RE: Pervious Concrete Paving
From: Prescott Nichols (pnicholsindigoarch.com)
Date: Fri, 6 Jan 2006 12:12:24 -0800 (PST)
Good questions.

Freeze-thaw: 
I do not have direct experience with pervious concrete in areas where the
ground freezes. It may be that since water does not remain in the matrix it
is not a problem, but maybe this is why you don't see pervious concrete
taking over the northern states! Perhaps the Concrete Network has more
information on this.

Oil:
As far as the oil goes, I can see how it would be more difficult to scrub
out any discoloration from the pervious concrete. The only way to avoid
discoloration altogether is to use an oil-based product like asphalt. If
your question has more to do with pollution concerns than staining, I agree
that it would make sense to use regular concrete in oil changing areas.
Elsewhere, the matrix is more than adequate to capture minor leaks.

Expense:
For paths and smaller areas that would require manual (truck chute/wheel
barrow) application, it costs about the same as regular concrete. There are
some trade offs: placing the concrete involves a little more labor, because
it is not as fluid as regular; however, there is no floating required, as
that would reduce the permeability of the material. Larger areas, like
parking lots, would probably be more expensive, because the material cannot
be pumped, but then you can start realizing savings by eliminating storm
drainage, including curbs and gutters, so parking lot costs tend to balance
out as well.

Other considerations:
- Existing trees can be saved by using pervious concrete within their
canopy. This alone makes pervious concrete the best option where parking
must commingle with existing trees.
- Something like 90% of hydrocarbon pollutants in storm water come from
resurfacing of asphalt parking lots. Pervious never needs resurfacing and
captures incidental hydrocarbon pollutants.

Cheers!
  _____  

Prescott Nichols, AIA
Muir Commons, CA
 


-----Original Message-----
From: Michael Barrett [mailto:mbarrett [at] toast.net] 
Sent: Friday, January 06, 2006 10:42 AM
To: 'Cohousing-L'
Subject: RE: [C-L]_ Pervious Concrete Paving


A question for Prescott:
How does Pervious Concrete Paving perform when the water in those pores
repeatedly freezes and thaws?  
Further it seems that the retention of (accidentally spilled dirty motor)
oil in the pores of the material might be a possible disadvantage, making
clean up even more difficult than solid concrete.

Michael Barrett
Liberty Village, Maryland, where we look forward to resuming building our
community once we get our long delayed sewer taps.  

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