The FHWA’s video, “Internal Curing,” describes this method of water curing concrete. Unlike conventional curing that supplies water from the surface of concrete, internal curing provides the curing water from the porous aggregates that are mixed into the concrete mixture.
The 9-minute video explains how this curing methodology has evolved from bridge-deck paving applications to other concrete pavement types and applications. The video credits the Illinois Tollway as being one of the agencies leading the paradigm shift.
The video explains how prewetted, expanded lightweight aggregates and sand are used to provide hydration in the internal curing process. The video also illustrates how the water promotes more complete hydration of the concrete, noting that this method is particularly beneficial with low water-cementious ratio concrete mixtures.
The video also describes the method for measuring and controlling the moisture in the lightweight aggregates. It also describes how internal curing contributes to greater durability, less shrinkage and curling, tighter (better controlled) cracks and other benefits in concrete pavements. In the few years since this video was produced, the acceptance and use of internal curing has increased for bridge deck and some highway applications.