Some cracking is bound to happen when dealing with concrete, and though it is difficult to totally eliminate it, certain steps can be taken to minimize cracking so its likelihood of creating more serious problems is reduced.
More than just preventing cracks, curing paves the way for the strength development and durability of concrete so it can withstand freezing and thawing, and able to resist abrasions and scaling. Properly cured concrete does not necessarily lack cosmetic cracks, but the cracks are typically easily filled over without affecting the structural integrity of a building.
Factors Affecting Length of Curing Period
Adequate curing often depends on a variety of factors including the concrete's specified strength (like the ability to hold 10 tons or more without breaking), the proportions of mixture (cement to aggregates to water), the size and shape of the concrete member, the prevailing weather conditions at the time of curing, and future exposure conditions like the elements.
Generally, pavements, parking lots, driveways, sidewalks, canal linings and floors require a curing period of at least seven days if the ambient temperature is above 40°F. The same curing period applies to piers, columns, slabs, beams, cast-in-place walls, small footings, retaining walls, and bridge decks if the same temperature prevails.
Curing in Hot or Cold Weather
Curing in cold weather entails use of evaporation reducers, heated enclosures, insulating blankets, and curing compounds. The curing period is of course longer than when curing is undertaken during hot weather, with the longer curing period necessary to achieve greater compressive strength.
In hot weather, as evaporation happens sooner, concrete is cured by wetting substrate surfaces with water to prevent rapid moisture loss at the surface before the concrete has achieved enough tensile strength. Failure to do so leads to plastic shrinkage cracking. Evaporation retardants, windscreens, sunscreens, and fogging are usually employed to lengthen the curing time and enable the concrete to achieve the right compressive strength.