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

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 degrees 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 tin logarithmic scale) is represented, the slope values from regression analysis data obtained for the 20 degrees C curing temperature series and origin ordinate from regression analysis data obtained for the 40 degrees C or 60 degrees C curing temperature series become good parameters for evaluating pozzolanic activity. An equivalence among R-c values obtained at curing temperatures of 20 degrees C and 40 degrees 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 degrees C range. (C) 2000 Elsevier Science Ltd. All rights reserved.