Does the colour of the waste glass affect their efficiency as supplementary cementitious material?

Abstract

Glass from the solid urban waste is presented mainly in amber, green and transparent colour. Regarding their reactivity, several studies argue that there are differences among each colour when they are used as supplementary cementitious material. Nevertheless, the current literature lacks of an assessment of the significance of these differences from a practical perspective. On top of that, one of the problems for effective glass recycling is that they are mixed at the waste collection centres and the separation cost would be too expensive or even impossible. Considering the technological and the economical benefits of using the waste glass with no separation, the hypothesis assessed in this paper was that the colour of the glass is not statistically significant (ANOVA test). Blended cements replaced up to 30% shown stimulation of the hydration at 2 days (isothermal calorimetry) and the pozzolanic activity at 7 days (Frattini test). At 28 days, the development of the compressive strength with the pozzolanic supply of the glass powders, lead to equal or higher values than the control. The ANOVA and Tukey tests have shown that at 28 days neither each glass colour powder per se nor a mix of them are a significative variable for the development of the compressive strength performance of the mortars up to 30% of replacement.