Abstract: The hydration process of red mud-based cementing material is studied by NMR and IR means and by structural analysis method. The effect of Ca/Si ratio of red mud cementing material on the solidification performance of Na+ of hydration product is disclosed. The results show that with the decrease of Ca/Si Ratio, along with the substitution of Al for Si, the structural unit polymerization degree of ［Si(Al)O₄］increases and ［SiO₄］and ［AlO₄］tetrahedra increase. Consequently, the C-S-H gel where Si occurs in Q¹ and Q² forms turns into (Na, Al)-C-S-H gel with SiQ² , SiQ³ and SiQ⁴ structural units, benefiting the solidification of Na+ in forms of chemical adsorption and chemical sosoloid.

Key words: Red mud-based cementing material, solidification of Na⁺, Ca/Si Ratio