Download or read book Performance of Unbound Aggregate Bases and Implications for Inverted Base Pavements written by Efthymios Papadopoulos and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Anisotropic Characterization and Performance Prediction of Chemically and Hydraulically Bounded Pavement Foundations written by Reza Salehi Ashtiani and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The aggregate base layer is a vital part of the flexible pavement system. Unlike rigid pavements, the base layer provides a substantial contribution to the load bearing capacity in flexible pavements, and this contribution is complex: stress dependent, moisture dependent, particle size dependent, and is anisotropic in nature. Furthermore, the response of the aggregate layer in the pavement structure is defined not only by resilient properties of the base layer but also by permanent deformation properties of the aggregate layer. Before the benefits of revolutionary changes in the typical pavement structures, such as deep unbound aggregate base (UAB) layers under thin hot mix asphalt surfaces and inverted pavement systems can be justified, an accurate assessment of the UAB is required. Several researchers identified that in order to properly assess the contribution of the UAB in the pavement structure, it is necessary to consider not only the vertical modulus but also the horizontal modulus as this substantially impacts the distribution of stresses within the pavement structure. Anisotropy, which is defined as the directional dependency of the material properties in unbound granular bases, is inherent even before the aggregate layer is subjected to traffic loads due to random arrangement of particles upon compaction. Distribution of particle contacts is dominated by the geometry of the aggregates as well as the compaction effort at the time of construction. Critical pavement responses and therefore performance of flexible pavements are significantly influenced by the level of anisotropy of aggregate layers. There are several ways to characterize the level of anisotropy in unbound aggregate systems. Previous research at Texas A & M University suggests functions of fitting parameters in material models (kvalues) as characterizers of the level of anisotropy. In the realm of geotechnical engineering, the ratio of the horizontal modulus to vertical modulus is commonly referred to as the level of anisotropy. When the vertical and horizontal moduli are equal, the system is isotropic, but when they differ, the system is anisotropic. This research showed that the level of anisotropy can vary considerably depending on aggregate mix properties such as gradation, saturation level, and the geometry of the aggregate particles. Cross anisotropic material properties for several unbound and stabilized aggregate systems were determined. A comprehensive aggregate database was developed to identify the contribution level of aggregate features to the directional dependency of material properties. Finally a new mechanistic performance protocol based on plasticity theory was developed to ensure the stability of the pavement foundations under traffic loads.

Download or read book Implication of Aggregates in the Design Construction and Performance of Flexible Pavements written by Hans G. Schreuders and published by ASTM International. This book was released on 1989 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Drainage in Unbound Aggregate Bases on Flexible Pavement Performance written by Mingjiang Tao and published by . This book was released on 2008 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study is to determine a proper/optimum gradation by conducting laboratory testing for unbound aggregates of Mexican limestone that are commonly used in Louisiana highways. However, there is trade-off between structural stability and permeability of unbound aggregates. The increase of permeability is often at the cost of structural stability or vice verse. Therefore, the criteria for selecting an optimum gradation are: (1) an adequate permeability to drain the infiltrated-water from the pavement as quickly as possible; and (2) a sufficient structural stability to support the traffic loading. The permeability of unbound aggregate is quantified by its saturated hydraulic conductivity while its structural stability is characterized by various laboratory tests on the strength, stiffness, and permanent deformation of the material. A series of laboratory tests, including constant-head permeability, California Bearing Ratio (CBR), Dynamic Cone Penetrometer (DCP), tube suction (TS), monotonic load traiaxial tests, and repeated load triaxial (RLT) tests, were conducted on Mexican limestone with different gradations. The gradations under investigation include coarse and fine branches of Louisiana class II gradation, New Jersey gradation medium, and an optimum gradation (fine and coarse branches).

Download or read book Significant Findings from Full scale Accelerated Pavement Testing written by Frederick Hugo and published by Transportation Research Board. This book was released on 2004 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 325: Significant Findings from Full-Scale Accelerated Pavement Testing documents and summarizes the findings from the various experimental activities associated with full-scale accelerated pavement testing programs.

Download or read book Effect of Large Size Aggregates on the Performance of Base Materials for Flexible Pavements written by Navneet Garg and published by . This book was released on 1993 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Practices for Unbound Aggregate Pavement Layers written by E. Tutumluer and published by . This book was released on 2013 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: "TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 445: Practices for Unbound Aggregate Pavement Layers consolidates information on the state-of-the-art and state-of-the-practice of designing and constructing unbound aggregate pavement layers. The report summarizes effective practices related to material selection, design, and construction of unbound aggregate layers to potentially improve pavement performance and longevity."--Publisher website.

