Slump Test

SLUMP TEST Introduction The slump test is perhaps the most widely used because of the simplicity of the apparatus required and the test procedure. The slump test indicates the behavior of a compacted concrete cone under the action of gravitational forces. The slump test is a practical means of measuring the workability. Changes in the value of slump obtained during a job may indicate changes in materials, in the water content or in the proportions of the mix, so it is useful in controlling the quality of the concrete produced. The test carried out with a mould called the slump cone. The slump cone is placed on a horizontal and non-absorbent surface and filled in three equal layers of fresh concrete, each layer being tamped 25 times with a standard tamping rod. The top layer is struck off level and the mould is lifted vertically without disturbing the concrete cone. The subsidence of concrete in millimeters is termed the slump. After the test, slumps evenly all around is called true slump. In the case of very lean concrete, one half of the cone may slide down the other which called a shear slump or it may collapse in case of very wet concretes. The slump test is essentially a measure of consistency or the wetness of the mix. Objective •

To find a workability of the specimen.

•

To find a consistence of the specimen.

Apparatus 1. Tamping rod - straight bar of circular cross section, 16 mm diameter, 600mm long with both end hemispherical. 2. Inspection Scale - Machine steel, 0-10 cm slump measurement, 1 cm increment. 3. Base Plate - Steel sheet, carrying handle, 600 x 600 x 5 mm 4. Sampling tray - 1.2 x 1.2 x 50mm deep made from minimum 1.6mm thick non-corrodible metal. 5. Scoop - Cast alumunium approximately 100mm wide. 6. Trowel - Pointed type 7. Brush - Steel wire 8. Specimen 9. Cone - Made of metal not readily attacked by cement paste with the following internal dimensions: • diameter of base 200 ± 2mm • diameter of top: 100 ± 2mm • height 300 ± 2mm

Cone

Tamping rod

Procedure 1. Filled mold in three equal layers. 2. Each layer is rodded 25 times to settle the concrete, before the next layer is added. 3. Full mold is ready to be pulled off to measure slump. 4. Remove the cone from the concrete by raising it vertically, slowly and carefully, in 5 to 10 seconds. 5. Partial mix being revealed by removal of mold. 6. Immediately after the cone is removed, measure the slump to the nearest 5mm by using the rule to determine the height of the cone and of the highest point of the specimen being tested

Result Quantities

Cement (kg)

Water(kg or litres)

Fine aggregate (kg)

Coarse aggregate (kg) – 20 mm size

Per trial mix of 0.0135 m³

4.8

2.8

9.4

15.4

The result of slump test by using the above amount of cement, water, fine aggregate and coarse aggregate was 10.5 cm collapse slump.

Discussion We must reduce water content in the concrete for avoid shear failure. However, the slump test has been found to be useful in ensuring the uniformity among different batches of supposedly similar concrete under field conditions.

Conclusion Slump result was 105mm but shear failure which mean collapse. Hence the concrete is non-acceptable. This happened because there a lot of water content in the concrete and look wetly during the test. It seems that it is because of one of our member mistake, which put the water, more than 2.8 liters. Water content in the concrete, mean higher the workability but lower the strength. If the cement content higher, the workability also become higher. The good mix particles, particle shape and size are cubical or rounded, the workability also become high. We concluded that our specimen is a high workability but shear failure which mean lateral collapse.

COMPRESSIVE STRENGTH OF CONCRETE CORES Introduction There are some methods to assess the quality of hardened concrete from properties of concrete at early age. The compressive strength testing technique is one of the available methods to evaluate the properties. It is a destructive test on sample and a easy technique compared with some other test. The accuracy and prediction of this technique has been satisfactory. Objectives The aim of this work was to establish a general and direct relationship between the compressive strength and its property behaviour regardless of the differences in mix proportions and age of concretes. This method describes the procedure for making and curing compression test

specimens from fresh concrete and for determining the compressive

strength of the specimens. Apparatus 1) Molds – 150mm X 150mm X 150mm. Molds shall be water tight and the base plate or bottom 2) Tamping Rod - a round straight steel rod 16 mm in diameter and 600 mm in length. 3) Sampling Equipment - scoop or shovel, trowel, 4) Curing Equipment - a moist storage cabinet or room capable of maintaining specimens at a temperature within ± 1 degrees of 23 ◦C 5) Compression testing machine complying with BS 1881: Part 115.

Sampling Equipment

Compression testing machine

Molds – 150mm X 150mm X 150mm

Procedure 1) Place the mold on a firm, level surface. 2) Form the test sample by placing concrete in the mold in three layers of approximately equal volume. 3) Move the scoop around the top edge of the mold to ensure a symmetrical distribution of the concrete within the mold. 4) Rod each layer with 25 strokes of the tamping rod. For layers 2 and 3, the rod shall penetrate about 25 mm into the underlying layer. 5) Distribute the strokes uniformly over the cross-section of the mold. 6) Close the voids left by the tamping rod by lightly tapping the sides of the mold. 7) After the top layer has been rodded, the surface will be struck off with a trowel and covered with saran wrap to prevent evaporation. 8) Store the specimen undisturbed for 24 hours in such a way as to prevent moisture loss and to maintain the specimen within a temperature range of 15oC to 27oC. 9) Remove the test specimen from the mold between 20 and 48 hours and transfer carefully to the place of curing and testing. If molds are being shipped it is permissible to leave specimen in cardboard mold during transit.

