Unveiling the Carbon Footprint Reduction Potential of Cementitious Composites: CO₂ Sequestration in a Lime-Clay Binder Incorporating Medium-Grade Clay

Abstract

This study evaluated the effects of CO 2 sequestration on the strength development, microstructural characteristics, and environmental footprint of a lime-clay binder for marine applications. This binder was prepared by mixing medium-grade clay (55.75% kaolin content) with lime and incorporating seawater for mixing and curing. The samples were cured in a CO 2 -containing chamber at an early stage to promote the carbonation reaction. Carbonation promoted silica polymerization, resulting in geopolymer gel and calcite formation in the matrix. The compressive strength of the carbonated composites was 36% higher than that of the noncarbonated counterpart after 28 days of curing, accompanied by a noticeable decline in the chloride-binding capacity. Sequestering CO 2 in medium-grade clay-based binders can reduce the global warming potential (GWP) by 47−66% compared to ordinary portland cement (OPC); additionally, the combined effect of clay-based mortar components decreased the GWP by up to 40% relative to the GWP of the OPC mortar. This work underscores the potential of CO 2 sequestration and seawater use in enhancing lime-clay binder systems while highlighting major environmental benefits.