Exploring bitumen self-healing mechanisms at the aggregate interface with atomic-scale insights

International Journal of Pavement Engineering, vol. 26

Abstract

Bitumen’s self-healing is crucial for restoring performance, yet its microscopic mechanisms at bitumen-aggregate interface remain poorly understood. This study employed molecular dynamics methods to construct the micro-crack and contact angle models, evaluating how aggregate type, temperature, aging, and pressure affect self-healing. The findings reveal that the bitumen self-healing ability on aggregate surfaces is driven by self-diffusion in the lower layer. Although the adhesion of aggregates limits the diffusion of bitumen molecules, the aggregate surface also serves as the foundation for bitumen diffusion. Owing to the high mobility, saturates in bitumen play a critical role in driving the self-healing by facilitating rapid molecular rearrangement. Bitumen demonstrates stronger self-healing on calcite than quartz due to superior diffusion performance. Dynamic contact angle analysis further supports this, revealing that bitumen sliding resistance is lower on calcite than on quartz. Elevated temperature reduces viscosity and modulus, improving diffusion and boosting self-healing, whereas aging increases bitumen polarity, hindering self-healing. External pressure hinders thermally driven bitumen self-healing on aggregate surface but significantly enhances compression-induced healing. It also promotes denser molecular packing at interface, thereby improving bitumen–aggregate adhesion. This work advances the microscopic understanding of self-healing at bitumen-aggregate interface and offers insights for improving bitumen’s self-healing capabilities.

Authors 2

1. Markus Oeser Aachen Institute of Highway Engineering

   RWTH Aachen University · Federal Highway and Transport Research Institute

   Affiliation as printed

   Federal Highway and Transport Research Institute (BASt)

   Institute of Highway Engineering, RWTH Aachen University

   Federal Highway and Transport Research Institute (BASt), Bergisch Gladbach, Germany

   Institute of Highway Engineering, RWTH Aachen University, Aachen, Germany

2. Pengfei Liu corresponding Aachen Institute of Highway Engineering

   RWTH Aachen University

   Affiliation as printed

   Institute of Highway Engineering, RWTH Aachen University

   Institute of Highway Engineering, RWTH Aachen University, Aachen, Germany