Experimental and Numerical Evaluation of Utilizing Recycled Concrete Aggregates in Stone Column

Stone columns improve bearing capacity and reduce settlement. This study evaluates recycled concrete aggregate (RCA) as stone-column backfill using large-scale physical modeling and a 3D finite-element (FE) model. A combined experimental validation and 3D calibrated parametric design assessment of RCA-filled stone columns, including group and cap effects under plate loading, was made. Three plate-loading tests were performed in a 1.0 m-diameter tank on loose, dry sand: untreated soil, a single natural aggregate (NA) column, and a single RCA column (D = 80 mm, L/D = 6). Experimentally, RCA increased bearing stress by ~ 50% at 25 mm settlement (vs. ~23% for NA), demonstrating that RCA can match or outperform NA under identical installation and loading conditions. The 3D FE model reproduced the measured response with < 3% deviation at the reference settlement. Numerically, the study identified an optimal column length of ~ 4–6D, quantified spacing-dependent group efficiency losses at practical spacings (≤ 2D) due to stress overlap, and showed that cap layers can enhance NA performance but may not benefit RCA columns under the tested footprint. These findings provide design-relevant guidance for adopting RCA in stone columns while accounting for geometry, group interaction, and capping effects.