According to Edwin Pawlowski :

"HeyBub" wrote in message

I suppose it could happen, but I've seen cars on cinder blocks, in
someone's front yard, for DECADES and the blocks haven't crumbled yet.

Probably will sit many more decades. OTOH, a block that was sledged out of
a wall may not be quite as strong or can have stress cracks in it. I'd not
trust my life to it.

Depends on the circumstances.

Up here, a cinder block that hasn't been "filled" with concrete
partially embedded in moist dirt won't last through more than
one or two freeze-thaw cycles. Of the 9 cinderblocks under the
14'x14' shed we renovated (including raising the whole thing 8"
to put another support beam under it), 4 of the 9 cinder blocks
had disintegrated.

Secondly, I watched an electrician "drill" a 2" conduit hole
through a new cinder block wall with only a 2lb hand sledge ...

Surprisingly neat hole too.

Cinder blocks aren't very durable. They shatter easy. Not
a good thing to stick under a car, unless you're not terribly
concerned it might fall down.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.