Ideally, asphalt pavements are designed to achieve sufficient stiffness prior to the application of traffic to resist rutting while also maintaining enough flexibility after years of service to minimize the amount of durability/brittleness related distresses (e.g. cracking and weathering). Multiple factors have caused an industry transition to mixes which are much more susceptible to crack, and durability related distresses are often the primary mechanism by which pavements fail. To restore a balance between rutting and durability distresses in asphalt pavements, the industry has started investigating balanced mix designs (BMDs). While mitigating only rutting or cracking behaviors is a straightforward exercise based on the collection of knowledge, simultaneously considering the two types of distresses is challenging considering that rutting is an early life distress and durability distresses are not typically observed until longer term aging has occurred. Mixture conditioning protocols to simulate field aging in conjunction with tests to fairly evaluate mixture integrity after conditioning are needed to scrutinize asphalt mixtures for durability related distresses during the mixture design phase. The current longer term conditioning protocol (R30) adopted by the American Association of State Highway and Transportation Officials (AASHTO) is not as severe as suggested when considering durability/brittleness (Isola et al. 2014; Yin et al. 2016; Cox et al. 2017). This dissertation’s primary objective is to provide guidance on asphalt mixture aging by contributing in four areas: 1) ensuring proper density measurement of field aged cores, 2) provide guidance on increased short term aging time effects in asphalt mixtures, 3) suggest improved mixture conditioning protocols to simulate longer term field aging, and 4) make suggestions for improving binder conditioning protocols to simulate longer term field aging. To these ends, a series of mixture and extracted binder tests were conducted on materials that were used to construct a full-scale test section in Columbus, MS that was monitored for aging for up to 5 after construction. The overall work presented provides simple recommendations or protocols which have the potential to improve the level of scrutiny that can be given to paving materials during the mix design phase and thus improve overall pavement performance.

Aggregate strength, gradation, and shape play a vital role in controlling asphalt mixture performance. Many studies have demonstrated the effects of these factors on asphalt mixture performance in terms of resistance to fatigue cracking and rutting. This study introduces numerical and analytical approaches supported with imaging techniques for studying the interrelated effects of aggregate strength, gradation, and shape on resistance of asphalt mixtures to fracture. The numerical approach relies on the discrete element method (DEM). The main advantage of this approach is the ability to account for the interaction between the internal structure distribution and aggregate properties in the analysis of asphalt mixture response and performance. The analytical approach combines aggregate strength variability and internal force distribution in an asphalt mixture to predict the probability of aggregate fracture. The numerical and analytical approaches were calibrated and verified using laboratory tests on various aggregate types and mixtures. Consequently these approaches were used to: (1) determine the resistance of various mixture types with different aggregate properties to fracture, (2) study the effects of aggregate strength variability on fracture, (3) quantify the influence of blending different types of aggregate on mixture strength, (4) develop a mathematical expression for calculating the probability of aggregate fracture within asphalt mixture, and (5) relate cracking patterns (cohesive: aggregate - aggregate and matrix - matrix, and adhesive: aggregate - matrix) in an asphalt mixture to internal structure distribution and aggregate properties. The results of this dissertation established numerical and analytical techniques that are useful for developing a virtual testing environment of asphalt mixtures. Such a virtual testing environment would be capable of relating the microscopic response of asphalt mixtures to the properties of the mixture constituents and internal structure distribution. The virtual testing environment would be an inexpensive mean to evaluate the influence of changing different material and design factors on the mixture response.

