Thermal properties of metakaolin-based geopolymer modified by the silane coupling agent

Abstract

In this work, metakaolin-based geopolymer was modified by the silane coupling agent. The effect of the silane coupling agent on the thermal resistance of metakaolin-based geopolymer was studied by linear shrinkage, mechanical properties, fourier transform infrared spectroscopy, and scanning electron microscope testing methods. Results show that the addition of the silane coupling agent did not change the mineral composition and refine the pore size of the geopolymer, but an appropriate amount of addition can reduce the shrinkage of samples exposed to high temperatures. The specimens with 0.2 wt% silane coupling agent (SAMG-0.2) achieves the best performance when exposed to 200 °C. Meanwhile, compressive strength reached 65.1 MP and was 10.2% higher than pure metakaolin-based geopolymer. The compressive strength of SAMG-0.2 was higher than the reference group at each exposure temperature. The silanol group provided by the silane coupling agent reacts with geopolymer, enriching the gel phase of geopolymer and improving the stability under high temperatures.