Shrinkage of concrete and low strength of cylinder break
Shrinkage of concrete and low strength of cylinder break
(OP)
Hi all,
I am involved in pumping station project and during concrete pour for slab on grade for reservoir we cast set of prisms to test Linear Shrinkage. I received test results from testing company. The test results show shrinkage around 0.044, which is slightly over the specified limit in the specs.
The individual test result of one specimen between 0 and 1 day shows expansion of the concrete. The other specimen shows expansion between 4 day and 7 day reading and one specimen show no change in length between 4 day and 7 day. Is it possible to have such kind of behavior? As per the testing company all specimens were placed in controlled humidity and temperature as per ASTM
Second question related to same project. We used 4300 psi concrete. The test results from cylinders break is less than specified strength (4090 psi at 56 day break). The concrete was used for base curb. Should I ask contractor to remove concrete and replace or the strength is acceptable?
Thanks
I am involved in pumping station project and during concrete pour for slab on grade for reservoir we cast set of prisms to test Linear Shrinkage. I received test results from testing company. The test results show shrinkage around 0.044, which is slightly over the specified limit in the specs.
The individual test result of one specimen between 0 and 1 day shows expansion of the concrete. The other specimen shows expansion between 4 day and 7 day reading and one specimen show no change in length between 4 day and 7 day. Is it possible to have such kind of behavior? As per the testing company all specimens were placed in controlled humidity and temperature as per ASTM
Second question related to same project. We used 4300 psi concrete. The test results from cylinders break is less than specified strength (4090 psi at 56 day break). The concrete was used for base curb. Should I ask contractor to remove concrete and replace or the strength is acceptable?
Thanks





RE: Shrinkage of concrete and low strength of cylinder break
Based on the strength, I'd say no - don't replace. Refer to this: FAQ507-1575: How to Evaluate Concrete Tests per ACI 318
Your strength is not more than 500 psi below specified. As the EOR I'd check that the lower f'c still works with any design loads (lower f'c usually doesn't affect strength that much except for shear).
RE: Shrinkage of concrete and low strength of cylinder break
As far as your shrinkage tests, are you measuring between 1 and 28 days as required or 0 and 28 days? I almost never have a problem with shrinkage between 1 and 28 days.
RE: Shrinkage of concrete and low strength of cylinder break
It is between 1 and 28 days, the final test results show shrinkage but few readings as i said show slight increase in length (between 4 and 7 days). One specimen show 1 mm increase and other specimen show 1.5 mm increase. Overall results of shrinkage looks fine. Just to know is it possible to notice increase in length between 4 and 7 day?
Thanks
RE: Shrinkage of concrete and low strength of cylinder break
If the aggregate, at the time of batching, was less than saturated, surface-dry (SSD) it will imbibe water, causing it to expand. This is particularly true of laboratory cured specimens.
As for strength, I agree with JAE that replacement is not indicated for that reason; however, as JC pointed out, durability will be affected...particularly since your strength was ultimately only close at 56 days, not 28.
Side note...JAE...the strength at 56 days was within the 500 psi undertolerance, but was that so for the 28 day strength, which is the evaluation criterion?
RE: Shrinkage of concrete and low strength of cylinder break
Why the 4300 psi? Seems like a weird value (vs. 3000, 4000, 5000, etc.) I know they are just numbers, but 0's are good numbers.
RE: Shrinkage of concrete and low strength of cylinder break
RE: Shrinkage of concrete and low strength of cylinder break
RE: Shrinkage of concrete and low strength of cylinder break
RE: Shrinkage of concrete and low strength of cylinder break
RE: Shrinkage of concrete and low strength of cylinder break
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RE: Shrinkage of concrete and low strength of cylinder break
RE: Shrinkage of concrete and low strength of cylinder break
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