Aggregate strength, gradation, and shape play a vital role in controlling asphalt mixture performance. Many studies have demonstrated the effects of these factors on asphalt mixture performance in terms of resistance to fatigue cracking and rutting. This study introduces numerical and analytical approaches supported with imaging techniques for studying the interrelated effects of aggregate strength, gradation, and shape on resistance of asphalt mixtures to fracture. The numerical approach relies on the discrete element method (DEM). The main advantage of this approach is the ability to account for the interaction between the internal structure distribution and aggregate properties in the analysis of asphalt mixture response and performance. The analytical approach combines aggregate strength variability and internal force distribution in an asphalt mixture to predict the probability of aggregate fracture. The numerical and analytical approaches were calibrated and verified using laboratory tests on various aggregate types and mixtures. Consequently these approaches were used to: (1) determine the resistance of various mixture types with different aggregate properties to fracture, (2) study the effects of aggregate strength variability on fracture, (3) quantify the influence of blending different types of aggregate on mixture strength, (4) develop a mathematical expression for calculating the probability of aggregate fracture within asphalt mixture, and (5) relate cracking patterns (cohesive: aggregate - aggregate and matrix - matrix, and adhesive: aggregate - matrix) in an asphalt mixture to internal structure distribution and aggregate properties. The results of this dissertation established numerical and analytical techniques that are useful for developing a virtual testing environment of asphalt mixtures. Such a virtual testing environment would be capable of relating the microscopic response of asphalt mixtures to the properties of the mixture constituents and internal structure distribution. The virtual testing environment would be an inexpensive mean to evaluate the influence of changing different material and design factors on the mixture response.

Este trabalho apresenta os resultados alcançados em uma pesquisa experimental que objetivou estudar misturas asfálticas com módulos de resiliência elevados (EME), para emprego em camadas estruturais de pavimentos. As misturas EME são solução muito utilizada para pavimentos com elevado volume de tráfego, especialmente na França, por serem muito resistentes às deformações permanentes apresentando bom comportamento à fadiga. Foram caracterizados os ligantes asfálticos utilizados e as misturas projetadas. Para caracterização e verificação de desempenho, realizaram-se os ensaios da Metodologia Marshall, ensaios de resistência à tração, módulo de resiliência à compressão diâmetral, fadiga à tensão controlada, resistência ao dano por umidade induzida (Método Lottman Modificado), perda de massa por desgaste (Cântabro) e deformação permanente (creep dinâmico e simulador tipo LCPC). As misturas asfálticas projetadas apresentaram melhor desempenho mecânico em comparação com uma mistura de comparação formulada com ligante convencional (CAP 50/70). Foi construída uma pista experimental com o objetivo de verificar aspectos executivos e monitorar o desempenho da estrutura submetida a ensaios acelerados. Os danos causados pelas solicitações impostas pelo simulador de tráfego UFRGS-DAER/RS foram monitorados através de medidas de deflexões e afundamentos nas trilhas de roda e da inspeção visual para verificar a ocorrência de trincamento superficial. O carregamento aplicado superou os 200 mil ciclos, com cargas de eixo de 100 e 120 kN. O ATR médio observado no final do experimento totalizou 6 mm. Não foi observado trincamento na superfície do pavimento. A partir dos resultados obtidos é possível concluir que o emprego de misturas asfálticas de módulo elevado em camadas estruturais de pavimentos permitirá a construção de estruturas de melhor qualidade técnica, podendo contribuir para o aumento da vida útil das rodovias. / This work presents an experimental study that searched to study high modulus asphalt mixtures (EME) for structural layers of pavements. The EME is a well-known solution for high volume roads, especially in France, presenting better results in terms of rutting and fatigue cracking than conventional mixtures. Asphalt binders and designed mixtures were characterized. To evaluate the laboratorial mixes performance, Marshall Methodology, tensile strength, resilient modulus, fatigue (controlled stress mode), stripping (Modified Lottman test), weight loss (Cantabro Methodology) and permanent deformation (dynamic creep and LCPC simulator) were carried out. The results showed that the EME mixtures present better mechanical behavior than conventional asphalt mixture. An experimental section was built to verify the construction features and to monitor the progressive degradation produced by a linear traffic simulator. For the accompaniment of the degradation were monitored the pavement deflections, rutting and cracking. 200.000 load cycles were applied with axle loads of 100 and 120 kN.The rut depth in the end of experiment totalized 6 mm. Fatigue cracking was not observed in the pavement surface. The study results show that the use of EME mixtures in structural layers of pavements will allow the construction of structures with remarkably good technical quality, contributing to increase pavement life.

