Theory: The ability of cement to maintain a constant volume is known as soundness of the cement. It is essential that the cement concrete shall not undergo appreciable change in volume after setting. Unsoundness produces cracks, distortion and disintegration there by giving passage to water and atmospheric gases which may have injurious effects on concrete and reinforcement. Soundness of cement is ensured by limiting the quantities of free lime,magnesia and sulphates as these compounds undergo a large change in volume.Unsoundness in cement does not come to surface for a considerable period of time. Thus this test is designed to accelerate the hydration of free lime by the application of heat thus discovering the defects in a short time. Further, to minimize the shrinkage of cement paste,the test setup is kept immersed in water bath.This test is carried out with the help of “Le Chatelier’s apparatus” which consists of a small split cylinder of spring brass or other suitable metal of 0.5mm thickness forming a mould 30 mm internal diameter and 30mm high (Figure 2). On either side of the split mould are attached to indicators with pointed ends, the distance from these ends to the center of the cylinder being 165 mm. The mould shall be kept in good condition with the jaws not more than 50mm apart.
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| Le-chatlier Apparatus |
Objective: Determination of soundness of cement by Le-Chatelier method.
Reference: IS 4031 (Part-3):1988.
Apparatus: Le- Chatelier apparatus conforming to IS: 5514-1969; Measuring cylinder;Gauging trowel; Balance; Water bath.
Material: Ordinary
Portland cement; Water; Grease
Procedure:
1. Weigh accurately 100 g of
cement to the nearest 0.15 g and add to it 0.78
2. Place the lightly grease mould on a lightly grease glass sheet and fill it with cement paste, taking care to keep the edges of the mould gently together.
3. Cover the mould with another piece of lightly grease glass sheet, place a small weight on this covering glass sheet and immediately submerge the whole assembly in water at a temperature of 27 ± 20 𝐶𝐶.
4. Keep this assembly under water
for 24 hrs. After this, take the mould out of
5. Bring the water to boiling
with the mould kept submerged, and keep it boiling
6. Remove the mould from the
water allow it to cool and measure the distance
7. The difference between these
two measurements represents the expansion of
8. Repeat the whole procedures two more times each
using fresh 100 g sample.
Observations:
Samples:
Distance
between pointers before boiling (D1) in mm
Distance
between pointers after boiling (D2) in mm
Expansion
of the cement = E1 = (D2- D1) in mm
Average
expansion of the cement in mm
Result:
Conclusions:
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