I have an old chicken coop. most of the building was build on a hill that was cut flat for a slab on grade. the west corner was filled because the hill slopes off to the west. the floor crakced and settled on the west end because the earth was not compacted. I broke out the old concrete and poured new to that my floor was flat again. Now when it rains the old concrete is very damp. The new concrete is bone dry. There is a distinct line between the cold joint. Does anybody know why this is?