Mechanical Performance, Statistical Optimization, and Environmental Impact of Roller-Compacted Concrete Reinforced with Waste and Industrial Fibers

This study evaluates the multi-physical effects of fiber type, length, and dosage on the fresh properties, mechanical performance, and environmental impact of roller-compacted concrete (RCC). Industrial steel (S), polypropylene (PP), and waste steel (WS) fibers with lengths of 30 mm and 60 mm were incorporated into RCC mixtures at volume fractions ranging from 0% to 1.25%. The experimental program included Vebe consistency tests, mechanical strength assessments, and fracture energy measurements, complemented by a simplified cradle-to-gate Global Warming Potential (GWP) analysis. Furthermore, Taguchi and ANOVA methods were employed to statistically determine the hierarchy of influential parameters. The statistical analysis revealed that fiber dosage was the most dominant factor, contributing approximately 68–78% to the variation in compressive, splitting tensile, and flexural strengths, whereas fiber type governed the consistency. Experimentally, S and WS fibers significantly enhanced the post-cracking behavior and fracture energy compared to the brittle control mix, although they imposed a greater penalty on workability than PP fibers. Notably, at comparable dosages, WS fibers exhibited mechanical interlock and toughness performance nearly identical to industrial steel fibers. The environmental analysis demonstrated that replacing industrial steel fibers with WS fibers reduces the embodied carbon by approximately 240 kgCO2-eq/m3 at the maximum dosage, without compromising mechanical reliability. These findings suggest that waste steel fibers offer a superior performance-to-carbon ratio, making them a viable sustainable alternative for heavy-duty RCC pavements where crack control is prioritized.