Parametric analysis of the production of alternative sodium silicate applied in alkali-activated materials

Although alkali-activated materials are considered potential substitutes for Portland cement, they still present elevated costs and significant emissions of CO₂. One way to partially overcome this disadvantage is the development of alternative activators, such as a sodium silicate based on the dissolution of rice husk ash (RHA). However, to maximize the mechanical performance of alkali-activated materials, the production of RHA-based sodium silicates needs to be fully understood. This article investigates the production process of an alternative RHA-based sodium silicate activator through the experimental evaluation of the following parameters: RHA grinding time, RHA dissolution time, thermal curing temperature and time. The mechanical performance was evaluated through compressive strength tests carried out on alkali-activated pastes made up of metakaolin, as a precursor, and two types of activators (RHA-based sodium silicate and commercial sodium silicate). Microstructural features were evaluated by performing X-Ray Diffraction, Scanning Electron Microscopy, and Thermogravimetry analyses. The optimized production was obtained for a grinding time of 30 minutes, a thermal curing temperature of 40°C, a dissolution time of 6 hours, and a thermal curing time of 8 hours. The results show the efficiency of the alternative alkaline activator, which may represent a technically viable solution for the larger-scale application of alkali-activated materials.