Bob Roberts wrote:So I am watching contractors build the ARRA funded Piedmont Improvement Project (double tracking Charlotte to Greensboro) and noticed that they are using wooden ties for the new tracks. I am not surprised (I know they are cheap), but it made me wonder about the cost difference between wooden and concrete ties, how long each lasted and if the weight of freight makes concrete a poor choice?
Are concrete ties used any any heavy / non-transit projects?
It depends. Railroads in the northeast have had a lot of problems with concrete ties because of the freeze-thaw cycle making them prematurely decay. If they aren't water-tight, a little seep and a few winters where the temperature crosses above/below freezing twice a day every day makes them bust up in no time...whereas porous wood can flex and bend. That can be a problem in poor drainage spots. Sort of the same reason why you don't see too many all-concrete grade crossings in the northeast while those do tend to be the dominant kind anywhere warm (or anywhere the winters are so cold it's below freezing all day instead of straddling the freezing mark). Not so much that concrete is inherently bad, but that you have to take extra steps to make sure the batch is good and isn't going to have prematurely shortened lifespan. Otherwise you get a situation where X% of the concrete ties from good batches last for all their rated lifetimes but that Y% minority from a bad batch all start failing en mass in 5 years. Whereas the odd bad new wood tie will fail sooner than expected but it doesn't show across an entire batch installation like it does with concrete. Quality control and superior supply chain matter the world for concrete ties, especially for railroads in the "freeze-thaw" belt. Metro North, the MBTA, and Amtrak were all very badly burned by poor quality control on batches they ordered from defunct concrete tie maker Rocla, and had to do very expensive replacements of brand-new installations. They're all gun-shy about using concrete going forward. And in their cases their traffic levels in the northeast are so punishing and their contracts for replacement ties so large that they can economically make it work better standardized on wood rather than risk a whole-batch failure. That's what those agencies' service scale buys them, and changing to a different type is costlier than staying with what they know.
There's no right or wrong answer, even when weather is less than cooperative. NJ Transit has done a lot of concrete installations and seems to have had good luck. Some freights have done it too, although their traffic levels compared to commuter traffic levels makes wood easier for fewer/further-between MoW crews to handle on spot replacements. Their MoW needs are not the same as Amtrak's, which is only going to work on a stretch of NEC track with a really big-staffed crew and as much automated machinery as they can get because their priority is to finish as fast as possible in short-burst track outages vs. a freight main where one ragtag track gang may have to cover couple dozen miles per day dodging trains every few hours instead of every 5 minutes. Totally different needs, totally different solutions for those needs.