Curing is a procedure of promoting the hydration of cement for development of concrete strength and controlling the temperature. As a result of curing, we can achieve higher strength and reduced permeability which is very vital for long term strength or durability. The effect of curing has been shown in the following figure.
The curing is required for full development of strength. Initially the entire concrete has sufficient quantity of water for hydration. But over the passage of time, the water is lost due to evaporation or it is consumed due to reaction of hydration. The relative humidity, thus, falls below 80% level and the hydration process eventually stops.
Important Notes to Remember
Curing should be started as earliest as possible
For the portion of concrete which is covered with formwork, the curing should be started as soon as formwork is removed.
On exposed surface, it should be started when concrete has sufficiently hardened such that it doesn’t get disturbed by curing.
Ensure uninterrupted curing. If it is discontinued for any reason, the reaction of hydration will be stopped permanently. The partial hydration makes the capillary pores discontinuous and water can’t enter the concrete even if the curing is started again.
High strength concrete should be cured at an early age.
There is a widespread belief that humid climate is sufficient and curing is not required in rainy season.
The person generally entrusted for curing is the most unskilled person. He doesn’t appreciate the importance of curing. In fact he believes that curing is a process of wastage of water, time and money.
It can’t be made a measurable item in the contract.