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/m3 (Vf-1%) do not meet toughness criteria. A 24 kg/m3 (Vf-2.7%) fiber dosage also falls short, suggesting a need for a stronger matrix. Statistical analysis produced precise prediction equations (R2 >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 (R2 = 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 CO2 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.