Download or read book Targeting Aggregate Marginality from a Chemical and Materials Perspective to Improve Pavement Performance written by Ebrahim Sangsefidi and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unbound granular aggregates, due to a comparatively lower cost in comparison to bound pavement layers, are extensively used in the construction of road pavements. Thus, it is not surprising that a careful testing and selection of these materials is required to ensure a longlasting pavement life that avoids early and costly maintenance intervention. In order to appropriately evaluate the road aggregates, a series of standardised laboratory tests are undertaken to aid appropriate decision making prior to construction phases beginning. Generally, it is assumed if properly constructed, that the selection of aggregates based on these tests largely guarantees a satisfactory performance of them in the structure of pavements. Based on the results of a number of laboratory tests, aggregates have typically been categorized into two groups; premium and marginal. Where marginal aggregates are excluded from being used in high-trafficked pavement sections or State Highways in New Zealand. However, the depletion of high-quality aggregates, in conjunction with the significant cost of transport haul distance to site and its adverse environmental effects, has led road agencies in New Zealand to consider using locally available aggregates that have a more marginal quality. Due to their inherent mineralogical properties, marginal aggregates are usually more susceptible to adverse environmental conditions of the pavement structure. Therefore, their engineering characteristics can be progressively affected by the in-service weathering processes. Generally, because of the initial mechanical crushing, strong compaction, continuous in-service traffic loading, and direct interaction with the surrounding environment, the process of weathering can be significant in unbound aggregates. This topic is of even higher relevance for New Zealand, where there is a high demand for unbound aggregates and its young geologically sourced aggregates are generally more susceptible to the diverse environmental and climatic conditions. Although weathering processes may happen in a relatively short time and can cause ageing and deterioration of the structure of aggregates, a quantitative evaluation of its effect on road aggregates over the lifetime of the pavement is usually disregarded and properties of aggregates are assumed to be constant over time and location. In order to better understand the weathering process of aggregates and achieve a more efficient use of them this research develops a field and laboratory- based experimental methodology (as follows). Two sources of andesitic unbound aggregates are used in this study, one source of aggregates is characterised to be of high quality and the other of more marginal quality according to the local standard New Zealand Transport Agency (NZTA) M4 specification. - Field-based experiment: The chemical and physical degradation of road aggregates within quarries are considered as an observable analogue of in-situ weathering of aggregates in the pavement structure. A variety of analytical methods, including thin section petrography, X-Ray Fluorescence (XRF), and X-ray Diffraction (XRD) reveal the short-term (less than 15 years) in-situ weathering of aggregates. Overall, the immediate loss of bases and production of clay minerals are the notable trend of chemical weathering of selected aggregates. Moreover, thin-section analysis reveals changes in the textural features of aggregates during the weathering. - Lab-based experiment (loose aggregates): In order to make the current New Zealand standard Weathering Quality Index (WQI) testing a better representative of in-service condition of unbound aggregates a series of modifications are proposed to this testing methodology. These modifications include improved wetting and drying processes, varied characteristics of the weathering solution, and a testing of the wider gradation of aggregates. Compared to standard WQI test, the results show 200% and 70% increase in CI value and 130% and 230% increase in WCI results of produced fines in premium and marginal aggregates, respectively. Thus, it is believed that the modified WQI test method better represents the potential in-field pavement weathering of andesitic road aggregates.in harsh environmental conditions. - Lab-based experiment (loose aggregates): Water is usually known to be a key factor in the performance of the structural elements of road pavements. To gain more insight into the water-aggregate interactions of UGM, a testing methodology is devised to determine the real-time appetite of aggregates for water in various environmental conditions. It is concluded that the water absorption of road aggregates depends upon the temperature and composition of the solution. Due to the increase in the water temperature, 160% and 100% increase in the absorbed water is reported for premium and marginal aggregates, respectively. Furthermore, it is concluded that the standard water absorption testing methodology generally under-estimates the appetite of aggregates to absorb water. In extreme cases, the proposed testing methodology results in 130% higher water absorption compared to the standard test. - Lab-based experiment (compacted aggregates): The effect of Wetting and Drying (WD) cycles on the performance of compacted aggregates are investigated by conducting California Bearing Ratio (CBR) alongside Repeated Load Triaxial (RLT) tests. The results show that W-D can affect the properties of fines in the compacted specimens and controls the swelling behavior of marginal aggregates. W-D cycles result in approximately 40% increase in CI and WCI results of produced fines in both sources of aggregates. The W-D can also have an appreciable effect on the permanent deformation, resilient modulus and CBR values of specimens. 160% increase in permanent deformation is reported for soaked-conditioned premium aggregates, whereas marginal aggregates fail in the last stage of the loading. Overall, a thorough investigation of andesitic aggregate weatherability has been undertaken based upon the fundamental testing techniques required during the selection procedures of aggregates to ensure engineering life performance. This investigation includes an understanding of the ageing properties of the available aggregates and the local environmental condition where the aggregates are to be placed. This can be quite important for marginal aggregates, whose properties are usually more susceptible to environmental conditions. Furthermore, the Pass/fail criteria of the traditional testing methodologies do not adequately consider the durability of road aggregates in the construction, maintenance and environmental conditions that an aggregate is placed. It is believed that a grey-scale labelling (i.e. non-binary pass/fail status) of aggregates would be more effective in describing the materials' natural variability and statistical distribution to subsequently characterise an aggregates performance given the associated environmental and climatic conditions of the target location.

