Most engineering as well as pavement materials are composites composed of two or more components to obtain a variety of solid properties to support internal and external loading. The composite materials rely on physical or chemical properties and volume fraction of each component. While the properties can be identified easily, the volume fraction is hard to be estimated due to the volumetric variation during the performance in the field. Various test procedures have been developed to measure the volume fractions; however, they depend on subjective determination and judgment. As an alternative, electromagnetic technique using dielectric constant was developed to estimate the volume fraction. Empirical and mechanistic approaches were used to relate the dielectric constant and volume fraction. While the empirical models are not very accurate in all cases, the mechanistic models require assumptions of constituent dielectric constants. For those reasons, the existing approaches might produce less accurate estimate of volume fraction. In this study, a mechanistic-based approach using the self consistent scheme was developed to be applied to multiphase materials. The new approach was based on calibrated dielectric constant of components to improve results without any assumptions. Also, the system identification was used iteratively to solve for dielectric parameters and volume fraction at each step. As the validation performed to verify the viability of the new approach using soil mixture and portland cement concrete, it was found that the approach has produced a significant improvement in the accuracy of the estimated volume fraction.

The most prevalent method for the prevention of freeze-thaw and salt scaling damage in cement based materials is through the entrainment of air voids using air entraining chemical admixtures (AEA's). However, the common field methods for measuring air content in fresh concrete cannot distinguish between entrained and entrapped air voids, and the actual air content in the hardened concrete can vary from that determined by these tests due to a variety of factors such as workability, placing operations, consolidation efforts, and environmental conditions. Previous research has shown the ability of ultrasonic attenuation to distinguish between entrained and entrapped air voids in hardened cement paste, providing a foundation for an inversion procedure to calculate the size and volume content of the two scatterer sizes. While additional challenges are present with measurements in fresh paste, the use of an immersion setup can overcome the limitations of cement paste containment vessels and provide a means to measure air content from batching to placement. An immersion apparatus to monitor ultrasonic wave attributes including attenuation in fresh cement paste is designed and built. Results comparing air entrained and non-air entrained cement pastes are presented. Ultrasonic wave attributes are studied as a function of time and level of chemical air entrainer. Finally, recommendations are made to improve the accuracy of the immersion apparatus in order to develop an in situ, quality control procedure to quantify the air content of fresh cement paste from batching to placement.

Not available / text

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 206-219). Available also in a digital version from Dissertation Abstracts.

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 2014-12-17T14:48:10Z (GMT). No. of bitstreams: 1 VeruscaKGR_DISSERT.pdf: 1561104 bytes, checksum: 8cf444f0891dd9cd7517204b9dd26c41 (MD5) Previous issue date: 2011-06-21 / This works aims at investigating the effects of adding waste from RCBP-polyester button manufacturing to Portland cement concrete, particularly regarding its consistency and mechanic strength. The RCBP used came from a button factory located in Parnamirim, RN, Brazil. The waste was added to the concrete on different ratios: 5 %, 10 %, 15 % and 20 % of the total cement mass. A sample of concrete without the RCBP was used as reference, 1:1,33:2,45:0,50. For the mechanic strength test four samples were tested with different ages (3, 7 and 28 days old) and mixtures. Furthermore, a Slump Test was also conducted in order to verify the concrete s consistency. A tendency to a reduction in the compression resistance was noticed for all samples. For the samples with 5 % and 10 %, there was also an increase in the traction resistance during inflexion, regarding the reference concrete. In the microstructural analysis, the RBCP was observed to show an irregular and porous surface, thus explaining the consistency decrease / O presente trabalho objetivou avaliar a influ?ncia da incorpora??o do res?duo de corte de bot?o em poli?ster-RCBP sobre a plasticidade e a resist?ncia mec?nica em concreto de cimento Portland. O RCBP utilizado na pesquisa originou-se do material descartado por uma empresa fabricante de bot?o localizada no munic?pio de Parnamirim/RN. Utilizou-se o res?duo, como carga no concreto, nas concentra??es de 0 %, 5 %, 10 %, 15 % e 20 %, em rela??o ? massa do cimento. O tra?o de refer?ncia do concreto utilizado na pesquisa apresenta a propor??o, em massa, de 1:1,33:2,45:0,50 (cimento:areia:brita:?gua/cimento). Nos ensaios de resist?ncia ? compress?o foram testados quatro corpos-de-prova para cada idade (3, 7 e 28 dias) e tra?o, enquanto que para os ensaios de resist?ncia ? tra??o na flex?o foram testados dois corpos-de-prova para cada tra?o. Al?m disso, fez-se o Slump Test, com vistas a verificar a consist?ncia do concreto. Observou-se uma tend?ncia de redu??o da resist?ncia ? compress?o e abatimento para todos os tra?os com incorpora??o do RCBP. Houve um aumento de resist?ncia ? tra??o na flex?o para os tra?os de 5 % e 10 %, em rela??o ao concreto sem incorpora??o do res?duo, superando o sugerido pela NBR 6118/2003 que apresenta uma correla??o entre resist?ncia ? tra??o e ? compress?o. Na an?lise microestrutural, observou-se que o RCBP apresentou uma superf?cie irregular e porosa, podendo ser o motivo do decr?scimo do abatimento

Made available in DSpace on 2014-10-09T12:52:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:03Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

