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"retempering" concrete

B

BSSTG

Gold Member
Joined
Nov 30, 2009
Messages
729
Location
Seadrift, Tx.
Greetings,

Well I took the commercial bldg yesterday and did not pass (scored 70). I was really miffed by a few questions. But one I never heard of was to the effect of "who is required to approve concrete when it has to be retempered". Now I'm certainly not a conrete guy and I have no idea what they were asking. I've never heard of "retempering concrete".

By the way, that test was loaded with conrete and masonry questions. Must of been about 20.

completely ignorant on this one

BS
 
Retempering should mean wetting it down again...commonly refered to as "loosening" it up....answer should be the special inspector...or maybe AHJ...
 
I agree with steveray, should be a special inspector, IMHO.

Retempering is the process of changing the consistency of a concrete mixture by adding water and remixing. As it is common to send the concrete to the placement site with slightly less water than the maximum that may be used, it is expected that a specified amount of water can be added if necessary. The contractor may add the water because the mixture arrives at the site in a condition that would make placement and finishing difficult. These difficult HCCs are often called harsh mixtures. They lack workability. (The only quantitative measure of workability is slump.) (See sections 6.1 and 8.4, Gaynor and Meininger, 1983; Pigeon, Saucier, and Plante, 1990.)
 
Retempering is not common terminology for engineers.

Adding water at the site is often prohibited by some project specifications due to abuses of adding too much water and thus reducing the strength of the concrete and causing other problems.

I believe that ASTM C94 allows adding water under certain limited circumstances. First you need to know how much water was added to that truck at the batching plant. If that amount of water was less than was listed in the mix design then it is acceptable to add the difference at the site. I believe that ASTM C94 says more on this subject.

If it is not possible to comply with the above criteria then either something is wrong with the batch or the wrong mix design was used and the concrete should not be placed. Workability can be improved by the proper selection of materials or by the addition of admixtures but this should be handled in a controlled manner and not by just adding water at the site.
 
1905.10.4 Retempering.

Retempered concrete or concrete that has been remixed after initial set shall not be used unless approved by the registered design professional.
 
Which code? ACI 318? The test was on the 09 IBC and ACI 318. However I had the ICC Conrete Manual which ICC says is suitable. I will not make that mistake again. That said, there was at least 1 other question with erroneous answers.

thanks

BS
 
What I posted was from an on-line version of the IBC, but when I looked in the code book today there actually is no 1905.10.4. I think I must have found someone's local ammendment on line.

Anyway - the answer is in section 5-10-4 of ACI 318. Same wording as I originally posted.
 
Yea that figures. That dang ICC manual was a waste of money insofar as helping pass the test. All of the IBC references for concrete quote ACI 318 for where to look for a lot of items. I was trying to save the taxpayers a few bucks by getting the concrete manual for the test as opposed to ACI 318. Big booboo. I should have figured that out before taking the test. Oh well it's in the past now.

thanks

Byron
 
Yeah I too just tested (passed luckily) for the B2 (commercial building) and found a number of questions were directed to the concrete manual.

The problem I had with that is it would direct you to a specific section in the manual but the section referenced did not have a clear answer. Plus, none of the practice questions or study guides had directed you towards the manual in preparation for the test. That concrete manual is not a book that I would pick to sit down with a cup-o-joe and find to be an interesting read.
 
You have to remember that concrete curing is a chemical reaction. Once it starts you cannot stop it. Adding water does nothing for concrete strength.
 
The problem with pulling questions from the concrete manual is that the manual is not code and you are supposed to comply with the code.
 
Well Martin,

I just got my ACI 318 (had to wait on the new budget) and confirmed retempering is 5.10.4 requiring the design professional........Once again, thanks

Byron
 
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