Curing is the protection of fresh concrete from evaporation and temperature extremes that might adversely affect cement hydration. Broadly speaking, this term covers all of the atmospheric conditions, both natural and artificially created, that affect the extent and the rate of hydration of the cement present in the mix. For all practical purposes these conditions boil down to the control of moisture content and temperature. If concrete is to gain a high percentage of its potential strength it must have: (1) sufficient water for hydration of the cement and (2) a temperature conducive to maintaining this chemical reaction at a rapid, continuous rate. To insure the existence of these conditions, the concrete must be protected from the harmful influences of wind, sun and weather- conditions that might adversely change the available water and ambient temperature. The mixing water used in concrete serves two purposes: it is the agent which reacts with the cement to produce hydration products and it provides the necessary lubrication to facilitate placing of the mix. Temperature also affects the rate of concrete hardening. High temperatures accelerate the hardening process; low temperatures slow it down. Near or below freezing point there is practically no chemical reaction at all. Research has proved that concrete develops its best properties when hydration proceeds at a slow, steady rate; it is thus important that the method of curing be such that temperature fluctuations are avoided as much as possible.