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Improving on our construction practices to promote sustainable development in engineering and to promote eco-friendly living is vital in the fight against global warming and associated problems. This study looked at one of the ways in which engineering can contribute to this fight through promoting the recycling of waste by-products such as fly ash (FA), on a larger scale in the cement and concrete industry, by utilizing the FA to the optimum. In this study concrete mixes of 25 MPa, 35 MPa and 50 MPa with FA partially substituting the cement at 30%, 40%, 50% and 60% were produced and numerous tests were performed to determine the optimum amount of FA that can be used and still obtain better or comparable concrete to ordinary concrete. Testing for concrete properties was conducted under laboratory conditions over a period of one year. In addition, a cost comparison between ordinary concrete and FA concrete was undertaken. The results obtained show that the increase in FA content influenced the rheological properties of fresh concrete favorable. The recorded slump increased with the increase of FA content. Increasing the FA content prolonged the setting of concrete, with the ordinary concrete taking 1 hour 45 min to set, compared to more than 2 hours for FA mixes. The FA increase had negligible effects on the air content of the concrete mixes. The drying shrinkage of concrete increased with the increase of FA content, with the strain ranging from 0,045% to 0,56%. The compressive strength results show that the control mixes with 30% FA content attained the highest compressive strength over a year. In some cases, the 40% FA strength was compatible to the 30% FA strength. The durability index results showed the control mix of 30% FA attaining better results for Oxygen Permeability Index and Sorptivity Index, with the 40% FA mix following closely. The higher FA content mixes (50% and 60%) attained better Chloride Conductivity results than the lower FA content mixes. Increasing the FA content does affect the performance of the concrete at early stages, however concrete with acceptable strength and good durability qualities can be produced even with 50% FA volume. Increasing the FA content can also significantly reduce the cost of producing and working with concrete. The practice of utilizing higher FA content in concrete can be beneficial for the South African cement and concrete industry without compromising the quality of the cement products concrete structures. / M

This dissertation investigates the level of acid‐resistance of concrete degradation. Concrete specimens obtained from four mixtures (M1, M2, M3 and M4) were prepared with calcareous, siliceous and a blend of calcareous and silica sand; and then, tested in low (30 g/l) and highly (200 g/l) concentrated sulphuric acid solutions. To this end, an architecture of artificial neural networks (ANNs) was implemented to predict the performance of concrete specimens due to sulphuric acid solutions. Neural networks were composed with one hidden layer for one input and output layer. Nine input parameters were: cement composition, proportions of coarse and fine aggregates, water content, and compressive strength, weight loss of concrete, time impacting corrosion, acid concentration and sulphur concentration. Thickness expansion and concrete conductivity are used as output targets to evaluate the degree of deterioration. In this study, the learning through ANNs from training data sets have been proved to be better than measured data. Excellent results were found with a coefficient of determination (R2 ) of 0.9989, 0.9999, 0.9989 and 0.9998, respectively for the four mixtures M1, M2, M3 and M4 using siliceous aggregate. Also, the results show that two ANN models performed with both the thickness (expansion) and the electrical conductivity can successfully learn the prediction of concrete corrosion. In both low and highly concentrated sulphuric acid condition, the model thickness was more accurate in predicting concrete corrosion compared to the model conductivity. The lowest error in neural networks was provided by the mixture (M2) for the concrete using siliceous aggregate. For this purpose, the root mean squared error (RMSE) and the average absolute error (AAE) were of 0.0049 and 0.0048 % respectively. / College of Engineering, Science and Technology / M. Tech. (Chemical Engineering)

Shear strength of fiber reinforced concrete beams was studied in this research project. Three types of fibers were examined: hooked-end steel fiber, crimped-steel fiber, and crimped-monofilament polypropylene fibers. The experimental program included five beam specimens. Two of the beams were control specimens in which one was reinforced with minimum shear reinforcement according to ACI 318, while the other one did not have any shear reinforcement. Each one of the other three specimens was reinforced with one of the above mentioned fibers by 1% volumetric ratio. In addition to the beam specimens, three prisms were also made for each type fiber to determine their toughness. The aim of this research was to investigate the following questions for medium-high concrete strength 1) to evaluate the effectiveness of each type of fibers on the shear strength, 2) to investigate the shear strength, toughness, crack patterns and near ultimate load crack width of each beam, and 3) to determine if using 1% volumetric ratio of fibers as shear reinforcement in beams would provide adequate strength and stiffness properties comparable to reinforcing steel used as minimum shear reinforcement. The results showed that all three types of fibers increased the shear capacity of the beam specimens more than the beam reinforced with minimum shear reinforcement. Moreover, some of the fibers used could shift the type of failure from a pure shear failure to a combined flexural-shear or pure flexural failure.

