53 Transportation Research Record: Journal of the Transportation Research Board, No. 2037, Transportation Research Board of the National Academies, Washington, D.C., 2007, pp. 53–62. DOI: 10.3141/2037-05 passing No. 200 sieve, and the like. Level 3, considered to provide the lowest level of accuracy, estimates the dynamic modulus of HMA from known properties of similar mixes without performing any laboratory tests. Rehabilitation projects use a similar three-level input scheme. Level 1 uses falling weight deflectometer (FWD) data to backcalcu- late the combined HMA layer modulus. The as-constructed dyna- mic modulus is then estimated from the mix volumetric parameters obtained after testing cored samples. A damage factor is then calcu- lated on the basis of the ratio of the backcalculated modulus to the estimated one. The damage factor is used to develop the dynamic modulus master curve for the field-damaged combined HMA layer. Level 2 uses field cores to measure and calculate the mix volumetric parameters and to measure the resilient modulus in the indirect tensile (IDT) setup. Obtained from these measurements is the damage factor, from which the field-damaged dynamic modulus master curve can be developed. Level 3 obtains the damage factor from correlations with the visual pavement rating; the master curve for the field-damaged dynamic modulus is obtained in the same way as in Levels 1 and 2. OBJECTIVE This paper discusses a project to validate the MEPDG analysis proce- dure designed to characterize HMA layers for rehabilitation purposes. This project took advantage of extensive field tests and material sam- pling from nine sites (eight flexible and one composite) from some of Virginia’s highest-trafficked pavements. The cores from these pave- ments were tested in the laboratory to determine their dynamic mod- uli. Undamaged master curves for the HMA layer were obtained from the volumetric properties and the default Level 2 (Witczak) predic- tion equation (2), while damaged master curves were generated by using FWD data, resilient modulus data, and pavement ratings. BACKGROUND As noted earlier, the proposed MEPDG (Chapter 2, Section 2.2.2.2) suggests three input levels for determining the existing (or field- damaged) HMA dynamic modulus for rehabilitation projects. Input Level 1 For Level 1 design, the MEPDG proposes the following procedure to determine the existing HMA dynamic modulus: 1. Perform an FWD survey on the pavement that needs rehabili- tation and backcalculate the average modulus for the HMA layer, E f , at the field temperature T f . Determination of In-Place Hot-Mix Asphalt Layer Modulus for Rehabilitation Projects by a Mechanistic–Empirical Procedure Amara Loulizi, Gerardo W. Flintsch, and Kevin McGhee This paper summarizes the findings of a project that evaluated the proce- dures proposed by the Mechanistic–Empirical Pavement Design Guide (MEPDG) to characterize existing hot-mix asphalt (HMA) layers for rehabilitation purposes. A total of 33 cores were extracted from nine sites in Virginia to measure their dynamic moduli in the lab. Falling weight deflectometer (FWD) testing and visual pavement rating were performed at the sites, and the resilient modulus was measured in the laboratory. Selected cores were tested for their bulk densities and then for their dynamic moduli. The cores were broken down and tested for their maxi- mum theoretical specific gravity. Finally, an ignition test was performed to find the percentage of binder and to reclaim the aggregate for grada- tion analysis. Volumetric properties were then calculated and used as input for the Witczak dynamic modulus prediction equations to find what the MEPDG calls the “undamaged master curve of the HMA layer.” The FWD data, resilient modulus data, and pavement rating were used to find the damaged master curve of the HMA layer as suggested for Input Lev- els 1, 2, and 3, respectively. It was found that the resilient modulus data needed for a Level 2 type of analysis (as proposed in Chapter 2 of the MEPDG) does not represent the entire HMA layer thickness, and there- fore it was recommended that this analysis should not be performed. The use of Level 1 data is recommended because FWD testing appears to be the only procedure investigated that can measure the overall condition of the entire HMA layer. The dynamic modulus is the property used in the proposed Mechanistic–Empirical Pavement Design Guide (MEPDG) (1) to characterize hot-mix asphalt (HMA) layers. For designing new pave- ments, Chapter 2 of the proposed guide suggests three input levels for the dynamic modulus. Level 1, considered to be the most accurate level of input, obtains the dynamic modulus through a series of labo- ratory tests performed at different temperatures and different loading rates to obtain a master curve for the design mix. Level 2, considered to provide an intermediate level of accuracy, estimates the dynamic modulus of HMA from other measured properties of the mix, such as effective binder content, binder viscosity, air void content, percentage A. Loulizi, École Nationale d’ingénieur de Tunis, ENIT Département Génie Civil B.P. 37 Le Belvédère, 1002 Tunis, Tunisia. G. W. Flintsch, Via Department of Civil and Environmental Engineering, Center for Safe and Sustainable Infrastruc- ture, Virginia Tech Transportation Institute, Virginia Polytechnic Institute and State University, 3500 Transportation Research Plaza, Blacksburg, VA 24061- 0105. K. McGhee, Virginia Transportation Research Council, Charlottesville, VA 22903. Corresponding author: G. W. Flintsch, flintsch@vt.edu.