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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Desenvolvimento de modelos de previsão de desempenho de pavimentos asfálticos com base em dados da rede de rodovias do Estado da Bahia / Development of performance prediction models for asphalt pavements based on data from the highway network of the State of Bahia, Brazil

Soncim, Sérgio Pacífico 28 June 2011 (has links)
O objetivo desta tese de doutorado foi desenvolver modelos de previsão de desempenho de pavimentos asfálticos para a malha rodoviária do Estado da Bahia. Os modelos de desempenho foram desenvolvidos para pavimentos em concreto asfáltico usinado a quente e em tratamento superficial duplo. Foram utilizadas informações de um banco de dados de gerência de rodovias do DERBA, coletados em 2004, e foram coletados dados complementares de irregularidade longitudinal em 2009, após o desenvolvimento de um planejamento fatorial específico para essa finalidade. Foram utilizadas duas formas de análise estatística dos dados para avaliar a significância dos fatores e definir os parâmetros dos modelos de desempenho: a Análise Exploratória de Dados (AED) e a Análise da Variância (ANOVA). Os fatores considerados foram a idade do pavimento, o tráfego e a pluviometria e os resultados da análise exploratória de dados corroboraram os resultados encontrados pela análise da variância, tanto em relação aos efeitos dos fatores como das interações. Os modelos de previsão do desempenho foram desenvolvidos para as variáveis dependentes Índice de Condição do Pavimento Flexível (ICPF) e Área Total de Trincas (ATT), para os pavimentos em concreto asfáltico usinado a quente, e os modelos de previsão de desempenho de Área de Desgaste (ADesg) e Irregularidade Longitudinal (IRI BA), para os trechos em tratamento superficial duplo. Para a irregularidade longitudinal, também foram desenvolvidos modelos de desempenho em separado, para regiões de clima semiárido a seco (IRIBAs) e clima subúmido a úmido (IRI BAÚ). Para a verificação da adequação dos modelos de previsão de desempenho foram utilizadas a análise de resíduos, o coeficiente de correlação (r) e o coeficiente de determinação (\'R POT.2\'). Os modelos de desempenho, desenvolvidos neste trabalho para a Área Total de Trinca (ATT) e para a Irregularidade Longitudinal, foram comparados com modelos de desempenho empíricos, utilizados em programas de gerência de pavimentos por organismos rodoviários, do Brasil e do exterior, e apresentaram melhores resultados. O modelo de Irregularidade Longitudinal (IRI BA) para a rede de rodovias em tratamento superficial duplo também foi comparado com modelo desenvolvido pelo Departamento de Infraestrutura de Transportes da Bahia - DERBA, com base em levantamentos para a priorização de trechos candidatos a atividades de manutenção e reabilitação, e apresentou melhor ajuste aos dados observados. No entanto, para que sejam obtidos ainda melhores resultados, quanto à previsão de desempenho dos pavimentos da rede de rodovias pavimentadas do Estado da Bahia, é necessário que sejam realizados novos levantamentos para alimentação do banco de dados, sugerindo-se estudos complementares que incluam fatores que não puderam ser considerados neste trabalho, como a capacidade estrutural, por exemplo. Recomenda-se que o método utilizado neste trabalho, baseado no planejamento fatorial, na Análise Exploratória de Dados e na Análise de Variância, seja repetido, pois se mostrou capaz de reduzir os custos da coleta de dados sem comprometer a precisão e acurácia dos modelos de desempenho obtidos. / The objective of this thesis was to develop performance prediction models for asphalt pavements in the State of Bahia. The performance models were developed for hot-mix asphalt (HMA) and double surface treatment (ST). Information was obtained from a database maintained by DERBA (State of Bahia Department of Transportation), with data collected in 2004, and from additional collection of data, mainly of pavement roughness, performed in 2009 and that was based on an experimental design for this specific purpose. Two statistical analyses were used to assess the significant factors and define the parameters of the performance models: Exploratory Data Analysis (EDA) and Analysis of Variance (ANOVA). The factors considered were age of the pavement, traffic volume and rainfall, and the results of the exploratory data analysis corroborated the results found by the analysis of variance, both in relation to the effects of factors such as of their interactions. The performance prediction models were developed for the dependent variables Pavement Condition Index (PCI) and Area of Total Cracks (ATC) for HMA pavements, and Raveling (R) and roughness (IRI BA) for ST pavements. For roughness, performance models were also developed considering, separately, two climate conditions: semiarid to arid (IRI BAa) and sub-humid to humid (IRI BAh). Residue analysis and calculation of correlation coefficient (r) and coefficient of determination (\'R POT.2\') were performed to verify the adequacy of performance prediction models. The performance models developed in this work for Area of Total Cracks (ATC) and roughness (IRI) were compared with empirical performance models used for pavement management in Brazilian and foreign highway agencies, and they presented the best results. The performance model for roughness (IRI BA) in ST pavements was also compared to a prediction model developed by DERBA using data collected by a maintenance and rehabilitation activities prioritization program and it presented the best fit to the observed data. However, to obtain even better results regarding the performance prediction of asphalt pavements in the State of Bahia, it is necessary to conduct new field surveys to feed the database and be used in further studies that include factors that could not be considered in this work, as structural capacity, for example. It is recommended that the method used in this work, based on factorial design, Exploratory Data Analysis and ANOVA, be repeated, because it proved capable of reducing the costs of data collection without compromising precision and accuracy of the obtained performance prediction models.
32

