The recently approved ASTM C1600/C1600M - Specification for Rapid Hardening Hydraulic Cement covers materials used in applications where reduced cementitious contents are desired or early service is needed, including paving, construction, stucco, mortar and block. Four types of cement are defined: Type URH (ultra rapid hardening) for use where ultra high early strength is desired; Type VRH (very rapid hardening) for use where very high early strength is desired; Type MRH (medium rapid hardening) for use where mid-range rapid hardening, high early strength is desired; and, Type GRH (general rapid hardening) for use when the higher-strength properties of VRH or MRH cement are not required.
The C1600 family includes environmentally friendly fly ash blends, made principally from coal combustion products, thereby requiring no additional fuel use and resulting in no additional carbon dioxide emissions. The C1600/C1600M standard was developed by Subcommittee C01.03 on Special Cements, chaired by James Hicks of Alexandria, Va.-based CeraTech, Inc., a designer, manufacturer and supplier of engineered, high-performance cements. ASTM C1600 lists minimum requirements for compressive strength, setting time, shrinkage and soundness [autoclave expansion], says Hicks. Optional specifications for sulfate expansion, alkali silicate reactions with aggregates, heat of hydration and expansion in water are also listed.