huangyhg

concrete failed at 3000 psi
can anyone pls. need ur opinion. im a civil engineer for 5 years here in the philippines. i still havent encountered concrete failed at 3000 psi at 28 days (as designed). i this do happened, what is the proper way to do. do i need to remove the concrete or wait until 3000 psi is attained??? pls... anyone help! thanks!
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there's too many possibilities to cover them all. 3000psi may not be the "make or break" point...become familiar with the acceptance criteria for aci (if that is what you're using). some engineers may reevaluate whether a lower strength is acceptable while other engineers may reject it all together. and if the cylinders break low, core the in place concrete first before taking it all out since the in place concrete is more often than not at a higher strength than cylinders...also keep in mind that cylinder strength and core strength are not the same thing.
check the many other threads on the site that discuss low breaks.
never, but never, assume the liability yourself for an understrength design to save either the neck of your client or the contractor.
if it is understrength at 28 days statistically, have it removed and repoured according to the original specs. put out the word in advance to all concerned that this will happen if the strength is not achieved. i guarantee youthat sufficient cement will be put in the mix to achieve the strength.
mike mccann
mmc engineering

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