The feasibility of properly raising temperature for preparing high-volume fly ash or slag steam-cured concrete: An evaluation on DEF, 4-year strength and durability

Abstract

Properly raising steam-curing temperature may aggravate the delayed ettringite formation (DEF) and be adverse to the long-term performance of concrete while adding fly ash or slag may alleviate the DEF and be beneficial to the long-term performance of concrete. However, their comprehensive effect is still unclear. In this paper, the feasibility of properly raising temperature from 60 °C to 80 °C for preparing high-volume fly ash or slag steam-cured concrete (HFC-80 or HSC-80) is investigated by evaluating the comprehensive effect of properly raising steam-curing temperature and adding fly ash or slag on the DEF, 4-year strength and durability. Plain cement concrete with 60 °C and 90 °C (PC-60 and PC-90) steam curing is used as the reference. The results show that DEF in HFC-80 is significantly delayed compared with that in PC-90 while DEF does not occur in HSC-80. The expansion of HFC-80 at 4 years is significantly larger than that of PC-60 while the expansion of HSC-80 is as small as that of PC-60. The compressive strength of HFC-80 or HSC-80 at 4 years is 12%-18% smaller than that of PC-60 while the resistance to chloride ion permeability of HFC-80 or HSC-80 at 4 years is better than that of PC-60. Therefore, it can be preliminarily judged that properly raising steam-curing temperature may be unfeasible for HFC but feasible for HSC in terms of in terms of the above results.