Assessment of mechanical properties with ANN modeling and fresh, and microstructural characteristics of eco-friendly concrete containing zeolite and crumb rubber waste

This study investigates the feasibility of using zeolite as a partial cement replacement and crumb rubber waste (CRW) as a fine aggregate substitute in the production of sustainable concrete. In addition to experimental evaluation, an Artificial Neural Network (ANN) model was developed to predict the mechanical properties of the mixtures. The results indicate that increasing the CRW content up to 45% and zeolite up to 15% leads to a reduction in slump and an increase in air content. While the incorporation of CRW reduces the strength of concrete, the presence of zeolite and extended curing periods up to 90 days contribute to strength improvement. Microstructural investigations using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) revealed that moderate amounts of zeolite enhance the formation of C–S–H gel and hydration products, producing a denser and more homogeneous matrix, whereas CRW increases voids and microcracks within the concrete structure. Statistical analysis confirmed that aggregate characteristics, CRW content, and curing age significantly influence the mechanical performance of concrete. The ANN model demonstrated good predictive capability for compressive, tensile, and flexural strengths, with prediction errors below 15%. Furthermore, the combined use of 15% zeolite and 45% CRW can reduce concrete production costs by approximately 17.89% and decrease CO₂ emissions by 13.37% compared with conventional concrete. These findings highlight the potential of incorporating waste materials to develop environmentally sustainable concrete.