The aim of this study was to solve the problems of low retention rate and poor grouting effect caused by the strong slurry fluidity of traditional cement-based grouting materials in deep backfill strata. Metakaolin-cement-based materials were used as raw materials to examine the dispersion of nano-boron carbide (B4C) using a laser particle size distribution instrument. Nano-B4C was used as a modifier to perform rheological and macroscopic mechanical tests. The effect of nano-B4C dispersion on the performance of the cement-based composite grouting materials was analyzed. The modified materials were further characterized via microscopic tests, and the grouting modification mechanism was revealed. The results showed that the agglomeration of nano-B4C with poor dispersion resulted in an increase in the fluidity of the grouting material, a decrease in viscosity, and a decrease in early strength. The well-dispersed nano-B4C effectively improved the viscosity and early strength of the grouting material and decreased the fluidity, and the change range increased with increasing nano-B4C content. The performance of the modified grouting material was superior to that of the traditional grouting material. The results present new solutions to problems, such as poor grouting effects in deep backfill soil strata.
