Water Content in Soil

Experiment No. 1 WATER CONTENT IN SOIL

Scope

This method of test is intended for determining the hygroscopic water content of soils by oven drying to constant weight. Apparatus

1. 2. 3. 4. 5. 6.

Container Container (e.g., (e.g., tin tin or aluminum aluminum with with lids) lids) Balance, Balance, sensi sensitive tive to to 0.1 gram Oven with temperature temperature control control Dessic Dessicator  ator  Tongs or suitabl suitablee holder holder for moving moving and handling handling hot containers containers Sieve Sieve No. 10, 10, No. No. 4, 3/8” 3/8” siev sievee

Test Specimen

The minimum mass of moist material selected to be representative of the total sample shall be in accordance with the following: Maximum Particle Size (100% passing)

Standard Sieve Size

Recommended Minimum Mass of  Moist Test Specimen for Water  Content Content Reported Reported to +0.1 % 2 mm or less No . 1 0 20 g * 4.75 mm No. 4 20 g * 3 9.5 mm /8-in. 50 g 19.0 mm ¾-in. 250 g 37.5 mm 1 ½-in. 1 kg 75.0 mm 3-in. 5 kg T o be representative not less than 20 g shall be used. Note  – * To Procedure

1. Weigh Weigh the clean and dry specimen specimen container container (and (and its lid, lid, if used) and record record as Wc. 2. Select a representati representative ve sample of the soil, soil, place in the container container and cover immediatel immediately. y. Weigh and record as W1. 3. Open the the container and dry in in the oven to constant constant weight at a temperature temperature of 110 + 5 oC. The drying time will depend on the kind of soil and size of sample. A 25-gram sandy material material can be dried at about 2 hours, hours, while while the same weight of a plastic, fine-grain fine-grained ed soil will require at least 4 hours to dry at constant weight. 4. Remove Remove the container container from the the oven and cool to room temperat temperature ure.. Weigh and record record as W2. A sample may be cooled at room humidity within an hour after it has been removed from the oven. If it cannot be weighed within this period, it should be placed in a dessicator to cool to

room temperature. This is especially significant if the soil is very plastic and the room humidity is high. Weighing hot container is not advisable as it affects the accuracy of results. Calculation

Equation: w



W 1



 W 2 W 2 W  

W c







W c





100%

c

where: w

water content of soil (expressed as a percentage)  weight of container plus moist soil (grams)



W 1 W 2



weight of container plus oven-dry soil (grams)

W c



weight of container (grams)

Questions 1. Is the moisture content of soil expressed as a percentage of the weight or as a percentage of  the volume of the soil? 2. What are the six categories of soil types identified in the ASTM classification system? 3. For which soil type is surface forces important? Why? 4. Can you remove the adsorbed water by oven drying at 105 C? Explain. 5. When a soil sample is dried in an oven during the moisture content determination test, what standard is used to determine that the sample is completely dry? 6. Why is it not recommended to leave an oven-dried sample in the open air for a long time  before measuring its dry weight? 7. Excluding oven drying, are there other methods to determine the water content of soils? 8. Soil must be baked in an oven to drive off the moisture during a moisture content determination test. Is there an approved ASTM method for using a microwave oven for this test? 9. Is it possible to measure the water content of sands? 10. Why do we use a fixed temperature range to dry soils? What is the effect on soils of  microwave drying? 11. What is the function of the container lid and dessicator when determining the water  content of soil? °

PRELIMINARY DATA SHEET

 Name: ___________________________________ Group No._____________________  Course/Section: ____________________________ Date: _________________________ 

Experiment No. 1 WATER CONTENT IN SOIL

Sieve No.

#4

Trial No.

1

# 10 2

1

2

Weight of wet soil + container (grams) Weight of oven-dry soil + container (grams) Weight of wet soil (grams) Weight of oven-dry soil (grams) Weight of container (grams) Moisture loss (grams) Water content,

w

(%)

Average water content (%) Average water content (%)

 ___________________________ Student’s Signature

___________________________  Instructor’s Signature

FINAL DATA SHEET

 Name: ___________________________________ Group No._____________________  Course/Section: ___________________________ Date: _________________________ 

Experiment No. 1 WATER CONTENT IN SOIL

Sieve No.

#4

Trial No.

1

Weight of wet soil + container (grams) Weight of oven-dry soil + container (grams) Weight of wet soil (grams) Weight of oven-dry soil (grams) Weight of container (grams) Moisture loss (grams) Water content,

w

(%)

Average water content (%) Average water content (%)

 ___________________________  Student’s Signature

# 10 2

1

2