Este trabalho apresenta os resultados alcançados em uma pesquisa experimental que objetivou estudar misturas asfálticas com módulos de resiliência elevados (EME), para emprego em camadas estruturais de pavimentos. As misturas EME são solução muito utilizada para pavimentos com elevado volume de tráfego, especialmente na França, por serem muito resistentes às deformações permanentes apresentando bom comportamento à fadiga. Foram caracterizados os ligantes asfálticos utilizados e as misturas projetadas. Para caracterização e verificação de desempenho, realizaram-se os ensaios da Metodologia Marshall, ensaios de resistência à tração, módulo de resiliência à compressão diâmetral, fadiga à tensão controlada, resistência ao dano por umidade induzida (Método Lottman Modificado), perda de massa por desgaste (Cântabro) e deformação permanente (creep dinâmico e simulador tipo LCPC). As misturas asfálticas projetadas apresentaram melhor desempenho mecânico em comparação com uma mistura de comparação formulada com ligante convencional (CAP 50/70). Foi construída uma pista experimental com o objetivo de verificar aspectos executivos e monitorar o desempenho da estrutura submetida a ensaios acelerados. Os danos causados pelas solicitações impostas pelo simulador de tráfego UFRGS-DAER/RS foram monitorados através de medidas de deflexões e afundamentos nas trilhas de roda e da inspeção visual para verificar a ocorrência de trincamento superficial. O carregamento aplicado superou os 200 mil ciclos, com cargas de eixo de 100 e 120 kN. O ATR médio observado no final do experimento totalizou 6 mm. Não foi observado trincamento na superfície do pavimento. A partir dos resultados obtidos é possível concluir que o emprego de misturas asfálticas de módulo elevado em camadas estruturais de pavimentos permitirá a construção de estruturas de melhor qualidade técnica, podendo contribuir para o aumento da vida útil das rodovias. / This work presents an experimental study that searched to study high modulus asphalt mixtures (EME) for structural layers of pavements. The EME is a well-known solution for high volume roads, especially in France, presenting better results in terms of rutting and fatigue cracking than conventional mixtures. Asphalt binders and designed mixtures were characterized. To evaluate the laboratorial mixes performance, Marshall Methodology, tensile strength, resilient modulus, fatigue (controlled stress mode), stripping (Modified Lottman test), weight loss (Cantabro Methodology) and permanent deformation (dynamic creep and LCPC simulator) were carried out. The results showed that the EME mixtures present better mechanical behavior than conventional asphalt mixture. An experimental section was built to verify the construction features and to monitor the progressive degradation produced by a linear traffic simulator. For the accompaniment of the degradation were monitored the pavement deflections, rutting and cracking. 200.000 load cycles were applied with axle loads of 100 and 120 kN.The rut depth in the end of experiment totalized 6 mm. Fatigue cracking was not observed in the pavement surface. The study results show that the use of EME mixtures in structural layers of pavements will allow the construction of structures with remarkably good technical quality, contributing to increase pavement life.

Este trabalho apresenta os resultados alcançados em uma pesquisa experimental que objetivou estudar misturas asfálticas com módulos de resiliência elevados (EME), para emprego em camadas estruturais de pavimentos. As misturas EME são solução muito utilizada para pavimentos com elevado volume de tráfego, especialmente na França, por serem muito resistentes às deformações permanentes apresentando bom comportamento à fadiga. Foram caracterizados os ligantes asfálticos utilizados e as misturas projetadas. Para caracterização e verificação de desempenho, realizaram-se os ensaios da Metodologia Marshall, ensaios de resistência à tração, módulo de resiliência à compressão diâmetral, fadiga à tensão controlada, resistência ao dano por umidade induzida (Método Lottman Modificado), perda de massa por desgaste (Cântabro) e deformação permanente (creep dinâmico e simulador tipo LCPC). As misturas asfálticas projetadas apresentaram melhor desempenho mecânico em comparação com uma mistura de comparação formulada com ligante convencional (CAP 50/70). Foi construída uma pista experimental com o objetivo de verificar aspectos executivos e monitorar o desempenho da estrutura submetida a ensaios acelerados. Os danos causados pelas solicitações impostas pelo simulador de tráfego UFRGS-DAER/RS foram monitorados através de medidas de deflexões e afundamentos nas trilhas de roda e da inspeção visual para verificar a ocorrência de trincamento superficial. O carregamento aplicado superou os 200 mil ciclos, com cargas de eixo de 100 e 120 kN. O ATR médio observado no final do experimento totalizou 6 mm. Não foi observado trincamento na superfície do pavimento. A partir dos resultados obtidos é possível concluir que o emprego de misturas asfálticas de módulo elevado em camadas estruturais de pavimentos permitirá a construção de estruturas de melhor qualidade técnica, podendo contribuir para o aumento da vida útil das rodovias. / This work presents an experimental study that searched to study high modulus asphalt mixtures (EME) for structural layers of pavements. The EME is a well-known solution for high volume