Experimental Investigation of the Mechanical Properties of Concrete Incorporating Waste Plastic Fibres as Partial Fine Aggregate Replacement

Abstract

The increasing accumulation of plastic waste and the depletion of natural aggregate resources have created a need for sustainable alternatives in concrete production. This study investigated the mechanical, physical, and durability-related properties of concrete incorporating waste polyethylene terephthalate (PET) fibers as a partial replacement for fine aggregate. Concrete of grade M20 was produced with PET fiber replacement levels of 0%, 2%, 4%, 6%, 8%, and 10% by weight of fine aggregate while maintaining a constant water-to-cement ratio of 0.50. The workability, density, water absorption, compressive strength, split tensile strength, and flexural strength of the resulting concrete were evaluated in accordance with ASTM standards. Statistical analyses, including analysis of variance (ANOVA), correlation analysis, and regression modelling, were performed to determine the significance of PET fiber incorporation and identify the optimum replacement level. The results showed that slump values decreased from 82 mm to 55 mm with increasing PET fiber content, indicating reduced workability. Density decreased from 2418 to 2298 kg m⁻³, while water absorption reduced from 4.12% to 3.71%, suggesting improved durability characteristics. Mechanical properties improved significantly up to a PET fiber content of 6%, beyond which a decline was observed. The highest compressive strength (35.1 MPa), split tensile strength (3.68 MPa), and flexural strength (5.42 MPa) were obtained at 6% replacement, representing increases of 23.6%, 34.3%, and 29.7%, respectively, compared with the control concrete. Correlation analysis revealed strong positive relationships among the mechanical properties (r = 0.958–0.983), while regression analysis produced a highly reliable predictive model (R² = 0.962) for compressive strength. Optimization analysis identified 6% PET fiber replacement as the most suitable level, providing the best balance between workability, strength, density reduction, and durability performance. The findings demonstrate that waste PET fibers can serve as effective reinforcing materials in concrete production, contributing to enhanced engineering performance and sustainable management of plastic waste.

https://doi.org/10.5281/zenodo.20595830