Performance of sustainable cementitious mortar incorporating hybrid waste glass powder and steel slag

The use of waste glass powder (WGP) and steel slag (SS) in cementitious materials not only reduces the disposal costs of industrial solid waste, decreases greenhouse gas emissions, and conserves natural raw materials, but also improves the performance of mortar and concrete. There is limited research on exploration of WGP and SS as simultaneous replacements for cement and fine aggregates. In this study, three different particle sizes of WGP were used to replace 20 % of the cement by mass, and SS was used to replace 20 % of the river sand by volume in mortar. The effects of WGP alone and the combined replacement of WGP and SS on the flowability, hydration process, mechanical properties, microstructure, and durability were evaluated. The results indicate that when the particle size of WGP is relatively small (D[50] ≤ 9.2μm), its strong pozzolanic activity of WGP contributes to higher strength and a lower chloride migration coefficient in the blended mortar. SS further enhances the pozzolanic reaction of WGP, which is macroscopically reflected in a strength increase of the blended mortar (SS-GP-Ⅲ) during the later curing age (120 days), with a 10.6 % increase in compressive strength and a 49.9 % increase in flexural strength. This is attributed to more hydration products and a more compact microstructural morphology. This finding identifies the unique contributions of the synergy between WGP and SS on the mechanical properties and durability of cementitious mortar. • WGP fails to compensate for the early age strength loss from cement replacement. • WGP with a smaller particle size exhibits higher pozzolanic activity. • The porous and rough surface of SS facilitates enhanced bonding with binder materials. • The hybrid addition of WGP and SS fine aggregate makes the performance better.