Compressive properties and post‐peak response of polyoxymethylene fiber‐reinforced shotcrete

Abstract To investigate the effects of polyoxymethylene fibers (PMF) on the compressive mechanical properties and post‐peak response of shotcrete, six groups of polyoxymethylene fiber‐reinforced shotcrete (PMF‐SC) specimens with different fiber lengths and contents were designed. Through cubic compressive strength tests, the failure modes, workability, cubic compressive strength, and load–displacement responses of PMF‐SC were systematically analyzed. The results show that PMF can effectively improve the structural integrity of shotcrete after compressive failure. The cubic compressive strength of PMF‐SC exhibits a threshold effect with the variation of fiber parameters. Within an appropriate range, fibers enhance stress transfer and inhibit crack propagation by forming an effective bridging network; however, excessive fiber length or content lead to agglomeration and uneven distribution, which introduce internal defects and weaken mechanical performance. This threshold effect reflects the competition between the positive crack‐bridging effect of fibers and the negative influence of structural inhomogeneity caused by fiber agglomeration. The addition of PMF shortened the pore compaction stage of the load–displacement curve and moderated the post‐peak softening stage, thereby improving the deformation capacity and residual load‐bearing behavior of shotcrete. A modified equivalent compressive strength, ductility‐related and residual load‐bearing indices were calculated from the compression load–displacement curves to characterize the post‐peak compressive response of PMF‐SC under the same testing configuration. Furthermore, the deformation energy and residual load‐bearing indices indicate that appropriate PMF incorporation improves deformation energy dissipation and residual load‐bearing behavior under compression. Among the investigated mixtures, the group with fiber parameters of 36 mm and 7 kg/m 3 showed the most favorable overall compressive performance under the present experimental conditions.