Study on Evaluation of Bond Performance of Concrete and Improvement

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In this study, we evaluated bond performance of concrete by using the tension softening diagrams in addition to the conventional flexural bond strength and improved the bond performance. The bond performance of joints under shear force as well as under tension forces was investigated. The fracture behavior of repair materials for concrete structures was analyzed through FEM with the tension softening diagrams.The concrete joint surfaces were roughened by means of a shot blast method, a water jet method and a wash out method with a paper sheet containing retarder. The roughness of the joint surfaces was quantified by using the power spectrum, the fractal dimension and the- total surface area. The bond performance of joints was evaluated through the flexural bond strength, the fracture energy and the shape of the tension softening diagrams. After the comparison of these parameters, it was concluded that the tension softening diagrams were efficient.The size effect on the flexural bond strength of concrete was investigated through experiments and numerical analysis. It was found that the size effect was remarkable when the bond performance at joints was poor.he shrinking and cracking behavior of repair materials for concrete structures was investigated. The cracking in repair materials and the delamination on the interfaces due to the shrinking were numerically analyzed and the results coincided with the experimental ones. The efficiency of the numerical analysis with tension softening diagrams at interfaces was confirmed. It was pointed out that the surface treatment at vertical joint surface (end surface of repair materials) was important because the treatment gave a large influence on the shrinking and cracking behavior of the repair materials.