should be between 127 mm and 133 mm: if it is not, remove the soil and repeat the test.

4.5.7.4

After compaction remove any loose material from the surface of the specimen around the edge of the mould collar. Lay the straight-edge across the top of the collar, and measure down to the surface of the specimen with the steel rule or depth gauge, to an accuracy of 0.5 mm. Take readings at four points spread evenly over the surface, all at least 15 mm from the side of the mould. Calculate the average depth (h2 mm). The mean height of the compacted specimen, h, is given by

h = (h1 - h2 ) mm MAY 2001

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Chapter 4 Dry Density – Moisture Content Relationship

Standard Test Procedures

where’ h1 = Height of mould. 4.5.7.5

Weigh the mould with the compacted soil, collar and base-plate to the nearest 5 g (m2).

4.5.7.6

Remove the soil from the mould and place on the tray. A jacking extruder makes this operation easy if fittings to suit the CBR mould are available. However, sandy and gravelly (non-cohesive) soil should not be too difficult to break up and remove by hand.

4.5.7.7

Take two representative samples in large moisture content containers for measurement of moisture content. This must be done immediately after removal from the mould, before the soil begins to dry out. The moisture content samples must be large enough to give results representative of the maximum particle size of the soil. The average of the two moisture content determinations is denoted by w%.

4.5.7.8

For soils susceptible to crushing, repeat step 4.5.7.1 to 4.5.7.7 on each batch of soil in turn. For soil not susceptible to crushing break up the material on the tray and rub it through the 20 mm or the 37.5 mm sieve if necessary, mixing with the remainder of the sample. Add an increment of water so as to raise the moisture content by 1 to 2% (150300 ml of water for 15 kg of soil). As the optimum moisture content is approached it is preferable to add water in smaller increments.

4.5.7.9

Repeat stages 4.5.7.1 to 4.5.7.8 for each increment of water added. At least five compactions should be made, and the range of moisture contents should be such that the optimum moisture content is within that range. If necessary, carry out one or more additional test at suitable moisture contents. Above a certain moisture content the soil may contain an excessive amount of free water, which indicates that the optimum condition has been passed.

4.5.8

Calculation and expression of results. The following stages apply to both the above procedures : Calculate the bulk density ρ (in kg/m3), of each compacted specimen from the equation

ρ = where,

m2 - m1 1000 Ah

m1 = mass of mould, collar and base-plate; m2 = mass of mould, collar and base-plate with soil; h = height of compacted soil specimen = h1 – h2 mm; A = circular area of the mould (in mm2).

Calculate the density, ρd (in kg/m3), of each compacted specimen from the equation

ρd =

100ρ 100 + w

where, w, is the moisture content of the soil. The results of the required calculations, as determinations of dry density and moisture content, are plotted as described in Part 4.3.6 and illustrated in Form 4.1.1 to 4.1.4. Calculations for air voids can be calculated if required as detailed in Part 4.3.6. 4.5.9

Report. The requirements for reporting are as detailed in 4.3.7.

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CHAPTER 5 STRENGTH TESTS CALIFORNIA BEARING RATIO AND DYNAMIC CONE PENETROMETER

5.1

California Bearing Ratio (CBR) Test

5.1.1

Introduction

5.1.1.1

General. The test is an empirical test which gives an indication of the shear strength of a soil. The great value of this test is that it is comparatively easy to perform and because of its wide use throughout the world, there is a vast amount of data to assist with the interpretation of results. The CBR test is essentially a laboratory test but in some instances the test is carried out on the soil in-situ.

5.1.1.2

Scope. The laboratory CBR test consists essentially of preparing a sample of soil in a cylindrical steel mould and then forcing a cylindrical steel plunger, of nominal diameter 50 mm, into the sample at a controlled rate, whilst measuring the force required to penetrate the sample. A pictorial view of the general test arrangement is shown in Figure 5.1.1. CBR values may vary from less than 1% on soft clays to over 150% on dense crushed rock samples. Preparation of remoulded samples for the CBR test can be made in several ways. However, commonly used methods are described here: (1) Static compression (2) Dynamic compaction by (a) using 2.5 or 4.5 kg rammer and (b) using vibrating hammer.

