I'm looking for informed comment and/or advice on a plan to repair
cracks in my 1-1/2" thick gypsum-based (gypcrete) floor.

Problem:
The floor is broken up into fairly large sections that are separated
by hairline cracks. When I walk on a section, it moves just a tiny
bit, causing its edges to rub against adjacent sections. This results
in annoying crunching and crackling sounds.

Objective:
I want to eliminate the crunching/crackling sounds without the big
expense and hassle of pouring a new gypcrete floor.

Assumption:
A series of cement "plugs" along the crackline would provide the
rigidity needed to prevent the sections from moving and rubbing
against each other when stepped on.

Plan:
1. Drill 5/8" holes every foot or so into the cracks along the
crackline (ie. not across them). The holes would be drilled at an
angle of 30 degrees. The angle would alternate -- drill one hole at
30 degrees in one direction and drill the next hole at 30 degrees in
the opposite direction.
2. After the holes are drilled, push a layer of thin plastic film into
the holes to line them. The liner would keep the existing gypcrete
separate from the new cement. The gypcrete and cement must be kept
separate because the moisture from the new cement will break down the
gypcrete and these materials are chemically incompatible with each
other.
3. Squeeze quick-setting cement tightly into the holes and stay off
floor until cement hardens.

Considerations:
Since the gypcrete is meant to prevent a fire from burning through the
floor into the wood structure below, the "plug" material must be
fireproof and have roughly the same heat-transference properties as
gypcrete.
Cement is used instead of gypcrete as a repair material because it's
considerably more resistant to shear stresses than gypcrete.

Thanks in advance for all helpful replies.

Darro

Greetings,

Don't laugh, but you may be able to screw down the gypcrete to keep it
from moving with large backerboard screws. This will be a lot quicker.

Hope this helps,
William