Modelos de desempenho de pavimentos: estudo de rodovias do Estado do Paraná / not available

Yshiba, José Kiynha 04 April 2003 (has links)
A tomada de decisão em gerência de pavimentos depende, dentre outros fatores, da estimativa da evolução da condição do pavimento ao longo do tempo. Tal estimativa é obtida por uma função que relaciona as causas e os efeitos da deterioração dos pavimentos, denominada modelo de desempenho. Neste trabalho são desenvolvidos modelos estatísticos para previsão do desempenho de pavimentos, mediante o estabelecimento de equações de regressão tendo por base dados históricos de avaliações da condição da malha rodoviária do Estado do Paraná. A análise do comportamento dos pavimentos é efetuada utilizando-se uma programação fatorial que, através de análise de variância (ANOVA), permite a determinação do nível de significância de fatores pré-selecionados (variáveis independentes: tráfego, idade e estrutura do pavimento) e de suas interações, bem como a modelagem do desempenho dos pavimentos (variáveis dependentes: irregularidade longitudinal e condição estrutural). Para cada uma das células da matriz fatorial, que correspondem às combinações dos fatores considerados, também são desenvolvidos modelos probabilísticos para previsão do desempenho de pavimentos, a partir de avaliações realizadas por especialista (engenheiros do DER-PR) e mediante o estabelecimento de matrizes de probabilidade de transição de Markov. Este trabalho mostra que é possível o desenvolvimento de modelos de desempenho sem dados históricos de avaliação da condição dos pavimentos ou tendo-se apenas dados coletados por um curto período de tempo. Observa-se, também, boa concordância entre os modelos estatísticos e probabilísticos, particularmente para previsão do desempenho funcional dos pavimentos. Os modelos de desempenhos desenvolvidos neste trabalho, quando comparados com equações desenvolvidas por pesquisadores e órgãos rodoviários brasileiros e estrangeiros, apresentaram melhores resultados, evidenciando as limitações de modelos de desempenho desenvolvidos e calibrados sob condições específicas. / The decision-making in pavement management systems depends, among other factors, of the prediction of the pavement condition during the service life. This prediction is obtained through a relation between causes and effects of pavement deterioration, called performance prediction model. This work develops statistic models for the predicion of pavement performance, based on regression equations from data of pavement evaluation performed in the highway network of the State of Paraná-Brazil. The pavement behavior is evaluated from an Analysis of Variance (ANOVA) of a factorial array, which calculates the level of significance of preselected factors (independent variables: traffic, age, and pavement structure) and their interactions and gives the performance models(dependent variables: roughness and structural condition). For each cell of the factorial array, that corresponds to combinations of the considered factors, it is also developed probabilistic models for the prediction of pavement performance, based on evaluations of pavement condition performed by specialists (State of Parana DOT engineers) and the definition of Markov transition matrices. This work shows that it is possible to develop performance prediction models without historic data of pavement evaluation or having just data colected in a short period of time. It is observed good correspondence between both models, statistic and probabilistic, particularly for the prediction of thefunctional behavior. The performance prediction models developed in this work show better results than equations developed by Brazilian and foreign researches and highway agencies, in a clear evidence of the limitation of models developed and calibrated under specific conditions.
33

