Comparative study of geopolymer binder and mortars made from thermally activated termite soils and kaolinitic clay: mechanical performance and microstructure

With the widespread use of geopolymer, the effective activation and utilization of thermally activated termite soils as alternative or eco-friendly material are great of interest. The present study investigated the use of calcined termite soils (TC) in geopolymer pastes and mortars as a precursor, while metakaolin (MK) was used as a reference material to prepare control samples. The physicochemical properties of both raw and calcined solid precursors as well as geopolymer pastes and mortars were characterized using various techniques, including BET, PSD, XRF, XRD, setting time, ICC, and SEM/EDS. Results showed that termite soil can be successfully employed as a starting material in geopolymer production. Pastes and mortars prepared using TC gave significant compressive strengths of 43.2 and 33.2 MPa, respectively, although they were approximately 26% and 6% lower than control samples made using MK. Based on the analytical studies, better mechanical performance of MK-based binders compared to TC-based ones is attributed to the presence of reactive phases within MK that promotes the geopolymerization resulting in the development of a stronger geopolymer network and better connectivity within the matrix. It can be concluded that TC can be considered as a suitable raw material for the production of geopolymer binder considering the availability and accessibility in certain regions.