Shotcrete
Encyclopedia
Shotcrete is concrete
(or sometimes mortar
) conveyed through a hose and pneumatically
projected at high velocity
onto a surface, as a construction technique.
Shotcrete is usually an all-inclusive term; gunite is a term sometimes used for some dry-mix types.
Shotcrete undergoes placement and compaction at the same time due to the force with which it is projected from the nozzle. It can be impacted onto any type or shape of surface, including vertical or overhead areas.
, used to fill plaster model of animals. He used the method of blowing dry material out of a hose with compressed air
, injecting water at the nozzle as it was released. This was later used to patch weak parts in old buildings. In 1911, he was granted a patent for his inventions, the "cement gun", the equipment used, and "gunite", the material that was produced. Until the 1950s when the wet-mix process was devised, only the dry-mix process was used. In the 1960s, the alternative method for gunning by the dry method was devised with the development of the rotary gun, with an open hopper that could be fed continuously. Shotcrete is also a viable means and method for placing structural concrete.
The nozzleman is the person controlling the nozzle that delivers the concrete to the surface. The nozzle is controlled by hand on small jobs, for example the construction of small swimming pools. On larger work the nozzle
can sometimes be held by mechanical arms where the nozzleman controls the operation by a hand-held remote control.
Wet-mix shotcrete involves pumping of a previously prepared concrete, typically ready-mixed concrete, to the nozzle. Compressed air is introduced at the nozzle to impel the mixture onto the receiving surface. The wet-gun procedure generally produces less rebound, waste (when material falls to the floor), and dust compared to the dry-mix procedure. The greatest advantage of the wet-mix process is that larger volumes can be placed in less time.
with either a dry or wet mix process. However, it may also sometimes be used to distinguish from gunite as a wet-mix. The term shotcrete was first defined by the American Railway Engineers Association (AREA) in the early 1930s. By 1951, shotcrete had become the official generic name of the sprayed concrete process.
Gunite refers only to the dry-mix process, in which the dry cementitious mixture is blown through a hose to the nozzle, where water is injected immediately before application. Gunite was the original term coined by Akeley
, trademark
ed in 1909 and patented in North Carolina
. The concrete is blasted by pneumatic pressure from a gun, hence "gun"-ite.
The term "Gunite" became the registered trademark of Allentown Equipment, the oldest manufacturer of gunite equipment. Other manufacturers were thus compelled to use other terminology to describe the process such as shotcrete, pneumatic concrete, guncrete, etc. Shotcrete emerged as the most commonly used term other than gunite, and after the later development of the wet process came to be used for both methods.
rods, steel mesh, and/or fibers. Fiber reinforcement (steel or synthetic) is also used for stabilization in applications such as slope
s or tunneling
.
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
(or sometimes mortar
Mortar (masonry)
Mortar is a workable paste used to bind construction blocks together and fill the gaps between them. The blocks may be stone, brick, cinder blocks, etc. Mortar becomes hard when it sets, resulting in a rigid aggregate structure. Modern mortars are typically made from a mixture of sand, a binder...
) conveyed through a hose and pneumatically
Pneumatics
Pneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...
projected at high velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
onto a surface, as a construction technique.
Shotcrete is usually an all-inclusive term; gunite is a term sometimes used for some dry-mix types.
Shotcrete undergoes placement and compaction at the same time due to the force with which it is projected from the nozzle. It can be impacted onto any type or shape of surface, including vertical or overhead areas.
History
Shotcrete, then known as gunite, was invented in the early 1900s by American taxidermist Carl AkeleyCarl Akeley
Carl Ethan Akeley was a taxidermist, sculptor, biologist, conservationist, inventor, and nature photographer, noted for his contributions to American museums, most notably to the Field Museum of Natural History and the American Museum of Natural History...
, used to fill plaster model of animals. He used the method of blowing dry material out of a hose with compressed air
Compressed air
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....
, injecting water at the nozzle as it was released. This was later used to patch weak parts in old buildings. In 1911, he was granted a patent for his inventions, the "cement gun", the equipment used, and "gunite", the material that was produced. Until the 1950s when the wet-mix process was devised, only the dry-mix process was used. In the 1960s, the alternative method for gunning by the dry method was devised with the development of the rotary gun, with an open hopper that could be fed continuously. Shotcrete is also a viable means and method for placing structural concrete.
