Eco-friendly treatment of low-calcium coal fly ash for high pozzolanic reactivity: A step towards waste utilization in sustainable building material

Fly ash is a coal combustion by-product with low pozzolanic reactivity which limits its resource utilization and engineering properties in building materials. The present study investigates a wet-milling treatment to activate the coal fly ash and promote its sustainable utilization. It was found that wet-milling is a suitable, efficient and eco-friendly technology for solid waste refinement. The pozzolanic reactivity is greatly improved after wet-milling treatment, as high as 140% at 60 days with particle size of 2.51 μm. It was observed that ettringite formation has occurred during the wet-milling. Physical structure, chemical evolution and ion leaching behavior during the wet-milling were discussed. It was proved that activation mechanism of wet-milling is a combined effect of physical breakage and ion dissolution acceleration. Binding energy was found decreased and SiQn structural units were found less polymerized which are helpful for the depolymerization during the pozzolanic reaction. Furthermore, technical applicability of wet-milling for various industrial solid wastes was also investigated.