Influence of Fibre Blends on the Mechanical Properties and Durability Response of Structural Grade Concrete

Abstract

The study aims to evaluate the influence of high-volume polymeric fibre incorporation on compressive and flexural strength characteristics, with a particular emphasis on serviceability and long-term durability improvements in dense, low water-cement ratio matrices. Polypropylene fibres were introduced at dosages of 2.5% and 3.5% by cement weight, employing a controlled pre-mixing technique to prevent fibre agglomeration and ensure uniform dispersion throughout the matrix. Compressive strength tests were conducted on standard cube specimens at 14 and 28 days, while flexural strength tests were performed on prism specimens at 28 days. The results indicated a consistent improvement in compressive strength, ranging between 35 and 42% compared to the control concrete. The flexural strength exhibited marginal but steady enhancement (4.31 MPa → 4.32 MPa for M40 and 5.10 MPa → 5.12 MPa for M50). The flexural strength results show an enhancement in tensile performance due to the inclusion of polypropylene fibres. Both M40 and M50 grades demonstrate a moderate increase in flexural strength from 2.5 to 3.5% fibre dosage. The M50 mix shows superior flexural performance compared to M40 due to its denser microstructure and enhanced paste-aggregate bond. The gain of approximately 1–5% in flexural strength reflects the ability of PPF to bridge cracks and resist tensile stresses even after matrix cracking, ensuring post-crack ductility. The experimental outcomes confirmed that fibre inclusion substantially refined the failure pattern, improved post-cracking behaviour, and enhanced crack-bridging capability without compromising mix workability or matrix integrity.