Ultra-high toughness green engineered cementitious composites with recycled hybrid fiber design: Mechanical properties and environmental performance

This study investigates the feasibility of utilizing recycled fibers in developing green ultra-high toughness engineered cementitious composites (ECC). Uniaxial tensile tests were conducted to investigate the effect of three types of recycled fibers (carbon fiber, basalt fiber, and polypropylene fiber) on the tensile performance of ECC at a constant total fiber volume fraction of 2.0 %. Virgin polyethylene fibers (PEF) were partially replaced by recycled fibers at volume replacement ratios of 25 %, 50 %, and 75 % to investigate the effects of fiber type and replacement ratio. Experimental results demonstrate that compressive strength decreases with increasing recycled fiber content. Hybridizing recycled fibers with virgin fibers can produce ultra-high toughness ECC exhibiting strain-hardening behavior and saturated multiple cracking characteristics. Among all recycled fiber reinforced ECC mixtures, the specimen with 0.5 vol% recycled polypropylene fiber and 1.5 vol% virgin polyethylene fibers (PEF1.5RPPF0.5) showed the highest tensile strain capacity (6.34 %), crack control capability, and strain-hardening characteristics, with performance closest to the reference ECC containing 2.0 vol% virgin polyethylene fibers. A trilinear tensile constitutive model was established considering the effect of recycled fiber replacement ratio ( R ) on the complete tensile stress-strain curve. Based on Weibull distribution analysis, the critical tensile strain was evaluated for self-healing ECC, with PEF1.5RPPF0.5 exhibiting a high critical tensile strain ( ε 100μm =3.92 %). A comprehensive performance index was proposed that integrates both mechanical properties and environmental benefits, which can be effectively used to determine the rational dosage of recycled materials. • Developed ultra-tough green ECC using recycled fibers with virgin polyethylene fibers. • Recycled polypropylene fibers superiorly preserve ECC's tensile performance. • The critical tensile strain of ECC was evaluated based on the Weibull distribution. • Propose an index ( P ) to integrate mechanical properties and environmental benefits.