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I have seen extremely porous concrete that water drains through very well. Narrow strips of this may be put across a driveway to limit excess water runoff. What is the name of extremely porous concrete? How does one make it? Where would one buy it?

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It appears as if you meant to edit the question you asked, but instead asked the question again. If this was the case, could you please delete one of the questions (or flag it for moderator attention, and they can delete it for you). Thanks. –  Tester101 Jul 5 at 12:11

3 Answers 3

It goes by many different commercial names, but the generic terms is "Permious" or "Pervious" concrete.

http://en.wikipedia.org/wiki/Pervious_concrete

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Dry pack it what I learned to call it. It is a regular mix of concrete, but it has just enough water added to it to get the concrete to "kick". This amount of water is so small, it is just enough to get the concrete to hold together when compressed in you hand with a strong squeeze.

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I don't mean to whine but drypack IS a very porous concrete that allows water to readily run through. If you have mixed it and it hasn't then you did not do it properly... –  Jack Aug 5 at 3:31

"no fines concrete", eg no sand is not used when making the concrete.

No-Fines Concrete is a method of producing light concrete by omitting the fines from conventional concrete. No-fines concrete as the term implies, is a kind of concrete from which the fine aggregate fraction has been omitted. This concrete is made up of only coarse aggregate, cement and water. Very often only single sized coarse aggregate, of size passing through 20 mm retained on 10 mm is used. No-fines concrete is becoming popular because of some of the advantages it possesses over the conventional concrete.

Quoted from NO-FINES CONCRETE & ITS MIX PROPORTION in theconstructor.org

enter image description here

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From what I read, this is a very weak mix. –  Jack Aug 5 at 3:32
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@Jack, Compared to what? It is a lot more stable then gravel, clearly you would not use it for the floors in the towerblock, but it is good be drainable footpaths, or behind retaining walls. –  Walker Aug 5 at 7:39
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Doesn't need to be compared to anything. When it is used in a shower pan the water readily flows through it. The water does not stand at all. The dry pack shower bases I have done require wetting, after it has set up, it just runs right through. Still really porous. The guy was asking for what types of concrete are really porous, this is the one I knew of. Not high tech but old school, strong and porous. –  Jack Aug 6 at 3:21

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