Bond behavior between steel bar and coal gangue coarse aggregate concrete: Experimental and numerical investigation

Using coal gangue (CG) as coarse aggregate in concrete preparation has good economic and environmental benefits, thus the mechanical properties of CG coarse aggregate (CGCA) concrete and the structural performance of reinforced concrete members made of CGCA have been investigated in various studies. However, the research on the bond behavior of ribbed steel bar in CGCA concrete is very limited, which hinders the application of this CGCA concrete. Therefore, in this paper, 36 center pull-out specimens were tested with the parameters of concrete strength grade (C30, C40 and C55), CGCA replacement ratio (0 %, 30 %, 50 %, 70 % and 100 %), and rebar diameter (16 mm and 25 mm). The test results demonstrated that with the increase of CGCA replacement ratio, the failure mode of center pull-out specimen transformed from pull-out failure to splitting failure, and the bond strength decreased by 9.9–50.7 %. Based on the test results presented herein, a prediction model for the bond strength of reinforced CGCA concrete members was proposed and its accuracy was verified. Finally, a meso-scale finite element model of crescent-shaped steel bar and CGCA concrete was established, and its reliability was verified by comparing with the test results in this paper. On this basis, the failure mechanism of crescent-shaped steel bar and CGCA concrete under pull-out force was investigated.