This study introduces a method to increase the load transfer capacity of a fully grouted rock bolting system by adding small amounts of rigid particles into the grouting material. The additive works via a keying effect to enhance the shear resistance of bond slip. The bonding effect of admixture grout was examined by common bolting assemblages under different confinement levels. The average increment of the peak load of the bond is approximately 14% and the average increment of energy absorption is approximately 70% compared to normal bolting. The load–displacement curves for grout with additive showed high irregularity. Furthermore, no conclusions can yet be drawn to quantify the effect of the admixture grout with respect to the confinement level. The admixture grout also provides a possible means to reduce gloving significantly by generating extra shredding force and broadening the shredding range in the process of bolt installation.