Thermal Performance of Ferrocement Slabs Reinforced with Recycled PET Fibers

Abstract This study aimed to identify the optimal ratio of polyethylene terephthalate (PET) fibers to enhance the structural performance of ferrocement slabs, particularly under varying high-temperature conditions. The research examines the effects of PET fibers on the hardened properties of ferrocement mortar, as well as how both PET fibers and elevated temperatures (25 °C, 100 °C, 200 °C, 400 °C, and 600 °C) influence the impact and mechanical behavior of the material. To achieve this, four volumetric proportions of PET fibers (0%, 0.5%, 0.75%, and 1%) were first used to identify the optimum PET content, which was found to be 0.75%. The impact and mechanical behavior of ferrocement slabs were then investigated using the optimized mix. To evaluate the impact behavior, a total of 25 two-way slabs of 500 mm × 500 mm × 50 mm were prepared and tested. The parameters were (a) fiber content (0% and 0.75%), (b) layers of steel wire mesh reinforcement (0, 2, and 4 layers), and (c) elevated temperatures (25 °C, 100 °C, 200 °C, 400 °C, and 600 °C). These were organized to have five different slab configurations: zero reinforcement layer (0L) and zero fiber (0F) (0L-0F); 2L-0F, 4L-0F, 2L-0.75F, and 4L-0.75F. Each of these slabs was tested under the five selected elevated temperatures, making the 25 specimens needed. The same parameters were repeated to evaluate the flexural behavior of ferrocement slabs using 25 one-way slabs with dimensions of 1200 mm × 150 mm × 50 mm. The results indicated that PET fibers decreased density and ultrasonic pulse velocity while increasing water absorption. At a PET fiber content of 0.75%, the compressive and flexural strengths increased by 17.85% and 5.79%, respectively, after 28 days. Strength loss was minimal up to 200 °C, but significant reductions were observed beyond 400 °C. The optimal performance was found in slabs with 0.75% PET and two layers of reinforcement at 200 °C, displaying improved flexural strength, toughness, and ductility. At 600 °C, the breakdown of the plastic fibers resulted in a substantial performance decline. Overall, the findings show that PET fibers enhance ferrocement performance up to 400 °C but experience degradation at higher temperatures.