Against the background of people’s increasing awareness of personal safety and property safety, the flame retardancy (FR) of materials has increasingly become the focus of attention in the field of construction engineering. A variety of materials have been developed in research and production in this field. Polymers have many advantages, such as their light weight, low water absorption, high flexibility, good chemical corrosion resistance, high specific strength, high specific modulus and low thermal conductivity, and are often applied to the field of construction engineering. However, the FR of unmodified polymer is not ideal, and new methods to make it more flame retardant are needed to enhance the FR. This article primarily introduces the flame-retardant mechanism of fire retardancy. It summarizes the preparation of polymer flame-retardant materials by adding different flame-retardant agents, and the application and research progress related to polymer flame-retardant materials in construction engineering.

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.