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Re: Pea Gravel Concrete

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A 3000 psi pea gravel mix should work fine for the grade beam construction.
But, here's some more info:

Limited gradation and small aggregate sizes increase the water demand of a
mix for a given target slump when compared to a mixture using a good
gradation and larger aggregate sizes. Increased water usually requires the
addition of cement to control w/c. Increased water also means larger
shrinkage strains.

The increased water demand can be partially compensated for by using a low
range water reducer (added with the head water at the batch plant). A low
range water reducer may be adequate used alone.  Further water replacement
can be achieved by using a superplasticizer.

When using superplasticized mixes be sure to specify (and have tested) the
required slump prior to dosing the super. The pre-plasticized slump should
be between 1 to 2 inches. This slump test tells all. A slump test performed
after dosing the plasticizer may help tell you how workable the mix is but
nothing else. The proper plasticizer dose typically results in a final slump
in the 6 to 8 inch range.

Make sure the Contractor has the readi-mix supplier furnish a mix design and
historical test data (or trial batch records) for your review. They should
have available a number of pump mixes which can readily achieve 3000 psi.

If you need more info keep posting to the list or e-mail me at


Brent Koch, P.E.
Livermore, CA

From: JPWillow <JPWillow(--nospam--at)>
To: seaoc(--nospam--at) <seaoc(--nospam--at)>
Date: Thursday, December 11, 1997 6:39 AM
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
>the plans? The concrete is used for a 3,000 psi grade beam in a two-story
>V residential building.
>Paul Willow