In the entire production process of an asphalt mixing plant, weighing is a core link between raw material preparation and mixing. Its accuracy directly affects whether the mix proportions meet design requirements. Mix proportion accuracy not only affects operability during construction but also determines the durability and overall service life of the road.
- A high aggregate ratio → The pavement lacks cohesion, potentially leading to cracks and structural damage within a few years;
- An excessive asphalt ratio → It easily softens and deforms under high temperatures, causing rutting and even surface runoff.
While traditional single-stage weighing can meet the needs of foundation construction, the rise of high-grade projects such as expressways, airport roads, and heavy-duty freight roads has led to increasingly demanding mix proportion accuracy. Primary weighing is often affected by factors such as falling material inertia, conveyor belt residue, and temperature and humidity fluctuations, leading to inevitable errors.
Secondary dynamic weighing technology was developed precisely to meet these industry needs. By adding dynamic detection and automatic compensation steps after the initial weighing, it ensures accurate and stable mix proportions between batches even under high-speed continuous production conditions, thereby reliably ensuring the final quality of the asphalt mixture.
Secondary dynamic weighing system improves proportioning accuracy
As previously mentioned, secondary dynamic weighing technology is a key means of ensuring mix accuracy in asphalt production and is essential for guaranteeing the quality of the finished product. So, how does it achieve this goal? Below, we’ll delve deeper into the system’s composition and operation.
Key Components
A secondary dynamic weighing system adds real-time monitoring and intelligent compensation to primary weighing. Its key components include:
- High-precision sensors: These are installed at key locations along the aggregate, powder, and asphalt conveyor paths. For example, load cells are placed on the weighing bridge beneath the aggregate conveyor belt to monitor the instantaneous weight and flow rate of the aggregate in real time. This ensures stable data even with temperature fluctuations or material moisture levels.
- Dynamic detection module: This consists of a high-speed data acquisition card and a signal amplifier. For example, on the aggregate conveyor belt and asphalt conveyor pipe, the acquisition module transmits sensor signals to the control system in milliseconds, eliminating compensation lags caused by latency.
- Feed control valve: This is installed on the feed lines for aggregate, powder, or asphalt. For example, if the powder level is low, the control valve instantly opens to precisely add a few kilograms of powder. Conversely, if the asphalt level is slightly above the specified level, the valve quickly closes to prevent overdosing.
- Intelligent algorithm control system (PLC/AI): The PLC is the brain of the entire system, performing real-time comparisons between the target recipe and actual weighing data. For example, when it detects that the aggregate weight is 2% lower than the target value, the algorithm will immediately calculate the weight that needs to be added and issue an instruction to the control valve.
Operational Process
- Initial Weighing: Aggregates, powders, and asphalt are weighed once in the weighing hopper.
- Conveying Detection: Sensors continuously monitor the actual weight of materials as they are conveyed to the mixing tank.
- Error Analysis: The control system compares real-time data with target values.
- Precision Compensation: The control valve instantly opens or closes, automatically adding or removing the appropriate material.
- Final Mixing: By the time the materials enter the mixing tank, the mix ratio has been precisely restored to the designed value.
The key feature of this mode is simultaneous conveying, detection, and correction, enabling secondary precision adjustments without reducing production speed.
Filling Gaps, Breaking Through — Advantages of Secondary Weighing
Before exploring the significant advantages of secondary dynamic weighing technology, we must first understand the basic operating mechanisms and limitations of traditional primary weighing technology.
Primary weighing typically involves a single measurement of aggregate, powder, and asphalt using a weighing hopper before the materials enter the mixing system to ensure that the initial mix proportions meet design requirements. However, this process only provides static weighing data, making it impossible to monitor material flow changes during transportation in real time, nor is it able to dynamically correct for deviations caused by equipment inertia, residue, or environmental factors.
Only by fully understanding the limitations of primary weighing can we fully appreciate why secondary dynamic weighing technology is a key solution for improving mix proportion accuracy.
Main Issues with Single-Stage Weighing Technology
Inertia Effects
After a single weighing operation, materials are conveyed to the mixer via the hopper or conveyor belt. Due to material inertia, over- or under-feeding may occur, resulting in a discrepancy between the weighed value and the actual amount delivered.
