Development of a New Test Method for Evaluating Fatigue Behavior of Asphalt Mixtures under Tension-Compression Loading Mode

摘要

The primary purpose of this study is to develop a new test method with a self-developed alternative biaxial splitting (ABS) fixture for evaluating fatigue behavior of asphalt mixtures under a tension-compression loading mode. A comparison was performed in the indirect tension (IDT) and ABS test on laboratory-mixed asphalt concrete (AC-13) with an optimum asphalt content of 4.7%. The tests were performed under stress-controlled conditions according to four stress ratios (namely, R = 0.3, R = 0.4, R = 0.5 and R = 0.6) which meant the ratio of given to maximum stress in fatigue testing. A sinusoidal waveform was applied in the fatigue tests at frequencies of 5 Hz and 10 Hz. The results showed that the strain growth rate of the asphalt samples in the ABS fatigue test increased slower than that of in the IDT fatigue test with an increase in loading cycles. When the damage evolution in the asphalt samples under fatigue loading reached the steady state, the ratio of damage change (RDC) of IDT fatigue testing samples changed little maintaining greater than zero all the time. In contrast, the RDC of ABS fatigue testing samples had an alternate positive-negative variation. The laboratory fatigue life of the ABS test was 4 to 23 times more than that of the IDT test at a constant temperature of 20°C. It demonstrated that the creep effect of compressive stress promoted the healing of micro cracks and produced increased fatigue life.