Experimental Study on Mechanical, Durability and Crack Resistance Properties of High-Strength Concrete Made with Surface-Treated Waste PET Fibers

1.     The concrete mix containing 10% silica fume and 0.75% surface-treated PET fiber (TM5) exhibited the best overall mechanical performance among all mixes tested, achieving 28-day compressive, split tensile and flexural strengths of 59.37 MPa, 4.57 MPa and 6.96 MPa respectively. 2.      Among the untreated PET fiber mixes, 0.75% dosage (TM3) produced the best performance, with 28-day strengths of 58.31 MPa (compressive), 4.41 MPa (split tensile) and 6.88 MPa (flexural), essentially matching or marginally exceeding the control mix. 3.      Increasing the untreated PET fiber content to 1.00% (TM4) reduced all three strength properties relative to the 0.75% dosage, with 28-day compressive strength falling to 54.63 MPa, attributable to reduced workability, fiber agglomeration and non-uniform dispersion. 4.       Surface treatment of PET fibers with a cement-silica fume slurry consistently improved mechanical performance relative to untreated fibers at the identical 0.75% dosage, confirming that fiber-matrix interfacial bonding, rather than fiber content alone, governs the effectiveness of PET reinforcement. 5.      The improvement in split tensile and flexural strength for the surface-treated mix indicates enhanced crack-bridging behaviour, although this was assessed indirectly in the absence of direct fracture or crack-width testing. 6.     The results support 0.75% surface-treated waste PET fiber, combined with 10% silica fume, as the optimum and recommended combination for producing sustainable, high-strength M50 concrete with recycled plastic reinforcement.

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