Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 84-87).

M.S.

An inverted base pavement is a new pavement structure that consists of an unbound aggregate base between a stiff cement-treated foundation layer and a thin asphalt cover. Unlike conventional pavements which rely on upper stiff layers to bear and spread traffic loads, the unbound aggregate inter-layer in an inverted base pavement plays a major role in the mechanical response of the pavement structure. Traditional empirical pavement design methods rely on rules developed through long-term experience with conventional flexible or rigid pavement structures. The boundaries imposed on the unbound aggregate base in an inverted pavement structure change radically from those in conventional pavements. Therefore, current empirically derived design methods are unsuitable for the analysis of inverted base pavements. The present work documents a comprehensive experimental study on a full-scale inverted pavement test section built near LaGrange, Georgia. A detailed description of the mechanical behavior of the test section before, during and after construction provides critically needed understanding of the internal behavior and macro-scale performance of this pavement structure. Given the critical role of the unbound aggregate base and its proximity to the surface, a new field test was developed to characterize the stress-dependent stiffness of the as-built layer. A complementary numerical study that incorporates state-of-the-art concepts in constitutive modeling of unbound aggregates is used to analyze experimental results and to develop preliminary guidelines for inverted base pavement design. Simulation results show that an inverted pavement can deliver superior rutting resistance compared to a conventional flexible pavement structure with the same fatigue life. Furthermore, results show that an inverted base pavement structure can exceed the structural capacity of conventional flexible pavement designs for three typical road types both in rutting and fatigue while saving up to 40% of the initial construction costs.

Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, İnşaat Mühendisliği Anabilim Dalı, 2009. / Kaynakça var.

The current economic situation has severely affected the US road infrastructure and funding has become inadequate for either maintenance or future growth. The inverted base pavement structure is a promising alternative to achieve high quality roads at considerably lower cost than conventional pavements. The proximity of the unbound granular base layer to the tire load makes the response of the granular base critical to the performance of the pavement structure. Therefore extensive material characterization is conducted on the granular materials that make the base. In particular, a true triaxial chamber is developed to study the mechanical response and the stress-dependent stiffness of granular bases compacted at different water contents. A novel method is developed to assess the as-built stress-dependent anisotropic stiffness of granular bases in-situ using both crosshole and uphole test configurations. The two inverted base pavements built in Georgia at the Morgan County quarry haul road and the Lagrange south Loop are tested as part of this study. A nonlinear orthotropic constitutive model is selected to capture the deformational behavior of compacted granular bases. The response of the pavement is analyzed by implementing this constitutive behavior in a three-dimensional finite-element model. Different pavement structures are simulated. It is shown that thin asphalt concrete layers resting directly on granular bases deform as membranes. Finally, numerical simulations are extended to compare inverted base pavements to conventional pavements used in practice. Results highlight the inadequacy of ASSHTO’s structural layer coefficient for the analysis of inverted base pavement structures as well as the potential economic advantages of inverted base pavements.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Orientador: João Virgilio Merighi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-12T06:59:48Z (GMT). No. of bitstreams: 1 Silva_LuizAntonioda_M.pdf: 2904886 bytes, checksum: 2b2402e2537cbd9db0a35d64244be674 (MD5) Previous issue date: 2008 / Resumo: Este trabalho versa sobre métodos de levantamento de defeitos e avaliação das condições estruturais, funcionais e de segurança dos pavimentos asfálticos nas estradas estaduais sob a jurisdição do Departamento de Estradas de Rodagem do Estado de São Paulo - DER/SP. Aborda também alguns aspectos administrativos da Autarquia Estadual, aonde atuo como engenheiro de carreira na área de planejamento e de projeto. O DER/SP tem como missão administrar o sistema rodoviário estadual, sua integração com as rodovias municipais e federais e a sua interação com os demais modos de transporte, objetivando o atendimento aos usuários no transporte de pessoas e cargas. Para atender o crescimento acelerado da demanda de tráfego do Estado mais desenvolvido da Nação é imprescindível a ininterrupta execução de serviços de manutenção da rede existente e de construção de novas alternativas. Hoje com a relativa facilidade de acesso a uma ampla e variada tecnologia, aliada a uma crescente quantidade de boas empresas consultoras existentes no mercado, o DER/SP vem procurando desenvolver um Sistema de Gerência de Pavimentos (SGP-DER/SP). Enfim, o Estado de São Paulo que já teve no seu órgão rodoviário oficial a mais importante escola de rodoviarismo brasileira, está se adequando a um novo sistema de gestão para fazer jus à sua condição de principal Estado de um País de índole rodoviária. / Abstract: This master's thesis examines methods for survey and assessment of the structural, functional and safe conditions of asphalt pavements at the roads under the control of the Sao Paulo State Road Department (Departamento de Estradas de Rodagem do Estado de São Paulo - DER/SP). It also discusses some administrative aspects of the DER/SP, where I have worked as an engineer in the planning and project areas, which has the mission to manage the State road system, its integration with local and national roads and its interaction with other transport modes, aiming at providing transportation for people and cargo. In order to meet the fast growing traffic demand of the State of Sao Paulo, which is the most developed State of the country, it is vital to continuously keep the maintenance of the existing road net and the construction of new alternatives. Nowadays, with a relatively easy access to a wide range of technologies together with a growing supply of good consultancy companies, the DER/SP has attempted to develop a Pavements Management System (PMS-DER/SP). Therefore, the DER/SP, which once had been the most important brazilian road school, it has adapted itself to a new management system in order to be entitled to the position of the Road Department of the main State of the country, which is known for its road tradition. / Mestrado / Transportes / Mestre em Engenharia Civil

