Use of Polymer Fiber to Improve Mechanical Properties of HMA Containing Recycled Asphalt Shingles (RAS)

A significant percentage of highways and roads in California are constructed using Hot Mix Asphalt (HMA). As the state’s infrastructure ages, maintaining and rehabilitating these roads has become increasingly critical. Recycling aggregates and other highway construction materials offers substantial economic, environmental, and engineering benefits.

Reclaimed Asphalt Shingles (RAS) present an excellent alternative to virgin materials, as they reduce the demand for virgin aggregate, minimize construction waste sent to landfills, and conserve nonrenewable natural resources. Additionally, incorporating RAS into roadway construction can yield energy savings by reducing the processing and transportation requirements associated with virgin aggregate materials.

However, the performance of HMA containing RAS depends on the percentage of RAS incorporated into the mix. Due to their thermoplastic properties, processed plastics can serve as beneficial modifiers for HMA, provided they are compatible with the asphalt matrix. While RAS increases stiffness, it can also reduce cracking resistance. To address this issue, incorporating polymer fibers has emerged as a potential solution to balance strength and flexibility, thereby improving the mechanical properties of HMA.

The inclusion of polymer fibers in asphalt mixtures enhances resistance to permanent deformation and increases mechanical strength at elevated temperatures. Therefore, in this project, we will conduct a laboratory investigation on the use of polymer fibers to enhance the properties of HMA containing RAS, and examine the effects of fiber addition on HMA with high RAS content.