Distribution properties of internal air voids in asphalt mixtures

X-ray computed tomography(CT) technology was adopted to scan the internal structures of AC-16, SMA-16 and OGFC-16 mixture specimens compacted using Marshall and Superpave gyratory compactor(SGC) methods. Digital image processing technology was adopted to analyze the spatial distribution of their internal air voids. The result shows that the distributions of air voids are not uniform in mixture specimens, and they vary greatly with the compacting styles and gradations of asphalt mixtures. Throughout the specimen height, air void percents are bigger on the top and at the bottom, and are smaller in the middles of the specimens compacted by SGC method, whereas the distribution variances are not marked for the specimens compacted by Marshall method. Throughout the cross sections of the specimens, air voids distribute more in the outside parts than in the middle parts for AC-16 and SMA-16 mixtures. 3 tAbs, 11 figs, 10 refs.