Development of a performance-based test method for quantification of cracking potential in asphalt pavement materials

With the increasing use of recycled materials in the construction of roadways, it is more critical now than ever to understand the impact that these materials have on pavement behavior and performance. Since recycled materials tend to, in general, behave in a more brittle fashion, a primary area of concern is increased cracking potential. There is a need for a performance-based approach to quantifying the cracking potential of asphalt mixtures, specifically those with high amounts of recycled content. This study aimed to first, characterize the impact of using various proportions of recycled materials in asphalt mixtures, and second, develop a testing protocol to quantify their cracking potential in a way that is scientifically meaningful and economically practical, while ensuring correlation to independent testing. A characterization of varying amounts of recycled content displayed a general trend of increased susceptibility to cracking as recycled content increased. It was determined that low-temperature testing was not capable of sufficiently distinguishing between these various materials. A practical test method, the Illinois Flexibility Index Test (I-FIT), was developed, and found to appropriately distinguish between variations in mix design and characteristics. The I-FIT method is a modification of the semicircle bending beam (SCB) test; the modification includes the testing temperature, the loading rate, and the analysis of test data to calculate a developed parameter titled the Flexibility Index