Investigation of Microstructure and Thermomechanical Properties of Nano-TiO2 Admixed Geopolymer for Thermal Resistance Applications

Abstract

In this study, the effect of nano-TiO2 on the thermomechanical properties of fly ash-based geopolymer prepared by using alkali activator solution in an SiO2/Na2O ratio of 1.1, cured at 80ºC for 24 h, is investigated. The integrity of geopolymer mortars at an elevated temperature was determined by estimating the retention of compressive strength and weight loss of sample subjected to elevated temperatures (30–800°C). Analytical tests such as x-ray diffraction (XRD), attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR), dilatometry and thermogravimetric and differential thermal analysis (TGA/DTA) were performed on the geopolymer to ascertain structural and phase changes when the geopolymer is subjected to higher temperatures up to 800ºC. We observed that 2% n-TiO2 admixed mortars (M2) showed enhanced engineering properties at all temperatures studied. TGA/DTA studies confirmed the thermal stability of geopolymers up to 1200°C and the major mass loss occurs due to evaporation of water below 200°C. The mass loss was 7% for M2 and 12% for the control mortars (M1). The thermal expansion values are 1.1% for M1 and 0.04% for M2, respectively. This negligible thermal expansion value for M2 indicated the matrix thermal compatibility between the gel and aggregate to be good so as to retain structural integrity. n-TiO2 stimulates the nucleating sites during gel formation reaction by increasing the dissolution of Si4+ and Al3+ from the original fly ash, resulting in the generation of more amount of binding gel, as confirmed by ATR-FT-IR, XRD and SEM analysis, which may be the reason for the increase in the material’s strength on adding n-TiO2. Fly ash-based geopolymers can therefore be used as a fire-resistant binder, and fire resistance can be further enhanced by addition of n-TiO2. So these binders have a great potential for fire-resistant construction applications.