# CONCRETE ROADBED QUESTION



## mgilger (Feb 22, 2008)

Is rebar needed when putting down concrete roadbed? If so, what are people using for the regar material?

Thanks,
Mark
*http://mmg-garden-rr.webs.com*


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## Greg Elmassian (Jan 3, 2008)

concrete is great in compression, but very weak in tension, that's why all concrete of any size needs metal or fiber spanning it inside... you could also probably use wire mesh, but I would defer to the people who have tried it. A long thin piece of concrete can easily crack and come apart. 

Greg


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## Madstang (Jan 4, 2008)

I havent layed as much as some people but I have layed some down in my layout. Yes we do use rebar 1/2". You can buy it at Menards in I think 8' pieces. Tie the end of one to the end of the other with wire ties. They should also be next to the rebar.

Like Greg says it will break, crack if you don't use it. It will give the concrete stability when it heaves a little...if it does. Any way you will need to use it for the stability factor. I have never used wire mesh.

When you want to change the layout the concrete is easily broken up with a sledge hammer. If you lay some iniitally, then add more at a different time you can use a masonary bit the size of the rebar..drilling with a hammer drill far enough into the concrete that is already there, fitting the new rebar far enough into the older cement so if your ground heaves it will heave as one unit and not crack apart. OR worse yet 1 section will stay put and the other will heave upward causeing a step and possible damaging your track..if you don't tie the 2 together.

Also after you lay it and it settles as it does in my wetter area, I use forms again to get the top surface level and then instead of concrete I use the thinner masonary mix that has no stones in it and spread it on the surface of the concrete that is already there and relevel it. 

Don't know if I said too much but hope this helps...kind of fun pouring concrete..

Bubba


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## jake3404 (Dec 3, 2010)

Couple things... 

What bubba said about attaching one pour to the next is mostly correct. You need some sort of "glue" in the hole that you insert the new rebar into the old piece of concrete to keep the new pour from pulling away from the old pour and forming a gap. Most would use a grout mix of some kind. 

As far as a wire mesh. It is less rigid so be more subjective to heave. However its advantage is it keep the entire matrix together better. If you have some torsional forces (Twisting) the rebar wont be able to keep the concrete together. The wire mesh will. 

Best case is to use both. Put a piece of rebar then a wire mesh on top of it. If you even wire tie the mesh to the rebar then its even better. 

Make sure you dont let the rebar set on the ground. It will rust and cause your concrete to break up. Most use little wire stands that keep the rebar an inch or so off the ground. Others will lay the bar on the ground then start pouring and then go back and lift the rebar up to get it off the ground.


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## NTCGRR (Jan 2, 2008)

personally 3/8" rebar bends easy to install, we are usually talking only a 3" wide X 2" deep ribbon, which 3/8" is fine. 
I've lifted 15ft sections and moved them to other places because I'm cheep. 
again this is one you can over think. 
I started using 3/8 rebar , two bags concrete mix and 1 bag motar mix for strength. gets about 25 to 30 ft strips. about 13 years ago and 4 layouts ago.


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## Greg Elmassian (Jan 3, 2008)

Just to underscore what Marty already said, whatever reinforcing materials you use, make sure they are in the middle of the pour, otherwise they do not do as good a job of strengthening the concrete. 

Midway is probably the best compromise for a single layer of reinforcement. 

Regards, Greg


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## John J (Dec 29, 2007)

I use 3/8ths too. 

I also have gone dumpster diving on construction sites.

I have found scrap R bar in them.

JJ


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## jjwtrainman (Mar 11, 2011)

If your track isn't funning on a patio, I would recommend using an idea i hatched when cleaning somebody's house today, they said they had "composite siding" its not vinyl but rather cement and paper material. it is stiff and would be excellent for use under track.


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## Torby (Jan 2, 2008)

And in a few hundred years, an archaeologist will get his PHD writing a paper about the cultic significance of Marty's railroads.


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## CliffyJ (Apr 29, 2009)

In case you've not seen it yet, here's a recent thread on concrete roadbed that touched on your question and related issues. Lotsa great pics, comments and links.

http://www.mylargescale.com/Community/Forums/tabid/56/aff/9/aft/118874/afv/topic/Default.aspx


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## pimanjc (Jan 2, 2008)

I use 3/8 rebar and the same mix that Marty uses. When making a pour, I am sure to leave about 8in of exposed rebar at the end to tie into the next pour. 
JimC.


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