This thesis addresses the testing and evaluation of the use of a cementitious injection grout for the reattachment of detached slabbing on the sandstone support rock of Holly Tower at Hovenweep National Monument. This research follows on a previous condition assessment and diagnosis of the deterioration of the sandstone support rock and the effects of consolidation on the rock as the first step in a multi-phase conservation program. The extreme instability of the slabbing on the west side of the support rock requires remedial intervention that will retain and reattach the slab to the parent rock. Injection grouting was identified as a viable option for reattachment, requiring the development of an intensive testing regimen to determine the physical and mechanical properties of a commercial cementitious grout.