Efeitos do tratamento superficial da sílica ativa com soluções de ácidos nítrico e fosfórico em propriedades do concreto

The addition of active silica potentially improves the quality of concrete due to its high reactivity and pore refinement effect. The reactivity of silica is likely related to its charge density. Variations in surface charge alter the reactivity of the material consequently affecting the properties of concrete. The present study aimed at investigating variations in the charge density of silica as a function of acid treatments using nitric or phosphoric acid and different pH values (2.0, 4.0 and 6.0). Effects on concrete properties including slump, mechanical strength, permeability and chloride corrosion were evaluated. To that end, a statistical analysis was carried out and empirical models that correlate studied parameters (pH, acid and cement) with concrete properties were established. The quality of the models was tested by variance analysis. The results revealed that the addition of silica was efficiency in improving the properties of concrete, especially the electrochemical parameters. The addition of silica treated using nitric acid at pH = 4.0 displayed the best cement performance including highest strength, reduced permeability and lowest corrosion current

Efeito da adição de fibras da palma do licuri (syagrus coronata) no comportamento físico e mecânico de compósitos de matriz cimentícia

This research was motivated by the requirement of asbestos s replacement in building systems and the need to generate jobs and income in the country side of the state of Bahia, Brazil. The project aimed at using fibers from licuri leaves (syagrus coronata), an abundant palm in the region, to produce composites appropriate for the sustainable production of cement fibre reinforced products in small plants. The composites were produced in laboratory using Portland cement CP-II-F32, sand, water, licuri palm fiber contents of 1.0, 1.5 and 2.0% by weight of binder (two different fiber length) and metakaolin. The latter was chosen as an additional binder for its efficiency to reduce the alkalinity of cementitious matrixes therefore preventing the degradation of vegetable fibers. The characterization of the composite components was carried out by sieving and laser particle size analyses, thermal analysis, fluorescence and X-ray diffraction. The composites performance was evaluated by 3- point-bending tests, compressive strength, ultrasound module of elasticity, free and restrained shrinkage, water capillarity absorption and apparent specific gravity. It has been found that the addition of fibers increased the time to onset of cracking over 200.00% and a 25% reduction in cracks opening in the restrained shrinkage test. The capillary absorption reduced about 25% when compared to fiber-free composites. It was also observed with regard to flexural strength, compressive strength and specific gravity, that the addiction of fibers did not affect the composite performance presenting similar results for compounds with and without fibers. In general it can be stated that the reinforced composite fibers of palm licuri presents physical and mechanical characteristics which enable them to be used in the intended proposals of this research

Avaliação da incorporação combinada dos resíduos de cascalho de perfuração de poço de petróleo e de polimento do porcelanato em cerâmica vermelha

Among the industries, those that produce ceramic porcelain for use in construction industry and oil, during the exploration and production period, play an important role in the production of waste. Much research has been carried out both by academia and the productive sector, sometimes reintroducing them in the same production line that generated them, sometimes in areas unrelated to their generation, as in the production of concrete and mortar for the construction, for example, but each one in an isolated way. In this research, the aim is to study the combined incorporation of the waste drill cuttings of oil well and the residue of the polishing of porcelain, generated in the final stage of finishing of this product in a clay matrix, for the production of red pottery, specifically bricks, ceramic blocks and tiles. The clay comes from the municipality of São Gonçalo, RN, the drilling waste is from the Natal basin, in Rio Grande do Norte, and the residue of the polishing proceeds from a ceramic porcelain of the State of Paraíba. For this purpose, we used a mixture of a plastic clay with a non-plastic, in a ratio of 50% each, settling formulations with the addition of these two residues in this clay matrix. In the formulations, both residues were incorporated with a minimum percentage of 2.5% and maximum of 12.5%, varying from 2.5% each, in each formulation, which the sum of the waste be no more than 15%. It should be noted that the residue of the polishing of ceramic porcelain is a IIa class (not inert). The materials were characterized by XRF, XRD, TG, DTA, laser granulometry and the plasticity index. The technological properties of water absorption, apparent porosity, linear shrinkage of burning, flexural tensile strength and bulk density were evaluated after the sintering of the pieces to 850 °C, 950 °C and 1050 °C, with a burning time of 3 hr, 3 hr and 30 minutes, and 3 hr and 50 minutes, respectively, with a heating rate of 10 °C/minute, for all formulations and landing of 30 minutes. To better understand the influence of each residue and temperature on the evaluated properties, we used the factorial planning and its surfaces of response for the interpretation of the results. It was found that the temperature has no statistical significance at a 95% of reliability level in flexural tensile strength and that it decreases the water absorption and the porosity, but increases the shrinkage and the bulk density. The results showed the feasibility of the desired incorporation, but adjusting the temperature to each product and formulation, and that the temperatures of 850 °C and 950 °C were the one that responded to the largest number of formulations

