Microstructural insights and sustainable utilisation of nano-alumina content in geopolymer mortar

This experimental research investigates the effects of different nano-alumina (NA) percentages partially replaced with ground granulated blast slag (GGBS) and fly ash (FA) using a variety of tests, including compressive and flexural strengths, flowability, dry density, microstructural analysis (scanning electron microscope, energy dispersive spectrometer, thermogravimetry analysis), water absorption, and sorptivity at ages of 28 days. All mixture results were also contrasted with those obtained from a control mixture of 50% GGBS and 50% FA without NA. All of the mixtures had the same alkaline activator and solid base, and the proportion of sodium hydroxide solution (S.H)/sodium silicate solution (S.S) was 2.5; the molarity of S.H is 12 M. The aim of this research is to investigate the optimal percentages of NA that showed significant results. The mix containing 2% NA reached its maximum strength of 61.9 MPa at 28 days. The results show that the percentage of NA significantly influences alkali-activated mortar properties, including water absorption, which is affected differently at varying concentrations. The proposed alkali-activated mortar may offer stable substitutes for conventional building materials that are also environmentally friendly.