Study On Fracture Performance And Engineering Application Of Adherence Of New And Old Concrete

This paper is a part of the country s grave foundational research subject (climbing project B) and country s natural science fund item (59778045) <> .Studying the adherence performance and engineering application technique of new and old concrete has became the key problem of repairing and strengthening concrete structure, and has been the grave research subject for safety and durability of concrete structure in civil and water conservancy engineering domain.Based on the existed research results, the fracture performance and engineering application on adherence of young on old concrete are studied by means of the theory and method of concrete fracture. Finally, the suggestions on repairing and strengthening of concrete structure are offered.The main contents of this paper are as follows:1. The fracture test results of 87 adhesive specimens of new and old concrete are presented. The failure patterns and main influencing factors of the specimens are discussed and analyzed, such as interfacial roughness, types of adhesive agent, size of the aggregate, adhesive ages of new and old concrete. The test results show that, the fracture properties of adherence of new and old concrete are evidence lower than the new concrete itself. The suggestions on repairing and strengthening of concrete structure are offered.2. Based on the adhesive fracture test results of new and old concrete with the three point bending test method, the main influence factors of the adhesive fracture toughness are analyzed by means of the square-residual method. The multi-factor formula of adhesive fracture toughness is put forward, which will give the reference to the repairing and strengthening of concrete structures.3. The micro-mechanism of adherence of new and old concrete is analyzed using the failure micro-mode of concrete. The results show that, the interfacial bonding strength of new and old concrete is evidence lower than the new or old concrete itself. Besides the dimension and roughness of bond interface, the chemical reaction degree at the interface is also the main factor. In the same time, according to the fracture test results, the influence mechanism of aggregate size on fracture toughness of adherence of new and old concrete is discussed and analyzed, which is verified by manse of the fractal theory.4. The influence of interfacial micro-crack point of new and old concrete oninadhesive fracture toughness is discussed. A banded micro-crack fracture process zone model of adherence of new and old concrete is built up. According to the test result of load ~ strain, the adhesive fracture toughness is modified.5. The micro-crack fracture expansive process of adherence of new and old concrete is analyzed by means of chaos theory. The result shows that the stable extension, bifurcate and unstable extension of original micro-crack fracture is coincidence with model of the stationary state zone, bifurcate zone and chaos zone of double periodic bifurcate theory of chaos.6. Based on abroad and domestic treating methods for the interfacial roughness of new and old concrete, a cutting-groove treating method and a roughness-rate assessing method for the interfacial roughness of new and old concrete are presented, which is simple and suitable for treating large interfacial roughness. This roughness-rate assessing method is internally equal to the sand-pouring method. In the same time, this method has been used to repairing a concrete pavement, and the practice proves that the proposal method is suitable and effective.