for about 20yrs our garage door would not keep the rain water from seeping in, the cement contractor did not angle the lip downwards to keep the water out. so one year i finally got some mason cement and made a sloped lip downwards to where the garage door came down.
it is not 100% reliable if we get a really heavy driving wind (the garage door faces the west so that is the place we do most likely get winds from as they come whipping up the driveway) some water may still come through but at least it is rarely enough to worry about.
after the cement was cured i got some good garage floor paint and put several coats over it. so far it has held up ok.
oh, yes, the current version is the third attempt. the first one was a small ridge which was just not enough to keep much of anything out. the 2nd attempt did not stick to the slab even with my cleaning, grinding and other prep, the last attempt i mixed some kind of flexible binder in with the cement.