On 3/17/2016 10:12 AM, Bod wrote:
On 17/03/2016 17:03, Don Y wrote:
On 3/17/2016 7:20 AM, HerHusband wrote:
I have a very thin hairline crack in my conrete slab, right in the middle
of the garage doorway. It is barely visible and is so thin I can't even
feel it with my fingers. Unfortunately, water still finds it's way
into the
crack on the outside of the garage door and seeps along the crack to the
inside of the garage. So, I would like to seal up the crack before it
turns
into a bigger issue.

Any recommendations?

Most crack sealers seem to be made for larger cracks, so I'm not sure
they
would even get down into my hairline crack.

Is water getting *into* the crack or simply clinging to it as a "guide"
to flow into the garage?

I.e., are you sure the crack is the cause and not just a *symptom*
(of a low spot in the floor)?

As a first attempt, I'd try some silicone caulk applied with a trowel
(or float). This will tell you if the crack *is* the "low spot"
vs. just RESIDING in a low spot.

Once you know what the case is, you can peel the silicone off (or, scrub it
off with a wire brush) -- it won't last applied as thinly as your
description
suggests it would be.

But, based on what this discloses, you might then be able to try an
epoxy intended for use with concrete/cement applied using the same sort of
technique. Make a serious effort to clean up the crack and surrounding
areas before trying to apply it.

I would chisel along the crack and make a V shaped channel, then wet it and
sand and cement it.

It's a "very thin hairline crack", "barely visible" and "so thin I can't even
feel it with my fingers". No need to make a *bigger* problem out of it!

The crack may not *be* the problem but, rather, just a convenient place
for water to adhere as it migrates inward. It could be a low spot
in the slab (there is *some* reason for the crack being there!).

Instead of weakening that area (chiseling it out) and then trying to
back fill, just try something that "flows well" (or, can be FORCED to
"flow well") that also ADHERES well (cuz you won't have much
"material" being added to that area if it is really as insignificant
as Anthony's description suggests.

(A really loose slurry of mortar and water would "flake off" after
drying)