Performance evaluation of glass powder as a partial precursor in alkali-activated slag (AAS) binder and recycled glass and steel fibers in AAS mortar

Abstract

To reduce environmental impacts such as landfill waste from glass and tire fibers and to develop sustainable, low-carbon construction materials, this study explores the use of waste glass powder as a precursor in alkali-activated slag (AAS) binders and the recycling of glass particles and tire steel fibers in AAS mortar. The effects of glass powder (GP) as a precursor replacement were compared with those of a control and class F fly ash (FA)-modified AAS binder. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed that GP and FA promote geopolymer formation due to the dissolution of quartz. Nitrogen absorption tests indicated a slight increase in geopolymerization phases with GP replacement, consistent with SEM results and the compressive strength of the AAS binder. In the binder tests, the control AAS binder exhibited the highest compressive strength, while GP-modified samples outperformed FA replacements. GP-modified binders also extended setting times and reduced alkali leaching by over 30 % compared to the control. In mortar systems, replacing natural sand with recycled glass sand (GS) increased 28-day compressive strength by approximately 5.1 %, while adding recycled tire steel fiber (RTSF) improved compressive strength by up to 9.1 %, splitting tensile strength by 30 %, and flexural strength by 2.5 % compared to non-reinforced mixes. Sustainability analysis indicated that using GP as a partial precursor in AAS binders can reduce CO₂ emissions by nearly 5 % compared to normal AAS samples. This study uniquely compares GP and FA as partial precursors and introduces an integrated approach by simultaneously incorporating recycled glass sand and RTSF in mortars, thereby enhancing the mechanical properties, durability, and sustainability of AAS materials.