Study On The Mechanics Performance Of Adherence Of Young On Old Concrete

The repair and strengthening of concrete structure has become an important engineering domain. The enlarging section method (the reinforcement and strengthening technique of integral type of young on old concrete) is widely applied in the repair and strengthening of concrete structure. Therefore, the research of adherence of young on old concrete has profound significance. This paper studied the mechanics performance of adherence of young on old concrete. The main results are summarized as follows: 1. The adhesive splitting tensile test is an indirect method to evaluate the tensile strength. But the adhesive direct strength is required to know in engineering. This paper got the relation formula between them tbro ugh tests. So, through the portable adhesive splitting tensile test, the adhesive direct tensile strength can be achieved from the relation formula. 2. The higher adhesive strength can be gotten through the water-jet method. By comparison, the adhesive strength gotten by the method of chipping with hammers is lower. After used these two methods to treat the surfaces of old concrete, the adhesive splitting tensile tests are performed on the bonding specimens. From the test results, the difference of their adhesive performance is gotten. 3. The bonding specimens are heated up to 200 0C. After that, the adhesive splitting tensile strength is achieved by tests. Compared with the strength gotten in normal temperature, the reason of the difference resulted from the effect of high temperature is analyzed. 4. Three main factors affecting the adhesion performance are selected to make orthogonal design, which are the age of new concrete~. the variety of new concrete and the roughness. By adhesive splitting tensile strength as index mark to analyze variance, the degrees of effect of each factor are gotten. 5. The shrinkage of various new concrete restrained by old concrete is different. Three kinds of new concrete: ordinary concrete~ steel fiber ?Ill ? concrete (steel fiber 1%) and steel fiber concrete (steel fiber 1.5%) are selected to make the adhesion specimens. After measured the restrained shrinkage of the specimens in four months, the corresponding curves of restrained shrinkage on the sites of new concrete are concluded. 6. When the shrinkage of new concrete is restrained by old concrete, the tensile stresses can be created in the interior of new concrete. Through founded the mechanics model of restrained shrinkage, the stresses and strains in the new concrete are studied. Compared with the results of measurement, the model is proved to be approprite and effective. 7. By the tests of compression-shear and tension-shear, the effects of compressive stresses (or tensile stresses) and roughness to the adhesion performance are analyzed, the formulas of failure strength under combined stresses are founded, and the relations of shear stress-slip of the interface under combined stresses are Studied. 8. By the tests of compression-compression-shear and tension-compression- shear, the effects of vertical compressive stresses (or vertical tensile stresses)~. parallel compressive stresses and roughness to the adhesion performance are analyzed, the formulas of failure strength under such...