Tensile Strength of Cemented Paste Backfill

The tensile strength is an important parameter in the design and analysis of cemented paste backfill (CPB) for underground mining. Although traditional axisymmetric dogbone-shaped specimens have been used to directly determine the tensile strength of rocks and concretes, such methods are not practical for CPB because of its much lower strength and associated difficulties in shaping the specimens. To determine the tensile strength of CPB, a castable rectangular dogbone specimen is developed, the apparatus including a compression to tension load converter, and a four-part split mold. The designed apparatus is validated using numerical analysis and shown through testing applications to be relatively simple, practical, and reliable. Results illustrate that the primary design allows the direct determination of tensile strength and characterization of the stress-strain behavior of isotropic materials. The stress-strain behavior could be reliably correlated with unconfined compression strength test results. The data show how the tensile strength is dependent on curing time and cement content. These results can lead to better mine backfill designs that fundamentally improve the underground mine stability.