Asphalt Concrete (AC) layer of a highway pavement is typically constructed by successive compaction of multiple thin layers. After construction, these layers may not deteriorate at the same rate over the years due to a number of factors such as moisture, aging and so on. Proper selection of pavement maintenance and rehabilitation strategy is dependent on the structural condition evaluation of these thin AC layers. Therefore, this study is performed to evaluate multiple thin AC layers of an instrumented flexible pavement section at Mile Post (MP) 141 on Interstate 40 (I-40) near Albuquerque, New Mexico. To facilitate, nondestructive tests such as Ground Penetrating Radar (GPR), Falling Weight Deflectometer (FWD), and Portable Seismic Property Analyzer (PSPA) were conducted on this pavement section. AC layer thicknesses were predicted by the 2.0 GHz air-coupled GPR antenna, and the predicted thicknesses are fairly accurate based on a comparison with core thicknesses at selected locations. In addition, the GPR predicted smaller thicknesses for the top AC layer at some locations which were marked as delaminated zone. Later, the AC thickness and modulus interpretation from the PSPA test also confirmed those delaminated locations. It was observed that the PSPA is the most effective for the evaluation of the top AC layer. In case of modulus prediction of all thin AC layers together, the FWD test has been proved to be the best option. In addition, accuracy of modulus prediction by the FWD test is enhanced due to incorporation of the GPR predicted layer thicknesses. Finally, it is recommended to conduct the combined GPR, PSPA, and FWD tests on a flexible pavement to ensure an efficient and accurate structural evaluation of thin AC layers.
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