Utilization of products from aqueous mineral carbonation of industrial residues as supplementary cementitious materials

The rising demand for low-carbon construction materials and the declining availability of traditional supplementary cementitious materials have driven interest in alternative substitutes. Alkaline industrial residues—such as incineration ashes, cement kiln dusts, and steel slags—are abundant but often unsuitable for direct use in cement due to unfavorable chemical and mineralogical compositions. This study investigates the CO 2 uptake and the potential of six such residues for partial cement replacement after treatment through aqueous mineral carbonation, using both direct carbonation in water and indirect carbonation in aqueous ammonium nitrate. Direct carbonation forms carbonates within the residues, while indirect carbonation produces two separate streams: a calcium-depleted leached residue and precipitated calcium carbonate. Mortars incorporating directly carbonated residues generally achieved higher compressive strength than those with fresh and leached residues, at 30 wt% cement replacement, likely due to calcite-induced nucleation and the pozzolanic reactivity of silica-rich gels. Although overall reactivity was limited—suggesting low to moderate clinker replacement potential—both aqueous carbonation routes removed or stabilized deleterious phases such as free lime, alkalis, and chlorides, expanding the potential use of these residues in construction, either as cement substitutes or fine fillers. Leaching tests revealed changes in hazardous element mobility, with implications for regulatory classification. Market analysis showed that while the cement sector could absorb suitable supplementary cementitious materials at moderate replacement levels, the limited demand for high-purity precipitated calcium carbonate constrains indirect carbonation to select feedstocks. This study provides a comparative framework for integrating mineral carbonation products into construction, which would enable CO 2 storage and resource circularity.