The development of strength and durability of any concrete mix, regardless of the type of cement used, depends on the degree of hydration of the cement. Strength and durability depend upon the
chemical reaction between the cement and water.
If concrete is allowed to dry out, this reaction ceases and inhibits strength and potential durability. Premature loss of water must be prevented, for the full benefits of cement hydration in the hardening of concrete.
|Type of Construction||Curing Method||Application|
|Pavements and slabs, etc.||
||Apply in close contact with surface immediately after finishing taking care to prevent damage.|
and walls, etc.
||Apply in close contact with surface immediately after formwork is removed, leave undisturbed for at least 4 days, preferably 7 days.|
In the case of slabs which are to be floated, protection from drying may be required after placing but before final finishing begins. Most curing compounds are not recommended for surfaces that are to receive finishes such a screed, plaster or paint, because of the likelihood of reduced bond.
Curing by ponding or continuous spraying of water is seldom used because of the practical problems associated with supply, containment and ultimate disposal of water used for curing. Care must be taken to avoid sudden temperature changes caused by the use of cold curing water on warm concrete. Cycles of wetting and drying should also be avoided. Both the above may lead to micro-cracking of the surface.
Water curing is only suitable when the temperature is well above freezing. Materials such as wet hessian or wet sand are sometimes used, but they must be kept continuously wet and not allowed to dry out. Damp materials may stain concrete. Black polythene sheeting should be avoided in hot weather, but has its advantages in cold weather.