O uso de resíduos de construção e demolição (RCD) na fabricação de blocos intertravados reforçados com malha Pet : uma aplicação da aprendizagem de máquina

Abstract

The construction industry is constantly growing worldwide. Every day, new buildings are constructed, renovated, and demolished. This growth is accompanied by the generation of construction and demolition waste (CDW), consumption of natural aggregates, and increasing cement, leading to several environmental and social problems, such as irregular waste disposal, overcrowding of landfills, illegal extraction of natural resources, CO2 emissions, among others. Therefore, sustainable alternatives are of utmost importance. Recycled concrete is a good option for applying CDW, since its aggregates can be partially or totally replaced by waste. Several products originate from concrete, such as interlocking paving blocks. However, a challenge for these products is their low mechanical strength, which is often inferior to traditional concrete products. In this context, this study seeks to verify the feasibility of making interlocking blocks with their fine and coarse aggregates from CDW. For this, machine learning was used to define the optimized mix that achieves the greatest resistance of the mixture. A mesh was also created to improve the strength of the blocks and, consequently, create another recycling alternative for polyethylene terephthalate (PET) bottles. Three compositions were then defined: pure recycled concrete (PRC), recycled concrete with mesh (CRM), and recycled concrete with mesh and ash (CRMP). The latter will have fly ash added instead of 20% of the cement. Visual inspection of the blocks immediately after manufacture showed good results, with no cracks or cavities. A more in-depth analysis was performed using SEM which identified small cracks on the surface, but no cavities. An X-ray fluorescence analysis was also performed, which showed that the CDW, together with Portland cement and fly ash, did not present any chemical elements that would be harmful to the recycled concrete. Finally, the results of the mechanical and physical tests determined that the blocks do not meet the requirements set forth by NBR 9781. However, changing the applicability of the blocks to masonry, their results are within those specified by the international standards ASTM C90-24 and ASTM 140/140M-24. Therefore, the use of RCD as a substitute for natural aggregates in concrete is viable, with potential for several other research projects.