Impact of synergistic use of chelator and fly ash/slag on properties and microstructure of CO₂-cured cement mortar

To achieve high-value utilization of industrial solid waste during CO₂ curing while simultaneously optimizing mineralization efficiency and microstructure, the effects of the synergistic use of chelator and fly ash/slag on the properties, microstructure, mineralization degree and mineralization products of CO₂-cured cement mortar were systematically investigated in this study. This work offered new insights into regulating pore structure and improving material properties through chelator-solid waste synergy. The results showed that the chelator-fly ash system significantly promoted early-stage mineralization but increased the proportion of pores larger than 0.1 μm, thereby reducing the mechanical strength and impermeability of the material. In contrast, the chelator-slag system further enhanced the mineralization degree, refined the microstructure, and improved both strength and durability. Compared to the control mortar cured for 48 h, the mortar containing 0.5 % chelator and 20 % slag exhibited an 18.9 % increase in carbon sequestration rate, a 35.2 % reduction in porosity of pores above 0.1 μm, a 21.8 % increase in compressive strength, and a 16.2 % decrease in chloride ion migration coefficient, demonstrating excellent synergistic performance.