Aluminum / Concrete Embedment 3

[jimrcasper]

Is it possible to embed Aluminum in concrete without spalling the concrete? Do all Aluminum alloy react the same? Does anyone know of a good reference? I have not been able to find much on this topic.

 

[UcfSE]

Aluminum needs to be coated with something to prevent it from corroding in the concrete, such as an asphaltic coating.

 

[SlideRuleEra]

jimrcasper - Go to my web site, at the link below, and download "Nonferrous Metals In Contact With Concrete" from the out-of-print Portland Cement Association page.

Best Wishes

http://www.SlideRuleEra.net

 

[henri2]

As pointed out by UcFSE it has to be effectively coated.

ACI 318 Section 6.3.2 including the commentary deals with provisions for aluminum conduits and pipes.

 

[doclou]

Is a conversion coating such as Alodine an effective coating for aluminum to be embedded in concrete/grout?

 

[Ron]

doclou....No. Generally conversion coatings are not sufficient to prevent aluminum-concrete reactions. As others noted, the aluminum must be isolated, proferably by a heavy body coating such as asphaltic based coatings; however, good quality clear urethane works well.

 

[JAE]

Ron,
(or anyone else)

Say you have a client who wants an aluminum guardrail (post and horizontals) instead of a galvanized steel system.

The architects don't want all that "ugly" base plate & anchor bolt stuff where you might be able to use SS bolts with a neoprene pad under the plate to separate from the concrete.

So would an installation using PVC sleeves in the concrete, with the aluminum posts set into it and filled with some sort of epoxy work? Not necessarily epoxy grout - but would that work?

 

[Dinosaur]

Fire the architect. Or better yet, embed him in the concrete.

 

[doclou]

Thanks Ron,
The reason I ask is that I have recently seen aluminum curtainwall anchors set into recesed pour stops along the edge of the poured concrete floor slab. The contractor was then coming back and filling the pour stop flush to the floor slab with grout to accomidate interior flooring. The aluminum anchors were about 1/2" thick extruded with a conversion coating for finishing.
It's currently not in my scope of work but raised my curiosity when I saw it so I'm doing a little research so I can comment on it intelligently.

 

[Ron]

JAE...I'm recommending the use of epoxy grouts for aluminum handrail posts. I've seen too many of them corrode right at the interface with the concrete and corrosion product testing shows compounds associated with cement-aluminum interaction. Another common problem is the compromise of the waterproofing system when the post holes are cut after the surfacing and waterproofing are in place. The epoxy has a better chance of sealing back against the waterproofing than conventional grouts.

I wouldn't leave a PVC sleeve in place unless it had some type of anchoring knobs or similar to get bond to the concrete and to the grout. PVC is prone to shrinkage for the long term and the bond will break, loosening the handrail.

 

[JAE]

So the epoxy grout itself does not react with the aluminum?

 

[Ron]

No. About the only issue that develops is if the epoxy surface is not finished correctly and it still traps water at the aluminum interface....long term that will corrode, just takes longer than with concrete since there are fewer chemical reactions to happen.