Dry Concrete Batching Plants

A dry concrete batching plant (also known as a dry mix plant) is specialized equipment for producing dry-mix concrete (a mixture of dry materials, mixed on-site with water). Its structure and functionality are designed around the precise proportioning and uniform mixing of dry raw materials. A key feature of a dry concrete batching plant is that it lacks a separate mixing unit. The mixing process is not performed within the plant, but rather relies on the drum agitation of a concrete mixer truck.

I. Core Structural Components

The core of a dry mix concrete batching plant is to achieve “precise proportioning and centralized batching of dry raw materials.” Its structure is based on a “storage – conveying – weighing – unloading” process, excluding the in-plant mixer. Specifically, it includes:

1. Raw Material Storage System

– Powder Silo (cement, fly ash, etc., equipped with a level meter, arch breaking device, and dust removal port);

– Aggregate Silo (sand, stone, etc., separated by particle size, with a bottom discharge control device);

– Dry Admixture Silo (e.g., powdered accelerator, separate small silo with screw conveyor).

2. Raw Material Conveying System

Responsible for conveying raw materials from the storage silo to the weighing system, and then collectively transporting the weighed dry materials to the concrete mixer truck.

– Powder conveying: A screw conveyor (enclosed to reduce dust) transports the powder from the powder silo to the powder weighing hopper.

– Aggregate conveying: A vibrating feeder or belt conveyor transports the aggregate from the aggregate silo to the aggregate weighing hopper.

– Total discharge conveying: All weighed dry materials (aggregates + powder + admixtures) are discharged into the drum of the waiting concrete mixer truck via a collection hopper or inclined conveyor.

3. Weighing System

Core function is to accurately measure each dry material according to the recipe (with an error of ≤±1%), providing the foundation for subsequent mixing in the concrete mixer truck. It includes:

– Aggregate scale (weighing sand and stone);

– Powder scale (weighing cement, fly ash, etc.);

– Dry admixture scale (weighing dry admixtures).

All weighing devices are linked to the control system via sensors to ensure accurate mixing ratios.

4. The Control System

Based on a PLC, offers the following functions:

– Preset/call recipes (storing dry material mix ratios for concrete of different strength grades);

– Automatic control of the timing and values of each silo’s unloading, conveying, and weighing;

– Real-time display of weighing data and error correction;

– Linked to the concrete mixer truck’s unloading signal (ensuring accurate unloading of dry materials into the mixer truck);

– Recording of production data (output, recipe, time, etc.).

5. Auxiliary Systems

Dust Removal System: Connects to dust-generating points such as the powder silo, weighing hopper, and discharge port, controlling dust through bag filters;

– Compressed Air System: Provides power for pneumatic gates and discharge valves;

– (Optional) Aggregate Screening Equipment: Removes oversized impurities;

– Control Room: Integrated control system and monitoring equipment, allowing operators to coordinate production and mixer truck scheduling.

II. Core Functions

– Precise Dry Material Proportioning:

Through the coordinated efforts of storage, conveying, and weighing systems, dry raw materials such as sand, stone, cement, and fly ash are precisely mixed according to a pre-set formula (physical mixing, not forced mixing), resulting in a uniform dry material composition (without water or with only a trace amount of moisture to prevent moisture).

– Truck Mixer Collaboration:

The mixed dry materials are directly discharged into the drum of the concrete mixer truck, and the mixing process is completely performed by the truck. During transportation to the construction site, or upon arrival, a predetermined amount of water is added via the truck’s built-in water injection system. The drum rotates to forcefully mix the dry materials and water, ultimately forming pourable concrete.

– Flexible Adaptability to Small and Medium-Sized Applications:

Eliminating the need for an on-site mixer, the system offers a simpler structure, smaller footprint, and lower investment costs. It is suitable for projects with low concrete demand and moderate transportation distances (ensuring sufficient time for the truck mixer to complete mixing), such as rural construction and small-scale municipal maintenance.

– Automated Production and Environmental Protection:

A control system enables automated batching, reducing manual labor; a dust removal system controls dust pollution and meets environmental requirements.

III. Key Differences from Wet Concrete Batching Plants

– Wet concrete batching plants: Equipped with a forced mixing unit, raw materials (including water) are mixed within the plant, producing pourable concrete directly. The concrete is then unloaded into a concrete mixer truck for transportation only (no mixing occurs).

– Dry mix concrete batching plants: The plant lacks a concrete mixer and only mixes dry materials. The concrete mixer truck serves as both a “transporter” and “mixer,” adding water and mixing during transportation or on-site.

Dry concrete batching plants utilize a closed-loop “storage – transport – weighing – mixing” system, combined with automated control, to achieve efficient and precise production of dry mixes. They provide high-quality raw materials for on-site water mixing and are widely used in small and medium-sized construction projects, road maintenance, and other applications.