Post-Cracking Flexural Performance of HTPP Fiber-Reinforced EPS Concrete and Its Application to Wind-Loaded Exterior Wall Panels

Expanded polystyrene concrete (EPSC) offers low density and thermal insulation but is limited by brittle flexural failure. This study evaluates whether high-toughness modified polypropylene (HTPP) fibers can improve the post-cracking response of EPSC and translate the material-level gains into exterior wall-panel design under wind loading. Six mixtures containing 0, 0.3, 0.6, 0.9, 1.2, and 1.5 vol% HTPP fibers were prepared. Compressive tests, four-point bending tests, and scanning electron microscopy were conducted. Flexural toughness was assessed using average residual flexural strength together with the Nemkumar, literature-based, JSCE-SF4, and modified PCER methods. The mechanical indices generally increased and then declined as fiber content rose, with the best overall performance at 0.9 vol%. Relative to plain EPSC, this mixture increased compressive strength by 21.5%, flexural strength by 277.2%, and average residual flexural strength by 681.3%. The four toughness evaluation approaches produced consistent trends and showed that HTPP fibers most strongly improved post-peak load retention and energy absorption. Microscopic observations indicated that fiber bridging, crack-path deflection, stress transfer, and interfacial energy dissipation contributed to the enhanced toughness, whereas excessive fiber addition reduced the benefits. Using the measured residual capacity in a wind-load design model showed that HTPP fiber reinforcement can enlarge the allowable unsupported span of EPSC exterior wall panels. These findings identify an effective fiber dosage and provide a basis for the structural use of lightweight EPSC panels.