Effects of composition and activator type on glass-based geopolymers

The alkali activation of 17 waste glass streams from across the United States were investigated to explore the effects of glass chemical composition on compressive strength development. The effect of the activator composition was also explored; each glass was activated with both 10M NaOH and a 1:1 mass ratio of 10M NaOH and sodium silicate. All mortars were cured for 24 hours at 80°C and then kept in ambient conditions. Compressive strength was measured on mortar cubes over 56 days. The inclusion of sodium silicate in the activator intensified the effects of compositional variations within the glasses at 1 day and led to a strength increase in nearly all mixtures. Residual strength at 56 days was highest when the silica to alumina (S/A) and alkali to alumina (M/A) molar ratios were lowest. Higher ratios led to significant leaching and strength loss, especially when the M/A was over 4.