Development of strain-hardening geopolymer mortar based on liquid-crystal display (LCD) glass and blast furnace slag

In this study, a strain-hardening geopolymer mortar, based on waste liquid-crystal display (LCD) glass and ground granulated blast furnace slag (GGBFS), was first developed by incorporating 2% polyethylene (PE) fibers. The influence of silica sand content on the packing density, porosity, fiber/matrix interfacial bond, compressive strength, and tensile performance of the geopolymer composites was also investigated. The test results indicated that the compressive and tensile strengths of the geopolymer increased with the addition of silica sand and by increasing its content up to a sand-to-binder (S/B) ratio of 1.0, which is related to the increased packing density. The total porosity of the geopolymer was insignificantly influenced by the silica sand (8.5%–9.15%), whereas the air voids and volumes of gel pores and mesopores were effectively decreased due to the addition of silica sand. However, the pseudo strain-hardening capability deteriorated when the silica sand content exceeded a certain value, that is, the S/B ratio of 0.3, causing significantly lower strain capacity and energy. The highest strain energy density of 227 kJ/m³ was achieved in the geopolymer mortar with the S/B ratio of 0.2, which is approximately 13% higher than that of the geopolymer paste. Both the strain capacity and energy absorption capacity were inversely correlated to the compressive strength, implying that achieving pseudo strain-hardening characteristics is more difficult for (ultra-) high-strength geopolymer composites than for normal-strength composites.