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Re: gravel under slab on grade

No, I don't have a sample specification for this, nor a list of
equipment.  This should be worked out with your geotech as Proctor
density tests do not reflect how granular soils can be compacted. 
ASTM D 4253 and D 4254 tests give the maximum and minimum index
densities of cohesionless, free draining soils and calculation of the
relative density.  I seem to recall reading a paper on the
effectiveness of different vibratory plate compactors, but I can't
recall where that was.  Besides, new equipment is coming out all the

I don't put much stock in "water-settling" soils.  Besides being
unpredictible, I have seen or heard reports that say the surface
tension of the water can actually prevent sand particles from
consolidating.  (Don't ask me where I saw or heard this either!) 
Likewise, I have seen or heard reports that say the water lubricates
the sand particles.  The latter is a situation that exists in Arizona
with "collapsing" soils.  These are soils that will collapse under
their own weight when exposed to increased moisture.  This will
frequently occur when a house is built and the owners install
landscaping, water it profusely to get it growing, and end up with
serious distress in their houses.  (Structural engineers and
horticulturists are at opposite ends in their recommendations. 
Horticulturists say if you want healthy plants, you deep water them, a
minimum of 2 feet; Structural Engineers say if you want a healthy
house, you keep planters, deppressions, etc., away from your house.)

As far as salt goes, if we get beach sand in Arizona, California would
have had one helluva wind storm <g>.  Seriously now, I can't even
begin to address that concern.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona