Low-carbon ternary binder bio-composites via accelerated carbonation for circular construction

This study demonstrates the significance of coupling biomass valorization with accelerated carbonation curing (ACC) as an integrated strategy for low-carbon construction materials. A bio-based ternary binder incorporating wood sawdust with shale ash, steel slag, and a reduced proportion of ordinary Portland cement (OPC) was developed to simultaneously enhance mechanical performance and enable CO 2 sequestration. The optimized formulation (25% shale ash, 15% OPC, 10% slag, and 50% sawdust) achieved a compressive strength of 7.2 MPa and an elastic modulus of 6 GPa, exceeding the performance of comparable wood-cement composites while using substantially less clinker. Microstructural analyses (SEM, XRD, FTIR, and XPS) confirmed portlandite depletion and the formation of calcite and low-Ca/Si C-(A)-S-H phases under ACC, resulting in matrix densification. Life cycle assessment (EN 15804 +A2) indicated a 65% reduction in greenhouse gas emissions relative to OPC-based systems, highlighting the combined structural and environmental benefits of the proposed approach.