No matter how inspection techniques have been advanced, manual visual inspection is currently still the first and fundamental step in assessing civil infrastructure. If no sign of deterioration has been spotted in manual inspection, any future inspection actions is not necessary to take. However, manual inspection has been identified with several limitations including the qualitative nature of inspection results, the time-consuming inspection process, and the heavy reliance on inspectors' and/or engineers' experience. In order to overcome these limitations, automated visual inspection systems have been proposed to enhance and/or replicate the manual inspection process. A number of image processing methods have been developed in detecting defects (i.e. coating rusts) and damage (i.e. cracks) on civil infrastructure. Their effectiveness has been verified in inspecting structures, such as bridges, underground pipes, and tunnels. Although existing methods are effective in finding defects and damage from digital images, missing two important links limits their application for rapid infrastructure assessment and rehabilitation. The first link is the correlation between the defects/damage and the structural members that the defects/damage lie on. The second link is the relationship between the defects/damage and their impacts on the structural members. The purpose of this research is to investigate the way of establishing these two links. It is focused on the retrieval of critical structural members and defects/damage information from images/videos, and then the utilization of this information for automated and rapid assessment and rehabilitation of civil infrastructure. Specifically, a combination of techniques from the areas of visual pattern recognition, digital filtering, and machine vision have been used in order to develop a set of methods for concrete column recognition, crack properties retrieval, and air pockets and discoloration detection and evaluation. The methods proposed in this research were implemented in a Microsoft Visual Studio environment, and tested on the real images/videos of concrete structures inflicted with cracks, air pockets and discoloration. The test results indicated that the methods could automatically recognize concrete columns, correctly measure the properties of the cracks in a crack map, and accurately evaluate the impacts of air pockets and discoloration on the visual quality of concrete surfaces.

A special problem in many reinforced concrete structures built in the 1970s and earlier is the lack of continuity between elements. Continuity is a characteristic of structures essential to preventing collapse. Therefore, in extreme loading conditions such as loss of a column support due to terrorist attack or if earthquake or other extreme actions occur, the structures could be vulnerable to collapse. The study reported here focused on two structural discontinuities in existing reinforced concrete structures, discontinuity in bottom reinforcement in beams (horizontal discontinuity) and poorly detailed lap splices in columns (vertical discontinuity). The objective of this study was to develop rehabilitation methods using CFRP to provide continuity of reinforcement in existing structures. To develop the rehabilitation methods, two separate experimental studies were conducted using beam and column specimens. CFRP materials were applied to the bottom or side face of a beam and anchored using CFRP anchors or U-wraps to provide horizontal continuity in bottom reinforcement and tested under dynamic loading. After CFRP rehabilitation, the ductility of the bottom reinforcement and large rotational capacity of the beam were realized. CFRP materials were also applied to the lap splice region in square and rectangular columns which exhibited a brittle splice failure as-built. After rehabilitating the columns using CFRP jackets and anchors, the failure mode changed from a brittle splice failure to yield of column reinforcement, and the strength and deformation capacity were improved under both monotonic and cyclic loading. Based on the results of beam and column tests, design guidelines for CFRP rehabilitation were proposed. Horizontal and vertical continuities can be provided through the use of CFRP for rehabilitating existing reinforced concrete structures that were designed prior to the introduction of codes that require continuous reinforcement along members and between adjacent members. The vulnerability of such structures to collapse can be reduced through rehabilitation. / text

M. Tech. Civil Engineering. / Evaluates various laboratory test methods to assess rutting potential in the hot-mix asphalt (HMA) and the effects of compaction methods. To achieve this objective, rutting potential of HMA samples prepared and compacted in the laboratory, and in the field was evaluated using different laboratory test methods under a range of temperatures and loads.

