Sprayed Concrete
Many project managers and other customers are not familiar with the incredible properties and applications associated with using sprayed concrete. For this reason, we have listed below some general information regarding the various properties and applications for sprayed conc
Types of Sprayed Concrete
Standard types for sprayed concrete include shotcrete and gunite.
Gunite was the original term used by the inventor of the original method for spraying concrete. Originally applied by taxidermist Carl Akeley, it was used to fill plaster molds of animals. Blowing dry concrete material through a hose using compressed air, a water injector nozzle would blast the mixture as it was blown. This original method became known as “Gunite” and was a trademarked term until 1967. It is now a generic term used for this original “dry” method of spraying concrete, where water is added on the fly, as the dry mixture is shot out. Spraying dry concrete has some advantages to wet, in that the water flow can be controlled on the fly which is advantageous for vertical or overhead surfaces, especially with patchwork applications.
Shotcrete is the term generally used for the “wet” alternative to this method. In this method, the sprayed concrete is a pre-mixed slurry that makes application easier, but with slightly less strength than a dry gunite method for sprayed concrete (both are still stronger than poured concrete).
Properties of Sprayed Concrete
Compressive Strength
Sprayed concrete has a higher density than poured. A “wet” mixture has a compressive strength of ~4000 psi, while typical poured psi is between 2500 and 3000.
Shrinkage
Because of the lower water content of sprayed concrete, there is less shrinkage as the excess water dries and evaporates.
Permeability
As with shrinkage, less water = denser material which means less seepage.
Top Benefits of Sprayed Concrete
- Quick – reduced set time & quicker repairs means less downtime & less dollars
- Economical – 50-100% framework savings over poured or cast construction, not to mention crane and other equipment savings or elimination. Repair applications are much quicker, reducing labor costs by roughly half
- Mobile – suitable for tight or restricted areas, overhead or underground applications
- Adaptable – able to cost-effectively repair surfaces not suitable for other processes
- Durable - structures are more durable due to better bonding to the substrate
- Sturdy – huge design, fabrication, erection, removal and transport savings since structuring for sprayed concrete does not have the same requirements for internal load while drying occurs
- Creative – allows complex or creative shapes with little-to-no framework