I have a back porch that is 8"x10'x40' one slab no joints that is also the roof of my basement pantry.
It doesn't get wet very often but I was pressure washing it yesterday and there was a small puddle in the basement pantry.
Of course a slab that big has cracks in it. It has rebar so the cracks are tight.

I don't think silicon caulk would seal it well, the crack is just to tight to get something that thick in it.
I could run a bead then try and trowel it into the crack with a putty knife but I think something thinner would work better.
I just don't have a clue.
Also it is my porch so it gets walked on every day.