Trr 1171
Several moduli have been used to characterize asphalt mixtures. However, little information is available about which modulus is most appropriate to use in a given situation. This paper provides rational understanding, based on principles of strength of materials, of the moduli commonly used for structural evaluation of asphalt mixtures. Young's, shear, bulk, complex, dynamic, double-punch, resilient, and Shell nomograph moduli are discussed. The assumptions and limitations of these moduli are evaluated. It is concluded that the resilient modulus is more appropriate for use in multilayer elastic programs than are other moduli because it represents the elastic stiffness of the material after many load repetitions. Also, moduli predicted from the dynamic nondestructive testing of pavements are most representative of the in situ resilient moduli of the materials. If other moduli are used in the theoretical analysis of pavements, caution should be exercised to avoid inconsistency of assumptions