Effect of binder film distribution on the fatigue characteristics of asphalt Binder/Filler composite based on image analysis method

As a composition of asphalt binder and mineral fillers, asphalt mastic plays a significant role in the fatigue resistance of asphalt mixtures. At the mastic scale, the existence of fillers may rearrange the distribution of asphalt binder and then influence the fatigue characteristics of the binder/filler composite. The effect of content and size distribution of fillers on the binder film distribution in the asphalt mastic were evaluated by a series of image acquisition and processing methods, including scan electronic microscope (SEM), laser diffusion analyzer (LDA), randomly generation algorithm and morphology analysis. A normal distribution model could be used to fit the thickness distribution curve of the binder film within the asphalt mastic perfectly. The expected value (E_binder) and peak value (P_binder) were proposed to quantify the average level and uniformity of the binder film thickness, respectively. The rheological and fatigue properties of the asphalt mastic were evaluated by the time–temperature sweep (TTS) test and a modified linear amplitude sweep (LAS) test. Based on the correlation results, it could be found that asphalt mastic with higher filler contents and finer filler size distribution present a thinner and more uniform binder film distribution, which may increase the fatigue life at small strain level of 0.1% and the strain sensitivity under cyclic loading. The morphology analysis provides new insight to quantify the relationship between the microstructure characteristics and fatigue performance of asphalt mastic.