Question about aluminium and concrete

[Lee]

I have a question, have been googling for a little while with no real success.....
Why is it you are advised to not use quick set concrete with aluminium products?? It is on the bags of concrete, and also strongly signed on the pole of my aluminium letterbox....

[DaveO (David)]

Lee

Try this link. Interesting!

[jjjnettie (Jeanette)]

The lime would corrode the aluminimum I would think.

[leon]

JJ is pretty right the materials in the cement would eventually corrode the aluminimum.

Cheers leon

[Lee]

I figured it was something to do with corrosion.... chlorides in the quick set stuff by the sounds.... thanks for the link - this place is a great think tank!

[Harb]

Another reason is some quick set concrete's can generate enought heat in the chemical heating process to melt aluminuim parts such as thin walled tubing etc

[h0ughy (David)]

all to do with the galvanic couple set up by the PH of the concrete and the annodic action of the aluminium in that environment, so like the info given above.

[Dennis]

Originally Posted by h0ughy

all to do with the galvanic couple set up by the PH of the concrete and the annodic action of the aluminium in that environment, so like the info given above.

I am in awe...

[xelasnave]

He is not just another pretty face it seems .
If you want a nice little "experiment" try a caustic soda solution on some alluminium. Apparently the only chemical reaction that "speeds up"..
The bubbles are hydrogen and the reaction is such that one can easily fill a ballon with hydrogen from a beer bottle containing the reaction. Tie off the ballon when filled and trim off the excess "rubber" and you have a ballon that goes up into the wide blue (er grey at the moment folks) above. Now for a little more fun tie a strip of paper to the ballon light it and let it go.. your own private super nova.
alex

[xelasnave]

Does not really explode as the ballon contains mainly hydrogen... mmm there is another experiment where you fill a tin with H with a hole in the top and a hole in the bottom of the tin.. light the top hole and stand back as the chamber mixes air with the hydrogen.. bang.
I tries lighting the bottle once having placed a cork and a jet in the openning..dam there was air in the bottle..bang. My parents took my chemistry set away for a while after that... as they did when I busted a ballon filled with ammonia gas in the house one day.
alex

[h0ughy (David)]

Originally Posted by Dennis

I am in awe...

Sir Dennis do I detect an overtone of labelling me thick!! If so its well directed.

An interesting byproduct of remembering a project I had, which was to redirect drainage from a cliff top to a secured location over the cliff edge over an addit, the design involved reducing the weight over the cliff and because it is in a marine environment we looked at the effects of salt and other chemical toxic environs, worked out that the aluminum had to have maximun coatings and that would give it a life of over 100 years using helcor 300 diameter aluminum pipe, which we had specifically made for the job. Even isolated with neoprene the 316 grade stainless steel pipe brackets with neoprene.

after all that there was a rock fall off the cliff 5 years later then Council spent 3 million removing material and regrading the cliff edge - the pipe was destroyed in that move!