Synthesis and characterization of geopolymer grout from fly ash class C

Typical grout material is made from ordinary Portland cement. This work focuses on feasibility of producing fly ash based geopolymer grouting material. Geopolymer based materials actually have several advantages but the improvement of their rheological performances remains a challenging task, as the raw materials, especially sodium silicate and metakaolin, do not have favorable properties and the main chemical admixtures used to optimize cement-based materials have not been found compatible. Considering the performances in both fresh and hardened states, a comprehensive study is necessary to develop a promising geopolymer based grout material. Fly ash allowed reducing the viscosity and increasing the setting time and the stabilizer provided the fresh mixes with better homogeneity and stability. Detailed morphological study of raw fly ash was performed in this work. Scanning electron microscopy shared the macrospehre and inner microsphere structure within fly ash micrographs. Curing condition and solids to liquid ratio is kept constant in this study. The different concentration of NaOH solution (10 M and 12 M) and sodium silicate-to-sodium hydroxide (Na₂SiO₃/NaOH) ratios (1.5, 2.0, 2.5 and 3.0) were used in the production of geopolymer.