This research presents the results on an experimental investigation to identify the effect of polyphosphoric acid (PPA) on aging characteristics of an asphalt binder. Addition of PPA to asphalt binders is said to improve performance of flexible pavements. Asphalt binder PG 64-22 in modified and unmodified conditions was subjected to aging in the laboratory using a regular oven and also simulated short term aging using rolling thin film oven (RTFO) test. Aging experiments were conducted to analyze the extent of oxidation in terms of changes in molecular structure of the asphalt binder. These changes were appraised using Fourier transform infrared (FTIR) spectroscopy, dynamic shear rheometer (DSR), and epifluorescence microscopy tests. FTIR was used to determine the changes in major bands with addition of PPA. Stiffness and viscoelastic behaviors of asphalts were determined from the DSR test. The stiffness is measured by calculating the shear modulus, G* and the viscoelastic behavior is measured by calculating the phase angle, sin δ. Epifluorescence microscopy is a tool used to study properties of organic or inorganic substances. The morphological characteristics of PPA modified asphalt samples were observed through epifluorescence microscopy. Epifluorescence microscopy reveals the polymer phase distribution in the asphalt binders. Results of this investigation show PPA addition to asphalt binders improve G*/sin δ characteristics of asphalt binders. In addition, presence of PPA in polymer containing asphalt did not adversely affect aging of the binders.

M. Tech. (Civil Engineering, Faculty of Engineering and Technology), Vaal University of Technology) / Modified asphalt concrete is one of the important construction materials for flexible pavements. The addition of polymers and natural hydrocarbon modifiers to enhance the properties of asphalt concrete over a wide temperature range in paving applications has been the common practice. Currently these modified asphalt mixtures are relatively expensive. However, recycled polymers and rubber added to asphalt have also shown similar results in improving the performance of road pavements. In this study, an attempt has been made to use low density polyethylene (LDPE) obtained from plastic waste and crumb rubber obtained from worn out vehicle tyres. The aim was to optimise the proportions of LDPE in the bitumen binder using the ‘wet process’ and crumb rubber aggregates in the hot mix asphalt (HMA) using the ‘dry process’. The Marshall method of bituminous mix design was carried out for varying percentages of LDPE namely 2%, 4%, 6%, 8% and 10% by weight of bitumen binder and 1%, 2%, 3%, 4% and 5% crumb rubber by volume of the mineral aggregates. The characteristics of bitumen modified with LDPE were evaluated. The modified asphalt mix was also evaluated to determine the different mix characteristics. The results from laboratory studies in terms of the rheological properties of the LDPE modified bitumen binder showed an increase in viscosity, softening point and stiffness of the binder. The optimum Marshall stability values for HMA mixtures containing 2% crumb rubber tyre and 4% LDPE were found to be 30% higher than the conventional asphalt concrete mix. The wheel tracking test done at 50ºC was 9.81mm rut depth showing a good rutting resistance of the optimized mixture compared to the conventional asphalt mixes. The Modified Lottman test gave a Tensile Strength Ratio value of 0.979 which indicates a low degree of moisture susceptibility of the modified asphalt mix. The above results showed improved properties of the asphalt mixture. The economic assessment done using the present worth of costs indicated a reduction in maintenance cost due to the extended service life of the modified asphalt pavement.