Strange question perhaps, but I'm currently renovating our concrete stairs at home. With this comes a consideration.
I understand that concrete is damaged when water seeps into cracks and then freezes. But if you have a concrete surface where all cracks are repaired, but the surface itself might not be completely flat (small "depressions" here and there), does it risk the same problem in winter? During rain, about 5 mm of water might gather in these depressions or hollows in the concrete. If it then freezes, what happens to this water? Will it just expand upwards, or is there the same risk of frost damage as with cracks?
I understand that concrete is damaged when water seeps into cracks and then freezes. But if you have a concrete surface where all cracks are repaired, but the surface itself might not be completely flat (small "depressions" here and there), does it risk the same problem in winter? During rain, about 5 mm of water might gather in these depressions or hollows in the concrete. If it then freezes, what happens to this water? Will it just expand upwards, or is there the same risk of frost damage as with cracks?
The idea is possibly to lay decking on top. Then I won't be able to see what's happening with the concrete underneath, hence my concern about the potential risk of frost damage. But with a smooth surface, the water expands (when it freezes) upwards and sideways so to speak, not down towards the concrete?
The water expands in all directions, but if there's resistance in one direction, it stops there if it's free in all other directions. In a crack, however, there's resistance in two opposing directions or more, and since it's not free for the water to expand, the crack is forced apart instead.
Imagine inflating a balloon lying flat on the ground compared to one that's wedged between a couple of boards.
Imagine inflating a balloon lying flat on the ground compared to one that's wedged between a couple of boards.
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