Propriedades reológicas e durabilidade do concreto autoadensável de alta resistência com resíduo de corte mármore e granito e areia de exaustão de fundição

Abstract

Self-compacting concrete, SCC, is practically a new concrete that has peculiar characteristics of fluidity and viscosity. To acquire such properties, it uses in its composition, mineral additions, fine materials, which, in large part, are industrial waste and, therefore, a sustainable material. Although the use of waste foundry sand (WFS) in concrete is already widespread, there is a gap regarding the waste foundry exhaust sand (WFES) and its influence on the reinforcement and, thus, producing a concrete that meets the prerogatives of compressive strength, durability, longer useful life and sustainability. In this research, the marble and granite processing waste residue, MGPW, was used as a mineral addition to improve the mixture viscosity, and waste foundry exhaust sand (WFES) as a partial substitute (10%, 20%, 30%, 40 % and 50%) of natural sand. Foundry Exhaust Sand makes up the WFSs, which correspond, on average, to 80% of the waste generated in the foundry industry. The influence of materials on concrete rheology, strength and durability was evaluated. Rheological parameters were tested by empirical methods. Mechanical properties were evaluated by compressive strength and splitting tensile strength. As indicators of durability, the tests of water absorption by immersion and capillarity, resistance to sulfates and acids attacks, bulk electrical resistivity, chloride permeability and corrosion potential were used. In fresh state, all mixtures presented fluidity and viscosity characteristics required by brazilian standard for SCC. As for compressive strength, all mixtures were classified as high strength. Mixtures showed good resistance to acid and sulphate attacks, low absorption by immersion in water and by capillarity. Very low permeability to chloride ions and high electrical resistivity, indicates the mixtures showed a negligible probability of corrosion and in the corrosion potential test the probability varied between uncertain and low. These results indicated that SCC with MGPW and FES has lower permeability to harmful agents and, consequently, greater durability when compared to reference concrete. All properties were improved with 30% of FES waste, although good results were obtained with up to 40%. In this sense, the use of these waste brings environmental benefits that translate into both the reduction of waste deposited in landfills and the reduction in the extraction of natural sand. the results show that the wastes, WFES and MGPW, can be used without affecting the concrete durability.