Study on the shearing mechanical behavior and damage model of the polymer grouting material-concrete contact surface

The polymer grouting material (PU) has been increasingly used in trenchless repair of concrete pipes and roadbeds. Investigating the mechanical behavior of the PU-concrete (P-C) contact surfaces provides a basis for further evaluating the stability of the reinforced concrete structures, which, however, has not been conducted yet. In this study, based on the shear testing results, the mechanical properties and cracking characteristics of the P-C contact surfaces were investigated, followed by establishing the damage model. Results show that the cohesion force of the P-C contact surface increases from 0.42 MPa to 1.44 MPa when the density of the PU materials increases, and there exists residual strength when normal stress is applied. The shear failure of the P-C contact surface is caused by the shearing zone, of which the thickness is about 9-10 mm. The theoretical shear stress-strain curves of the P-C contact surfaces are in good agreement with the experimental ones. The maximum relative difference between the theoretical and experimental shear strength is about 4.2%, implying that the damage model can reflect the stress-strain laws of the P-C contact surfaces under shear.