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Tips on Concrete Curing : 

Curing concrete is a complex process involving maintenance of proper temperature,

humidity, circulation, and other factors. Cracks may develop and cement strength may be

affected if adequate arrangements are not made for these controls. Crystals develop by the

reaction of water with Portland cement.  

What Is Curing 

Curing is much more than retaining moisture for a prolonged period on theconcrete surface. Curing is the process that ensures that the concrete attains its

desired strength. The strength of concrete is dependent on crystal growth within theconcrete matrix. These crystals grow due to the hydration that is the reaction

 between the water and Portland cement. If water is not adequate, the crystals

cannot grow, due to which the concrete is unable to attain the desired strength. The presence of water facilitates the crystal growth that encloses the gravel and sand

mix, causing interweaving with each other.

Controls During Curing 

It is important to maintain the proper curing temperatures otherwise the hydrationreaction will be affected. If the concrete is too hot, the hydration reaction will be

too rapid for a proper crystal growth. Thus, concrete will not attain proper strength.

The reaction being exothermic, temperature differentials will be created within the

concrete that may cause cracks. Unsuitable hydration on the concrete surface may

 produce rough surface and a porous concrete structure. Such permeable concrete

structures will permit calcium hydroxide to contact the concrete surface causing

efflorescence. The concrete structure is also weakened. Other important aspects

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that need care during the curing are proper humidity, circulation, insulation, and

time control.

Autogenous Shrinkage

Autogenous shrinkage occurs when the cement paste has lost shape due to

inadequate water for hydration. Autogenous shrinkage happens when the volumeof the hydrated cement products is less than the volume of the cement and water 

mix before hydration. It is not caused by external factors, such as loss of moistureor temperature changes. Autogenous shrinkage is usually not significant in

concrete with a water-cement ratio of greater than about 0.4. However, as this ratio

is decreased below that limit, autogenous shrinkage is likely to be increased. Mixes

with a water-cement ratio less than 0.40 do not have adequate water in the concretefor curing. In the early stages, when the tensile strength is low, and concrete is

under the effects of high temperature disparity, concrete may crack if autogenous

shrinkage occurs.

Modern Curing 

The specific controls of temperature, humidity, and time required during the process of curing are difficult to attain accurately, due to which proper concrete

strength and other characteristics may be affected. Self-curing technologies have been developed that use substances for internal curing. Appropriate materials are

applied to the wet concrete surface to decrease the loss of water from the concrete.

The materials developed are emulsions of paraffins that are scattered on to thesurface. An improved concrete is produced that has lesser permeability, and

therefore improved durability and strength.

Related Reading 

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