Evaluation of Bond Properties in Concrete Repair Materials

Bond quality is an important factor that affects the performance of repaired members. In patching repair, interfacial cracking and delamination due to the shrinkage of repair materials are often observed. In this study, flexural bond strength tests using jointed specimens were carried out, and the tension softening diagrams were determined by using experimental load-CMOD curves. These tension softening diagrams were adopted as the bond properties in numerical analyses to predict shrinkage and cracking behavior. For crack injection repair, bond strength tests based on the Japanese Industrial Standard (JIS) were carried out under conditions that are different from those normally encountered in the field (i.e. the tests involved smaller specimens, smoother surfaces, and finer grained materials). The bond properties of crack injection materials were evaluated using tension-softening diagrams. Size effect on flexural bond strength of repair materials was observed and clarified by numerical analysis with these tension softening diagrams. The analyses indicate size effect should be considered when evaluating the strength of larger structures in the field.