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Evaluation of Thin Hot Mix Asphalt Overlay: Field Evaluation Summary Report

Preserving the road surface and maintaining it at a proper functional level is essential to safe transportation. Among alternatives for pavement surface treatment, thin asphalt overlays have been utilized and promoted by several states to serve this need. To evaluate the performance of such overlays and develop relevant specifications, PennDOT initiated a four-year research program with Penn State. The project carried several major objectives. One was to assess best practices for design and construction of such mixes through field application of three pilot projects and conducting necessary laboratory testing. Second was to evaluate the performance of such mixes placed in these pilot projects through visual survey and pavement condition measurements. Third was the use of existing advanced technology such as thermal imaging and ground-penetrating radar to determine the uniformity of such mixes during placement in regard to temperature and density. Finally, it was the intention of the project to develop relevant specifications and guidelines for thin asphalt overlays. Field evaluations, in general, indicated satisfactory performance of these roads. This report does not cover the research team’s field work during construction. The construction-related work, including thermal imaging and ground penetrating radar measurements, is covered in separate reports. This summary report presents a brief presentation of results from pavement condition evaluation conducted at several intervals during the time this research was conducted.

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