What is Shotcrete?
Shotcrete refers to an application method for refractory monoliths. You may have seen concrete being pumped through heavy duty hoses into bridge piers or road surfaces that might be in hard to reach areas. Heavy duty pumps can be used to transport refractory concretes too, providing a speed and accessibility advantage over traditional placement methods. Pumpable refractories are generally placed behind forms much the same as castable refractories are. The shotcrete method is an extension of pumping wherein the pumpable refractories are gelled and stiffened with chemical activators during placement. These activating chemicals are aspirated and injected into the pumped material by use of a specially designed nozzle just before the pumped refractory leaves the hose. In this way the material can be used to build a refractory lining without the use of forms. The pumping and shotcrete methods are generally the fastest way to install refractories with a controlled water addition.
As a structural material, most people are familiar with concrete. However, not everyone is familiar with the form of concrete known as shotcrete. Here is some background on shotcrete, including how it is used in building projects today. Essentially, shotcrete is projected concrete. Originally devised in the early 20th century, shotcrete was created as a means of using concrete to fill out molds. The concrete itself was a dry mix that was blown directly into the mold using compressed air. As the concrete was released, the dry mix was moistened, allowing it to settle and set in the mold. The inventor of this method, Carl Akeley, received a patent in 1911 for both the concrete gun he developed, as well as the material that was produced, which he dubbed gunite. Other applications for shotcrete were immediately obvious. Because the shotcrete could be applied to a horizontal or a vertical facing, the shot concrete could easily be applied to the sides of buildings, the shotcrete could be used
Shotcrete (formerly known as Gunite) can be best described as pneumatically applied or sprayed concrete. Shotcrete mix designs are a combination of Portland cement, aggregates, water and admixtures. The admixtures can range from silica-fume and accelerators to steel or synthetic fibers. These components are either mixed and then pumped to the nozzle (wet process) or pneumatically conveyed by compressed air through special hoses to the nozzle (dry process), where the material is shot or sprayed in place. Finish of the product can range from float or trowel finish to carved, colored textures. Shotcrete, being sprayed concrete, results in a very durable product with structural properties. Mix designs are available to address needs such as high compressive strengths, long-term durability and early-age strength development. Shotcrete is typically used to repair concrete on parking structures, bridges, dams, sewers, tunnels and marine structures. It is also commonly used in building swimming
Shotcrete refers to a process in which compressed air forces mortar or concrete through a hose and nozzle onto a surface at a high velocity and forms structural or non-structural components of buildings. The relatively dry mixture is consolidated by the force of impact and develops a compressive strength similar to normal- and high-strength concrete. Materials used in the shotcrete process are generally the same as those used for conventional concrete-portland cement, lightweight aggregate, water, and admixtures. Shotcrete projects also call for the same types of reinforcement specified for conventional concrete, including deformed bars, welded wire fabric, and prestressing steel.
Simply said, shotcrete is sprayed concrete or mortar. In the wet mix process all the ingredients, including water, are premixed. The mix is then pumped to the nozzle where compressed air blows it into the substrate. “The shotcrete process is particularly suited for curved or sculpted surfaces.” Shotcrete has a wide range of uses – casting new structures; swimming pools; sculpting waterscapes; lining tunnels and ditches; paving slopes and complex shapes such as skateboard parks and earth retaining structures; strengthening and repairing existing structures of all types; providing fireproofing and chemical protection to steel; and construction of tanks, basement walls (underground parking facilities) and any other place that can not be formed and poured. The use of shotcrete to build new concrete structures as well as to restore and repair existing structures is well known and documented. Shotcrete for ground support in tunnel and mine operations is perhaps less known in the general cons
