Comparison of shear and pull-off tests for testing adhesion of different content limestone fillers mortars used as repair system

When a repair operation is performed and a new concrete or mortar is applied on the old concrete substrate, it is very important to have a good bond between the old concrete layer and the repair concrete system. The bond strengths usually determinate using pure tensile tests (pull-off tests) because of the field applicability of this category of tests. However, in most of the applications, shear stress is the main reason of the bond failure. In general, bond strength under tensile is considered smaller than bond strength in shear stress conditions.
The objective of this paper is to compare the results obtained from tensile and shear tests and to potentially determine a mathematical relation between shear and tension. The materials used for tests are Ordinary Portland Cement and modified limestone fillers mortars. Specific humidity storage conditions have been selected.