Numerical modelling of crack propagation in road composite pavements

<p dir="ltr">Reflective cracking remains a critical issue affecting the performance and longevity of composite pavements, particularly in high-traffic areas subjected to varying environmental conditions. This research investigates crack propagation in composite pavements commonly used in New South Wales (NSW), Australia, focusing on numerically modelling reflective cracking. A key aspect of the study is evaluating the existing minimum asphalt overlay thickness requirement of 175 mm, questioning its empirical foundation and suitability across diverse pavement configurations.</p><p dir="ltr">Using the Extended Finite Element Method (XFEM) in ABAQUS, this study simulates crack initiation and propagation under different conditions, incorporating variations in asphalt-wearing course materials, subgrade strengths, and boundary constraints to reflect field scenarios. The numerical models are validated against laboratory data from the Austroads APT6330 project, ensuring their reliability in predicting reflective cracking behaviour. The Maximum Principal Stress (MAXPS) criterion is applied to analyse crack initiation and growth, providing insights into material performance under different loading and support conditions.</p><p dir="ltr">Findings indicate that asphalt material properties and boundary conditions significantly influence reflective cracking severity. Among the boundary conditions analysed, BC2—representing differential slab movement—exhibited the most severe cracking patterns. The results suggest that the standard 175 mm minimum overlay thickness may be insufficient under such conditions, potentially necessitating an increase to mitigate uncontrolled cracking. The required thickness adjustment depends on the specific materials used in the wearing course and subbase layers.</p><p dir="ltr">Conversely, the study identifies scenarios where asphalt overlay thickness could be reduced without compromising pavement performance. Composite pavements incorporating a lean mix concrete subbase demonstrated improved crack control when cracks were intentionally spaced to manage reflective cracking and limit differential movement near joints. Active crack control—an established approach in continuously reinforced concrete pavements (CRCP)—emerges as a viable strategy for composite pavements with lean-mix concrete subbases. This method enhances crack predictability and reduces the need for excessive overlay thickness.</p><p dir="ltr">By refining guidelines for asphalt thickness and material selection, this research provides practical recommendations to improve the resilience and cost-efficiency of composite pavement designs. The study advances current pavement engineering methodologies, offering validated numerical models to inform future design and maintenance practices.</p>