A lixiviação de resíduos industriais e de mineração usualmente resultam em águas residuárias com pH extremamente ácido. Estes contaminantes podem migrar para o solo ou percolar através de barreiras de fundo em aterros de resíduos sólidos, perturbando a estrutura do solo e modificando a sua condutividade hidráulica. A adição de cimento Portland a este tipo de barreira pode ser uma opção para a neutralização do pH, buscando reduzir os impactos da lixiviação ácida nas águas subterrâneas. Embora muitos estudos abordem o comportamento de barreiras compactadas quando submetidas à ação dos mais diversos tipos de contaminantes, poucos tem explorado os aspectos microestruturais dos materiais componentes das barreiras e suas modificações ao longo do processo de percolação do contaminante. Neste contexto, este trabalho propôs a avaliação do comportamento microestrutural e macroestrutural de um solo argiloso residual compactado, com e sem a adição de cimento Portland (0, 1 e 2%), para fins de aplicação em barreiras impermeáveis sumetidas à ação de lixiviados ácidos. Os resultados motraram uma notável redução da condutividade hidráulica com a percolação de uma solução a 2% de ácido sulfúrico, a qual foi acompanhada pela ocorrência de recalques e redução do pH. Com relação à análise do tamanho e distribuição dos poros, pôde-se concluir que tanto a adição de cimento como a variação do peso específico de compactação, aliadas à ocorrência de recalques, contribuíram para a redução dos microporos e a consequente redução da condutividade hidráulica. Com relação às modificações químicas e mineralógicas, o ataque ácido promoveu principalmente a solubilização de Fe2O3 nas camadas superiores das amostras ensaiadas, porém não causou alterações significativas na estrutura dos argilominerais. Pode-se inferir que o peso específico de compactação não influenciou os resultados e que a adição de cimento contribuiu de maneira discreta para reduzir o impacto da percolação ácida, na medida em que produziu compostos de Ca e S nas camadas de meio e inferior das amostras, reduziu os microporos e retardou a solubilização de Fe2O3, a qual ocorreu principalmente nas camadas superiores das amostras ensaiadas. / The leaching of industrial and mining solid wastes usually result in wastewaters with extremely acidic pH, which might percolate into the ground or through bottom compacted barriers of landfills, disturbing soil structure and increasing hydraulic conductivity. The addition of Portland cement to containment barriers can be an option for pH neutralization, seeking to reduce the impact of acidic leachate to the groundwater. Although many studies have addressed the behavior of compacted barriers subjected to the action of several types of contaminants, a few have explored the microstructural aspects of barriers component materials and their modifications along the contaminant percolation process. In this context, this work proposed the evaluation of microstructural and macrostructural behavior of a compacted residual clayey soil, with and without the addition of Portland cement (0, 1, and 2%), for purposes of application in containment bottom submitted to acidic leachate percolation. The results showed a noticeable reduction in the compacted soil hydraulic conductivity during the percolation of a 2% sulfuric acid solution, which was accompanied by settlements and pH reduction. Regarding the determination of the size and distribution of pores, it can be concluded that both the addition of cement and the variation of specific weights, coupled with the occurrence of settlements, contributed to the reduction of micropores, which consequently resulted in hydraulic conductivity reduction. Concerning the chemical and mineralogical changes, the acidic attack mainly promoted the solubilization of Fe2O3 in the upper layers of the specimens tested but caused no significant modification in clay minerals structure. It can be inferred that the specific gravity did not influence the results and that the cement addition contributed discretely to reduce the acidic percolation impact, as it produced compounds of Ca and S in the middle and lower layers, reduced micropores, and slowly delayed Fe2O3 solubilization, which occurred mainly in the upper layers of the specimens tested.

The aim of the project is to utilise fly ash (PFA), a waste material/industrial byproduct, with metakaolin (MK), as a partial replacement for Portland cement (PC) in mortar and paste. The influence of various compositions of MK-PFA-PC blends on the resistance to the action of sulphate and synthetic seawater solutions, setting time and heat of hydration will be examined. MK is calcinated clay and is a relatively new pozzolanic material. Although it is a very effective pozzolan it is also very expensive. Using FA, which is a much less expensive material, as a PC replacement material, is problematic, as there is slow and low early strength development whereas MK enhances early strength development. Combining these materials in ternary blends should therefore produce a high performance material at an acceptable cost for use as a pozzolan. However the properties and performance of such a material still need to be fully established. The results of the research show, for the initial and final setting time of binary MK-PC pastes there is a substantial increase at 5% MK and then decreases at 10 and 15% MK before increasing again at 20% MK replacement level. However, with PFA there are different trends to those observed when using MK alone. The initial and final setting time of binary PFA-PC pastes shows a slight increase at 10% PFA and then systematically increases with increase in PFA content up to 40% PFA. Evaluation of sample preparation for porosimetry found that, overall, the compression tested samples show a lower proportion of 'fine pores' (volume (%) 0.05) jam than the cored and cut paste disks. It is deducted that this is due to the widespread microcracking during failure of the cubes under compressive loading thus modifying the pore structure present in the compressive tested samples. In strength development of mortar there is very little advantage in using MK over binary PFA-PC mortar blends when exposed to sulphate solution for up to 2 years. The strength behaviour in seawater is however quite different from that observed in mortar exposed to sulphate solution. As the MK replacement levels increase relative to the PFA levels the resistance to seawater attack improves significantly. In mortar exposed to sulphate solution the durability is greatly improved at high replacement levels in both binary and ternary blends. The durability of mortar exposed to seawater is greatly improved at 30 and 40% total replacement in ternary blended mortars.