A retirada das fôrmas e do escoramento de estruturas de concreto armado só pode ser realizada quando o concreto estiver suficientemente endurecido para resistir às ações que sobre ele atuarem e não conduzir a deformações inaceitáveis. Estes são dois condicionantes importantes impostos pela norma brasileira NBR 14931 de 2004. Para o atendimento dessas condições, o responsável pelo projeto da estrutura deve informar ao responsável pela execução da obra os valores mínimos de resistência à compressão e módulo de elasticidade que devem ser obedecidos, concomitantemente, para a retirada das fôrmas e do escoramento em determinada idade. Para se determinar a resistência à compressão in loco dos concretos em elementos estruturais é comum o recurso a ensaios destrutivos realizados em corpos de provas padronizados confeccionados do mesmo concreto que será utilizado neste elemento. Esta situação, entretanto, não configura um estrito atendimento às demandas da norma brasileira, já que são diferentes as condições dos ensaios daquelas encontradas no elemento. A presente pesquisa discute possibilidades de atendimento a estas exigências através da utilização de ensaios não destrutivos com ondas ultrassônicas associado com ferramentas de inteligência artificial. Embora o teste de ultrassom seja relativamente simples de se executar, a interpretação dos seus resultados encerra importantes dificuldades, uma vez que são influenciados por vários fatores. A pesquisa, então, explorou a possibilidade de agregar as potencialidades das simulações com Redes Neurais Artificiais com ensaios não destrutivos de ultrassom para a estimativa da resistência à compressão do concreto. Duas linhas de ação distintas foram seguidas: uma linha experimental e outra linha computacional. No programa experimental, foram confeccionados nove diferentes traços de concreto, moldados 162 corpos de prova de 10x20 cm e confeccionados 27 prismas com dimensão de 25x25x50 cm. Os corpos de prova foram rompidos em compressão em três idades diferentes 7, 28 e 60 dias e foram realizadas leituras de ultrassom nos prismas nestas mesmas idades. De posse dos resultados do programa experimental, foram realizadas simulações computacionais com Redes Neurais Artificiais com vistas à obtenção de um mapeamento entre as variáveis de entrada do problema - comprimento dos prismas, teor de metacaulim, diâmetro dos agregados, idade dos corpos de prova e velocidade ultra-sônica e a variável de saída de interesse a resistência à compressão. Os resultados obtidos mostraram que a simulação com redes neurais associada a ensaios de ultrassom se constituem em importantes ferramentas para se avaliar a resistência à compressão de concretos / Stripping of formworks in reinforced concrete structures can only be done when concrete is hardened enough to carry the loads without generating unacceptable deformations. These are two important demands from Brazilian Code NBR 14931-2004. To get those conditions the structural design engineer should inform the building engineer the minimum values of compressive strength and elasticity modulus that must be obtained, simultaneously, to strip of the formworks on the specified age. To determine the in situ compressive strength of concrete in an specific structural elements is usual to perform destructive tests using test standard samples made with the same concrete that will be used in the element. This situation, however, does not configure a strict attendance to the demands of the Brazilian Code since the conditions of the tests in standard samples are quite different from the concrete in the structural element. The research discusses the possibilities to adopt and follow those requirements using non destructive ultrasonic waves tests associated with artificial intelligence tools. Although the ultrasound test is relatively simple to perform, the interpretation of its results brings important difficulties, since it is influenced by several factors. The research, then, explored the possibility to use potentialities of Artificial Neural Nets simulations associated with ultrasonic wave tests to estimate compressive strength of the concretes. Two distinct ways to investigate the subject were used: experimental and numerical computational simulation. In the experimental program, nine different concrete mixtures, 162 standard test samples 10x20 cm and 27 prisms with dimension of 25x25x50 cm were made. The test samples were tested in direct compression on three different ages - 7, 28 and 60 days - and ultrasonic wave tests were made in the prisms on the same ages. With the results from experimental tests, computational simulations using Artificial Neural Networks to obtain a mapping among the problem variables length of the prisms, metacaulim content, aggregate diameter, age of the test samples and ultrasonic speed - and the output properties which was the compressive strength of the concrete. Obtained results showed that the simulations with Artificial Neural Networks together with ultrasonic wave tests are import tools that can help engineers to evaluate the compressive strength of in situ concrete

