Argamassas cimenticias mistas a partir de rejeitos de beneficiamento da bauxita da Amazônia

Abstract

Worldwide aluminum production generates an enormous amount of Bauxite Wash Sludge Tails (RLLB) as residue obtained in upgrading bauxite processing. Currently, the search for innovative and sustainable solutions becomes essential in the face of the great consumption of natural resources by the construction industry. For these facts, the present work aims to demonstrate the feasibility of using RLLB, contained in dams of bauxite ores, as raw material for the production of mixed cementitious mortars. Tails (RLLB) was characterized physicochemically and mineralogically by X-ray diffraction (XRD), X-ray fluorescence (FRX) and scanning electron microscopy (SEM); mortars properly produced with natural aggregates, cement, sand, lime and water were subsequently produced. Was performedthe technical verification of the mortars according to the norms of the Brazilian Association of Technical Norms (ABNT) and the preparation of different roportions of mortar in the 1:3 trace were done by means of the variation of quantity of cement, tailings (RLLB) and water/cement ratio. Tests were performed in percentages of: 5%, 10%, 20% and 30% of tails replacing Portland cement, for age (one time/cure) of 28 days, and submission to mechanical tests in order to provide their classification according to the characteristics and interesting properties to the engineering. The tail consists of gibbsite kaolinite, hematite, quartz and anatase, showing Al2O3, SiO2 and Fe2O3 as the predominant chemical composition. The material is neutral, with pH close to 7, and grain sizes are in the clay fraction. The mechanical results of the mortars showed that the higher the amount of RLLB, the greater the compressive strength, in the range of 5%, 10%, 20% and 30% of the addition of tailings replacing the Portland cement in the traces, reaching a minimum value of 2.53Mpa with 5% of substitution and 3.26 MPa the maximum value with 30% of substitution, according to ABNT / NBR 13279. This was also confirmed by the tensile flexion mechanical tests. Throughout the process, it was verified the possibility of final disposal, environmental and adequate technique to the tail (RLLB), transforming it into mixed cement mortars. This will contribute to the reduction of existing tailings in mineral dams and consequently to the reduction of the costs destined by the miners for the maintenance, security and monitoring of this type of structure.