Interpreting fatigue tests in hot mix asphalt (HMA) using concepts from viscoelasticity and damage mechanics

Abstract

The upcoming Brazilian asphalt pavement design method is likely to recommend, in a more basic level, the controlled force indirect tensile fatigue test as a tool for asphalt mixture fatigue characterization. In a more advanced level, mechanistic characterization includes the damage properties measurement for subsequent material behavior simulation. In this paper two different asphalt mixtures were investigated. The stiffer one was obtained after aging of the original mix. They presented similar behavior when it comes to damage properties (damage characteristic curve following the Simplified Vis-coelastic Continuum Damage - S-VECD - model). However, the aged mix needed six times more cycles to failure, compared to the original one, in the indirect tensile fatigue test. The force control, instead of the stress control, leads to the application of different stresses for different materials.As there is no signal inversion, creep flow accumulates, leading to damage and failure. Stiffer mixtures and mixtures presenting less viscous behavior tend to present a better response when those tests are considered. Consequently, it can lead to false conclusions about asphalt mixture fatigue resistance.