This study addresses the growing environmental burden of polyethylene terephthalate (PET) waste by developing and optimizing structural lightweight concrete using fully recycled PET aggregates. A two-level factorial design generated eight mix combinations varying water–cement ratios (0.40–0.45) and PET fine and coarse aggregate contents. Fresh densities ranged from 1455 to 1515 kg/m³, confirming lightweight classification, while Vebe times of 13–40 s indicated medium-to-low workability. Dry densities were consistently within 1490–1537 kg/m³. Compressive strength ranged from 14.1 to 16.5 MPa, meeting LC 12/13 structural lightweight concrete requirements. Splitting tensile strength varied between 0.84 and 1.40 MPa, and water absorption levels of 4.66–10.2% reflected PET’s porous–hydrophobic influence on pore structure. ANOVA-based regression models demonstrated high predictive accuracy for compressive and tensile strength (R² ≥ 0.95), with moderate accuracy for workability (R² = 0.69) and water absorption (R² = 0.58). Numerical optimisation identified an ideal mix comprising a water–cement ratio of 0.45, fine aggregates of 372 kg/m³, and coarse aggregates of 532 kg/m³. Validation confirmed all predicted responses within a 95% confidence interval. The results demonstrate the technical feasibility of producing fully PET-based structural lightweight concrete, contributing to sustainable construction, plastic waste valorisation, and circular-economy objectives under SDG 11.
Uche et al. (Fri,) studied this question.