Shotcrete is a generic term for spray-application of concretes, referring to both the wet or the dry application method. Gunite is a specific term referring to dry concrete applied using pressurised air, where mixing with water occurs at the nozzle, as it is applied. The Gunite technique allows a skilled worker to add precisely the correct amount of water to obtain the required viscosity for application to both vertical or horizontal surfaces (overhead), and so it can develop the required strength for the final product.
Shotcrete is commonly used to line tunnel walls, in mines, subways, and automobile tunnels. Fire-resistant shotcrete developed in Norway is used on the Marmaray tunnel in Istanbul.
Shotcrete is used to reinforce both temporary and permanent excavations. It may be employed, in concert with lagging and other forms of earth anchor, to stabilize an excavation for an underground parking structure or hi-rise during construction. This provides a large waterproof enclosure in which a structure can be erected. Once the structure is completed the area between its foundation and the shotcrete is backfilled and compacted.
Shotcrete is also a viable means and method for placing structural concrete.
Shotcrete is very useful in hard rock mining. Development of decline pathway to go underground is critical for movement of heavy machinery, miners, and material. Shotcrete helps make these paths safe from any ground fall.
In-ground swimming pools can use either the wet or dry application method. Shotcrete-wet is ideal for covering large areas quickly, whereas shotcrete-dry (Gunite) is more useful for frequent start-and-stop operations. Neither is superior for this application, and the technique should be selected based on individual project needs.
Costs vary depending on project needs.Shotcrete swimming pools are typically more durable and longer lasting than poured concrete. Poured concrete can have a compressive strength of 2,500-3,000 psi, whereas shotcrete exceeds 4,000 psi. Additionally, the use of Shotcrete allows for customization in shape, depth, and styles that are not typically available in traditional pool kits.Shotcrete pools can also have many different types of finishes including tile, quartz, or glass beading.