Made available in DSpace on 2017-06-01T17:57:29Z (GMT). No. of bitstreams: 1 dissertacao_rosely.pdf: 8656278 bytes, checksum: df7ba267702f306c1aff9abdbcb4d7f2 (MD5) Previous issue date: 2010-09-10 / Stripping of formworks in reinforced concrete structures can only be done when concrete is hardened enough to carry the loads without generating unacceptable deformations. These are two important demands from Brazilian Code NBR 14931-2004. To get those conditions the structural design engineer should inform the building engineer the minimum values of compressive strength and elasticity modulus that must be obtained, simultaneously, to strip of the formworks on the specified age. To determine the in situ compressive strength of concrete in an specific structural elements is usual to perform destructive tests using test standard samples made with the same concrete that will be used in the element. This situation, however, does not configure a strict attendance to the demands of the Brazilian Code since the conditions of the tests in standard samples are quite different from the concrete in the structural element. The research discusses the possibilities to adopt and follow those requirements using non destructive ultrasonic waves tests associated with artificial intelligence tools. Although the ultrasound test is relatively simple to perform, the interpretation of its results brings important difficulties, since it is influenced by several factors. The research, then, explored the possibility to use potentialities of Artificial Neural Nets simulations associated with ultrasonic wave tests to estimate compressive strength of the concretes. Two distinct ways to investigate the subject were used: experimental and numerical computational simulation. In the experimental program, nine different concrete mixtures, 162 standard test samples 10x20 cm and 27 prisms with dimension of 25x25x50 cm were made. The test samples were tested in direct compression on three different ages - 7, 28 and 60 days - and ultrasonic wave tests were made in the prisms on the same ages. With the results from experimental tests, computational simulations using Artificial Neural Networks to obtain a mapping among the problem variables length of the prisms, metacaulim content, aggregate diameter, age of the test samples and ultrasonic speed - and the output properties which was the compressive strength of the concrete. Obtained results showed that the simulations with Artificial Neural Networks together with ultrasonic wave tests are import tools that can help engineers to evaluate the compressive strength of in situ concrete / A retirada das fôrmas e do escoramento de estruturas de concreto armado só pode ser realizada quando o concreto estiver suficientemente endurecido para resistir às ações que sobre ele atuarem e não conduzir a deformações inaceitáveis. Estes são dois condicionantes importantes impostos pela norma brasileira NBR 14931 de 2004. Para o atendimento dessas condições, o responsável pelo projeto da estrutura deve informar ao responsável pela execução da obra os valores mínimos de resistência à compressão e módulo de elasticidade que devem ser obedecidos, concomitantemente, para a retirada das fôrmas e do escoramento em determinada idade. Para se determinar a resistência à compressão in loco dos concretos em elementos estruturais é comum o recurso a ensaios destrutivos realizados em corpos de provas padronizados confeccionados do mesmo concreto que será utilizado neste elemento. Esta situação, entretanto, não configura um estrito atendimento às demandas da norma brasileira, já que são diferentes as condições dos ensaios daquelas encontradas no elemento. A presente pesquisa discute possibilidades de atendimento a estas exigências através da utilização de ensaios não destrutivos com ondas ultrassônicas associado com ferramentas de inteligência artificial. Embora o teste de ultrassom seja relativamente simples de se executar, a interpretação dos seus resultados encerra importantes dificuldades, uma vez que são influenciados por vários fatores. A pesquisa, então, explorou a possibilidade de agregar as potencialidades das simulações com Redes Neurais Artificiais com ensaios não destrutivos de ultrassom para a estimativa da resistência à compressão do concreto. Duas linhas de ação distintas foram seguidas: uma linha experimental e outra linha computacional. No programa experimental, foram confeccionados nove diferentes traços de concreto, moldados 162 corpos de prova de 10x20 cm e confeccionados 27 prismas com dimensão de 25x25x50 cm. Os corpos de prova foram rompidos em compressão em três idades diferentes 7, 28 e 60 dias e foram realizadas leituras de ultrassom nos prismas nestas mesmas idades. De posse dos resultados do programa experimental, foram realizadas simulações computacionais com Redes Neurais Artificiais com vistas à obtenção de um mapeamento entre as variáveis de entrada do problema - comprimento dos prismas, teor de metacaulim, diâmetro dos agregados, idade dos corpos de prova e velocidade ultra-sônica e a variável de saída de interesse a resistência à compressão. Os resultados obtidos mostraram que a simulação com redes neurais associada a ensaios de ultrassom se constituem em importantes ferramentas para se avaliar a resistência à compressão de concretos

In recent years the use of carbon fiber reinforcing polymers (CFRP) to repair damaged structural components has become more accepted and practiced. However, the current reference for designing FRP systems to repair and strengthen reinforced concrete (RC) and prestressed concrete (PSC) girders has limitations. Similarly, very few resources address solutions for the debonding problem associated with CFRP laminates or the use of CFRP laminates to repair structural members with pre-existing damage. The included experimental program consists of testing both RC and PSC girders with simulated lateral damage and CFRP repairs. A total of 34 RC beams were statically tested under a 4-point loading until failure and had cross-section dimensions of 5” x 10” (14cm x 25.4cm), were 8’ long (2.44m), and were reinforced with either #3 or #4 mild steel rebar. 13 PSC girders having cross-section dimensions representing a half-scaled AASHTO type II shape, were 20’ long (6.1m), and were prestressed with five 7/16” (11.1mm) diameter low-lax 7-wire strands. Ten of the PSC girders were statically loaded until failure under a 4-point testing setup, but 3 PSC girders were dynamically tested under fatigue loading using a 3-point arrangement. Different configurations of CFRP laminates, number and spacing of CFRP transverse U-wraps, and amount of longitudinal CFRP layers are studied. The results present the flexural behavior of all specimen including load-deflection characteristics, strain characteristics, and modes of failure. Ultimately, results are used to recommend important considerations, needed criteria, and proper design procedures for a safe and optimized CFRP repair configuration.