Shotcrete and Gunite: 6 Common Questions — Answered
Throughout the country, home and business owners are searching for alternative forms of concrete for tunnels, bridges, swimming pools, and train stations. Cemen Tech understands the difference and similarities between plain old concrete and shotcrete and gunite. Here are answers to the six most common questions.
1. What’s The Difference Between Shotcrete and Gunite?
At the crux, nothing. Gunite was originally a tradename for a pneumatically placed dry sand-cement mixture. When the term shotcrete was approved by the American Concrete Institute (ACI) in the early 1950s, it referred to pneumatically placed mortar. Today, it’s not uncommon for companies and people to call dry-mix shotcrete ‘gunite’ when it’s a method of shotcrete application.
2. Dry-Mix Or Wet-Mix — Which Method Is Better?
This perpetual debate usually boils down to the specific type of application or project.
In most situations using this method, coarse sand and cement mixture mix with water inside the delivery hose. The mixture then sprays from the hose nozzle at high velocity to the targeted surface.
The benefits of using this method include:
- Minimal mess from production and ease of job site clean-up;
- Ideal for pools located in a small work area or those with less than 1,000 square feet of water surface area; and
- Pools with elaborate or sophisticated detail.
With the wet-mix method, premixed concrete moves through the line, with air added once the concrete reaches the nozzle. The air creates a high-velocity flow of the mixture, which is most often cement, coarse sand, and a coarse aggregate less than 3/8 inch in diameter.
Benefits of using the wet-mix method include:
- Less rebound during application;
- The ability to use accelerators, air entrainment, fibers, and other admixtures; and
- Ease of placement for more complex jobs, such as those with several curtains of reinforcing bars.
3. Why Isn’t Gunite Used For Swimming Pools?
It is — remember that the term generally refers to dry-mix shotcrete.
4. What’s The Difference Between Waterproof & Watertight?
Waterproof means a surface is wholly impervious when water is in either its liquid or vapor state. While this sounds ideal, no surface — such as a pool wall — is truly waterproof and will be susceptible to water infiltration as the surface wears over time.
On the other hand, watertight means the pool surface is generally impermeable unless the hydrostatic pressure is high enough to cause structural failure.
5. What Are The Advantages Of Using Shotcrete For Swimming Pools?
Though home and business owners have several installation options for swimming pools, using shotcrete comes with a number of advantages, such as:
- Creating both curving walls and straight surfaces in the same pool;
- Place any textured finish, such as smooth troweling or mimicking exposed rock;
- Meeting close tolerances for infinity edges; and
- Overall quicker installation and construction without a loss of project sustainability.
6. Can A Volumetric Concrete Mixer Produce Shotcrete?
Absolutely! In fact, a mobile concrete mixer can produce both shotcrete methods and at consistently high-quality levels. Learn more about Cemen Tech’s concrete production solutions for gunite and shotcrete here, including our G Series volumetric mixer.