This document describes several methods for determining the water content of soils in a soil mechanics laboratory experiment. The most accurate method is the oven-dry method, which involves weighing a moist soil sample, drying it in an oven at 105-110°C, and then reweighing to find the lost water weight. The pycnometer method is a quicker alternative that can be used when the soil's specific gravity is known. It involves filling a flask containing a moist soil sample with water to displace the air, then calculating the water content based on the change in weight and soil specific gravity. Up to seven different tests are described for measuring water content, with the oven-dry, calcium carbide, and pycnometer methods generally

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

2. WATER CONTENT is the percentage of ratio between
weight of water and the weight of solid.
Water content is designated as w%
 𝑤 =
𝑊𝑊
𝑊𝑆
×100%

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

4. • Most accurate method used for the determination of
water content in laboratory
Procedure:
o This method comprises of placing of moist soil
sample of soil in an empty container of
unknown weight (W1).
o Container with moist sample is being weight
W2 and placed in temperature controlled oven
for drying.
W1
W2

5. 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 (CaSO4, 2H20)
 Temperature- 80° C (to avoid loss of water of
crystallization)
W1
W2

6. Procedure:
o After removing the container from oven, weight measured as W3
W1 W2 W3
Container +
Moist soil
Empty
Container
Container +
Dry soil
105° to
110 ° C
Water content, 𝑤 =
𝑊𝑊
𝑊𝑆
×100%
Weight of water, 𝑊𝑊 = W2-W3 ; Weight of solid, 𝑊𝑆= W3-W1

7. • 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:
o Pycnometer is 900 ml flask having conical
brass top having 6mm diameter hole at its
center.
6mm
900 ml

8. Procedure:
o Weight of empty pycnometer is observed initially W1
o 200-400 gm moist sample W2 with pycnometer
o 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
o Pycnometer is being again weight after filling the empty volume with
water W3
o Pycnometer is then completely emptied and again filled with water after
cleaning properly (W4 )

9. W1
(a)
W2
(b)
W3
(c)
W4
(d)
Weight of water (WW)
 Weight of moist soil in pycnometer
= W2-W1
 Let’s say weight of solid in (b) = Wd
 Weight of water in the moist soil
sample (WW) = (W2-W1) -Wd
Weight of Solid (Wd)
𝛾𝑆=
𝑊𝑑
𝑉
; 𝛾𝑑=
𝑊𝑑
𝑉𝑑
; G=
𝛾𝑆
𝛾𝑤
Volume of Solid (Vd) =
𝑊𝑑
𝛾𝑆
=
𝑊𝑑
𝐺.𝛾𝑤
Volume of water equivalent to
volume of solid

10. W1
(a)
W2
(b)
W3
(c)
W4
(d)
 Equivalent weight of water
=
𝑊𝑑
𝐺.𝛾𝑤
×𝛾𝑤 =
𝑊𝑑
𝐺
 If the solids from (c) are replaced
with water of equivalent weight
𝑊𝑑
𝐺
 We get the weight W4 from (d)
 W4=W3-Wd+
𝑊𝑑
𝐺
 W4=W3-Wd(1-
1
𝐺
)
 W3 - W4= Wd(
𝐺−1
𝐺
)
 Wd = ( W3 - W4 )(
𝐺
𝐺−1
)
𝑤 =
𝑊𝑊
𝑊𝑑
×100%
w =
𝑊2−𝑊1 −𝑊𝑑
𝑊𝑑
×100%
w = [ (
𝑊2−𝑊1
𝑊3−𝑊4
) (
𝐺−1
𝐺
) -1] ×100%