Slump test after adding Super P? 7

[Mr168]

Please forgive my ignorance on the subject, as I am a welding guy trying to help a fellow QC guy find an answer.

Is it required or outlined in any code as to when slump tests should be performed when Super P plasticizer is used? The concrete had all tests run before adding the Super P, air tested ok, slump was routinely low. These results were documented, the Super P was added, and no additional testing was performed before it was poured.

This is foundation work for a fossil power plant.

We're going under the assumption that the addtion of the Super P would pretty much invalidate any slump test anyways, but we're looking for some evidence or section of code that confirms or refutes this process of running no further tests after the plasticizer is added (break tests were all coming back good).

This is pretty much a CYA scenario in case of a QA audit or something like that. Thanks for the help.

 

[dik]

Further to Ron's comments, slump is also a measure of the amount of shrinkage anticipated... I generally spec slump as 4" max. for general usage and 3" max. for slabwork and tell the testing agency that I expect this to be followed.

Dik

 

[conceng]

What I tell my ACI Field Sampling & Testing Certification classes I teach is "the slump test is really only a measure of the slump of the concrete". With today's admixture packages and supplementary cementitious materials added to the concrete, the slump test is primarily useful as tool to measure the load to load or batch to batch consistency of the concrete. It cannot be used to measure the water added, w/c ratio, workability, strength, shrinkage, or any physical property other than slump. I've seen 6" slump concrete that is less workable than a 1" slump concrete. I've had 8" slump mixes with 1/3 the shrinkage of a 4" slump concrete just due to proportioning and admixture packages. Just by changing the aggregate proportions of a given cementitious content and water content, I've gone from a 2" slump up to a 7" slump and then back down to a 5" just by increasing the coarse aggregate content and reducing the fine aggregate.

The slump test will alert you to something being different in the load such as water content, air content, aggregate proportions, admixture dosage, admixture compatibility, time since batching, temperature, foreign matter contamination, or some other cause I'm not able to come up with right now. A significant change in the slump should send up the yellow or red flag that something in this load of concrete is different and a decision must be made as to if the deviance is acceptable after investigating the likely causes.

Some rules of thumb that will remain true given all else being equal:
1 gallon of water per yard is equal to 1" change in the slump,
1% variance in air is equivalent to 3/4" of slump
10 degrees F is equivalent to 1" of slump.
These get a little tricky with air entrained mixes, because the air usually goes up when water is added.

Greg

 

[mugzy1]

Slump is taken after HRWR is added regardless of opinions.

Check

http://www.todaysconcretetechnology.com

 

[darthsoilsguy2]

if the specifications mandate the Super-P slump to be between 7" to 9" (for example) and the pre-Super-P slump to be less than 3" (for example) than the contractor and concrete supplier have already agreed to meet this criteria and that it may/will be tested.