Investigating the physical and chemical contribution of ground low-quality fly ash particles to cementitious composites

This work investigates grinding as a potential solution to improve the utilization of low-quality fly ashes in concrete. Factors contributing to the performance of ground fly ash in cementitious composites were investigated. Grinding significantly crushes large cenospheres particles and increases specific gravity and surface area of fly ash, which leads to higher filler effect and improves the rate of cement hydration contributing to strength development. The comparison of strength of quartz-blended pastes and fly ash-blended pastes showed that the pozzolanic reaction of fly ash marginally contributes to strength development. The major influence of ground particles was seen on the region near to aggregates. Ground fly ash significantly increased the microhardness of interfacial transition zone near aggregates. Since this zone has a direct influence on the failure of mortars and concrete, its improvement resulted in a comparable strength of fly ash-blended mortars to the reference OPC mortar.