8.11 : Curing Methods

Concrete members with a small surface-to-volume ratio are cured by oiling and moistening the forms before casting the concrete member. These forms can be left in place for a prolonged period to prevent moisture loss, and can be wetted if made of a material suitable for wetting. If the forms are removed early, the concrete member is moistened and covered with polythene sheets to maintain moisture. For large horizontal concrete surfaces exposed to dry weather, a temporary covering is suspended above the surface until the concrete sets, after which wet curing is initiated. Wet curing can be achieved by spraying or fogging water over the concrete using a system of nozzles or by ponding the surfaces with water. Also, covering the concrete with moistened sawdust, straw, or saturated moisture-retaining fabrics like wet hessian or cotton mats maintains the contact of concrete with water. Impervious membranes, such as waterproof papers, plastic sheets, or membrane-forming sealing compounds, are also utilized to reduce moisture evaporation from concrete. However, these membranes fail to replace the moisture lost by self-desiccation, as the entry of moisture into the concrete from outside is impossible. Immersion in water is practiced to cure laboratory test specimens of concrete.