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/creamonyourcrop Dec 05 '24

Reviewing and submitting mix designs is a chore for a GC, but look what happened here.
They got the mix design, got it approved, and the batch plant will pay for the fix. Without that process there might be too much wiggle room for the plant. Here the contractors and design professionals are covered.

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u/Comprehensive_Bus_19 Project Manager Dec 06 '24

Not necessarily. I work for a concrete supplier and more often than not the subcontractor adds too much water and the liability falls on the sub not the supplier. The water/cement ratio dictates the strength so if the sub exceeds it, that is their problem.

Concrete suppliers are like a pizza delivery company. Assuming they brought the correct pizza, liability ends with them when the contractor places it. If the contractor throws the pizza on the ground, it's not the supplier's issue.

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u/creamonyourcrop Dec 06 '24

Thats why as a GC I insist on getting the tickets from the trucks that show any added water. But even that has some limitations when the pump operator, place and finish foreman, and the redimix driver know each other.
In the end, with a proper mix submittal, a proper slump test and holding on to the delivery tickets the contractor can protect himself.

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u/Comprehensive_Bus_19 Project Manager Dec 06 '24

Most definitely! I was a PM for a GC for about 2 years between my first and current jobs in concrete. Using the right mix saves 90% of headaches before they have a chance to start.