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RE: Pea Gravel Concrete

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A residential job is obviously very different than a large commercial
job, but I always reject pea gravel mixes.  As a matter of fact, I have
in my specs now to not even submit pea gravel mixes.  Contractors
usually want to use pea gravel mixes because they like to use small
grout pumps chiefly used for block walls instead of a proper concrete
pump.  The reason is obviously economic.  The problems just cascade from
there.  The smaller line necessitates pea gravel.  The smaller aggregate
requires more sand which, in turn, requires more water.  Oversanded
mixes are a real problem.  The results are often a very high
water/cement ratio.  (There is no reason that the w/c ratio cannot be
kept below .5.)  The ratio of sand to aggregate should be about equal.
With a pea gravel mix, the sand gets up to 60 or 70 percent.  The result
in my experience is that the mixes often do not come up to strength.
Also, with so much sand and water, there is a propensity to crack.  In
my view, the reason to lean toward pea gravel is for the contractor's
convenience and to save him money, not to produce a better product.
There are undoubtedly times when pea gravel is necessary for very
confined spaces or the like, but as a general rule, I do not allow it.

Kent Estes, S.E.  

> ----------
> From: 	JPWillow[SMTP:JPWillow(--nospam--at)]
> Sent: 	Thursday, December 11, 1997 6:23 AM
> To: 	seaoc(--nospam--at)
> Subject: 	Pea Gravel Concrete
> Can anyone tell me if there could be potential problems in approving
> the
> contractor  to use pea gravel rather than 1" rock concrete mix as
> specified on
> the plans? The concrete is used for a 3,000 psi grade beam in a
> two-story type
> V residential building.
> Paul Willow