• Shotcrete is a concrete conveyed pneumatically through a hose and projected at high velocity on to a surface.
  • The force of the concrete impacting on the surface compacts the mixture.
  • It is commonly used for repair work, thin layers or fibre-reinforced concrete layers.
  • Shotcreting is also commonly known as Guniting. Guniting is the process of conveying desired mixture of dry cement and sand through a hole and depositing the same on the surface to be treated under pressure with just sufficient quantity of water for hydration. The material deposited by this process is called GUNITE.

Basically Gunites are of two types:

High velocity gunites- High velocity gunite is produced by using a small nozzle and high pressure air, resulting in impact velocities of 90 to 120 m/sec.

Low velocity gunites- A wide nozzel with large output machine is used. Such gunite is not as well compacted as high velocity gunite, still with low water cement ratio and high cement content, adequate in-situ compaction can be achieved.

Applications:

• Renovation of plain or RCC structures deteriorated due to weather, bad workmanship etc.
• Strengthening of old structures.
• Lining of water reservior, canals etc.
• Water proofing on the surface which directly comes in contact with water.
• Removal of leakage with rich cement mix after guniting is done in leaking surfaces.
• For protection of exposed pre-stressed wires in structures like chimneys, concrete pipes etc.

Merits:

• Specific gravity of gunited concrete is about 2.16 to 2.18, which is much higher than any concrete done by any other method.
• Gunited concrete makes a perfect bond between the concrete and masonary surfaces.
• Gunited concrete is more resistant to weather and chemical action than ordinary concrete.