What Is Shotcrete?

If you've never previously prepared concrete before, you're probably wondering, "What is shotcrete?" Well, any skilled concrete contractor should be able to tell you.

There are various types of concrete applications and kinds of concrete itself.

Shotcrete, for instance, is more of an application than a material. It is used for applying concrete projected at high velocity primarily to a vertical or overhead surface.

Read along to learn more about the shotcrete process.

What Is Shotcrete?

Shotcrete is used for applying concrete pneumatically projected at high velocity on a vertical or overhead surface.

Shotcrete is also easy to apply as sprayed concrete, suitable for curved and thin elements. The impact created by this application consolidates the concrete.

The shotcrete method requires less formwork because it has good chemical bond strength with the materials it is made up of. It can be applied to walls strengthened by steel rods, steel mesh, or fibers.

You will often find shotcrete used in building tunnels, swimming pools, underground walls, drainage systems, and retaining walls.

What Are the Ingredients of Shotcrete?

The ingredients in shotcrete compose of mostly dry material. It is a typically ready-mixed concrete composed of cement, sand (natural or crushed), coarse mixture (below 10mm), admixture, fly ash or micro silica, and water.

What Is the Purpose of Shotcrete?

Shotcrete applied, whether wet or dry, is a great option when you need to reinforce excavations.

The shotcrete method is also often used for an underground parking structure or to stabilize hi-rise buildings upon construction.

Shotcrete can build walls top-down or bottom-up, too. They have high strength, low permeability, and high durability. 

Shotcrete Applications & Uses

Shotcrete is often used in new construction as well as in repairs of walls destroyed by fire, earthquake, or deterioration. It is versatile and convenient, suitable for curved and thin elements.

Whether you work at small construction sites or large hard-to-reach projects, shotcrete can be a big help. Here is a list of important uses of shotcrete:

• Usable on thin overhead vertical or horizontal surfaces, curved or folded sections like canals, reservoirs, and tunnel linings.
• Used for constructing water-retaining surfaces like swimming pools and tanks.
• To stabilize and add temporary protection to freshly excavated rock surfaces.
• To protect coal bunkers, oil tanks, or steel building frames from long-term corrosion.
• Encases structural steel for fireproofing.
• Strengthening walls, beams, columns, and connections.
• To withstand high-temperature applications in the case of refractory lining of kilns, chimneys, and furnaces.

The Types of Shotcrete Technology

Now that your question "What is shotcrete?" is answered, you should still know that shotcrete technology, unlike your conventionally placed concrete, has two types: The dry-mix shotcrete process and the wet-mix shotcrete process.

Dry-Mix Shotcrete Process

In the dry-mix shotcrete process, dry ingredients or gunite are first loaded into a gun and then sprayed through a delivery hose nozzle.

Its nozzle has a water ring where water is mixed into the gunite as it oozes out from the nozzle, propelled to the wall's surface with high-pressure compressed air.

The water and dry shotcrete or gunite are not completely mixed until it exits the delivery hose nozzle and the mixture hits the receiving surface.

For this dry-mix process, it is beneficial to hire a skilled nozzleman.

Wet-Mix Shotcrete Process

In the wet-mix shotcrete process, ready-mix concrete is used and sprayed through a concrete pump. The mix is then propelled through the delivery hose with compressed air at its nozzle for ease of application on the surface.

Compared to the dry-mix process, the wet-mix shotcrete method has less dust and rebound. It is easier to maneuver its hose, and larger volumes can be applied in lesser time.

Shotcrete vs. Concrete: What's the Difference?

There's not much to differentiate between what is shotcrete and just concrete itself. The term gunite refers to the dry mixture, while shotcrete refers to the wet concrete.

Conventional concrete is applied through a mixing truck that prepares and pours the mixture onto the ground. The shotcrete process requires the dry-mix or wet-mix to be applied via a cement gun or hose at high velocity.

With shotcrete, the impact created by the application consolidates the concrete. For conventional concrete, the vibration affects its strength and sturdiness.

Is Shotcrete More Expensive Than Concrete?

Whether shotcrete is applied wet or dry, this free-form, highly versatile, and watertight concrete can cost between $55 to $60 per square foot. In most cases, it can be more expensive than conventionally applying concrete.

What Are the Advantages of Shotcrete?

Here are advantages that make shotcrete compared to conventionally placed concrete more beneficial:

• Excellent bonding with other materials making strong layers for new construction.
• Requires no compaction, does not need expansion joints, and less formwork.
• Application is even and can be applied through a nozzle from a safe distance.
• Easy to use, low permeability, and high durability.
• Used to apply on curved and thin elements making it versatile and ideal for irregular surfaces.
• Shotcrete is used to resist fire, corrosion and mold.
• Cost-effective with reduced labor costs.

What Are the Disadvantages of Shotcrete?

The drawbacks of shotcrete include the following:

• A lot of dust upon application.
• Thick gravel in the mix can hinder spraying, while too-wet ready-mix concrete may not adhere too well either.
• Production costs can be high.
• A lot of concrete material can be wasted.
• A highly skilled professional must be employed and specific equipment required.

When to Use Shotcrete

Shotcrete is used to reinforce both temporary and permanent excavations. It can be considered an earth anchor, among other forms of stabilization.

Shotcrete can take any shape and can be easily colored, too. It is used in various fancy concrete structures, including artificial rock walls, zoo enclosures, canopy roofs, refractory linings, pools, and dams.

Frequently Asked Questions

Conclusion

Shotcrete is a method of applying concrete projected at high velocity primarily onto a vertical or overhead surface.

Compared to conventionally placed concrete, whether it is wet or dry, it can be very beneficial. It's an excellent choice that needs less formwork but still results in stronger structures

But it is still important to consider whether the shotcrete cost is within your budget and whether you have the equipment required.

The overall expenses in the shotcrete wet or dry mix process might be the main consideration to keep in mind.