Effect of Synthesis Parameters on Fresh and Hardened Properties of Slag-Waste Glass Binary Geopolymer

Waste glass is a major constituent in municipal solid waste, containing significant amount of silica (55-72%). Its potential usage in geopolymer production contributes to waste reduction and promotes the development of sustainable binders. The current study aims to investigate the influence of different glass power (GP) contents (0%, 10%, 20%, 30%, and 40%) on fresh and hardened properties of slag-GP binary geopolymer at different sodium hydroxide (NaOH) concentrations (2-10 M) and liquid alkali activator-to-solid binder (L/S) ratios (0.25-0.45). The workability and setting period of geopolymer were reduced with increased GP content and NaOH concentration. The flow diameter was reduced by 26.57%, and the final setting period was shortened by 56 min when GP content was increased from 0 to 40% at 6 M NaOH concentration. Based on 28-day compressive strength (CS), an optimum NaOH concentration of 8 M and an optimum L/S ratio of 0.35 was observed. With GP inclusion, the NaOH requirement was reduced by up to 50% due the availability of alkali cations in GP. However, at higher GP contents (> 20%), the rise of Si/Al, Na/Al, and Si/Ca molar ratios beyond their ideal range causes a low CS in slag-GP geopolymer. The resistance to soundness and drying shrinkage improved as GP content increased. The main reaction products observed in slag-GP geopolymers are C-S-H, C-A-S-H, N-A-S-H, and N-A-S. A non-linear statistical model developed with GP content, alkali concentration, and L/S ratio as input variables predicts the CS with an R-square of 0.9072.