2006-10-13 16:13:41 · 7 answers · asked by Old man wrench 4 in Science & Mathematics ➔ Engineering
A answers about vapor barrier are correct, but a word of caution. There should be a two or three inch layer of dry sand on top of the moisture barrier to provide a place for any water from the curing process to excape the concrete. Otherwise this water can try to come up through the concrete as it is setting and cause problems. If you are pouring a very dry mix with air entrainment, this is less of a problem.
2006-10-14 03:49:54 · answer #1 · answered by oil field trash 7 · 0⤊ 0⤋
This is not normally done, but depending on where it is, this might be to act as a vapor barrier. Concrete is porous, and water will soak through it. If the area is damp or this slab will be an interior floor or wall, putting plastic under of behind it will act as a barrier to keep dampness from seeping through.
2006-10-13 23:19:58 · answer #2 · answered by Kokopelli 7 · 1⤊ 0⤋
cement in concrete has its own setting time. the origin setting time is around 1 hour. so if the operating time is too long the concrete or cement setting took place and its plastic abality is lower than normal.
2006-10-14 01:04:13 · answer #3 · answered by Anonymous · 0⤊ 0⤋
It is a moisture barrier. Concrete is porous.
2006-10-14 00:24:12 · answer #4 · answered by Stewart H 4 · 0⤊ 0⤋
keep condensation out
2006-10-13 23:23:26 · answer #5 · answered by T C 2 · 0⤊ 0⤋
it is to prevent water from the soil or walls from seeping inside the structure they are costructing.
2006-10-13 23:20:49 · answer #6 · answered by marikit _ako 2 · 1⤊ 0⤋
Too stop any plants or weeds growing.
2006-10-13 23:21:04 · answer #7 · answered by Anonymous · 0⤊ 0⤋