How do you spray shotcrete?
9 Rules for the art of shotcreting
- Clean the surface before spraying.
- Maintain a distance of 1 to 2 m between the nozzle and the substrate.
- Place the nozzle at an angle of 90° to the substrate.
- Fill holes and cracks.
- Application in layers.
- Clean the surface after longer breaks between the application of layers.
What are the two types of process in shotcrete?
The two basic methods for applying shotcrete are the dry-mix process and the wet-mix process. The term gunite is frequently used when referring to the dry-mix method; other terms such as air-placed concrete, gunned concrete and sprayed concrete have also been used in the past to describe the process.
How do you stop rebound in shotcrete?
It’s vital to keep a distance of 1-2 m between the nozzle and the surface: too short a distance will create a greater amount of rebound, while an excessive one will prevent the shotcrete from compacting.
Can I do shotcrete myself?
DIY shotcrete is achievable for a hobbyist, owner/builder or a contractor. It is all about the speed of delivery you want to accomplish. The best advice ever shared with me about shotcrete and pumping concrete is to choose the equipment needed as a package, because each set up works best at a specific scale.
How long does it take to shoot shotcrete?
As a general rule, without the use of retardant admixtures, you have 90 minutes in the wet-mix process from the time the material is mixed to when it’s applied.
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 is the code for shotcrete?
IS 9012
The current Indian shotcrete code, IS 9012 is not adequate to fulfil the requirement of the present scenario of sprayed concrete construction. The details about the mix design, usage of fibers, long term durability and standard testing procedures for shotcrete are deficient.
What material is used in shotcrete?
shotcrete, also called (trademark) Gunite, concrete applied by spraying. Shotcrete is a mixture of aggregate and portland cement, conveyed by compressed air to the nozzle of a spray gun, where water is added. The wet mixture is then sprayed in place and may be carved or troweled almost immediately.
Does shotcrete have rebound?
This appears to be caused by the fact that the highest amount of rebound occurs at the time shotcreting begins, when the shotcrete is impinging on a hard surface. Later, when it is being blown against a shotcrete surface the amount of rebound decreases.
What is rebound construction?
Rebound is the material that ricochets off the application surface during the gunite operation. Rebound is typically made up of the larger and harder particles (which tend to ricochet) and does not contain adequate cement, water or density to develop significant strength.
Is shotcrete stronger than concrete?
The impact velocity of properly applied shotcrete instantly compacts the material, yielding an “in-place” mix that is richer in cement and higher in strength than the same mixture prior to placement.
How long does shotcrete take to cure?
7 days
Concrete, when applied using the shotcrete process, or cast-in-place, needs to cure for 7 days. Water is the best curing method (7 continuous days).
What happens if you dont water shotcrete?
Lack of curing and exposure to windy, hot, or dry conditions will certainly increase the potential for shrinkage and cracking of the concrete. Lack of curing will prevent the concrete from achieving its maximum potential strength.
How long do you water shotcrete?
Concrete, when applied using the shotcrete process, or cast-in-place, needs to cure for 7 days. Water is the best curing method (7 continuous days).
Can you shotcrete in the rain?
Shotcrete needs to be protected from rain until it obtains its final set, usually 4 or 5 hours. Following final set, it should be wet cured for at least 4 days, preferably 7 days if possible. The exposure to rain would prove beneficial as the rain would assure the presence of moisture for continued curing.
What is the lifespan of shotcrete?
The durability of shotcrete is equivalent to high-quality concrete. The life span of a new construction shotcrete structure is more than 50 years. For rehabilitation projects, shotcrete can extend the life of a structure by more than 25 years.
What is the mix for shotcrete?
Shotcrete typically consists of one part cement and four parts sand by weight with approximately 7% water by mass of dry ingredients. It can also include coarse aggregate and admixtures. Dry mix shotcrete involves the premixing of dry ingredients with water added at the nozzle.
Are there cold joints in shotcrete?
In shotcrete, there’s no such thing as a cold joint. You can stop shooting and come back a year later and if the surface and surround are properly prepared you can resume shooting and still come away with a monolithic structure.
Does shotcrete cure faster 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.
What is rebound Gunite?
What is the air pressure for dry mix shotcrete?
The air pressure in the hose for the dry-mix shotcrete process is no more than what is registering on the air gauge (80 to 100 psi [0.55 to 0.69 MPa]). The forces experienced by the nozzleman for the dry-mix process come from the ft3/minute of air, not the psi pressure in the hose.
What is shotcrete made of?
Shotcrete is a mixture of cement, aggregates, and water that is usually reinforced by conventional steel rods, steel mesh, or fiber. Shotcreting is performed with the special unit, which consists of a mortar gun or concrete sprayer and a compressor. Here we learn about shotcrete, methods of shotcrete, advantages & diadvantages of shotcrete.
What are the advantages and disadvantages of shotcrete?
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. It also has a good thermal resistance mass.
Why is correct nozzling technique so important?
The body stress and increased fatigue endured while nozzling this way can substantially shorten a nozzleman’s career. Figures 4 to 9 also show correct nozzling techniques. In conclusion, the aforementioned correct nozzling technique has been passed down to nozzlemen for more than 95 years.