Download or read book Practices for Unbound Aggregate Pavement Layers written by E. Tutumluer and published by . This book was released on 2013 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: "TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 445: Practices for Unbound Aggregate Pavement Layers consolidates information on the state-of-the-art and state-of-the-practice of designing and constructing unbound aggregate pavement layers. The report summarizes effective practices related to material selection, design, and construction of unbound aggregate layers to potentially improve pavement performance and longevity."--Publisher website.

Download or read book Significant Findings from Full scale Accelerated Pavement Testing written by Wynand JvdM. Steyn and published by Transportation Research Board. This book was released on 2012 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: "TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 433: Significant Findings from Full-Scale Accelerated Pavement Testing documents and summarizes significant findings from the various experimental activities associated with full-scale accelerated pavement testing (f-sAPT) programs that have taken place between 2000 and 2011. The report also identifies gaps in knowledge related to f-sAPT and where future research may be needed. NCHRP Synthesis 433 is designed to expand the f-sAPT base of knowledge documented in NCHRP Syntheses 325 and 235, both with the same title of Significant Findings from Full-Scale Accelerated Pavement Testing. f-sAPT is the controlled application of a wheel loading, at or above the appropriate legal load limit, to a pavement system to determine pavement response in a compressed time period. The acceleration of damage is achieved by one or more of the following factors: increased repetitions, modified loading conditions, imposed climatic conditions, and thinner pavements with a decreased structural capacity which have shorter design lives"--

Download or read book Pavement Design and Materials written by A. T. Papagiannakis and published by John Wiley & Sons. This book was released on 2017-02-22 with total page 555 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive, state-of-the-art guide to pavement design and materials With innovations ranging from the advent of SuperpaveTM, the data generated by the Long Term Pavement Performance (LTPP) project, to the recent release of the Mechanistic-Empirical pavement design guide developed under NCHRP Study 1-37A, the field of pavement engineering is experiencing significant development. Pavement Design and Materials is a practical reference for both students and practicing engineers that explores all the aspects of pavement engineering, including materials, analysis, design, evaluation, and economic analysis. Historically, numerous techniques have been applied by a multitude of jurisdictions dealing with roadway pavements. This book focuses on the best-established, currently applicable techniques available. Pavement Design and Materials offers complete coverage of: The characterization of traffic input The characterization of pavement bases/subgrades and aggregates Asphalt binder and asphalt concrete characterization Portland cement and concrete characterization Analysis of flexible and rigid pavements Pavement evaluation Environmental effects on pavements The design of flexible and rigid pavements Pavement rehabilitation Economic analysis of alternative pavement designs The coverage is accompanied by suggestions for software for implementing various analytical techniques described in these chapters. These tools are easily accessible through the book’s companion Web site, which is constantly updated to ensure that the reader finds the most up-to-date software available.

Download or read book Interim Report on the Performance of the Lake County Inverted Flexible Pavement written by Robert P. Elliott and published by . This book was released on 1972 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book AASHTO Guide for Design of Pavement Structures 1993 written by American Association of State Highway and Transportation Officials and published by AASHTO. This book was released on 1993 with total page 622 pages. Available in PDF, EPUB and Kindle. Book excerpt: Design related project level pavement management - Economic evaluation of alternative pavement design strategies - Reliability / - Pavement design procedures for new construction or reconstruction : Design requirements - Highway pavement structural design - Low-volume road design / - Pavement design procedures for rehabilitation of existing pavements : Rehabilitation concepts - Guides for field data collection - Rehabilitation methods other than overlay - Rehabilitation methods with overlays / - Mechanistic-empirical design procedures.

Download or read book Transportation Research Record written by and published by . This book was released on 1974 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Highway Subdrainage Design written by Lyle K. Moulton and published by . This book was released on 1980 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Aggregates Handbook Second Edition written by National Stone, Sand & Gravel Association and published by . This book was released on 2013-03-20 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Pavement Engineering written by Rajib B. Mallick and published by CRC Press. This book was released on 2017-10-16 with total page 1013 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pavement Engineering will cover the entire range of pavement construction, from soil preparation to structural design and life-cycle costing and analysis. It will link the concepts of mix and structural design, while also placing emphasis on pavement evaluation and rehabilitation techniques. State-of-the-art content will introduce the latest concepts and techniques, including ground-penetrating radar and seismic testing. This new edition will be fully updated, and add a new chapter on systems approaches to pavement engineering, with an emphasis on sustainability, as well as all new downloadable models and simulations.