Characterization of the healing potential of asphalt binders with separation of thixotropy after cyclic loading

Considering the self-healing property of asphalt binders in material selection and pavement design can help improve pavement performance and reduce maintenance costs. The study of self-healing of asphalt materials gradually is becoming an important step in the design of durable pavements. Traditionally, the performance recovery of asphalt binders has been attributed only to microcrack healing, which may lead to an overestimation of the self-healing ability. This is because an increasing number of studies have shown that the driving mech-anism of asphalt binder performance recovery includes not only self-healing but also thixotropy. In order to accurately quantify the self-healing ability of asphalt binders without the influence of thixotropy, a novel test procedure and a three-step analysis method are proposed. The novel test procedure includes the large amplitude time sweep test and the small amplitude time sweep test. The three-step analysis method consists of establishing a thixotropy relationship between the dynamic shear modulus and the phase angle, calculating the effective modulus from the phase angle data via the thixotropy relationship, and determing the healing degree of asphalt binders by separating the thixotropy. The results show that the recovery of the dynamic shear modulus of asphalt materials results from the combined action of thixotropy and self-healing. And thixotropy plays a prominent role in the dynamic shear modulus recovery at the initial resting period. The contribution of self-healing to dynamic shear modulus recovery gradually increases with increasing resting time. Without excluding the influence of thixotropy, the self-healing ability of asphalt binders is overestimated, especially the short-term self-healing ability.