Compósitos para a construção civil com base em resíduos industriais dos processos de mineração de ferro, papel e celulose, entulhos e produção de cal

Abstract

The use of industrial waste in construction materials is an excellent mitigating alternative for the problems that arise with these residues generation. Human intervention in nature has damaged the environment, such as global warming, groundwater contamination, diseases spread, among others, which get worse by the reckless industrial waste disposal. The civil construction, iron ore processing, pulp and paper production and lime production industries stand out in this scenario due to the high volume of waste production and the sócio-environmental problems they usually cause, such as the incidents that occurred in storage of iron mining tailings in the cities of Mariana and Brumadinho (MG). There are large volumes of published papers with the intention of reusing industrial waste in order to reduce the exploitation of natural resources, including the application of that mentioned residues as concrete aggregates, cement production, bricks and blocks, asphalt mixtures, geopolymers, among others, in most cases with the use of Portland cement. This work deals with composites production in different contents of mentioned wastes without cement Portland addition. There are 35 proposed compositions compacted in the dimensions of 20 x 20 mm (diameter x height), in a metallic cylindrical mold, cured under ambient conditions for the assessment of dimensional variations, water absorption, uniaxial compressive strength, and specific mass. Four selected compositions were investigated for mineralogical changes by XRD, microstructural changes by SEM, microchemical mapping by EDS. The results point to the possibility of using these composites as materials for civil construction, with mechanical strength gains varying up to 21 MPa, discrete dimensional variations, acceptable levels of water absorption (between 18 and 26%), and safety in external contamination by any metals present. The improvements in the evaluated properties are due the microstructural changes, with the dissociation of elements of silicon, calcium, aluminum and sulfur. Mineralogical alterations such as the consumption of portlandite, periclase and dolomite, and the brucite, ettringite and cristobalita formation were also observed and related to the microstructure development in alkaline environment.