When concrete is not cured properly, its durability, strength and abrasive resistance are affected. Due to inadequate curing, concrete develops plastic shrinkage cracks, thermal cracks, along with a considerable loss in the strength of the surface layer.
When the surface of the concrete is not kept moist within the first 24 hours after the casting, the evaporation from the exposed horizontal surface results in plastic shrinkage cracks and a weak and dusty surface.
An excessive temperature difference between the outer and the inner layers of the concrete results in thermal cracking due to restraint to contraction of the cooling outer layers from the warmer inner concrete.
When concrete is allowed to freeze before minimum degree of hardening is achieved after casting, the concrete gets permanently damaged due to expansion of water within the concrete as it freezes. This results in irretrievable strength loss and makes concrete porous.
Inadequate curing of concrete results in the loss of properties of the surface layer of concrete up to 30–50 mm, not meeting the requirements of the design in terms of durability, strength and abrasion resistance.
The Effect of Curing on Strength
The curing of concrete helps in strength development on the surface of the member rather than the inner part. So, its main effect is not on the strength, but the durability.
Since the outer surface of the concrete is mainly considered for the cover to reinforcement, the effect of thermal cracks or plastic shrinkage cracks developed due to inadequate curing, on concrete strength under compressive loads will be much less than the element loaded in flexure. The structural element size and type of loading decide the effect of inadequate curing.
But for the long-time consideration of durability, the cracks developed makes the concrete surface porous which becomes the cause of reinforcement corrosion and can affect the concrete strength at a later stage.