Effect of Fly Ash Fineness on Temperature Rise, Setting, and Strength Development of Mortar

This paper investigates the effects of the fineness and replacement ratio of fly ash on the temperature rise and setting time, and compressive, tensile, and flexural strength of mortar mixtures. Three types of fly ash with Blaine finenesses of 4,125 cm2/g (40F), 6,686 cm2/g (60F), and 9,632 cm2/g (90F) were used to replace Portland cement at replacement ratios of 0 (which was the control mix), 15, 30, 45, and 60% by binder mass. Test results demonstrate that using fly ash as a cement replacement resulted in a reduction in the maximum temperature rise in mortar regardless of the fineness of the fly ash. In this investigation, 15 fly ash replacement caused a reduction in the peak temperature of about 4 to 6°C in the mortar. The setting time of fly ash mixes where 15 and 30% of the cement was replaced with fine fly ashes was faster than that of the control mix. The compressive strength of mortar mixes using finer fly ashes (60F and 90F) was significantly improved compared to that of the 40F fly ash mortar.