In alt.home.repair, on Fri, 14 Oct 2016 20:03:33 -0400, Mike Duffy
wrote:

On Fri, 14 Oct 2016 12:03:32 -0400, micky wrote:

[...] a ball of cement almost 3 feet in diameter

If you're not in a hurry, repeated applications of vinegar should soften
it.

I thought maybe you were kidding, but I see that works.

Of course, I think in this case it might take 100 years, so maybe you
were kidding after all.

But it's good to know for other times.