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Carbonation curing of concrete products has shown potentials for CO2 capture and storage with environmental, technical and economical benefits in global greenhouse gas mitigation exercise. The primary objective of this study is to investigate the effect of early age carbonation on mechanical performance and pH of concrete in an attempt to understand the process and promote large scale applications. / It was found that significant early strength was developed in cement and concrete through early age carbonation curing. The early strength could be maintained and improved due to subsequent hydration. Twenty-eight-day strength of carbonated cement and concrete was comparable to that of hydrated reference if subsequently cured in the air in a sealed bag, but was lower if subsequently cured in water. Treatment with either internal curing using lightweight aggregates or chemical admixture can effectively enhance late strength development in carbonated concrete. / For three typical cement-based products including cement paste compacts, concrete compacts and precast concrete, two-hour carbonation reduced pH value from 12.8 to 11.8 as the lowest and subsequent 28-day hydration could slightly increase pH by 2% as maximum. At any time pH of early age carbonated concrete was always higher than 11.5, a threshold value under which the corrosion of reinforcing steel is likely to occur in concrete. The high pH in early-age carbonated concrete was likely attributed to the fact that early age carbonation was an accelerated hydration process, which was totally different from weathering carbonation in which pH of concrete could be neutralized due to the decomposition of calcium hydroxide and calcium silicate hydrates gel. Therefore, early age carbonation technology is applicable not only to concrete products such as masonry units and paving stones, but possibly to precast concrete with steel reinforcement as well.

Recycled concrete aggregate (RCA) is a construction material, which is being used in the Canadian construction industry more frequently than it was in the past. The environmental benefits associated with RCA use, such as reduced landfilling and natural aggregate (NA) quarrying, have been identified by industry and government agencies. This has resulted in some incentives to use RCA in construction applications. Some properties of RCA are variable and as a result the material is often used as a structural fill, which is a low risk application. The use of RCA in this application is beneficial from an overall sustainability perspective but may not represent the most efficient use of the material. Efficient use of a material means getting the most benefit possible out of that material in a given application. The initial step in efficient material use is evaluating how a material affects its potential applications. In the case of RCA, this includes its use in concrete as a coarse aggregate. RCA is made up of both aggregate and cement mortar from its original application. Its make-up results in absorption capacities, which are higher than NA. Its high absorption capacity indicates that RCA can retain a relatively large proportion of water. Internal curing of concrete is the practice of intentionally entraining reservoirs of water within concrete. This water is drawn into the cement at a beneficial point in the cement hydration process. This water allows for a more complete hydration reaction, less desiccation, a less permeable concrete pore system, and less susceptibility to the negative effects of poor curing. The potential for RCA to act as an internal curing agent was evaluated in this research. Two RCA types were studied in the course of this research, one RCA of high-quality and one low-quality. These were compared to one NA type, which served as experimental control. Neither RCA type was found to desorb significant amounts of entrained water at relative humidity levels between 85% and 93%. This behaviour indicates that they would not behave as a traditional internal curing agent. Within concrete, the initial saturation levels of these RCAs were 0%, 60% and 100% of their full absorption capacity. The mixtures ranged from 30% RCA (by volume of coarse aggregate) to 100% RCA. These mixtures were subjected to two curing regimes, MTO-specified curing conditions and moist curing, in order to gauge the internal curing potential of the RCA. Fully saturated RCA mixtures were found to retain water throughout the course of testing. They were also found to increase the rate of compressive strength gain at early ages in comparison to similarly cured NA mixtures. Full saturation was found to have a negative effect on the thermal expansion behaviour of the concrete at 28 days concrete age. Permeable porosity of concrete was measured as an indicator of more thorough hydration in RCA concrete, but any potential benefits were masked by the increase in permeable porosity associated with permeable RCA. When compared with NA control mixtures and RCA mixtures cured under ideal conditions, it was found that saturated RCA mixtures provided compressive strength benefits. Low-quality RCA, which lost entrained water earlier in the testing period than high-quality RCA, benefitted in terms of early age compressive strength gains under specified curing conditions. High-quality RCA, which retained a relatively higher proportion of its entrained water throughout the early testing period, improved later age compressive strength under spec-curing conditions. Mixtures with 30% RCA (by volume of coarse aggregate) were generally found to not significantly affect the tensile strength, elastic modulus, and permeable porosity of the concrete. Tensile strength and elastic modulus were found to be consistently lower in RCA concretes, while permeable porosity was consistently higher. However, the magnitudes of these changes were not large enough to be statistically significant based on the testing regime employed. Compressive strength was significantly improved at 28 days when the 30% RCA was fully saturated. 30% RCA mixtures significantly reduced the thermal expansion of concrete at 28 days, which could provide particular benefit to concrete pavement applications. Overall, RCA saturation in new concrete had both positive and negative effects on the properties of concrete, which should both be considered in the context of the application for which RCA concrete is being considered. Specifically, concrete applications with the potential for poor curing and the need for reduced thermal expansion could benefit through the inclusion of coarse RCA. For example, these benefits could manifest in reduced thermal cracking at slab joints and reduced thermal stresses due to temperature gradients in pavements.

