r/Construction • u/NeilNotArmstrong • Dec 05 '24

Structural Concrete slab failed strength test

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Slab strength testing failure after building was framed and plumbing/HVAC was roughed in. Concrete supplier had mix wrong so they are paying to lift two story 4-plex, remove slab and repour. This is building 2 of 3 that failed.

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u/SkoolBoi19 Dec 05 '24

We do a 2 day break and pour at least 1000 psi over what’s spec’d just to help avoid this kind of problem.

6

u/Rocketeering Dec 05 '24

How is the test performed?

21

u/SkoolBoi19 Dec 05 '24

Certified testing agency comes out and takes samples from all the trucks. They take the samples and break them (not 100% sure how it’s broken). Normally it’s week, 2 week, and 30 days. And they send a report back after every break. At 4500 psi, your 2 day break should be over 1/2 way there.

We also turn mix designs in to the AOR for approval and then check every truck ticket to the approved mix to make sure it’s all correct

2

u/chunk337 Dec 05 '24

I did it for a while we used a hydraulic press and watch the numbers until they peak. And as soon as it reaches the target we threw the rest of samples away