Concrete
Slump
A measure of the consistency and workability of fresh concrete, determined by filling a cone mold, lifting it, and measuring how far the concrete settles.
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In the Field
Inspectors pull slump tests at the truck before any pour. If the slump is too high the driver may have added water on the road — reject the load. Typical slump for footings is 3–5 inches; for slabs 4–6 inches.
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Rule of Thumb
Every extra inch of slump above spec adds roughly 1 gallon of water per yard, which drops compressive strength by about 200–300 psi.