A self-healing material has the inherent ability to partially reverse damage. It is a common consensus that healing of damage has a substantial effect on the performance of asphalt pavements. It is important to understandthe mechanisms that are responsible for healing in asphalt binders, develop a model to predict healing that is based on these mechanisms, and develop test methods by which to determine the properties required for use withsuch a model. In previous work, the authors proposed a healing model for asphalt materials. This model is comprised of a convolution of wetting and intrinsic healing processes that occur across a crack interface. According to the proposed convolution process, intrinsic healing or strength gainacross a crack surface occurs in two steps: an instantaneous strength gain due to the interfacial cohesion between the crack faces, and a time dependent strength gain due to intermolecular diffusion and randomization across the crack interface. A modified form of the Avrami equation, that includes a parameter for instantaneous strength gain, is used to describe the intrinsic healing in asphalt binders. A test method based on the use of a Dynamic Shear Rheometer is described which can be used to estimate the parameters of the intrinsic healing function. Five different asphalt binderswere studied with considerably different compositions. Limited validation of this test method and the intrinsic healing model is presented by comparing the parameter related to instantaneous healing to the thermodynamic work of cohesion for the selected binders.
Samenvatting