Shotcrete, guniteor sprayed concrete can be defined as a technique in which mortor or concrete is passed through hose and pneumatically projected at high velocity onto a surface.
Carl Akeley in 1907 is first person to found out about this technique.
Steel rod ,Steel mesh and fibre are some of material which is used to reinforced.
Both the dry mix and wet mix can be referred as shotcrete which is invented by Carl Akeley.
But while pool construction wet mix can be termed as shotcrete and granite to dry mix.
Shotcrete is a technique in which it is placed and compacted at a same time because the force at which it is poured out from the nozzle.
It can be used on any shape of surface whether it is vertical or overhead area.
History
Shotcrete which is that time known as guniting was discovered bye American Carl Akeley in 1907 , he was repairing crumbling facade of the field Columbian museum.
He then used the technique of puffing dry material out of hose with compressed air,While inserting water at the nozzle. After that in 1911 patent was granted for his inventions and equipment which is used was 'cement gun' and material that was produced 'gunite'.
Dry mix process was the one technique which continuously used until 1950 and then wait mix process was invented. Alternate method for Gunning with the dry material was introduced in 1960 which is with the help of rotary gun.
Generally for the small works nozzle can be handled by work man,but for larger work it needs to be attached to mechanical arm and which can be controlled by remote controls.
Dry mix vs wet mix:-
In the dry mix method, the dry ingredients need to be placed into the hooper and then convey pneumatically through a hose to the nozzle.
Water can be controlled at the nozzle by the nozzle man but water and dry mixture is not still completely mixed it will be mixed when it hits receiving surface.
For thick and heavily reinforced section you need skilled nozzleman.
In a dry mix process nozzleman can control the water content so instantly so more effective placement in overhead and vertical application can be made without using accelrator.
Dry mix process frequently used in a repair works where it it needs to stop the work regularly so dry material is easily poured out from the hose.
In wet mix concretethe already prepared concrete which is also called as ready mix concrete is pumped through nozzle and compressor air is also introduce for better mixture at receiving end.
One of the advantage of wet mix concrete is that it produces less waste when the material fall from the surface and dust is also very less as compared to dry mix.
The greatest advantage of weight mix concrete is that all the ingredients are combined with water and more volume can be placed on the surface as compared to dry process concrete.
Shotcrete machines
Complete process of shotcreting is controlled by shotcrete machines and make it fast and easy. Traditionally for wet mix concrete it is applied by machine but sometimes manual method can also be used.
Shotcrete machines are available which control the complete process and make it very fast and easy. Manual and mechanical methods are used for the wet spraying process but wet sprayed concrete is traditionally applied by machine.
Continuous concrete flow which is as constant as possible is required so as guaranteed homogeneous spray application.
Application:
Mines ,Subways line tunnel walls, automobile tunnels are some of the common example for the the use of Shotcrete.
E.g Maramaray tunnel
Shotcrete can be used for both permanent and temporary excavation. it can also be used to stabilize excavation for underground parking structure and high rise construction. Large structure can be erected so waterproofing can be controlled. After the structure is completed from foundation to short crete the area is compacted.
For placing structural concrete it is common method of work.
Shotcrete is one of the very useful method in the mining particularly hard rock, in which the heavy machinery miners and materials need to go underground for movement. It can help to make safe Path from ground fall.
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