Modeling the prediction of fracture parameters in fly‐ash‐enriched concrete mixtures

Abstract This study presents a comprehensive investigation into the fracture properties and compressive strength of fly‐ash‐enriched concrete through advanced numerical analyses. Two mix designs were considered: CNS (fly ash replacing fine aggregate content) and INS (fly ash replacing cement content). A novel mathematical model was developed and optimized using the whale optimization algorithm (WOA), based on a robust dataset of 384 specimens, with 76% used for calibration. This model achieved a 16% reduction in prediction error and a 1.2% increase in correlation accuracy, effectively addressing the limitations of existing approaches. Numerical analyses using FEM on notched beams provided load‐deflection () curves, fracture energy, fracture toughness, critical crack mouth opening displacement (CMOD), and critical crack tip opening displacement (CTOD). Comparison of normalized cohesive stress (σ/ft) versus CMOD across various concrete strengths showed excellent agreement between numerical predictions and experimental data. Additionally, 3D XFEM simulations were employed to evaluate J‐integral values for CNS and INS scenarios. Results indicated that CNS mixes achieved superior fracture toughness, with fracture energy increasing by up to 3.3% under optimal fly‐ash content (40%). INS mixes exhibited notable improvements in J‐integral values at later curing ages, highlighting their potential for long‐term structural performance. The effect of fly‐ash content on CNS fracture toughness demonstrated that optimal replacement levels significantly enhanced crack resistance and energy dissipation, particularly at a water‐to‐cement ratio of 50%. These findings provide valuable insights into the design of high‐performance fly‐ash concrete for improved mechanical and fracture properties.