Understanding the influence of temperature and frequency on the fatigue resistance of bitumen

Fatigue performance of bitumen holds great importance in the design and durability of asphalt pavements. However, there are still gaps in knowledge on the influence of specific experimental conditions on the degradation of bitumen under cyclic loading. Stress-controlled fatigue tests at three temperatures (-10 degrees C, 15 degrees C and 20 degrees C) and two loading frequencies (10 Hz and 20 Hz) were performed on cylindrical specimens of a 50/70 grade bitumen, using a recently developed fatigue testing protocol in the Dynamic Shear Rheometer (DSR) equipment. Experimental data were analysed through multiple analysis approaches, including a novel 'failure lines' method that uses the dissipated energy (DE) of the material and the number of cycles to failure (N-f). Experimental results corroborated the impact of temperature and frequency testing conditions on the fatigue response of the bitumen. For example, at 200 kPa and 20 degrees C, the bitumen dissipated 3.07 times more energy at failure at 10 Hz than at 20 Hz; while at 400 kPa and 10 degrees C, the bitumen only dissipated 1.07 times more energy at 10 Hz than at 20 Hz. Also, depending on the applied stress, the bitumen tested at 10 Hz dissipated between 2.45 and 4.02 times more energy at 20 degrees C than at 15 degrees C, and between 4.11 and 6.52 times more energy at 15 degrees C than at 10 degrees C. Additionally, 15 degrees C was identified as a 'frequency-free transition temperature' for this bitumen, as the 'failure lines' at both frequencies overlapped. Finally, a new temperature and frequency independent fatigue representation was identified when analysing the initial DE and N-f data. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study revealed the influence of temperature and frequency testing conditions on the fatigue response of bitumen, showing significant differences in energy dissipation at failure under different conditions. Additionally, a "frequency-free transition temperature" was identified for the specific bitumen studied.