Influência da substituição de areia natural por pó de pedra no comportamento mecânico, microestrutural e eletroquímico de concretos

The construction industry is one of the largest consumers of natural raw materials, and concrete is considered today the most used material wide. This accentuated consumption of natural resources has generated concern with the preservation of the environment, and has motivated various studies related to the use of resid ues, which can partially or entirely substitute, with satisfactory performance, some materials such as the aggregate, and in so doing, decrease the impact on the environment caused by the produced residues. Research has been done to better understand and improve the microstructure of concrete, as well as to understand the mechanism of corrosion in reinforced steel. In this context, this work was developed aiming at discovering the influence of the substitution of natural sand by artificial sand, with rega rd to mechanical resistance, microstructure, and durability. To obtain the electrochemical parameters, an adaptation was made to the galvanostatic electrochemical method to study the corrosion in reinforced steel. Concretes of categories 20 MPa and 40 MPa were produced, containing natural sand, and concretes of the same categories were produced with artificial sand substituting the natural sand, and with the addition of sodium nitrate and sodium chloride. Due to the use of rock dust reject (artificial sand), an evaluation was made of its environmental risk. The results indicate that the concretes of category 20 MPa present a better performance than the concrete made with natural sand, thus making it a viable substitute. For the category 40 MPa, the better performance is from the concrete containing natural sand. The adaptation of the galvanostatic electrochemical technique to the study of the corrosion of reinforced steel within concrete proved to be valid for obtaining electrochemical parameters with a high degree of reliability, considering the number of degrees of freedom

Estudo da Potencialidade da produção de tijolos de adobe misturado com outros materiais: uma alternativa de baixo custo para a construção civil

The production of the red pottery brick, made traditionally with clay, is a technique that is already stabled. However, in spite of the little complexity that involves the conventional process of these bricks production, it are exposed to many problems that begin in the fase of exploration of the mines, the problems get worse because of the lack of the clay's characterization, and they continue through the steps of the dough preparation, conformation of the products, the drying and the burning process. The wastefulness is shown and so is the low quality of the material produced. Among other factors, the high use of energy in the burning makes the cost of this material inaccessible to the low income consumer. Besides this, the destruction of the environment around the mines and the use of native vegetation to produce wood - the most used fuel in the pottery industry - make serious environmental damage. The production technique of a new type of simple brick (adobe), that has low cost and no environmental damage, can be the viable altemative to lower the cost of this part of the civil construction, and, consequently, in the building of cheaper houses. In this paper, the results of the mechanical resistance of the adobe brick are shown, using in its composition, clay, natural vegetable fibers, cement and plaster in a process that is completely handcrafted and manual. It is intented to make clear that are possible alternatives to be put in practice, with the simple process, using "raw earth" that has been used in the construction of houses in thousands of years, trying to solve these severe problems. Analysis and tests were performed to find results that could prove the possibility of the utilization of this kind of material. Other studies are in progress, and the new researches are necessary to enrich this work, but it stays the certainty that there is potential to produce bricks from adobe, as an alternative that has low cost to civil construction

Desenvolvimento de métodos construtivos e de novos materiais empregados na confecção de cartuchos de próteses de membros inferiores

The manufacture of prostheses for lower limb amputees (transfemural and transtibial) requires the preparation of a cartridge with appropriate and custom fit to the profile of each patient. The traditional process to the patients, mainly in public hospitals in Brazil, begins with the completion of a form where types of equipment, plugins, measures, levels of amputation etc. are identified. Currently, such work is carried out manually using a common metric tape and caliper of wood to take the measures of the stump, featuring a very rudimentary, and with a high degree of uncertainty geometry of the final product. To address this problem, it was necessary to act in two simultaneously and correlated directions. Originally, it was developed an integrated tool for viewing 3D CAD for transfemoral types of prostheses and transtibial called OrtoCAD I. At the same time, it was necessary to design and build a reader Mechanical equipment (sort of three-dimensional scanner simplified) able to obtain, automatically and with accuracy, the geometric information of either of the stump or the healthy leg. The methodology includes the application of concepts of reverse engineering to computationally generate the representation of the stump and/or the reverse image of the healthy member. The materials used in the manufacturing of prostheses nor always obey to a technical scientific criteria, because, if by one way it meets the criteria of resistance, by the other, it brings serious problems mainly due to excess of weight. This causes to the user various disorders due to lack of conformity. That problem was addressed with the creation of a hybrid composite material for the manufacture of cartridges of prostheses. Using the Reader Fitter and OrtoCAD, the new composite material, which aggregates the mechanical properties of strength and rigidity on important parameters such as low weight and low cost, it can be defined in its better way. Besides, it brings a reduction of up steps in the current processes of manufacturing or even the feasibility of using new processes, in the industries, in order to obtain the prostheses. In this sense, the hybridization of the composite with the combination of natural and synthetic fibers can be a viable solution to the challenges offered above

Produção de grês porcelanato a partir de matérias-primas do Rio Grande do Norte e queima a gás natural

