write short note on soundness of cement.
Answers
Answer:
soundness” refers to the ability of a hardened cement paste to retain its volume after setting without delayed destructive expansion (PCA, 1988). This destructive expansion is caused by excessive amounts of free lime (CaO) or magnesia (MgO).
We determine the soundness of cement by Le-Chatelier method as per IS: 4031 (Part 3) – 1988.
PROCEDURE
Place the mould on a glass sheet and fill it with the cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency (see Para 1.2).
Cover the mould with another piece of glass sheet, place a small weight on this covering glass sheet and immediately submerge the whole assembly in water at a temperature of 27 ± 2oC and keep it there for 24hrs.
Measure the distance separating the indicator points to the nearest 0.5mm (say d l ).
Submerge the mould again in water at the temperature prescribed above. Bring the water to boiling point in 25 to 30 minutesand keep it boiling for 3hrs.
Remove the mould from the water, allow it to cool and measure the distance between the indicator points (say d 2 ).
(d 2 – d l) represents the expansion of cement.
Explanation:
Soundness of cement is the property of hardened cement paste undergoing large change in volume after setting without delayed destructive expansion. This destructive expansion is caused by excessive amounts of free lime or magnesia. It is tested in accordance to (IS:4031-PART 3-1988).