Environmental Interference
Fluctuations in temperature and humidity in the production environment, especially fluctuations in the moisture content of the material itself, can affect the readings of the weighing sensor, leading to unstable weighing data and reduced proportioning accuracy.
Accuracy Loss Due to Equipment Wear
Over long-term use, the sensors of the belt scale, the tensioning devices of the belt conveyor, and related mechanical components will wear or loosen, reducing sensor sensitivity. This leads to the gradual accumulation of weighing errors and affects accuracy and stability.
Accumulation of Errors in Continuous Production
Single-stage weighing only weighs materials before they are added, making it impossible to implement dynamic adjustments. As production progresses, errors cannot be corrected in a timely manner, causing proportioning deviations to gradually increase, ultimately affecting the overall quality of the mixture.
Advantages of Secondary Dynamic Weighing
To address the limitations of primary weighing, secondary dynamic weighing technology achieves a quantum leap in mix accuracy and stability by adding real-time monitoring and intelligent compensation. Specific advantages include:
Improved accuracy, meeting high-level engineering requirements
Traditional primary weighing typically has an error of approximately ±1% for aggregates and ±0.5% for powders and asphalt. Macroad‘s secondary dynamic weighing technology reduces aggregate error to ±0.5% and stabilizes the error at ±0.25% for powders and asphalt. This improved accuracy is crucial for the compactness and aging resistance of high-grade roads, such as highways.
Improved adaptability to complex formulations
In complex formulations involving multiple aggregates and mineral powders, secondary weighing can monitor and correct the proportions of each material individually, effectively preventing imbalances caused by cumulative errors, ensuring that each component strictly meets design requirements and improving the overall stability of the mixture.
Real-time dynamic correction to eliminate inertia errors
Using dynamic weighing sensors installed along the conveyor path, secondary weighing monitors material weight changes in real time, promptly detecting over- or under-dosing caused by material inertia and instantly compensating for it.
Strong immunity to environmental interference and stable data
High-precision sensors, combined with signal amplification and filtering technology, effectively suppress the impact of temperature, humidity, and material moisture content fluctuations on weighing results, ensuring continuous and stable data.
Automatic compensation for equipment wear
The intelligent control system analyzes historical data and provides real-time feedback to identify deviations caused by equipment status changes and automatically adjusts compensation strategies, extending equipment life while ensuring weighing accuracy.
Maintaining high accuracy during continuous production
The dynamic weighing mode, which monitors while conveying, enables instant correction of errors between batches, preventing error accumulation and ensuring highly consistent proportions even under long-term, high-load production.
Saving raw materials and reducing costs
Accurate material delivery not only improves product quality but also significantly reduces material waste caused by overdosing, reducing production costs. Taking a mixing plant with a daily output of 800 tons of asphalt as an example, secondary weighing can reduce asphalt waste by about 0.5% per day, which is equivalent to saving 4 tons of asphalt and more than 1,000 tons of raw material costs per year.
The above comparative analysis clearly demonstrates that secondary dynamic weighing technology not only successfully overcomes the shortcomings of traditional primary weighing but also achieves breakthroughs in accuracy, stability, and economic efficiency, becoming a key technical support for batching control in high-grade asphalt mixing plants.
Furthermore, Macroad’s series of asphalt mixing plants have successfully integrated a mature secondary dynamic weighing system. Leveraging its high-precision sensors and intelligent algorithms, it ensures a stable mix ratio in every batch, meeting the requirements of various project grades.
Secondary Dynamic Weighing Seamlessly Integrated with Asphalt Plant System
Secondary dynamic weighing technology doesn’t operate in isolation; instead, it collaborates deeply with multiple key systems within the asphalt mixing plant to create an efficient and accurate production closed loop. This inter-system collaboration not only ensures accurate mix proportions but also improves overall mixing quality and production efficiency.
Cold material supply system
Responsible for initial batching according to design requirements, providing a stable material base for primary weighing and subsequent secondary dynamic weighing.
