Fatigue behaviours of asphalt mixture at different temperatures in four-point bending and indirect tensile fatigue tests

The laboratory fatigue test for the asphalt mixture is generally conducted at the intermediate temperatures (10 °C to 20 °C). Some research findings reveal that fatigue cracking may also appear in the asphalt layer at higher temperatures. Motivated by these findings, the present research investigated and compared the fatigue behaviours of the asphalt mixture at a wide range of temperatures (15 °C to 40 °C with an interval of 5 ℃) in four-point bending (4 PB) and indirect tensile (IDT) fatigue tests. The dense-graded asphalt mixtures (AC-13) using neat asphalt binder and Styrene-butadiene-styrene (SBS) modified asphalt binder are applied for evaluation. It is found that a uniform law exists for the stiffness evolution of the asphalt mixture in the fatigue test: as the stiffness of the asphalt mixture declined to about 70% of its initial stiffness, the asphalt mixture starts to experience the stable fatigue damage accumulation stage. The temperature affects the fatigue life of the asphalt mixture oppositely in the 4 PB and IDT tests. In the 4 PB test, the rising temperature causes an increase in the fatigue life of the mixture. However, in the IDT test, the fatigue life of the mixture decreases obviously with the increase of temperature. The model Nf=a(1/F)becT is proposed and developed to describe the relationships among fatigue life (Nf), temperature (T) and stress/strain level (F) of asphalt mixture in 4 PB and IDT tests. The developed models provide reference data for evaluating the fatigue resistance of the asphalt layer under various temperature and strain/stress conditions.