Pairing Chemical Activation and Carbonation of Basalt to Manufacture Novel Supplementary Cementitious Materials that Incorporate Carbon Capture

CO₂ capture and mineralization within the concrete industry, through supplementary cementitious materials (SCMs), offers an opportunity to meet both the UN’s climate goals and address dwindling global fly ash supplies. To address these issues, this study explores the high-energy attrition-milling of basaltic fines in a CO₂ atmosphere (named mechano-carbonation). This paper employs a suite of materials characterization techniques to determine the currently undocumented microstructural changes occurring throughout the mechano-carbonation process in basaltic fines. Addressing a critical gap in knowledge, this paper observes the agglomeration of particles, resulting in the increase of Dv(50) particle size by 12.5×, the increase in the BET surface area by 3.7×, and a decrease in XRD crystalline peak intensity by ∼50% across all major phases. Additionally, different milling conditions (250–500 rpm, 10–40 ball to powder ratios) are shown to impact the desirable properties of the produced SCM, with 500 rpm and a 40 b/p ratio increasing pozzolanic reactivity compared to plain basalt by 4-fold. This increase in rpm and b:p ratio also resulted in greater CO₂ sequestration potential, as evidenced by the formation of CaCO₃ in the form of calcite and aragonite, mineralized through CO₂ off-gassed from the resultant milling solution. These factors, when combined, resulted in an SCM with a 50% increase in CaCO₃ content (0.8 g per 100 g basalt) and an R3 pozzolanic reactivity similar to that of fly ash (∼160 J/gSCM).