Influence of Calcium Carbonate Whiskers on the Mechanical and Fatigue Properties of Polyethylene Fiber–Reinforced Cementitious Composites

To investigate the influence of calcium carbonate whisker (CW) content on the mechanical properties of polyethylene fiber-reinforced engineered cementitious composites (PE-ECC), uniaxial compression tests, axial tensile tests, and axial tensile fatigue tests were conducted on five groups of PE-ECC specimens with varying CW volume fractions (0%, 0.5%, 1%, 2%, and 3%). The variations in compressive, tensile, and fatigue properties were systematically analyzed. The experimental results demonstrated that an appropriate amount of CW significantly enhanced the mechanical performance of PE-ECC by bridging and deflecting microcracks within the matrix. With increasing CW content, the compressive strength, tensile strength, and initial cracking strength of PE-ECC exhibited a trend of initial increase followed by a decline, with the optimal CW content identified as 1%. At this content, the compressive strength, tensile strength, and initial cracking strength of PE-ECC increased by 14.91%, 19.58%, and 31.31%, respectively, compared to the CW-free group. Furthermore, the tensile fatigue life of PE-ECC peaked at 1% CW content (93,665 cycles, representing a 32.29% improvement over the baseline group). However, excessive CW content (>1%) led to fiber agglomeration, increased matrix porosity, and microcrack proliferation, resulting in mechanical degradation. Microstructural analysis revealed that an optimal CW content enabled uniform dispersion within the matrix and formed a synergistic reinforcement network with polyethylene fibers, whereas excessive CW caused reduced dispersion and exacerbated interfacial defects. This study provides a theoretical foundation for the optimized design and engineering applications of PE-ECC.