An expanding number of products are demonstrating the real-world feasibility of incorporating post-consumer polyethylene (PE) into asphalt paving for roadways and parking lots. The set of demonstration projects — part of the New End-Market Opportunities (NEMO) program, under the auspices of the Plastics Industry Association (Washington, D.C.; www.plasticsindustry.org)— are intended to investigate the benefits of such applications.
In one approach, known as the wet method, recycled plastic is added into the asphalt binder as polymer modifier or asphalt replacement. This requires mechanical mixing and, in some cases, additional compatibilizers to achieve and maintain a homogeneous modified binder blend, according to the National Center for Asphalt Technology (NCAT) at Auburn University (www.eng.auburn.edu), which has collaborated on several of the projects. In another technique, known as the dry method, recycled plastic is incorporated as a solid additive during the manufacturing of the asphalt mixture.
A recent demonstration occurred at the Chevron Phillips Chemical (The Woodlands, Texas; www.cpchem.com) site in Port Arthur, Texas, where a 67,000-ft2 lot was paved using asphalt into which 191,000 recycled polyethylene bags were blended.
Last year, similar projects were undertaken by Lyondell Basell at its Cincinnati Technology Center and by grocery retailer Meijer in a collaboration with Dow Chemical. Also, Shell Polymers collaborated with Green Mantra on paving with PE-containing asphalt at its new ethane cracking facility in Potter Township, Pa.
According to Andy Brewer, associate director of sustainability and materials at the Plastics Industry Association, the finished asphalt material shows greater strength and stiffening impact, providing better rutting resistance than conventional asphalt when tested on paved surfaces.