In addition to maintaining a moist environment, the methods discussed here also cool the concrete in hot weather through evaporation. The amount of water needed (or evaporation rate) can be computed from the tables if we know the wind speed, temperatures of the air and that of the concrete. Total water requirement will be the product of the evaporation rate and the exposed surface area.
Ponding or immersion
This method is suited to curing flat surfaces, such as pavements and floors. Sand or earth may be used to form dikes around the concrete surface to be cured. It is important that the material used does not discolor the finished concrete. The surface between the dikes is then flooded with water which ideally should be no more than 20°F cooler than the concrete surface. Temperature differentials above this could result in development of thermal stresses and eventual cracking.
This is however labor intensive, as it needs constant supervision and is useful mostly on small jobs.
Ponding is also commonly used for curing specimens in laboratories.
Spraying or fogging
This method consists of continuously spraying a fine mist of water through a system of nozzles. Lawn sprinklers may be used for flat surfaces while soil-soaker hoses are useful on vertical or nearly vertical surfaces. The method is good when temperatures are well above freezing and humidity is low. While a constant spray is not essential, care is needed to ensure that the concrete does not dry out between applications.
Major disadvantages of spraying include the need for large amounts of water and supervision. Water could also erode the concrete surface if adequate care is not taken.
The surface of the concrete may be kept moist by covering with fabric material which is in turn kept saturated with water. Fabrics commonly used include burlap, cotton mats, and rugs. On smaller jobs, wet coverings of earth, sand, hay or saw dust can also be used. Whatever the material used, it is most important that it is evenly distributed over the entire previously moistened surface (including edges of slabs) and kept moist for the duration of the curing. The material should also not cause discoloration of the concrete.
Moist curing protects the concrete from self-desiccation and is theoretically better than using sealants (see Preventing loss of mixing water). The former method is however gradually giving way to the latter which is more laborsaving.