Experimental Study on the Bond-Slip Behavior of Steel-Steel Fiber Recycled Aggregate Concrete

To study the bond–slip behavior of steel–steel fiber recycled aggregate concrete, push-out tests of 16 specimens were carried out using steel fiber volume ratio, steel fiber aspect ratio, steel protective layer thickness and steel embedded length as the design parameters. In addition, the crack patterns, steel strain distribution, and load–slip curves were studied, in addition to the bond strengths of the interface between the steel–steel fiber and recycled aggregate concrete. The results showed that the fracture cracks of the specimens mainly included bond cracks and expansion cracks. For the load increase stage, the maximum strain of the steel flange was near the loading end of the steel and decreased toward the free end, while the strain changed linearly for the load descending stage. The bond–slip process between the steel–steel fiber and recycled aggregate concrete included five stages, which consisted of slight-slip, slow-slip, accelerated-slip, the sharp-slip and load-steep-drop stage, and gentle-slip stage. Additionally, the influencing factors of bond strength were analyzed, where the bond strength increased first and then decreased with increasing steel fiber volume and steel fiber aspect ratios, and the bond strength increased with increasing steel protective layer thickness. The ultimate bond strength decreased slightly with increasing steel embedded length. Finally, the equation for calculating the characteristic bond strength of the steel–steel fiber recycled aggregate concrete was established, which showed that the calculation results were in good agreement with the test results.

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