Recovery of asphalt mixture stiffness during fatigue loading rest periods

- Introducing rest periods in fatigue loading of asphalt mixtures were examined.
- Neat and polymer modified asphalt was tested, with the polymer modified asphalt having a higher fatigue life.
- Rest periods extended fatigue life significantly at intermediate temperatures (10 °C and 20 °C).
- Rest periods at colder temperatures would have a detrimental effect on the fatigue life of the mixture.

Asphalt is a self-healing material that has the ability to restore part of its stiffness and strength during rest periods and elevated temperatures, leading to a significant extension in service life. The self-healing of asphalt mixtures has been investigated in this paper using a modified tension-compression fatigue test. Asphalt mixture specimens, prepared with different binders (neat and SBS polymer modified) and gradations, were sinusoidally loaded in strain control mode, with a rest period being introduced at the end of each loading period. Rest period temperatures varied at 0, 10 and 20 °C. This loading-rest sequence was repeated three or four times. For some tests, the samples were loaded to complete failure after the final rest period. The asphalt mixture with the polymer modified asphalt had much better resistance to fatigue loading compared to the samples with neat binder. The stiffness of the sample represented by the norm of complex modulus (|E∗|) showed an increase during the rest periods. The fatigue life in terms of number of loading cycles was higher with an increase in rest time temperatures. Moreover, the fatigue life values of the samples with rest periods were significantly higher than for continuously loaded samples loaded under the same conditions.