Fatigue Cracking Characteristics of Ultra-Large Particle Size Asphalt Mixture Under Temperature and Loading Using Digital Image Correlation Techniques

This study quantitatively investigates the fatigue cracking behavior of ultra-large particle size asphalt mixture (LSAM-50) under coupled temperature and stress effects. Fatigue tests were conducted across temperatures ranging from -15 °C to 35 °C and stress levels (0.3-0.9 of splitting tensile strength), with crack evolution tracked in real time using digital image correlation (DIC). Key parameters, including main crack length, crack density, curvature, fractal dimension, and strain, were analyzed to characterize crack propagation. Results revealed a three-stage process: initiation, development, and acceleration to failure. Increasing temperature or stress level accelerated horizontal/vertical displacement rates, main crack expansion, and strain accumulation, while reducing crack density and fractal dimension. A fatigue prediction model, Lg<i>N</i> = 9.741 - 1.213Lg<i>ε</i> - 0.017<i>T</i> - 1.579<i>S</i> (<i>R</i>² = 0.954), was established, linking fatigue life (<i>N</i>) to strain (<i>ε</i>), temperature (<i>T</i>), and stress level (<i>S</i>). This model enables precise fatigue life estimation under varying environmental conditions. For instance, the model predicts a 60% reduction in fatigue life when temperature rises from 15 °C to 35 °C at <i>S</i> = 0.7, highlighting its utility in material selection for climate-resilient infrastructure, offering a critical tool for optimizing LSAM-50 in pavement design. By integrating DIC-derived crack metrics and mechanistic insights, this work not only enhances understanding of the fatigue cracking behavior of LSAM-50 but also provides valuable insights for the design and optimization of materials under varying environmental conditions.