Mechanical Behavior and Predictive Modeling of Cementitious Composites Incorporating Recycled HDPE

In this study, High-Density Polyethylene (HDPE) granules were used as fine aggregate replacements in concrete to contribute to plastic waste recycling. Substitution rates were determined as 10%, 20%, and 30% by volume. Slump, density, and mechanical strength tests were applied to concrete samples. All strength values decreased as the HDPE substitution rate increased. Compressive strength decreased by 12-34%, tensile strength by 7-23%, flexural strength by 6-21%, and the modulus of elasticity by 15-34%. However, axial and lateral strain values increased between 4% and 44%. Density and slump values also decreased by 3-9% and 4-19%, respectively. Additionally, a database of previously published research on concrete and mortar was compiled and integrated with the experimental results obtained. This combined dataset was used to develop predictive models assessing the influence of HDPE substitution on the mechanical performance of cementitious composites. Exponential equations were formulated to estimate compressive strength, tensile strength, flexural strength, and modulus of elasticity. These formulations were compared with existing models reported in the literature. Statistical evaluation was conducted to measure predictive accuracy, and the results demonstrated that the models proposed in this study provided superior performance relative to earlier approaches.