Yes, you are right, all granites are not equal, however, more to the point is
that all environmental setting and conditions are far far from equal. Granite
blocks that are sitting in a narrow walkway in a yard is a completely different
set of conditions than a large area of granite pavers over a concrete base. The
walkway surrounded by a lawn, and possibly shaded, might allow most of the
salts to migrate into the soil and as a result would most likely have no real
affect of the stones. The soil is more porous. It absorbs and gives off
moisture much faster than the granite. As a result, the salt activity is drawn
away from the granite and leaves the stone basically unaffected.  If you had
porous stone or brick instead of granite, it could be a very different story.
Now think about granite pavers covering a larger area. The surface of the
pavers become the evaporation interface. The salts do not migrate into the
surrounding soil, most likely due to a Portland Cement based concrete substrate
with Portland Cement based mortar around the pavers. At that point the granite
may be the more porous material and be the one subject to damage by the salt
crystals forming and expanding on and within the surface of the granite. The
walkway may be shaded and the pavers may be in the open or even direct sun
light. The pavers are in a flat setting with possible drainage problems while
the walkway is sloped and drainage is good.

I have two pieces of marble in my yard. One is under a bush, the other in
direct sun light. The one under the bush is basically as good as the day I
placed it there. The one in direct sun light has surface deterioration
(sugaring of the surface). Two identical pieces of marble, two different
environments within 30 feet of each other, two different results.  Is it the
marble's fault?

MMmmm...corn on the cob, please pass the efflorescence.

Bryan

===========

Ruth Barton wrote:

> You all must have weak granite.  My front walk is chunks of granite about
> the size of cement blocks and I don't know how thick.  This walk is on
> quite an incline up from the street so you better believe it get plenty of
> salt every winter, cause I don't like skatin' downhill donchaknow, and I
> don't have any problem with the granite coming apart.  Now if I could just
> find some thing to eat up the gloppy cement somebody put between the
> granite blocks I'd be happy.  Don't know why they put it there, maybe they
> thought the blocks would move without it, but it looks like hell.  Ruth
>
> At 4:47 PM -0400 7/12/00, Mike Devonshire wrote:
> >In a message dated 7/12/2000 12:53:16 PM Eastern Daylight Time,
> >[log in to unmask] writes:
> >
> ><< I am looking for some case studies of spalling of granite paving  >>
> >Ain't got no paving, but we had pieces of granite the size of pizza slices
> >coming off the base of the Guardian Life building in NYC due to de-icing
> >salts. There are alternatives to chlorides, don't cha know.
> >
> >Village Idiot
>
> --
> Ruth Barton
> [log in to unmask]
> Westminster, VT