Ex 2 water content by calcium carbide method

Geo-technical Engineering

1. Experiment No: 02 Date:
DETERMINATION OF WATER CONTENT BY CALCIUM CARBIDE
METHOD
Objective and Scope:
Rapid determination of water content from the gas pressure developed by the reaction of calcium
carbide with the free water of the soil.
Reference:
IS: 2720 (Part II) -1973
Soil specimen:
Sand requires no special preparation. Coarse soil may be grounded and pulverized. Cohesive and
plastic soil is tested with addition of steel balls in the pressure vessel. This test requires about 6 gm of
soil sample.
Equipments:
1) Metallic pressure vessel with clamp for scaling cup and gauge calibrated in percentage water
content.
2) Counterpoised balance for weighing sample.
3) Scoop for measuring absorbent.
4) Absorbent bottle (Calcium carbide)
5) Cleaning Brush
6) Steel balls- three balls of about 12.5 mm dia. and one steel ball of 25 mm dia.
Procedure:
1) Set up the balance. Place the sample in pan till the mark on the balance arm mass lines up with the
index mark. Unclamp the clamping screw of the instrument sufficiently to move the U-clamp off
the cup. Lift off the cup. Clean the cup and body with cleaning brush.
2) Hold the body horizontal and gently deposit one scoopful of absorbent (Calcium carbide) half way
inside the chamber. Then lay the chamber down without disturbing the absorbent charge. Transfer
the soil weighed from pan to the cup. Holding cup and chamber approximately horizontal bring
them together. Without disturbing sample, bring the U-clamp round and clamp the cup tightly in
the place.
3) With gauge downwards shake the moisture meter up and down vigorously for 5 sec, then quickly
turn it so that the gauge is upwards, give a tap to the body of the moisture meter to ensure that all
the content fall into the cup. Hold the rapid moisture meter downwards, again shake for 5 min.,
then turn gauge upwards and tap. Hold for 1 min.
4) Repeat this for three times. Water present in the soil reacts with the calcium carbide powder
releasing acetylene gas which exerts pressure on the dial from which water content on wet basis is
read. This is converted into dry basis as shown in the observation table.
5) Finally release the pressure slowly (away from the operator) by opening the clamp screw and
taking cup out, empty the contents and clean the instrument with the brush.

2. Observation table:
Sr.
No.
Description 1 2 3
1 Water content obtained on wet basis as the reading
on the rapid moisture meter

2 Water content on the dry basis ω = m ×
100
(100−m)
%
Average value of water content (%)
Calculation:
Water content (%) ω = m ×
100
(100−m)
%
Result:
Water content of given soil sample on dry basis =

3. Description
1. Scoop 2. Balance Base
3. Index mark 4. Balance arm
5. Stirrup 6. Pan
7. Gauge (0 - 50 percent) 8. Body
9. Cup 10. U-clamp
11. Clamp screw
Fig.1. Rapid Moisture Meter