Shotcrete, gunite or sprayed concrete is concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique, first used in 1914. It is typically reinforced by conventional steel rods, steel mesh, or fibers. Shotcrete is usually an all-inclusive term for both the wet-mix and dry-mix versions. In pool construction, however, shotcrete refers to wet mix and gunite to dry mix. In this context, these terms are not interchangeable. Shotcrete is placed and compacted at the same time, due to the force with which it is ejected from the nozzle. It can be sprayed onto any type or shape of surface, including vertical or overhead areas
Methods of Application – Dry Mix or Wet Mix Processes
Although both wet and dry shotcrete have specific benefits, advancements in both material and equipment technology make both processes almost interchangeable. In most applications, the preferred method is determined by
1- Economics;
2- Availability of material and equipment;
3- Site access; and
4- The expertise and preference of the contractor.
Today, rebound levels, dust levels, and properties such as bond strength, compressive strength, and durability can be similar whether the wet or dry method is used.
Shotcrete Applications
1- Thin overhead vertical or horizontal surfaces.
2- Curved or folded sections like tunnels, canals, reservoirs, or swimming pools, and pre-stressed tanks.
3- Stabilized rock slopes.
4- Restoration and repairing of old building and fire-damaged structure.
5- Waterproofing walls etc.
Advantages
Shotcrete is very useful and has great advantages over conventional concrete in a new variety of construction and repair works.
1- Excellent bonding in nature makes the concrete layers very strong.
2- It is more economical than conventional concrete and requires less formwork.
3- The Concrete can be applied by a nozzle from a safe distance.
Disadvantages
1- The production cost is very high.
2- Dusting problems.
3- So many wastages of concrete.
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