Improvement in the unconfined compressive strength of sand test pieces cemented with calcium phosphate compound by addition of calcium carbonate

We added calcium carbonate (CC) powder to a novel grout made from calcium phosphate compound (CPC-chem) to increase the ground strength improvement afforded by CPC-chem. We conducted the unconfined compressive strength (UCS) test and scanning electron microscopy (SEM) observation on test pieces cemented with CPC-chem and CC powder. The UCS of test pieces cemented with CPC-chem and CC powder was significantly higher than that of test pieces cemented without CC powder, and it reached a maximum of 209.7 kPa. The UCS of test pieces cemented with CC powder and deionized water was 12.5 kPa, which was similar to that of test pieces cemented with deionized water only (10 kPa). SEM observation revealed mesh-like and three-dimensional structures in the segment of the test piece cemented with CPC-chem and 1 wt% of CC, which showed UCS of over 200 kPa and the minimum axial strain rate among all cases in this study. These results suggest that the addition of CC powder significantly enhances the ground improvement afforded by CPC-chem.

► UCS of test pieces cemented with CPC grout and calcium carbonate (CC) was measured. ► The maximum UCS of the sand test pieces cemented with CPC grout and CC was 209.7 kPa. ► A mesh-like structure was observed in test pieces cemented with CPC grout and 1% CC. ► These results suggest that CC addition effectively improves CPC grout performance.