Curing concrete, whether it is footings, slabs, walls, architectural or
non-architectural, is defined by the American Concrete Institute as maintaining satisfactory moisture content and temperature in concrete during its early stages so that it may obtain the desired properties that the
owner, engineer, and architect expect. The effects of curing the concrete can play a major role in either diminishing or enhancing its strength, durability, and appearance. For example, a slab that is not cured properly
may exhibit more drying shrinkage cracks due to excessive evaporation or if cured improperly, may show significant discoloration.Concrete curing methods can be divided into two basic methods for retaining
a satisfactory moisture content. First, moisture can be retained by fogging, ponding, or immersion and second, moisture can be retained by the application of curing compounds or impervious coverings.
If the decision
is to cure by ponding or immersion in water, the water temperature should be kept to plus or minus twenty-five degrees to reduce thermal stress in the concrete. It is very important that the concrete surface be kept
continually wet. If the concrete is subject to alternate cycles of wetting and drying, it may cause surface crazing and cracking
Fogging or spraying with water are excellent methods of curing if temperatures are well
above freezing and the water source and run off do not create any site problems. Soaker hoses and fogging nozzles may also be used as a good way to reduce rapid evaporation of moisture from the concrete surface.
Impervious paper or plastic sheeting may be used to seal or prevent the loss of moisture from the concrete surface. It should be tightly sealed to maintain close contact with the concrete surface during the curing
process. Impervious paper or plastic should not be used for colored concrete or architectural concrete due to the possibility of discoloration, especially where wrinkles and seams are present.
Curing compounds are
probably the most widely used due to the ease of application and cost. A good solution is a combination cure/seal compound that will seal and protect the concrete in addition to proper curing. Due to their
reflective nature, white pigmented curing compounds should be used in hot weather situations to reduce solar heat gain and maintain cooler in-place concrete temperatures. It should be noted that some curing
compounds may affect bonding of concrete surfaces and the adhesion of some flooring systems. You should check the manufacturer's product data for this information.
Curing does play a vital role in both the structural
properties of finished concrete and in its appearance. A discussion of curing procedures should take place in all pre-pour meetings. It is a critical process in the complete performance of the concrete and should be
addressed by the architect, engineer, owner, supplier, and contractor to insure that the quality and durability of the concrete are met.
