Made available in DSpace on 2014-12-17T14:07:13Z (GMT). No. of bitstreams: 1 JoaoBD_DISSERT.pdf: 1988359 bytes, checksum: 0207f1a988edf03be9aba6cc36f1919a (MD5) Previous issue date: 2013-11-29 / The sharp consumption of natural resources by the construction industry has motivated numerous studies concerning the application of waste to replace partially or fully, some materials, such as aggregates, thereby reducing the environmental impact caused by the extraction of sand and crushing process. The application of stone dust from crushing process arising as an aggregate for the production of Portland cement concrete is a viable alternative in view of the high cost of natural sands, in addition to the environmental damage which causes its operation to the environment. The stone dust has reduced cost compared to natural sand because it is produced in the beds of their own quarries, which are usually located close to major urban centers. This study examined the feasibility of using stone dust from the crushing of rock gneisses in the state of Bahia, replacing natural quartz sand. In the development of scientific study was conducted to characterize physical and chemical raw materials applied and molded cylindrical specimens , using as reference values Fck 20, Fck 25 and Fck 30 MPa ( resistance characteristic of the concrete after 28 days) in following compositions stone powder: 10%, 30%, 50 %, 100% and 100% with additive. The specimens were cured and subjected to the tests of compressive strength and water absorption, then the samples were subjected to the tests of X-ray diffraction and scanning electron microscopy. The results obtained showed that the composition with 10% stone powder showed the best results regarding the physical and mechanical tests performed, confirming the reduction in compressive strength and increased water uptake increased as the content of the powder stone in the concrete composition / O acentuado consumo de recursos naturais pela ind?stria da constru??o civil tem motivado in?meros estudos referentes ? aplica??o de res?duos que substituam parcialmente ou totalmente alguns materiais, como os agregados, reduzindo assim o impacto ambiental causado pela extra??o da areia e pelo processo de britagem. A aplica??o do p? de pedra oriundo do processo de britagem como agregado para a produ??o de concretos de cimento Portland, ? uma alternativa vi?vel, tendo em vista o alto custo das areias naturais, al?m dos danos ambientais que sua explora??o ocasiona ao meio ambiente. O p? de pedra possui custo reduzido comparado ao da areia natural pelo fato de ser produzido nos canteiros das pr?prias pedreiras, que geralmente ficam localizadas pr?ximas aos grandes centros urbanos. A presente pesquisa analisou a viabilidade da utiliza??o do p? de pedra proveniente da britagem de rochas gnaisses no estado da Bahia, em substitui??o ? areia natural quartzosa. No desenvolvimento deste estudo cient?fico foi realizada a caracteriza??o f?sica e qu?mica das mat?rias-primas aplicadas e moldados corpos de prova cil?ndricos, utilizando-se como refer?ncia os valores de Fck 20, Fck 25 e Fck 30 MPa (Resist?ncia caracter?stica do concreto aos 28 dias) nas seguintes composi??es de p? de pedra:10%, 30%, 50%, 100% e 100% com aditivo. Os corpos de prova foram curados e submetidos aos ensaios de resist?ncia ? compress?o e absor??o de ?gua, em seguida as amostras foram submetidas ? ensaios de difra??o de raios X e microscopia eletr?nica de varredura. A an?lise dos resultados obtidos constatou que a composi??o com 10% de p? de pedra apresentou os melhores resultados referentes aos ensaios f?sicos e mec?nicos realizados, confirmando a redu??o da resist?ncia ? compress?o e o aumento da absor??o de ?gua ? medida que se aumentou o teor do p? de pedra na composi??o do concreto

Made available in DSpace on 2014-12-17T14:07:23Z (GMT). No. of bitstreams: 1 MariadasVitoriasVAS.pdf: 9409036 bytes, checksum: 998170be52f9e25917324f5a0f7e8bba (MD5) Previous issue date: 2006-12-28 / 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 / A constru??o civil ? um dos maiores consumidores de mat?rias-primas naturais, sendo o concreto considerado hoje, o material mais utilizado em todo o mundo. Esse acentuado consumo de recursos naturais tem gerado preocupa??o com a preserva??o do meio ambiente, motivado v?rios estudos relativos ? utiliza??o de res?duos, que possam substituir, na sua totalidade ou parcialmente, com desempenho satisfat?rio, alguns materiais, como, por exemplo, o agregado, diminuindo assim o impacto ambiental causado pelos res?duos gerados. Pesquisas t?m sido realizadas, buscando conhecer e melhorar a microestrutura do concreto, bem como conhecer o mecanismo de corros?o das armaduras. Nesse contexto, esse trabalho foi desenvolvido visando conhecer a influ?ncia da substitui??o da areia natural pelo p? de pedra, quanto ? resist?ncia mec?nica, ? microestrutura e quanto ? sua durabilidade. Para obten??o dos par?metros eletroqu?micos, foi feita uma adapta??o do m?todo eletroqu?mico galvanost?tico ao estudo da corros?o das armaduras. Foram produzidos concretos com categorias de 20 MPa e 40 MPa, contendo areia natural, e concretos de mesma categoria, contendo p? de pedra, em substitui??o da areia natural, e os aditivos: nitrito de s?dio e cloreto de s?dio. Devido a utiliza??o do rejeito p? de pedra, foi feita a avalia??o do risco ambiental do mesmo. Os resultados indicam que os concretos de categoria 20 MPa apresentam melhor desempenho do que o concreto contendo areia natural, sendo vi?vel a sua substitui??o. Para a categoria de 40 MPa, o melhor desempenho ? o do concreto contendo areia natural. A adapta??o da t?cnica eletroqu?mica galvanost?tica ao estudo da corros?o das armaduras, mostrou-se v?lida para obten??o dos par?metros eletroqu?micos com grau de confian?a alto, considerando-se o n?mero de graus de liberdade