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The fatigue life of an asphalt pavement is directly related to various factors of a typical warm mix asphalt (WMA) mixture. Improving the understanding of the fatigue behavior of the rubberized WMA mixtures is helpful in recycling the scrap tires and saving energy. This study explores the utilization of the conventional fatigue analysis approach in investigating the cumulative dissipated energy, stiffness, and fatigue life of rubberized asphalt concrete mixtures containing WMA additives. The fatigue beams were made with one rubber type (-40 mesh ambient crumb rubber), two aggregate sources, two WMA additives (Asphamin and Sasobit), and tested at 5°C. The test results indicated that the addition of crumb rubber and WMA additive not only reduced the mixing and compaction temperatures of rubberized asphalt mixtures offset by crumb rubber but also slightly extended the long-term performance of pavement when compared with conventional asphalt mixtures.
In the recent past, new materials, laboratory and in-situ testing methods and construction techniques have been introduced. In addition, modern computational techniques such as the finite element method enable the utilization of sophisticated constitutive models for realistic model-based predictions of the response of pavements. The 7th RILEM International Conference on Cracking of Pavements provided an international forum for the exchange of ideas, information and knowledge amongst experts involved in computational analysis, material production, experimental characterization, design and construction of pavements. All submitted contributions were subjected to an exhaustive refereed peer review procedure by the Scientific Committee, the Editors and a large group of international experts in the topic. On the basis of their recommendations, 129 contributions which best suited the goals and the objectives of the Conference were chosen for presentation and inclusion in the Proceedings. The strong message that emanates from the accepted contributions is that, by accounting for the idiosyncrasies of the response of pavement engineering materials, modern sophisticated constitutive models in combination with new experimental material characterization and construction techniques provide a powerful arsenal for understanding and designing against the mechanisms and the processes causing cracking and pavement response deterioration. As such they enable the adoption of truly "mechanistic" design methodologies. The papers represent the following topics: Laboratory evaluation of asphalt concrete cracking potential; Pavement cracking detection; Field investigation of pavement cracking; Pavement cracking modeling response, crack analysis and damage prediction; Performance of concrete pavements and white toppings; Fatigue cracking and damage characterization of asphalt concrete; Evaluation of the effectiveness of asphalt concrete modification; Crack growth parameters and mechanisms; Evaluation, quantification and modeling of asphalt healing properties; Reinforcement and interlayer systems for crack mitigation; Thermal and low temperature cracking of pavements; and Cracking propensity of WMA and recycled asphalts.
Integration of theoretical developments offers complete description of linear theory of viscoelastic behavior of materials, with theoretical formulations derived from continuum mechanics viewpoint and discussions of problem solving. 1982 edition.
Introduction and Research Approach -- Findings -- Interpretation, Appraisal, and Applications -- Conclusions and Recommendations -- References -- Appendixes.
Low temperature cracking is a major distress for flexible pavements in cold regions. Most tests that are used currently to predict asphalt mixture performance at low temperatures require long time and effort to perform the test and analyze the data. A new laboratory test called the Ohio CTE device (OCD) has been developed as a more practical alternative to predict the asphalt mixture performance at low temperatures. This study presents an evaluation of the Ohio CTE device (OCD) in terms of effort for sample preparation, testing time, repeatability of test results, and complexity of the analysis of test data. To assess the ability of the Ohio CTE device (OCD) to predict the low temperature performance of asphalt mixtures, results obtained from this test were correlated to three other common low temperature tests, including the creep compliance and indirect tension test (IDT), the thermal stress restrained specimen test (TSRST), the asphalt concrete cracking device test (ACCD). Nine asphalt mixtures prepared using the same aggregate blend and different asphalt binders were included in this study. High correlation was observed between the Ohio CTE device (OCD) test results and results obtained from the other laboratory tests. In addition, the Ohio CTE device (OCD) was found to be advantageous over the other low temperature tests in that it requires significantly less time to prepare the test samples, which suggests that the Ohio CTE device (OCD) can be used as a routine test for low temperature characterization of asphalt mixtures.
This report examines the feasibility of using the thermal stress restrained specimen test to evaluate low temperature cracking in asphalt pavement mixes. Data were collected from laboratory and field evaluations. Various mixing, aging, and compaction methods were used to prepare test samples with materials obtained from two Wyoming Department of Transportation (WYDOT) highway projects. Field data were obtained from two recently built test sections and compared with laboratory test results. Pavement condition surveys quantified low temperature cracking of both test sections after one winter. Temperature data for the project sites also were collected. Pavement condition and temperature data were compared to results from the thermal stress restrained specimen test. The thermal stress restrained specimen test was effective in testing asphalt pavement mixes. However, test results indicated that lab prepared samples did not closely simulate field samples. Also, comparisons of lab results with field conditions were performed. However, it is recommended that a more comprehensive analysis be performed after test sections have been in service for a few years.
This report develops procedures and associated criteria for laboratory conditioning of asphalt mixtures to simulate short-term aging. The report presents proposed changes to the American Association of State Highway and Transportation Officials (AASHTO) R 30, Mixture Conditioning of Hot-Mix Asphalt (HMA), and a proposed AASHTO practice for conducting plant aging studies. The report will be of immediate interest to materials engineers in state highway agencies and the construction industry with responsibility for design and production of hot and warm mix asphalt.
A study was performed to determine the influence of material properties on the thermal cracking performance of hot mix asphalt (HMA), and to determine the ability to predict thermal cracking from pavements of known field performance. The testing device used to measure the HMA properties was the thermal-stress, restrained-specimen test (TSRST), and the device used to measure the binder properties was the bending beam rheometer (BBR). The laboratory study was conducted to determine the variability of test results as an influence of 1) asphalt cement stiffness, 2) asphalt cement quantity, 3) mixes with various aggregate qualities, 4) aging, and 5) the presence of hydrated lime. The influence of the asphalt cement stiffness was the single largest factor that controlled the test results.
This report describes the thermal stress restrained specimen test (TSRST), which was selected to evaluate the low-temperature cracking resistance of asphalt concrete mixtures. The TSRST system includes a load frame, step-motor-driven load ram, data acquisition hardware and software, temperature controller, and specimen alignment stand. An experiment design that considered a range of mixture and test condition variables was developed to evaluate the suitability of TSRST for characterizing low-temperature cracking resistance of asphalt concrete mixtures. Four asphalts and two aggregates were selected for the experiment. The mixture variables included asphalt type, aggregate type, and air voids content; the test condition variables included specimen size, stress relaxation, aging, and cooling rate.