Synthesis of One-Part Geopolymer Mixes
Geopolymerisation is a technology capable of turning industrial wastes into strong and chemically durable cementitious binders. The synthesis of geopolymers can start from a variety of aluminosilicate sources such as fly ash or metakaolin. 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% of total global anthropogenic CO2 emissions.
In geopolymer technology, silicate solutions are frequently used in alkali activation for dissolving the aluminosilicate 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. In the present work geothermal silica and sodium aluminate are used as solid silica, alkali and alumina sources for the production of geopolymer cement.
X-ray diffraction is used to identify and characterize crystalline phases forming, however the main reaction product is X-ray amorphous. Results of attenuated total reflectance Fourier transform infrared spectroscopy indicate that the structure of the 1-part mix geopolymer cement is similar to that of geopolymer cement made from the alkali activation of fly ash. Strength testing and microstructural analysis are also performed to compare the two systems. Results indicate that by using solid silica and sodium aluminate it is possible to produce geopolymers in a 1-part mixture.