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.

This thesis presents a continuum model for asphalt concrete incorporating non- linear viscoelasticity, viscoplasticity, mechanically-induced damage and moisture- induced damage. The Schapery single-integral viscoelastic model describes the nonlinear viscoelastic response. The viscoplastic model of Perzyna models the time- dependent permanent deformations, using a Drucker-Prager yield surface which is modified to depend on the third deviatoric stress invariant to include more complex dependence on state of stress. Mechanically-induced damage is modeled using continuum damage mechanics, using the same modified Drucker-Prager law to determine damage onset and growth. A novel moisture damage model is proposed, modeling moisture-induced damage using continuum damage mechanics; adhesive moisture- induced damage to the asphalt mastic-aggregate bond and moisture-induced cohesive damage to the asphalt mastic itself are treated separately. The analytical model is implemented numerically for three-dimensional and plane strain finite element analyses, and a series of simulations is presented to show the performance of the model and its implementation. Sensitivity studies are conducted for all model parameters and results due to various simulations corresponding to laboratory tests are presented. In addition to the continuum model, results are presented for a micromechanical model using the nonlinear-viscoelastic-viscoplastic-damage model for asphalt mastic and a linear elastic model for aggregates. Initial results are encouraging, showing the strength and stiffness of the mix as well as the failure mode varying with moisture loading. These initial results are provided as a an example of the model's robustness and suitability for modeling asphalt concrete at the mix scale.

The focus of this dissertation is on constant displacment rate experiments on asphalt concrete and on developing continuum models in a general thermo-mechanical setting which will corroborate with the experimental results. Modeling asphalt concrete and predicting its response is of great importance to the pavement industry. More than 90 percent of the US Highways uses asphalt concrete as a pavement material. Asphalt concrete exhibits nonlinear response even at small strains and the response of asphalt concrete to different types of loading is quite different. The properties of asphalt concrete are highly influenced by the type and amount of the aggregates and the asphalt used. The internal structure of asphalt concrete keeps on evolving during the loading process. This is due to the influence of different kinds of activities at the microlevel and also due to the interaction with the environment. The properties of asphalt concrete depend on its internal structure. Hence we need to take the evolution of the internal structure in modeling the response of asphalt concrete. Experiments were carried out at different confinement pressures and displacement rates on cylindrical samples of asphalt concrete. Two different aggregates were used to make the sample -limestone and granite. The samples were tested at a constant displacement rate at a given confinement pressure. The force required to maintain this constant displacement rate is measured and recorded. The frame-work has been developed using the idea of multiple natural configurations that was introduced recently to study a variety of non-linear dissipative response of materials. By specifying the forms of the stored energy and rate of dissipation function of the material, specific models were developed using this frame work. In this work both a compressible and an incompressible model were developed by choosing appropriate forms of stored energy and rate of dissipation function. Finally the veracity of the models were tested by corroborating with the experimental results. It is anticipated that the present work will aid in the development of better constitutive equations which in turn will accurately model asphalt concrete in laboratory and in field.

This dissertation presents the development of an anisotropic viscoplastic continuum damage model to describe the permanent deformation of asphalt pavements. The model is developed to account for several phenomena that influence the permanent deformation of Asphalt Concrete (AC) at high temperatures. These phenomena include strain rate dependency, confining pressure dependency, dilation, aggregate friction, anisotropy, and damage. The model is based on Perzyna's theory of viscoplasticity with Drucker-Prager yield function modified to account for the microstructure anisotropy and damage. A parametric study was conducted to study the effect of key factors such as inherent anisotropy and damage on the model response. A preliminary investigation was conducted to demonstrate the capabilities of the model and its sensitivity to changes in the microstructure distribution and loading conditions. The model was used to describe laboratory experimental measurements obtained from the Federal Highway Administration (FHWA) Accelerated Loading Facility (ALF). The model had a good match with these experimental measurements. In particular, using the damage parameter, the model was able to capture the point at which AC experienced tertiary creep in a static creep test. A comprehensive experiment was conducted to systematically determine the model parameters and the evolution laws that describe AC hardening, anisotropy, and damage. The experiment consisted of a set of compressive triaxial strength tests conducted at three confining pressures and five strain rates. Based on these experimental measurements, the model was modified to include a nonassociated flow rule. The model was shown to capture the experimental measurements very well. Furthermore, an experiment was conducted to capture and characterize damage evolution in AC due to permanent deformation. AC specimens were loaded using a triaxial compression setup to four predefined strain levels at three confining pressures. X-Ray computed tomography and image analysis techniques were used to capture and characterize the evolution of cracks and air voids in the deformed specimens. Damage was found to be a localized phenomenon in the sense that there exists a critical section in an AC specimen that is mainly responsible for failure. The results of the damage experiment supported the damage evolution function proposed in the viscoplastic model.

