Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-26Bitstream added on 2014-06-13T20:16:15Z : No. of bitstreams: 1 santos_lf_me_ilha.pdf: 6137370 bytes, checksum: 5de758f11cce6406d87fe87638a96bb5 (MD5) / O concreto auto-adensável (CAA) é um material que representa um dos maiores avanços na tecnologia do concreto das últimas décadas. O desenvolvimento do CAA propiciou eficiência e melhora nas condições de trabalho em canteiro de obras e na indústria de pré-moldados. Do ponto de vista reológico, o CAA é uma mistura fluida que proporciona diferenças de comportamento quando comparado ao concreto convencional. Neste contexto, a proposta desta pesquisa foi estudar, num primeiro plano, as características reológicas nas fases de pasta, argamassa e concreto do CAA no estado fresco e seu comportamento no estado endurecido. Para isso, optouse por empregar a metodologia de Repette e Melo (2005), que considera a resistência à compressão como ponto de partida para a composição do traço do CAA e que estuda os aspectos reológicos envolvidos nas diferentes fases de sua dosagem. Os materiais empregados para estudo de dosagem foram o fíler basáltico como adição, areia média, brita 19 mm, aditivo superplastificante e dois tipos de cimento. Foram elaborados dois concretos, com cimentos distintos, ambos com mesma classe de resistência igual a 40 MPa. Num segundo plano, foi realizado um estudo da avaliação da resistência à compressão desses concretos quando submetidos à cura térmica a vapor, variando-se as temperaturas de cura (entre 65oC e 80oC), assim como o patamar isotérmico de cura em 4 h,6 h e 8 h para cada temperatura. A avaliação das propriedades mecânicas dos concretos foi realizada empregando o Método da Maturidade. No emprego da maturidade foram utilizados as funções de Nurse e Saul e a proposta por Freiesleben-Hansen e Pedersen (FHP). As análises comparativas foram realizadas em função do tipo de cimento empregado, temperatura de cura e tempo de patamar isotérmico / The self-compacting concrete (SCC) is a material that represents one of the greatest advances in concrete technology in recent decades. The development of SCC has resulted in improved efficiency and working conditions at the construction site and the precast industry. Rheological point of view, the SCC is a fluid mix that provides behavior differences when compared to conventional concrete. In this context, the proposal of this research was to study, in the foreground, the rheological phases of paste, mortar and concrete of SCC in the fresh state and its behavior in the hardened state. For this, we chose to employ the methodology Repette e Melo (2005), which considers the compressive strength as a starting point for the composition of the trace of SCC and studying the rheological aspects involved in the different stages of their dosage. The materials used to study the dosage was basalt fillers such as addition, medium sand, gravel 19 mm, superplasticizer additive and two types of cement. We prepared two concretes with different cements, both with the same strength class of 40 MPa. In the background, a study assessing the compressive strength of concrete when subjected to steam curing, varying the curing temperatures (between 65oC and 80oC) as well as the level of isothermal cure at 4 h, 6 h and 8 h for each temperature. The evaluation of mechanical properties of concrete was carried out using the Maturity Method. Employment of maturity was used to Nurse e Saul function, as well as function proposed by Freiesleben-Hansen and Pedersen (FHP). Comparative analysis were performed according to the type of cement used, curing temperature and isothermal plateau

