Rapid-setting cements are used in concrete under a variety of acronyms (HES for High Early Strength, or RSC for Rapid Strength Concrete, etc.). Their use is becoming increasingly important because the stresses on our highway and airport infrastructure require increasingly fast construction. This broad nomenclature hides a number of important differences between materials. In some respects, there is no such thing as single RSC; there are several different RSCs.
Specifications, appropriately so, focus on performance instead of chemical composition. For example, one key specification is early age strength, such as 400 psi flexural strength at 4 hours in order to re-open pavement to service. Yet differences in materials usually result in differences in durability. For example, if only early strength is specified, what is the impact of differences in early shrinkage? If pavement enters service at 4 hours, shouldn’t a shrinkage protocol also start at 4 hours? Typical shrinkage testing specifications do not.
This paper reviews the chemistry and hydration of the different types of materials available on the market (accelerated portland-based systems, belitic calcium sulfoaluminate, calcium sulfoaluminate blended with portland and calcium aluminates, for example) typically used for RSC. With this understanding, owners can further improve concrete pavement performance-based specifications for RSC.