roads, especially in France, presenting better results in terms of rutting and fatigue cracking than conventional mixtures. Asphalt binders and designed mixtures were characterized. To evaluate the laboratorial mixes performance, Marshall Methodology, tensile strength, resilient modulus, fatigue (controlled stress mode), stripping (Modified Lottman test), weight loss (Cantabro Methodology) and permanent deformation (dynamic creep and LCPC simulator) were carried out. The results showed that the EME mixtures present better mechanical behavior than conventional asphalt mixture. An experimental section was built to verify the construction features and to monitor the progressive degradation produced by a linear traffic simulator. For the accompaniment of the degradation were monitored the pavement deflections, rutting and cracking. 200.000 load cycles were applied with axle loads of 100 and 120 kN.The rut depth in the end of experiment totalized 6 mm. Fatigue cracking was not observed in the pavement surface. The study results show that the use of EME mixtures in structural layers of pavements will allow the construction of structures with remarkably good technical quality, contributing to increase pavement life.

Doctor of Philosophy / Department of Civil Engineering / Stefan A. Romanoschi / Permanent deformation (rutting) is the most critical load-associated distress that develops on asphalt pavements significantly affecting their performance. Past research work focused on estimating permanent deformation of asphalt mixes using empirical prediction models or prediction models based on linear elastic material models. In recent years, mechanistic and mechanistic-empirical prediction models have been developed to take into account the behavior of asphalt material (viscoelastic, viscoplastic or elasto-visco-plastic). This research project aims to evaluate existing mechanistic models that predict permanent deformation (rutting) in asphalt mixes by comparing computed permanent deformation to that measured in a full-scale accelerated pavement test. Six pavement sections were constructed in the Civil Infrastructure Systems Laboratory (CISL) of Kansas State University with six different asphalt mixes. The sections were loaded with up to 700,000 load repetitions of a 22,000lb single axle. The transverse profiles at the pavement surface were measured periodically. For material characterization, asphalt mix samples fabricated in the laboratory, were subjected to dynamic modulus (|E*|), static creep - flow time (Ft), dynamic creep - flow number (Fn), triaxial and uniaxial strength tests, repetitive shear at constant height (RSCH) and frequency sweep at constant height (FSCH). The finite element software, Abaqus, was used to simulate and evaluate four permanent deformation prediction models, which are: creep model, elasto-visco-plastic model, viscoelastic model and Drucker-Prager model. The predicted permanent deformation was then compared to permanent deformation measured in CISL for the six of asphalt pavement sections. It was found that, with some improvements, creep and elasto-visco-plastic models could be used to predict permanent deformation in asphalt mixes. The viscoelastic model greatly under-predict permanent deformation, and the Drucker-Prager model with hardening criteria over predicts permanent deformation as compared to values measured in CISL.

Time- and rate-dependent materials such as polymers, bituminous materials, and soft materials clearly display all four fundamental responses (i.e. viscoelasticity, viscoplasticity, viscodamage, and healing) where contribution of each response strongly depends on the temperature and loading conditions. This study proposes a new general thermodynamic-based framework to specifically derive thermo-viscoelastic, thermo-viscoplastic, thermo-viscodamage, and micro-damage healing constitutive models for bituminous materials and asphalt mixes. The developed thermodynamic-based framework is general and can be applied for constitutive modeling of different materials such as bituminous materials, soft materials, polymers, and biomaterials. This framework is build on the basis of assuming a form for the Helmohelotz free energy function (i.e. knowing how the material stores energy) and a form for the rate of entropy production (i.e. knowing how the material dissipates energy). However, the focus in this work is placed on constitutive modeling of bituminous materials and asphalt mixes. A viscoplastic softening model is proposed to model the distinct viscoplastic softening response of asphalt mixes subjected to cyclic loading conditions. A systematic procedure for identification of the constitutive model parameters based on optimized experimental effort is proposed. It is shown that this procedure is simple and straightforward and yields unique values for the model material parameters. Subsequently, the proposed model is validated against an extensive experimental data including creep, creep-recovery, repeated creep-recovery, dynamic modulus, constant strain rate, cyclic stress controlled, and cyclic strain controlled tests in both tension and compression and over a wide range of temperatures, stress levels, strain rates, loading/unloading periods, loading frequencies, and confinement levels. It is shown that the model is capable of predicting time-, rate-, and temperature-dependent of asphalt mixes subjected to different loading conditions.