5.1.2.1

Material. The CBR test is carried out on material passing a 20mm test sieve. If soil contains particles larger than this the fraction retained on 20mm shall be removed and weighed before preparing the test sample. If this fraction is greater than 25% of the original sample the test is not applicable. The moisture content of the specimen or specimens can be adjusted as necessary following the procedure given in Chapter 4. The moisture content used is normally to the Optimum Moisture Content (OMC), but obviously this can be varied to suit particular requirements.

5.1.2.2

Mass of soil for test. When the density or air voids content of a compacted sample is specified the exact amount of soil required for the test can be calculated as described in a) or b) below. When a compactive effort is specified the mass of soil can only be estimated, as described in c) below. a) Dry density specification. The mass of soil m1 (in g), required to just fill the CBR mould of volume Vm (in cm3) is given by the equation

m1 =

Vm (100 + w ) ρ d 100

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where, w is the moisture content of the soil (in %); and pd is the specified dry density (in Mg/m3). b) Air voids specification. The dry density, ρ d, (in Mg/m3), corresponding to an air voids content of Va (in %) is given by the equation

Va 100 ρd = 1 w + ρ s 100 ρ w 1-

Where, Va is the air voids expressed as a percentage of the total volumes of soil ; 3 ρ s is the particle density (in Mg/m ); w is the soil moisture content (in %); 3 ρ w is the density of water (in Mg/m ), assumed equal to 1. The corresponding mass of soil to just fill the CBR mould is calculated from the equation in (a) above. c) Compactive effort specification. About 6kg of soil shall be prepared for each sample to be tested. The initial mass shall be measured to the nearest 5g so that the mass used for the test sample can be determined after compaction by difference, as a check. Note.

Preliminary trials may be necessary to determine the required mass more closely.

5.1.2.3

Undisturbed samples. This method is very useful for testing of fine-grained cohesive soils, but cannot be applied to non-cohesive materials or materials containing gravel or stones. Only the CBR moulds as described in 5.1.2.4(b) are suitable for undisturbed sampling.

5.1.2.4

Apparatus. The following apparatus is variously required to carry out the 2.5 kg, 4.5 kg and Vibrating hammer methods in Figure 5.1.2. a) Test sieves of aperture sizes 20 mm and 5 mm. b) A cylindrical, corrosion-resistant, metal mould, i.e. the CBR mould, having a nominal internal diameter of 152±0.5 mm. The mould shall be fitted with a detachable base-plate and a removable extension. The mould is shown in Figure 4.3.3. The internal faces shall be smooth, clean and dry before each use. c) A compression device (load press) for static compaction, (for 2.5 kg hammer). Horizontal platens shall be large enough to cover a 150mm diameter circle and capable of a vertical separation of not less than 300 mm. The device shall be capable of applying a force of at least 300 kN. d) Metal plugs, 152±0.5 mm in diameter and 50±1.0 mm thick, for static compaction of a soil specimen (for 2.5 kg hammer). A handle which may be screwed into the plugs makes removal easier after compaction. The essential dimensions are shown in Figure 5.1.3. Three plugs are required for 2.5 kg hammer.

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50± 1

e) A metal rammer, (for 4.5 kg hammer). This shall be either the 2.5 kg rammer or the 4.5 kg rammer, both as specified in Chapter 4, depending on the degree of compaction required. A mechanical compacting apparatus may be used provided that it also complies with the requirements of that document. f) An electric, vibrating hammer and tamper, as specified in Chapter 4 (for vibrating hammer). g) A steel rod, about 16mm in diameter and 600 mm long. h) A steel straightedge, e.g. a steel strip about 300 mm long, 25 mm wide and 3mm thick, with one beveled edge. i) A spatula. j) A balance, capable of weighing up to 25 kg readable to 5 g. k) Apparatus for moisture content determination, as described in Chapter 3. l) Filter papers, 150 mm in diameter, e.g. Whatman No. 1 or equivalent.