This research paper covers the analysis of the main asphalt concrete production technological processes. It includes calculation of dosed materials for the asphalt concrete mix, as well as precision and stability of maintenance of temperature necessary for the technological process.

Thesis (M.S.) -- Mississippi State University. Department of Civil Engineering. / Title from title screen. Includes bibliographical references.

O crescente aumento do volume de tráfego, o excesso de cargas e a carência de manutenção têm contribuído cada vez mais para a degradação prematura dos pavimentos asfálticos. Na procura por materiais de elevado desempenho, uma alternativa que vem ganhando destaque é a incorporação de cal hidratada a concretos asfálticos. Nesta dissertação apresentam-se e analisam-se os resultados de uma investigação sobre a influência de dois tipos de cal (calcítica e dolomítica) em misturas asfálticas formuladas com ligante convencional e polimerizado. Os resultados demonstraram que a melhoria das propriedades de concretos asfálticos depende significativamente da qualidade da cal e do teor utilizado, sendo que não se observaram benefícios adicionais ao aumentar-se o teor de 1% para 2%. A cal calcítica mostrou-se mais eficiente na melhoria das propriedades das misturas asfálticas, proporcionando aumentos significativos de módulo de resiliência e resistência à tração. Além disso, nas misturas com cal ocorreram menores reduções de resistência e de módulo com a elevação da temperatura de ensaio e após processo de condicionamento para simular os efeitos deletérios da água e envelhecimento. De forma geral, a influência da cal foi mais efetiva em misturas com ligante convencional, onde sua incorporação promoveu comportamento semelhante, ou em alguns casos até superior, ao das misturas elaboradas com ligante modificado. Amostras sem cal acumularam deformações permanentes superiores no ensaio de creep dinâmico às registradas em amostras com cal hidratada, sem observarem-se comportamentos significativamente diferentes com ligantes convencional ou modificado. Ao analisar-se a influência de cal no envelhecimento de ligantes (RTFOT), observaram-se menores variações de viscosidade (menor enrijecimento) em amostras de ligante convencional com cal calcítica, seguindo tendência constatada em trabalhos internacionais, que relatam redução na taxa de envelhecimento em misturas asfálticas devido à incorporação de cal. A análise global dos resultados de ensaios realizados nesta pesquisa aponta que é possível produzir misturas asfálticas de elevado desempenho e durabilidade através da incorporação de cal hidratada, mas que a magnitude dos benefícios obtidos depende significativamente da qualidade da cal (porcentagem de óxido de cálcio) e do tipo de ligante utilizados em sua formulação. / The increasing growth of traffic volume and overloading and the lack of maintenance have growingly contributed for asphalt pavements early distress. In the search for high performance materials, the incorporation of hydrated lime to asphalt concretes has been gaining relevance. In this dissertation the results of a research on the influence of two kinds of lime (calcitic and dolomitic) in asphalt concretes (AC) with conventional and polymer binders are presented and analyzed. Laboratory tests results show that the improvement of AC properties highly depend on lime quality and content, no additional benefits being observed when lime content increases from 1% to 2%. Calcitic lime showed to be more efficient improving AC properties, especially regarding resilient modulus and split tensile strength, which significantly increased. Besides, adding lime made asphalt mixes strength and modulus less sensitive to temperature increase and also to hardening and to water deleterious effects. All in all, lime benefits were stronger when added to AC with conventional binder. In fact, asphalt mixtures with conventional binder and calcitic lime performed even better than mixtures with polymermodified binder. In dynamic creep tests, specimens of AC without lime accumulated higher permanent deformations than AC specimens with hydrated lime, regardless the type of binder. Regarding the influence of lime in binders aging (RTFOT), viscosity variations of lesser magnitude were observed in samples of conventional binder and calcitic lime, following the pattern described in international works, which report the decrease of aging rate of asphalt mixtures due to lime incorporation. Globally, tests results point out that asphalt mixtures with high modulus and resistance to permanent deformation may be obtained by adding hydrated lime. However, the extent of benefits highly depends on lime quality (calcium oxide content) and type of asphalt binder used.

