Mechanical treatment of fly ashes: Part IV. Strength development of ground fly ash-cement mortars cured at different temperatures

Abstract

The influence of fly ash grinding on the strength development of fly ash/cement mortars cured at different temperatures was studied. A significant increase of compressive strength ( R c) for fly ash mortars was found at early age (3 days) when curing temperature is raised. However, the highest R c values at 28 days' curing time were obtained for fly ash mortars cured at 40°C. The higher reactivity of fly ashes was found for ground fly ashes (GFA) compared to unground fly ash (T0). When R c vs. curing time (in logarithmic scale) is represented, the slope values from regression analysis data obtained for the 20°C curing temperature series and origin ordinate from regression analysis data obtained for the 40°C or 60°C curing temperature series become good parameters for evaluating pozzolanic activity. An equivalence among R c values obtained at curing temperatures of 20°C and 40°C and different curing times was proposed from strength gain data for mortars containing 15%, 30%, 45% and 60% replacing percentages. Finally, the compressive ( R c) and flexural ( R f) strength values for early ages and different curing temperatures were measured. A mathematical model has been proposed for the mechanical properties at early age of mortars containing fly ashes in 15–60% replacement range and cured in 20–80°C range.