Utilisation of alkali activated glass powder in binary mixtures with Portland cement, slag, fly ash and hydrated lime

This paper evaluates feasibility of alkali activation to boost the reactivity and cementitious properties of recycled glass powder (GP), when it is used in four different binary mixtures with ordinary Portland cement (OPC), alkali activated slag or fly ash, and calcium hydroxide. It is found that the detrimental effect of alkaline solution on hydration of OPC could not be compensated by enhancement of the reactivity of GP. By optimized mixture design and preferably elevated temperature of curing, a positive performance of glass powder in alkali activated slag–GP and fly ash–GP mortars was achieved, where high volume of GP can be effectively utilized. SEM/EDS analysis confirmed that GP increases the silica content of the hydration (geopolymerization) products of slag (C–A–S–H) and fly ash (N–A–S–H). Proper design of GP–CH binders and use of high molarities of NaOH solution can results in formation of calcium–silicate–hydrate products with a composition close to tobermorite, which can provide moderate compressive strength of mortars (21 MPa at 28 days) based on CH–GP binder. Finally, GP particles were observed to not cause alkali silica reaction (ASR) expansion in alkali activated systems.