Sprutbetong

Sprutbetong, or shotcrete, is a cementitious material that is conveyed through a hose and pneumatically projected onto a surface to form a dense, structurally bonded layer. It can be applied in two main processes: wet-mix, where a ready-made slurry is pumped; and dry-mix, where dry cement and aggregate are fed into the nozzle and water is added at the nozzle.

Commonly used for tunnel linings, slope stabilization, rock support in mining, dam rehabilitation, underwater works, and architectural façades and pool shells. It allows application on vertical or overhead surfaces without formwork, and can provide rapid early strength.

Mixes typically include Portland cement, aggregates (sand and small gravel), water, and optional admixtures or fibers to improve bonding, workability, toughness or corrosion resistance. Additives such as accelerators can speed setting; plasticizers improve pumpability. Fibers (steel, glass, or polypropylene) may be included. Curing is important to avoid cracking.

The spray technique requires skilled nozzle operators, proper surface preparation, and control of rebound and thickness. Finishing may include troweling or planning; rebound material can be recycled. Quality is evaluated via compressive strength tests, adhesion, and thickness checks in accordance with standards.

Standards and guidelines exist worldwide, such as EN 14487-1 for shotcrete and ACI 506 for sprayed concrete. Safety concerns include exposure to silica dust, high-velocity spray, and noise; operations require PPE, ventilation, and risk management.