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The main objective of this study was to develop a new test that would be simple to conduct and analyze for evaluating resistance of asphalt mixtures to fatigue cracking. For this purpose, a piece of equipment known as the Hamburg Wheel Tracking Test (HWTT) was used. HWTT has been widely accepted as a reasonable and reliable test to evaluate the rutting and moisture damage performance of asphalt mixtures but its use for evaluating fatigue resistance of asphalt mixtures is relatively a new concept. Its use as a fatigue test is advantages over current laboratory fatigue tests because of the possibility of considering various underlying support layers when the specimen is subjected to repeated loading. Ability to assess the asphalt mixture fatigue resistance in a layered system under repeated loading and in a laboratory environment provides the opportunity to integrate material design and pavement structural design for optimum performance. In addition, this test is practically feasible as a routine test method in terms of reliability, equipment availability, and data processing efficiency. The tests were conducted on a two-layer structure with the asphalt concrete slab as the top layer and the neoprene or an unbound aggregate base as the underlying layer. Based on the numerical analysis, a width of 6 inches was selected as the optimum width for this study. However, the experiment also included the 4-inch width for comparison. The thickness of the slab was selected at three levels: 1.0, 1.5, and 2.0 inches, with the 1.5-inch thickness being the main thickness applied to most of the slabs. In an asphalt pavement structure, the surface layer is often designed at a thickness of 1.5 to 2.0 inches. These tests were based on strain amplitude growth corresponding to three defined stages during the test (Early, Middle, Late). The impact of several factors on the test results was investigated. Those factors included the slab width and thickness, the underlying support type and condition, temperature of the test, the speed of tracking, and the type of asphalt mixture. The experiment showed that as the slab thickness become smaller, the strain amplitude and its corresponding growth rate become larger, exhibiting a relatively higher rate of fatigue damage. Using the unbound aggregate base proved to be challenging because of difficulty in achieving a smooth, even surface. A smooth surface was required to ensure proper bond of the gauges and collection of the data. Using synthetic rubber neoprene provided a smooth base and delivered a more reliable dataset compared to the aggregate base in this study. As expected, temperature played a significant role in the experiment, as a higher initial strain amplitude was observed at elevated temperatures. A higher strain and increased strain growth rate were observed at lower loading speeds. After determining the appropriate dimensions, temperature, and underlying support, tests were conducted on six different asphalt mixes. Strain development was monitored at the bottom of the slab for each mix. From the data collected, a new fatigue life model was developed to evaluate the fatigue performance of asphalt pavements when tested under the conditions explored in this research. The fatigue life in this model is defined as the number of HWTT load cycles at which the strain amplitude doubles, or equivalently, when the stiffness is reduced to half. This determination is made under the premise that the test operates in stress control mode. It was found that the rate of growth in strain amplitude during the test increased considerably when the binder content in the mix was decreased, validating the importance of ensuring adequate binder content in the asphalt mix. The SMA mixture demonstrated a higher rate of strain amplitude increase compared to the dense-graded mixtures. The mix with 35% RAP content and a PG 64-22 binder delivered lower growth in strain amplitude compared with other mixes. The IDEAL-CT test was also performed to draw comparisons. However, based on the outcomes, it showed no correlation with the results of the newly developed fatigue test. Based on the growth of strain amplitude throughout the test, a fatigue life model was developed. The fatigue life can be determined using this model, based on the number of cycles, with a criterion of either a 50% reduction in stiffness or a doubling of the strain amplitude. Finally, a numerical model was developed, and the observed strain response demonstrated that this model is capable of predicting both the type of response and the magnitude of strain amplitude with relative accuracy.
Recent research on asphalt binder aging and rejuvenatorsKey data on asphalt performance and formulationsUpdates on tests and specificationsFully-searchable text on CD-ROM (included) This series volume comprises research papers and technical reports developed within the U.S.-based Association of Asphalt Paving Technologists. The book is divided into sessions focused on technology, specifications, cold recycling of RAP, and rejuvenators, with special emphasis on aging and on how rejuvenators are modeled, formulated and used to improve asphalt binders and prevent cracking. The CD-ROM displays figures and illustrations in articles in full color along with a title screen and main menu screen. Each user can link to all papers from the Table of Contents and Author Index and also link to papers and front matter by using the global bookmarks which allow navigation of the entire CD-ROM from every article. Search features on the CD-ROM can be by full text including all key words, article title, author name, and session title. The CD-ROM has Autorun feature for Windows 2000 with Service Pack 4 or higher products along with the program for Adobe Acrobat Reader with Search 11.0. One year of technical support is included with your purchase of this product.
Fatigue Testing and Analysis of Results discusses fundamental concepts of fatigue testing and results analysis. The book begins with a description of the symbols and nomenclature selected for the present book, mainly those proposed by the ASTM Committee E-9 on Fatigue. Fatigue testing methods are then discussed including routine tests, short-life and long-life tests, cumulative-damage tests, and abbreviated and accelerated tests. Separate chapters cover fatigue testing machines and equipment; instruments and measuring devices; and test pieces used in fatigue testing. The factors affecting tes.
Explores whether combining the environmental conditioning system with the simple performance test would provide a superior procedure for determining the moisture susceptibility of hot-mix asphalt (HMA).
"TRB's National Cooperative Highway Research Program (NCHRP) Report 763: Evaluation of the Moisture Susceptibility of WMA Technologies presents proposed guidelines for identifying potential moisture susceptibility in warm mix asphalt (WMA). The report also suggests potential revisions to the Appendix to AASHTO R 35, "Special Mixture Design Considerations and Methods for WMA" as a means to implement the guidelines."--publisher's 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.
All of us are dependent on a built environment constructed and maintained by civil and hydraulic engineers, and for those working in these fields, keeping up to date with the latest technological developments is vital for the safe and efficient design and operation of this infrastructure. This book presents the proceedings of HCET 2023, the 8th International Technical Conference on Frontiers of Hydraulic and Civil Engineering Technology, held from 25-27 September 2023 in Wuhan, China. HCET is an international conference which aims to enhance the development of hydraulic and civil engineering in China, with a focus on high-end, intelligent and green technologies. It seeks to do this by consolidating global wisdom and achievements and providing scientific support. HCET also offers an excellent opportunity for scientists, researchers and engineers from around the world to exchange their findings and discuss developments, establishing a basis for national and international collaboration. A total of 316 contributions were received for the 2023 edition, of which 187 were ultimately accepted after a rigorous review process and checks for quality and plagiarism. Topics covered include the research and development of concrete structure design and analysis; structural mechanics and structural engineering; building and future materials; hydraulic engineering; geological exploration and earthquake engineering; building technology; urban planning; road, bridge and traffic engineering; energy infrastructure; environmental engineering and advanced engineering technologies, and interdisciplinary sciences and applications. Covering a wide range of subjects related to hydraulic engineering and civil engineering technology and associated transdisciplinary sciences, the book will be of interest to all those working in the field.