A concrete agitator is a rotating drum or mixing device mounted on a truck that keeps freshly mixed concrete in continuous motion during transport from the batching plant to the construction site. By slowly turning the drum, the agitator prevents the concrete from setting prematurely, segregating, or losing workability before it is poured.
How it works
The agitator drum is typically a large, pear-shaped steel cylinder mounted at an angle on the truck chassis. Inside the drum, spiral blades (also called fins or flights) are welded to the interior wall. As the drum rotates at a slow speed — usually between 2 and 6 revolutions per minute — these blades continuously fold and tumble the concrete, keeping the cement, water, sand, and aggregates evenly distributed. When the truck arrives at the job site, the drum rotation is reversed to discharge the concrete through a chute at the rear.
Types of concrete trucks
There is an important distinction between agitator trucks and mixer trucks:
- Agitator trucks — Receive pre-mixed concrete from a batching plant and simply keep it moving during transport. The drum rotates slowly to maintain consistency.
- Transit mixers — Receive the raw ingredients (cement, water, aggregates) and mix them at higher speed during the journey to the site. The drum serves as both mixer and agitator.
- Volumetric mixers — Carry the ingredients separately and mix them on-site, producing fresh concrete on demand.
Application
Concrete agitators are essential in modern construction for:
- Ready-mix concrete delivery — The vast majority of commercial and residential concrete is delivered by agitator trucks.
- Large pours — Continuous delivery by multiple trucks ensures uninterrupted placement for foundations, slabs, and structural elements.
- Remote sites — Agitator trucks transport concrete over long distances while maintaining its quality and workability.
Related terms
- Ready-mix concrete
- Concrete pump
- Slump test
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