Thursday, June 28, 2018

TESTING OF CEMENT – SETTING TIME TEST

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SETTING TIME
The time interval for which the cement product remains in plastic condition is known as the setting time.
Initial Setting Time                 Final Setting Time
Ordinary Portland Cement                 30 min                                           10 hrs
Rapid Hardening Cement                   30 min                                           10 hrs
Low Heat Cement                                 60 min                                           10 hrs
INITIAL SETTING TIME
Initial setting time is the time elapsed between the moment that the water is added to the cement, to the time that the paste starts losing its plasticity.
PROCEDURE
Take 500gms of cement sample and gauge it with 0.85 times of water required to produce a standard consistent cement paste. Fill the cement paste in Vicat’s mould within 3-5minutes. Start the stop watch, the moment water is added to the cement.
The initial setting time is the time elapsing between the time when the water is added to the cement and the time at which the needle penetrates to a depth of 33-35mm in the test block. But initially the needle gets penetrated completely into the mould.
FINAL SETTING TIME
Final setting time is the time elapsed between the moment when the water is added to the cement and the time when the paste has completely lost its plasticity. This time should not be more than 10hrs.
PROCEDURE
Take 500gms of cement sample and gauge it with 0.85 times of water required to produce a standard consistent cement paste. Fill the cement paste in Vicat’s mould within 3-5minutes. Start the stop watch, the moment water is added to the cement.
Replace the needle of Vicat’s apparatus by a circular arrangement. The cement shall be considered as finally set, when upon lowering the attachment gently cover the surface of the test block, the centre needle makes an impression, while the circular cutting edge of the attachment fails to do so. The paste is said to have attained final setting time, when the centre needle does not pierce through the paste more than 0.5mm.

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