Study On Bond Capability Of Young And Old Concrete

At present,the study of adhesive performance of young and old concrete has gradually gone deeply into the fields of reinforcing and repairing.The adhesive strength of young and old concrete,which is lower than the strength of integral concreting structure,has great influence on the reliability of repaired structure and service life.As the development of the technology of planting reinforcing bar,mechanical joint element embedded in the adjoining faces between the old and new concrete can limit the open displacement of the combining surface,increase the bond strength,ensure that structure with cracks can work normally.However,there are few researches about the shear property,mechanism of shear transmission and bond failure of the young and old concrete surface,especially when limited by the size of the specimens and the conditions of test,we need to embed in several bars with different depth,ratio of reinforcing bar and arrangement of the bars.Following aspects of bond property of the young and old concrete are discussed in this paper:The roughness effects on the bond property of the young and old concrete has been analyzed in this paper and by using the digital imaging technology the method of shear friction coefficient calculation has deduced.We design 16 Z-cut specimens with 8 series,at the same time increased the size of the specimens to embed several bars,considering the effects of the diameter of the bars,ratio of reinforcing bar and arrangement of the bars.According to results of the test data,we analyze the effects of the different planting reinforcing bar parameters on the ultimate load and cracking load.Compared with the distribution of strain on the bars surface and the process of shear transmission on the bars with two arrangements,we gained the mechanism of Z-cut specimens shear transmission.Study the shear transfer mechanism of young and old concrete.