>>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.<<
Mary D

>I'm sitting here shaking my head over this one. Granite more porous than
Portland cement concrete? While I don't have numbers at my Sunday morning
fingertips, I'd bet that granite is both more dense and less permeable than
any but the highest strength/longest wet-cured concrete one can imagine.<
Mike E.

The granite almost certainly has a higher density (or specific gravity) than
the portland cement based mortar, but the porosity might be similar to the
mortar, particularly if it is rich in cement and contains only fine
aggregate.  As for the permeability ... the granite will probably be more
permeable than the portland cement mortar, because there is the ability for
moisture to travel via the grain boundaries and microcracks.  If we are
talking New England granites, then we are probably talking about rocks with
a well-developed system of microcracks, and hence a water absorption of
0.25-0.35%.  If you stand a piece of this granite in water, then capillary
action will take the water up the granite at least one foot, and possibly
eighteen inches to two feet.

So yup, I'd say that there is a very good chance that the moisture migrates
through the granite in preference to the portland cement based mortar in the
joints.

david west