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RE: Concrete at Higher than Normal Temperatures

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There was quite a bit of work done in the area during the 70s and 80s in
support of the Clinch River Breeder Reactor project because it used liquid
sodium as a coolant.  Some ACI papers on concrete properties were published
during that time.

Also, some work was done by GE San Jose, CA on their Boiling Water Reactor
projects in the early 90s.  In some cases the contemplated temperature
exposure of reinforced concrete was 300F for at least two months.  The
Canadian National Buildings Lab (or something like that) published some test
results on long term (4 month) heat exposure.  The Japanese and British (1+
year exposure) published some test results in the Structural Mechanics in
Reactor Technology (SMIRT) journal also.

Anyway, the exposed material does lose strength and gets softer when exposed
to sustained heat.  But from what I know about it, predicting how bad it
could get is difficult; some mixtures aren't affected, others turn to a pile
of rubble under their own weight.  But most of the "damage" seems to occur
during the first heating cycle.

The major difference between sustained heating and structural fires is
whether the fire lasts long enough to drive out the free water and gel
water.  Of course, the duration depends upon the permeability of the
concrete to water and steam and the concrete's configuration (including
boundary conditions).

Try contacting Burns and Roe of Oradell, NJ, USA.  If you need some
contacts, please reply to me privately.  Otherwise, best of luck, it can be
an interesting subject.

Ray Pixley, PE

> -----Original Message-----
> From: Nick Bassar [mailto:nbassar(--nospam--at)AeroSysEngr.com]
> Sent: Wednesday, February 02, 2000 10:27 AM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: Concrete at Higher than Normal Temperatures
>
>
> Does anyone know of resources which explain what happens to
> portland cement
> concrete (reinforced) when subjected to long term service in the 150 F to
> 300 F range?  I'm mainily looking for how the material degrades, and the
> resulting effect on it's mechanical properties.  I'm also looking for
> information on what happens when there is a significant number of thermal
> cycles in this range.
>
> I can find a lot of information on what happens to concrete during a fire,
> but I don't believe it's applicable due to the short term nature of fire
> temperatures.
>
> Thanks for your help.
>
>        Nick Bassar
>
>