Effects of waste glass as a sand replacement on the strength and durability of fly ash/GGBS based alkali activated mortar

This study incorporates fine waste glass (GS) as a replacement for natural sand (NS) in fly ash (FA) and/or ground granulated blast furnace slag (GGBS) based alkali activated mortar (AAm). Tests were conducted on the AAm to determine the mechanical properties, water absorption, apparent porosity and the durability based on its resistance to Na₂SO₄ 5% and H₂SO₄ 2% concentrated solutions. Whereas the microstructure and chemical composition of AAm was analyzed by SEM-EDX to support results obtained from the experimental tests. The study revealed that the effects of GS depends on the ratio of binders used to synthesize the mortar. For high FA/GGBS mortar, an increase in strength and reduction of porosity was observed with increasing GS up to 50 wt%. For lower FA/GGBS mortar, increasing GS up to 100 wt%, increased strength and decreased porosity. The lower porosity attained with the incorporation of GS, improved the resistance of mortar to Na₂SO₄ solution thus increasing durability. The resistance of mortar to H₂SO₄ was also improved with lower porosity due to incorporation of GS. However, the durability of mortar was negatively impacted with the further reduction of porosity observed with increasing GS and GGBS above 50 wt% believed to be caused by the stress induced as a result of expansive reaction products created when the mortar reacted with acid.