Synergistic Effects of RHA, UFA, and GGBS on Physical, Rheological, Mechanical Properties of Alkali-Activated Grouting Material

Alkali-activated grouting material is a promising grouting material. This study developed a solid waste alkali-activated grouting material using rice husk ash (RHA), ultrafine fly ash (UFA) and ground granulated blast-furnace slag (GGBS), which has the advantages of low carbon, good fluidity, and high early strength. The synergistic effects of RHA, UFA, and GGBS on the physical properties, rheological behavior, mechanical performance, reaction process, and microstructure of the grouting material were systematically investigated. The incorporation of 5% RHA, 5% UFA increased the 28-day compressive strength of GGBS-based alkali-activated grouting material by 19.9% and decreased the 28-day water absorption rate by 42.5%. The addition of RHA, UFA increased the proportion of gel pores (3–10 nm) by 9% and decreased the proportions of capillary and macropore (>100 nm) by 5%. The combined use of RHA, UFA, and GGBS improves the slurry workability, increases the content of the Si-O bond, and promotes the alkali-activated reaction. Finally, the optimal proportions of RHA, UFA, and GGBS were determined, 5%, 5%, and 90%, respectively. This work can provide references for the proportion design of high-performance grouting material.