Development of rail pads from recycled polymers for ballasted railway tracks

• Rail eco-pads made from recycled polymers were designed. • Waste plastics and end-of-life tyres were combined to modify pad stiffness. • The influence of pad geometry on its stiffness was determined. • The carbon footprint of the designs was determined. • Recycled high density polyethylene-based pads were found to be the most durable. • The net and gross carbon footprints of the pads were explored. This article focuses on the study and design of rail pads from recycled plastics for their application in railway tracks, aiming to reduce environmental impacts produced from virgin materials. For this purpose, sustainable rail pads were designed and manufactured using two separate locally recycled plastics: high-density polyethylene from plastic boxes, and from a combination of polypropylene and low-density polyethylene from reclaimed geomembranes. A high-performance polymeric industrial resin was also used as a reference material. These separate plastics were also combined with different quantities and sizes of recycled crumb rubber from end-of-life tires. The results of this paper analyse the influence of pad composition and geometry on the mechanical performance of the pads, while also assessing the durability and environmental benefits of the most optimal solutions. Results found that the pads from high-density polyethylene presented values of static stiffness around 800 kN/mm while the low-density polyethylene led to values close to 150 kN/mm, where the reference industrial binder outputted intermediate values. In addition, the combination of different quantities and sizes of crumb rubber resulted in a range of viable solutions, in some cases reducing stiffness more than 50%. Additionally, both recycled plastics offered a reduced carbon footprint compared to conventional pads, although this did decrease with increasing amounts of crumb rubber. Nonetheless, it was found that the softer solutions led to higher plastic deformations during fatigue tests, reducing the durability in comparison to the pads made from high-density polyethylene.