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RE: Spec needed for 3000 psi concrete

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What I am confused about is, on what basis did the testing lab have to say
that the mix was not acceptable. The fact that you did not specify weight
of concrete and mix ratio does not mean that the mix is inappropriate.  It
is probable that by changing the rules after the contract was signed that
the Contractor has a claim for an extra.  In such a case I would only make
a change if there was evidence that the resulting concrete would not
provide necessary properties.  Look carefully at your notes and the
Architects specificationa and make changes only when clearly appropriate.

I do not believe that it is the testing laboratories job to reject a mix
for reasons not specified in the construction documents.  This is the EOR's
perogative.  The testing laboratory can provide advice but it is our job to
make the decision.

The failure to control how much time the concrete can remain in the truck
is not a reason to reject the mix design.  This has to do with workmanship
issues that should be addressed elsewhere.  Be aware that the real criteria
is not how long the concrete is in the truck but rather has it started to
set up and can it be placed sucessfully.  Time limits are only general
guides that are appropriate most of the time.

The fact that the Architect included a specification on concrete without
obtaining input from the EOR is scary.  On the other hand if  the EOR knew
there were specifications created he should have enquired.  I would suggest
that it is not the inspectors role to modify the consrete specifications. 
Modifications to the specifications should be prepared by the design
professionals and should be provided to the GC by the Architect.  Here
again any changes to the specifications at this time will likely result in
a claim for extras.

Writing construction specifications related to our scope of work is part of
our work.  While many small projects can be built with only some notes on
the drawings we are in a litigatious environment and the size of project
that needs specifications is constantly changing.

Mark Gilligan

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