A New Classification Method for High-Volume Fly Ash: Performance Based on Coal Source and Particle Size.

This study investigates the impact of particle size in fly ash derived from different coal sources on the performance of fly ash-cement systems. Utilizing a newly developed flotation classification method, physical properties of fly ash were examined to reveal variations among different particle sizes and coal sources. Thermal analysis was employed to analyze the calcium hydroxide content's effect on the cement system, while selective dissolution methods were used to assess reaction rates. XRD analysis confirmed particle size effects. Results indicate that flotation classification optimizes the properties of fly ash, enhancing activity and flow values, where some of the ash fractions exhibit overall superior properties. The use of high-volume fly ash (50% fly ash replacement) promotes continued pozzolanic reactions, especially with smaller particle sizes. Reaction rates decrease with larger particle sizes, emphasizing the importance of classification. XRD analysis further supports these findings, revealing that smaller particle sizes favor cement hydration and pozzolanic reactions. Overall, this study provides insights into optimizing fly ash properties for enhanced concrete performance.