Increasing demands for more reliability and functionalities in electronic devices have pushed the electronics industry to adopt newly developed materials and reduce interconnect sizes and spacing. These adaptations have led to concerns of reliability failures caused by conductive anodic filament formation (CAF). CAF is a conductive copper-containing salt that forms via an electrochemical process. It is initiated at the anode and grows along the epoxy/glass interface to the cathode, and once CAF reaches the cathode a short circuit will occur. The objective of this research is to evaluate and compare the effects of curing agents (DICY vs. phenolic-cured epoxy) and drilling methods (laser vs. mechanical drilling) on CAF formation using an insulation resistance test at 85 ºC, relative humidity of 85%, and a voltage gradient of 0.4V/µm. Time-to-failure for DICY-cured and phenolic-cured epoxy with laser drilled microvias and mechanically drilled vias were determined using the insulation resistance test. The failed coupons were cross-sectioned and examined using a Scanning Electron Microscope equipped with Energy-dispersive X-ray spectroscopy to verify the existence of CAF. Weibull analysis was used to compare the reliability and identify the failure modes of the failed coupons. Test results show that DICY-cured epoxy is a better CAF resistant material than phenolic-cured epoxy. It is believed that the brittleness of phenolic-cured material might enhance the damage to the epoxy/glass fiber interface during drilling; and hence, facilitate subsequent CAF formation. The study also shows that laser drilled microvias are less prone to CAF formation than mechanically drilled vias, because there is less mechanical damage and lower glass fiber content. Finally, using Weibull analysis, it is determined that laser drilled microvias experienced infant-mortality failure, whereas mechanically drilled vias exhibited a wear-out type failure.

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Sitaraman, Suresh; Committee Member: Chang, Gee-Kung; Committee Member: Colton, Jonathan; Committee Member: Joshi, Yogendra; Committee Member: Swaminathan, Madhavan; Committee Member: Thompson, Patrick.

