Enhancement of early-age strength of the high content fly ash blended cement paste by sodium sulfate and C-S-H seeds towards a greener binder

Due to the economic and environmental benefits, the industry by-products like fly ash have been intensively employed to partially substitute cement in concrete and other cementitious materials. However, with the increased substitution level of cement by fly ash, the major drawback is the low early-age strength of cement paste owing to the slow pozzolanic reaction of fly ash. This study aims to accelerate the early-age strength of high content fly ash blended cement paste using sodium sulfate and calcium silicate hydrate (C-S-H) seeds. The results show that sodium sulfate and C-S-H seeds exhibit a synergistic enhancement effect on the early-age strength of high content fly ash blended cement paste, which is much higher than the sum of individual effects of sodium sulfate and C-S-H seeds. Therefore, the high replacement of cement by fly ash towards a greener binder can be achieved by the application of sodium sulfate and C-S-H seeds. Moreover, the underlying mechanism of the synergistic effect is revealed through this study. (C) 2019 Elsevier Ltd. All rights reserved.