Screw thread ∅ 150±0.5

Figure 5.1.3 Plug for use with cylindrical mould in the CBR test (in mm). 5.1.2.5

Preparation of test sample using static compression 1. Preparation of mould a) Weigh the mould with baseplate attached to the nearest 5 g (m2). b) Measure the internal dimensions to 0.5 mm c) Attach the extension collar to the mould and cover the base-plate with a filter paper. d) Measure the depth of the collar as fitted, and the thickness of the spacer plug or plugs, to 0.1 mm. 2. Preparation procedure a) This procedure is for 2.5 kg hammer in Figure 5.1.2. b) Divide the prepared quantity of soil into three portions with a mass equal to within 50 g of each other and seal each portion in an airtight container until required for use. c) Place one portion in the mould and level the surface. Compact to 1/3 the height of the mould in the compression device using suitably marked steel spacer discs to obtain the required depth of sample (127/3 = 42 mm). The mould is then removed from the compression device and the second portion of the material is added. This is then compressed to give a total sample depth to 2/3 the height of the mould (i.e. 85 mm). Finally, the remainder of the sample is MAY 2001

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added and the mould is returned to the compression device until the finished sample is just level with the top of the mould. Care should be taken not to damage the press by attempting to crush the steel mould when the sample is level : always pay close attention to the load gauge. Except for some dense aggregates the force required for compaction should not be very large. d) On completion of compaction weigh the mould, soil and base-plate to the nearest 5 g (m3). e) Unless the sample is to be tested immediately, seal the sample (by screwing on the top plate if appropriate) to prevent loss of moisture. With clay soils or soils in which the air content is less than 5%, allow the sample to stand for at least 24 h before testing to enable excess pore pressures set up during compression to dissipate. 5.1.2.6

Preparation of sample using dynamic compaction 1. General. This method may be used if a static compression device is not available. If it is required to compact specimens to a density and moisture content other than Maximum Dry Density and Optimum Moisture Content, it is preferable to use static compaction, as with dynamic compaction these can only be achieved by trial and error. Note.

An alternative to compacting a single sample using a specified compaction method (see 5.1.2.6(3) below) and then carrying out a CBR test on it, is to carry out a CBR test on each of the specimens made up during a normal compaction test (in CBR moulds). This procedure gives a curve of varying CBR with moisture content/dry density, an example is shown in Figure 5.1.8 at the end of this document.

2. Preparation of mould. Follow the procedure given in 5.1.2.5(1) above, with the exception of 5.1.2.5(1)(d) . 3. Preparation procedure 3A.

Using compaction rammers a) This procedure is for 4.5 kg hammer in Figure 5.1.2 b) The procedures for use in the CBR mould are summarised in Table 5.1.1 below. Table 5.1.1 Dynamic compaction procedures for use in CBR mould Test Method

2.5 kg rammer method Intermediate compaction * 4.5 kg rammer method Vibrating hammer method

Mass of Rammer (Kg) 2.5 4.5 4.5 **

Height of Drop mm

Number of Layers

300 450 450 -

3 5 5 3

Blows per Layer 62 30 62 -

* Recommended procedure to obtain a specimen density between that achieved by using the 2.5 kg and 4.5 kg rammer methods. ** See Chapter 4 for specification of vibrating hammer c) Having decided which compaction method to use from Table 5.1.2, divide the prepared quantity of soil into three (or five) portions with a mass equal to

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d) e)

f) g) h) i) 3B.

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within 50 g of each other and seal each portion into an airtight container until required for use. Stand the mould assembly on a solid base, e.g. a concrete floor. Place the first portion of soil into the mould and compact it with the required number of blows of the appropriate rammer. After compaction the layer should occupy about or a little more than one-third (or one-fifth) of the height of the mould. Ensure that the blows are evenly distributed over the surface of the soil. Repeat the process in (e) above using the other two (or four) portions of soil, so that the final of the soil surface is not more that 6mm above the top of the mould body. Remove the collar, trim the soil flush with the top of the mould with a scraper, and check with the steel straightedge that the surface is level. Weigh the mould, soil and base-plate to the nearest 5 g (m3) Seal and store the sample as described in 5.1.2.5(2)(e)

Using a vibrating hammer a) This procedure is for Vibrating Hammer in Figure 5.1.2. b) Divide the prepared quantity of soil into three portions with a mass equal to within 50 g of each other and seal each portion in an airtight container until required for use, to prevent loss of moisture. c) Stand the mould assembly on a solid base, e.g. a concrete floor or plinth. d) Please the first portion of soil into the mould and compact it using the vibrating hammer fitted with the circular steel tamper. Compact for a period of 60±2 s, applying a total downward force on the sample of between 300 N and 400 N. The compacted thickness of the layer shall be about equal to or a little greater than one-third of the height of the mould. e) Repeat 3B(d) of 5.1.2.6(3) above using the other two portions of soil in turn, so that the final level of the soil surface is not more than 6 mm above the top of the mould. f) Remove the collar and trim the soil flush with the top of the mould with the scraper, checking with the steel straightedge. g) Weigh the mould, soil and base-plate to the nearest 5 g (m3). h) Seal and store the sample as described in 5.1.2.5(2)(e) above.

