Study on the effect of ultrafine powder prepared by coactivation of ternary industrial solid waste on concrete properties

Addressing the dual challenges of high emissions and low utilization rates associated with industrial solid waste (ISW), this study pioneers a strategy for high-value resource recovery by developing a highly active ultrafine powder through the compounding and grinding of coal gasification slag, fly ash, and slag powder (mass ratio 2:3:5). The efficacy of this tri-component solid waste synergistic activator was evaluated by producing C50 concrete specimens with cement replacement levels of 0%, 10%, 20%, 30%, and 40%. Results demonstrate that while early (7-day) compressive strength decreases with increasing replacement ratio, a 10% ratio yields superior later-age strength. Notably, the 30% replacement ratio conferred optimal resistance to both carbonation and chloride ion penetration. Microstructural analyses (XRD, SEM) revealed that the ultrafine powder refines the pore structure of the hydration products, thereby enhancing the concrete's mechanical properties and durability. This approach presents significant potential for advancing the resource-efficient utilization of ISW and promoting green, low-carbon, and sustainable development within the construction sector. • Ternary waste coactivation : Coal slag/fly ash/slag powder (2:3:5) activated as ultrafine powder. • 30% cement replacement maximizes carbonation/chloride resistance in C50 concrete. • 10% replacement achieves superior long-term compressive strength. • XRD/SEM proves refined pore structure enhances durability & mechanics. • Waste-to-resource pathway cuts 40% cement use, advancing circular construction.