Experimental study on interfacial damage mechanisms of polymer-concrete composite structure

Non-water reacting polymer as an effective repair material is extensively employed in trenchless rehabilitation of geotechnical engineering. The interface bonding characteristics of concrete-polymer structures greatly influence the service performance of the repaired structure. In this paper, direct shear tests of the polymer-concrete composite specimens were conducted. The interfacial damage and deformation process was studied using acoustic emission and digital image correlation techniques. The microstructure features of the polymer at the interface were analyzed by scanning electron microscope. Results show that the shear failure of polymer-concrete composite specimens mainly occurred at the interface, and acoustic emission activities existed throughout the failure process, mainly including three stages. The interface damage between polymer and concrete can be qualitatively predicted based on the rapid increase of accumulated acoustic emission ringing count and energy. The macroscopic observation shows that the interface damage started from the top of the concrete-polymer specimen with a density of 0.2 g/cm3, and expanded from top to bottom along with the interface until the specimen failed. In addition, the relative slip at the interface and its growth rate showed a decreasing trend from top to bottom while increasing with increasing acoustic emission parameters in the last stage. Furthermore, the interfacial failure of specimens mainly occurred in the cement mortar layer near the interface of the composite specimen.