Research has shown that heavy metals in wastewater can negatively affect concrete properties, creating challenges for building floor applications. This study improved the strength and durability of concrete by incorporating plastic waste (PET) fibre as a partial replacement for fine aggregate (sand) at 0%, 10%, 20%, 30%, and 40%. Sixty concrete cubes were cast and tested to evaluate compressive strength. The results show that compressive strength increased with age across all PET replacement levels. The study demonstrates a potential solution to wastewater-related concrete deterioration while also promoting environmental sustainability by reducing plastic waste and lowering reliance on cement, which contributes to carbon emissions.