Investigation of Hydration and Microstructure of Reactive Powder Concrete (RPC) Containing Steel Slag Powder

摘要

Cement and silica fume (SF) content of RPC are generally rather high compared with conventional concrete. Replacing cement with steel slag powder (SS) and ultra-fine fly ash (UFFA) and decreasing SF content is a feasible way to prepare RPC. In this paper, the hydration and microstructure of RPC composition containing SS, UFFA and SF were studied by X-ray diffraction, Thermo-gravimetric Analysis and SEM in order to gain a better understanding of the influence of temperature and duration on hydration and microstructure. Samples having undergone heat treatment at temperatures between 20°C and 90°C were investigated. Influence of temperature on hydration and pozzolanic reaction were examined. The results indicated that the amount of Ca (OH)2 remained in paste and the percentage of bound water by total water content both were highly dependent on heat treatment temperature and duration. This was mainly attributed to the activation of pozzolanic reaction with heat treatment and the sequential hydration effect of the compound cementitious system containing SF, SS and UFFA. The sequential hydration of compound cementitious system continuously consumed Ca(OH)2. Meanwhile the amount of hydration products was also growing, and thus the microstructure of compound system became increasingly compact, which was verified by SEM analysis.