04-02-2013, 11:48 AM
SELF-CURING CONCRETE
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Introduction
Most of the concrete that is produced and placed each year all over the world already does self-cure to some extent. Some of it is not intended to have anything done to its exterior surface, except perhaps surface finishing. Yet the concrete’s ability to serve its intended purpose is not significantly reduced [1].
―Curing is the maintaining of a satisfactory moisture content and temperature in concrete during its early stages so that desired properties (of concrete) may develop. Curing is essential in the production of concrete that will have the desired properties. The strength and durability of concrete will be fully developed only if it is cured. No action to this end is required, however, when ambient conditions of moisture, humidity, and temperature are sufficiently favorable to curing. Otherwise, specified curing measures shall start as soon as required.‖ [1]
Most of the concrete in the world is placed in quantities that are of sufficient thickness such that most of the material will remain in satisfactory conditions of temperature and moisture during its early stages. Also, there are cases in which concrete has been greatly assisted in moving toward a self-curing status either inadvertently or deliberately through actions taken in the selection and use of materials [1].
Initial Surface Absorption Test (ISAT)
Figure 1 shows the 10-minute ISAT values obtained from concrete test specimens. The surface of the air cured control specimens absorbs water at a highest rate, the least permeable surfaces are those of the time cured specimens. The higher dosage of the self-cure chemical provided a greater improvement in surface characteristics, but at both concentrations the chemical decreases the rate of absorption at the surface [8].
With respect to surface quality, chloride diffusion, carbonation, corrosion potential and freeze thaw, resistance self-cure concrete provides improved performance when compared to air cured specimens. The improvements in concrete durability properties are dependent on chemical dosage. At the highest dosage used in this study properties, approaching, and in some cases as good as, those characteristics of the film cured control were achieved. It is conceivable that higher dosages could produce air-cured concrete with properties rivaling those achieved in the film-cured situation [8].