A design-oriented stress-strain model for CFRP-confined fully replaced coal gangue aggregate concrete square columns

Coal gangue is a solid industrial waste generated during coal mining or utilization processes. This study takes coal gangue solid waste as the coarse aggregate in concrete. Using the concrete strength grade, fiber content, and number of carbon fiber-reinforced polymer (CFRP) layers as variables, cube and cylinder compression tests are conducted to understand the load-bearing performance of these components, providing theoretical support for their engineering application. The experimental results indicate the following: (1) As the number of CFRP layers increases, the specimens exhibit an excellent plastic deformation ability, and all feature point values are effectively improved. (2) As the fiber content increases, the load-bearing performance of the specimens gradually improves, but the efficiency enhancement rate decreases; thus, it is suggested to take a value of 0.5 %. (3) An increase in the concrete strength grade decreases the magnitude of improvement in the column force performance but is positively correlated with the Stage III slope in the stress-strain curve. (4) The stress-strain curve can be significantly divided into three stages, which is related to the excellent deformation ability of fiberreinforced coal gangue aggregate concrete. Based on the experimental results and theoretical analysis, feature point models and stress-strain curve models are established.