Concrete mixer trucks are essential equipment in construction projects, and their operating procedures directly impact the final quality of concrete. This article systematically explains the working principles of mixer trucks, transportation precautions, concrete batching control, and best practices to help mixer truck drivers and construction teams ensure concrete quality.
A concrete mixer truck uses a power take-off device to extract power from the chassis, driving the variable displacement pump in the hydraulic system. This converts mechanical energy into hydraulic energy, which is then transmitted to the fixed displacement motor. The motor then drives the reducer, which in turn drives the mixing mechanism to mix the concrete. The tank is cylindrical, with multiple spiral-shaped mixing blades on the inner wall. These rotating blades evenly mix the mixture, preventing separation or sedimentation during transportation.
2.1 Key Points for Pre-Start Inspection
Completely inspect the mechanical system, exterior, tires, hydraulic system, and other systems. Ensure adequate water in the water tank. Check the antifreeze, lubricating oil, and cooling water. Place the mixing lever in the "neutral" position.
Check the lighting system, especially the side lights, ensuring they illuminate the tire edges. Clean the rearview mirrors and windows to ensure a clear view.
2.2 Continuous Rotation to Prevent Segregation
When the concrete mixer truck is unloaded or in transportation, the mixing drum must be continuously rotating to prevent wear of the raceway and rollers and concrete segregation.
The recommended rotation speed during transportation is 3–6 rpm to maintain concrete uniformity.
2.3 Turning and Speed Control
Strictly prohibit sharp turns at high speeds when fully loaded. Appropriate speed reduction should be applied to prevent lamination and uneven distribution of concrete. The mixing speed should be maintained at 2-4 rpm, and the entire conveying process should be kept within 300 rpm.
2.4 Time Limit
The transport time from the concrete batching plant to the pouring site should not exceed 90 minutes. This should be shortened in high-temperature environments, such as temperatures above 25°C, to approximately 60 minutes. In low-temperature conditions, this time can be slightly relaxed to within 90 minutes.
2.5 Speed Adjustment Before Arrival
Upon arrival at the construction site, the mixing drum should be rotated at a high speed of 14-18 rpm for 1-2 minutes before discharging.
2.6 Cleaning and Maintenance
After each unloading, immediately clean the feed hopper, discharge chute, and other areas with a hose. During transport back to the concrete mixing station, add 150–200 L of clean water and rotate for 5–10 minutes to prevent any residual hardening.
When using a high-pressure water jet, maintain a distance of 40 cm or greater between the nozzle and the vehicle body to avoid damage to instrumentation and paint.
2.7 Special Situation Handling
Adding water to adjust slump during transportation is strictly prohibited. This must be handled by concrete mixing station technicians. If slump does not meet requirements, the concrete must be returned to the concrete mixing station for adjustment. Adding water on-site is not permitted. In the event of water shortages during transportation, add water on-site and mix at a speed of at least 6–18 rpm for 30 revolutions.
3.1 Accurate Measuring
Standardized electronic metering equipment should be used for batching. The deviation between single-plate and cumulative measurements must be strictly controlled (e.g., ±2% for cement, ±3% for aggregates, ±2% for water, and ±1% for admixtures).
When moisture content fluctuates, water and aggregate mix should be adjusted promptly, and moisture content measurements should be measured more frequently.
3.2 Allowable Material Error
|
Material Type |
Allowable error range |
Control Points |
|
cement |
±1% |
The error of each bag shall not exceed±0.5kg, and the electronic scale shall be calibrated 3 times a month |
|
coarse aggregate |
±2% |
Control the discharge height and install anti-segregation baffles |
|
fine aggregate |
±2% |
When the moisture content changes by more than 0.5%, the mix ratio should be adjusted |
|
admixtures |
±1% |
Liquid admixture storage tanks must be equipped with temperature control devices |
|
Mixing water |
±1% |
During the rainy season, the moisture content of sand and gravel should be tested at least 4 times a day |
3.3 Mix Proportion and Temperature Control
Before mixing, implement control measures such as preheating or cooling based on ambient temperature. For example, in summer, use cold water, sprinklers, or sand and gravel to cool the mixture to ensure the mold entry temperature is ≤ 30°C. In winter, preheat the water source to a temperature no higher than 60°C to ensure the mold entry temperature is ≥ 5°C.
3.4 Mixing and Secondary Mixing
Forced mixing machines should mix within the specified minimum time (e.g., 90–150 seconds for a slump ≤ 40 mm, depending on the specifications). If segregation, bleeding, or slump loss occurs during transportation, a secondary mix should be performed. Adding water on-site is strictly prohibited. Adjustments to the cementitious materials or admixtures may be made as necessary to maintain a constant water-binder ratio.
3.5 Key Factors of Concrete Quality
Operational Factors: Water-binder ratio control, metering deviation, and mixing time are the three key factors affecting concrete quality.
Transportation Factors: Improper rotational speed can cause segregation, while excessive mixing time can cause initial setting.
Environmental Factors: Excessively high temperatures accelerate water evaporation, while excessively low humidity affects hydration.
Construction Factors: Improper vibration can cause internal unevenness, while insufficient curing can affect strength development.
Equipment Factors: Metering system errors and wear of the mixing device can affect final quality.
4.1 Daily Maintenance
Check the engine coolant level, radiator cleanliness, and sun protection equipment (sun visors, sun blinds).
The hydraulic system must comply with the instructions in the operating manual and must not be adjusted arbitrarily. Keep the hydraulic oil clean and within the specified quantity.
4.2 Brake System Inspection
Pay attention to brake pedal pressure, brake smoothness, abnormal indicator lights, and sound changes. Regularly replace brake pads and brake fluid to prevent malfunction.
4.3 Vehicle Inspection Process
Ensure the proper operation of all equipment through visual inspection, no-load and load testing, hydraulic system pressure and flow testing, brake performance testing, and electronic control system and vibration and noise testing.
5.1 Safe Operation
Before starting the concrete mixer truck, place the operating handle in the "Stop" position. After starting, preheat the drum at low speed for at least 10 minutes. Continuous operation of the working device should not exceed 8 hours.
Strictly prohibit unsupervised or operator-guided operation to avoid pinching accidents. Protective equipment must be worn when working near the hopper or discharge chute. Never switch directly from forward to reverse during a full load.
5.2 Training Requirements
Drivers must undergo professional training and obtain a license to operate the truck and must comply with traffic laws and station regulations.
Through scientific transportation, precise batching, rigorous maintenance, and professional operation, as well as adherence to the aforementioned operating specifications and control standards, concrete mixer trucks not only ensure project quality but also enhance construction efficiency, safety, and a green brand image. Drivers should continuously learn and improve their operating skills, and construction companies should establish a comprehensive quality control system to jointly ensure the quality of concrete in construction projects. Every rotation, every drop of water, carries the solid promise of the project. Choosing the right mixer truck and operating it well will make construction more reliable and ingenious.
For more information on the operating instructions for concrete mixer trucks, or if you would like to purchase or customize a concrete mixer truck, please contact us. We offer custom-made mixer trucks based on your drawings.