The nozzleman is the person controlling the nozzle that delivers the concrete to the surface. The nozzle is controlled by hand on small jobs, for example the construction of small swimming pools. On larger work the nozzle
Nozzle
A nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....
can sometimes be held by mechanical arms where the nozzleman controls the operation by a hand-held remote control.
Dry mix vs. wet mix
The dry mix method involves placing the dry ingredients into a hopper and then conveying them pneumatically through a hose to the nozzle. The nozzleman controls the addition of water at the nozzle. The water and the dry mixture is not completely mixed, but is completed as the mixture hits the receiving surface. This requires a skilled nozzleman, especially in the case of thick or heavily reinforced sections. Advantages of the dry mix process are that the water content can be adjusted instantaneously by the nozzleman, allowing more effective placement in overhead and vertical applications without using accelerators. The dry mix process is useful in repair applications when it is necessary to stop frequently, as the dry material is easily discharged from the hose.Wet-mix shotcrete involves pumping of a previously prepared concrete, typically ready-mixed concrete, to the nozzle. Compressed air is introduced at the nozzle to impel the mixture onto the receiving surface. The wet-gun procedure generally produces less rebound, waste (when material falls to the floor), and dust compared to the dry-mix procedure. The greatest advantage of the wet-mix process is that larger volumes can be placed in less time.
Shotcrete vs. gunite
Shotcrete is today an all-inclusive term that describes spraying concrete or mortarMortar (masonry)
Mortar is a workable paste used to bind construction blocks together and fill the gaps between them. The blocks may be stone, brick, cinder blocks, etc. Mortar becomes hard when it sets, resulting in a rigid aggregate structure. Modern mortars are typically made from a mixture of sand, a binder...
with either a dry or wet mix process. However, it may also sometimes be used to distinguish from gunite as a wet-mix. The term shotcrete was first defined by the American Railway Engineers Association (AREA) in the early 1930s. By 1951, shotcrete had become the official generic name of the sprayed concrete process.
Gunite refers only to the dry-mix process, in which the dry cementitious mixture is blown through a hose to the nozzle, where water is injected immediately before application. Gunite was the original term coined by Akeley
Carl Akeley
Carl Ethan Akeley was a taxidermist, sculptor, biologist, conservationist, inventor, and nature photographer, noted for his contributions to American museums, most notably to the Field Museum of Natural History and the American Museum of Natural History...
, trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...
ed in 1909 and patented in North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
. The concrete is blasted by pneumatic pressure from a gun, hence "gun"-ite.
The term "Gunite" became the registered trademark of Allentown Equipment, the oldest manufacturer of gunite equipment. Other manufacturers were thus compelled to use other terminology to describe the process such as shotcrete, pneumatic concrete, guncrete, etc. Shotcrete emerged as the most commonly used term other than gunite, and after the later development of the wet process came to be used for both methods.
Reinforcement
Sprayed concrete is reinforced by conventional steelSteel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
rods, steel mesh, and/or fibers. Fiber reinforcement (steel or synthetic) is also used for stabilization in applications such as slope
Slope
In mathematics, the slope or gradient of a line describes its steepness, incline, or grade. A higher slope value indicates a steeper incline....
s or tunneling
Tunneling
Tunneling may refer to:* Digging tunnels * Quantum tunneling, the quantum-mechanical effect where a particle crosses through a classically-forbidden potential energy barrier...
.
See also
- CementCementIn the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
- ConcreteConcreteConcrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
- Reinforced concreteReinforced concreteReinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...
- Structural engineeringStructural engineeringStructural engineering is a field of engineering dealing with the analysis and design of structures that support or resist loads. Structural engineering is usually considered a specialty within civil engineering, but it can also be studied in its own right....
- The Flintstone HouseThe Flintstone HouseThe Flintstone House is a house in Hillsborough, California overlooking, and best seen from the Eugene A. Doran Memorial Bridge on Interstate 280. It was designed by architect William Nicholson and built in 1976 as an experiment in new building materials, in the form of a series of domes...
— an example of shotcrete housing construction