Study On Fatigue Performance Of POE-SBS Composite Modified Asphalt Based On Energy Dissipation Theory

Fatigue property of asphalt binder plays an important role on the fatigue life of asphalt mixture, it is the basic study of pavement fatigue damage problem that evaluating the fatigue life of asphalt effectively. Existing research show that the continuous loading mode was adopted mostly when studying fatigue performance of asphalt binder under laboratory conditions, or adopted adding resting time after continuous loading. All of these stress patterns are not consistent with the actual condition of pavement. In order to study the fatigue perfermance of asphalt binder, intermittent loading mode was adopted to simulating the actual loading mode of pavement in this paper, and the continuous loading mode was used as the reference test group.Thermoplastic elastomer SBS is the most widely used asphalt modifier, one of the disadvantages of SBS modified asphalt is that the fatigue performance is not ideal.Poly olefin Elastomer(POE) has excellent toughness and good workability, it has obvious advantages in improving impact and fatigue properties of polymer composites. On account of this, POE and SBS were adopted to modified the asphalt in this experiment, analyzed the rheological properties of POE-SBS composite modified asphalt, and also the fatigue performance under different loading modes. The main research contents and results are as follows:The influence of POE-SBS ratio and modifier dosage on the performance of asphalt was studied by conducting SHRP single point test, multiple stress creep recovery test and bending creep stiffness test, test results show that POE-SBS composite modified asphalt has both preferable high and low temperature performance when the POE-SBS ratio is 1:9 and the content of modifier is 4.5%. Based on WLF formula and CAM model, using programming method to fit the complex modulus of asphalt, the correlation coefficient of fitted complex modulus and measured complex modulus can reach 0.99 or above. A conclusion can be draw from the analysis of asphalt master curve that the addition of POE has no significant effect on rheological properties of SBS asphalt binder in wide frequency range.Based on the research about fatigue property of 6 kinds asphalt binders under the modes of stress controlled intermittent loading and continuous loading, when using Nf50 and Np20 to evaluate the fatigue performance of asphalt binders, which Nf50 is determined by complex modulus G* and Np20 is determined by dissipated energy, compared with continuous loading mode, the Nf50 and Np20 of 6 kinds asphalt binders under intermittent loading mode are increased by 80%-90% and 90%-100%, respectively. The number of alternating load cycles asphalt binders can withstand under intermittent loading mode is much larger than that under continuous loading mode of the equivalent stress magnitude, so it is unreasonable to study the fatigue performance of asphalt under the condition of continuous loading only.Based on the research about the fatigue performance of 6 kinds asphalt binders with different proportion of POE and SBS, it concludes that Nf50 and Np20 all show a trend of increase then decrease and then increase after the first increase with the increase in the proportion of POE, whether it is continuous loading or intermittent loading mode, and the fatigue life of asphalt added with POE are all higher than that of SBS modified asphalt. It is indicated that the fatigue life of SBS modified asphalt is improved by the introduction of POE. Compare the composite modified asphalt that POE-SBS ratio is 1:9 with the pure SBS modified asphalt, the Nf50-continuous of the former increases of 60% than the latter and the Np20-continuous increases of 54% in continuous loading mode, the Nf50-intermittent of the former increases of 62% than the latter and the Np20-intermittent increases of 60% in intermittent loading mode. It shows that a small amount of POE can greatly improve the fatigue life of asphalt.When using Dissipated Energy Ratio(DR) to characterize the fatigue performance of asphalt, DR can present certain regularity in stress controlled continuous loading mode, but it performes as a series of irregular scattered points in intermittent loading mode. It shows that DR is not applicable to evaluate the fatigue performance of asphalt under intermittent loading conditions, continuity of data should be guaranteed when using DR to characterize the fatigue performance of asphalt.