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No. of bitstreams: 2 Dissertação - Mário Henrique Gomes Brito - 2013.pdf: 6257761 bytes, checksum: 3ff568c727b44a8a7e645c8475216a03 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-04-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The overall objective of this research, which was essentially experimental, is to study the influence of the isothermal period and the maximum temperature of the thermal cure cycle steam under atmospheric pressure in the development of compressive strength of concrete blocks over time. The influences of two other types of curing are also being investigated; curing by enveloping with plastic sheet and open air curing, considered the last case scenario for reference. This study specifically aimed to further our understanding on how to; a) evaluate and quantify the importance of adopting procedures for curing the average resistance (Fbm) and characteristic (fbk) strength to compression of concrete blocks, comparing the processes of thermal curing and curing by enveloping plastic sheet to open air curing; b) evaluate statistically the aging effect of blocks over its compressive strength; c) evaluate the interaction effects of the variables "type of cure" and "age analysis" of the results of compressive strength of concrete blocks; and d) identify the main changes in the microstructure of the blocks subjected to a thermal curing process, especially observing eventual delayed ettringite formation in the internal structure of the material. To examine the influence of maximum curing temperature, two levels were adopted; 65°C and 85°C. As for analyzing the influence of isothermal period, three levels were adopted; 3 hours, 4 hours and 5 hours. The age analysis was evaluated in five levels; 1, 3, 7, 28 and 91 days. The results showed that the worst condition for curing, or curing type, was the open air curing (curing time approximately equal to 24 hours), which led to a lower overall average result of compressive strength of concrete blocks, proving the importance of adopting procedures of curing to optimize the mechanical performance of concrete blocks. Furthermore, it was also determined that the best curing conditions were the curing with enveloping plastic sheet (curing time approximately equal to 24 hours) and the thermal curing with steam under atmospheric pressure isotherm of 65°C and isothermal period of 3 hours (curing time approximately equals 8.5 hours), which were considered statistically equal. It was also observed that there was no significant influence of the curing in maximum temperature in relation to the compressive strength of the blocks. In the other hand, the isothermal period was very significant; the best condition was 3 hours, while 4 hours and 5 hours were considered statistically equal. Regarding the delayed ettringite formation, it was only verified for thermal curing conditions of isothermal of 85°C and isothermal period of 4 hours and 5 hours. / O objetivo geral desta pesquisa, de caráter essencialmente experimental, é estudar a influência do período isotérmico e da temperatura máxima do ciclo de cura térmica a vapor sob pressão atmosférica no desenvolvimento da resistência à compressão de blocos de concreto ao longo do tempo. Paralelamente, foram investigadas ainda as influências de dois outros tipos de cura, a saber: cura por envelopamento com lona plástica e cura ao ar livre, considerada esta última a situação de referência. De modo específico, o estudo visou ainda: a) avaliar e quantificar a importância da adoção de procedimentos de cura nas resistências média (fbm) e característica (fbk) à compressão de blocos de concreto, comparando os processos de cura térmica e cura por envelopamento com lona plástica com a cura ao ar livre; b) avaliar estatisticamente o efeito da idade dos blocos sobre a sua resistência à compressão; c) avaliar a interação dos efeitos das variáveis “tipo de cura” e “idade de análise” sobre os resultados de resistência à compressão dos blocos de concreto; e d) identificar as principais transformações ocorridas na microestrutura dos blocos submetidos aos processos de cura térmica, em especial observando eventual formação de etringita tardia na estrutura interna do material. Para analisar a influência da temperatura máxima de cura, foram adotados dois níveis: 65°C e 85°C. Já para analisar a influência do período isotérmico, foram adotados três níveis: 3 horas, 4 horas e 5 horas. Por sua vez, a idade de análise foi avaliada em cinco níveis: 1, 3, 7, 28 e 91 dias. Os resultados mostraram que a pior condição de cura, ou seja, o tipo de cura que conduziu ao menor resultado médio global de resistência à compressão dos blocos de concreto, foi a cura ao ar livre (tempo de cura aproximadamente igual a 24 horas), comprovando a importância da adoção de procedimentos de cura para a otimização do desempenho mecânico dos blocos de concreto. Além disso, foi verificado ainda que as melhores condições de cura foram a cura por envelopamento com lona plástica (tempo de cura aproximadamente igual a 24 horas) e a cura térmica a vapor sob pressão atmosférica com isoterma de 65°C e período isotérmico de 3 horas (tempo de cura aproximadamente igual a 8,5 horas), os quais foram considerados, estatisticamente, iguais. Também foi verificado que não houve influência significativa da temperatura máxima de cura em relação à resistência à compressão dos blocos. Já o período isotérmico foi significativo, de modo que a melhor condição foi 3 horas, enquanto 4 horas e 5 horas foram considerados, estatisticamente, iguais. Quanto à formação de etringita tardia, esta só foi verificada para as condições de cura térmica com isoterma de 85°C e períodos isotérmicos de 4 horas e 5 horas.

The work deals with the determination of optimal curing temperature by powder coating. The thesis includes a literary study of powder coating. In the experimental part of the thesis will be performed pre-treatment and coated several test samples. It will be carried out verification of the properties of powdered coating

The thesis deals with the comparison and selection of a suitable system of curing powder coatings. The work includes a literature review focused on the issue of powder coating. In the experimental part of the work will be carried out techno-economic analysis of the suitability of each technology for curing parts in a conventional and catalytic infrared oven.

Thesis (M. Tech. - Engineering: Electrical, Department Electronic Engineering, Faculty of Engineering and Technology)--Vaal University of Technology. / Curing of materials in order to obtain different properties has been a practice for many years. New developments in composite materials increase the need to control certain variables during the curing process. One very significant variable is temperature. Temperature control by itself is an old practice, however when the need for repeatedly controlling the process accurately over long periods of time arises, a system is required that outperforms normal manual control. One of the aspects within such a system that needs to be considered is the ability to replicate the temperatures within an oven which were originally used for a specific material’s curing profile. This means that a curing profile would need to be defined, saved for later and finally be interpreted correctly by the controlling system. Different control methods were simulated to enable the system to control the temperature which has been defined by literature. This dissertation introduces a variation on the standard control methods and shows improved results. Switching the oven on and off in order to increase or decrease internal oven temperature seems simple, but can cause switching devices to decrease their operational life span, if not designed carefully. A combination switch was introduced which harnesses the advantages of two very common switching devices to form an improved combination switch. Software for the personal computer environment, as well as software for the embedded environment were developed and formed a control system that produced acceptable results for temperature control. Accuracies of 98% and more were achieved and found to be acceptable according to standard engineering control practices. An accurate temperature profile controller was designed, simulated and built in order to control the temperature inside a specific curing oven which, in turn, determined the curing properties of specific materials. The overall results were satisfactory which lead to achieving the objectives outlined in this dissertation.