Hot material elevator and conveyor belt
As key channels for material transportation, they not only carry large amounts of material but also provide a stable conveying environment for dynamic monitoring by the secondary weighing sensors, ensuring accurate data collection.
Mixing unit
Receives materials precisely proportioned by secondary dynamic weighing, achieving uniform, high-quality mixing and ensuring that the final asphalt mixture meets design standards.
Intelligent control system (PLC/AI)
By integrating secondary weighing technology with the Internet of Things (IoT), remote monitoring, real-time analysis of production data, abnormality alarms, and complete production record traceability are achieved, ensuring digital upgrades in production safety and quality management.
The efficient collaboration of this series of systems forms a complete closed-loop quality control chain. Secondary dynamic weighing technology, as the core link, ensures precise adjustment of mix proportions and consistent mixing quality, laying a solid foundation for the efficient and intelligent operation of modern asphalt mixing plants.
Industry comparison: Who needs secondary dynamic weighing more?
With the outstanding performance of secondary dynamic weighing technology in mix accuracy and production stability, its application value is becoming increasingly significant in various types of road projects. To better understand the practical impact of this technology, we need to analyze the different requirements for weighing technology in various road projects from the perspective of project needs, thereby clarifying which areas are most in need of secondary dynamic weighing systems.
| Basic municipal roads: | Primary weighing generally meets the needs of foundation construction, but in areas with high humidity or large fluctuations in material moisture content, secondary weighing can significantly improve mix stability and construction quality. |
| Expressways and high-grade highways: | The requirements for material mix accuracy are extremely stringent, and secondary dynamic weighing technology has become an industry standard for ensuring mix quality. |
| Airport roads: | Because asphalt mixtures must possess extremely high shear resistance and high-temperature resistance, any mix deviation can cause structural damage, making secondary weighing technology essential in airport road projects. |
| Roads in high-altitude and cold regions: | Low temperatures weaken the bond between asphalt and aggregate, necessitating even higher requirements for mix accuracy. Secondary weighing technology can effectively ensure material performance and pavement durability. |
The upgrade path of secondary dynamic weighing technology
Secondary dynamic weighing technology not only improves the current mix accuracy of asphalt mixing plants, but also becomes an important support for promoting intelligent production and digital management to a new stage. With the continuous advancement of artificial intelligence, big data and automation technology, the extended value and future trends of secondary weighing are mainly reflected in the following aspects.
Deep Integration with AI Predictive Maintenance
The real-time material weighing data collected by the secondary weighing system not only reflects the accuracy of production proportions but also reveals subtle changes in equipment operating status. AI algorithms analyze this data to promptly identify potential risks such as equipment wear and sensor degradation. This enables predictive maintenance, avoids sudden failures, extends the life of critical components, and significantly reduces maintenance costs and the risk of production downtime.
Seamless Integration with Big Data Quality Management Platforms
The precise data generated by the secondary dynamic weighing system can be integrated into the big data platform, forming a full lifecycle quality data chain covering formulation design, weighing control, mixing, construction implementation, and maintenance management. Through data integration and analysis, managers can achieve quality traceability, process optimization, and risk warning, thereby improving overall project management and construction quality.
Towards Fully Automated Unmanned Intelligent Production
In the future, secondary weighing systems based on AI self-learning algorithms will be able to predict environmental changes. They will be able to proactively assess potential impacts of temperature, humidity, and material properties on weighing accuracy and automatically adjust initial weighing parameters, achieving truly dynamic intelligent batching. With the help of automated equipment and remote monitoring technology, asphalt mixing plants will gradually achieve unmanned production, greatly improving production efficiency and safety, and pushing the industry into a new era of intelligent manufacturing.
Secondary dynamic weighing technology is not only a hardware upgrade, but also an innovation in production philosophy. It enables asphalt mixing plants to maintain accurate, stable, and low-cost production despite the diverse environments, materials, and high-precision engineering requirements.
Faced with increasingly complex engineering requirements and changing construction environments, secondary dynamic weighing technology makes efficient and stable work possible, ensuring that every road can bear the heavy responsibility of the future. It is this power of precise control that drives the industry forward and lays a solid foundation for modern intelligent transportation.