What is the initial setting time of Portland-Pozzolana Cement when tested by the Vicat apparatus method as described in IS 4031 (Part 5):1988?
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A.
60 minutes
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B.
30 minutes
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C.
40 minutes
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D.
10 minutes
Correct Answer:
B. 30 minutes
Explanation:
The correct answer is 30 minutes.
According to IS 4031 (Part 5): 1988, which specifies the methods for physical tests of hydraulic cement, the initial setting time for Portland-Pozzolana Cement (PPC) must not be less than 30 minutes. This test is conducted using the Vicat apparatus, where a 1 mm square needle is released into a cement paste of standard consistency. The initial setting time is recorded as the duration from the moment water is added to the cement until the needle stops penetrating the paste at a distance of 5 mm to 7 mm from the bottom of the mold. This standard ensures that the cement remains workable long enough for proper mixing, transportation, and placement before it begins to lose its plasticity and harden.
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