Shear bond testing of concrete repairs

Abstract

Good adhesion of a repair material to concrete is of vital importance in the application and performance of concrete repairs. This paper reviews and compares techniques and results of bond strength test methods that induce shear, including a tensile slant-shear test. The effect of surface preparation (particularly as it affects roughness and soundness) and modulus mismatch between repair and substrate are illustrated by experimental and theoretical data. While these tests can provide individually useful information on bond strength and a limited picture of bond characteristics, they can, taken in isolation, result in a misunderstanding of the behaviour of bonded cementitious materials. A more complete appreciation can be obtained by consideration of a bond failure envelope that encompasses all possible normal/shear stress states. Such an envelope is presented in the context of Mohr-Coulomb and Griffith's fracture criteria.