A dry porous road surface may need a higher quantity of emulsion. The texture and condition of the existing road surface will affect the aggregate if needed, quantity and spray rate. If an aggregate is needed to inhance surface friction then a sharp clean sand would be required. The type and quantity of traffic will have a large effect on the amount of asphalt emulsion to be used as well as the emulsion type. If these factors are addressed the chances of a good fog seal being placed are greatly increased. The following factors can have a tremendous effect on the performance of a fog seal traffic, aggregate shape, existing surface and residual asphalt content. When designing a fog seal a number of factors have to be examined and assessed to ensure a proper surface will be placed that will perform for its service life. This type of maintenance treatment is primarily employed as an impervious sealer that will slow the rate of weathering of the asphalt in the underlying pavement. More in-depth research is needed in the future.A fog seal is a light application of asphalt emulsion to an existing paved asphalt surface. 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. These factors were not investigated at the time of writing this report. 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. There is a rough trend that the service life of the overlay pavement has a reverse relationship with the annual traffic volume. 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. 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 low temperature property of tack coat material should be addressed in the standard to achieve a material with a balanced performance.ĪBAQUS was used to simulate the asphalt overlay pavement's response under static traffic load. The Multiple Stress Creep Recovery (MSCR) test results indicated that all the investigated tack coat materials have low rutting susceptibility. The Christensen-Anderson-Marasteanu (CAM) model is also suitable to characterize the dynamic modulus of tack coat material. The new product of tack coat, such as Trackless and Ultrafuse, exhibit greater shear strength than conventional tack coat. The results of laboratory study indicated that the modified direct shear test could be applied to differentiate the quality of different tack coat materials. 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. This study was trying to make an effort to answer some of these questions. Therefore, there is a need to understand fully the performance of different tack coat materials. The related standard and specifications for quality control of tack coat is still under development. Each state highway agency has its own selection procedure for determining which tack coat material is appropriate for a specific area. However, the importance of tack coat to the performance of thin overlays is still not emphasized. 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. to 0.75 in.) seem to be more beneficial than conventional asphalt overlays. In Texas, thin overlays (lift thickness less than 2 in.) and ultra-thin overlays (lift thickness of 0.5 in.
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. Asphalt overlay has been widely used in the United States as a cost-effective maintenance approach to keep the pavement in a satisfactory condition.
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