Extensive evaluation on the effect of glass powder on the rheology, strength, and microstructure of metakaolin-based geopolymer binders

The current study aims to investigate the rheological, mechanical and microstructural characteristics of different geopolymer pastes derived from metakaolin (MK) and glass powder (GP) as precursors as well as sodium silicate and sodium hydroxide as alkaline reagent. An algorithmic mixture design approach was proposed by considering the important chemical and physical factors related to the precursor powders and alkaline reagents. Three combination groups containing 100% MK, 75% MK + 25% GP and 50% MK + 50% GP were designed by targeting different chemical and physical ratios of SiO2/Al2O3, Na2O/ SiO2 and liquid/solid. For a sustainable, energy efficient and practical solution, the ambient temperature was considered during the entire process of preparation and curing. Rheological properties, mechanical performance and microstructural analysis were investigated on the developed 44 geopolymer mixtures. The results showed that the rheological characteristics of MK based geopolymers were not affected by the addition of GP in their compositions. All produced pastes yielded shear-thinning or pseudoplastic behavior with decreased viscosity versus shear rate. Additionally, up to 25% GP replacement levels by MK, geopolymer pastes obtained equal compressive strengths to that of 100% MK. The SEM micrographs and EDS analyses showed the formation of NASH as the main reaction product in GP and MK-based geopolymers. (C) 2020 Elsevier Ltd. All rights reserved.