THE HISTORY OF SHOTCRETE
Shotcrete and Gunite – what’s the difference? Where do these terms come from? Let’s dive into the history of shotcrete and break down some common terms in the Shotcrete Industry!
What is Shotcrete?
Shotcrete is a method applying concrete projected at high velocity primarily onto a vertical or overhead surface. The concrete is applied using a wet-mix or dry-mix process.
The wet-mix shotcrete process mixes all ingredients, including water, before introduction into the delivery hose, and air is added at the nozzle to increase velocity of the material leaving the hose.
We prefer the dry-mix method.
The dry-mix shotcrete method is a technique for applying a mixture of cement and aggregate to a surface using compressed air. Water isn’t introduced to the mix until the very end, when the material reaches the nozzle of the hose.
The velocity in the dry-mix process is attained with the high volume of air used to convey the material down the hose where the smaller orifice of the nozzle increases velocity, as well as helps mix the material with water. In either process (dry or wet), the concrete leaving the hose is traveling between 60 and 80 mph.
GUNITE VS. SHOTCRETE
The first Gunite machine was invented in 1910 by Carl Akeley. He sold the patent and rights to the Cement Gun Company around 1911 and the term “gunite” was introduced to describe the sand-cement product produced by a dry-mix “gun.”
The Cement Gun Company was highly active in the worldwide spread of pneumatically-placed concrete, as the more modern concrete pump had yet to be invented.
Gunite was the first method of placing high velocity concrete. To address the subject without using a trademarked name, the American Concrete Institute (ACI) recognized the process as “shotcrete” in 1951.
Once the advancements had been made to the concrete pump, it was discovered that an otherwise low velocity concrete pump could also “shoot” concrete by adding air just before a nozzle tip with a reduced orifice.
To address this new process, ACI decided to call both processes “shotcrete,” differentiating the processes with the terms “wet-mix” and “dry-mix.”
Nowadays, “shotcrete” is a widely used and recognized term worldwide. So, to preserve a little history, we implement “gunite” in our company’s namesake.
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