Internal curing (IC) was originally defined by the American Concrete Institute (ACI) as a means to supplying water throughout a freshly placed cementitious mixture. The process produces reservoirs that readily release water as needed for hydration, or to replace moisture lost through evaporation or self-desiccation.

IC is often referred to as “curing concrete from the inside out.” IC using prewetted expanded shale, clay or slate lightweight aggregate is a simple and practical way of supplying additional curing water throughout the concrete mixture. This is done by replacing some of the conventional sand in the mixture with an equal volume of prewetted Buildex Haydite^® fine aggregate.