Experimental Study and Analysis-Oriented Model of FRP-Confined Coal Gangue Aggregate Concrete

Coal gangue， a solid byproduct continuously generated during mining operations， can be utilized to replace natural aggregates in concrete， forming coal gangue aggregate concrete （CGAC）. This application addresses the environmental pollution caused by gangue stockpiling and mitigates the scarcity of natural aggregates. To compensate for the reduction in the mechanical properties of concrete resulting from replacing conventional aggregates with coal gangue， fiber-reinforced polymer （FRP） confinement can be employed to enhance the axial compressive strength of CGAC. In this study， the effects of three parameters were investigated： the coal gangue replacement ratio by volume （0% and 50%）， the FRP fabric type （glass fiber and carbon fiber）， and the number of FRP confinement layers （1 to 6 layers）. A total of eighteen specimens were tested under axial compression to compare the stress-strain relationships of CGAC confined with different types of FRP. Experimental results indicated that FRP-confined CGAC exhibited characteristics similar to those of FRP-confined conventional concrete. Under sufficient confinement， the load-displacement response demonstrated a distinct two-stage ascending behavior. However， the enhancement effect on the axial compressive strength gradually diminished as the confinement stiffness increased significantly. Finally， based on the experimental findings， an analytical model for FRP-confined CGAC was developed using a three-dimensional graphical representation approach.