## 4 Conclusions  
This work aimed to investigate the characterisation of structural recycled concrete for the production of beams. The concrete was produced by replacing all the natural aggregates with recycled aggregates from precast concrete rejects. These aggregates have been considered as all-in-one, which represents an advantage in terms of economy and operability for the manufacturing process, in addition to the already known environmental benefits due to the reduction of waste and the lower extraction of raw materials, as set out in the targets of \"Goal 12: Responsible consumption and production\" of the Sustainable Development Goals established by the United Nations. Firstly, the analysis of the recycled aggregates showed the adaptability of their granulometric curve to the Fuller method, which allows them to be used in the production of concrete. Subsequently, a large number of cubic and cylindrical specimens were made in order to obtain the main mechanical properties of the recycled concrete. These tests allowed the definition of a HA-30 structural recycled concrete. In addition, the digital image correlation technique was used to obtain more accurate and full-filed strains. Thanks to this technique, the high heterogeneity of the material and the difference found between the results of the cylindrical and cubic specimens were analysed. The results of the experimental characterisation were then used to define an analytical theoretical model to obtain the maximum load and deflection in bending beams. The data provided by DIC allowed a reliability-based probabilistic approach to be adopted, performing one million simulations by modifying the input parameters according to the distributions calculated from the experimental tests. This allowed to obtain a proba  
Figure 9: Results obtained during the sensitivity analysis of the deflection model: (**a**) first-order Sobol indices; and (**b**) total Sobol indices. bilistic density function for the maximum load and deflection of the recycled concrete beams studied. Finally, the theoretical simulations were validated by experimental tests, in which six beams were manufactured and tested in the laboratory. In all cases, the results were in agreement with the model, and the predicted values were within the acceptable range. These results demonstrate the great potential of the proposed methodology to characterise and predict the behaviour of recycled concrete structural elements. Nevertheless, the strength prediction model was more accurate than the deflection model, so a sensitivity analysis of the parameters included in the model was carried out to better understand its behaviour. The results showed a higher influence of the modulus of elasticity (47%), followed by the arbitrary coefficient used to calculate the effective moment of inertia (39%). The difficulty in precisely determining this parameter may account for the model's lower accuracy and represents one of its potential weaknesses. Furthermore, it should be noted that a simple analytical theoretical model was chosen for this study, which presents a limitation when incorporating certain indirect factors. Factors such as interfacial slippage, creep or shrinkage, although having less direct influence, can affect the result and limit the accuracy of the model if they are not taken into account. One of the main future works will focus on improving the analytical theoretical model, trying to include some of these factors that could improve the accuracy of the results, e.g., creep or shrinkage deformation, and even using a Bayesian approach to adjust the results from the experimental data with a larger number of samples and variability in loading or experimental conditions such as temperature and humidity. In addition, adaptation of the model parameters to material properties and configurations from existing studies could help to validate its extrapolation so that it can be generalised and its use extended to the scientific community.