Abstract: A new type of grouting material is prepared by using soda residue and fly ash. The influence of the dosage of gypsum, a component together with sodium silicate in compound activator, on the setting time, fluidity, unconfined compressive strength, and freeze-thaw resistance of the slurry was examined. The influence regularity was expounded in association with SEM and XRD approaches. Results demonstrated that: with the increase of gypsum dosage, setting time shortened, fluidity declined, while compressive strength increased; on the contrary, before gypsum dosage reached 10%, the variation tendency of setting time and compressive strength was the opposite. The larger the proportion of gypsum, the greater the strength loss of the stone during freeze-thaw cycles, and such strength loss during the first five freeze-thaw cycles was the most remarkable and then tended to be stable. Ettringite was generated in the slurry system after the addition of gypsum. The research findings provide reference for the improvement and application of soda residue-fly ash grouting material.

Key words: soda residue, fly ash, grouting material, compound activation, gypsum