Deterioration of Cold Recycled Mixtures Using Foamed Asphalt in Seasonal Frozen Region

The cold recycled mixtures using foamed asphalt (CRMF) has been widely used in pavement construction with many ecofriendly advantages. However, the material with a large void fraction is more vulnerable to freeze-thaw cycles in seasonal frozen regions usually. Although some efforts on the properties and applications of CRMF are expended, the regular of decay of the material in seasonally frozen region remains insufficient with urgently further studies. This paper intends to investigate the deterioration of CRMF under seasonal freeze-thaw cycles. First, the cylindrical CRMF specimens experienced various freeze-thaw cycles to simulate the seasonal frozen environment. Second, the indirect tensile asphalt cracking test (IDEAL-CT) and the indirect tensile fatigue (ITF) test were conducted. The strain field was recorded by the digital image correlation (DIC) technology in the IDEAL-CT and the ITF test. The influences of freeze-thaw cycles on the properties of CRMF were evaluated with the void fraction, failure energy, cracking tolerance index, fatigue life, and crack tortuosity. The IDEAL-CT and ITF results showed the specimen has a primary cracking area. A good correlation between void content and failure energy was verified. As the void content rose, the crack tortuosity and fracture energy fell with the increase of freeze-thaw cycles. Moreover, the failure energy is a more accurate index to describe the cracking resistance of the CRMF from the aspects of crack initiation and propagation. The decay of fracture resistance and fatigue life of the CRMF with freeze-thaw cycles can be accurately described by the exponential model. In the ITF test, the average strain in the primary cracking area represented the nature of fatigue damage of CRMF better than that collected according to BS EN12697-24.