O uso de resíduo de construção civil como substituto de agregados naturais em concretos: avaliação de alguns parâmetros de durabilidade

Abstract

The concern about the environmental impacts generated by the construction industry, which traditionally requires large quantities of raw materials and usually generate a large amount of waste, motivated the development of the Solid Waste National Policy that regulates and seek for sustainable solutions that can mitigate these effects. Additionally to this is the increased inspection of waste disposal and the interest of construction companies in reducing their costs, so the use of the recycled aggregate in the production of conventional concrete, appears as an alternative source of raw material. The research was developed with the objective of studying the influence of the use of recycled aggregates of construction and demolition waste in concrete submitted to different aggressive agents. The study presents the granulometric and physical characteristics of fine and coarse aggregates, being the recycled coarse aggregates were obtained from the process of recycling waste from the construction industry and collected at the provider Sand Beautiful View, located in Sobradinho, northern region of Brasília. After the characterization of the materials, the concrete test specimens were dosed by mass, with the substitution of the recycled aggregates in volume, in five replacement contents of the coarse recycled aggregate (0%, 30%, 50%, 70% e 100%). The water cement ratio considered was 0,55 and it was considered an additional amount of water obtained from tests of absorption with the recycled aggregate. In order to maintain the workability it was used superplasticizer additive. It was analyzed the following properties: compressive strength, diametric compression tensile strength, modulus of elasticity, absorption of water by capillarity, water absorption, voids index and specific mass, depth of ions chloride, carbonation and electrical resistivity. The results showed the feasibility of the use of the recycled coarse aggregate in the concrete production, considering the mechanical properties of the concretes, since it complies with the requirements specified in NBR 12655: 2015, and also the durability, since the results indicate low (CEB 192) and moderate (COST 509) risk of corrosion, and the depth of penetration of chloride ions as well as the carbonation did not exceed the concrete cover thickness. The substitution content of 30% of recycled aggregate presented better results from a mechanical and durability point of view and present to be the ideal replacement contend for the construction and demolition waste.