A Mixture of High Density Polyethylene (HDPE) and styrene is used to make railroad ties. HDPE is a very common plastic and used to make milk jugs and plastic toys. Styrene is also very common and used to make Styrofoam coffee cups and meat trays. A railroad tie is molded by mixing the two. According to Trish Thiel of American Recycler, the ties are made completely out of recycled milk jugs and foam products. The ties are comparable in strength and weight to wood ties.
A composite is a combination, or blend, of plastics. In 2011, the Performance Rail Tie Company (PRT) is manufacturing ties out a proprietary plastic composite material. The company states the ties weigh 230 lbs. each, and are cheaper than wood. Furthermore, PRT states the ties are more stable than wood. The ties measure 7-inches-by-9 1/4-inches-by-108-inches.
Concrete is a very common building material. It is used to make roads, driveways and bridges. In 2011, the Rocla Company is making railroad ties out of concrete. The company states concrete is stronger and more reliable than wood. Several types of ties are made, such as for light people movers or for heavy freight rail usage. The ties have embedded steel clips to secure the rail, so no drilling is needed.
The Axion Company developed a Recycled Structural Composite (RSC) material. Unlike new composites, these are made entirely from recycled plastics. The proprietary material is made form several different types of plastics, formulated to simulate the structural characteristics of wood. Compositology LLC cited the "Business Wire" when it reported that in February of 2011, Axion was awarded a $15 million contract for its railroad ties.