One-part geopolymer mixes from geothermal silica and sodium aluminate

At present, the most commonly used building material is ordinary Portland cement (OPC). However, OPC has a negative environmental effect during synthesis, with the release of significant amount of CO2 greenhouse gas. The cement industry is responsible for 5-8% of total global anthropogenic CO2 emissions. Geopolymerization is a technology capable of turning industrial wastes into strong and chemically durable cement-like binders, with significant Greenhouse emission savings. The synthesis of geopolymers can start from a variety of aluminosilicate sources such as fly ash or metakaolin. In geopolymer technology, alkali silicate solutions are frequently used to dissolve the solid aluminosilicate precursor to produce the binder. Sodium aluminate solutions have also been used. These corrosive and often viscous solutions are not user friendly, and would be difficult to use for bulk production. Developing geopolymers as a 1-part mixture (“just add water”) similar to OPC increases their commercial viability. Here, the geopolymer system consisting of geothermal silica and solid sodium aluminate (providing the solid silica, alkali and alumina sources), activated by addition of water, is studied. The effects of water content, high early silica and high early alumina in the formation of one part mix geopolymers are also investigated. XRD shows that the formulation with less water has an unexpected greater extent of crystallinity. It is also observed that a high early Al concentration inhibits geopolymerization, while a high early Si concentration enhances the reaction