Q.: A customer reports that he got a nice white color when he applied our curing agent to a broomed-finish pavement the day after finishing. However, he complains that the same curing agent leaves the concrete looking dark when he applies it immediately after brooming. Is this a defect in the curing agent, or could something in the concrete be causing the trouble? Our product is a solvent system clear acrylic that meets the requirements of ASTM C 309, "Standard Specification for Liquid Membrane-Forming Compounds for Curing Concrete." We recommend applying it at the rate of 200 square feet per gallon.
A.: Some curing agents are formulated with white pigment to reflect sunlight and thereby prevent heat buildup in summer heat. These materials give the concrete a whitish appearance until the curing agent wears off or deteriorates, one to several months later. They don't impart a permanent whiteness. Since your product is unpigmented and clear, the product itself doesn't make the concrete white. The lightness in color that your customer experienced may have been the result of allowing the concrete to dry a day before applying the curing agent. If so, the surface will be less hard and wear resistant than if he had applied the curing agent promptly, as he should have done. In the long run both concrete surfaces should be about the same color, other things being equal.