How fast does concrete break down? (in gabion cages)

Factual Questions
1

Last October I made thread asking for options on a retaining wall about 65 feet long and 4 foot tall: http://boards.straightdope.com/sdmb/showthread.php?p=18818855#post18818855 , and I have another question. I was going to put this as a post in the old thread, but then I thought it was different enough from the original question.

We have a rubble pile from a concrete sidewalk that we replaced. If we do use the gabion cages, is concrete suitable to use as fill (keep the natural stone on the face, and the concrete chunks hidden behind)? I was thinking it would be good, but my dad thinks the concrete would break down too fast. But from Googling it I see that people do use it. But I also see that people make there own cages out of chicken wire. So I was wondering what the folks here think on the matter.

And if anyone has another ideas, I’d love to there them.
Thanks.

2

Was the sidewalk concrete breaking down before you removed it? If the concrete was mixed improperly it could be weak, but properly mixed concrete shouldn’t degrade in any reasonable amount of time. The concrete in the Pantheon is over 2000 years old and it’s still in good shape. Especially when it’s semi-protected by being piled in a gabion. According to Wikipedia, “The life expectancy of gabions depends on the lifespan of the wire, not on the contents of the basket.”

–Mark