Influence of in-situ casting temperature and curing regime on the properties of blended cement concretes under hot climatic conditions

Abstract

Casting temperature and curing method significantly affect the properties of concrete, especially the blended cement concretes. Consequently, it is imperative to study the influence of casting temperature and curing regime on the properties of concretes. This paper reports results of a study conducted to evaluate the properties of plain and blended cement concretes prepared using very fine fly ash (VFFA), fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBFS) and natural pozzolan (NP) cast and cured under varying temperature and curing conditions. The concrete specimens were prepared under natural summer atmosphere at intital concrete temperature of 25, 32, 38 or 45 °C. The specimens were cured under laboratory conditions by water ponding and under hot weaterher conditions by covering with wet burlap or applying a curing compound. The effect of casting temperature and curing regime on the properties of the studied concretes was evaluated by measuring compressive and split tensile strength up to 180 days, pulse velocity up to 90 days and depth of water penetration after 28 days of curing. As expected, the properties of concrete specimens cured by water ponding were better than those cured by covering with wet burlap or applying a curing compound. The properties of blended cement concretes were better than those of plain cement concretes at later ages due to the pozzolanic reaction. It is postulated that the optimum casting temperature is 32 °C for OPC and SF cement concretes while it is 38 °C for VFFA, FA, GGBFS and NP cement concretes. This finding differs with the current international practice of limiting the casting temperature to 35 °C.