Contribuição ao estudo da durabilidade de concretos produzidos com a incorporação de resíduo do beneficiamento de rochas ornamentais

Abstract

The construction industry consumes a significant amount of natural resources, however, it has a great potential on the use of wastes in production of building materials. The use of industrial subproducts can optimize inputs, as well as contribute to sustainable development practices. Brazil is one of the largest producers of ornamental rocks in the world, and Espírito Santo state is the main contributor to this industry in the country. To produce the plates, the rock blocks are sawn on looms, and this process results in approximately 25% of residue. This residue consists in slurry that passes through filters and must be discarded. Due to the amount of waste generated, the costs and difficulties for disposal, this material has been investigated for use in construction for several years. Therefore, this study aimed to research about the influence of the incorporation of the residue generated in ornamental stones processing, named in Portuguese as Resíduo do Beneficiamento de Rochas Ornamentais (RBRO), relating this residue to properties like concrete durability, in particular those associated with resistance to external aggressors like sulfate ions. For this purpose, the concrete was produced with three different water/cement ratios (0.45, 0.55 and 0.65) and the RBRO was added in levels of 5%, 10% and 15% in relation to the amount of water/cement mass created originally. The proprieties analyzed when the material was still fresh were workability and density, and after the material has gotten hard, it was observed its resistance to axial compression, to water absorption by capillarity and to immersion beyond microstructural analysis. For the tests of accelerated degradation it was used magnesium sulfate. The concrete were subjected to cycles of immersion and drying and, in the end, their resistance to compression was measured. The concrete created with 5% of residue showed the best results in terms of mechanical performance. It was observed in the attack concrete superficial microcracks that are typical of attacks by sulfates, also it was noticed the consumption of calcium hydroxide and the possible presence of ettringite by EDS. However, the results show the positive effect of the use of RBRO in the resistance to attack by sulphates in concentrations of 5%.