3C.

Preparation of undisturbed sample. Take an undisturbed sample from natural soil or from compacted fill by the procedure described in Chapter 2 using a weighed CBR mould fitted with a cutting shoe. After removing the cutting shoe from the mould, cut and trim the ends of the sample so that they are flush with the ends of the mould body. Fill any cavities with fine soil, well pressed in. Attach the base-plate and weigh the sample in the mould to the nearest 5 g (m3). Unless the sample is to be tested immediately, seal the exposed face with a plate or an impervious sheet to prevent loss of moisture.

5.1.2.7

Soaking 1.

General. The test sample as prepared will normally represent the material shortly after compaction in the road works. However, if the material is likely to be subjected to an increase in moisture content, either from rainfall, ground-water or ingress through the surfacing it is probable that its strength and, hence, CBR, will drop as the moisture content increases. In an attempt to estimate these effects CBR samples can be soaked in water for 4 days prior to penetration testing.

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Some soils, especially heavy clays, are likely to swell during soaking and excessive swelling may indicate that the soil is unsuitable for use as a sub-grade; it is, therefore, important to record the swell during soaking. 2.

Apparatus. The following items are required in addition to the apparatus listed in 5.1.2.4 above. a) A perforated base-plate, fitted to the CBR mould in place of the normal baseplate (see Figure 5.1.4). b) A perforated swell plate, with an adjustable stem to provide a seating for the stem of a dial gauge (see Figure 5.1.4). c) Tripod, mounting to support the dial gauge. A suitable assembly is shown in Figure 5.1.4. d) A dial gauge, having a travel of 25 mm and reading to 0.01 mm. e) A soaking tank, large enough to allow the CBR mould with base-plate to be submerged, preferably supported on an open mesh platform. f) Annular surcharge discs, each having a mass known to ±50 g, an internal diameter of 52-54 mm and an external diameter of 145-150 mm. As an alternative, half-circular segments may be used. For practical purposes, the latter are often easier to use. g) Petroleum jelly.

Dial Dialgauge gauge Dial gauge mounting frame Adjustable stem

Surcharge Surcharge rings rings Extension collar Extension collar

Looking nut

Sooking tank

Perforated swell plate CBR mould body Sample

Perforated baseplate Open mesh platform

Figure 5.1.4 3.

Apparatus for measuring the swelling of a sample during soaking for the CBR Test. Test procedure a) Remove the base-plate from the mould and replace it with the perforated base-plate. b) Fit the collar to the other end of the mould, packing the screw threads with petroleum jelly to obtain a watertight joint. c) Place the mould assembly in the empty soaking tank. Place a filter paper on top of the sample, followed by the perforated swell plate. Fit the required number of annular surcharge discs around the stem on the perforated plate. Note. One surcharge disc of 2 kg simulates the effect of approximately 70 mm of superimposed construction on the sub-grade being tested. However, the exact amount of surcharge is not critical. Surcharge discs of any convenient multiples may be used.

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d) Mount the dial gauge support on top of the extension collar, secure the dial gauge in place and adjust the stem on the perforated plate to give a convenient zero reading (see Figure 5.1.4) e) The apparatus is then placed in a tank of clean water and the sample is kept submerged for 4 days and the dial gauge is read every 24 hours. The difference between the initial and final dial gauge reading gives the swell, S. The % swell is given by :

% Swell =

S S x 100 = % 127.0 1.27

Where, S is in mm. f)

On completion of soaking surplus water is wiped from the sample which is reweighed. The difference in weights before and after soaking is the weight of water absorbed, Ww. The % of water absorbed is give by :

% Water absorbed =

M W (100 + m 2 ) % Wm

Where Wm is original weight of sample and m2 is original moisture content. g) Take off the dial gauge and its support, remove the mould assembly from the immersion tank and allow the sample to drain for 15 min. If the tank is fitted with a mesh platform leave the mould there to drain after emptying the tank. If water remains on the top of the sample after draining it should be carefully siphoned off. h) Remove the surcharge discs, perforated plate and extension collar. remove the perforated base-plate and refit the original base-plate. i) Weigh the sample with mould and base-plate to the nearest 5 g if the density after soaking is required. j) If the sample has swollen, trim it level with the end of the mould and reweigh. k) The sample is then ready for test in the soaked condition. 5.1.2.8

Penetration test procedure 1.

