Darro wrote:
I'd appreciate informed opinions on the idea of using plywood sheeting
to stabilize the fractured concrete floor in my apartment.

My apartment has a subfloor of 5/8" plywood overlaid with 1-1/2" of
gypsum concrete (gypcrete). The gypcrete has lots of cracks which move
and rub against each other, creating annoying crunching sounds when I
walk on the floor. To eliminate the movement of the gypcrete pieces,
I'm thinking of glueing sheets of 3/8" plywood with "No More Nails" to
the floor.

I figure that the plywood will bind the gypcrete pieces, and that 3/8"
plywood will be rigid enough to help reduce shear stresses on the
glue, be flexible enough to conform to a floor that isn't perfectly
flat and be thin enough to minimize the increase in height of the
floor.

Any comments or suggestions?

Thanks in advance,
Darro

I think think your proposed repair MIGHT work but IMO it will be a lot
of work.

Even a 3/8" floor thickness will require finish features to be
modified.

take a look at the follwoing for ideas about DIY solutions
http://www.ultraquietfloors.com/gypcrete_repair.asp

I assume the high traffic areas are the ones with the most compromised
gypcrete.

IMO a liquid consolidation material (epoxy or urethane) is what will
work best for you. Maybe you can try a small area & see if it works.

Water based materials will be more environmentally friendly (no fumes
for you) but traditional "solvent" based epoxies are (IMO) stronger &
more durable.

cheers
Bob