abstract: The fatigue resistance of asphalt concrete (AC) plays an important role in the service life of a pavement. For predicting the fatigue life of AC, there are several existing empirical and mechanistic models. However, the assessment and quantification of the ‘reliability’ of the predictions from these models is a substantial knowledge gap. The importance of reliability in AC material performance predictions becomes all the more important in light of limited monetary and material resources. The goal of this dissertation research is to address these shortcomings by developing a framework for incorporating reliability into the prediction of mechanical models for AC and to improve the reliability of AC material performance prediction by using Fine Aggregate Matrix (FAM) phase data. The goal of the study is divided into four objectives; 1) development of a reliability framework for fatigue life prediction of AC materials using the simplified viscoelastic continuum damage (S-VECD) model, 2) development of test protocols for FAM in similar loading conditions as AC, 3) evaluation of the mechanical linkages between the AC and FAM mix through upscaling analysis, and 4) investigation of the hypothesis that the reliability of fatigue life prediction of AC can be improved with FAM data modeling. In this research effort, a reliability framework is developed using Monte Carlo simulation for predicting the fatigue life of AC material using the S-VECD model. The reliability analysis reveals that the fatigue life prediction is very sensitive to the uncertainty in the input variables. FAM testing in similar loading conditions as AC, and upscaling of AC modulus and damage response using FAM properties from a relatively simple homogenized continuum approach shows promising results. The FAM phase fatigue life prediction and upscaling of FAM results to AC show more reliable fatigue life prediction than the fatigue life prediction of AC material using its experimental data. To assess the sensitivity of fatigue life prediction model to uncertainty in the input variables, a parametric sensitivity study is conducted on the S-VECD model. Overall, the findings from this research show promising results both in terms of upscaling FAM to AC properties and the reliability of fatigue prediction in AC using experimental data on FAM. / Dissertation/Thesis / Doctoral Dissertation Civil and Environmental Engineering 2016