Estudo do resíduo fosfogesso na formulação de uma pasta para revestimento interno de edifícios

Universidade Federal do Rio Grande do Norte

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

Desenvolvimento de sistemas de aditivos químicos para aplicação em cimentações de poços de petróleo

The primary cementing is an important step in the oilwell drilling process, ensuring the mechanical stability of the well and the hydraulic isolation between casing and formation. For slurries to meet the requirements for application in a certain well, some care in the project should be taken into account to obtain a cement paste with the proper composition. In most cases, it is necessary to add chemicals to the cement to modify its properties, according to the operation conditions and thus obtain slurries that can move inside the jacket providing a good displacement to the interest area. New technologies of preparation and use of chemicals and modernization of technological standards in the construction industry have resulted in the development of new chemical additives for optimizing the properties of building materials. Products such as polycarboxylate superplasticizers provide improved fluidity and cohesion of the cement grains, in addition to improving the dispersion with respect to slurries without additives. This study aimed at adapting chemical additives used in civil construction to be used use in oilwell cement slurries systems, using Portland cement CPP-Special Class as the hydraulic binder. The chemical additives classified as defoamer, dispersant, fluid loss controller and retarder were characterized by infrared absorption spectroscopy, thermogravimetric analyses and technological tests set by the API (American Petroleum Institute). These additives showed satisfactory results for its application in cement slurries systems for oil wells. The silicone-based defoamer promoted the reduction of air bubbles incorporated during the stirring of the slurries. The dispersant significantly reduced the rheological parameters of the systems studied. The tests performed with the fluid loss controller and the retarder also resulted in suitable properties for application as chemical additives in cement slurries

Entre o cartão-postal e a cidade real: um estudo sobre paisagem e produção imobiliária em Natal/RN

Recent studies concerning the landscape have investigated the most important activities that contribute for its modification and have tried to better understand the society through the marks left by its quotidian. It is understood that singular landscapes constitute the cultural patrimonies of the cities, once they are part of the daily life of the citizens and are present in their social representations. Some contemporary authors defend the preservation of the natural and urban landscape trying, specially, to keep its importance for the local population. Natal is a city where the ambient qualities are well defined and known by the beauty of the area where it is located. Situated just between a river and the sea, the city grew following its geographic characteristics. The Potengi River, the Atlantic Ocean and the vast dunes ecosystem represented natural limits to the urban expansion; at the same time they have favored the development of a landscape pattern marked by the dialectic between the natural elements and the human interventions. However, this relationship changed after the intensification of the high rising development process that took place since the 1960s. The urban legislation tried to preserve the features of the local landscape delimiting Areas for Controlling Building High , destined to protect the scenic value of some parts of the city. On the other hand, the civil construction sector has made constant pressure in sense to abolish or to modify this legal instrument, aiming profits that have increased, in the 1990s, because of the consumption and the qualification of the urban space for tourist activities. It is necessary the raising of new elements to stimulate the quarrel about the landscape preservation, the process of the urban space production and the best way for the legislation implementation. This work tries to raise elements about the subject at local level, in sense to use Natal City experience to contribute for the formulation of indicators to raise the question about the lack of measure for subjective values, for example the cultural and affective value of the landscape. The natural elements inserted in the urban profile, represent strong visual references and supply identity to the town; they are part of the collective imaginary and are detached in the social context of the city. Then, why the preservation of the landscape, that estimates the improvement in the quality of life, is not enough to justify the controlling building high already previewed as part of Natal City Legislation? These questions send us to the approach of the landscape, as a community patrimony, alerting that some of its significant esthetics attributes must be preserved as a legacy for the future generations

Padronização e flexibilidade: proposta de um edifício tipo para uma escola técnica profissionalizante

Nowadays the acquisition of sustainable elements and concepts in construction has been increasingly discussed, improved and incorporated to buildings, since the sector directly interferes in the urban space and environment, representing environmental impact. In order to make a sustainable building (Green Building) it is vital to incorporate less damaging constructive practice, starting from the project until the operation of the enterprise, that means to consider an integrated process of conception, implementation, construction and operation. The more effective sustainable principles participation in architecture happens at the projecting step through minimal environment impact solutions. Among the issues varieties that goes with sustainability proposal of the buildings project, there were added to this work the elements that are directly attached to bioclimatic architecture, more specifically the climate variation, ventilation, lighting and sunlight, that directly affect the project conception. It is important to put in evidence that architecture role goes far beyond the simple activity of building spaces; it is the sequence of political, economic, social and cultural elements, having the users as the main apparatus to its materialization. Thereby this professional dissertation consists of an architecture draft for a professional and technological school in the Rio Grande do Norte State, this dissertation is based on the analysis of previous experience and the bioclimatic principles that implicate in building on hot and dry, hot and humid climates, and the use of strategic solutions that aim the optimization of natural light and ventilation

