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Author: Publisher: ISBN: Category : Asphalt Languages : en Pages : 62
Book Description
This project reviewed existing laboratory methods for accurately describing the constitutive behavior of the mixes used in the Commonwealth of Virginia. Indirect tensile (IDT) strength, resilient modulus, static creep in the IDT and uniaxial modes, flexural beam fatigue, and dynamic modulus tests were conducted on two typical mixes used in Virginia: SM-9.5A (surface mix) and BM-25.0 (base mix). The tests conducted produced a wealth of data on typical values for the properties of the two mixes studied over a wide range of temperatures and loading frequencies. The results suggest that the IDT strength test is an effective test to characterize the tensile strength of hot-mix asphalt (HMA), especially for thermal cracking evaluation. The resilient modulus test and the static creep test in the IDT setup are practical and simple to perform, but the analysis of the measurements is complicated, and the variability of the results is high. The compressive uniaxial dynamic modulus and the uniaxial static creep tests were found to be simple to conduct and to analyze because of the homogeneous state of stress in the specimen during testing. The flexural fatigue test was time consuming, but the test produces valuable information about the fatigue properties of hot-mix asphalt. The investigation also found good correlations among the IDT strength, resilient modulus, and dynamic modulus results. A variety of tests is recommended for characterizing the mechanistic-empirical pavement analysis and design. These tests would provide the properties needed to characterize the asphalt layers for the pavement analysis and design. The recommended tests are as follows: IDT strength for characterizing HMA susceptibility to thermal cracking, dynamic modulus for characterization of the constitutive behavior of the HMA, uniaxial creep for characterizing permanent deformation characteristics, and flexural fatigue tests to characterize fatigue properties. Materials characterization testing can be a valuable tool in pavement design. The use of mechanistic-empirical modeling can be used to predict the performance of a pavement. With this type of testing and modeling, the materials used in pavements will be of better quality and more resistant to environmental and structural deterioration. A more durable pavement will aid in reducing the frequency and costs associated with maintenance.
Author: Publisher: ISBN: Category : Asphalt Languages : en Pages : 62
Book Description
This project reviewed existing laboratory methods for accurately describing the constitutive behavior of the mixes used in the Commonwealth of Virginia. Indirect tensile (IDT) strength, resilient modulus, static creep in the IDT and uniaxial modes, flexural beam fatigue, and dynamic modulus tests were conducted on two typical mixes used in Virginia: SM-9.5A (surface mix) and BM-25.0 (base mix). The tests conducted produced a wealth of data on typical values for the properties of the two mixes studied over a wide range of temperatures and loading frequencies. The results suggest that the IDT strength test is an effective test to characterize the tensile strength of hot-mix asphalt (HMA), especially for thermal cracking evaluation. The resilient modulus test and the static creep test in the IDT setup are practical and simple to perform, but the analysis of the measurements is complicated, and the variability of the results is high. The compressive uniaxial dynamic modulus and the uniaxial static creep tests were found to be simple to conduct and to analyze because of the homogeneous state of stress in the specimen during testing. The flexural fatigue test was time consuming, but the test produces valuable information about the fatigue properties of hot-mix asphalt. The investigation also found good correlations among the IDT strength, resilient modulus, and dynamic modulus results. A variety of tests is recommended for characterizing the mechanistic-empirical pavement analysis and design. These tests would provide the properties needed to characterize the asphalt layers for the pavement analysis and design. The recommended tests are as follows: IDT strength for characterizing HMA susceptibility to thermal cracking, dynamic modulus for characterization of the constitutive behavior of the HMA, uniaxial creep for characterizing permanent deformation characteristics, and flexural fatigue tests to characterize fatigue properties. Materials characterization testing can be a valuable tool in pavement design. The use of mechanistic-empirical modeling can be used to predict the performance of a pavement. With this type of testing and modeling, the materials used in pavements will be of better quality and more resistant to environmental and structural deterioration. A more durable pavement will aid in reducing the frequency and costs associated with maintenance.
Author: Douglas M. Marshall Publisher: CRC Press ISBN: 113802693X Category : Political Science Languages : en Pages : 1944
Book Description
The proliferation of technological capability, miniaturization, and demand for aerial intelligence is pushing unmanned aerial systems (UAS) into the realm of a multi-billion dollar industry. This book surveys the UAS landscape from history to future applications. It discusses commercial applications, integration into the national airspace system (NAS), System function, operational procedures, safety concerns, and a host of other relevant topics. The book is dynamic and well-illustrated with separate sections for terminology and web- based resources for further information.
