Numerical simulation of early-age thermal stress of high volume fly ash (HVFA) concrete

Abstract This paper numerically studied the effect of fly ash (FA) replacement on early-age thermal stress of concrete. Different FA replacement levels (0%, 20%, 50% and 80%) on the thermal stress and cracking risk of concrete have been considered. Results showed that, due to the FA effect on the reduction of hydration heat, the maximum temperature and corresponding compressive stress during the temperature rise stage were both lowered; meanwhile, the strength of concrete was simultaneously weakened, leading to lower cracking stress when the FA replacement increased gradually. Finally, the cracking temperature of concrete decreased when the FA replacement level increased up to 50%, and converted to plateau with higher FA replacement level. Overall, FA replacement level with 50% was recommended for concrete under restraint cracking risk.