High-Volume Mineral Admixtures Cement: The Effects of Particle Size Distribution

The effects of high-volume slag-fly ash cement with different particle sizes on hydration degree, microstructure and mechanical properties were systematically studied, by means of laser particle size (DLS), X-ray diffraction (XRD), comprehensive thermal analysis (TG-DTA), scanning electron microscopy (SEM) and mechanical properties tests. The results show that suitable particle size distribution of cementitious material has significantly promoting effects on hydration reaction rate and mechanical properties. Compared with slag without further grinding, the slag after ball milling for 4 h has an obvious improvement in reactivity, which also provides a faster hydration rate and higher compressive strength for the cementitious material. When the slag milled for 1 and 4 h is mixed at a mass ratio of 2:1 (i e, slag with D₅₀ of 7.4 µm and average size of 9.9 µm, and slag with D₅₀ value of 2.6 µm and average size of 5.3 µm), and a certain amount of fly ash is added in, the most obvious improvement of compressive strength of cement is achieved.