Question

Q4: What type of cement test is used to compute the amount of water to be added for making the cement paste for Initial setting time? Write the step-by-step guidelines of that cement test.

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Answer 1

In order to compute the amount of water to be added for making the cement paste for initial setting time, final setting time, strength and soundness of the cement a parameter referred as a Standard Consistency is required.

For this the test done is known as Consistency Test.

• Standard Consistency is defined as the consistency of the cement paste that permits the Vicat's Plunger of diameter 10 mm and height 50 mm to penetrate into the mould upto the depth of 33-35 mm from the top (5-7 mm from the bottom).
• In order to perform this test 500 grams of cement sample is taken and gauged with 24% of water by weight in the first trial and the paste formed is infilled in the mould and the depth of penetration of the plunger in it is noted.
• This test is repeated at different water content upto an extent till the penetration of 33-35 mm from the top is observed.
• This water content is recorded and termed as 'p'.
• This test is performed at the relative humidity of 90% and temperature of 27+/-2 °C.

In order to determine the initial setting time of cement, again the 500 grams of cement sample is gauged with '0.85p' of water content.

Water content used for initial setting time of cement = 0.85×standard consistency.