Effects of ultrafine fly ash on the properties of high-strength concrete

Ultrafine fly ash was added in the concrete mixtures in two different replacement ratios: 20 and 35 % in comparison with the control group. The water-to-binder ratio was 0.28. Standard curing and temperature matching curing methods were applied. Results showed that ultrafine fly ash decreased the adiabatic temperature rise of concrete and the bigger the replacement ratio, the more the decrease. It also decreased early compressive strength of concrete under standard curing condition, but it was compensated under temperature matching curing condition. Resistance to permeability of concrete was enhanced by ultrafine fly ash because the pore structure was improved. TG test reveals that the nucleation effect of ultrafine fly ash accelerated cement hydration. Temperature matching curing promoted the pozzolanic reaction of ultrafine fly ash at the early age. Non-evaporable water content was increased by ultrafine fly ash incorporation under standard curing condition, while at later age, under temperature matching curing condition it reduced the non-evaporable water content.