# Concrete roadbed: adjusting grade?



## Skeeterweazel (Feb 11, 2014)

Guys, i thought i was being slick in doing my layout this way- using bricks/blocks to support beams. Beams are OK. Wasn't too hard to make them. Some aren't flat, but i think i can adjust w/ ballast.

Problem is getting the beams at the right height. I'm somewhat confident i'm getting the right grade (3%) using regular levels w/ shims on one end and i made a water level. The bitch is getting the blocks at the right height. I guestimate height before putting the beam in place, but it still takes numerous attempts to get it acceptable. I figured once it's set it shouldn't move, but that may not be true. Using dirt and sand under blocks. Maybe i should dig down a bit and use gravel under blocks?

The PVC ladder idea didn't appeal to me, but now i'm kinda thinking about it. My way was relatively cheap, but labor intensive. I found some concrete shim/wedges online that i may try to fine tune the height.

Anybody out there w/ any bright ideas? Do i just need to be patient and do what i'm doing?
Thx.
Marty


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## Garratt (Sep 15, 2012)

You could put some wooden stakes adjacent to the beams that have all been marked level as reference then a measurement from there for the grade according to track distance and line the top of the beams to that rather than setting each beam with a level. You could use thin shims of some material under the beams to adjust. Making flat beams then grading them will actually tilt the track sideways a little unless there is some ballast under the track to get it true again. A constructed ladder system won't have that problem.
I would put crushed rock with fines under each block. Dirt and sand is unstable and will likely sink.

Andrew


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## BigRedOne (Dec 13, 2012)

Do you intend to make a raised track from concrete, or will you ultimately use fill such that concrete is merely a roadbed?

If going for a raised track, I think you need your support posts to have a solid footing down to the frost line in your area. From that point upward, wood (and plastic "wood") seem to be the popular method. Reinventing the wheel.

If going for a concrete roadbed, then I think fill dirt first, tamped down, then place the concrete on those (or use forms and pour in place.)


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## chuck n (Jan 2, 2008)

Where do you live? If you have significant frost, blocks sitting on the ground without a good foundation will all rise and fall differently, come spring thaw. I think that a ladder or trench with ballast would be a better choice. 

Chuck


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## Skeeterweazel (Feb 11, 2014)

Thx guys. I live in So Cal, so hardly any frost.
Plan to back-fill after roadbed is up.


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## BigRedOne (Dec 13, 2012)

I think you'd be best served by placing the fill first, for a consistent foundation, then tamp down where you'll build roadbed, then make the roadbed.

Don't use posts unless you're raising the railway.


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## Skeeterweazel (Feb 11, 2014)

BRO: elevation will vary from 0 to 18", 3% grade.
Thx.


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## wigginsn (Jan 9, 2008)

Hi Skeeter,

I've thought about using the same system for my next railway - concrete beams on block risers, with infill later, plus a version of CliffyJ's mountains above.

I'd certainly put a good foundation of crushed rock under the blocks as others have mentioned. Tamped crusher dust as a top layer would make the final adjustments a bit easier to my thinking. Like you mention - cheap & stable if no frost involved, plus I get to prefab each beam to my needs.

Regarding levels my thoughts were to set a site datum point then reference the height of each riser from that with a water level. Same as you really so I'd be keen to know why its harder than you thought.

If the blocks are fixed height, then it should be easy to work backwards to set the foundation final level?

This is similar to the roadbed construction method used for the Southern Cross Railway in England (ie its been done and proven), I've got the book somewhere but it got filed in a box after we moved..

Cheers
Neil


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## Skeeterweazel (Feb 11, 2014)

Neil, just seems to take so much time to get it right. Set riser height by digging down, adding sand. Place beam in correct position. Check "level". Sounds easy. But trying to get within 1/16" or so, so if off have to take it down and adjust all risers for the beam. Water level more difficult to use than i thought. Have to be real careful not to knock it over. Temperature change effect tubing: as gets warmer tubing expands and changes "level", so have to keep rechecking. Need to try gravel/fines.
Thx.


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## SD90WLMT (Feb 16, 2010)

Your trying to "level" your precast cement roadbed...

Dig ...in a variable base soil...and backfill...which causes settling. ..

Just a guess here...but are your precast sections all the same thickness..?

I ask...this can become an "un-seen" variable...and confound the process for you...

Second thought....find a workable solution to adjusting the level...just below the precast piece...not at ground line...say like set the bases a bit low...set the precast on top....shim with a hard item - think rocks, come in all sizes...to set your grade elevation of desire..and work mortar mix under the surface...or place it first ...using the small hard spacers to maintain your work..while the mortar cures and hardens...not settling under the weight...

Using long thin wood wedges might be a source of shim control your looking for...add mortar mix to fill the void..pull or break off shims when set and dry...

Find easy ways to get the job done..that are effective....

Good luck...keep trying...your building a RR!! Have Fun !!

Dirk


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## CliffyJ (Apr 29, 2009)

Marty, 
Are you pre-casting your own sections? If so, nice castings! 

You know this I'm sure, but a curve on a grade is a helix. So a flat arc trying to fill the role of a helix section is geometrically tough. Even if shimmed and anchored well, the joint transitions will not be perfectly smooth. The ladder method tends to smooth everything out, permitting natural helixes, semi-automatically.