É apresentado um estudo sobre a influência da escolha dos parâmetros constitutivos no comportamento de misturas asfálticas, estudando o comportamento do material tanto no regime linear como o regime não-linear de deformações. Foram utilizados os dados experimentais da dissertação de Brito (2006), no qual realizou ensaios de compressão diametral medindo simultaneamente deslocamentos horizontais e verticais, além de que seus ensaios contemplavam corpos-de-prova variando o índice de vazios, crucial para as análises da presente tese. Comparou-se o comportamento das misturas de Brito extraindo-se delas as compliancias de cisalhamento J(t), de compressibilidade B(t) e a curva de fluência D(t) com coeficiente de Poisson assumido como constante. Os resultados das análises no regime linear mostraram que a consideração do coeficiente de Poisson implica alteração do comportamento do material em função do índice de vazios, resultando curvas de fluência diferentes na horizontal e vertical, não condizendo com a lógica de aumento da rigidez com a queda do índice de vazios. Provou-se também que o coeficiente de Poisson é totalmente incorreto para materiais viscoelásticos e assumi-lo como constante negligencia grau de viscoelasticidade do mesmo. Na análise não- linear, as principais conclusões foram que o uso do coeficiente de Poisson pode superestimar a rigidez do material quando este está em fluência não-linear, além de que independentemente do coeficiente de Poisson, o uso da Teoria de Potencial de Trabalho de Schapery não deve ser aplicado se considerada a fase de condicionamento nos dados do ensaio de fadiga, onde foi proposto um modelo para tal consideração que apresentou resultados de previsão satisfatórios frente aos resultados experimentais. Por fim, concluiu-se que o uso do coeficiente de Poisson em misturas asfálticas deve ser abandonado, recomendando-se o uso das compliancias J(t) e B(t), pois são parâmetros constitutivos fundamentais e sem as limitações impostas pelo coeficiente de Poisson. Além disto, recomenda-se cuidado no uso da Teoria do Potencial de Trabalho, não adaptada para a fase de condicionamento do material, recomendando-se uso de modelo auxiliar para, sugerindo-se assim o modelo deduzido nesta tese para uso conjunto com a Teoria do Potencial de Trabalho. / A study on the influence of the choice of constitutive parameters on the behavior of asphalt mixtures, studying the behavior of the material both in the linear and non-linear level of strains. The experimental data from the dissertation of Brito (2006) has been used, which performed indirect tensile tests measuring both horizontal and vertical displacements. The material tested by Brito has taken into account a reasonable range of air voids, which was crucial for the analysis of this thesis. The behavior of the mixes has been compared extracting from them the shear compliances J(t), compressibility B (t) and creep compliance D (t) with Poisson's ratio assumed as constant. The analysis results in the linear level of strains has shown that the consideration of Poisson's ratio implies change in material behavior in function of the air voids, resulting different creep compliances in the horizontal and vertical, not matching the logic increasing of stiffness with the decreasing of the air voids. It was also proved that the Poisson ratio is totally incorrect for viscoelastic materials and assume it as constant neglect of degree of viscoelasticity. In nonlinear analysis, the main conclusions were that the use of Poisson's ratio may overestimate the stiffness of the material when it is in nonlinear creep, despite the use of Poisson's ratio, the Schapery’s Work Potential Theory should not be applied if considered in the conditioning phase of the fatigue test data, where a model was proposed for such consideration and the results were satisfactory prediction compared to experimental results. Finally, it was concluded that the use of Poisson's ratio in asphalt mixtures must be abandoned, recommending the use of compliances J (t) and B (t), which are fundamental constitutive parameters without the constraints imposed by the Poisson’s ratio. Moreover, caution is advised in the use of the Schapery’s Work Potential Theory, not adapted to the conditioning phase of the material, recommending the use of auxiliary model, thus suggesting the model deduced in this thesis for use in conjunction with the Schapery’s Work Potential Theory.

