Consideration of HMA resilient modulus (Mr) for M-E pavement design and analysis
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The purpose of this paper is to present the resilient modulus (M r) approach for pavement design and analysis. Different from the traditional dynamic modulus (|E*|) used in the Mechanistic-Empirical Pavement Design Guide (MEPDG), the proposed Mr approach fully simulates the influences of both the rest period and different loading waveforms (i. e. haversine and square loading) on the pavement strain response. In addition to the direct laboratory Mr testing approach, an alternative Mr estimation approach, based on the |E*| test (TP62-03), was proposed and verified through laboratory testing. Furthermore, this paper discussed the necessity of square loading and recommended that the square loading waveforms be used for the top sublayers) of HMA layer; and the haversine loading being used for the rest of HMA layer. Specifically, using the square loading for the top sublayers) of surface HMA layer can eliminate the controversy surrounding the output from the MEPDG: a decrease in predicted modulus with depth in hot weather. Field verification of the Mr approach was demonstrated with the tensile strain data collected from the Federal Highway Administration's Accelerated Loading Facility (FHWA-ALF) test program. Five 4 in. HMA lanes were analyzed and the calculated tensile strains based on the Mr approach were compared with the actual measured strains and very promising results were obtained. However, further field validation is still needed.
