Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
(OP)
It is proposed to remove an area (about 10 feet x 35 feet plan area) of loose wet sand under an old existing 5" thick slab on grade floor of a below grade parking garage. The clay tile weepers run through this area so will replace a 35 foot length, the existing wet sand removed to a depth of 3 feet and replaced with 0.7 MPa controlled density cementitious fill to about 2" below the invert of the new weeper and then a CSA concrete sand placed to about 3" below the slab on grade, than a new slab on grade place. The traditional way of laying clay tile weepers is to leave 1/4" wide open joints between each tile (and that is how the old weepers here were laid in 1957).
QUESTION:
If we place a filter fabric around each open joint between clay weeper tiles, is there any danger that the new CSA concrete sand will clog the filter fabric? Since the CSA concrete sand has no fines, it is thought that the filter fabric will not be clogged by it, but just looking here for a confirmation.






RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
With a coarse graded concrete sand very little sand is lost into the pipe, due to bridging the slots by the coarser parts. If you are worried about that, these pipes also come with a filter sock over the pipe. This kind of drain pipe saves a lot of labor time and is pretty fool-proof.
Any danger of clogging is pretty well avoided if the fill itself is a good filter (which concrete sand is).
Why dig out 3 feet anyway?
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
I would not use individual clay drain tiles. They are serviceable; however, they are labor intensive to install, tough to maintain a slope line and relatively expensive as compared to PVC or ABS.
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
To Ron - yes, as you suggest rigid PVC with holes and sock is likely what we will use, as that is what I see generally used in this area. Thanks. Much appreciated.
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
If you wish to check out the filtering capability ASTM C-33 fine aggregate (concrete sand) the US Corps of Engineers published information on its use about 1937 from its Vicksburg, MS labs. It is a good all-purpose filter for most soil types.
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
Can the controlled density cementitious fill come right to the bottom of the weeper, or should there be a few inches of CSA concrete sand under the bottom of the weeper?
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
Right. I will add that to the drawing. Is it ok to bring the concrete sand to the underside of the perforated pipe, or shuld there be a few inches of the concrete sand below the pipe?
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
In my case the material immediately below the pipe will be a very low strength concrete (about 100 psi) that will be placed for about 2 feet below the pipe to replace the existing weak wet sandy material therethat has sttled; the pipe does not contact any soil under it. In that case, would I be correct in assuming that the no fines concrete sand fill need not be placed under the pipe,but only around it?
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
Ok, thanks.
RE: Can Filter fabric be clogged by surrounding fill comprised of CSA concrete sand?
Guess my approach for drainage using perforated, slotted or wrapped pipe, generally in rough conditions that may occur is less stringent than Ron. I spec that you lay the pipe in on a sand layer, if you can (sometimes trenches are caving), but be sure you have the pipe surrounded with the filter sand. Sometimes the trench is filled most of the way with the sand, but at times you don't have that condition, but surrounding the pipe is mandatory. Since ASTM concrete sand many times is processed to get the correct gradation and thus is more x pensive than "bank-run" sand, so getting the filter around the pipe first is then followed by filling with less costly bank-run sand with low P-200 fraction.