SEM Analysis on Fracture and Healing of SandAsphalt Mixtures

One of the major reasons for the discrepancy between the fatigue lives of asphalt concrete pavements predicted from a laboratory and observed in the field is due to rest periods that are not considered realistically in the laboratory experiments. During a rest period, relaxation and chemical healing occur simultaneously in an asphalt concrete layer. Understanding the mechanism of healing is important in order to predict the fatigue life of asphalt concrete pavements. A replication technique for scanning electron microscopy is employed to study the process of fracture healing of sand-asphalt mixtures. Three binders are investigated: Texaco AC-5, Texaco AC-20, and styrene-butadiene rubber latex-modified Texaco AC-5. This technique provided information about the fracture patterns of these binders and demonstrated the incompatibility of latex with Texaco AC-5. The degree of healing was found to be dependent upon healing time and binder viscosity. Initial surface penetration and structural bonding concepts provide a basis for modeling the healing mechanism of asphalt concrete. ASCE.

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