Influence of mineralogy and activator type on the rheology behaviour and setting time of laterite based geopolymer paste

Abstract

Laterite soils are one of the promising aluminosilicate materials that can be utilized as precursors in the synthesis of geopolymers. However, it is critical to understand how the composition of the laterites and the type of activator influence the corresponding performance of geopolymer composites. Hence, this study was undertaken to evaluate the influence of mineralogy and activator type on the rheology, microstructure and performance of laterite-based geopolymers pastes. In this study, calcined laterite alongside an alkali and acid solution was utilized for geopolymer synthesis. The physical and chemical properties of the raw laterite, calcined laterite and geopolymer pastes were evaluated using Brunauer Emmett and Teller method, X-ray diffraction, fluorescence X analyses, quantitative Rietveld analysis and infrared spectroscopy. The fresh geopolymer pastes were assessed in terms of slump flow, setting time and rheological properties. Microstructural investigations alongside the evaluation of mechanical and permeability properties of the hardened geopolymer pastes were also carried out. The findings from this study showed that the fresh and hardened properties of laterite-based geopolymers are dependent on the mineralogy of the calcined laterite and the type of activator used. Geopolymer pastes synthesized using acidic solution exhibited a slower reaction than those made with an alkali solution. However, geopolymer pastes activated with an acidic solution exhibited higher mechanical performance and lower permeability compared to those synthesized with an alkali solution.