Axial compressive behavior of basalt and carbon FRP-confined coal gangue concrete

Abstract

Coal gangue concrete (CGC), in which fine and coarse aggregates are completely replaced by coal gangue aggregates, has been limited to non-structural applications owing to its brittle structure, lower strength and stiffness. Nevertheless, the disadvantages of CGC can be minimized by external confinement of fiber-reinforced polymer (FRP) jacket. A total of 39 cylindrical specimens were studied under a monotonic axial compression test to understand the compressive behavior of FRP-confined CGC, considering the CGC strength, FRP layer number, basalt FRP (BFRP) and carbon FRP (CFRP) type as variables. The failure modes, stress–strain relationship, and dilation properties were analyzed in detail. The results indicate that the strength of the BFRP/CFRP-confined CGC was improved by 16.9%–145.8%, and the axial ultimate strain was 4.787–8.812 times that of the plain CGC. The stress–strain curve of the BFRP/CFRP-confined specimen exhibited a bilinear response, where the second portion showed a descending shape under weak confinement and an ascending branch under strong confinement, mainly depending on the FRP confining ratio. Additionally, the axial strain of the confined CGC is larger than that of the confined normal concrete when given the same lateral strain. Most importantly, the modified discriminative models and ultimate strength and strain models for BFRP/CFRP-confined CGC were proposed, providing a theoretical basis for its application in mines.