Determination of water content

SOIL MECHANICS LAB

1. DETERMINATION OF WATER CONTENT EXPERIMENT NO 1 SOIL MECHANICS LABORATORY CE PC 594

2. DEFINITION OF WATER CONTENT WATER CONTENT is the percentage of ratio between weight of water and the weight of solid. Water content is designated as w% ×100%  

3. TESTS TO DETERMINE WATER CONTENT OVEN dry method Sand bath method Alcohol method Calcium Carbide method Radiation method Infrared torsional balance method Pycnometer method NOTE: Out of them 1 st , 4 th and 7 th number of tests generally used to determine water content

4. OVEN DRY METHOD Most accurate method used for the determination of water content in laboratory Procedure: This method comprises of placing of moist soil sample of soil in an empty container of unknown weight (W 1 ). Container with moist sample is being weight W 2 and placed in temperature controlled oven for drying. W 1 W 2

5. OVEN DRY METHOD Procedure: Temperature – 105° to 110 ° C (for inorganic soil) Time- 4 hours (sandy soil) 12 to 16 hours (silt and clay) Temperature – 60° C (for organic soil ) For soil having high gypsum (CaSO 4 , 2H 2 0) Temperature- 80 ° C (to avoid loss of water of crystallization) W 1 W 2

6. OVEN DRY METHOD Procedure: After removing the container from oven, weight measured as W 3 W 1 W 2 W 3 Container + Moist soil Empty Container Container + Dry soil 105° to 110 ° C Water content, ×100 % Weight of water, = W 2 -W 3 ; Weight of solid, = W 3 -W 1  

7. PYCNOMETER METHOD It is a quick method in which result is obtained between 10 to 20 minutes. This method is used for only those soil whose specific gravity is known. Procedure: Pycnometer is 900 ml flask having conical brass top having 6mm diameter hole at its center. 6mm 900 ml

8. PYCNOMETER METHOD Procedure: Weight of empty pycnometer is observed initially W 1 200-400 gm moist sample W 2 with pycnometer Empty volume of pycnometer is filled with water along with simultaneous removal of air present in soil either by stirring or by use of vacuum at the top of pycnometer Pycnometer is being again weight after filling the empty volume with water W 3 Pycnometer is then completely emptied and again filled with water after cleaning properly (W 4 )

9. PYCNOMETER METHOD W 1 (a) W 2 (b) W 3 (c) W 4 (d) Weight of water (W W ) Weight of moist soil in pycnometer = W 2 -W 1 Let’s say weight of solid in (b) = W d Weight of water in the moist soil sample (W W ) = (W 2 -W 1 ) - W d Weight of Solid ( W d ) = ; = ; G= Volume of Solid ( V d ) = = Volume of water equivalent to volume of solid  

10. PYCNOMETER METHOD W 1 (a) W 2 (b) W 3 (c) W 4 (d) Equivalent weight of water = × = If the solids from (c) are replaced with water of equivalent weight We get the weight W 4 from (d) W 4 =W 3 -W d + W 4 =W 3 -W d (1- )   W 3 - W 4 = W d ( ) W d = ( W 3 - W 4 )( ) ×100 % w = ×100% w = [ ( ) ( ) -1] × 100%  

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