The utilization of recycled thermoplastic composites for civil and military load bearing applications

Long-term performance and extended service life are issues of vital importance to the Department of Defense (DoD). The DoD seeks alternative construction materials to replace more traditional materials, such as wood and steel, for heavily loaded infrastructure to combat this expensive corrosion and bio-degradation problem. Recently, two military bridge installations were completed, composed entirely of a reinforced thermoplastic composite lumber (RTCL) material that is capable of supporting the load of an M1 Abrams tank at approximately 64,410 kg (71 tons). The RTCL material selected for these applications is polypropylene (PP) coated fiberglass blended with high-density polyethylene (HDPE). Advantages of using RTCL include the following qualities: corrosion, insect, and rot resistance; no toxic chemical treatments required to increase service life; environmentally friendly; diversion of waste plastics from landfills; reduction of deforestation, green house gases, and global warming. RTCL has many advantages but does behave differently than traditional materials and certain properties must be addressed during the design stage. Both bridges are continually monitored, have performed well over the first year and a half, and are more cost-effective than any other construction material. Details of the material, design considerations, and construction are reviewed.