10)Place the specimen in the water bath and store for the curing period designated in the contract. 11)After the specimen has been cured for the proper length of time in the water bath remove and cap. The capping compound will be prepared and applied to form a plane uniform surface at right angles to the axis of the cylinder. 12) Allow the sulphur capping compound to harden at least two hours before applying the load. Specimens will be kept moist until time of test. 13)Place the specimen in the machine and slowly bring the blocks to bear on the specimen without shock until failure occurs. 14)Operate the machine at a constant rate within the range of 0.140 to 0.350 MPa per second.

Cracks due to compression failure

Load being applied

Results Date of preparation: 28 July 2007 Test specimen preparation Cement

= 17.8 kg

Water

= 10.5 kg Fine aggregate

= 34.9kg

Coarse aggregate = 56.9 kg Target Design grade of 25

Date of testing: 30 August 2007 Sample No.

Core

Loading

Diameter

K15/ 15

(mm)

Reading 1

Reading 2

Average

150

(KN) 870

(KN) 870

(KN) 870

*Detail test results on consolidation test can be referred in appendices. So the compressive strength is 870 000 N/ ( 150mm x 150mm) = 38.7 N/mm2 And it is found that the type of failure is very satisfactory. Estimated in-situ cube strength = D x measured compressive strength of core 1.5 + (1/ n)

Discussion It can be implied from the experiments or can be observed during mixing, that the only (or at least the predominant) factor causing variation of workability is variation of water content, then a simple relationship between workability and strength might be expected. Whether or not the required condition holds is indicated by whether or not there is a positive correlation between the water/cement ratio. It shows from the results that there is no positive correlation between cement and water ratio and it is not the predominant cause of variation in workability and therefore, no correlation between strength and any measure of workability is to be expected; in fact none exists.

Conclusion In general and can be concluded that there is no direct relationship between workability of the fresh concrete and the strength of the hardened concrete. The reason is that strength is determined primarily by the water/cement ratio provided the concrete is properly compacted, whereas workability is affected by many other factors as well. It may also be concluded that the condition exist that water content variation is the predominant cause of variation of workability, strength may be also to be expected to correlate with the results of a single- point workability test and the design grade of 25 is over-achieved to grade 38.

COMPACTING FACTOR FOR CONCRETE CORE Introduction The compacting-factor test was devised because they recognised the importance of achieving full compaction in concrete, and therefore the importance of being able to measure the ability of the material to be compacted. It is always argued that the work in placing concrete is composed of that lost in shock and the useful work which is expended in overcoming the internal friction of the concrete itself and in overcoming the friction against the mould and the reinforcements. Of these, it is only the loss against internal friction that is characteristic of the concrete alone and it is this that they used as the basis for a definition of workability and they set out to measure. The standard quantity of work is provided simply by allowing the concrete to fall under gravity through a standard distance. The apparatus consists simply of two (2) conical hoppers and a cylindrical mould mounted vertically one above the other, the capacity of the top hopper being greater that that of the lower, which in turn is greater that that of the cylinder. The internal surfaces are smooth to minimise surface friction.

Apparatus 1.) Compacting factor apparatus consisting of two conical hoppers mounted above a cylinder. The hopper and cylinder shall be rigid construction made of metal. 2.) Steel floats, two (2) plasterer’s steel floats 3.) Sampling tray of 1.2m x 1.2m x 50 mm deep made from non-corrodible metal. 4.) Square mouthed shovel 5.) Tamping rod. 6.) Scales or balance of weighing up to 25 kg to an accuracy of 10 g or better. 7.) Compacting bar or vibrating hammer or table. Procedure Sampling 1.)

The sample of fresh concrete are obtained. The determination of compacting factor is commenced as soon as possible after sampling.

Preparing the sample for test 2.)

The sample is emptied from the container onto the sampling tray.

3.)

The sample are thoroughly mixed by shovelling it to form a cone on the sampling tray and turning this over with the shovel to form a new cone, the operation are carried out three (3) times.

4.)

The third cone was flatten by repeatedly vertical insertion of the shovel across the apex of the cone, lifting the shovel clear of the concrete after each insertion.

Testing procedure 5.)

The internal surfaces of the hoppers and cylinder are smooth, clean and damp is ensured. The frame are placed in a position free from vibration or shock in such a manner that it is stable with axes of the hoppers and the cylinder all lying on the same vertical line.

6.)

The sample of concrete are gently placed in the upper hopper using the scoop until the hopper is filled to the level of the rim. The excess concrete was cut off by holding a float in each hands with the plane of the blades horizontal.

7.)

