Development of the Loaded Wheel Tracking Test (LWT) for Evaluating Bleeding In Chip Seals and Relationship to Emulsion Residue Rheology
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State highway agencies (SHAs) lack sufficient to maintain the nation?s highway infrastructure. Most pavements have structural capacity, but lack serviceability functions as their surface characteristics have been lost with time. Pavement preservation surface treatments present SHAs with a cost-effective means of restoring surface characteristics and extending the service lives of structurally adequate pavement. Chip seals are one of the most commonly used cost-effective surface treatments in preventative and preservations maintenance programs. Compared to Hot Mix Asphalt (HMA) overlays, chip seals allow many kilometers of highways to be resurfaced with the same budget, and have many environmental and sustainability benefits in addition. Chip seals can extend pavement life up to 5 years depending on the quality of the materials, design and construction practice, climate, traffic and conditions of the existing pavements. One commonly distress leading to premature failure of chip seals is bleeding. Bleeding reduces the surface texture of the pavement, and hence compromises the safety of the traveling public especially during wet seasons, and intersections. However, although factors leading to premature bleeding are known, there are currently no laboratory test methods for evaluating bleedings in chip seals. The first objective of this thesis was to develop a laboratory testing procedure and analysis method for evaluating bleeding in chip seal using testing device of the loaded wheel test (LWT) specified in the American Society for Testing and Materials (ASMT D 6372). The second objective was to investigate the relationship between emulsion residue performance as measured by the ASTM D7405 ?Multiple Stress Creep and Recovery (MSCR)? test and chip seal bleeding resistance as measured by the LWT to evaluate the influence factors that related to bleeding performance to prevent bleeding in the field. The third objective was to quantify the benefits of emulsion modification to address bleeding resistance through comparison of emulsion residue and chip seal mixture samples prepared with conventional emulsions, and emulsions modified with SBS polymer and SBR Latex. A new sample preparation, testing and analysis procedure that allow for the effects of existing pavement substrate, traffic load, traffic volume, and temperature on bleeding to be evaluated using the LWT device was developed in this study. Specifically by introducing a system to control test temperature and application of image analysis to quantify changes in surface Results indicate that the modified LWT test method is capable of quantifying bleeding potential and bleeding development with loading cycles of laboratory prepared chip seal sample. Two response parameters of surface texture and image analysis were used as response parameters. Results showed emulsion application rate, aggregate gradation, and emulsion type to significant factors affecting bleeding of LWT evaluated samples. Also, there is moderate relationship between texture loss and % bleeding. The MSCR test was found to be a promising evaluation tool for emulsion residue performance properties as it proved capable of differentiating between emulsion chemistries and modification in terms of sensitivity to both temperature and stress. The result showed that modification could give the same creep compliance at higher temperature. The creep compliance, Jnr at 3.2kPa, %Recovery at 0.1kPa and %Recovery at 3.2 kPa obtained from the MSCR test results were found to be the significant factors affecting bleeding. In all, the LWT is shown to be the versatile equipment for testing the bleeding for chip seal and slurry seal. It recommended that a combinations different aggregate gradations, aggregate type, and emulsions type be evaluated, and the results be used to develop a standardized laboratory test for evaluating bleeding. Field results are also needed to help establish specification limits for the test.