On Fri, 11 May 2007 21:46:21 GMT, "dadiOH"
wrote:

Exploding concrete isn't the problem with the powder ones. True, a
smallish area may chip off at the point of impact but that doesn't
effect the holding power.

The problem is that they come in different loads and you have to know
the concrete density to select the proper load...too weak and they
won't go in all the way and you'll have to hammer in manually; too
strong and they may well go clean through the plywood. Even if you
know the concrete density you'll probably find areas that are harder
or softer.

I've used lots of Hilti (and generic copy) 22 ca. nails, and find that
testing easily determines the proper force load. A few may still
screw up, but you'll be in the ballpark.

The real issue I've seen is concrete that's too fresh and concrete
with too much aggregate. The fresh stuff falls apart, and the
aggregate is rocks! G