Large Scale Central

New idea, maybe, modular concrete

Track and Trestles
#1

I got to looking at the cover of the new Garden Railways magazine and notice that the bridge on Rupert James’s railroad looks like cast concrete. This got me thinking about the use of concrete in our roadbeds.

Would it be advantageous to use precast concrete sections instead of casting the roadbed in place. I was thinking that you could control the casting better and it would save time in setting up the forms. Plus you could cast inside a shed or something and then place later. This would allow you to continue making roadbed even in the winter.

My idea would be making 3-4 ft sections depending on the weight of the finished cast. Cast lips in each end so you have something to connect the sections together. You could also cast in connecting points into the cement that allow you to connect the track to the roadbed. Then I would make a roadbed of base course. Tamp and level it and then place the concrete on that. I would glue the sections of concrete together with a concrete glue or paver glue. Or perhaps a silicon glue that would allow a small amount of flexure.

Anyways, just thinking out loud and wondering if it would work or not, your thoughts???

#2

Seems to me that the whole idea behind conrete roadbeds is to avoid frost heave and make your roadbed easier to maintain… Casting 2 or 3 foot sections, would eliminate the contrinous flow of roadbed, allowing for it to heave… People that I know who do cconrete roadbed also use rebar in the roadbed to help stiffen the concrete…

#3

I agree frost heave would be a problem with shorter pieces of concrete.
I use patio blocks as bases for buildings and under all my switches and over time the ground does settle and I have had to readjust the blocks.
The idea of the concrete roadbed is the strength of it and the fact it won’t move.
I think pre casting 3-4 foot sections then putting them down might work depending on where you live. Casting them to interlock is a good idea but overal alot of work. It might be better just to do it in place.

Todd

#4

I’ve done some concrete roadbed, and I’ve done some precast block walls, Digging and pouring results in a more level structure with a lot less work than digging, filling with stone and tamping before setting blocks.

The advantage, like Andy says, of concrete is that it does not move if you make it thick enough (5-7") and reinforce it. I use stainless fencing for reinforcement in small pours and rebar in larger ones. I can point you to some photos of past projects if you are interested.

#5

I don’t understand…frost heave is frost heave …unless your below the frost line it’s gonna heave if the earth decides to period whether you see it with the eye or not.

#6

Son, for once, you are right… (Jon says so)… However, a frost heave is much easier to fix/level with a floating ballast, than with a concrete roadbed… In my opinion… :slight_smile:

#7

Dave, of course you are right. In my area we need to go down 42" to be safe - BUT a long 6-8" thick piece of concrete rarely moves here during a typical winter. I’ve had sections down for 5 years that hardly have a crack in them and as far as the eye can see have not moved.

My buried ladder roadbed does push up some each winter, but is easily pushed back down in early spring.

My biggest problem is where I transition from track imbedded in concrete (Walk Crossing) to floating track. The floating track always pushes up creating a vertical curve at the joint. I need to remove the floating track every few years and cut down the ballast to get it back level with the imbedded track.

#8

I agree with all the frost heave issues. However, don’t you get some cracking in the continuous concrete roadbed? And I think you try to combat this by adding the rebar, but don’t you still get the cracking?

If you have, what I would call an expansion joint, the movement could be controlled to the joints. Also, some of that paver glue is pretty strong. I built a retaining wall with it. I messed up a part and had to tear it out…well the glue was so strong I ended up breaking the pavers to get them apart. That’s some pretty strong stuff in my book.

Keep in mind I’m kind of thinking out loud and just exploring other alternatives to what we do normally. Also, I don’t have a lot of experience with concrete because I use the ladder method, but I do have experience in concrete from a construction stand point.

#9

My mistake was to drive rebar in the ground before poured concrete, big mistake, frost heave cracked the concrete, still don’t know why I did that, looked good at the time, otherwise the lengths of concrete I poured with out that never cracked, just floated along top. All frost heave is based on moisture in ground, lots of moisture, lots of heave. Had the concrete down for 5 years never a problem, and then when I tore layout out all I did was borrow concrete saw, cut up sections and hauled them out with a 2 wheel cart.

Tom h

#10

The guys in Canada build with frost heave in mind and build unattached to the ground on the surface and it all floats together. Not much on ballast, but it runs good. I’ve watched it for 9 years and it stays pretty good with little maintenance.

#11

What guys in Canada?

#12

Tom I made the same mistake with a bridge abutment. Worse, I drove the rebar into the root of a growing tree. Didn’t take long for things to move!

#13

I would bet your idea could work if the underneath was prepared right. I believe the whole heave thing is due to water being trapped. So if you laid your precast on top of a stone bed that the water could escape from, it would help. Maybe treating the precast like pavers with paver base??

The only other thing I could add would be to pour posts down below the frost line that the precast would rest on top of. That would help stabilize it? Not sure if they would be connected somehow with bolts to limit movement?
I guess pouring in place has it’s merits.

A big problem I see in G gauge is that what works for some, doesn’t work everywhere. They don’t get deep frost in the southeast for example, but the sun is murder.

#14

David Russell said:

What guys in Canada?

Fred Mills, Doug Matheson, David McCurdy and the Ironwood, Peter’s Pond and Western guys, plus others.

#15

Like others said frost heave is worst where you have moisture in the ground. If the water drains well you wont have frost heave issues. I have great drainage on my layout with almost no frost heave. If I were to build my railroad on the back end of my property, I would get major frost heave. I have seen it heave almost a foot. Large rocks get lifted like it was nothing That areas is also like a sponge.

#16

Did you get all your repair work done Dave?

#17

I say give it a try. Concrete is cheap, a bit labor intensive, but cheap. Make a section and see how it holds up. They always say there’s a fine line between genius and insanity. But, then again, who are they?

Terry

#18

Well, I might someday when I expand the railroad. Mine is all built on Ladder. I was just thinking out loud and wondering if some have tried it or would have better experience than I and would know if it would work.

#19

But then again the prototypical track bed seems to work. :wink: