Compressive strength and hydration of high-volume wet-grinded coal fly ash cementitious materials

摘要

High volume coal fly ash (FA) cementitious system (C-FA) was reported to present great economic and environmental benefits in cement and concrete industry, but the slow strength development limited its use in real engineering practice. In this study, FA was processed by wet-grinding in order to obtain super-fine particles. Three kinds of FA, namely raw FA with D50 (Median particle size) of 19.70 mu m, wet-grinded FA with D50 of 2.67 mu m and 7.80 mu m, were used; 30%, 50%, and 70% replacement ratio in C-FA system were designed. The compressive strength, hydration, and pore structure were investigated, and the cost and CO2 emission of the system were also considered. The results showed that FA with D50 = 2.67 mu m could be obtained by 2 hours' wet-grinding; 30% replacement ratio increased the compressive strength by 16% at 1 d age and 22% at 28 d age in comparison with the reference; surprisingly, 50% replacement ratio even showed slightly higher 28 d strength than that of the reference; the main reason for the increased strength was due to the refined the pore structure, the densified hardened system, and the promoted pozzolanic reaction of FA. The system with 30% and 50% replacement ratio of wetgrinded FA (D50 = 2.67 mu m) showed greater environmental and economic advantages in comparison with cement-raw FA system. Such results would be expected to offer one new way for utilization of FA and the design of low carbon cementitious materials. (C) 2019 Elsevier Ltd. All rights reserved.