Volume-12, Issue-9, September 2026

Abstract

The escalating accumulation of plastic waste, particularly Polyethylene Terephthalate (PET), poses a significant environmental challenge, especially in developing regions with inadequate waste management systems. This study investigated the valorization of Waste Polyethylene Terephthalate (WPET) as a partial substitute for fine aggregate in concrete production, with a view to addressing both plastic waste disposal and the depletion of natural aggregate resources. WPET sourced from industrial plastic waste was collected, mechanically crushed, washed, and characterized through sieve analysis and specific gravity determination to assess its suitability as a lightweight aggregate prior to incorporation into concrete mixes. Concrete cubes were cast at a 1:2:4 mix ratio, with WPET substituting fine aggregate at 1%, 2%, 4%, 6%, and 8% by weight, using both washed gravel and crushed granite as coarse aggregates. Slump, density, and compressive strength tests were conducted at curing ages of 7, 14, 21, and 28 days to evaluate the fresh and hardened properties of the resulting concrete, with results benchmarked against relevant British Standard specifications. Findings revealed a progressive decline in workability, density, and compressive strength with increasing WPET content, attributable to the hydrophobic nature of plastic particles and their effect on bonding within the cement matrix. Nonetheless, specimens with lower replacement levels (up to 4%) met acceptable thresholds for lightweight and non-structural applications. The study concludes that WPET can serve as a viable partial fine aggregate substitute within optimized replacement limits, offering a practical pathway for plastic waste valorization, reduction of environmental pollution, conservation of natural aggregates, and promotion of sustainable construction practices.

Keywords: Plastic waste valorization, WPET, fine aggregate substitution, lightweight concrete, compressive strength

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Abstract

Recycling construction and demolition waste is essential in reducing its environmental impacts such as occupied land space and the leaching of harmful substances into the underlying soil. Understanding the mechanical properties of such waste ensures the strength and quality of concrete with recycled waste aggregates are not compromised. This study is divided into two components. The experimental component compared the compressive strength and elastic modulus of natural aggregate concrete (NAC) with that of recycled aggregate concrete (RAC). The RAC consisted of natural coarse aggregates replaced 100% by recycled concrete aggregates (RCAs) and was seen to do just as well as the NAC, showing that RAC is a viable option for structural use. In the artificial neural network (ANN) development component, the network model was trained using a dataset sourced from about 90 previous studies and used to predict the elastic modulus of RAC. With a mean absolute error (MAE) of 2.23, this study concludes that ANNs can be used to successfully predict mechanical properties of structural concrete.

Keywords: Recycled Concrete, Recycled Aggregate, Modulus of elasticity, Artificial Neural network.

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