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RE: Water/cement ratio 1997 UBC

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Thanks for comments, everyone. The reason I brought this up was that I have
seen recommendations for water cement ratios in soils reports, however, not
on the current project. The concern was to address moisture permeability.
One report asked for a .43 w/c. Without other fillers, this is achieved by
added cement, therefore a 3,000 psi mix for strength goes up to around 5000
psi (I believe) and the workability goes down, so then we need to add super
plasticizers. For freeze thaw conditions with air entrainment the w/c ratio
is typically specified lower (.35) than the same non-entrained mix, however
I did not specify that. In addition the waterproofing consultant wants Xypex
added to the exterior walls. We were considering adding some Eclipse just to
see how many additives we could get in :^)  We have some architecturally
exposed concrete shearwalls where we used the same mix elsewhere for a
sample mock up and the contractor did not get a good finish, he can't seem
to get all the air bubbles out, it was a 12' wall. They are not overly
impressed with my boundary element stirrups @ 3-1/2" oc in a 10" wall. The
batch plant is working with him and they have consulted the Ouji Board and
they have begun chanting. They are trying a final stand alone mock up, so we
will see how that goes.


Regards,

Jeff

|~|Jeff,
|~|
|~|As the UBC parallels the ACI, you may note that this provision also
|~|disappeared from the ACI 318.  The last issue of ACI in which it appeared
|~|was the ACI 318-89. It also is no longer in ACI 301.
|~|
|~|(The nice thing about 318 as opposed to 301 and the Code is that 318 has
|~|commentary.) When you read the commentary in ACI 318 Section 5.4 you will
|~|note a lot of caveats that were ignored by many practitioners.
|~|
|~|I don't know the particulars on that specific ICBO change, but
|~|there was a
|~|problem of engineers and some building officials using table 19-A-7 as a
|~|minimum requirement.  The ACI commentary states that the table was "very
|~|conservative" and should only be used for "relatively small
|~|structures".
|~|
|~|Regards,
|~|Harold Sprague
|~|The Neenan Company
|~|
|~|
|~|-----Original Message-----
|~|Jeff Smith wrote:
|~|
|~|> Does anyone know why table 19-A-7 for water cement ratio was
|~|deleted from
|~|> the 1997 UBC?
|~|>