Low-Temperature Fatigue Performance of Polymer-Modified Asphalt Mixtures Evaluated by Cyclic SCB Testing

Source abstract

Fatigue cracking is one of the most critical deterioration mechanisms affecting the service life of asphalt pavements. This study investigates the fatigue crack propagation behavior of asphalt mixtures modified with styrene-butadiene-styrene (SBS), Enprene 611, Enprene 701, and crumb rubber (CR) under low-temperature conditions. Semi-Circular Bending (SCB) specimens with notch depths of 10, 20, and 30 mm were subjected to cyclic loading at −20°C. Static SCB tests were first conducted to determine the reference load levels, and the resulting values were used to establish the loading protocol for the cyclic experiments. The deformation–load cycle relationships obtained from the cyclic SCB tests were analyzed to evaluate fatigue resistance and crack propagation characteristics. The results showed that all modifiers improved fatigue performance compared with the virgin and control mixtures by reducing deformation accumulation and delaying crack growth. Among the additives, Enprene 611 exhibited the highest fatigue resistance, particularly at a dosage of 4%, providing the greatest number of load cycles and the lowest deformation growth rate. SBS also significantly enhanced fatigue performance, while Enprene 701 and CR provided moderate improvements. Increasing notch depth accelerated crack propagation and reduced fatigue life for all mixtures. Based on the overall performance, the mixtures were ranked as Enprene 611 > SBS ≈ Enprene 701 > CR > Control > Virgin mixture. The findings indicate that polymer modification, particularly with Enprene 611, is an effective approach for improving the low-temperature fatigue crack resistance of asphalt mixtures and extending pavement service life.