Orientador: Maria Salete Machado Cândido / Banca: José Roberto Cury Saad / Banca: Jesuania Maria Guardiero Azevedo Pfeifer / Abstract: The aim of this work was to evaluate the linear polymerization shrinkage and the degree of conversion of two commercial composite resins, with similar compositions, being one of use in anterior and posterior teeth (Filtek Z250) and other for use in posterior teeth (Filtek P60). The effect of different light sources was also evaluated in that process, and were used for that an halogen light curing (Degulux - Degussa) and a LED light curing of high intensity (Ultrablue IS - DMC). In that way, the materials and light sources were divided in four groups: Group 1 - Filtek Z250 resin cured with the halogen light curing (QHT); Group 2 - Filtek Z250 cured with LED light curing (LED); Group 3 - Filtek P60 resin cured with the halogen light curing (QHT); Group 4 - Filtek P60 cured with the LED light curing (LED). The polymerization shrinkage was measured with the insert of the materials in a plastic tube and the values of the alterations accomplished by an electronic instrument of linear measure with sensibility for 1æm. The conversion degree was obtained through Fourier Transform Infrared Spectroscopy (FTIR), where the picks were analyzed inside of the bands of interest in the values of 1.646 cm-1 and 1.731 cm-1, corresponding to the connections C=C aliphatic and C=O respectively. The results were submitted to the statistical analysis of Variance and test of Tukey (a = 0,05), which allowed to end that: the polymerization shrinkage of different materials (Filtek Z250 and Filtek P60) presented different behavior with the use of the same light source (LED); the degree of conversion of the materials came similar in relation to materials and light sources; the LED light curing (Ultrablue IS) presented results of polymerization shrinkage and degree of conversion that allow it to be used as an alternative to QHT light curing units. / Resumo: O objetivo deste trabalho foi avaliar a contração de polimerização linear e o grau de conversão de duas marcas comerciais de resinas compostas, com composições semelhantes, sendo uma de uso em dentes anteriores e posteriores (Filtek Z250) e outra para uso em dentes posteriores (Filtek P60). Também foi avaliado o efeito de diferentes fontes de luz nesse processo, utilizando-se para isso aparelho de luz halógena (Degulux - Degussa) e aparelho LED de alta intensidade (Ultrablue IS - DMC). Dessa forma, os materiais e fontes de luz foram divididos em quatro grupos: Grupo 1 - resina Filtek Z250 polimerizada com o aparelho de luz halógena (LH); Grupo 2 - resina Filtek Z250 polimerizada com aparelho LED (LED); Grupo 3 - resina Filtek P60 polimerizada com o aparelho de luz halógena (LH); Grupo 4 - resina Filtek P60 polimerizada com o aparelho LED (LED). A contração de polimerização foi medida com a inserção dos materiais em um anel plástico e a mensuração das alterações realizada por um instrumento eletrônico de medida linear com sensibilidade para 1 æm. O grau de conversão foi obtido através de teste de espectrometria no infravermelho por transformações de Fourier (FTIR), onde foram analisados os picos dentro das bandas de interesse nos valores de 1.646 cm-1 e 1.731 cm-1, correspondentes às ligações C=C alifática e C=O respectivamente. Os resultados foram submetidos à análise estatística de Variância e teste de Tukey (a = 0,05), os quais permitiram concluir que: a contração de polimerização de diferentes materiais (Filtek Z250 e Filtek P60) apresentou comportamento diferente mediante a mesma fonte luz (LED); o grau de conversão dos materiais apresentou-se estatisticamente semelhante em relação aos materiais e aparelhos fotopolimerizadores; o aparelho LED (Ultrablue IS) apresentou resultados de... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

Made available in DSpace on 2014-06-11T19:24:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-02-19Bitstream added on 2014-06-13T20:12:03Z : No. of bitstreams: 1 alencarjunior_ea_me_arafo_prot.pdf: 747787 bytes, checksum: fd32e276778e87934566a313af1035b5 (MD5) / O objetivo desta pesquisa foi avaliar a influência da distância de uma fonte de luz halógena na microdureza superficial da resina composta, considerando as superfícies de topo e base dos corpos-de-prova. Foram utilizadas duas marcas comerciais de resina composta, Z250 de partículas pequenas e uma resina de micropartícula, A110, ambas da 3M do Brasil Ltda. O aparelho de ativação da resina composta foi K&M 220- R, cuja intensidade de luz possui um pulso que variava após os 5 primeiros segundos assim alcançando sua intensidade máxima que foi medida em 720 mW/cm2. Para a determinação da intensidade de luz emitida pelo aparelho fotoativador, utilizou-se um