Slump Test
CSI Division 03, Concrete
A quick field test, filling a cone-shaped mold with wet concrete, lifting the mold, and measuring how far the concrete slumps down, used to check whether a concrete mix is workable enough to pour and finish properly.
Why it matters
Concrete that's too stiff is difficult to place and consolidate around rebar, while concrete that's too wet loses strength as it cures. The slump test gives a fast, repeatable way to catch a mix that's out of spec before it ever gets poured, rather than discovering the problem after it's already in the forms.
On a real project
A ready-mix truck arrives at a jobsite, and before the pour begins, a crew member runs a slump test on a sample from the load, confirming the slump falls within the range the mix design calls for before approving the truck to discharge.
Who this matters most to
A Concrete Worker or quality technician runs a slump test on nearly every concrete delivery, since it's the fastest way to catch a bad mix before it's committed to the forms.
Where this goes wrong
A crew under time pressure skips the slump test on a delivery and pours concrete that turns out to be far too wet. The extra water weakens the cured concrete's final strength, a problem that isn't discovered until strength testing weeks later, long after the pour can be undone.