Fracture and Fatigue Behavior of Geosynthetic Reinforced Asphalt Concrete for Pavement Overlays

Unknown Date (has links)
Flexible or asphalt pavements constitute nearly 94% of the 2.7 million miles of existing roadways in the United States. In a typical rehabilitation project, the existing asphalt pavement is milled up to a prescribed depth for removing the near surface distresses such as excessive cracking and rutting, and a new overlay is placed. The average time between resurfacing projects varies depending on the level of pavement deterioration which is significantly accelerated when poor subgrade conditions are encountered. The use of geosynthetic reinforcement within the new asphalt overlay is often perceived as a mitigation strategy that can delay the onset and propagation of reflection cracking, and also control the rutting and differential settlement. However, some mixed reviews about the performance of the geosynthetic reinforced overlays have been reported in the literature. In Phase I of this study, a laboratory investigation was conducted for evaluating the flexural fatigue behavior, permanent deformation response, and fracture characteristics of geogrid reinforced asphalt beam specimens made from a typical overlay material. The laboratory specimens included geogrid as a single-layer inclusion either at the bottom third depth or at the mid height, and as double-layer inclusion, with geogrid placed both at the bottom third and at the middle of the beam. In Phase II, a case study involving geogrid reinforced overlay constructed over a deteriorated pavement underlain by soft subgrade in southeastern Florida was numerically simulated. It was found that the geogrid reinforcement significantly improved the fatigue and fracture properties of the asphalt beams compared to unreinforced specimens. Results from numerical simulation demonstrated that the double reinforced overlay resulted in the minimum tensile stress at the bottom of the asphalt layer (reducing the cracking potential) and minimum vertical strain on the top of the subgrade (reducing the rutting potential), compared to unreinforced or bottom-third reinforced overlays. Accordingly, it is concluded that the double layer reinforcement of asphalt overlays with an appropriate geosynthetic product can be beneficial for the performance and long term preservation of the pavement system when soft soils are encountered. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
34

Ensaios comparativos de mistura asfáltica pré-misturado a frio com adição de borracha de pneu /

