Estudo de desempenho de concretos estruturais produzidos com agregados reciclados

Abstract

Given the large amount of construction and demolition waste (CDW) generated in the construction industry, as well as the constant need to extract natural aggregates (NA) from deposits on the planet (which are becoming scarcer every day), it is clear that it is necessary to invest in efficiently sustainable alternatives. One alternative that is often overlooked is the use of mixed recycled aggregates (MRA), since most Brazilian and international studies are limited to applications in non-structural concrete or mortars. However, due to the fact that most of the RCDs produced are classified as MRA, it is necessary to carry out studies that analyze their properties for structural purposes. Thus, the general objective of this study is to evaluate the performance of concrete produced with coarse mixed recycled aggregate (MRAc). Concretes were produced with six different dosages, using the method proposed by ABCP, varying the percentage of replacement of coarse natural aggregate (NAc) by MRAc (20% and 50%) and adopting, in all mixtures, the replacement of 20% of CP V – ARI cement by the mineral addition metakaolin (MK). In the fresh state, the performance was evaluated through the slump test and the specific mass test. The analysis of the properties in the hardened state was carried out through compressive strength tests, as well as physical indices of the concretes, such as water absorption by capillarity. Regarding the use of MRAc, the compressive strength results tended to decrease compared to conventional concretes, with this reduction being smaller in concretes using 20% MRAc and greater with 50% MRAc. The use of MK improved the compressive strength results in these concretes, allowing them to have values closer to conventional concrete. Regarding the capillary water absorption property, the concretes using MRAc absorbed more water than the conventional one, which was expected due to the high porosity of these materials. The use of MK improved this property in all concretes, due to the high fine content of this supplementary material. Regarding the influence of the type of curing in the concretes, it was found that the average results of compressive strength are statistically equal at both ages of analysis, 7 and 28 days of curing, and the average results of water absorption by capillarity are also equal at 28 days of curing, demonstrating that the type of curing did not influence the results in the hardened state of the concretes. Regarding the influence of the location factor in the concretes, it was found that the average results of compressive strength are statistically equal at both ages of analysis, being 7 and 28 days of curing.