Question

write the importance of initial setting time of cement in various operation of making cement mortar and cement concrete

Answer 1

Intial setting time for Portland cement should not be less than 30 minutes. It is defined as the time lapse between water added to the cement and the instance when cement paste start loosing its plasticity.

Initial setting time adjusted according to the type of work by adding accelerator or retardar.

Importance of initial setting time in transportation, placing and compaction of concrete.

Suppose concrete mixing plant and placing plant is far away from each other then in that case initial setting time should be such that hydration of concrete should not occur at the time of transportation. In this case retarders are used to decrease the rate of hydration.

When work is to be done inside water bodies then in that case quick setting cement is required. Initial setting time in this case should be 5 minutes. Accelerators are used in this case to increase the rate of hydration in cement concrete.