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Low Concrete Quality - Units

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For those that do not do a lot of overseas work there are definitely two
metric system used around the world.  The SI metric system (Newtons,
Pascal's, etc.) is used throughout Europe and in U.S. textbooks.  However,
in large portions of the Middle East, South America, and Asia the MKS
(meter, kilogram, second) metric system is used.  If you buy rebar in these
areas it will definitely be kg/cm2 instead of MPa.  If you use RISA-3D you
will notice both unit options available.  As a side note, most of my
conversion headaches have been trying to convert from SI metric to MKS
metric instead of either one to U.S. Imperial units.  A very good units
converter program is Master Converter by Savard Software
http://www.savardsoftware.com/ .

Thomas Hunt, S.E.
Duke/Fluor Daniel

----- Forwarded by Tom Hunt/DFD on 06/18/01 10:03 AM -----
                                                                                                                   
                    "Lutz, James"                                                                                  
                    <JLUTZ@eartht        To:     seaint(--nospam--at)seaint.org                                                 
                    ech.com>             cc:                                                                       
                                         Subject:     RE: Low Concrete Quality                                     
                    06/15/01                                                                                       
                    08:41 AM                                                                                       
                    Please                                                                                         
                    respond to                                                                                     
                    seaint                                                                                         
                                                                                                                   
                                                                                                                   




I've never heard of compressive strength being expressed as kg/cm2.
Shouldn't it be N/cm2 or MPa? 210 N/cm2 or 21 Mpa is around 3000 psi. (1
Ksi
= 6.894 MPa.)

I've never used silica fume, but my understanding is that it dramatically
reduces concrete permeability, which adds a lot to durability. I believe it
has been used a lot for bridge decks. If you contact any distributor of
this
additive, I am sure they can give you plenty of information.

Try the following link.

http://www.masterbuilders.com/MB/pub/Products.asp?TypeCat=2&ParentID=101



-----Original Message-----
From: Leonardo Zapata [mailto:Lzapata(--nospam--at)otepi.com.ve]
Sent: Friday, June 15, 2001 8:18 AM
To: seaint(--nospam--at)seaint.org
Subject: Low Concrete Quality


We have a problem in the foundations of the most important building of the
Main Process Station: Central Control Room.
It was initially a concrete structure supported on direct foundations but
after foundations construction was already started, the structure was
changed to Steel, therefore the foundation are over-dimensioned.
A value of compressive strength at 28 days of 250 kg/cm2 was specified for
all structural concrete in the project. During the construction, all
footings were poured the same day and the average strength obtained for
them
at 28 days was between 285-306 kg/cm2. Five days later, all pedestals were
poured and the average strength obtained for them at 28 days was between
149-166 kg/cm2.
Venezuelan codes applicable in Oil Industry specify minimum 210 kg/cm2 for
foundations, 250 kg/cm2 for aggressive environment and 140 kg/cm2 for lean
concrete.
The facilities are located in a no-aggressive environment and in a seismic
zone with ground acceleration of 0.24g.
Due to a bad inspection, the building is already totally built. We have
performed the structural calculation with the low strength and apparently,
there is no problem because the loads are lower than those used in the
initial foundations design. As the timelife at the facilities is stated in
25 years, our main concern is about durability of the concrete. Contractor
is arguing the use of Silica Fume in his concrete which increase the
durability.
Does anybody have experience about it?
Any help is really appreciated.


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