What are the types of concrete spraying? Concrete spraying techniques can be categorized based on material mixing methods, equipment types, and construction characteristics. The four main types are as follows:
1. Dry Spray Method
Characteristics:
Material Mixing: Cement, aggregate, and accelerator are dry-mixed in proportion and transported to the nozzle via compressed air, where water is added.
Advantages: Simple equipment (such as a dry sprayer), long transport distance (up to 150–200 meters), suitable for lightweight porous aggregates.
Disadvantages: High dust concentration at the nozzle, high rebound rate (approximately 40–50%), and difficult water-cement ratio control.
2. Damp Spray Method
Characteristics:
Material Mixing: Aggregate is pre-wetted (with 5–8% moisture content) before mixing with cement and then sprayed.
Advantages: Reduces dust compared to dry spraying (about 60 mg/m³), and equipment is similar to dry sprayers (dual-use dry/damp sprayers).
Disadvantages: Still has a certain rebound rate (around 15–25%) and challenges in water-cement ratio control.
3. Wet Spray Method
Characteristics:
Material Mixing: Cement, aggregate, and water are fully mixed into a wet mixture before being transported through a wet sprayer, with an accelerator added at the nozzle.
Advantages: Low dust, low rebound rate (below 15%), and stable concrete quality with controlled water-cement ratio.
Disadvantages: Complex equipment (requires power-driven transport), prone to pipeline blockage, and higher cost.
4. Hybrid Spray Method (SEC Method)
Characteristics:
Material Mixing: Materials are added in stages, first mixing cement-coated sand mortar, then combining it with aggregate before spraying, integrating both dry and wet spraying techniques.
Advantages: Further reduces dust and rebound rate while improving concrete homogeneity.
Disadvantages: Complex equipment (requires a mortar pump and sprayer), more intricate operation, and mainly used for large-section projects.
Additional Notes
Mainstream Application: The wet spray method has become the dominant choice due to its environmental benefits and stable quality (e.g., tunnel support and slope reinforcement).
Equipment Classification: Sprayers can be categorized into piston-type, screw-type, and rotor-type based on structure, with rotor-type wet sprayers being the most widely used.