Development and Implementation of Recycled Thermoplastic RR Ties

Abstract

About a billion wood cross-ties are in service in North America for safe and effective transfer of heavy freight or high-speed passenger train loads. These wood ties are facing long-term safety and serviceability issues related to ever increasing intensities and frequencies, and harsh field conditions. In addition to other applications, the Constructed Facilities Center, West Virginia University (CFC-WVU) has been investigating the use of recycled polymer composite railroad (RR) ties with discarded wood or rubber core to safely alleviate many of the problems posed by creosote treated timber ties. In this research, mechanical property characterization of recycled thermoplastics was carried out prior to manufacturing RR ties with continuous glass fiber reinforced (GFRP) polymer composite shell with recycled polymer, and wood/FRP (fiber reinforced polymer) core. GFRP Composite ties manufactured with thermoplastics and continuous glass fiber/fabric have exhibited high strength/stiffness unlike plastic ties with chopped fibers. Local cracking from spikes was found to be negligible. Half- and full-scale RR ties were subjected to static loads of 80 kips and fatigue loads up to 12.5 million cycles with a strain range of 750 micro strains (με, i.e., 750×10−6) in FRP composite shell. Spike pull-out tests were conducted on full-scale RR tie specimens. Results showed high strength/stiffness of these ties under static loads and also excellent strength retention under millions of fatigue cycles. Field installed ties exhibited maximum strain of 1070 micro-strains under actual locomotive loads moving at 15 mph.