Silva, Simone Cristina Caldato da. January 2008 (has links)
Resumo: A mistura asfáltica, pode ser usinado a quente e pré-misturado a frio. A mistura denominada "pré-misturado", empregada no revestimento de pavimento é a mistura a frio, tendo como composição agregado mineral graduado, material de enchimento e emulsão asfáltica espalhada e comprimida a frio. Esse trabalho irá abordar a mistura asfástica pré-misturado a frio, tendo como objetivo comparar os resultados baseados em ensaios da mistura asfáltica e a caracterização do comportamento da mistura quando preparada com a adição de borracha reciclada de pneus usados. A pesquisa visa qualificar e otimizar o desempenho da mistura asfáltica que receberá a borracha moída com adições de 3%, 4% e 5% em relação à massa total de agregados minerais, comparando-as com a mistura de referência, sem a adição da borracha. A destinação final da borracha constitui em todo o mundo em um grande desafio, em virtude de suas peculiaridades, como seu tempo de degradação, estimado em aproximadamente 600 anos. Além da quantidade gerada nos dias de hoje, volume, peso e principalmente grande dificuldade de alternativas consideradas ecologicamente corretas e economicamente viáveis. Os ensaios realizados baseiam-se em uma faixa de pré-misturado a frio, onde os corpos de prova foram produzidos em laboratório com emulsão asfáltica catiônica. A adição da borracha moída e os teores de emulsão asfáltica foram definidos e analisados após ensaio de Dosagem Marshall a Frio. As características e comportamento das misturas foram avaliados pela densidade da mistura asfáltica, estabilidade e fluência Marshall. Dessa forma, buscando uma alternativa a atender as normas brasileiras e resultados de desempenho dessas misturas asfálticas, conclui-se que... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The asphalt paving mixture can be produced in the heat and premixed in cold. The mixture called premixed, having as mineral aggregate composition graduated, stuffing material and the asphalt emulsion compressed in cold. This work will go to approach the premixed in cold of the asphalt misture, having as objective to compare the results based on assays of the asphalt mixture and the behavior misture characterization when it prepared with the recycled rubber of old tires. The research seeks to qualify and optimize the performance of the asphalt mixture thet will receive the crushed rubber with additions of 3%, 4% and 5% in relation to the total agregate mineral mass, comparing them with the reference mixture, without the rubber addition. The final destination of the rubber to consist of a great challenge all over the world, in virtue of its peculiarities, as its time of degradation, approximately esttmed in 600 years. Beyond the generated amount nowadays, volume, weight and mainly great difficult of considered alternatives correct ecologically and viable economically. The accomplishment rehearsals based on in a strip premixed in cold, called dense strip, where the specimens were produced on the lab wiyh the cationic asphalt emulsion. The crushed rubber addition and the asphalt emulsion texts had been defined and analyzed after rehearsal of in cold Marshall Dosage. The mixture characteristics and behaviour had been evaluated by the stability, Marshall fluency and asphalt mixture density. In the way, looking for an alternative to attend the Brazillians rules and results of performance of these asphalt paving mixture, it follows that the rubber addition benefits are considerable, where the line with 3% addition rubber it presented the smallest index of emptiness, to smallest fluency, the biggest stability Marshall, the biggest apparent density, the biggest relationship polishemptiness and the smallest tenor of emulsion asphalt. / Orientador: Eduardo Carlos Bianchi / Coorientador: Emílio Shizuo Fujikawa / Banca: Rosane Aparecida Gomes Battistelle / Banca: Bernardo Luiz Costas Fumio / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Mestre
35

Modelos de desempenho de pavimentos: estudo de rodovias do Estado do Paraná / not available

José Kiynha Yshiba 04 April 2003 (has links)
A tomada de decisão em gerência de pavimentos depende, dentre outros fatores, da estimativa da evolução da condição do pavimento ao longo do tempo. Tal estimativa é obtida por uma função que relaciona as causas e os efeitos da deterioração dos pavimentos, denominada modelo de desempenho. Neste trabalho são desenvolvidos modelos estatísticos para previsão do desempenho de pavimentos, mediante o estabelecimento de equações de regressão tendo por base dados históricos de avaliações da condição da malha rodoviária do Estado do Paraná. A análise do comportamento dos pavimentos é efetuada utilizando-se uma programação fatorial que, através de análise de variância (ANOVA), permite a determinação do nível de significância de fatores pré-selecionados (variáveis independentes: tráfego, idade e estrutura do pavimento) e de suas interações, bem como a modelagem do desempenho dos pavimentos (variáveis dependentes: irregularidade longitudinal e condição estrutural). Para cada uma das células da matriz fatorial, que correspondem às combinações dos fatores considerados, também são desenvolvidos modelos probabilísticos para previsão do desempenho de pavimentos, a partir de avaliações realizadas por especialista (engenheiros do DER-PR) e mediante o estabelecimento de matrizes de probabilidade de transição de Markov. Este trabalho mostra que é possível o desenvolvimento de modelos de desempenho sem dados históricos de avaliação da condição dos pavimentos ou tendo-se apenas dados coletados por um curto período de tempo. Observa-se, também, boa concordância entre os modelos estatísticos e probabilísticos, particularmente para previsão do desempenho funcional dos pavimentos. Os modelos de desempenhos desenvolvidos neste trabalho, quando comparados com equações desenvolvidas por pesquisadores e órgãos rodoviários brasileiros e estrangeiros, apresentaram melhores resultados, evidenciando as limitações de modelos de desempenho desenvolvidos e calibrados sob condições específicas. / The decision-making in pavement management systems depends, among other factors, of the prediction of the pavement condition during the service life. This prediction is obtained through a relation between causes and effects of pavement deterioration, called performance prediction model. This work develops statistic models for the predicion of pavement performance, based on regression equations from data of pavement evaluation performed in the highway network of the State of Paraná-Brazil. The pavement behavior is evaluated from an Analysis of Variance (ANOVA) of a factorial array, which calculates the level of significance of preselected factors (independent variables: traffic, age, and pavement structure) and their interactions and gives the performance models(dependent variables: roughness and structural condition). For each cell of the factorial array, that corresponds to combinations of the considered factors, it is also developed probabilistic models for the prediction of pavement performance, based on evaluations of pavement condition performed by specialists (State of Parana DOT engineers) and the definition of Markov transition matrices. This work shows that it is possible to develop performance prediction models without historic data of pavement evaluation or having just data colected in a short period of time. It is observed good correspondence between both models, statistic and probabilistic, particularly for the prediction of thefunctional behavior. The performance prediction models developed in this work show better results than equations developed by Brazilian and foreign researches and highway agencies, in a clear evidence of the limitation of models developed and calibrated under specific conditions.
36

