Propriedades de concretos leves autoadensáveis com agregados leves artificiais produzidos a partir da calcinação de resíduos agroindustrial e de mineração

Abstract

Self-compacting concrete (SCC) is an important example of new technology and alternative to the use of conventional concrete. The rheological parameters demonstrated by this type of concrete, provide high fluidity and cohesion that results in the ability to fill and resistance to segregation, as well as optimize concrete processes and reducing labor costs. Currently, due to the lack of resistant soil to support loads of buildings in urban agglomerations, studies have been carried out in search of possibilities that result in a lower weight for the structure, as well as ease of transportation, execution and thermoacoustic properties. The self-compacting lightweight concrete (SCLC) then emerges as a possible alternative for grouping the benefits of SCC and structural lightweight concrete (SLC). In the production of these concretes, the lightweight aggregate most used in the world and in Brazil is still an expanded clay, with its national production concentrated in the Southeast Region. In this context, studies carried out by Leal de Souza (2019) and Souza (2019), verified the viability of producing lightweight aggregates from the sintering of industrial residues and regional raw materials (Rio Grande do Norte/Brazil), as waste from sugar cane biomass ash (SCBA), scheelite residue (RPS) and local clays. In view of the above, the present study listed some of the lightweight aggregates that were developed by Leal de Souza (2019) and Souza (2019), and analyzed their influence on the composition of self-compacting lightweight concretes, investigating their efficiency and behavior in comparison with SCLC produced with commercial lightweight aggregate. The concretes were subjected to characterization tests in the fresh state, where the properties of fluidity, apparent viscosity, visual stability and passing ability were evaluated, through slump flow tests, flow time (t500), visual stability index and J-ring, respectively, and measurement of fresh density. In the hardened state, tests were performed to determine the mechanical properties, with the compressive strength test at 7 and 28 days, with the measurement of the dry density for each age, and the durability parameters through the diffusion of chloride ions. The results obtained showed the viability of producing selfcompacting lightweight concrete with unconventional lightweight aggregates. Both in the fresh and in the hardened state, all mixtures met the requirements established in the standard, with final density ranging between 1.94 to 2.03 g/cm³ and compressive strength at 28 days between 36.72 to 26.11 MPa. The mixtures with lightweight aggregates of SCBA showed a constant performance and similar to the performance of concrete with commercial lightweight aggregate, demonstrating to be a promising material for use in self-compacting lightweight concretes. Still, it was found that the physical properties of the lightweight aggregates influenced the results obtained in the fresh and hardened state, making the lightweight aggregate the main responsible for limiting and influencing the properties of the concretes.