Can anyone tell me the best method to remove one section of concrete
from a sidewalk? I have one row of 4' x 4' of concrete blocks and one
is pretty bad. I thought of patching it, but I'd rather just remove it
and repour that section. I rented a cut-off saw, but I couldn't get
the damn thing started and was so mad that I took it back the next day
for a refund. Now I am wondering if I could buy masonary blades and
use them on an old circular saw and use that, but they are only 7"
blades (depth of cut is 2 3/8"). At that depth the cut wouldn't go all
the way throught the 4" slab. Could I cut the 2 3/8" and then just use
a sledge and hope the break happens along the control joints? Is there
another method?

I've broken up concrete before with a sledge and pick-axe, but I am
afraid of trying to remove this middle section because I don't want to
repair more than just one section if I don't have to.

The cut-off saw cost me $89 ($50 for the saw and the rest for two
throwaway blades). And I'm guessing that a contractor would charge me
$300, plus they remove/recyle the concrete.

Any ideas would be appreciated.