Performance of Polypropylene Fiber-Reinforced Mortar Exposed to Elevated Temperatures.

BACKGROUND: Cement-based materials deteriorate significantly when exposed to high temperatures due to extensive microcracking, increased porosity, and dehydration of hydration products, all of which lower the materials' mechanical performance and post-fire stability. This makes thermally robust mortar essential for protective applications in fire-prone areas as well as structural restoration. METHOD: The goal of this study is to assess how the amount of polypropylene (PP) fiber in cement mortar affects its mechanical behavior, thermal resistance, and residual performance at temperatures as high as 600°C. Prior to and following exposure to increased temperatures of 200, 400, and 600°C, mortar mixes containing 0%, 0.5%, 1.0%, and 1.5% PP fibers by volume were made and tested for workability, density, compressive strength, flexural strength, and flexural toughness. RESULTS: The results show that increasing PP fiber content decreases workability. PP fibers significantly improved high-temperature performance. At 600°C, the control mix retained only 19% of its compressive strength, while the 0.5% PP mix retained 33%. Flexural strength increased by 26-44% at ambient temperature for 0.5-1.0% PP fiber content, and at 600°C, PP mixes preserved up to 8% more flexural strength than the control. Toughness improved substantially, with the 1.5% PP mix showing nearly 10-time higher residual toughness than the control at 600°C. CONCLUSIONS: In conclusion, the incorporation of 0.5-1.0% polypropylene fibers provides a balanced enhancement in thermal resistance, residual strength and ductility, confirming its effectiveness in producing mortar with superior structural integrity after exposed to high temperatures.