INNOVATIVE NONDESTRUCTIVE TESTING (NDT) FOR CONDITION ASSESSMNET OF LONGITUDINAL JOINTS IN ASPHALT PAVEMENTS

Jiang, Zhiyong January 2007 (has links)
The failure of longitudinal construction joints is one of the critical factors causing accelerated pavement deterioration. Poor-quality longitudinal construction joints are often characterized by a difference in elevation between adjacent lanes or by unraveling of the hot mix asphalt (HMA). Current wave-based non-destructive testing (NDT) methods are efficient and economical for the evaluation of material properties. In this thesis, an innovative surface wave testing technique for condition assessment of longitudinal construction joints in asphalt pavements is presented. This method enables reduction of the number of cores required for large-strain testing and provision of a more uniform quality assessment of longitudinal joints as well as the relative condition of the asphalt pavements. The technical development is based on a theoretical study of the wave attenuation mechanisms and on the reported deficiencies in current seismic wave-based methods. Traditionally, the use of ultrasonic testing to determine small-strain elastic property for asphalt concrete was uniquely based on the measurement of wave velocity. However, isolated use of wave velocity does not provide complete information of the materials strength because of the different variables that affect the strength-velocity relationship. Therefore, it is necessary to complement velocity data with independent information such as the change in attenuation and frequency content of the propagating pulse. The existing deficiencies in current seismic wave-based methods were addressed to improve reliability, accuracy and consistency for asphalt concrete material characterization in the laboratory and in the field. Refined and improved signal processing techniques were used to overcome the shortcomings in the existing wave-based methods that contribute to uncertainties in the interpretation of test results. To capture more information from a wave, the signal was analyzed in the time and frequency domains. The basic analyses included a simple method such as peak to peak amplitude of the first cycle of arriving wave, and complex methods such as maximum magnitude and area of corresponding frequency spectrum through Fourier transform. A novel approach based on wavelet transform of the signal was presented, which provides an alternative method to determine wave characteristics. Material characterization tests (experiment Phase I) were carried out to study the relationship between the wave characteristics obtained from UPV test and the quality of the asphalt concrete specimens prepared in the laboratory. The specimens were identical in terms of aggregate and asphalt binder ratio, but varying in volumetric properties produced by different compaction efforts. The specimen quality was determined using two methods: 1) the traditional method using density measurement and 2) an innovative approach using dynamic modulus which is recommended by the Federal Highway Administration (FHWA) for use as a fundamental material property for characterizing Superpave mixes (Witczak, et al., 2002; Bonaquist et al., 2003; Christensen et al., 2004). The measured wave characteristics showed excellent correlations (R2 > 0.9) with the fundamental properties of the mix. The results revealed that the wave amplitude parameters as the condition index have the potential to provide a reliable assessment of the quality of HMA mixtures. The finding is very critical to moving the technology forward in the right direction, and form an important basis for the experiment Phase II. Experiment Phase II investigated the feasibility and effectiveness of using the wave characteristics identified in experiment Phase I to assess the condition of longitudinal construction joints. Particular attention was given to examining the sensitivity of the wave-based technique to different types of construction joints. For this purpose, three types of construction joints (good, fair and poor) were fabricated in the laboratory and identified using the wave-based technique. The research was intended to develop a suitable test procedure for condition assessment the longitudinal joints in asphalt pavement in the field. The data from experiment Phase II revealed that the wave-based technique enables assessment of not only the quality of different types of longitudinal construction joints but also the relative condition of asphalt pavements.
37

