Toward waste glass upcycling: Preparation and characterization of high-volume waste glass geopolymer composites

Portland cement-free high-volume waste glass geopolymer composite is proposed for the upcycling of glass waste. The “high-volume” is achieved by utilizing GP as the geopolymer precursor and glass cullet as the aggregate. Our observations show decent strength and durability can be obtained by the composites with up to ∼83 wt% waste glass by the mass of solid components. GP and common geopolymer precursors (class C and class F fly ash and slag) have synergistic effects on forming calcium-(sodium-)aluminosilicate hydrate (C-(N-)A-S-H) and sodium-aluminosilicate hydrate (N-A-S-H). A higher Ca content and dosage of Na₂O, however, lead to a larger drying shrinkage. Although glass aggregate can reduce the shrinkage to some extent, the highly reactive aggregate may cause the progressive ASR in the Ca-rich mixtures. The ASR expansion decreases with the increasing dosage of Na₂O possibly because an overly high pH in pore solution thermodynamically hindered the precipitation of ASR gels and/or a higher alkaline concentration favors the dissolution of aggregate surfaces at curing stage, and the dissolved Si participates in the hydration process.