Important Notes on Setting Time Test of Cement
o It is essential that cement set neither too rapidly nor too slowly. In the first case there might be insufficient time to transport and place the concrete before it becomes too rigid. In the second case too long a setting period tends to slow up the work unduly, also it might postpone the actual use of the structure because of inadequate strength at the desired age.
o Setting should not be confused with hardening, which refers to the gain in mechanical strength after the certain degree of resistance to the penetration of a special attachment pressed into it.
o Setting time is the time required for stiffening of cement paste to a defined consistency.
o Indirectly related to the initial chemical reaction of cement with water to form aluminum-silicate compound.
o Initial setting time is the time when the paste starts losing its plasticity.
o Initial setting time test is important for transportation, placing and compaction of cement concrete.
o Initial setting time duration is required to delay the process of hydration or hardening.
o Final setting time is the time when the paste completely loses its plasticity.
o It is the time taken for the cement paste or cement concrete to harden sufficiently and attain the shape of the mould in which it is cast.
o Determination of final setting time period facilitates safe removal of scaffolding or form.
o During this period of time primary chemical reaction of cement with water is almost completed.