Impacts of Freeze-Thaw Cycles on Microscopic Characteristics of Recycled Mixture Using Foamed Asphalt

In order to explore decay rule of moisture damage resistance of cold recycled mixture using foamed asphalt, 6 kinds of gradation cold recycled mixture using foamed asphalt was selected to study strength characteristics. Meanwhile, the indirect tensile strength test and computerized tomography (CT) test were conducted to analyze air voids gradation and the most probable air voids diameter under different freeze-thaw cycles. As the freeze-thaw cycle increased, the strength of the recycled mixture prominently reduced, the micro-void significantly decreased, while the large gap increased significantly. The CT and indirect tensile strength (ITS) test results show that the more the micro-void is, the higher the strength when they have the same total air voids. The more the large volume voids is, the lower the strength of specimens. The division method of air voids which is in cold recycled mixture of using foamed asphalt was put forward. The first two freeze-thaw cycles of cold recycled mixture had significant influence. The larger the initial void volume is, the larger the most probable air void is.