Asphalt pavements play a crucial role in constructing durable and sustainable road infrastructure. In recent years, with the advancement of sustainability and circular economy goals, reclaimed asphalt (RA) has been widely used in road construction. While the use of RA effectively reduces resource consumption and environmental impact, research on the fatigue and healing performance of asphalt mixtures and binders with high RA content remains relatively limited. This study aims to evaluate the healing performance of binder components from three asphalt mixtures commonly used in the base layers of Dutch pavements, employing multiple healing test protocols and healing indices. Two of these binders contain a high proportion of RA bitumen.

To achieve the research objectives, fatigue and healing tests were conducted on three different asphalt binders: Binder 1, composed entirely of fresh bitumen; Binder 2, a blend of high RA content bitumen with softer fresh bitumen; and Binder 3, which includes high RA bitumen content, fresh bitumen, and the rejuvenator. Fatigue performance was evaluated using Time Sweep (TS) and Linear Amplitude Sweep (LAS) tests to determine the fatigue life of each binder. Additionally, healing performance was assessed through single-rest period and multiple-rest period Time Sweep Healing (TS-H) tests, as well as Linear Amplitude Sweep Healing (LAS-H) tests. To evaluate healing performance, two different indices were used: the Healing Shift Factor (SFh), based on fatigue life extension, and the Healing Index (HI), based on modulus recovery.

The differences between single and multiple rest periods TS-H tests highlight the limitations of single rest period tests in fully capturing material healing capacity, indicating that more complex loading patterns should be explored for more comprehensive assessments. The variations in healing potential results across different test protocols and indices suggest that the healing performance of binders is highly sensitive to test protocol and indices selection.

Based on the described approach, a better understanding of the healing performance of different asphalt binders is achieved. Conclusions and future recommendations for research in this field were provided at the end of this research.

The Netherlands has one of the densest road networks with over 140,000 km of roadways. Fatigue cracking is an important distress in flexible pavements. This form of distress results from the application of repeated traffic loading which causes failure. Fatigue cracking assessment on various base layer asphalt mixtures including reclaimed asphalt pavement materials and recycling agents has been addressed in this research work. This research work aims to develop a method for quantifying and assessing this fatigue characterization including the self-healing mechanism of asphalt mixtures using Visco Elastic Continuum Damage Theory. The self-healing in asphalt mixtures was assessed by incorporating group-rest healing periods in a self-developed laboratory testing method. The reliable self-healing models for asphalt mixtures with recycled asphalt materials and recycling agents based on temperature, damage state, and rest periods were predicted using the damage characteristics curve (C-S). Bottom-up cracking in base layer asphalt mixtures was modeled and studied using finite element modeling software FlexPAVE based on the Visco-Elastic Continuum Damage theory. A vivid assessment of mixtures for fatigue and healing characterization is discussed in this research work.

This research work is interrelated with an ongoing project, which aims at developing a protocol to determine the shift factors for the fatigue life of asphalt mixtures to correct healing and aging. The project runs under the umbrella of Knowledge-based Pavement Engineering (KPE), a joint program among Rijkswaterstaat, TNO, and TU Delft. Dura Vermeer is contributing partner to this MSc graduation research work as well.