Study on the role of n-SiO2 incorporation in thermo-mechanical and microstructural properties of ambient cured FA-GGBS geopolymer matrix

Highlights: • A significant improvement in the compressive strength was found both the ambient and elevated temperature (200 °C–800 °C) in the FA/GGBS(80/20) geopolymer with the addition of 2.5 weight % of Nano silica. • Incorporation of Nano silica improves the microstructure wiht the increased geopoymerica reaction products as well the geopolymeric gel. • In situ ATR-FTIR spectaoscopic results showed the enhancement of dissolution of silicous layer from fly ash at the early stage of 24 h. The effect of Nano silica (seed) addition on the early period of geopolymer formation in the alkali mediated FA + GGBS reaction, was analyzed by Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Experimentation on different dosages of NS (0–3%), in the 80% FA and 20% GGBS (precursor material) activated through NaOH and Na₂SiO₃ (MR:1.1). The seed (NS) added in the system triggering the nucleation that reduce the induction period by formation of more geo polymeric gel in the early period of 12–72 h that was evident from ATR-FTIR results and it was pronounced at the NS dose of 2.5% that yield rapid increase in strength development to an extend of 50% gain as curing age increased from 1 day to 3 days, thereafter at slower rate upto 365 days. The weight change and strength characteristics of mortars after heat treatment in the temperature range of 30–800 °C studied showed that seeded mortar did not show any visible cracks/deterioration. Thermal conductivity and thermal stability using TGA/DTA and SEM microscopic examination studied.