Porous Asphalt Pavement Designs: Proactive Design for Cold Climate Use

Schaus, Lori Kathryn January 2007 (has links)
Porous asphalt pavements offer an alternative technology for stormwater management. A porous asphalt pavement differs from traditional asphalt pavement designs in that the structure permits fluids to pass freely through it, reducing or controlling the amount of run-off from the surrounding area. By allowing precipitation and run-off to flow through the structure, this pavement type functions as an additional stormwater management technique. The overall benefits of porous asphalt pavements may include both environmental and safety benefits including improved stormwater management, improved skid resistance, reduction of spray to drivers and pedestrians, as well as a potential for noise reduction. With increasing environmental awareness and an evolving paradigm shift in stormwater management techniques, this research aims to provide guidance for Canadian engineers, contractors, and government agencies on the design of porous asphalt pavement structures. One of the keys to the success of this pavement type is in the design of the asphalt mix. The air void percentage, which is ultimately related to the effectiveness of the pavement to adequately control the runoff, is a critical component of the mix. However, special consideration is required in order to obtain higher air void percentages while maintaining strength and durability within a cold climate. The objectives of this study were to evaluate several laboratory porous asphalt mix designs for durability and strength in cold climate conditions. The porous asphalt mixes consisted of a porous asphalt Superpave mix design method whereby the asphalt binder type was varied. Performance testing of the porous asphalt including draindown susceptibility, moisture-induced damage susceptibility, dynamic modulus, and permeability testing were completed. Based on the preliminary laboratory results, an optimal porous asphalt mix was recommended for use in a Canadian climate. Initial design guidelines for porous asphalt were provided based on preliminary findings and hydrological analysis.
38

ALTERNATIVA ASFALTSBELÄGGNINGAR : Möjligheten att använda icke petroleumbaserade bindemedel / Alternative asphalt pavements

Norrlander, Pontus January 2012 (has links)
This report investigates the possibility to use non-petroleum based adhesive (biobitumen) in asphalt. The main reasons for replacing bitumen are the fact that oil prices are rising, the threat of peak oil and the fact that the asphalt industry is becoming more environmentally friendly. The main purpose of this report is to investigate whether there are any non-petroleum based adhesives on the market. If so, how can they be used? The questions covered are: • Are there any other alternative asphalt coatings available? • Can bio-oils be used in asphalt? • If the bio-oils can be used, what are the details their properties? • How does a cold climate affect the bio binders? • What is the Swedish asphalt industry’s opinion about bio asphalt? The project was concluded through literature studies, consultations with people in the asphalt industry and through several interviews. The conclusion of this report is that there are some existing non-petroleum based adhesives on the market. They are mainly used for bike paths, sidewalks and parkareas. The biggest problem for greater use is the fact that it is expensive and performance in cold climate is unknown. The study indicates that Sweden could have a new potential industry in the field of producing bio-adhesives from both wood and waste from paper industry
39

