Desenvolvimento de produto sustentável: análise da substituição de agregados por lixo eletrônico na produção de concreto

Abstract

Among the main concerns with environmental issues, this present work highlights two. The first is with the residue of the non-metallic fraction of the printed circuit board (PCB). This residue, despite having one of the highest rates of increase in its generation, arouses little interest from recyclers. The second issue is the concrete production process. Not only because it uses many natural resources, but because the Portland cement manufacturing process is responsible for generating a large part of greenhouse gases. In a survey carried out by this present work, no research was identified that investigated the replacement of part of the natural aggregates by the non-metallic fraction of PCB in the production of concrete. Therefore, this present work investigated the use of replacing part of the natural aggregates by the non-metallic fraction of PCB in the production of concrete. The replacement of part of the Portland cement with fly ash was also investigated. To carry out these investigations, a literature review was carried out to identify the types of waste that were being used as aggregates in the production of concrete and, also, to identify the percentages of replacement of Portland cement by fly ash. The data obtained in the literature review helped in the experimental design. The design was carried out using the mixing experiment methodology and the extreme vertex method. With this design, concrete traces were produced to investigate the percentage of replacement of natural aggregates by electronic waste, which produces concrete that is classified as structural concrete. This investigation was carried out for mixes that used the replacement of part of Portland cement by fly ash and for mixes that did not use this substitution. To carry out this investigation, slump and compressive strength tests of concrete were carried out. With the data from the experiment, a hypothesis test was performed (t test for two samples). The objective of this test is to compare the average compressive strength of the specimens whose traces replaced 20% of Portland cement with fly ash with the specimens whose traces did not perform this replacement. The result showed that there is no statistically significant difference between the two means. Another result of the experiments was the development of a mix using 20% fly ash as a substitute for Portland cement and part of the aggregates for e-waste, with a strength of 23.010 MPa. Four traces were also developed, without fly ash and with electronic waste, whose specimens obtained a concrete compressive strength of 21.804 MPa; 23.329 MPa; 23.614 MPa and 24.637 MPa. In this way, these five traits produced structural concrete, since their strengths are greater than or equal to 20 MPa. Finally, leaching tests were carried out. For leaching, a scanning electron microscopy was performed on the samples, conductivity and pH test in the water where the samples were soaked, in the periods of 24, 72, 168 and 384 hours. The result of the leaching showed that there was no chemical element in the specimens of the experiments that were different from the chemical elements found in the control traces. It also showed that there were no toxic elements, such as lead and mercury, in the specimens of the experiments. With these results, this present work concludes that from an environmental and natural resource saving point of view, the replacement of part of the natural aggregates by electronic waste, and of 20% of Portland cement by fly ash, are reasonable and significant. Among the objectives of this present work are not to minimize the cost of concrete production nor to improve the compressive strength of concrete. The objectives of this present work are to mitigate the problems caused to the environment by the inadequate destination of electronic waste and to reduce the generation of gases that cause the greenhouse effect, by the construction industry. As future works, this present work intends to investigate the replacement of part of the natural aggregates by the non-metallic fraction of PCI, with replacement percentages higher than those investigated here. The reason is that the statistical analysis indicated that a higher percentage of this replacement can improve the strengths obtained in this present work.