radiômetro (Medidor de irradiância 150- CMC , São Carlos - SP). Corpos-de-prova foram confeccionados utilizado-se matrizes metálicas que possuíam um orifício central de 4mm de diâmetro por 2mm de espessura. As resinas foram inseridas no orifício da matriz metálica, em um único incremento, por meio de uma espátula metálica e sobre elas foi sobreposta uma tira matriz transparente de poliéster e, após isto, um peso de 1 Kg foi posto em cima da tira para que houvesse uma melhor condensação da resina composta evitando a presença de bolhas de ar, no interior do corpo-de-prova. A fonte de luz halógena foi fixada em uma mesa de maneira que a saída da ponta de luz ficasse paralela à superfície do corpo-de-prova. Para provocar o distanciamento da fonte de luz, anéis metálicos confeccionados em latão, com espessuras que variavam de 2mm, 4mm e 8mm foram utilizados, os quais, após posicionados, eram removidos para não interferiem no dispersamento da luz. As distâncias imprimidas a fonte de luz na superfície da resina foram de 0mm(tocando a superfície), 2mm, 4mm e 8mm. Para cada uma destas distâncias, a intensidade de luz foi medida. Esta variou de intensidade de... . / The aim of this research was to evaluate the influence of the light tip distance in the superficial microhardness of the composite resin, considering the surfaces of top and base of the samples. Two commercial composite resin marks had been used, Z250 of small particles e a microparticle resin, A110, both of 3m of Brazil Ltda. The device of activation of the composite resin was K&M 220- R, whose intensity of light possess a pulse that varied the 5 first seconds after thus reaching its maximum intensity that was measured in 720 mW/cm2. For the determination of the intensity of light emitted for the fotoativador device, a radiometer (Measuring of irradiance 150- CMC was used, Is Carlos. SP). The samples had been confectioned used first metallic that had a central orifice of 4mm of diameter for 2mm of thickness. The resins had been inserted in the orifice of the metallic array, in an only increment, by means of a metallic spatula and on them a transparent first polyester strap was overlapped and, after this, one weight of 1 kg was rank in top of the strap so that it had one better condensation of the composite resin preventing the presence of air bubbles, in the inward of the body-of-test. The source of light was fixed in a table thus the output of the light tip was parallel to the surface of the body-of-test. To provoke distance from the light source, confectioned metallic rings in brass, with thickness that varied of 2mm, 4mm and 8mm had been used, which, after located, was removed to avoid concentration of light. The printed pitches the source of light in the surface of the resin had been of 0mm(on the surface), 2mm, 4mm and 8mm. For each one of these pitches, the light intensity was measured. This varied of intensity of 720 mW/cm2 for the tip touching the surface of the body-of-test, 650 mW/cm2 for in the distance of 2mm, 600 mW/cm2... (Complete abstract, click electronic address below).

Made available in DSpace on 2014-10-09T12:55:36Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:13Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:55:36Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:13Z (GMT). No. of bitstreams: 0 / O objetivo deste trabalho foi desenvolver matrizes epoxídicas e estudar os parâmetros de processo de cura para fabricação de compósitos poliméricos curados por feixe de elétrons. A fabricação de compósitos poliméricos estruturais pelo processo térmico necessita de um ciclo de cura de algumas horas e elevada temperatura, implicando num alto custo de produção. A tecnologia de cura por feixe de elétrons permite curar matrizes epoxídicas em poucos minutos à temperatura ambiente e proporcionar temperaturas de transição vítrea superiores às obtidas pelos sistemas curados pelo processo térmico. Neste trabalho foi utilizada uma resina epoxídica do tipo éter diglicidílico de bisfenol A (DGEBA) e o hexafluoroantimonato de diariliodônio como iniciador catiônico. O tempo do ciclo de cura do compósito polimérico obtido por feixe de elétrons foi de 40 minutos até completar uma dose total aproximada de 200kGy. O grau de cura e a temperatura de transição vítrea foram avaliados por técnicas de análise térmica. A temperatura de transição vítrea determinada por meio da técnica de termodinâmico-mecânica (DMTA) foi de 167ºC (tan ) e o grau cura de 96% obtido pela técnica de calorimetria exploratória diferencial (DSC). A mesma resina epoxídica curada pelo processo térmico por um período de 16 horas, com um endurecedor à base de anidrido, atingiu uma temperatura de transição vítrea de 125ºC (tan ). / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP