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.