Effect of cordierite addition on compressive strength and thermal stability of metakaolin based geopolymer

Abstract

Metakaolin based geopolymer composites have been synthesized at room temperature by mixing metakaolin with NaOH and sodium silicate solutions, then adding cordierite powder from 0 to 50wt% as a weight fraction of geopolymer matrix. Compressive strength was measured after aged 28days. The thermal stability was analyzed by placing cube specimens in the furnace at 800°C for 2h. The compressive strength of cordierite-metakaolin based geopolymer composites was studied in comparison with those without cordierite addition. In this study, the compressive strength showed an increase with cordierite addition (from 0 to 30wt%), whereas the molar ratio SiO2/Al2O3=3.5 and H2O/Na2O=13, the strength increased from 45MPa to 57MPa. The microstructure revealed the unreacted metakaolin phase dispersed in the dense geopolymer matrix corresponding with the XRD results. It is evident that cordierite content in metakaolin based geopolymers can provide the good thermal stability at high temperature. Thermal shock resistance of 50wt% cordierite added to geopolymers at 800°C attained 15 cycles without cracking, although, the residual compressive strength was declined. Cordierite-metakaolin based geopolymer composites could be considered as a good candidate for high temperature refractory applications.