Polypropylene fiber assessment for achieving optimal toughness in sustainable tunnel lining selection with various concrete matrices

Abstract This study evaluates the performance of polypropylene (PP) fiber‐reinforced concrete mixes for tunnel‐lining applications, using four concrete types: pervious, moderate strength, high‐performance, and ultra‐high‐performance. The mixes incorporate fiber dosages up to 1.0% by volume, except for ultra‐high‐performance concrete, which includes up to 2.7%. Performance is assessed through flexural tests on 72 panels, following european standard (EN) 14488‐5 and American society for testing and materials (ASTM) 1550 standards. The findings show that fiber addition boosts energy absorption in pervious concrete, but volumes under 9 kg/m 3 (Vf‐1%) do not meet toughness criteria. A 24 kg/m 3 (Vf‐2.7%) fiber dosage also falls short, suggesting a need for a stronger matrix. Statistical analysis produced precise prediction equations ( R 2 >92%) for energy absorption, factoring in cementitious materials, water‐to‐cement ratio, fiber dosage, and aggregate ratio. These equations serve as valuable tools for predicting the performance of fiber‐reinforced concrete (FRC) mixtures based on concrete composition and fiber dosages. Notably, both square and round panel tests demonstrate a strong correlation ( R 2 = 94%) with respect to energy absorption capacity, with the square panel test exhibiting values approximately 2.5 times higher. Assessment of toughness levels, material cost, and CO 2 emissions is carried out from a sustainability perspective, with the optimal choice emphasized as the normal‐performance FRC matrix incorporating 9 kg of PP fiber.