Desenvolvimento de pastas cimentantes utilizando cimentos portland compostos para cimentação de poços petrolíferos

The Compound Portland cements are commonly used in construction, among them stand out the CPII-Z, CPII-F and CPIV. These types of cement have limited application on oil well cementing, having its compositional characteristics focused specifically to construction, as cement for use in oil wells has greater complexity and properties covering the specific needs for each well to be coated. For operations of oil wells cementing are used Portland cements designed specifically for this purpose. The American Petroleum Institute (API) classifies cements into classes designated by letters A to J. In the petroleum industry, often it is used Class G cement, which is cement that meets all requirements needed for cement from classes A to E. According to the scenario described above, this paper aims to present a credible alternative to apply the compound cements in the oil industry due to the large availability of this cement in relation to oil well cements. The cements were micro structurally characterized by XRF, XRD and SEM tests, both in its anhydrous and hydrated state. Later technological tests were conducted to determine the limits set by the NBR 9831. Among the compound cements studied, the CPII-Z showed satisfactory properties for use in primary and secondary operations of oil wells up to 1200 meters cementing

Caracterização reológica de pastas de cimento portland de alta resistência contendo diferentes tipos de polímeros superabsorventes pela técnica de reometria rotacional

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2016.

O acesso à habitação no Brasil em tempos de capitalismo financeirizado : uma análise do Programa Minha Casa, Minha Vida

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Humanas, Departamento de Serviço Social, Programa de Pós-Graduação em Política Social, 2016.

Efeito da adição de cargas minerais leves na resistência mecânica de grautes para cimentação de poços offshore

The preparation of cement slurries for offshore well cementing involves mixing all solid components to be added to the mixing water on the platform. The aim of this work was to study the formulation of pre-prepared dry mixtures, or grouts, for offshore oilwell cementing. The addition of mineral fillers in the strength of lightweight grouts applied for depths down to 400 m under water depths of 500 m was investigated. Lightweight materials and fine aggregates were selected. For the choice of starting materials, a study of the pozzolanic activity of low-cost fillers such as porcelain tile residue, microsilica and diatomaceous earth was carried out by X-ray diffraction and mechanical strength tests. Hardened grouts containing porcelain tile residue and microsilica depicted high strength at early ages. Based on such preliminary investigation, a study of the mechanical strength of grouts with density 1.74 g/cm3 (14.5 lb/gal) cured initially at 27 °C was performed using cement, microsilica, porcelain tile residue and an anti-foaming agent. The results showed that the mixture containing 7% of porcelain tile residue and 7% of microsilica was the one with the highest compressive strength after curing for 24 hours. This composition was chosen to be studied and adapted for offshore conditions based on testes performed at 4 °C. The grout containing cement, 7% of porcelain tile residue, 7% of active silica and admixtures (CaCl2), anti-foaming and dispersant resulted satisfactory rheology and mechanical strength after curing for 24 hours of curing

Influência da adição de fibras de celulose (papel kraft) nas características dos blocos de concreto não estrutural

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2016.

Influência do espaçamento na densidade da madeira de Bagassa guianensis Aubl. (Tatajuba) no planaldo de Belterra, Pará.

As espécies arbóreas em florestas tropicais possuem madeiras com muita variação sob o ponto de vista de suas propriedades tecnológicas. Portanto, é necessário que se conheça com mais detalhes as propriedades tecnológicas em relação as silviculturais, principalmente daquelas espécies com potencial para comercialização. Várias espécies nativas estão sendo plantadas, por apresentarem crescimento rápido, porém pouco se sabe a respeito de suas propriedades tecnológicas e a relação em cada sistema ou método de plantio e tratos culturais. Visando contribuir para aumentar as informações sobre a interação entre as propriedades tecnológicas e a Silvicultura, este trabalho teve por objetivo estudar a densidade básica da espécie Bagassa guianensis Aubl., em quatro espaçamentos, em plantio com 16 anos de idade, em área do Campo Experimental da Embrapa Amazônia Oriental, em Belterra. Estado do Pará. Os dados foram coletados em uma plantação de Bagassa guianensis Aubl. cobrindo uma área de 5,75 ha. Foram sorteadas, aleatoriamente, 8 árvores por espaçamento (3mx2m, 3mx3m, 3mx4m e 4mx4m). perfazendo urn total de 32 indivíduos. Considerando que a Bagassa guianensis Aubl. pode ter diversos usos, desde construção civil e naval ate móveis finos, os resultados deste trabalho mostram que a espécie pode ser plantada em diferentes espaçamentos, de acordo com o use final pretendido, já que não houve influência dos espaçamentos estudados na densidade básica da madeira.