Performance of polypropylene fiber in compacted residual soil for pavement applications

Growing infrastructure demands necessitate cost-effective alternatives to conventional soil stabilization methods that often involve high energy consumption and environmental impacts. Therefore, this study contributes to the existing body of knowledge by investigating the performance enhancement of residual soil using discrete and strand polypropylene fibers for road subgrade and fill applications, addressing the need for alternative materials to conventional stabilization methods. Laboratory testing was conducted on soil specimens reinforced with varying Fiber contents (0.6-3.0%) and lime content (8%). California Bearing Ratio (CBR) and Indirect Tensile Strength (ITS) tests assessed fundamental mechanical properties, while large-scale model tests in a wooden steel-braced box (460 × 410 × 1000 mm) evaluated static and dynamic load responses under simulated field conditions. CBR improvements of 25.05% and 19.13% were achieved for discrete and strand Fibers, respectively, under unsoaked conditions. ITS tests revealed maximum tensile strengths of 37.45 kPa at 1.8% strand Fiber content and 30.8 kPa at 2.4% discrete Fiber content. Static bearing capacity at 25–50 mm settlement improved with 1.8–2.4% strand and 3.0% discrete Fiber reinforcement. Dynamic loading tests showed that unreinforced and lime-stabilized soils exhibited higher initial stiffness through 250 loading cycles. However, beyond this threshold, fiber-reinforced specimens demonstrated a better performance due to enhanced ductility, with 1.8% discrete Fiber reinforcement showing minimal cumulative settlement. Contrary to theoretical expectations, fiber-lime combinations did not demonstrate synergistic benefits. Lime-stabilized pavement section has a lower cumulative settlement than discrete and strand fibers under equivalent loading cycles. These findings provide practical guidance for field engineers when selecting appropriate reinforcement strategies for various loading conditions and performance requirements in unpaved road applications.