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 (ZrO 2 ). No visible cracks were found on the specimens with and without ZrO 2 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 ZrO 2 improved thermal resistance. The micro structure of the matrix found to be intact even at elevated temperature that was evident from the FESEM studies.
Highlights
Geopolymers (GPs) are systems of inorganic binders proposed by Prof Davidovits in 1970’s [1] have emerged as an alternative to Ordinary Portland cement, with superior strength, durability and environmental performances
The total chemical composition of Fly ash, alkaline activator solution used in the sample preparation with geopolymer mortar are given in the Table1 and Table 2
Fly ash mix with Zirconium di oxide at 2% is designated as FAGP2z
Summary
Geopolymers (GPs) are systems of inorganic binders proposed by Prof Davidovits in 1970’s [1] have emerged as an alternative to Ordinary Portland cement, with superior strength, durability and environmental performances. Geopolymer technology is opt for field applications in light of today’s burning issues, i.e. sustainability and need for reduction of greenhouse gas emissions from cement-based industries which is contributing to about 7% of world CO2 emission. These inorganic alumino-silicate polymers can be synthesized from alkali activation of any material rich in silica and alumina. Heat resistant properties of alkali activated fly ash were investigated by several workers [10-15] and geopolymeric paste indicated high shrinkage as well as large changes in compressive strength at elevated temperature in the range 800-1200°C. Alternate GSMs such as mine tailings, waste ceramics were tried and satisfactory thermo stable geopolymeric paste was obtained [16-17]
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