embedded conduit in concrete

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larrycad

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I am having a discussion with a customer regarding proper installation technique for RMC in concrete. He contends that the red concrete not only enclose the horizontal underground conduits, but also the stubups. His contention is that any dirt that comes in contact with the RMC will rust is out and the concrete is there to protect the conduit from rust. I would be interested in hearing from anyone with opinions on this, but would really appreciate any technical information on the specific subject.
 
344.10(B)
(B) Corrosion Environments RMC, elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition.
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Corrosion protection would be required for concrete as well as dirt.

Now, considering it is galvanized, the corrosion protection is already taken care of in either situation.

Roger
 
Red concrete is just that- colored red and is normally required to indicate concrete encased services. It has nothing to do with anti-corrosion properties (if that's what he is saying).

That said, if the soil is continually moist or saturated even RMC will fail eventually even if encased in concrete. You could coat the RMC with an epoxy or bituminous coating after you fabricate it. Best way is to use RNC or use a PVC coated RMC like Robroy.

-Hal
 
hbiss said:
That said, if the soil is continually moist or saturated even RMC will fail eventually even if encased in concrete. You could coat the RMC with an epoxy or bituminous coating after you fabricate it. Best way is to use RNC or use a PVC coated RMC like Robroy.

-Hal
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I agree with Hal.

Even though RMC is galvanized, it won't last forever whereas PVC will get close.

I hate Robroy so I won't go there.

Roger
 
peteo said:
Not sure I understand the issue here. In any case, this document should provide some guidance. The linked web site has several documents if more research is needed.
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Actually, two issues:

1. do stub ups require concrete encasing?
2. does concrete provide better corrosion protection than dirt?

Perhaps a better question would be, is there any requirement or justification for concrete around the stubups.
 
roger said:
I hate Robroy so I won't go there.

Roger
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:lol:

We are again in absolute agreement.

The last time I used it the customer was specifying jacket colors and explosion proof fittings.

Luckily all that lead time gives you the time to get the dies you will need. :roll:
 
larrycad said:
peteo said:
Not sure I understand the issue here. In any case, this document should provide some guidance. The linked web site has several documents if more research is needed.
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Actually, two issues:

1. do stub ups require concrete encasing?
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No

2. does concrete provide better corrosion protection than dirt?
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No again,


I have been involved with a good number of renovations where what had once been RMC raceways were just hollow voids with a brown crust lining them.

Perhaps a better question would be, is there any requirement or justification for concrete around the stubups.
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No again.

Roger
 
Hello Bob.

iwire said:
roger said:
I hate Robroy so I won't go there.

Roger
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:lol:

We are again in absolute agreement.

The last time I used it the customer was specifying jacket colors and explosion proof fittings.
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That's one I haven't run into yet, whew. :lol:

Luckily all that lead time gives you the time to get the dies you will need. :roll:
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And that's one (not all though :wink: ) of the biggest reasons I hate it so much.

Roger
 
Hardworkingstiff, most of these renovations I am recalling were buildings from the 50's and 60's, and were RMC.

Don't interpret it as though I meant all were gone, but there were a good number in these buildings that were just remnants of a raceway.

PVC on the other hand would have still been intact.

PVC encased in concrete is every bit as good of an installation (better IMO) as RMC, IMC, EMT, or any metallic installation.

Roger
 
There is a galvanic type reaction that occurs when conduit is in contact with both soil and concrete. In this area if you make an installation like that the conduit will be gone at the soil concrete joint in a few years. The following is from the UL Guide Information for Rigid Metal Conduit.
Wherever ferrous metal conduit runs directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.
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