Fire Related Temperature Resistance of Fly Ash Based Geopolymer Mortar

Abstract

The study presented in this paper is on the effect of heat treatment on fly ash based geopolymer mortar synthesized from fly ash (Class F –Low lime) using alkaline binary activator solution containing sodium hydroxide (18 M) and sodium silicate solution (MR 2.0), cured at 80oC for 24 h. 7 days aged specimen heated at elevated temperature (200°C, 400°C, 600°C and 800°C) for the sustained period of 2hrs. The TGA/DTA analysis and thermal conductivity measurement as per ASTM C113 were carried out besides the compressive strengths. The thermal stability of the fly ash mortar at elevated temperature was found to be high as reflected in the observed value of f800°C/f30°C being more than 1 and this ratio was raised to about 1.3 with the addition of 2% Zirconium di oxide (ZrO2). No visible cracks were found on the specimens with and without ZrO2 when 800°C was sustained for 4 hrs in smaller specimens of size: 50 mm diameter x 100 mm height and in also bigger size specimens: 22 cm × 11 cm × 7 cm) specimens. TGA/DTA analysis of the geopolymer paste showed that the retention of mass was around 90%. The addition of ZrO2 improved thermal resistance. The micro structure of the matrix found to be intact even at elevated temperature that was evident from the FESEM studies.