Evaluation of bitumen's fatigue resistance - a comparative study

Since asphalt mixtures are based on bituminous binders, a complex organic viscoelastic and time-temperature dependent material, they naturally tend to change their performance. Due to increasing traffic and axle loads, fatigue resistance is one of the most important properties of asphalt materials. The standard procedure of asphalt mixture evaluation is determining their fatigue resistance, but it is also possible to determine the fatigue resistance of bitumen on binders level. This article presents the research results of asphalt binders fatigue resistance, two paving grade bitumens and one polymer modified bitumen, in unaged and aged states. Asphalt binders were tested using three methods according to the Superpave criterion, the time-sweep fatigue test and the linear amplitude sweep test (LAS). Analysis and evaluation of the test results were carried out due to fatigue and time consumption of the testing procedure. In terms of determining the fatigue phenomenon, both in bitumen and asphalt mixture levels, the most critical aspect is the time severity of the tests and the necessity to perform such advanced testing on many test specimens. The results show that the G*·sinδ parameter should not be used to validate the fatigue life of bitumen. The result from fatigue time-sweep and LAS tests appear to give similar outcomes and correlate better, especially the LAS in higher strain levels. Furthermore, regarding test time consumption, LAS requires less time to perform and gives a more flexible approach to determining bitumen fatigue life.