Fracture Healing Properties of Asphaltic Material under Controlled Damage

The self-healing properties of asphalt materials present a new means to achieve reliable, durable, and sustainable asphalt pavements through maximizing the effect of microdamage recovery. However, healing (healing of fracture damage) normally happens in conjunction with the recovery of viscoelastic deformation, making the analysis of healing complicated. This paper conducts a comprehensive evaluation of the fracture healing properties of asphalt binder under different damage levels while excluding the effect of viscoelastic recovery. It develops a simple healing testing protocol and a data analysis method that can create fracture damage in the material, assess the level of damage before rest periods, monitor the change of material properties during the healing process, and evaluate the effect of fracture healing on material performance. Healing functions are developed to model the healing characteristics of asphalt binder during the rest under different damage levels and temperatures. Based on the testing results for two binders (PG64-28 and PG70-28), it is found that fracture healing dominates the long-term modulus recovery, while the viscoelasticity contributes greatly for early modulus gain right after the load is removed. The fracture healing properties and the recovery of fatigue performance are strongly affected by temperature and the damage level prior to rest.