É apresentado um estudo sobre a influência da escolha dos parâmetros constitutivos no comportamento de misturas asfálticas, estudando o comportamento do material tanto no regime linear como o regime não-linear de deformações. Foram utilizados os dados experimentais da dissertação de Brito (2006), no qual realizou ensaios de compressão diametral medindo simultaneamente deslocamentos horizontais e verticais, além de que seus ensaios contemplavam corpos-de-prova variando o índice de vazios, crucial para as análises da presente tese. Comparou-se o comportamento das misturas de Brito extraindo-se delas as compliancias de cisalhamento J(t), de compressibilidade B(t) e a curva de fluência D(t) com coeficiente de Poisson assumido como constante. Os resultados das análises no regime linear mostraram que a consideração do coeficiente de Poisson implica alteração do comportamento do material em função do índice de vazios, resultando curvas de fluência diferentes na horizontal e vertical, não condizendo com a lógica de aumento da rigidez com a queda do índice de vazios. Provou-se também que o coeficiente de Poisson é totalmente incorreto para materiais viscoelásticos e assumi-lo como constante negligencia grau de viscoelasticidade do mesmo. Na análise não- linear, as principais conclusões foram que o uso do coeficiente de Poisson pode superestimar a rigidez do material quando este está em fluência não-linear, além de que independentemente do coeficiente de Poisson, o uso da Teoria de Potencial de Trabalho de Schapery não deve ser aplicado se considerada a fase de condicionamento nos dados do ensaio de fadiga, onde foi proposto um modelo para tal consideração que apresentou resultados de previsão satisfatórios frente aos resultados experimentais. Por fim, concluiu-se que o uso do coeficiente de Poisson em misturas asfálticas deve ser abandonado, recomendando-se o uso das compliancias J(t) e B(t), pois são parâmetros constitutivos fundamentais e sem as limitações impostas pelo coeficiente de Poisson. Além disto, recomenda-se cuidado no uso da Teoria do Potencial de Trabalho, não adaptada para a fase de condicionamento do material, recomendando-se uso de modelo auxiliar para, sugerindo-se assim o modelo deduzido nesta tese para uso conjunto com a Teoria do Potencial de Trabalho. / A study on the influence of the choice of constitutive parameters on the behavior of asphalt mixtures, studying the behavior of the material both in the linear and non-linear level of strains. The experimental data from the dissertation of Brito (2006) has been used, which performed indirect tensile tests measuring both horizontal and vertical displacements. The material tested by Brito has taken into account a reasonable range of air voids, which was crucial for the analysis of this thesis. The behavior of the mixes has been compared extracting from them the shear compliances J(t), compressibility B (t) and creep compliance D (t) with Poisson's ratio assumed as constant. The analysis results in the linear level of strains has shown that the consideration of Poisson's ratio implies change in material behavior in function of the air voids, resulting different creep compliances in the horizontal and vertical, not matching the logic increasing of stiffness with the decreasing of the air voids. It was also proved that the Poisson ratio is totally incorrect for viscoelastic materials and assume it as constant neglect of degree of viscoelasticity. In nonlinear analysis, the main conclusions were that the use of Poisson's ratio may overestimate the stiffness of the material when it is in nonlinear creep, despite the use of Poisson's ratio, the Schapery’s Work Potential Theory should not be applied if considered in the conditioning phase of the fatigue test data, where a model was proposed for such consideration and the results were satisfactory prediction compared to experimental results. Finally, it was concluded that the use of Poisson's ratio in asphalt mixtures must be abandoned, recommending the use of compliances J (t) and B (t), which are fundamental constitutive parameters without the constraints imposed by the Poisson’s ratio. Moreover, caution is advised in the use of the Schapery’s Work Potential Theory, not adapted to the conditioning phase of the material, recommending the use of auxiliary model, thus suggesting the model deduced in this thesis for use in conjunction with the Schapery’s Work Potential Theory.