Made available in DSpace on 2014-12-17T15:03:18Z (GMT). No. of bitstreams: 1 CibeleGC.pdf: 1402838 bytes, checksum: db637069ba867fa96c00ae8cf6ff383c (MD5) Previous issue date: 2006-11-10 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The municipal district of Equador-RN is located in an area of great amounts of ores, being your main economical activity the extraction and the kaolin improvement. The main originating from environmental problem that activity is the amount of generated residue, about 70% of the extracted kaolin. The residues are simply piled up in lands of the improvement companies, occupying like this a large area and causing impact in the existent flora. When dry, the residues transform powdered and for the action of the wind, they disperse, polluting the air. Being like this, the present work has as objective evaluates the incorporation of the great residue, originating from of the kaolin improvement, in partial substitution of all the employed aggregates in a conventional mixture of asphalt concrete, which was used in the paving of BR101/RN061 - passage between Ponta Negra and Ares. That evaluation was accomplished in three stages. The first refers to the evaluation of the physical, thermal and mineralogical characteristics of the residue with the intention of to classify it and to define your application as aggregate (small and great). The second refers to the physical characterization of the aggregates and of the asphalt material used in the conventional mixture. And the third, to the evaluation of the mixtures containing residue, which were elaborated starting from the conventional mixture with the gradual incorporation of the residue, from 5 to 40%, in substitution to the part of the conventional aggregates, in way to obtain similar particle size curves the one of the conventional mixture. That evaluation was accomplished through the comparison between the volumetric composition, the mechanical behavior and the susceptibility to the humidity of the mixtures containing residue with the one of the conventional mixture, and with the one of the DNIT specifications. The results show that the great residue originating from of the kaolin improvement has grains of the most varied size, being like this, it can substitute part of all the conventional aggregates and of the filler in an asphalt mixture. Besides, your mineralogical composition presented the same present minerals in the composition of conventional aggregates used in paving. The results evaluation of the volumetric composition of the mixtures containing residue indicates that it can use up to 30% of residue in substitution to the conventional aggregates. The evaluation of the mechanical behavior of those mixtures indicates that the residue increment in the studied mixtures caused an increase of the stability and a reduction of the resistance to the traction. The values obtained in the resistance to the traction meet below the minimum value specified by DNIT, but close to the value obtained in the conventional mixture. When taking in consideration the susceptibility of the same ones to the humidity, the results indicate that she can use up to 25% of residue / O munic?pio de Equador-RN est? localizado numa regi?o de grandes quantidades de min?rios, sendo sua principal atividade econ?mica a extra??o e o beneficiamento de caulim. O principal problema ambiental proveniente dessa atividade ? a quantidade de res?duo gerado, cerca de 70% do caulim extra?do. Os res?duos s?o simplesmente amontoados em terrenos das empresas de beneficiamento, ocupando assim uma grande ?rea e causando impacto na flora existente. Quando secos, os res?duos transformam-se em p? e pela a??o do vento, se espalham, poluindo o ar. Sendo assim, o presente trabalho tem como objetivo avaliar a incorpora??o do res?duo grosso, oriundo do beneficiamento de caulim, em substitui??o parcial de todos os agregados empregados em uma mistura convencional de concreto asf?ltico, a qual foi utilizada na pavimenta??o da BR101/RN061 trecho entre Ponta Negra e Ares. Essa avalia??o foi realizada em tr?s etapas. A primeira refere-se ? avalia??o das caracter?sticas f?sicas, t?rmicas e mineral?gicas do res?duo com o intuito de classific?-lo e definir sua aplica??o como agregado (mi?do e gra?do). A segunda refere-se ? caracteriza??o f?sica dos agregados e do material asf?ltico utilizados na mistura convencional. E a terceira ? avalia??o das misturas contendo res?duo, as quais foram elaboradas a partir da mistura convencional com a incorpora??o gradativa do res?duo, de 5 a 40%, em substitui??o ? parte dos agregados convencionais, de forma a obter curvas granulom?tricas similares a da mistura convencional. Essa avalia??o foi realizada atrav?s da compara??o entre a composi??o volum?trica, o comportamento mec?nico e a suscetibilidade ? umidade das misturas contendo res?duo com os da mistura convencional, e com os das especifica??es exigidas pelo DNIT. Os resultados mostram que o res?duo grosso oriundo do beneficiamento de caulim possui gr?os dos mais variados di?metros, sendo assim, pode substituir parte de todos os agregados convencionais e do filler em uma mistura asf?ltica. Al?m disso, a sua composi??o mineral?gica apresentou os mesmos minerais presentes na composi??o de agregados convencionais utilizados em pavimenta??o. Os resultados da avalia??o da composi??o volum?trica das misturas contendo res?duo indicam que se pode empregar at? 30% de res?duo em substitui??o aos agregados convencionais. A avalia??o do comportamento mec?nico dessas misturas indicam que o incremento de res?duo nas misturas estudadas ocasionou um aumento da estabilidade e uma redu??o da resist?ncia ? tra??o. Os valores obtidos na resist?ncia ? tra??o se encontram abaixo do valor m?nimo especificado pelo DNIT, mas pr?ximos ao valor obtido na mistura convencional. Ao levar em considera??o a suscetibilidade das mesmas ? umidade, os resultados indicam que se pode empregar at? 25% de res?duo

