ABSTRACT
The Illinois Flexibility Index Test, or I-FIT, was developed specifically to analyze the flexibility and cracking potential of asphalt mixtures. The introduction of recycled materials, such as Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS), has increased mixture brittleness to unacceptable levels, leading to increased cracking. The I-FIT method is ideal for identifying potentially brittle mixes and analyzing acceptable flexibility in recycled mixes.
The results from mixes with varying levels of RAP and RAS content is presented in this paper. Materials with low recycled content often have Flexibility Index (FI) values above 10, while mixes with high recycled content and proven high cracking potential often haveFI values below 4. The I-FIT method combined with the Hamburg Wheel Tracking (HWT) test, which quantifies rutting potential, can ensure a balanced mix design, which will resist both rutting and cracking failure.
