Concrete Cylinder Break Test
CSI Division 03, Concrete
A quality control test where cylindrical concrete samples are cast from a pour, cured alongside it, and then crushed in a lab press at set intervals, typically seven and twenty-eight days, to verify the concrete actually reached its specified compressive strength.
Why it matters
Concrete doesn't reach its full design strength the moment it's poured, it gains strength over weeks as it cures, which is why the test happens at two checkpoints: the seven-day break gives an early read on whether the mix is on track, and the twenty-eight day break is the one that actually confirms the concrete met its specified design strength.
On a real project
A testing lab casts six cylinders from the same batch of concrete used in a foundation pour, breaks two at seven days to get an early strength indication, and breaks the rest at twenty-eight days to confirm the pour meets its specified design strength before the project relies on that foundation structurally.
Who this matters most to
A QA/QC Inspector oversees cylinder sampling and tracks the lab results against each pour's specified strength requirement.
Where this goes wrong
A pour's twenty-eight day cylinder break comes back below the specified strength, but by that point the concrete has already been in place for a month and other work has already built on top of it. The low result forces an expensive structural evaluation to determine whether the pour is still acceptable.