What Is Slump in Concrete?

Slump is a standard measurement of the workability or fluidity of fresh concrete. It indicates how easily the concrete can be poured, spread, and shaped, which directly impacts how it performs during placement.

The slump test involves filling a cone-shaped mold with concrete, lifting the mold, and observing how much the concrete “slumps” or sinks. The distance the concrete slumps is measured in millimeters or inches.

A higher slump means the concrete is more fluid and easier to work with—ideal for areas with tight forms or heavy reinforcement.

A lower slump means the concrete is stiffer and better suited for vertical structures or applications requiring more strength and less shrinkage.

Maintaining the right slump during transport is essential. That’s why the rotating drum on a concrete truck not only mixes the materials but also helps preserve the proper slump level until the concrete is ready to be poured.