CONCRETE STRENGTH
CONCRETE STRENGTH
(OP)
This is a new one on me. Recently I was told that it had been stated at a seminar that concrete cylinder break strengths which were significantly higher than the design strength could indicate some kind of deficiency in the completed structure.
Certainly I can see that the "deficiency" could be that the concrete producer was losing profit in supplying material which is more expensive than specified, or necessary, but I'm stumped to come up with any reason why the designer should be concerned. Am I missing something?
Certainly I can see that the "deficiency" could be that the concrete producer was losing profit in supplying material which is more expensive than specified, or necessary, but I'm stumped to come up with any reason why the designer should be concerned. Am I missing something?






RE: CONCRETE STRENGTH
What about admixtures? I know sodium chloride is an effective plasticizer and contributes to higher early strengths; It's just TERRIBLE for the rebar.
YS
B.Eng (Carleton), P.Eng (Ontario), MIPENZ (Structural-New Zealand)
Working in Canada, and missing my adoptive New Zealand family... at least I brought the little Kiwi with me!
RE: CONCRETE STRENGTH
In California, concrete producers have a minimum and a maximum value of f'c that they can deliver to the job site precisely because of this reason.
RE: CONCRETE STRENGTH
RE: CONCRETE STRENGTH
Dik
RE: CONCRETE STRENGTH
What are the cylinder strengths you are referring to? - Ones submitted with a proposed mix design or samples from the job site.
If you are looking at submittals for the mix design, look at the testing data. Unless it is a unique project, a special, time consuming set of samples is usually not supplied and older test for the same mix with the same materials are taken from testing files.
For normal jobs, the savings in material substitution is not worth the extra problems since the common admixtures are so cheap when bought by the tank or truckload and dosed automatically.
If you are worried, you can request a lower strength that is closer to the design strength.
As usually, the delivery cost is still one of the two most important costs of a delivered yard of concrete.
If you are concerned with the performance of the completed structure, core samples could be an indicator, but they are often higher than the cylinder breaks, but could indicate placement or curing problems during construction.
RE: CONCRETE STRENGTH
RE: CONCRETE STRENGTH
RE: CONCRETE STRENGTH