Experimental research on load-shear performance of interface between new and old concrete with corroded planting bar

Thus far, a lot of concrete structures have been aging owing to the rapid development of highways, railways, and the construction industry in China. Concrete structure diseases, such as concrete surface cracks and erosion, require serious consideration due to the effect of long-term use and environmental impact. Some man-made factors have exacerbated these problems, such as insufficient operating level and corners, among others. This has obscured safety risks associated with these concrete structures. However, not all of these structures could not be decommissioned to reduce the negative social and economic impact and to ensure the safety of buildings; therefore, a reasonable approach was to repair and reinforce the old concrete structures. Additionally, in the process of maintenance and reinforcement, planting bars between the new and old concrete must be considered, and especially the corroded planting bar from an aged project that has been terminated. Many studies for the bonding performance of new and old concrete have been conducted by the experts and scholars at home and abroad; thereby, some results have been achieved. Only a few scholars have investigated the bonding performance between new and old concrete with planting bars and especially corroded planting bars from old reconstruction projects that have been terminated. Therefore, investigating the shear performance of new and old concrete with corroded planting bars was of utmost importance. To study the mechanical properties of the interface between new and old concrete with corroded planting bars, the new and old concrete specimens with different planting bar ratios (0%, 0.223%, 0.446%, 0.502%, 0.893%, 1.004%, 1.396%,1.786%, and 2.792%) were prepared based on the corroded planting bars. These corroded planting bars came from the tunnel lining structure of a project that had been terminated for over five years. Shear tests were conducted for new and old concrete under different initial static pressures (0-4 MPa) in an RYL-600 microcomputer control servo rock shear rheometer. The evolution law of the deformation and destruction of new and old concrete specimens under the action of external forces was obtained through summarizing the shear stresses and displacement curves of the specimens. The law of shear strength along with the variation of the steel planting ratio, as well as the initial pressure, were acquired by analyzing the shear strength of the new and old concrete interface with corroded planting bars. Moreover, the influence of different planting bar ratios and the initial pressure on the failure mode of concrete specimens was analyzed emphatically based on specimen failure results. The test results provided the theoretical basis for investigating the mechanical performance of new and old concrete.