Experimental and simulation study on mechanical properties of steel fiber coal gangue concrete

Abstract Coal gangue aggregate has high water absorption and a porous microstructure, both of which can reduce the mechanical performance of coal gangue concrete (CGC). This study examined whether hooked steel fibers can compensate for this strength loss and improve the mechanical behavior of steel fiber-reinforced coal gangue concrete (STCGC). Seven mixtures were prepared by varying the coal gangue replacement ratio (0%, 25%, 50%, and 75%) and, at 50% replacement, the steel fiber content (0%, 0.5%, 1.0%, and 1.5%). In total, 210 specimens were tested at 7 d, 14 d, and 28 d by cube compression, splitting tensile, axial compression, and elastic modulus tests. Scanning electron microscopy and ABAQUS mesoscopic simulation were used to interpret the failure mechanism and verify the compressive response. The results show that increasing coal gangue replacement reduces strength because of the porous and weak aggregate structure, whereas steel fibers improve crack resistance and post-cracking integrity. Compared with the 50% CGC mixture, steel fiber addition increased the average cube compressive strength, splitting tensile strength, axial compressive strength, and measured elastic modulus by 2.26%, 24.61%, 23.26%, and 59.47% (a mixture-specific result under the present test conditions; see Results for interpretation), respectively. Under the specific baseline of 50% coal gangue replacement, the 1.0% steel fiber mixture achieved the most balanced mechanical performance among the tested series Strength-conversion equations and stress-strain constitutive relationships were fitted for the tested mixtures. The simulated cube compressive strengths followed the experimental trend, indicating that the mesoscopic model can reproduce the compressive failure pattern of STCGC within the scope of the present mixtures. This study provides a test-calibrated basis for using steel fibers to improve the mechanical performance of coal gangue aggregate concrete.