Chemical deformation and mass change of metakaolin-based geopolymer grouting material in sulfate environment

In this study, metakaolin and waterglass with a modulus of 1.3 were mixed to prepare metakaolin based geopolymer grouting materials (MKGPGM) with different alkalinity of 11 wt%, 12 wt%, and 13 wt% The linear expansion, mass change, mechanical properties and microstructure of the specimens were investigated after being immersed in pure water and sodium sulfate solutions with a concentration of 1-4 wt% for 90 days. The results indicate that the main gel products were sodium silicoaluminate hydrate (N-A-S-H) gel, gypsum and ettringite were not detected in the specimens. The MKGPGM samples showed slight expansion first and then followed by a micro-shrinkage. When the mass concentration of Na2O is 12 wt%, the maximum expansion rate was less than 0.12%. MKGPGM samples showed a small increase in mass, essentially unchanged compressive strength and good anti- sulfate corrosion performance.