Asphalt overlay has been widely used in the United States as a cost-effective maintenance approach to keep the pavement in a satisfactory condition. In recent years, many studies have been conducted to investigate the overlay asphalt mix design, overlay pavement design, and quality control/quality assurance for the asphalt overlay pavement. In Texas, thin overlays (lift thickness less than 2 in.) and ultra-thin overlays (lift thickness of 0.5 in. to 0.75 in.) seem to be more beneficial than conventional asphalt overlays. For this type of overlay, the bonding condition between the overlay and existing AC layer is crucial for the pavement to exhibit a long-lasting performance. However, the importance of tack coat to the performance of thin overlays is still not emphasized. Each state highway agency has its own selection procedure for determining which tack coat material is appropriate for a specific area. The related standard and specifications for quality control of tack coat is still under development. Therefore, there is a need to understand fully the performance of different tack coat materials.
This study was trying to make an effort to answer some of these questions. There are three parts in this research including the laboratory study with tack coat materials, the numerical modeling of overlay pavement in consideration of bonding condition, and LTPP case study on evaluation of performance of asphalt overlay pavement in Texas.
The results of laboratory study indicated that the modified direct shear test could be applied to differentiate the quality of different tack coat materials. The new product of tack coat, such as Trackless and Ultrafuse, exhibit greater shear strength than conventional tack coat. The Christensen-Anderson-Marasteanu (CAM) model is also suitable to characterize the dynamic modulus of tack coat material. The Multiple Stress Creep Recovery (MSCR) test results indicated that all the investigated tack coat materials have low rutting susceptibility. The low temperature property of tack coat material should be addressed in the standard to achieve a material with a balanced performance.
ABAQUS was used to simulate the asphalt overlay pavement’s response under static traffic load. The results indicated that a good bonding condition between the asphalt overlay layer and existing AC layer is crucial to asphalt overlay pavement’s integrated performance.
The LTPP case study results indicated that the calculated life gain of these experimental sections was not consistent with the life gain based on the Pavement Condition Rating (PCR) curves. There is a rough trend that the service life of the overlay pavement has a reverse relationship with the annual traffic volume. The field performance of overlays is affected by many factors, such as the climate, the over-loading vehicles, and the accuracy of pavement condition survey. These factors were not investigated at the time of writing this report.
This study proved that a good quality of asphalt overlay pavement’s interface is important to the pavement for retaining a long-term satisfactory performance. More in-depth research is needed in the future.
|Commitee:||Carrasco, Cesar, Tirado, Cesar, Taboada Jimenez, Heidi|
|School:||The University of Texas at El Paso|
|School Location:||United States -- Texas|
|Source:||DAI-B 81/12(E), Dissertation Abstracts International|
|Subjects:||Civil engineering, Materials science|
|Keywords:||ABAQUS, LTPP data base, Modified direct-shear test, Pavement condition rating, Tack coat, Thin overlay|
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