EFFECTS OF FLY-ASH ON THE DEVELOPMENT OF MECHANICAL RESISTANCE OF PRECAST CONCRETE

The results of an investigation of the influence of fly ashes on the d evelopment of mechanical properties of concretes subjected to 24-h the rmal curing are presented in this paper. In addition to the curing tem perature (23 and 60 degrees C), the variables studied in this investig ation were the type of cement (types 10 and 30) and the source of fly ashes (four different North-American class F fly ashes). Overall, 10 d ifferent concrete mixtures were tested. Test results indicate that the rmal curing tends to increase significantly the concrete compressive s trength in the first 24 h. Data also demonstrate that the thermal curi ng regime does not have any detrimental effect on the long-term compre ssive strength of ordinary portland cement concrete. Compressive stren gth of fly ash concretes was significantly reduced by thermal curing i n the 1- to 28-day period, despite an initial increase. The influence of thermal curing on the development of concrete compressive strength is discussed.