REUSE OF MINING DAMS WASTE FOR BLOCKS OF CERAMIC PROCESSING AIMING FOR A MASONRY STRUCTURAL
Ana Cláudia Pereira Soares(1) *, Guilherme Borges Ribeiro(2), Raíssa Ribeiro Lima Machado(1), Sidney Nicodemos da Silva(1)
*e-mail: anaclaudia55@hotmail.com
Materials Engineering Department (1) Mechanical Engineering Department (2)
(1)(2)
Federal Center of Technological Education in Minas Gerais – CEFET- MG CEP: 30.421.169, Belo Horizonte, MG, Brazil
Abstract
The environmental impact provided by tailings dams can be mitigated by the reuse of these residues in the production of interlocking blocks floor, with a strength given the required range (4.5 - 16MPa). The following study aimed to enhance the features by replacing the sand bed of rivers by mining residue dams, which because of the huge volumes in the iron quadrangle may represent an opportunity to generate employment and income. By generating a mixture of traits of CPV-ARI cement, sand and water were made characterizations of mechanical and physico-chemical properties by the following procedures: the simple compression test, SEM, XRD and XRF. The trait of 50% showed the best mechanical strength (5.80 MPa). Thus, the blocks produced from these residues can be considered an economic alternative to mining depletion cycle in Minas Gerais.
Keywords: Residues, traits, mining. 1. Introduction
The Brazilian ceramic industry has great importance for the country and share in GDP - Gross Domestic Product - the order of 1.0% .1 Brazil is going through a time of economic growth, which encourages the construction industry therefore the red ceramic segment. This segment is responsible for producing bored and solid bricks, slabs, bricks and structural, tiles, shackles and rustic floors, products are based construction. Thus we see the need to frame their products to the requirements of technical standards, which would minimize the diversity of products, providing reduction of production costs and better service the construction civil.2
Mining activity constitutes an important economic activity in Brazil and world.3 The first of the challenges of this activity consists of the environmental impacts, since the process of mining generates, directly or indirectly, significant quantities of residue or co-products without an adequate use.3,4 In Minas Gerais the huge volumes of residue from iron mining dams motivates the study of these residues as raw materials for production of red ceramics (bricks and blocks).5
This paper presents a study of the application of a common residue in the mining sector, which consists of mud resulting wash the iron ore beneficiation. Therefore, the reuse of residue emerges as a measure to be adopted.
2. Experimental
2.1 Materials
The materials used for producing the samples were as follows: iron mining residue dams, cement CPV-ARI, sand and water.
First there was the realization of the measures required for the processing of the samples with the aid of a beaker. Then, the mixture was held, with water being added at the end in small measurements. The tailings dams were gradually added at a concentration of 0% to 90%. Four dashes were performed (table 1), the trait I is the mark of this work and served as a basis for comparison, it was prepared with cement 300 milliliters, 500 milliliters of sand, 100 milliliters of water and the proportion sand/residues 100%/0%. The trait II was processed in different iron ore powder additions compared to the sand of the mark (trait I). The amounts of water and cement maintained, while the ratio sand/residues changed to 50%/50%. Since the trait III was prepared in different substitutions of iron ore powder in place of the sand. The amounts of water and cement maintained, while the ratio sand/residues changed to 20%/80%. While the trait IV was processed in different substitutions iron ore powder instead of sand. The amounts of water and cement maintained, while the ratio sand/residues changed to 10%/90% .4,6
Table 1. Proportions traits in molding the blocks.
Raw - material (liters) Reference blocks (Trait I) 50% residue (Trait II) 80% residue (Trait III) 90% residue (Trait IV) CPV-ARI cement 300 ml 300 ml 300 ml 300 ml Natural sand / residue 550/0 ml 225/225 ml 110/440 ml 50/500 ml Water 100 ml 101 ml 102 ml 103 ml Income (Blocks) 26 21 20 32
It was observed that the staining of the blocks was a reddish color due to the presence of residue which contains iron III oxide (hematite – Fe2O3). As was gradually added with
hematite residue the traits, increased reddish pigmentation was observed.
