In today's infrastructure projects, concrete mixing plants play a vital role. With the continuous development of science and technology, the status of concrete mixing plants in the construction industry is becoming increasingly prominent. It can not only improve the quality of projects, but also speed up project progress and reduce project costs.
1. Meaning of Concrete Mixing Plant
Concrete mixing station, also known as concrete mixing station, is a special facility for efficiently mixing various materials to produce concrete. Concrete mixing station is mainly composed of five major systems, including mixing host, material weighing system, material conveying system, material storage system and control system, and other ancillary facilities. Concrete mixing station is a joint device used for centralized mixing of concrete, also known as concrete prefabrication site. Due to its high degree of mechanization and automation, the productivity is also high, and it can ensure the quality of concrete and save cement. It is often used in large and medium-sized water conservancy, power, bridge and other projects with large concrete engineering volume, long construction period and concentrated construction sites. With the development of municipal construction, the mixing station that adopts centralized mixing and provides commercial concrete has great advantages, so it has been rapidly developed, and has created conditions for promoting concrete pumping construction and realizing the joint operation of mixing, conveying and pouring machinery.
2. Classification of Concrete Mixing Plant
- According to the type, concrete mixing stations are divided into two categories: fixed mixing stations and mobile mixing stations. This is also the first classification that many manufacturers distinguish during production. Most fixed mixing stations also adopt a modular and easy-to-join design. They are mainly used in large-scale commercial concrete manufacturers or manufacturers related to concrete components. They can be used in large-scale engineering construction. The characteristics are strong production capacity, stable operation and good anti-interference. The mobile mixing station is towed by a trailer unit, with good mobility, making production more flexible. It is generally used in various small and medium-sized temporary construction projects, and can be rented or used for self-use.
- According to the purpose, it can be divided into commercial concrete mixing stations and engineering concrete mixing stations. Commercial mixing stations are concrete mixing stations mainly for commercial purposes. They should be efficient and economical, and meet environmental protection requirements. Engineering mixing stations are for self-use purposes, and whether they are in line with their own projects should be considered.
- According to the layout process, it is generally divided into one-stage and two-stage. The first-stage refers to lifting sand and gravel aggregates, cement, etc. to the top silo of the mixing station at one time. Various materials are carried out from top to bottom according to the production process, and finally discharged from the bottom. It is more common in mixing buildings. Such a mixing station is divided into a silo layer, a weighing layer, a mixing layer, and a discharging layer from top to bottom. The mixing efficiency is very high, but the construction is difficult, the demolition is inconvenient, and the investment cost is high. Compared with the first-stage, the second-stage weighs the aggregate and then lifts the mixer again. Although it occupies a large area and the mixing efficiency is slightly lower than the first-stage, it is easy to disassemble and assemble, has low manufacturing cost, and is easy to install. It is widely used, and the production capacity of the improved second-stage mixing station is comparable to that of the first-stage.
- According to the number of mixers, the mixing station can be divided into a single-host station and a dual-host mixing station.The model name of the dual-host mixing station is 2HZS series concrete mixing station. For example, the 2HZS25 concrete mixing station means that the theoretical productivity of the dual-host mixing station with two JS500 mixing hosts is 2*25m³/h. The dual-host mixing station is a good supplement to the same model mixing station.
- According to the weighing method, it can be divided into independent weighing and cumulative weighing. Individual weighing will equip each material with a separate weighing unit. After weighing each material, it will be added to the mixer for mixing. This weighing method has high precision, but the design is complex and the cost is high. Cumulative weighing is to add all aggregates into a unified hopper, which is more likely to cause error accumulation, which is not good for the final production. Moreover, the more batching bins there are, the more likely there will be deviations. It is not suitable for large-scale projects. However, the structural design is simple and the cost is low.
3. Features
Concrete mixing station is a building material manufacturing equipment composed of five major systems: mixing host, material weighing system, material conveying system, material storage system, control system and other ancillary facilities. Its main working principle is to use cement as a binder, mix and mix raw materials such as sand, lime, and coal slag, and finally make concrete, which is put into construction and production as a wall material. Since it was put into use, the concrete mixing station has always played an important role in my country's construction and building materials industry. Of course, this is also determined by the superior characteristics of the concrete mixing station itself.
The concrete mixing station is mainly divided into four parts: sand and gravel feeding, powder feeding, water and admixture feeding, transmission mixing and storage. The whole equipment is cast with an integral steel structure. The high-quality H-shaped steel not only has a beautiful appearance, but also strengthens the overall structural strength of the concrete mixing station. The equipment is easy to install and can be applied to various complex terrain structures.
