Computers and Concrete

Volume 37, Number 1, 2026, pages 45-77

DOI: 10.12989/cac.2026.37.1.045

Ensemble boosting-based model for predicting compressive strength of recycled aggregate concrete

Mosbeh R. Kaloop , Mohamed Rezaik , Ash Ahmed , Jong Wan Hu , Mohamed Eldessouki , Emad Elbeltagi

Abstract

Using recycled aggregate concrete (RAC) has recently been growing rapidly as an alternative to conventional concrete for sustainable development in construction. Nevertheless, there are limitation in computational guidance for compressive strength (CS) of RAC. Thus, this study aims to develop ensemble data-driven models for estimating the CS of RAC. Five ensemble models, namely category-boosting (CatBoost), gradient-boosting (GBoost), extreme gradient-boosting (XGBoost), K-nearest neighbor boosting (KNN), and random forest (RF), were developed, examined and compared for estimating the 28-day CS. A total of 578 datasets of different RAC mixtures were used to develop and test the proposed models. SHapley Additive exPlanations (SHAP) was used to analyze the impact of the used input variables on CS. The multivariate adaptive regression splines (MARS) algorithm was used to formulate the relationship between significant input variables and CS. The results show that CatBoost model outperformed the other proposed models with correlation coefficient (r) and mean absolute error (MAE) scores of 0.92 and 4.36 MPa, respectively. SHAP results of the CatBoost model show the impact of water/cement ratio is highly significant in modelling CS of RAC followed by nominal maximum recycled concrete aggregate (RCA) size, RCA replacement ratio, and bulk density of natural aggregate. Although parent concrete strength and the Los Angeles abrasion index of RCA have limited influence on the CS of RAC, they can be used to enhance the CS when both are greater than 40 MPa and 35 MPa, respectively. The proposed MARS equations can be used as a guideline in the design stage of RAC mixtures.

Key Words

boosting; compressive strength; ensemble; recycled aggregate concrete

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