Effect of the use of waste glass (as precursor, and alkali activator) in the manufacture of geopolymer rendering mortars and architectural tiles

Abstract

The environmental impact of construction demolition wastes (CDW) is high since it represents between 45 and 65 % of the solid wastes that reach landfills. These wastes can be concrete, bricks, ceramic, wood, glass, plastic, metals, and others. Specifically, the glass wastes are considered 100 % recyclable, nevertheless, in the United States it is estimated that the recycling rate is only 33.1 %, compared to the European average of 42.6 %. In this research, the use of waste glass in the synthesis of geopolymers from different precursors such as brick wastes (BW), ceramic tiles wastes (CW) and metakaolin (MK) was evaluated. Glass wastes were studied as: (i) precursor, (ii) alkaline activator and (iii) fine aggregate (FG). The results showed that, in the pastes, the best strength is reached when they are made with SS alkali activator, reaching compressive strength above 25 MPa; in pastes with 50 wt% glass as precursor reaches strength up to 15 MPa, but when using 100 wt% glass as solid activator the strength does not exceed 1 MPa. Calorimetry results showed that the use of glass (at 25 °C) does not release enough heat. The formation of hybrid reaction gels (N,CASH) were identified in the CW-SS activated pastes. However, in the mortars made with G and FG, an improvement in strength was found compared to their respective pastes, which is attributed to the fact that the microns G particles that did not react with the alkaline activation can act as fillers, allowing them to support higher loads. Finally, mortars with strengths of ∼10–15 MPa were successfully applied as render mortar and in the elaboration of architectonic tiles.