The concrete mixing station has good mixing performance. The equipment adopts a spiral double-horizontal shaft forced mixing host. Not only is the mixing machine strong, but it can also achieve good mixing effects for dry hardness, plasticity and various proportions of concrete. And the mixing is uniform and efficient.
The concrete mixing station not only has excellent mixing host, but also has various excellent accessories, such as screw conveyor, metering sensor, pneumatic components, etc. These components ensure the high reliability, accurate metering skills and long service life of the concrete mixing station during operation. At the same time, each maintenance part of the concrete mixing station is equipped with a walkway or inspection ladder, and has sufficient operating space. The mixing host can be equipped with a high-pressure automatic cleaning system, with functional oil shortage and over-temperature automatic alarm function, which is convenient for equipment maintenance.
The concrete mixing station has good environmental protection performance. During the operation of the machine, the powder operation is carried out in a fully enclosed system. The powder tank adopts high-efficiency dust collector/mist spray and other methods to greatly reduce the pollution of dust to the environment. At the same time, the concrete mixing station uses silencers for the pneumatic system exhaust and unloading equipment to effectively reduce noise pollution.
4. Concrete Mixing Plant Components
Concrete mixing station is mainly composed of five systems including material storage system, material weighing system, material conveying system, mixing system, powder storage system, powder conveying system, powder metering system, water and admixture metering system and control system, as well as other ancillary facilities.
- Mixing Host
Mixing main machine is divided into forced mixing and self-falling mixing according to its mixing method. Forced mixer is the mainstream used in mixing stations at home and abroad. It can mix various types of concrete such as fluidity, semi-hardness and hardness. Self-falling mixer is mainly used to mix fluidity concrete and is rarely used in mixing stations.
Forced mixer is divided into main shaft planetary mixer, single shaft mixer and double shaft mixer according to the structural form. Among them, the double shaft forced mixer has the best comprehensive performance.
- Weighing System
The material weighing system is a key component that affects the quality of concrete and the cost of concrete production. It is mainly divided into three parts: aggregate weighing, powder weighing and liquid weighing. Generally speaking, mixing stations with a capacity of less than 20 cubic meters per hour adopt a superimposed weighing method, that is, aggregates (sand and stone) are weighed with a scale, cement and fly ash are weighed with a scale, water and liquid admixtures are weighed separately, and then the liquid admixtures are put into the water weighing bucket for pre-mixing. In mixing stations with a capacity of more than 50 cubic meters per hour, the method of weighing each material independently is mostly adopted, and all weighing is controlled by electronic scales and microcomputers. The weighing accuracy of aggregates is ±2%, and the weighing accuracy of cement, powder, water and admixtures is ±1%.
- Conveying System
Material transportation consists of three parts:
1. Aggregate transportation: There are two ways of transportation in mixing stations: hopper transportation and belt transportation. The advantages of hopper lifting are small footprint and simple structure. The advantages of belt transportation are large transportation distance, high efficiency and low failure rate. Belt transportation is mainly suitable for mixing stations with aggregate temporary storage bins, thereby improving the productivity of mixing stations.
2. Powder transportation: The powder materials available for concrete are mainly cement, fly ash and mineral powder. The commonly used powder conveying method is screw conveyor conveying, and large mixing plants use pneumatic conveying and scraper conveying. The advantages of screw conveying are simple structure, low cost and reliable use.
3. Liquid conveying: mainly refers to water and liquid admixtures, which are conveyed by water pumps respectively.
- Storage System
The storage methods of materials available for concrete are basically the same. Aggregates are piled in the open air (there are also closed silos for large commercial concrete mixing stations in cities); powders are stored in fully enclosed steel structure silos; admixtures are stored in steel structure containers.
- Control System
The control system of the mixing station is the central nervous system of the entire set of equipment. The control system has different functions and configurations according to different user requirements and the size of the mixing station. Generally, the control system of small mixing stations available on the construction site is simpler, while the system of large mixing stations is relatively complex.
5. Future Development
Informatization and digitalization are important directions for the future development of concrete mixing plants. By introducing technologies such as the Internet of Things, big data, and cloud computing, the informatization and digital management of concrete mixing plants can be realized, the accuracy and real-time nature of production data can be improved, and more scientific and effective support can be provided for production and management. In addition, digital technology can be used to simulate and optimize the production process to improve production efficiency and product quality.
