What is the purpose of shotcrete?

Shotcrete is a method of applying concrete projected at high velocity primarily on to a vertical or overhead surface. The impact created by the application consolidates the concrete.

Is shotcrete stronger than concrete?

What is Shotcrete? Frequently used in underground applications, shotcrete is a wet- or dry-mix concrete that is pneumatically propelled at high velocity through a hose and nozzle. And because the spray application process reduces the water/cement ratio, it’s generally stronger than CIP.

What are some advantages of shotcrete during rehab construction?

ADVANTAGES

• No major disruption to traffic, business, etc.
• Extremely cost effective.
• No excavation or trenching.
• The smooth interior of a Shotcrete lining improves flow by reducing the roughness (Manning’s) coefficient.
• Repair without interfering with existing utilities.
• Environmentally friendly.

What is difference between shotcrete and concrete?

Traditionally, concrete has been poured from a ready mix truck onto a project site. It is either placed on the ground or into forms, and then vibrated to flush out air and to make sure that it is compact. Shotcrete involves applying the concrete after it is already mixed.

Where is shotcrete used?

In building repairs, shotcrete is commonly used for repair of fire and earthquake damage and deterioration, strengthening walls, and encasing structural steel for fireproofing. The repair of structural members such as beams, columns, and connections is common for structures damaged by an earthquake.

What is a disadvantage to shotcrete?

The primary disadvantage of shotcrete compared to poured concrete is the amount of time that it takes when used for large foundations, structural piers, and other structures with large cross-sections, compared to using conventional forms for these large structures.

Is shotcrete better than gunite?

Durability. Gunite generally lasts longer and maintains a higher quality than shotcrete. For instance, gunite tends to dry faster than shotcrete, leading to a much smoother surface and avoiding significant cracks from shrinking. Gunite can also withstand up to 9500 psi, a much higher psi than shotcrete.

How thick can shotcrete be applied?

There is no stated maximum thickness for shotcrete used in shear walls or any other type of wall. Walls have been successfully placed to a thickness of 36 in. (914 mm) for some time. The two main concerns are the heat of hydration and proper encapsulation of the reinforcing steel.

What are the advantages and disadvantages of shotcrete when is shotcreting preferred over other concreting methods?

Shotcrete is more economical than conventional concrete because it requires less formwork. It only requires a small space for construction and its location. In the case of the shotcrete, cement content is high, so it is durable. It is resistant to fire, disasters, mold, worms and also has low permeability.

Why is shotcrete used in tunnels?

An important area of shotcrete application in underground mining is in the support of ‘permanent’ openings such as ramps, haulages, shaft stations and crusher chambers. Rehabilitation of conventional rockbolt and mesh support can be very disruptive and expensive.

Is shotcrete a type of concrete?

Shotcrete, gunite, or sprayed concrete is concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique, first used in 1914. It is typically reinforced by conventional steel rods, steel mesh, or fibers.

What are the advantages of wet shotcrete?

Less rebound The amount of water in the shotcrete mix, among other factors, influences rebound quantity. The wet-mix method provides more control over the shotcrete mix, reducing rebound in comparison to the dry-mix method.

What is shotcrete and how is it applied?

Shotcrete is applied using a wet- or dry-mix process. The wet-mix shotcrete process mixes all ingredients, including water, before introduction into the delivery hose. The dry-mix shotcrete process adds water to the mix at the nozzle. Shotcrete is used in new construction and repairs and is suitable for curved and thin elements (ACI 506R).

How many mm is a shotcrete hose?

Shotcrete nozzle with 75 mm concrete hose from line pump and 20 mm compressed air line. Shotcrete, gunite ( / ˈɡʌnaɪt / ), or sprayed concrete is concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique, first used in 1914 invented by engineer Heidar Rizouki.

What is the difference between wet mix and dry mix shotcrete?

The wet-mix shotcrete process mixes all ingredients, including water, before introduction into the delivery hose. The dry-mix shotcrete process adds water to the mix at the nozzle. Shotcrete is used in new construction and repairs and is suitable for curved and thin elements (ACI 506R).

What is section 53 of the standard specifications for shotcrete?

This section provides guidelines for inspection of shotcrete placement under Section 53, “Shotcrete,” of the Standard Specifications. Shotcrete is concrete that is pneumatically projected onto a surface. Shotcrete is used for facing of soil nail walls.