The State of Rio Grande do Norte, Brazil, possess major deposits of feldspar, clay, kaolin and talc, all raw materials used in the production of porcelainized stoneware tiles. Conversely, state industries manufacture only low added value red ceramics. Porcelainized stoneware tiles is one of the noblest ceramics, depicting low water absorption (typically below of 0,5%), in addition to excellent staining resistance and mechanical strength. The present work aims at investigating the potential of local raw materials for the production of porcelainized stoneware tiles. To that end, these materials were characterized by X-ray fluorescence, X-ray diffraction, particle size analysis, thermal gravimetric analysis and thermal differential analysis. Admixtures containing different compositions were prepared and fired at three temperatures, 1150, 1200 and 1250°C for 30 min. After firing, tests samples were characterized by water absorption tests, linear retraction, dilatometric analysis, apparent porosity, apparent specific mass, flexural strength, and microstructural analysis by XRD and SEM. The results revealed that ceramics with porcelainized stoneware tiles characteristics could be produced from raw materials originated in the State of Rio Grande do Norte

Viabilidade do uso de secadores solar de convecção natural e forçada para a secagem do coco Licuri

Licuri is a palm tree from the semiarid regions of Bahia State, Brazil. It is an important source of food and feed in that region, since their nuts are commonly eaten by humans and used as maize substitute for poultry feeding. The aim of this dissertation is to study the feasibility for use of natural convection solar dryers and forced being compared with the traditional drying outdoors for drying coconut licuri Syagrus coronate. The study led to the construction of two prototype solar dryer for carrying out experiments proving: model Solar Drying System Direct Exposure to Natural Convection built with wood, has a drying chamber with direct cover transparent glass laminates 4 mm, using techniques for proper isolation of the drying chamber. The two prototypes were comparatively analyzed for performance and drying efficiency with traditional extractive use by the community. Were evaluated the variables: time and drying rates and quality of the final samples of coconut licuri. The fruits were harvested and brought the town of Ouricuri, in the city of Caldeirão Grande, BA for the experiments comparing the three methods of drying was used a standard load of 4.0 kg The quantitative analysis for the result of the drying rate was found in 74% yield and 44% for natural and forced convection respectively compared with the traditional drying. These drying rates represent variation 3-5 times lower. Drying using forced convection licuri showed better quality, was found in a reddish pulp, representing the quantities that were kept of the nutrient beta carotene, and not notice the flavor change from the previous system, the final cost of construction of this system were higher . The prototypes built competitive advantage and had testified fully to resolve the technical difficulties previously encountered in the production of products made of coconut licuri. Allowing add value and increase their potential use for the fruit extractive communities of semi-arid region of Bahia

Metagenoma de comunidades microbianas expostas à radiação natural e a metais

Many species have specialized to live in the most varied existing environments showing the remarkable adaptability of the microbial world the most diverse physicochemical conditions. Environments exposed to natural radiation and metals are scarce around the world, presenting a microbiota still unknown. With a total number estimated between 4 and 6 x 1030 microrganisms on earth, they constitute an enormous biological and genetic pool to be explored. Metagenomic approach independent of cultivation, provides a new form to access to the potential genomic environmental samples becoming a powerful tool for the elucidation of ecological functions, metabolic profiles, as well as to identify new biomolecules. In this context, the genetic material of environmental soil and water samples from Açude Boqueirao Parelhas-RN, under the influence of natural radiation and the presence of metals, was extracted, pirosequencing and the generated sequences were analyzed by bioinformatics programs (MG-RAST and STAMP). Taxonomic comparative profiles of both samples showed high abundance of Domain Bacteria, followed by a small portion attributable to Eucaryota Domains, Archaea and Viruses. Proteobacteria, Actinobacteria and Bacterioidetes phyla showed the greater dominance in both samples. Important genera and species associated with resistance to various stressors found in region were observed. Sequences related to oxidative and heat stress, DNA replication and repair, and resistance to toxic compounds were observed, suggesting a significant relationship between the microbiota and their metabolic profile, influenced by regional environmental variables. The results of this study add valuable and unpublished data on the composition of microbial communities in these regions

Influência da substituição de areia natural por pó de pedra no comportamento mecânico, microestrutural e eletroquímico de concretos

The construction industry is one of the largest consumers of natural raw materials, and concrete is considered today the most used material wide. This accentuated consumption of natural resources has generated concern with the preservation of the environment, and has motivated various studies related to the use of resid ues, which can partially or entirely substitute, with satisfactory performance, some materials such as the aggregate, and in so doing, decrease the impact on the environment caused by the produced residues. Research has been done to better understand and improve the microstructure of concrete, as well as to understand the mechanism of corrosion in reinforced steel. In this context, this work was developed aiming at discovering the influence of the substitution of natural sand by artificial sand, with rega rd to mechanical resistance, microstructure, and durability. To obtain the electrochemical parameters, an adaptation was made to the galvanostatic electrochemical method to study the corrosion in reinforced steel. Concretes of categories 20 MPa and 40 MPa were produced, containing natural sand, and concretes of the same categories were produced with artificial sand substituting the natural sand, and with the addition of sodium nitrate and sodium chloride. Due to the use of rock dust reject (artificial sand), an evaluation was made of its environmental risk. The results indicate that the concretes of category 20 MPa present a better performance than the concrete made with natural sand, thus making it a viable substitute. For the category 40 MPa, the better performance is from the concrete containing natural sand. The adaptation of the galvanostatic electrochemical technique to the study of the corrosion of reinforced steel within concrete proved to be valid for obtaining electrochemical parameters with a high degree of reliability, considering the number of degrees of freedom