Field Demo of Waste Plastic, Crumb Rubber & Plastic-Rubber Hybrid Additives in Kansas City, Missouri

Abstract: The construction industry is responsible for 38% of global carbon emissions, making it a significant contributor to greenhouse gases. In August 2024, the U.S. Environmental Protection Agency (EPA) introduced a Label Program to identify and facilitate the procurement of low embodied carbon construction materials, prioritizing asphalt, concrete, steel, and glass. Although asphalt is one of the most recycled materials in the U.S., there is still potential to reduce its embodied carbon footprint. Post-consumer recycled polymers, such as ground tire rubber and waste plastics, have been studied to lower the carbon footprint of asphalt mixtures while also improving performance. Missouri has initiated several demonstration projects to explore the use of these materials on highways. This case study focuses on one of the first uses of recycled polymers in a residential street with low-volume traffic in Kansas City, Missouri.
The field demonstration was conducted using three mixture modifiers incorporated via the dry process: Low Density Polyethylene (LDPE or PE), Engineered Crumb Rubber (ECR), and End-of-Life Tire Compound (ELTC) which is a mixture of devulcanized rubber and waste plastic. The construction took place on October 3rd and 4th, 2024, with each modified section covering approximately 0.2 miles. A control section without modifiers was also included. All mixtures adhered to APWA Type 5 specifications, with key volumetric requirements being a maximum of 98% Gmm at Nmax, 90.5% at Ninitial, 3-5% air voids (AV) with Ninitial of 6, Ndesign of 50, and Nmax of 75, 65-75% voids filled with asphalt (VFA), and a minimum of 14% voids in the mineral aggregate (VMA). Each mixture contained 30% recycled asphalt pavement (RAP) and 0.75% of an anti-stripping agent (LOF65) by weight of virgin binder.
Balanced Mix Design (BMD) tests, including the IDEAL-CT, Hamburg Wheel Tracking Test (HWTT), and IDEAL Rutting Test (IDEAL-RT) were performed. HWTT results were reported for 20,000 passes at 50°C. The control mixture had a baseline rut depth of 16.2 mm at 20,000 passes, with a CT-Index of 55.5 and an RT-Index of 65.7. The addition of PE and ECR significantly reduced rutting, with depths of 4.1 mm and 3.9 mm, respectively. ELTC slightly increased rutting to 18.3 mm. At 10,000 passes, the PE, ECR, and ELTC mixtures showed rut depths of 3.2 mm, 3.0 mm, and 5.0 mm, respectively. In terms of cracking, PE and ELTC improved the CT-Index to 56.2 and 65.8, while ECR decreased it to 40.8. RT-Index values for PE and ELTC were 82.7 and 65.8, while ECR result is still being analyzed.
The average field density was 97.2% of Gmm, indicating excellent compaction across all sections. BMD test results for plant-produced mixes, along with RT and Disc Shaped Compact Tension Test (DC(T)) outcomes, are still being analyzed. Additionally, a life cycle assessment (LCA) will be conducted to quantify the environmental impacts of these post-consumer additives in asphalt and will be included in this study.

Keywords: Waste Plastics, Ground Tire Rubber, Field Demonstration, Balanced Mix Design, Low Volume Roads