Towards the development of an in situ non-destructive method to control the quality of concrete-to-concrete interfaces

In structural concrete codes, the design expression to assess the shear strength of concrete-to-concrete interfaces is based on the “shear-friction theory”. In these, the shear strength is highly dependent on the surface roughness of the concrete substrate. Recent studies have focused in the texture characterization of concrete surfaces and some in situ methods have been developed in this scope. However, with these methods the surface texture can only be assessed before applying the concrete overlay. In this paper, a study on the viability of developing a non-destructive test to assess the surface roughness of a concrete substrate after applying the overlay is presented. An ultrasound-based method was considered and the Boundary Elements and Finite Differences Methods were chosen to simulate two-layer slabs with different materials and interface textures. Experimental tests were also conducted to validate the numerical results. It was concluded that an ultrasound based method can be used to characterize the interface texture of homogeneous two-layer slabs but further research is needed for heterogeneous materials, such as concrete.