Determination of Initial and Final Setting Time of Concrete

IMPORTANCE & THEORY:
TEST FOR SETTING TIME:
This test is carried out to find whether cement sets at a rate suitable for a particular work. There is no necessary relationship between the time of setting and that of hardening or attaining the maximum strength. Slow setting cement may harden more rapidly than a quick setting one, and vice versa. The hardening of cement is actually a continuation of the chemical action which began with setting if the cement is placed in the mould. After initial setting time the cement mould can be detached and after final setting time the Vicatt’s apparatus plunger gives no impression. .
The initial setting time can be defined as “time taken by paste to stiffen to such an extent that the Vicatt’s needle is not permitted to move down through the paste through 25 mm.”
The final setting time can be defined as “it is the time after which the paste becomes so hard that Vicatt’s 5mm needle doesn’t sinks visibly and leave no impression”.
With Portland cement and rapid hardening cement the normal initial setting time should not be less than 30 minutes and the final setting time should not be more than 10 hours With quick setting cement the initial setting time should not be less than 5 minutes and the final setting time should not be more than 30 minutes.
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Determination of Initial and Final Setting Time of Concrete