In-situ Asphalt Master Curve Construction Using Non-destructive Testing Techniques
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For in-situ asphalt concrete characterization, the MEDPG recommends using the falling weight deflectometer (FWD) to determine the dynamic modulus in combination with the construction of the master curve using the predictive equation. If there is adequate asphalt concrete thickness, asphalt cores may be tested using AASHTO TP 62 to determine the dynamic modulus and construct the master curve, however these cores may not be representative of the actual pavement condition since they may be extracted from select areas showing minimum damage. Both the predictive equation and AASHTO TP 62 require destructive core extraction and can be too costly for many transportation agencies. Recently, the Multichannel Analysis of Surface Waves (MASW) technique has shown to provide accurate non-destructive estimates of the in-situ asphalt concrete dynamic modulus, which may complement the FWD backcalculation process, however the values only constitute the upper two thirds of the master curve, while FWD determined moduli values generally constitute the lower portion of the curve. Therefore, it is a requirement to correct surface wave measured moduli to a standard design frequency using the master curve. To date, the master curves utilized in correcting seismic measured moduli have been constructed using conventional methods and have not incorporated the seismic data into the construction process. There is currently no in-situ non-destructive test method available to measure the dynamic moduli at the range of frequencies required to construct the master curve and researchers have not attempted to construct the master curve in-situ ultimately making the master curve more accessible for asphalt concrete characterization. This research demonstrates the construction of an in-situ non-destructive master curve using a combination of MASW and FWD data collected over a range of temperatures, which then provides a technique to correct the MASW data for enhancing the FWD backcalculation process or to seed the AC modulus directly. Additionally, for MASW moduli correction, the addition of the surface wave data into the master curve construction process is extremely important for providing the most accurate results when used in design.