It's just aesthetic (and a little practical), but I want to fill the
gaps in my driveway. They had felt, once upon a time, but as it
stands, the joints between the concrete slabs are slowly getting deeper
as rain washes through them. They collect leaves and other trash and
are a pain to keep clean. Can I just get new felt and jam it in there?
I know not to put in anything rigid, but the drones at Lowes & HD seem
to feel that it is impossible to put in a joint after the concrete is
poured. True?