Characterization of slag-based mix activated with hydrated lime of industrial grade: A short communication

Abstract

This study aims to evaluate the effectiveness of industrial-grade hydrated lime as the sole alkali activator in a one-part system. Despite prior researches highlighting the importance of calcium in alkali-activated concrete, our findings indicate that using only hydrated lime did not significantly enhance strength due to its limited impact on system pH compared to sodium-based activators. The highest strength was achieved with a silica fume content of 20 %, regardless of the proportion of hydrated lime, while exceeding 30 % silica fume content led to a reduction in strength. Notably, the combination of 30 % hydrated lime and 20 % silica fume yields the highest strength of 27.16 MPa at 28 days. The compressive strength was particularly influenced by the CaO/SiO2 ratio, with higher ratios associated with higher strength. Higher hydrated lime content promoted the formation of colloidal Ca(OH)2, resulting in additional C-S-H gels with [SiO3]-2 from silica fume. Microstructural analysis revealed a prevalence of CSH gel over CASH polymeric gel, indicating that pozzolanic reactions were more dominant than the polymerization process, leading to the production of mixtures with low-to-medium strength.