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Building Materials - Engineering

Q1:

If P is the percentage of water required for normal consistency, water to be added for determination of initial setting time, is

A 0.70 P

B 0.75 P

C 0.80 P

D 0.85 P

E 0.90 P.

ANS:D - 0.85 P

INITIAL AND FINAL SETTING TIME.

We need to calculate the initial and final setting time as per IS: 4031 (Part 5) - 1988. To do so we need Vicat apparatus conforming to IS: 5513 - 1976, Balance, whose permissible variation at a load of 1000g should be +1.0g, Gauging trowel conforming to IS: 10086- 1982.

Procedure to determine initial and final setting time of cement.

i) Prepare a cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consistency.

ii) Start a stop-watch, the moment water is added to the cement.

iii) Fill the Vicat mould completely with the cement paste gauged as above, the mould resting on a non-porous plate and smooth off the surface of the paste making it level with the top of the mould. The cement block thus prepared in the mould is the test block.