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Components of a Concrete Mixer Truck
A concrete mixer truck consists primarily of a chassis and an upper assembly. It can be broken down into ten key components: the chassis system, hydraulic transmission system, mixing drum, discharge system, cleaning system, sub-frame, control system, support roller system, charging system, and electrical system.
(1) Chassis System: A primary component of the mixer truck; the chassis enables the vehicle’s transportation function.
(2) Hydraulic Transmission System: Converts engine power (extracted via the power take-off) into hydraulic energy (flow and pressure) and subsequently into mechanical energy (rotational speed and torque) via a hydraulic motor to drive the rotation of the mixing drum.
(3) Mixing Drum: The core component of the vehicle, serving as the container for the concrete; it plays a decisive role in preventing concrete hardening and segregation. Internal blades facilitate mixing and material guidance.
(4) Discharge System: Composed mainly of a main discharge chute, an auxiliary discharge chute, and a locking mechanism; the auxiliary chute extends the reach of the main chute.
(5) Cleaning System: Consists primarily of a pressurized water tank, spray gun, hoses, and valves. It utilizes air pressure to supply water for washing the hopper after loading and for rinsing the mixing drum and discharge chutes after unloading, thereby preventing concrete adhesion.
(6) Sub-frame: The primary load-bearing structure; it supports nearly the entire operational load and transfers it to the chassis. It also helps absorb impact loads caused by road bumps and deceleration. The sub-frame assembly comprises main beams, a front support bracket, and a rear support bracket.
(7) Control System: Composed of controllers, linkage shafts, flexible shafts, and linkage mechanisms; it primarily controls the rotational speed and direction of the mixing drum.
(8) Support roller system: The section connecting the rear of the mixing drum to the sub-frame; its primary function is to support the drum body.
(9) Feeding system: Composed mainly of a feed hopper and a support bracket. Since the feed hopper is subject to significant impact and abrasion, the material used must possess high wear resistance; the bracket serves primarily to absorb and reduce impact forces.
(10) Electrical system: Refers to the vehicle’s entire electrical network, including tail lights, side marker lights, clearance lights, cooling fan motors, etc.
Mixer truck sizes: Models ranging from 2m³ to 16m³—and even up to 20m³—can be manufactured.
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Working Principle of Concrete Mixer Trucks
A concrete mixer truck is a specialized vehicle designed to transport construction-grade concrete; due to its distinctive shape, it is often referred to as a “snail truck” or “olive truck.”
These trucks are equipped with a cylindrical mixing drum to carry the mixed concrete. The drum rotates continuously during transport to prevent the concrete from setting.
After delivery, the interior of the mixing drum is typically washed with water to prevent residual concrete from hardening and taking up space, which would otherwise reduce the drum’s effective capacity.
Based on the moisture content of the concrete transported, mixer trucks are categorized into three types: wet-mix, dry-mix, and semi-dry-mix.
Wet-mix trucks are the most common type; they transport either ready-mixed concrete from a batching plant or a mixture of aggregates (sand and gravel), cement, and water. During transport, the wet mixture is slowly and continuously agitated to prevent premature setting and segregation.
However, the time elapsed from production to pouring generally must not exceed 1.5 hours to avoid concrete setting. Therefore, for longer-distance transport, dry-mix or semi-dry-mix trucks are used.
Dry-mix trucks are loaded with dry aggregates and cement in the correct proportions directly into the drum. The dry materials are agitated during transport, and water is added—either just before arrival at the construction site or upon arrival—to complete the mixing process.
Semi-dry-mix trucks transport aggregates and cement that have been proportioned and contain some water, though the moisture content is insufficient for pouring. Additional water must be added and mixed in just before or upon arrival at the construction site.
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Operating Techniques for Mixer Trucks
(1) Before starting the engine, carefully inspect all components of the mechanical system to ensure they are in good working order.
(2) Before starting, place the mixing control lever in the “neutral” position.
(3) After starting, place the mixing control lever in the “discharge” position to drain any accumulated water from the drum.
(4) When loading materials, place the mixing control lever in the “loading” position.
(5) Before transport, the discharge chute must be secured in the “travel” position to prevent swinging.
(6) When operating the control lever, pause briefly in the “neutral” position before moving it to the next position.
(7) Maintain good worksite practices; do not indiscriminately dump excess material from the drum. After discharging, the mixing drum, chute, support rollers, and other components must be cleaned.
(8) When a person enters the drum to remove concrete buildup, the engine must be turned off, the ignition key removed, and a monitor stationed outside the drum.
