Evaluation Of Fatigue Life Of High Modulus Asphalt Concrete With Use Of Three Different Definitions

The fatigue life of an asphalt mix is defined as the number of load repetitions at which the crack initiation phase ends and macro cracks start to grow (crack propagation/failure phase). The problem is how to determine in an objective way this number of repetitions. Three different definitions for the fatigue life were applied and compared to each other using three different Polish asphalt mixes. Twelve beams of SBS-modified asphalt mix (mix A), 12 beams of the HiMA mix (mix B) and 14 beams of an ordinary Polish asphalt mix (mix C) were tested in a four-point bending (4PB) device in controlled deflection (strain) mode at 10 Hz and 10 degrees C. During fatigue development, three different phases typically may be indicated (plus so-called transition zone). Based on the locations of the fatigue life (obtained on the basis of three different definitions) with respect to the characteristic fatigue phases a proposal for a new fatigue life definition was made. The location of this fatigue life definition will always fall in the transition zone between the fatigue initiation phase and the failure phase. The main advantage of this definition is that it can be used in automatic processing of fatigue data.