Effect of temperature on metakaolin-quartz powder geopolymer binder with different combinations of silicates and hydroxides

Abstract

Geopolymers have gained great attention from researchers because of their excellent mechanical properties. Recent studies indicated an increasing interest in the use of geopolymer materials in the construction industry due to their great potential to replace Portland cement-based materials or even produce binders to be used as adhesives in for structural repairs, besides being a promising ecological alternative. In this study, the metakaolin-quartz powder geopolymer binder (MQGB) reached compressive strengths greater than 80 MPa and tensile strengths between 5 and 6 MPa at 28 days. In addition to the tests performed at 28 days, other measurements were conducted at early ages (1, 3 and 14 days) and a high gain in the mechanical strength was observed. The ratio of compressive strength ranged from 55% to 60% on the first day, from 85% to 93% after 3 days and from 90% to 99% after 14 days in relation to the values obtained at 28 days. For samples exposed to high temperatures, the alkaline activator solution was determinant in the residual mechanical performance. The MQGB with potassium silicate presented better results than those prepared with alkaline sodium silicate and the commercial epoxy resin. The MQGB showed mass loss, as a function of temperature, which ranged from 11.15% to 16.41% and the commercial epoxy resin showed a higher value of 31.64%. These results indicate that metakaolin-quartz powder geopolymer binder manufactured with different combinations of silicates and hydroxides, proposed in this study, could be used as fire-resistant material in structural repairs.