DEVELOPMENT OF SUSTAINABLE ASPHALT MIXES BY INCORPORATING CRUMB RUBBER IN HIGH-MODULUS ASPHALT CONCRETE (HMAC) MIXTURES IN LOUISIANA

Asphalt concrete mixtures are primarily designed using the Superpave mix design procedure where the proportioning of asphalt mix components is based on volumetric properties. Efforts are now being made to develop performance-based sustainable asphalt mixes. In this regard, a French asphalt mix design known as “High Modulus Asphalt Concrete (HMAC)” meets certain performance-based specifications including workability, stiffness, rutting, and fatigue behavior. HMAC uses a hard asphalt binder with a high asphalt binder content (about 6%) and low air void content in comparison to the Superpave mixes. This study prepared HMAC mixes using crumb rubber and local materials available in Louisiana. Five HMAC mixes were prepared using PG 76- 22 and PG 67-22 with 10% and 20% crumb rubber content. Additionally, a Superpave control mix was prepared from PG 76-22. RAP content was fixed at 20% in all mixes. Compaction curves were prepared from Superpave gyratory compactor results. Semi-Circular Bending (SCB) and Dynamic Modulus tests were conducted to determine the cracking resistance and stiffness of the mixes. The results indicated that HMAC mixes prepared with PG 76-22 and 20% crumb rubber successfully met the French HMAC mix design and Louisiana DOT specifications.