MICROSCOPIC OBSERVATION OF DEGRADATION BEHAVIOR IN RECYCLED ASPHALT MIXTURES UNDER BENDING FATIGUE TESTING

Abstract

 In contemporary asphalt pavement maintenance, corrective interventions are generally undertaken after the progression of damage, with the extent of deterioration determining the timing and type of repair. Nevertheless, the fundamental mechanical properties of asphalt mixtures and the underlying mechanisms of degradation, particularly cracking, remain insufficiently understood. The present study aims to elucidate the mechanisms governing crack initiation and propagation in asphalt mixtures. To achieve this, bending fatigue tests in combination with X-ray micro-computed tomography (micro-CT) imaging were performed on specimens of both virgin and recycled asphalt mixtures. The CT datasets were subsequently subjected to image processing techniques, allowing for detailed microscopic observation of crack development within the mixture specimens. The experimental results demonstrated that cracks emerged in three characteristic locations in both virgin and recycled mixtures following fatigue loading. Moreover, distinct differences were identified in the patterns of crack formation surrounding aggregate particles, indicating a potential influence of material composition on fracture behavior. This paper provides an interpretation of the factors and mechanisms underlying these microscopic observations and further discusses the validity and effectiveness of the applied image-processing methodology for analyzing microstructural damage in asphalt mixtures.