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RE: Concrete Mix for low permeability

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If you must rely on your slab for permeability, you can try the following
recipe:  in your concrete mix, replace 25 to 50 % of the cement by ground
granulated blastfurnace slag or fly ash.  You will get far less permeable
concrete, and probably much higher compressive strength, but it needs to be
cured more carefully than ordinary concrete.
  Another option is a curing or sealing compound.  You spray it on after
your concrete has cured and it will seal and protect the surface quite
effectively.
  Please note that concrete with slag/fly ash replacement does not perform
as well as ordinary concrete when exposed to a lot of freezing and thawing
or deicing salts.  Should be OK for Alabama, though.

Regards
Maria I. Falconi

-----Mensaje original-----
De: MSSROLLO(--nospam--at)aol.com <MSSROLLO(--nospam--at)aol.com>
Para: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Fecha: Lunes 26 de Abril de 1999 07:24 PM
Asunto: Concrete Mix for low permeability


>Does anyone have any information concerning what to add to concrete mix or
>specify for an overhead slab that is exposed to weather.  It is needed to
>minimize cracking and reduce permeability.  I am designing around 4000 psi
>and the slab has a room under it.
>
>I have never done a slab that had "dry-space" under it.
>
>Thanks.
>Ron Martin
>Tuscaloosa, AL
>
>
>