How Does a Concrete Mixer Truck Work?

Understanding the Working Principles of Mixing, Loading, Unloading, and Cleaning Functions

Concrete mixer trucks are vital for transporting ready-mix concrete from batching plants to construction sites. Their unique structure and systems allow them to mix, transport, unload, and clean efficiently. Here’s a breakdown of the key working principles behind a concrete mixer truck:

The mixing drum is powered through a series of mechanical and hydraulic systems. The process starts with the engine transmitting power to a hydraulic pump via a small drive shaft. This pump activates a hydraulic motor, which drives the reducer—a gearbox that controls the speed of the drum’s rotation.

During transportation, the mixing drum rotates slowly at about 1 to 3 revolutions per minute (RPM). This low-speed rotation keeps the concrete well-mixed and prevents segregation or settling of the ingredients. This process is commonly referred to as stirring or mixing on the move.

When loading concrete into the truck, the mixing drum rotates at a faster speed—typically 6 to 10 RPM. The concrete enters through the loading system and flows into the drum via a drum chute. Inside the drum, spiral blades guide the concrete toward the middle and bottom sections, ensuring even distribution and mixing.

To unload the concrete, the mixer truck reverses the rotation direction of the drum. Power from the engine is transmitted via the power take-off (PTO), hydraulic pump, and reducer, causing the drum to rotate at 3 to 14 RPM. The spiral blades inside the drum push the concrete toward the discharge mouth, allowing it to flow out smoothly through the discharge chute. The reversal in rotation ensures efficient and controlled unloading of the concrete.

After delivery, the concrete mixer truck must be cleaned to prevent hardened buildup inside the drum. The cleaning system uses water from an onboard water tank, which is pressurized using the truck’s brake air cylinder. This pressurized water is sprayed inside the mixing drum, loading port, and discharge chute to remove leftover concrete and keep the system clean for the next load.

Conclusion：

Understanding how a concrete mixer truck works—covering mixing, loading, unloading, and cleaning functions—is essential for operators, engineers, and construction professionals. These systems work together to ensure concrete is delivered on time, in the right condition, and with minimal waste or mechanical issues.