Influence of elevated temperatures on the mechanical properties of foamed geopolymer materials

Abstract

Current research focuses heavily on geopolymer concrete as possible applications for insulation materials. The aim of the research is to test the strength properties of lightweight geopolymer concrete after exposure to high temperatures. Waste material from the Wieczorek mine (Poland) was used to produce the foamed geopolymers. Alkaline activation took place by mixing the mine powder with an aqueous solution of sodium hydroxide combined with an aqueous sodium silicate with a concentration of 10 M. Prepared geopolymer samples after temperature curing at 75 °C for 24 hours in a laboratory dryer, they were seasoned for 28 days, after which the strength properties were determined. Mechanical tests: compressive strength and bending strength were carried out at temperatures: 20 °C, 200 °C, 600 °C, 800 °C, 1100 °C. Research has shown the precursor activation with the presence of hydrogen peroxide enabled the manufacturing of foamed geopolymers. Heating in the temperature range up to 1100 °C influenced, to some extent, the total porosity of the tested foams. The geopolymer foams based on coal gangue present stable mechanical properties in the range up to 800 °C. No sharp mechanical performances decrease or material chipping was observed. Only colour change of heated samples occurred.