Want to create a six to twelve inch wide porous concrete strip about thirty feet long in our backyard over a drain pipe. Normal concrete is porous but the concrete i want is extremely porous. So porous in fact that you could pour a 5 gallon bucket of water on it and it goes directly thru the concrete. Extremely porous concrete is not as strong especially for heavy vehicles, but i will not have vehicles and the strip would be no more than a foot wide. Is there a name for this type of concrete?
Why? We have 3 "shower" drains six inches in diameter to drain a concrete backyard. The problem is the drains clog easily with leaves and other natural debris blown around in a storm. A downpour may leave inches of standing water in our backyard. A strip of concrete should not clog.
There already is a pipe that drains the water away, but that would need to be a half pipe, right? How would you form the porous concrete so that it drains into the half-pipe? Is there a recommended impervious underlayment for the porous concrete that would direct water into the drain pipe?
Best Answer
There is a concrete that I have used, and it is regular concrete, and perhaps it can have gravel in it, but the type I have installed did not use any gravel/aggregate. Dry pack is what I have learned to know it by, and stone setters use it for building walls and laying flagstone sidewalks. I have used it for shower bases over PVC liner and coated it with Redguard for waterproofing. That is where I learned that it took on water real fast. I was to dampen the dry pack slab I set 2 days before. What water I poured on to move around just fell into the concrete, did not stand at all. I even had a decent troweled surface.
The mix is the same, just add enough water to get the concrete to form a ball when compressed in your hand, and I mean just enough, too much will screw it up.
This may be worth a shot, but be careful, this may clog too from atmospheric dirt, decayed debris settling in etc.
The pipe since it is covered with concrete can be black corrugated drain tile or perforated sch 35 set in a gravel bed. Holes in the pipe are slits in the black drain tile and gravel size will not matter. In the Sch 35 the holes are larger so you do not want to use a small gravel there, #57 crushed stone or something larger than 3/4" washed gravel depending on your area. You may want to consider using a different type of area drain. The way you describe "shower drain", sound like it get clogged pretty easily. Replacing the drain you have with something that has a much larger grate or trap included that allows debris to collect, but not clog, may do you well too.