Liquid-solid grinding system: Grinding kinetics of coal fly ash as ultrafine supplementary cementitious materials

Wet-milling in liquid-solid system can achieve ultra-fine mechanical dissociation of solid wastes with low energy consumption, thereby efficiently improving the potential pozzolanic reactivity. However, the wet-milling kinetics of ultrafine dissociation in liquid-solid system has not been fully investigated. This paper systematically investigates the wet-milling kinetics of fly ash (FA). Results showed that before wet-milling of FA for 360 min, no agglomeration effect was observed. The particle dissociation of FA during wet-milling can be divided into three stages: rapid dissociation, slow dissociation and stabilization. The evolution process of particle size distribution during wet-milling is consistent with the Rosin-Rammler-Bennet distribution. Both the particle uniformity coefficient and fractal dimension showed highly positive linear correlation with the strength activity index of wet-milled FA. The grey correlation analysis showed that FA particles between 1.1 and 3.1 μm had the greatest impact on both the early and late strength activity index. Simultaneously, D10 of wet-milled FA has the largest impact on strength activity index at each age, while D100 has the least impact. Therefore, D10 and proportion of particles in 1.1–3.1 μm can be an important basis for judging the reactivity of wet-milled FA as ultrafine supplementary cementitious materials.