The partially compacted concrete are removed from the cylinder and re-fill it with concrete from the same sample in such a way as to remove as much entrapped air as possible.

8.)

After the top layer has been compacted, smooth it level with the top of the cylinder, using the plasterer’s float and wipe clean the outside of the cylinder.

Compacting bar compaction 9.)

When compacting each layer with compacting bar, the strokes must be distributed of the compacting bar in a uniform manner over the cross-section of the cylinder and ensure that the compacting bar does not penetrate significantly any previous layer nor forcibly stroke the bottom of the cylinder when compacting the first layer.

10.)

The number of strokes per layer required to produce full compaction will depend upon the consistence of the concrete but in no case shall the concrete be subjected to fewer than 30 strokes per layer and the number of strokes are recorded.

Vibration compaction 11.)

When compaction with vibrator by means of the vibrating table. The duration of vibration depend upon the workability of the concrete and the effectiveness of the vibrator and vibratrion ceased as soon as the surface of the concrete becomes relatively smooth and has a glazed appearance. The duration of vibration are recorded.

Results

Date of testing: 28 July 2005 Partially compacted concrete, mp = 13.42 kg Fully compacted concrete, mf

= 14.97kg

Compaction factor = 13.42 x 100 = 89.64 % 14.97 *Detail test results on compacting factor can be referred in appendices.

Discussion

It is shown that the amount of energy imparted to the concrete in the compacting-factor test is much less that that used in compacting concrete by vibration. Although it is not strictly in accord with the requirements of the standard, the mass of fully compacted concrete may be found by compacting the partially compacted material using an internal vibrator, or poker and adding further concrete. We had noticed that by doing this method, a good estimate of the compacting factor maybe made by noting the drop in level of the partially compacted concrete as it is vibrated and further compacted.

Conclusion

It can be concluded that the test suffered from the disadvantage that cohesive concrete tends to stick in the hopper and must be encouraged to fall by pushing a rod through it. This is particularly so for air-entrained concrete. This method was found that it was impractical to measure that the work required to produce a given degree of compaction, so it was developed in which the inverse quantity, the degree of compaction produced by a given amount of work is measure instead.

DENSITY Introduction The principal properties of hardened concrete which are of practical importance are those concerning its strength, stress-strain characteristics, shrinkage and creep deformation, and response to temperature variation, permeability and durability. Of these, the strength of concrete assumes a greater significance because the strength is related to the structure of hardened cement paste and gives an overall picture of the quality of concrete. The strength of concrete at a given age under given curing conditions is assumed to depend mainly on water-cement ratio and degree of compaction. Objective •

To find the density of the specimen.

Scope •

To determination of compressive strength of concrete, both in the

laboratory and in the field. Apparatus •

Weighing machine

•

Vernier clamp

Procedure 1. Weigh the specimen cube and record the reading 2. Measure the length, width and thickness of the specimen cube and record the reading 3. Calculate the volume of the cube by multiplying the value of length with width and thickness. 4. Calculate the density by dividing the weight value over volume of cube Result Cube Length Mark

Averag

(L)(mm) e Length

Width Average

Height Averag

Volume

Weigh

* Density

(mm)

(mm)

e

(V)

t (W)

P=W/V

Height

LxWxH

(g)

(kg/m³)

(H)

(mm³)

Width (W)(mm)

(L)(mm)

(mm) AM1

AM2

AM3

152 151.3 151.6 151.3 151.4 151 150.7 150.6 150 150.1 150 150

151.55

150.925

150.025

Conclusion

150.4 150.6 150.875 151.1 151.4 151 150.6 150.625 150.5 150.4 151.7 151.5 152.2 152 153.6

149.5 151.3 151 149.2 151.2 151.1 150.8 150.4 151.1 151.3 151 151.6

8400 150.25

3,435,482 8.4kg

2445.071

150.875

3,429,853 8420g

2454.92

8.42kg 151.25

3,453,613 8460g 8.46kg

2449.61

•

The density for the three cubes marked AM1, AM2 and AM3 are exceeding the value for density in the designed mix which was 2500kg/m³.

•

It means during preparation of these cubes, the concrete were well compacted. As a result the cubes have less air voids and more dense.

•

The density for the three cubes of around 2445 to 2455 kg/m³ shows that this type of concrete can be considered as normal concrete.

•

It is suitable for normal concreting work.

References •

www.pearcereadymix.com/slump.html

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www.logicsphere.com/products/firstmix/hlp/html/work5xd0.htm

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www.tpub.com/content/engineering/ 14069/css/14069_550.htm

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civil.engr.siu.edu/330lab/Slump test.htm

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tecnotest.it/Products/Concrete/slump_test_equipment_description.htm

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www.umeciv.maine.edu/cie111/concrete/slump.htm

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www.mbt.co.id/equipment/co-370.html

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www.tpub.com/builder2n3/74.htm

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www.logicsphere.com/products/firstmix/hlp/html/work0ois.htm

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tecnotest.it/Products/.../compacting_factor_apparatus_description.htm

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ASTM Method C873

•

CAN3-A23.2-M77