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

Abstract

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.