The Disadvantages Of Weighing Methods In Concrete Mixing Plants

• Posted by Mavis Chai November 10, 2025 Filed in Technology #concrete mixing plants  #concrete batching plants  #weighing methods of concrete plant  52 views
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  When choosing a weighing method, we often focus on its advantages, but a clear understanding of its disadvantages is necessary to make the wisest decision. The following are the disadvantages that cannot be ignored for the three methods of cumulative weighing, independent weighing, and combined weighing.

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  I. Cumulative weighing: Although it may seem economical, there are actually many hidden dangers

   

  Cumulative weighing is a solution that has been almost eliminated by modern formal mixing plants, and its disadvantages are very prominent.

   

  1. Low accuracy and unavoidable error accumulation

  Core Disadvantage: This is its most fatal flaw. Due to the use of the same scale to weigh multiple materials in sequence, the weighing error of the first material will be directly transmitted to the second material.

  Specific manifestations: For example, there may be an error of ± 5kg when weighing sand. When the weighing bucket is zeroed and the stone is weighed, this ± 5kg error will accumulate to the weight of the stone. For small quantities of materials such as cement, this cumulative error accounts for a very high proportion of their total weight, seriously damaging the mix design of concrete, resulting in insufficient strength or decreased durability.

   

  2. Extremely low production efficiency and lengthy cycles

  Core disadvantage: Cannot achieve parallel operations, all materials must be "queued" for weighing.

  Specific manifestations: Only after weighing the sand can the stones be weighed, and only after weighing the stones can the cement be weighed...

  The entire weighing process is linear, and the waiting time is superimposed, resulting in a very long production cycle of the mixing plant (from unloading the previous plate to unloading the next plate), and the unit time output (energy) is severely limited.

   

  3. Serious cross contamination, affecting the quality of concrete

  Core Disadvantage: The same weighing bucket will weigh different materials in succession, inevitably leading to mutual adhesion and mixing.

  Specific manifestations:

  Dry and wet pollution: After weighing damp sand and gravel, a large amount of material will adhere to the inner wall of the weighing hopper, which will mix into the subsequent cement or fly ash, changing the actual proportion of the powder.

  Mixing of coarse and fine aggregates: The particles of sand and gravel will be embedded in each other, affecting the grading of the aggregates.

  Affects the effectiveness of additives: Even after cleaning, residual powder or aggregate in the weighing hopper will absorb the additives added later, resulting in a decrease in their effective ingredients.

   

  4. Reliability issues and inconvenient maintenance

  Core disadvantage: High risk of single point failure.

  Specific manifestation: The entire weighing system only has one set of weighing sensors and one set of weighing buckets. Once this core component malfunctions (such as sensor damage, scale hopper jamming), the entire mixing plant will be completely paralyzed and unable to produce any concrete.

  I. Independent weighing: the king of accuracy, but at a high cost

   

  Although independent weighing reaches its peak in accuracy, its disadvantages mainly revolve around cost and complexity.

   

  1. The highest initial investment and land occupation cost for equipment

  Core Disadvantage: "Cash ability" is the primary threshold.

  Specific manifestations: Each material requires an independent and complete weighing system, including a scale hopper, sensors, pneumatic or electric valves, and feeding pipelines connected to them. This has led to:

  Hardware cost surge: The number of sensors and scales has doubled.

  Complex structure and large footprint: More space is needed to layout independent weighing hoppers and feeding channels, which puts higher demands on the overall structural design of the mixing plant.

   

  2. Complex structure with increased maintenance points

  Core Disadvantage: Higher complexity means more potential failure points.

  Specific performance: Although a single point of failure will not result in a complete shutdown, the number of equipment that needs maintenance has increased. Each sensor of the scale needs to be calibrated regularly, and each discharge valve needs maintenance. The maintenance workload is large, and the requirements for technical personnel are also higher.

   

  3. The 'standby' waste of aggregate scale

  Core Disadvantage: For aggregates with large particles, good flowability, and relatively low precision requirements, using high specification independent scales sometimes appears to be "overestimating".

  Specific manifestations: From a purely technical perspective, equipping bulk materials such as sand and stone with independent weighing systems with the same accuracy as cement may not necessarily result in a proportional increase in accuracy benefits and high costs in certain application scenarios. This is a premium paid for the ultimate.

  III. Combination weighing: The technique of balance requires trade-offs

   

  Combination weighing is the mainstream choice in the market, but it is the result of weighing and comes with the disadvantage of compromise.

   

  1. There is still a cumulative error in the weighing of aggregates

  Core Disadvantage: It inherits the core defect of cumulative weighing in the aggregate process.

  Specific manifestation: In the "aggregate accumulation scale", sand, stone, etc. still need to be weighed sequentially, so there is still a risk of error accumulation and cross contamination between them. Although aggregates account for a relatively large proportion of the total weight and the absolute error ratio of individual aggregates is relatively small, this is still a technical shortcoming that needs attention for high-strength grades or concrete with strict requirements for aggregate grading.

   

  2. The system complexity is between the two, but still not low

  Core Disadvantage: It is not a "simple" system.

  Specific manifestation: It includes two subsystems: independent weighing (powder, liquid agent) and cumulative weighing (aggregate). This means that it not only has the partial complexity of independent weighing (requiring maintenance of multiple powder scales and liquid scales), but also retains the inherent disadvantage of cumulative weighing in aggregate weighing. The difficulty of its design and debugging is higher than pure cumulative weighing.

   

  3. The accuracy level is a 'mixture' rather than a 'unity'

  Core disadvantage: The weighing accuracy of the entire station is inconsistent.

  Specific performance: You will receive high-precision powder and liquid weighing, but can only accept medium precision aggregate weighing. For users who pursue the highest precision standards for all materials, this' discount 'is unacceptable. Its accuracy level depends on its weakest link - the aggregate accumulation scale.

   

  Summary and Decision Perspective

  |Weighing method | Core disadvantage | Main risks brought about|

  |Cumulative weighing | Accumulated errors, no guarantee of accuracy | Concrete quality risk (strength, durability)|

  |Independent weighing|High initial investment and operating costs | Project economic risks, long investment return cycle|

  |Combination weighing | Accumulated errors and pollution in the aggregate process | Potential quality fluctuation risk, inconsistent accuracy|

  Choosing which weighing method to use is essentially a trade-off between risk and cost.

   

  Choosing cumulative weighing, you are trading huge quality risks for low costs, which is no longer advisable in modern engineering.

  By choosing independent weighing, you are completely eliminating precision and pollution risks at a high cost, pursuing the ultimate.

  By choosing a combination weighing method, you are significantly reducing costs with a controllable and relatively small quality risk (aggregate error). This is a pragmatic business and technical trade-off aimed at the mainstream market.

   

  Understanding these disadvantages can help you ask the right question: "Can I afford the cost of independent weighing?" If the answer is negative, then "Can I accept a compromise on the accuracy of combined weighing on aggregates?"- For the vast majority of commercial concrete production, the answer to this question is usually "yes" , which is why combined weighing has become mainstream in the market.