Setting Time of Concrete

April 21, 2020

When cement paste starts to harden that is called initial setting time and once cement paste has hardened sufficiently that is called final setting time. Cement past has hardened can be specify by using needle. If 1mm needle makes an impression on the paste in the mould but 5 mm needle does not make any impression that means paste has hardened.

It is necessary that cement should not neither be settled too fast nor too slow. This is because 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. Setting time should not be confused with hardening. Setting time means the time required for stiffening of cement paste to a defined consistency.

Initial setting time is the time when paste starts to lose its plasticity. Initial setting time test is important for transportation, placing and compaction of cement concrete.Initial setting time duration is required to delay the process of hydration or hardening. When cement paste completely loses its plasticity it is called final setting time.

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.Determination of final setting time period facilitates safe removal of scaffolding or form.During this period of time primary chemical reaction of cement with water is almost completed.

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