Author: Vittorio Guglielmetti Publisher: CRC Press ISBN: 0415558549 Category : Technology & Engineering Languages : en Pages : 1336
Book Description
The design and construction of “long and deep” tunnels, i.e. tunnels under mountains, characterised by either considerable length and/or overburden, represent a considerable challenge. The scope of this book is not to instruct how to design and construct such tunnels but to share a method to identify the potential hazards related to the process of designing and constructing long and deep tunnels, to produce a relevant comprehensive analysis and listing, to quantify the probability and consequences, and to design proper mitigation measures and countermeasures. The design, developed using probabilistic methods, is verified during execution by means of the so called Plan for Advance of the Tunnel (PAT) method, which allows adapting the design and control parameters of the future stretches of the tunnel to the results of the stretches already finished, using the monitoring data base. Numerous criteria are given to identify the key parameters, necessary for the PAT procedure. Best practices of excavation management with the help of real time monitoring and control are also provided. Furthermore cost and time evaluation systems are analysed. Finally, contractual aspects related to construction by contract are investigated, for best development and application of models more appropriate for tunnelling-construction contracts. The work will be of interest to practising engineers, designers, consultants and students in mining, underground, tunnelling, transportation and construction engineering, as well as to foundation and geological engineers, urban planners/developers and architects.
Author: Amara Loulizi Publisher: ISBN: Category : Pavements, Asphalt Languages : en Pages : 32
Book Description
This project evaluated the procedures proposed by the Mechanistic-Empirical Pavement Design Guide (MEPDG) to characterize existing hot-mix asphalt (HMA) layers for rehabilitation purposes. Thirty-three cores were extracted from nine sites in Virginia to measure their dynamic moduli in the lab. Falling-weight deflectometer (FWD) testing was performed at the sites because the backcalculated moduli are needed for the Level 1 procedure. The resilient modulus was also measured in the lab because it is needed for the Level 2 procedure. A visual pavement rating was performed based on pavement condition because it is needed for the Level 3 procedure. The selected cores were tested for their bulk densities (Gmb) using the AASHTO T166 procedure and then for their dynamic modulus in accordance with the AASHTO TP62-03 standard test method. Then the cores were broken down and tested for their maximum theoretical specific gravity (Gmm) using the AASHTO T-209 procedure. Finally an ignition test was performed to find the percentage of binder and to reclaim the aggregate for gradation analysis. Volumetric properties were then calculated and used as input for the Witczak dynamic modulus prediction equations to find what the MEPDG calls the undamaged master curve of the HMA layer. The FWD data, resilient modulus data, and pavement rating were used to find the damaged master curve of the HMA layer as suggested for input Levels 1, 2, and 3, respectively. It was found that the resilient modulus data needed for a Level 2 type of analysis do not represent the entire HMA layer thickness, and therefore it was recommended that this analysis should not be performed by VDOT when implementing the design guide. The use of Level 1 data is recommended because FWD testing appears to be the only procedure investigated that can measure the overall condition of the entire HMA layer.
Author: Stacey D. Diefenderfer Publisher: ISBN: Category : Pavements, Asphalt Languages : en Pages : 44
Book Description
Several processes have been developed to reduce the mixing and compaction temperatures of hot mix asphalt (HMA) without sacrificing the quality of the resulting pavement. The purpose of this study was to evaluate the installation of warm mix asphalt (WMA) to compile experiences and offer recommendations for future use. Three trial sections were installed using warm mix technologies between August and November of 2006. Two used the Sasobit technology, and the third employed the Evotherm technology. This report discusses the material makeup of these technologies and documents the production and placement of the three trial sections. The results of this study and further studies can serve as a basis for decision making by the Virginia Department of Transportation (VDOT) regarding the use of WMA technology. Trial sections were initiated through cooperative efforts by the Virginia Transportation Research Council; VDOT districts, residencies, and area headquarters; and participating contractors. Construction used typical mixture designs and practices so that performance under typical construction conditions could be evaluated. General experiences and processes used during construction were documented, and samples were taken for laboratory characterization. Density measurements and cores were taken at each site to determine the initial pavement properties. At the Evotherm installation, asphalt fume sampling was conducted by VDOT's Employee Safety & Health Division to evaluate differences in worker exposure between HMA and WMA pavement laydown operations. The study showed that WMA can be successfully placed using conventional HMA paving practices and procedures with only minor modifications to account for the reduction in temperature. The evaluated technologies affected mixture properties in slightly different ways such as changes in tensile strength ratios and variability in air voids. Additional monitoring of constructed sections was recommended to evaluate long-term performance. Inclusion of WMA technology as an option for paving operations provides potential benefits to VDOT and the contracting community. Theoretically, these technologies could extend the asphalt paving season into cooler weather, allowing for better optimization of paving resources. The technologies also allow the construction of asphalt pavements at lower temperatures, resulting in reduced cooling time before the pavement is opened to traffic. Lower production temperatures may also increase mixture durability by reducing production aging of the mix. Benefits to contractors may include the ability to increase hauling distances between the plant and project, reduced plant emissions resulting in improved air quality, and cost savings because of reduced energy costs. Because of the experimental nature of this study, no cost savings data are yet available to justify or refute the use of WMA technologies.
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Author: Louay Nadhim Mohammad
Author: Douglas M. Marshall
Author: Vittorio Guglielmetti
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Author: Amara Loulizi
Author: Isaac Lem Howard
Author: Rouzbeh Ghabchi
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Author: Stacey D. Diefenderfer