huangyhg

maturity method vs field cured cylinders
we have a post tensioned parking garage under construction. the testing agent has requested to use the maturity method (astm c1074) for all concrete strength testing, instead of field cured cylinders.
with maturity method, probes were placed at multiple location at the slab prior to pour. after pour, they come with a digital reader to read the concrete strength of the slab at the probe location.
the first pour has succesfull reached the concrete strength with both the maturity method and the field cured cylinder test.
based on this, the testing agent has requested to abandon field cured cylinder testing.
i have no experience in maturity method, therefore i am feeling uncomfortable about not doing any conventional cured cylinder testing.
please, if you have any experience with this, either bad or good, i would appreciate if you could share with me.
again, please shed some lights on this matter, i would really appreciate that.
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here's a post of the actual astm spec:
you may also want to check with the local building department to make sure they'll accept it.
sounds weird to me too.
is the contractor batching the concrete themselves? i would think the concrete company would act like their concrete was perfect if lab-cured cylinders aren't cast and a problem comes up.
i can't think of any alternate tests that don't involve compressing a sample that can stand alone for acceptance testing (and concrete beam testing for pavements). all the other ones, in my experience, are supplemental.
i had a similar situation. when we looked into it, the maturity figures had to be calibrated by breaking cylinders cured on the same conditions as the rest of the slab, and everybody i talked to seemed to think that the results were approximated anyway.
we didnot feel confortable enough to use maturity to determine when to post-tension our structure, but i would be happy to hear from anybody with more experience in the matter.
even if the concrete was cast in a plant controlled environment (like precast plant, etc), i shall still be hesitant to accept the result from the maturity alone without a secondary method verifying it.
i have used maturity testing on large, repetitive projects. cylinder breaks were used for the first several pours to establish a correlation, then were discontinued when all parties (engineer, inspector, owner, etc.) were satisfied and comfortable with it.
the maturity meter was used in texas to accelerate the process of form removal and loading of new placements of concrete. it was found that the higher temperatures accelerated the maturity process of concrete allowing early removal when a minimum strength was achieved. this was not a substitute of compressive cylinders stored at lab conditions for 28 days but rather a measure of early strength gains due to higher temperatures in the forms. the strength must be from a lab cured cylinder of 28 day age and the "maturity meter" expresses the percentage of final strength for the concrete in the forms. you still must have cylinders to know what the value of 100%.
thank you all for your responses. they are very helpful. basically, we agree that even with maturity test, lab cured specimens are required. as pointed out by jae, astm actually specify that the maturity method must be backed up with supplemental tests. civilperson further verify that.
taro - thanks for your info. that makes me feel comfortable about the accuracy of the test.
for the rest of you all - again - thanks!

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