What is the reason behind the initial setting time of cement should not be less that 30min.?
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Initial setting time of various types of cement:
Please refer the above image for knowing the values of initial setting time and final setting time for various types of cement.
Initial Setting Time is regarded as the time elapsed between the moment that the water is added to the cement to the time that the paste starts losing its plasticity.
In actual construction dealing with cement paste, mortar, or concrete, a particular time is required to mix, transport, place, compact, and finish. During this time, cement paste, mortar, or concrete should be in plastic condition. The time interval for which the cement products remain in the plastic condition is known as Initial Setting Time.
The final setting time should not be more than 10 hours.
Usually, a minimum of 30 minutes is given for mixing and handling operations.
Final Setting Time elapsed between the moment water is added to the cement and the time when the paste has wholly lost its plasticity and has attained sufficient firmness to resist absolute definite pressure.
The constituents and fineness of cement are maintained to remain in plastic condition for a particular minimum time. Once the concrete is placed in the final position, compacted and finished, it should lose its plasticity in the earliest possible time to be least vulnerable to damages from external destructive agencies.
Hope you get the concept.
The main reason behind the initial setting time of cement should not be less than 30 min is that the initial setting time is the exact moment when the concrete starts to harden. In theory, this time starts as soon as the water is added to the cement. The final setting time is the moment the concrete has hardened enough so that a five-millimetre square needle no longer penetrates the surface.
In this time cement can be molded in any desired shape without losing its strength. This is the time at which the hardening of the cement starts and the only time available for mixing the paste and placing it in position. if this time less then 30 min then can’t molded in any shape in many situations.
Initial setting time:
When we deal with cement, mortar or concrete during the construction process then the time required for mixing, transportation, placement, compaction, and finishing is more.
During this whole time, our cement should be in plastic condition and it should not be set.
The time which is required for the cement products remain in a plastic condition is known as initial setting time. Usually, a minimum of 30 minutes is the initial setting time.
It is the time required for mixing and handling operations.