DETERMINATION OF WATER CONTENT OF SOIL
A) By oven dry method
Theory: The water content (w) of a soil sample is equal to the mass of water divided by the mass of solids.
Where M1=mass of empty container with lid,
M2= mass of the container with wet soil and lid
M3= mass of the container with dry soil and lid.
1. Thermostatically controlled oven, maintained at a temperature of 1100 ± 50C.
2. Weighing balance with accuracy of 0.04% of the mass of the soil taken
3. Desiccator, with any suitable desiccating agent
4. Airtight container made of non-corrodible material with lid
The soil specimen should be representative of the soil mass. The quantity of the specimen taken would depend upon the gradation and the maximum size of the particles. For more than 90% of the particles passing through 425 micron IS sieve, the minimum quantity is 25g.
1. Clean the container, dry it and weight it with lid (M1).
2. Take the required quantity of the wet specimen in the container and close it with lid. Take the mass (M2)
3. Place the container with its lid removed in the oven till mass becomes constant (normally for 24 hours).
4. When the soil has dried, remove the container from the oven using tongs. Replace the lid on the container. Cool it in a desiccator.
5. Find the mass (M3) of the container with lid and dry soil sample.
Observations and Calculations:
Data sheet for water content by oven-drying method
Observations an Calculations
Mass of empty container (M1)
Mass of container + soil (M2)
Mass of container + dry soil (M3)
Mass of water Mw= M2 – M3
Mass of solids, Ms= M3 – M1
Water content= (5)/(6)x100
Water content of the sample = ______%.
B) By Pycnometer Method
A Pycnometer is a glass jar of about 1 liter capacity, fitted with a brass conical cap by means of a screw type cover. The cap has a small hole of about 6mm diameter at its apex.
The water content (w) of the sample is obtained as
Where M1=mass of empty Pycnometer,
M2= mass of the Pycnometer with wet soil
M3= mass of the Pycnometer and soil, filled with water,
M4 = mass of Pycnometer filled with water only.
G= Specific gravity of solids.
2. Weighing balance with an accuracy of 1.0g.
3. Glass rod
1. Wash and clean Pycnometer and dry it.
2. Determine the mass of Pycnometer with brass cap and washer (M1) accurate to 1.0g.
3. Place about 200 to 400g of wet soil specimen in the Pycnometer wand weigh it with its cap and washer (M2).
4. Fill water in the Pycnometer containing the wet soil specimen to about half its height.
5. Mix the contents thoroughly with a glass road. Add more water and stir it. Fill the Pycnometer with water, flush with the hole in the conical cap.
6. Dry the Pycnometer from outside and take its mass (M3).
7. Empty the Pycnometer. Clean it thoroughly. Fill it with water, flush with the hole in the conical cap and weigh (M4)
Observations and calculations:
See the data sheet.
Data sheet for water content by Pycnometer method
Observations an Calculations
Mass of empty pycnometer (M1)
Mass of pycnometer + wet soil (M2)
Mass of Pycnometer soil, filled with water (M3)
Mass of Pycnometer filled with water only (M4)
M2 – M1
M3 – M4
(G – 1) / G
w (using above formula)
Water content of the sample = _______%.