Spray concrete, commonly known within the industry as “shotcreting”, involves the projection of wet or dry mix concrete at a high velocity and letting the material set on the receiving surface. Using this method, the material can be sprayed onto any type or shape of surface, including vertical or overhead areas.
Sprayed concrete has a high, early and rapid strength gain, and is low in permeability, meaning it can provide a solid, waterproof lining, without the need for formwork in an extremely short space of time. For certain applications, such as lining tunnels and subterranean works, this technique is extremely useful.
History of spray concrete
Although this method is now used every day on large and small projects across Britain, spraying concrete is, relatively speaking, a new building technique. The process has an interesting backstory, having first been discovered by a museum curator in Chicago in the late 1890s.
Dr Carlton Akeley, from the Chicago Field Museum, was working on the creation of replica prehistoric animals, attempting to apply mortar over skeletons to make them more lifelike. Having initially tried and failed to spread the material over the frame using a trowel, he went on to create a crude single chamber pressure vessel which would project a mix of sand and cement over the frames.
Following his initial success, Akeley made several refinements to, what he called, his ‘cement gun’ patenting the technique, and introduced it into global markets. During the Second World War, spraying concrete was an instrumental technique in building airport hangers for Spitfires and repairing bombed-out structures in Britain.
In the 1960s, spray concreting technology advanced to include wet mixes. This involved pumping out ready-mixed concrete rather than adding water at the nozzle. The practicality of the technique was quickly recognised by the industry and its use became commonplace for a wide range of applications in the commercial building sector.
Posted: Feb 25, 2015
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