Experimental study on bond behavior between SMPM and concrete using dual-beam speckle interferometry

Abstract

Steel stranded wire mesh and polymer mortar (SMPM) is a novel technique for structural strengthening. To study the still unknown bond behavior between SMPM composites and concrete, the dual-beam speckle interferometry with four-step phase-shifting is used in double-shear tests. Displacements of SMPM composites are obtained by unwrapping the phase pattern due to deformation, and derivation of the displacements results in the strains. Twenty-five specimens were tested with different strengthening parameters to investigate their influences on the bond behavior. It is found that the measured strain distributions are different from those in fiber-reinforced polymer (FRP) sheets, but are similar to the bond strains existed in the FRP-concrete interface. Locations of transversal wires have a significant influence on the strain distributions and the debonding loads. The maximum displacements before brittle debonding occurs are about an order of magnitude smaller than those of FRP composites. According to the test data, a bond strength model is developed to predict the debonding loads, in which a number of factors, such as interfacial roughness, concrete strength, and locations of transversal wires, etc., are taken into account. A three segment stress—displacement relationship is proposed to describe the debonding behavior of SMPM composites.