Interfacial bond performance between self-expansion polymer and concrete.

• The effect of polymer density and interfacial moisture on the bond behavior was evaluated. • Correlation between bond strength and microstructural features was analyzed. • Bond mechanism between self-expansion polymer and concrete was characterized. Polymer grouting technology is a new trenchless method to restore leakage and subsidence of underground concrete structures, and the bond between polymer and concrete is critical to estimate the deformation and ultimate conditions of the repaired structures. In this paper, scanning electron microscopy (SEM) and a series of direct shear tests were used to evaluate the interfacial bond properties between self-expansion polymer and concrete. Based on the test results, the effect of polymer density, the strength of concrete, the moisture content of grouting interface before and after grouting on interfacial microstructure, failure mode, shear stress-slip curves, and bond capacity were evaluated and discussed. The results demonstrated that the polymer could infiltrate into the pores of the concrete grouting surface, the infiltrate value and the polymer strength increased with the amount of grouting and resulted in large bond strength. Pre-moistened the grouting surface reduce the polymer migration into the irregularities of the concrete substrate and affect chemical reactions, show un-full filled pores of the interface and increased the diameter of the polymer cells around the interface, which is thought to exerts a negative influence on the bond behavior. [ABSTRACT FROM AUTHOR]