2.3 Test methods
Cylindrical samples prepared by uniaxial compaction at 98MPa in stainless steel array of mixing were produced (powder) with cement ARI-CPV (Table 1). The crystalline phases, chemical composition and the microstructure were investigated by XRD, XRF and MEV.7 The mechanical strength was determined for each body-of-test and expressed as mean and standard deviation for 3 reps. Charging was conducted with the force application speed between 300 kPa/s 800kPa/s.8
3. Results and discussion
3.1 X-ray Fluorescence(XRF)
The chemical composition was determined by x-ray fluorescence (XRF) (Table 2). Through this semi-quantitative analysis it was possible to determine the concentration level of the elements present in the sample, and oxides. It was observed that the iron oxide content III present in this sample had become high due to the use of mining residue, consisting of hematite. Furthermore, the silicon oxide content (silica – SiO2) and aluminum oxide (alumina
– Al2O3) were also high due to its presence in Portland cement. Table. 2. Semi-quantitative analysis of fluorescence x-rays.
Semi-Quantitative Analysis Semi-Quantitative Analysis
Elements Percentual Oxides Percentual
Si 67,6% SiO2 63,4%
Al 11,5% Fe2O3 12,2% Mn 2,9% SO3 2,7% S 1,3% MnO 1,1% Ti 0,6% Cr2O3 0,6% K 0,4% TiO2 0,5% Cr 0,3% SrO 0,2% Sr 0,3% K2O 0,2% Nb 0,1% NbO 0,1% 3.2 X-ray Diffraction (XRD)
The crystalline phases were determined by x-ray diffraction (XRD). This analysis makes it possible to check the settings of the atoms in the crystal and can be represented by Figure 1. It was observed that major peaks presented were SiO2 (alpha quartz), Fe2O3
(hematite) and Al2O3 (alpha alumina), because those were present in greater quantity. The
hematite due to the presence of the dam mining residue, alpha alumina and alpha-quartz in the presence of Portland cement.
Figure 1. Analysis by x-ray diffraction.
3.3 Scanning Electron Microscope (SEM)
Verification of the microstructure was performed by using a scanning electron microscope (SEM). The morphology of the particulate materials of the dam residues can be demonstrated in Figure 2.
Figure 2. Morphology of the particulate material of residue dam.
3.4 Mechanical Strengh
The analysis of the mechanical properties was determined by simple compression test, and for each residue percentage was 3 bodies of the test piece for an average of that percentage. Charging was conducted with the force application speed between 300 kPa/s 800kPa/s.8 The 3 groups of concrete blocks (Figure 3) with more than 28 days have good resistance to compression and the range required by the rules between 4,5 MPa and 16 MPa, high resistance was available only on blocks more heavier.9 The concrete block with the trait of 80% of residue did not presented compressive strength within the required range due to its
curing time be less than 24 hours, but presented a considerably next resistance required in the minimum range (4,5MPa).
Figure 3. Simple sampling compression test chart.
Obs.: Sample containing 80% residual (curing time <24h): 4,33MPa
The results of the physical, chemical and environmental replacement of natural aggregate with residues have properties of interest for the production of concrete masonry elements. In Brazil there are buildings with more than 20 floors containing structural masonry concrete blocks. In much of the housing units of the “Minha Casa Minha Vida” program, the walls are built with concrete blocks that perform the functions and structure of closing, eliminating columns and/or beams, thus reducing the use of armor and forms (reducing the cost of the work) .10
4. Conclusions
The main problems faced in the reuse of the approach of solid residue from mining activities as an input in the production of masonry blocks were classified (residues) according
to environmental agencies, the blocks production process (traits) and physicochemical characterization, and the transfer of technology and social responsibility (NGOs in Nova Lima, Brumadinho and Vespasian) .6,7
Among the additions of iron ore powder, the value of 50% added showed the best result, its resistance proved to be higher than other traits, except for the mark. Furthermore, the consistency was not significantly impaired and is remarkable smooth color change (red).
In conclusion, the use of iron ore in the form of mud plaster powder is viable when applied to the addition of 50% residue to replace 50% of the sand since showed a considerable resistance to compression, and good pigmentation.4
Acknowledgements
This research was financially supported by Fundação de Amparo à Pesquisa de Minas Gerais (FAPEMIG).
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