Development of cement-free strain-hardening slag composites: Impact of calcium hydroxide activation and dosage on microstructural and mechanical properties

This study evaluates the mechanical and environmental performance of strain-hardening slag composites (SHSCs) reinforced with polyethylene fibers. Ground granulated blast furnace slag (GGBFS) was activated with calcium hydroxide (Ca(OH)₂, CH), and silica fume was added to promote pozzolanic reactions. Mixtures containing up to 15% CH by weight of GGBFS were tested through chemical analyses, mechanical evaluations, digital image correlation, and life cycle assessment. Increasing CH dosage accelerated hydration, generating more reaction products and a denser silicate network. The mixture with 15% CH exhibited notable improvements in tensile performance including a tensile strength of 10.05 MPa, tensile strain capacity of 9.19%, and strain energy density of 664.9 kJ/m 3 , along with a clear pseudo-strain-hardening response. Environmentally, CH-activated SHSCs showed substantially lower CO₂ emissions and embodied energy than conventional strain-hardening cement composites and sodium-activated SHSCs. These findings highlight CH as an effective and sustainable activator for producing high-performance SHSCs with reduced environmental impact.