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RE: Spec needed for 3000 psi concrete

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Nels,

The information I provided came from the testing lab inspector who reviewed the spec supplied by the concrete company. He called me before our weekly meeting yesterday morning to tell me that the spec supplied to him was not acceptable. He looked through my general notes and all I specify is the strength and the requirement for special deputy inspection (the testing lab inspector), which I guess was not enough. He provided me with the weight of the concrete, the mix ratio (but no mention of aggregate size) and the maximum time and temperature that it can remain in the truck before placement occurs. If you think this is sufficient, then I will write it up as a memo to the GC to pass on to the concrete company but I believe that I should have something in the spec as to how the testing lab will test the mix and whether or not a slump test is required. I don’t think certification by the concrete company is sufficient if the inspector has already nixed the mix (pun intended).

 

What do you think? BTW, Randy Collier sent me a spec they us in Louisiana that we can modify and it is a very complete spec. I’ve sent it on to the inspector so that he can make modifications to it as he sees fit. I’d planned to use this modified spec to send to the GC. It is similar to a Masterspec specification that is specific to Baton Rouge area – rather complete.  

 

The Architect had assembled a specifications book but I did not provide any information on structural other than my own General Notes and Observation requirements. Should I have the inspector modify the full Cast-In-Place Concrete Section 0300 requirements and pass these along to the GC?

 

You know, I don’t recall having to be this specific on such a small job when doing retrofits years ago. I have even had to resolve the problems the GC and the steel company had in setting the frame (delivered fully welded including the base plates) on the erection pads (over the anchor bolts) and under the concrete lintel (existing). I gave them a number of suggestions including field welding the base plates or hanging the frame before the erection pads were placed if the city would allow it. I just don’t think I should have had to spend this much time solving a construction methods issue.

 

What do you think?

BTW, we need to catch up some time soon.

Best regards to you and Linda

Dennis

Dennis S. Wish, PE

California Professional Engineer

Structural Engineering Consultant

dennis.wish(--nospam--at)verizon.net

http://www.structuralist.net

 

-----Original Message-----
From: Nels Roselund, SE [mailto:njineer(--nospam--at)att.net]
Sent: Friday, October 08, 2004 8:13 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Spec needed for 3000 psi concrete

 

Dennis,

 

For most small projects, I specify the strength I want and other characteristics, and then require that the concrete supplier submit a design along with evidence [a record of previous tests] that the proposed mix meets the specified criteria.  For a major project, I have had a concrete consultant associated with a testing lab design the mix using materials from the supplier's bins for in-lab testing of the design.

 

Nels

 

Nels Roselund
Structural Engineer
South San Gabriel, CA
njineer(--nospam--at)att.net


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