# Design Procedures for Sustainable Structural Concretes Using Wastes and Industrial By-Products
## 5 Conclusions  
The present research was aimed at studying the design approach for structural concrete mixtures with the incorporation of wastes. In particular, electric arc furnace slag (EAFS) aggregates and fly ash (FA) powder, as well as recycled tire waste (RTSF) were used and the developed matrixes were compared with two reference mixtures, REF1 and REF2. According to the predefined requirements of the two target mixtures and by using the modified Andreasen and Andersen particle packing model, it was possible to achieve EAFS optimized concrete compositions, reaching the highest compactness and strength. RTSF were also incorporated in the EAFS concrete selected in order to assess the feasibility of developing FRCs including high wastes percentages. Workability and mechanical behavior were evaluated for reference mixtures, REF1 and REF2, and for the designed EAFS mixtures developed with and without RTSF. Physical properties were investigated for EAFS8D1, FRC_EAFS and the reference mixture REF2, as representatives of the studied mixtures. The FRC_EAFS allowed to study the effect of the incorporation of RTSF on the physical properties of the designed mixtures. The main conclusions of this study are:  
(1) The EAFS aggregates significantly altered the concrete fresh state when compared to natural aggregates typically used in structural concrete design. Compositions have been shown to be very sensitive to the process of mixing and to the \(w/p\) or \(w/c\) ratio, most likely due to the porous nature of the EAFS aggregates. The EAFS aggregates' porosity leads to the delayed absorption of water during the mixing process, resulting in alterations of the fresh and hardened behavior during mixing that could be solved by adapting the mixing process. (2) Two of the mixtures of greater interest for a waste-based structural concrete were the EAFS8C and EAFS8D1 mixtures, which reflected the optimal balance between the percentage of EAFS aggregate used and the behavior reached in the fresh and hardened state. Nevertheless, the EAFS8D1 mixture seemed to be a more sustainable mixture, since the amount of cement used in its composition was approximately 19% lower than the EAFS8C mixture. The replacement of a significant portion of the natural ingredients with substantial quantities of industrial by-products increases the sustainability potential of concrete, in particular with the EAFS8D1 mixture. The replacement percentages (in weight of solid ingredients) were about 10% of FA and 70% of EAFS aggregates. (3) For a structural concrete containing EAFS aggregates, the results seemed to indicate that parameters \(w/p\) and \(q\) can be initially estimated for intermediate values of the parameters studied adopting the linear and second-degree polynomial equations. (4) The average air and water permeability coefficients of EAFS8D1 were in accordance with the values found in the literature. Moreover, based on water permeability coefficients, \(K_{\text{W}}\), the EAFS8D1 mixture can be classified as a concrete of normal quality by using the classification proposed by [PERSON]. [59]. (5) The carbonation coefficient of REF2 mixture was 9.4% higher compared with the carbonation coefficient of the EAFS8D1 mixture, and the variation of the average carbonation resistance, \(R_{\text{c65m}}\), of REF2 was 25.1% lower than EAFS8D1. FRC_EAFS showed even better results, when compared to REF2. In this way, the EAFS8D1 and FRC_EAFS mixtures showed an improved behavior to carbonation resistance relative to the reference mixture. By adopting the design approach followed, it was possible to design concrete mixtures that, while meeting the fresh and hardened state requirements, were able to incorporate large percentages of wastes or industrial by-products, and therefore potentially improve environmental performance. The mixtures developed even outperformed the conventional reference mixtures in some of their characteristics, such as strength and resistance to carbonation.