Early-age hydration and mechanical properties of high volume slag and fly ash concrete at different curing temperatures

[Display omitted] •The dilution, filler and retardation effects of high volume GGBS and FA are observed to affect early age hydration of cement.•The hydration process of binders with FA is found to be more sensitive to temperature than that with GGBS.•The equivalent age equation exactly predicts the early age strength development at ambient temperature. Multiple Supplementary Cementitious Materials (SCM) in large quantities have been used in quasi-mass concrete to minimize the crack risk. Yet the hydration process of concrete with high volume addition of SCM, especially effect of temperature on the early stage hydration, has been rarely investigated. In this paper, early age hydration progress and mechanical properties of concrete with high volume GGBS and FA were studied under different curing temperatures. The results show that high volume GGBS and FA accelerate the cement hydration in early age due to the dilution and filler effects. However, the hydration was slowed down when the addition of FA is up to 55% and 70%. Compared to binders with GGBS, the hydration process of binders with FA are more sensitive to temperature. The results also imply the necessity of the introduction of a range factor of hydration degree for effective estimation of Ea for binders with high volume of SCM. The equivalent age equation effectively predicts the early age strength development of high volume SCM concrete curing under changing temperature in an actual structure and what needed to do is to modify the activation energy by considering the hydration progress of binder with high volume SCM.