Work

A carbon-sequestering cementitious binder: Synergistic mechanisms of carbonated steel slag and carbonated carbide slag on hydration and strength development

Year: 2026

Type: article

Abstract: The complementary use of carbonated carbide slag (CCS) and carbonated steel slag (CSS) enables substantial cement substitution, but their composition-driven hydration synergy remains unclear. In this study, CCS and CSS were incorporated individually and jointly into Portland cement (PC) at a fixed total replacement of 30 wt%, with systematically varied proportions. Isothermal calorimetry, Krstulović-Dabić kinetic modelling and pore-solution analysis showed that increasing CSS progressively redistributed hydration from strong early nucleation toward sustained later-stage reaction, balancing CaCO 3 -assisted nucleation with Si/Al-mediated dissolution-precipitation. At the optimum CCS10CSS20 composition, the 28-d TGA-derived apparent degree of hydration reached 92.63%, while monocarboaluminate increased to 17.40 wt%. The gel-associated Q 1 + Q 2 Al + Q 2 proportion reached 65.15%, compared with 52.47% in CCS30, indicating enhanced C-(A-)S-H formation and polymerization, accompanied by pore refinement. This evolution reflects the complementary roles of CCS-derived carbonate nucleation and the sustained chemical contribution of CSS-derived reactive Si and Al. These coupled changes increased the 1-d and 28-d compressive strengths by 26% and 82%, respectively, relative to CCS30, while maintaining a 36.5% CO 2 reduction relative to PC. The results establish a composition link among hydration kinetics, hydrate assemblage, structural evolution and strength, providing a mechanistic basis for optimizing composite cements.

Source: Cement and Concrete Research

DOI: 10.1016/j.cemconres.2026.108419