Impact of Different Loading Patterns with Short Duration on the Permanent Strain of Asphalt Mixture

Abstract The suggested procedure for measuring the permanent deformation of asphalt concrete mixtures in the standard laboratory tests are based on using a single-hump loading. This loading type can only simulate the single-axle load, whereas pavements are subjected to single, tandem, and tridem axles at different speeds. On the other hand, the behavior of asphalt mixtures is affected by the loading pulse duration as a function of moving speed. Therefore, the laboratory investigation of permanent deformation is more logical under similar loading conditions. Accordingly, in this study, the effect of the type and duration of loading on the permanent strain of asphalt mixture have been examined at three stress levels. To investigate, the unconfined cyclic creep test was performed on asphalt specimens and, finally, the impacts of each variable on the permanent strain were evaluated, as discussed here in detail. Based on the findings of this research, it is concluded that for various loading patterns, the permanent deformation caused by the tridem axles can be greater than that caused by single and tandem axles, and under tandem axles it can be greater than that under single axles; the effects are dependent on the loading duration indeed. Also, this study showed that the impact of pulse duration on the changing trend of permanent strain is dependent on loading pattern and stress level.