Prediction of the mechanical properties of structural recycled concrete using multivariable regression and genetic programming

• A database about recycled concrete (RC) has been developed with 1831 mixes from 81 papers.
• Prediction of some of the most important properties of RC has been analyzed.
• Code expressions regarding fsp and Ec prediction have been adjusted using correction coefficients.
• Specific expressions used to predict these properties have been optimized.
• Multivariable regression and genetic programming have been used for predictions optimization.

This study focuses on the prediction of some of the most important properties of structural recycled concrete (compressive strength, modulus of elasticity and splitting tensile strength) taking into account, not only the recycled percentage and the quality of the recycled aggregates used, but also the production method. For said purpose, a database has been developed with 1831 mixes obtained from 81 papers.Firstly, in this manner, these properties have been compared with those of conventional concrete. Then, the need to adapt the prediction code expressions (adjusted for conventional concretes) was analyzed to take into account the use of recycled concrete, developing, if finally necessary, the correction coefficients which allow engineers to predict the recycled properties with the same approximation degree as in conventional concretes. These correction coefficients have been adjusted using multivariable regression, and have been analyzed using different statistical indexes.Lastly, specific expressions used to predict these properties in structural recycled concretes have been optimized. Two different tools have been used to develop these expressions: multivariable regression and genetic programming. The proposed expressions have been analysed using statistical parameters which have been compared with those obtained using the expressions proposed by other authors. In this regard, and finally, the best prediction expressions for the modulus of elasticity and the splitting tensile strength of structural recycled concretes have been proposed.