# Question on large cast in place concrete arches



## SE18 (Feb 21, 2008)

I'm going to be building a large concrete aquaduct that will be pretty massive as it will hold a canal and a railroad track. It's too big to build upsidedown and then move to the site and it's too big to build next to the site and then push upright, as there are some delicate plants nearby and some structural problems, so I'm going to cast it in place. Has anyone built a cast-in-place concrete arch bridge that has pictures to show? Even if it's not an aquaduct, it probably will have applications to my project.


I've got some ideas, but would like to first see what others have done to get even more ideas. I'm thinking large wood and styrofoam form. 


Also, I was just curious, if my aquaduct with track will be a first in garden RR model history. There are a couple prototype examples.


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## toddalin (Jan 4, 2008)

I do this using the basic shape made from styrofoam. I then use a mesh strainer to sprinkle DryLock hydraulic cement over the styrofoam over a cement mixing tub. (A very clean method of applying this stuff.) You can push extra powered cement into the cracks and crannies prior to the "major sprinkle" to fill in areas and smooth your work. I then mist it with a spray bottle until it staturates. Several layers can be built up like this without waiting between layers. (Watch for my article on this technique in _Garden_ _Railways Magazine_ to come out ???)

You would be far from the first to have an aquaduct.


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## SE18 (Feb 21, 2008)

oh, so instead of pouring the entire mold, you make both sides first and then backfill. 

any photos?


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## toddalin (Jan 4, 2008)

Posted By SE18 on 28 Jul 2010 11:15 AM 
oh, so instead of pouring the entire mold, you make both sides first and then backfill. 

any photos? 
No. I make the _entire structure_ out of styrofoam then apply the hydraulic cement as a "surface coating." Just keep turning it to do the various sides after the prior side dries.

The bridge that the train just came from (upper right corner) was done using this method as was the ramp on the left side of the third link (and featured in the GR article).

Hydraulic cement coated bridge

Another view 

Hydraulic cement coated ramp


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## SE18 (Feb 21, 2008)

oh, I see. I'm going to be sitting on and walking on mine. It will need to be hard-scaped. But thanks.


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## Biblegrove RR (Jan 4, 2008)

SE, (sorry I can't find your real name) have you started or completed this project? I too want to build a 40' x 2' high CURVED Viaduct. any info will help!


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## Totalwrecker (Feb 26, 2009)

We're hoping for better luck with the new one....


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## ohioriverrailway (Jan 2, 2008)

John -- I did a realtively short curved cast concrete viaduct a few years ago. Worked out pretty well. Details are at www.orery.com. You can email me if youu have any questions.


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## Biblegrove RR (Jan 4, 2008)

can't find www.orery.com


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## Biblegrove RR (Jan 4, 2008)

ok, found the site but see no pics


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## Nutz-n-Bolts (Aug 12, 2010)

T.W., That is a great picture! That would be a viaduct scene should be modeled on someones railroad. Any takers?


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