O crescente aumento do volume de tráfego, o excesso de cargas e a carência de manutenção têm contribuído cada vez mais para a degradação prematura dos pavimentos asfálticos. Na procura por materiais de elevado desempenho, uma alternativa que vem ganhando destaque é a incorporação de cal hidratada a concretos asfálticos. Nesta dissertação apresentam-se e analisam-se os resultados de uma investigação sobre a influência de dois tipos de cal (calcítica e dolomítica) em misturas asfálticas formuladas com ligante convencional e polimerizado. Os resultados demonstraram que a melhoria das propriedades de concretos asfálticos depende significativamente da qualidade da cal e do teor utilizado, sendo que não se observaram benefícios adicionais ao aumentar-se o teor de 1% para 2%. A cal calcítica mostrou-se mais eficiente na melhoria das propriedades das misturas asfálticas, proporcionando aumentos significativos de módulo de resiliência e resistência à tração. Além disso, nas misturas com cal ocorreram menores reduções de resistência e de módulo com a elevação da temperatura de ensaio e após processo de condicionamento para simular os efeitos deletérios da água e envelhecimento. De forma geral, a influência da cal foi mais efetiva em misturas com ligante convencional, onde sua incorporação promoveu comportamento semelhante, ou em alguns casos até superior, ao das misturas elaboradas com ligante modificado. Amostras sem cal acumularam deformações permanentes superiores no ensaio de creep dinâmico às registradas em amostras com cal hidratada, sem observarem-se comportamentos significativamente diferentes com ligantes convencional ou modificado. Ao analisar-se a influência de cal no envelhecimento de ligantes (RTFOT), observaram-se menores variações de viscosidade (menor enrijecimento) em amostras de ligante convencional com cal calcítica, seguindo tendência constatada em trabalhos internacionais, que relatam redução na taxa de envelhecimento em misturas asfálticas devido à incorporação de cal. A análise global dos resultados de ensaios realizados nesta pesquisa aponta que é possível produzir misturas asfálticas de elevado desempenho e durabilidade através da incorporação de cal hidratada, mas que a magnitude dos benefícios obtidos depende significativamente da qualidade da cal (porcentagem de óxido de cálcio) e do tipo de ligante utilizados em sua formulação. / The increasing growth of traffic volume and overloading and the lack of maintenance have growingly contributed for asphalt pavements early distress. In the search for high performance materials, the incorporation of hydrated lime to asphalt concretes has been gaining relevance. In this dissertation the results of a research on the influence of two kinds of lime (calcitic and dolomitic) in asphalt concretes (AC) with conventional and polymer binders are presented and analyzed. Laboratory tests results show that the improvement of AC properties highly depend on lime quality and content, no additional benefits being observed when lime content increases from 1% to 2%. Calcitic lime showed to be more efficient improving AC properties, especially regarding resilient modulus and split tensile strength, which significantly increased. Besides, adding lime made asphalt mixes strength and modulus less sensitive to temperature increase and also to hardening and to water deleterious effects. All in all, lime benefits were stronger when added to AC with conventional binder. In fact, asphalt mixtures with conventional binder and calcitic lime performed even better than mixtures with polymermodified binder. In dynamic creep tests, specimens of AC without lime accumulated higher permanent deformations than AC specimens with hydrated lime, regardless the type of binder. Regarding the influence of lime in binders aging (RTFOT), viscosity variations of lesser magnitude were observed in samples of conventional binder and calcitic lime, following the pattern described in international works, which report the decrease of aging rate of asphalt mixtures due to lime incorporation. Globally, tests results point out that asphalt mixtures with high modulus and resistance to permanent deformation may be obtained by adding hydrated lime. However, the extent of benefits highly depends on lime quality (calcium oxide content) and type of asphalt binder used.