Shotcrete is a method of applying concrete or mortar pneumatically projected or sprayed with the help of nozzle having high velocity on the prepared surface.

Shotcrete is also called Gunite or sprayed concrete.

It is typically reinforced by steel, rods, steel mesh or fibres. It is placed and compacted or consolidated with the force with which it is ejected at the same time. It can be sprayed at any shape and type of surface.


Types of the Shotcrete Process

Dry-Mix Process

The dry mix process involves placing the dry ingredients into a hopper. And this mix is then conveyed pneumatically through a hose to the nozzle. The addition of water at the nozzle is controlled by Nozzleman. The water and the dry mixture is not mixed completely, but it is completed when the mixture hits the receiving surface. A skilled nozzleman is required, especially in the case of thick or heavily reinforced sections. The dry mix process has an advantage of the water content. It can be adjusted immediately by the nozzleman, allowing more effective placement in overhead and vertical applications without using accelerators. The dry mix process is useful in repairing works when it is necessary to stop frequently, as the dry material is easily discharged from the hose.


Wet-Mix Process

Wet-mix shotcrete consists of pumping the already prepared concrete, typically ready-mixed concrete, to the nozzle. Compressed air is introduced at the nozzle to compel the mixture onto the receiving surface. The wet-process procedure normally produces less dust, rebound and waste compared to the dry-mix process. The greatest advantage of the wet-mix process is that all ingredients are mixed with the water and additives and also larger volumes can be placed in less time than the dry process concrete.

Applications of Shotcrete

  1. It is used for stabilized rock slopes.
  2. It is used for repairing and restoration work.
  3. It is used in a thin overhead vertical and horizontal surface.
  4. It is used for waterproofing walls.
  5. It is used in curved and folded sections like canals, tanks, tunnels etc.
  6. Used in hard rock mining.

Shotcrete Machines

shotcrete machines are the machines that control the complete process. It is very fast and easy. Both Manual and mechanical methods are used for the wet spraying process. traditionally, wet sprayed concrete is applied by a machine. To mechanised the work, it requires high spray outputs and large cross-sections. To work with wet mixes, Concrete spraying systems with duplex pumps are mainly used. Distinct from conventional concrete pumps, these systems have to meet the further requirement of delivering a concrete flow that is as constant as possible and therefore continuous to guarantee homogeneous spray application.

Advantages of Shotcrete

  1. It has excellent bonding, makes concrete layers very strong.
  2. It is more economical.
  3. It requires less formwork.
Disadvantages of Shotcrete
  1. Cost of production is more.
  2. It has more wastage of concrete.
  3. It has a problem of dusting.

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