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

Abstract

Metakaolin (MK) and waterglass (WG) with a modulus of 1.3 were mixed to prepare MK-based geopolymer grouting materials (MKGPGM) with different alkalinity (concentration of sodium oxide in modified WG by mass of MK 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 showed that the main gel products were sodium silicoaluminate hydrate gels. Gypsum and ettringite were not detected in the specimens. The MKGPGM showed slight expansion first, followed by a micro-shrinkage. When the mass concentration of sodium oxide was 12 wt%, the maximum expansion rate was less than 0.12%. The MKGPGM showed a small increase in mass, essentially unchanged compressive strength and good anti-sulfate corrosion performance.