Apparatus. A general arrangement of apparatus is shown in Figure 5.1.5. The apparatus consists of: a) A cylindrical metal plunger, the lower end of which shall be of hardened steel and have a nominal cross-sectional area of 1935 mm2, corresponding to a specified diameter of 49.65 ±0.10 mm. A convenient size would be approximately 250 mm long. b) A machine for applying the test force through the plunger, having a means for applying the force at a controlled rate. The machine shall be capable of applying at least 45 kN at a rate of penetration of the plunger of 1 mm/min to within ±0.2 mm/min. c) A calibrated force-measuring device, usually a load ring or proving ring. The device shall be supported by the cross-head of the compression machine so as to prevent its own weight being transferred to the test specimen (see Figure 5.1.1) Note. At least three force-measuring devices should be available, having the following ranges : 0 to 2 kN readable to 2 N for values of CBR up to 8% 0 to 10 kN readable to 10 N for values of CBR from 8% to 40% MAY 2001

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0 to 50 kN readable to 50 N for values of CBR above 40% d) A means of measuring the penetration of the plunger into the specimen, to within 0.01 mm. A dial gauge with 25 mm travel, reading to 0.01 mm and fitted to a bracket attached to the plunger is suitable. A general arrangement is shown in Figure 5.1.5. A dial gauge with a chisel edge to the stem anvil is easier to use than one with a pointed stem anvil. Note. A dial gauge indicating 1 mm/revolution is convenient since the specified rate of penetration of 1 mm/min can be controlled conveniently by keeping the hand of the dial gauge in step with the second hand of a clock or watch. This is particularly convenient when using a non-motorised loading frame. e) A stop-clock or stopwatch readable to 1 s. f) The CBR mould as described in Chapter 4. g) Surcharge discs as described in 5.1.2.7(2). 2.

Procedure a) Place the mould with base-plate containing the sample, with the top face of the sample exposed, centrally on the lower platen of the testing machine. b) Place the appropriate annular surcharge discs on top of the sample. c) Fit into place the cylindrical plunger and force-measuring device assembly with the face of the plunger resting on the surface of the sample. Make sure that the proving ring dial gauge is properly adjusted, i.e. that there is no daylight between the bottom of the stem and the proving ring anvil. Note. It may be necessary to move the crosshead up to allow the plunger to be inserted through the surcharge discs and the stabilizer bar (if fitted). Be careful to lower the cross-head again in order to make sure that the lower platen and penetration dial gauge have enough travel left before starting the test. This must be level before starting the penetration test. d) Apply a seating force to the plunger, depending on the expected CBR value, as follows: For CBR value up to 5% apply 10 kN For CBR value from 5% to 30%, apply 50 kN For CBR value up to 30% apply 250 kN Note. The number of proving ring dial gauge divisions corresponding to the required seating load can be found from the calibration chart for that proving ring. It is helpful to have the N/division value displayed on each load ring. It is extremely important to ensure that the maximum allowable dial gauge reading for the proving ring is never exceeded. e) Record the reading of the force-measuring device as the initial zero reading (because the seating force is not taken into account during the test) or reset the force measuring to read zero. f) Secure the penetration dial gauge in position. Record its initial zero reading, or reset it to read zero. Make sure that all connections between plunger, crosshead, proving ring and penetration dial gauge assembly are tight. g) Start the test so that the plunger penetrates the sample at the uniform rate of 1±0.2 mm/min, and at the same instant start the timer. MAY 2001

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h) Record readings of the force gauge at intervals of penetration of 0.25 mm to a total penetration not exceeding 7.5 mm (see Form 5.1.2). Note. If the operator plots the force penetration curve as the test is being carried out, the test can be terminated when the indicated CBR value falls below its maximum value. Thus if the CBR at 2.5 mm were seen to be 6% but by 3.5 mm penetration it could be seen to have fallen below 6%, the test could be stopped and the result reported as: CBR at 2.5 mm penetration = 6% CBR at 5.0 mm penetration =