Evaluation of asphalt concrete's fatigue behavior using cyclic semi-circular bending test

Fatigue cracking in asphalt concrete (AC) is one of the major distresses that cause premature failure of flexible pavements. Fatigue tests are often lengthy, cumbersome, and expensive. Therefore, in the performance-related mix-design specifications, some static tests are recommended due to their simplicity. The monotonic semicircular bending (SCB) test is among the most popular. Even though the SCB test is practical, the actual number of cycles to failure due to cyclic loads cannot be obtained. Implementing SCB testing under cyclic loading conditions for AC performance evaluation could be promising. This study aims to develop a cyclic SCB fatigue testing method. To this end, SCB specimens were produced, and static SCB fracture testing was first conducted to determine the loading levels of the cyclic SCB fatigue test. Then, cyclic SCB tests were conducted by varying load levels to obtain the S-N (stress-fatigue life) curves. To demonstrate the applicability of the proposed framework to differentiate fatigue behavior of mixtures, two AC mixtures were designed and subjected to the proposed protocol, varying the type of aggregate (gneiss and mica schist). Additionally, the S-N curves from cyclic SCB tests were compared to the ones from indirect tensile (IDT) fatigue tests. A considerable similarity in the results between the two approaches (SCB vs. IDT) under cyclic loading was observed, while SCB showed good test repeatability. The SCB configuration with a pre-notch allows fracture mechanics-based testing to monitor the cracking mechanisms and promote rapid cracking evolution, which can reduce testing time.

Automated summary

Fatigue cracking in asphalt concrete (AC) is a major issue in flexible pavements. Current fatigue tests are time-consuming and expensive, and static tests are recommended in mix-design specifications for their simplicity. This study aims to develop a cyclic SCB fatigue testing method for AC performance evaluation. The results from the cyclic SCB tests were compared to those from indirect tensile (IDT) fatigue tests, showing good repeatability and similarity in the results.