Estimation of the Stiffness of Asphalt Mastics Using Hirsch Model

Mastic properties are very important to the performance of asphalt concrete. Fine and coarse aggregates are usually not directly interacting with asphalt binder but with mastics. Permanent deformation and fatigue cracking tend to occur in the mastics and the interfaces between mastic and aggregate. Mastics demonstrate much more complicated behavior than asphalt binder including permanent deformation, non-linearity, and temperature sensitivity. Two important mastic properties include its shear modulus and permanent deformation. Too low stiffness may lead to high potential of rutting while too high stiffness may lead to cracking. This study targets at estimating the shear stiffness of mastics using the complex shear modulus of binder and the Hirsch model based on binder modulus and the volumetric composition of filler. Predictions of the mastics shear moduli using Hirsch model were compared with experimental measurements at different temperatures and frequencies and show very good agreement. The study also indicates that Time-Temperature superposition algorithms are applicable to mastics for different volume fractions of mineral fillers.