More than likely it's the rebar. Moisture loaded with dissolved salt penetrates the tie, the salt rusts the rebar, the rebar expands from the corrosion and there goes the concrete tie.
jeffhergert Firelock76 From what I've read in "Trains" and other sources the jury still seems to be out on concrete ties. They're a lot more expensive than wood ties and promise an extremely long service life, but there have been a lot of concrete tie failures. I guess it depends on the application. Concrete ties for light rail useage seems to be OK, it's the heavy main-line useage that seems to have the problems. No shortage of wood for ties however, there still seems to be plenty ro go around. A few years ago, the UP couldn't buy enough wood ties for their needs. At least that was what was being said then. It may have been a temporary problem. Something caused by some other problem, such as environmental concerns over the wood preservative used for ties, etc. I don't really remember all the details. It also was during the time of a big concrete tie push. So maybe they were trying to justify all the concrete ties they were installing. Ever since they installed them, we see a concrete tie gang every couple of years replacing the broken ones. Funny how it seems it's usually the same spots that have the rash of broken ties. Jeff
Firelock76 From what I've read in "Trains" and other sources the jury still seems to be out on concrete ties. They're a lot more expensive than wood ties and promise an extremely long service life, but there have been a lot of concrete tie failures. I guess it depends on the application. Concrete ties for light rail useage seems to be OK, it's the heavy main-line useage that seems to have the problems. No shortage of wood for ties however, there still seems to be plenty ro go around.
From what I've read in "Trains" and other sources the jury still seems to be out on concrete ties. They're a lot more expensive than wood ties and promise an extremely long service life, but there have been a lot of concrete tie failures.
I guess it depends on the application. Concrete ties for light rail useage seems to be OK, it's the heavy main-line useage that seems to have the problems.
No shortage of wood for ties however, there still seems to be plenty ro go around.
A few years ago, the UP couldn't buy enough wood ties for their needs. At least that was what was being said then. It may have been a temporary problem. Something caused by some other problem, such as environmental concerns over the wood preservative used for ties, etc. I don't really remember all the details.
It also was during the time of a big concrete tie push. So maybe they were trying to justify all the concrete ties they were installing. Ever since they installed them, we see a concrete tie gang every couple of years replacing the broken ones. Funny how it seems it's usually the same spots that have the rash of broken ties.
Jeff
Sounds similar to CN's early experiences with concrete ties; there is still a section of track east of Hinton, AB where the ballast looks like wet concrete has been poured on it as a result of tie disintegration (still a popular story to tell new hires). Today CN still buys and installs large numbers of wood ties all over the place, including on 70 MPH mainline track. Concrete ties are used more in curves because they are stronger laterally than wooden ties.
One other downside of concrete ties is that they are attacked and corroded by road salt (maybe just the rebar?). Because of this Edmonton Transit has continued to use standard wood ties at level crossings on our LRT system.
Greetings from Alberta
-an Articulate Malcontent
doctorwayneThis coal train is on a 9 mile extension of the Kiski Junction Railroad, completed in 2011. It's on welded rail on steel ties and, like the rest of the KJRR, is on a former PRR right-of-way.
If I remember correctly, there was a state grant for $4 million in 2008 to help build this. How much did the whole 9 miles cost? Remarkably inexpensive for such high capacity even if laid over a good remaining grade...
This coal train is on a 9 mile extension of the Kiski Junction Railroad, completed in 2011. It's on welded rail on steel ties and, like the rest of the KJRR, is on a former PRR right-of-way.
Unfortunately, coal traffic ceased earlier this year, as did steel traffic on the opposite end of the line.
Wayne
wjstixFor a while in the 1940's or 50's the Missabe Road (owned by US Steel) tested out some sections of mainline track laid on steel ties. Apparently worked OK but wasn't an improvement over wood, and didn't catch on.
Are you sure this isn't the experimentation shortly after the turn of the 20th Century, with Carnegie M-21 section ties?
Willard's Maintenance of Way and Structures has what I consider a very good discussion of the various early steel tie systems. See this Google Books link which will let readers in the United States download a PDF copy.
And more than likely wasn't worth the added expense.
For a while in the 1940's or 50's the Missabe Road (owned by US Steel) tested out some sections of mainline track laid on steel ties. Apparently worked OK but wasn't an improvement over wood, and didn't catch on.
Firelock76Now we're back to square one with concrete, basically artificial stone. Interesting.
I kept trying to post on this and the interface kept changing the page and wiping the input out as I edited.
The key thing that makes concrete ties possible is the introduction of elastomer under the rail and the provision of some sort of elastic clamp system (like Pandrol) to hold the rail down. Without that, the shocks involved both break the ties and cause increased wear. Earlier designs also fostered much greater noise and reflected shock into the primary and secondary suspensions of the trains.
I have a still-vivid recollection of an early Northeast Corridor use of concrete ties - I actually thought for a few seconds we had a derailed axle, as the sudden noise and vibration characteristics were so great, and the sound and 'feel' so unlike anything I'd expect high-speed compliance to feel like.
We have, of course, progressed substantially in a wide range of developments since that time. Something that remains problematic, though, is what happens to concrete ties following derailments. A conventional wood tie experiences some flange cutting, which does not substantially impair its abilities both in absorbing shock and preserving geometry. A concrete tie either fractures or suffers likely damage that makes it imprudent to keep it in service. This is one of the arguments favoring the usual types of composite ties.
I worry the recycled-rubber ties will go much the way of recycled-rubber pavement (a good-sounding idea that did not survive the first rainstorm), albeit for different technical reasons. Look at the experience with the elastomer seals in the 'alternative' class 9 track structure tested at Pueblo, and consider what methods would be used to hold the rails to the composite tie.
There is another type of tie coming on the market, one that uses recycled rubber. The goal is to combine the advantages of both concrete and wood into one long-lasting tie.
It's interesting that the recent experiences with concrete ties almost, not quite, but almost mirror what happened in railroadings infancy.
The original bases for rails were cut stone blocks, but it was found that wooden ties gave a much better ride, were a lot easier on the rolling stock, and most importantly were a lot cheaper than using stone, so stone went away in spite of it's theoretical superiority.
Now we're back to square one with concrete, basically artificial stone. Interesting.
Firelock76I guess it depends on the application. Concrete ties for light rail useage seems to be OK, it's the heavy main-line useage that seems to have the problems.
Both the heaviest and fastest main-line usage demands better-determined track structure. Note in particular what is required for AREMA Class 9 track.
I suppose it is possible to implement top-down rail alignment with wood ties, but you would need much more equipment, of a very specialized type, to do it, and I wouldn't expect the precise alignment to hold up without very frequent (and equally specialized!) maintenance attention.
Some of the traditional problems with concrete ties, notably those involving interaction with crushed-stone ballast, are exacerbated under high speed and high load. A conventional wood tie allows ballast 'points' to penetrate and lock in, which increases both the area for load transfer and the relative resistance to lateral shift. I don't know of a commercially-successful approach to concrete tie production that allows this in the 'necessary' manner; a problem I remember from 'an earlier life' was that the ties grinding against the ballast would produce extensive fines that would clog drainage and cause other problems including abrasive dust.
There are some interesting track systems 'out there' now, including LR55 and the African 'tubular track', that some forum readers might find interesting.
After reading the discussion about wood fuel for locomotives I thought, what about wood for cross ties? Railroads needed a source for those as well. But my question is: Why and when did concrete cross ties come into play? My earliest recolection was in the 1970s. Are they more cost effective? Do they require periodic replacement as wooden ties do?
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