Electrical Ductbank Concrete (*red dog*) 2

[TBellP47]

Can someone verify that when electrical duct banks are poured in place, is the concrete normally used a light-weight or lean concrete (1000 psi) mixture with a red dye additive in some cases (referred to as *red dog* when it's in place)?
Is *lean concrete* appropriate per code or otherwise?
Thanks!

(NOTE: The red dye is added to make apparent and *warn* of its presence when digging occurs and the ductback is accidently struck. In my area, it's commonly called *red dog*)

 

[JedClampett]

In our area, lean concrete is made with small amounts of cement and sometimes some fly ash. It tests out at about 100 to 300 psi. I don't think if if you hit it with a backhoe it would provide that much resistance.
We use a 2500 psi mix with about 4 to 5 sacks of cement per cu yd. I think it's pretty standard.
You'll not find any guidance in the ACI code for this. Maybe in some electrical code, but I doubt it.

 

[TBellP47]

Thanks Jed.
Most *red dog* I'm familiar with *doesn't* provide much resistance. Its real purpose is to serve as a warning and to stabalize buried conduit runs. In most cases, prior to a dig, a warning is posted on the design drawing(s): [highlight]*Caution!! Hand dig only!! Buried electrical cables are known to exist in the area.[/highlight], etc. etc..
I, too, don't know of any ACI code that covers this aspect of concrete. Not sure about NEC.
Thanks again!

 

[JedClampett]

You're right. If you've encased the conduits with 4000, 2500 or 100 psi red concrete and someone still rips them up, who are they going to be mad at? The guy who used lower grade concrete?
It's one of those times when you try to idiot-proof something and someone comes up with a bigger idiot.

 

[TBellP47]

Exactly!

 

[concretemasonry]

For what is worth, even some electrical contractors on individual residential projects lay red patio stones (2x8x16") over buried lines as a warning to those following later.

If you ever specify anything, specify red iron oxide as a PIGMENT. Other "dyes" are not really permanent in concrete.