What is shotcrete?
Shotcrete refers to a method that applies concrete or mortar through pressurized hoses to a nozzle, where it is pneumatically spread over the surface at high speed. It offers all the advantages of standard concrete materials, while its direct application on the surface increases its density. The main features of Shotcrete are:
- High compressive strength
- Low permeability
- Minimum format required
- Shotcrete incorporates dense rebar configurations
- Shotcrete is ideal for creating complex geometric shapes
فهرست مطالب
- Why Shotcrete?
- Types of shotcrete processes
- Comparison of dry mixing and wet mixing processes
- benefits
- Disadvantages
- dry mix
- Advantages of dry mix shotcrete:
- Wet mixture
- Advantages of using wet mix:
- In most applications, the preferred method is determined by:
- Applications
- Repair work
- Slope stabilization or surface protection
- Pools and reservoirs
- Construction of complex structures
Why Shotcrete?
Shotcrete can be used for many economic applications. Adheres to normal or flat surfaces such as plywood, fiberboard, existing smooth concrete, rigid insulation, sheet metal, etc. It also adheres to irregular surfaces such as uneven concrete, soil, shale, rock, even loose gravel.
Types of shotcrete processes
There are two types of shotcrete process which are wet mix process and dry mix process. In the wet mixing process, all ingredients, including water, are mixed together before being sent to the delivery hose and nozzle. In the dry mixing process, dry materials such as cement, sand and aggregates are mixed together and then transported to the desired location. On site, water is added to the mixture at the nozzle before spraying onto the surface. The dry mix process is sometimes called Gunite.
Comparison of dry mixing and wet mixing processes
A comparison is made between dry mixing and wet mixing processes. Each of these processes is suitable for typical construction requirements. The differences are in the capital cost and maintenance of the equipment, operational characteristics, suitability of available materials and location characteristics. However, one or the other may be more attractive for a particular application.
| Dry mixing process | Wet mixing process |
|---|---|
| 1. Instant control over mixing Water and consistency mixed in Nozzles to meet changing farm conditions. |
1. Water mixing by The mixing equipment is controlled and can be accurately measured. |
| 2. It is more suitable for placing mixtures containing light aggregates or refractory materials. | 2. Better assurance that Mixed water is thoroughly mixed with other ingredients. |
| 3. Ability to carry over long distances. | 3. Dust and Less cement material was lost in the firing operation . |
| 4. Delivery hoses are easier to move. | 4. Typically has lower returns and As a result, it has less waste. |
| 5. Less volume per hose size. | 5. Higher volume per hose size. |
benefits
This process has several advantages over conventional concrete for new construction and repair work. Some of the benefits are as follows:
- It makes the structure less porous, which increases the strength of the concrete bond.
- Reducing construction time and reducing construction costs.
- For channel lining protection, bridge safety, and debris flow stabilization.
- It is used to rebuild dilapidated marine structures such as walls, docks, seas, etc.
Disadvantages
- This process is expensive compared to conventional concrete.
- There is a lot of concrete waste.
- Dust is a problem in technique.
dry mix
Pre-mixed dry ingredients are placed in delivery equipment. Compressed air delivers the material through a high-velocity hose to the nozzle, where water is added.
Advantages of dry mix shotcrete:
- Increase bonding ability and bond strength
- The water content is easily controlled in the nozzle, with no time limit for placing the material
- Materials can be transported in bags versus bulk trucks – good for remote locations
- It is more compatible with small volume works and thin coatings
Wet mixture
All ingredients, including water, are thoroughly mixed and fed into the delivery equipment. Wet material is pumped to a nozzle where compressed air is added to provide high speed for placement.
Advantages of using wet mix:
- The water content in the batch plant is more carefully controlled
- Additions can be added based on design requirements
- Suitable for higher volume productivity
Although both wet and dry mix shotcrete have certain advantages, advances in materials and equipment technology have made the two processes nearly interchangeable.
In most applications, the preferred method is determined by:
- Economy
- Availability of materials and equipment
- Access to the site
- Expertise and priority of the contractor
Applications
Shotcrete can be used in place of regular concrete in many cases, the choice being based on convenience and cost. This process also has advantages over conventional concrete in several ways for new construction and repair work. Some of the benefits are mentioned below.
Repair work
Shotcrete is suitable for carrying out restoration works for damages caused to concrete structures due to natural disasters such as fire, earthquake, etc., and it can also be used to repair worn-out concrete from old structures, such as surface and underground bridges, culverts. , walls and many more.
Slope stabilization or surface protection
Sometimes it is chosen to protect a slope that is not stable and may collapse at any time. Therefore, the slope is protected by applying concrete that uses the shotcrete process. This concrete protects the unstable surface of the earth and rock against erosion and runoff during heavy rains.
Pools and reservoirs
Due to the complex geometry of the pool, which is chosen by the client, it is difficult to make a mold or formwork for concrete work. The work also makes the work surface compact and uneven. Therefore, it is easily done by applying shotcrete for complex geometry pool and water tank construction.
Construction of complex structures
This technique is easy to use for complex structures such as domed houses and complex architectural forms.