INNOVATIVE NONDESTRUCTIVE TESTING (NDT) FOR CONDITION ASSESSMNET OF LONGITUDINAL JOINTS IN ASPHALT PAVEMENTS

Jiang, Zhiyong January 2007 (has links)
The failure of longitudinal construction joints is one of the critical factors causing accelerated pavement deterioration. Poor-quality longitudinal construction joints are often characterized by a difference in elevation between adjacent lanes or by unraveling of the hot mix asphalt (HMA). Current wave-based non-destructive testing (NDT) methods are efficient and economical for the evaluation of material properties. In this thesis, an innovative surface wave testing technique for condition assessment of longitudinal construction joints in asphalt pavements is presented. This method enables reduction of the number of cores required for large-strain testing and provision of a more uniform quality assessment of longitudinal joints as well as the relative condition of the asphalt pavements. The technical development is based on a theoretical study of the wave attenuation mechanisms and on the reported deficiencies in current seismic wave-based methods. Traditionally, the use of ultrasonic testing to determine small-strain elastic property for asphalt concrete was uniquely based on the measurement of wave velocity. However, isolated use of wave velocity does not provide complete information of the materials strength because of the different variables that affect the strength-velocity relationship. Therefore, it is necessary to complement velocity data with independent information such as the change in attenuation and frequency content of the propagating pulse. The existing deficiencies in current seismic wave-based methods were addressed to improve reliability, accuracy and consistency for asphalt concrete material characterization in the laboratory and in the field. Refined and improved signal processing techniques were used to overcome the shortcomings in the existing wave-based methods that contribute to uncertainties in the interpretation of test results. To capture more information from a wave, the signal was analyzed in the time and frequency domains. The basic analyses included a simple method such as peak to peak amplitude of the first cycle of arriving wave, and complex methods such as maximum magnitude and area of corresponding frequency spectrum through Fourier transform. A novel approach based on wavelet transform of the signal was presented, which provides an alternative method to determine wave characteristics. Material characterization tests (experiment Phase I) were carried out to study the relationship between the wave characteristics obtained from UPV test and the quality of the asphalt concrete specimens prepared in the laboratory. The specimens were identical in terms of aggregate and asphalt binder ratio, but varying in volumetric properties produced by different compaction efforts. The specimen quality was determined using two methods: 1) the traditional method using density measurement and 2) an innovative approach using dynamic modulus which is recommended by the Federal Highway Administration (FHWA) for use as a fundamental material property for characterizing Superpave mixes (Witczak, et al., 2002; Bonaquist et al., 2003; Christensen et al., 2004). The measured wave characteristics showed excellent correlations (R2 > 0.9) with the fundamental properties of the mix. The results revealed that the wave amplitude parameters as the condition index have the potential to provide a reliable assessment of the quality of HMA mixtures. The finding is very critical to moving the technology forward in the right direction, and form an important basis for the experiment Phase II. Experiment Phase II investigated the feasibility and effectiveness of using the wave characteristics identified in experiment Phase I to assess the condition of longitudinal construction joints. Particular attention was given to examining the sensitivity of the wave-based technique to different types of construction joints. For this purpose, three types of construction joints (good, fair and poor) were fabricated in the laboratory and identified using the wave-based technique. The research was intended to develop a suitable test procedure for condition assessment the longitudinal joints in asphalt pavement in the field. The data from experiment Phase II revealed that the wave-based technique enables assessment of not only the quality of different types of longitudinal construction joints but also the relative condition of asphalt pavements.
40

Porous Asphalt Pavement Designs: Proactive Design for Cold Climate Use

Schaus, Lori Kathryn January 2007 (has links)
Porous asphalt pavements offer an alternative technology for stormwater management. A porous asphalt pavement differs from traditional asphalt pavement designs in that the structure permits fluids to pass freely through it, reducing or controlling the amount of run-off from the surrounding area. By allowing precipitation and run-off to flow through the structure, this pavement type functions as an additional stormwater management technique. The overall benefits of porous asphalt pavements may include both environmental and safety benefits including improved stormwater management, improved skid resistance, reduction of spray to drivers and pedestrians, as well as a potential for noise reduction. With increasing environmental awareness and an evolving paradigm shift in stormwater management techniques, this research aims to provide guidance for Canadian engineers, contractors, and government agencies on the design of porous asphalt pavement structures. One of the keys to the success of this pavement type is in the design of the asphalt mix. The air void percentage, which is ultimately related to the effectiveness of the pavement to adequately control the runoff, is a critical component of the mix. However, special consideration is required in order to obtain higher air void percentages while maintaining strength and durability within a cold climate. The objectives of this study were to evaluate several laboratory porous asphalt mix designs for durability and strength in cold climate conditions. The porous asphalt mixes consisted of a porous asphalt Superpave mix design method whereby the asphalt binder type was varied. Performance testing of the porous asphalt including draindown susceptibility, moisture-induced damage susceptibility, dynamic modulus, and permeability testing were completed. Based on the preliminary laboratory results, an optimal porous asphalt mix was recommended for use in a Canadian climate. Initial design guidelines for porous asphalt were provided based on preliminary findings and hydrological analysis.

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