Best regards,
===>Cliffy


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## wigginsn (Jan 9, 2008)

Thats a gd point Dirk,

Maybe use 2 wedges under one end of the beam to set height (grade) & side level, then fix with mortar.

I haven't used a water level yet but have been told to use a clear 'reservoir' at 1 end to cater for those small changes - don't know how effective this is tho.

Cheers
Neil


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## SD90WLMT (Feb 16, 2010)

I very much agree that lifting solid curved sections is a goofy geometery issue...

If on a level grade ...no problem...
But after introducing a climbing grade...twisting enters the picture...
...and those thick n heavy concrete pieces will not twist or bend to conform..
The longer the individual pieces ..the greater the issue becomes..

I originally left this aspect off my discussion due to using typical roadbed base material to "float" the track on...which over comes a lot ..

Thanks Neil, 

Dirk


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## Skeeterweazel (Feb 11, 2014)

Thx guys.
Cliff: my buddy and i made a straight and curve form to make beams. Curves are almost a 1/4 turn. That length creates weird geometry like you guys have said, so i'm seeing how they do cut in half.
Mortar shrinkage is minimal if used under beam? I like that idea. Small issue being w/ small footprint supports (i.e. brinks) doesn't give much room for mortar.
Thx again for your pointers.
Marty

edit: Neil, i saw a YouTube vid of guy that made a water level w/ a jug on one end. I'll have to look into that more to see if that would work better.


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## Skeeterweazel (Feb 11, 2014)

Hijack: here's vid of fancy water level. Wouldn't having reservoir help reduce volume changes caused by expanding tubing? Hmmmm.


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## CliffyJ (Apr 29, 2009)

For my water level, my reservoir is an old 30 gal plastic trash can. Hole drilled near the bottom, clear tube stuffed in, never leaks. The tube is about 50' long, so that gives a good range. To calibrate, I fill the can until the level at the end of the tube matches a known elevation datum. 

Main problem is forgetting to dump it, because the mosquitoes love it!


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## John J (Dec 29, 2007)

I would suggest that you get one of the calculating levels at Sears. I found a 8 ft level in the trash at a construction site. . All the bubbles were broken. I put my 18 in Sears Calculating level on it when I want to do a long stretch. The level is well worth the expense. 

JJ


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## John J (Dec 29, 2007)

When I need shims to adjust height I use Washers. The size of dimes, quarters, and half dollars. I have had a difference in height from a bridge to a abutment. I made up the space using washers. I use them once to create super elevation. Ummmm That didn't work out like I expected. 

JJ


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## benshell (Oct 1, 2008)

Skeeterweazel, I would definitely set your piers in concrete, and just get it close, erring on the side of too low since it's easier to add than remove. In several places I've used cement blocks to build up roadbed, and filled the cores, but I've found the result is never as perfect as I'd like it to be. Now I'm of the opinion that a concrete roadbed should be roughed in without worrying about details like a bump here and there, or super elevation. When it's all set, just skim coat the top with mortar or stucco. And if there's a high spot, shave it off with diamond cup wheel on an angle grinder. I also don't have to worry about frost. I'm sure I wouldn't be able to do things the same way in many parts of the world.


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## Skeeterweazel (Feb 11, 2014)

Thx. guys. All good pointers.


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## FlagstaffLGB (Jul 15, 2012)

I actually like your "precast" concrete approach. I assume that you are including some small rebar (say #3R) in the bottom of the forms? Just as a thought to alter your design a bit and maybe solve your leveling problem; why not design the cross-section of your concrete beams as an inverted "C" channel? Then you could fill the area with decomposed granite or other small stone (which would look more like ballast anyway) and then you don't worry so must about leveling. The granite sub-base could be leveled as you set the track. Your design may have to include some anchor points to hold the track in place once you have it in the right place. Anyway, just another thought. I do like your basic idea.


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## Greg Elmassian (Jan 3, 2008)

I live in So. Cal also. Are you doing this so you can raise the track above the surrounding grades?

Greg


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## SD90WLMT (Feb 16, 2010)

On a personal note....I'm not sure I'd like hefting precast pieces around..

....on any given day....I move enough heavy stuff around to build a layout!!

Dirk - DMS Ry.


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## Skeeterweazel (Feb 11, 2014)

Have 2 3/8 rebar in beams. 
majority of track will be off the ground at 3% grade.
beams roughly 65#. Cutting curves in half so i can support them at a more even grade rather than leaving them as-is, e.g. 1/4 of a circle.
Marty


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## FlagstaffLGB (Jul 15, 2012)

Marty, just another thought...since once you place all these concrete forms in place, you probably aren't going to move them again, you might want to try a casting method used by Palo Soleri (Italian Architect) here in Arizona. He would build his forms out of dirt (clay mixed in) to a "reverse" of what he was constructing. So you could build earth mounds for the diameter that you wanted, depress the area for the concrete beams and vertical upright supports....add the steel and then pour the base. Once it had cured, the dirt can be removed from below and you would have perfectly formed elevated concrete supports. Could be interesting, but it would be labor intensive...but then what isn't these days.?


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## Skeeterweazel (Feb 11, 2014)

yeah, trying to avoid that. maybe in the long run it would save time.
thx


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