Dear Paul,
To my opinion, the permeability of the asphalt layer, as measured in standard
laboratory conditions, is not a important parameter. The water entry will not occur
through this material, but through its cracks, which will appear after two, three or
four years. The waterproofing layer is installed to prevent water entry after
appearence of small cracks in the pavement, and thus reduces the degradation of the
roadway surface (potholes, frost action, etc.).
You will find many references and research results related to the efficiency of this
kind of interlayer in one of the four RILEM conferences proceedings, which should be
in a university near you. The web page of the last RILEM conference, held in ottawa
a few month ago, is :
http://www.nrc.ca/confserv/rilem/
Best regards,
____________
Eric Blond
Technical director
SAGEOS, Geosynthetics technology center
[log in to unmask] a écrit :
> Good Morning All
> Our Department of Transport in the Northern Territory, Australia has recently
> implemented the use of a waterproof membrane (usually a 10mm PMB seal) under all
> asphalt wearing surfaces used on our road network as there is a perceived
> problem of water penetrating the wearing course. Obviously this has increased
> our costs by 40-50% on new roads. Does anyone have any research they have
> carried out on the permeability of asphalt. I can understand the reason to use
> this under an open graded asphalt but it seems an ineffiecient and costly
> exercise under a dense graded mix.
> Regards
> Paul Bicknell
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