A concrete shall pour in particular structural element by mixing of hand or ready-mix concrete. The shotcrete concrete is not one of the types of concrete, it is one of the applying methods on a horizontal or vertical surface.
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What is Shotcrete Concrete
By high-velocity pressure the concrete sprayed on a horizontal or vertical surface of structure through nozzle it’s called Shotcrete concrete or a gunite concrete.
Sometimes instead of concrete, the mortar will be applied on the structural surface.
Shotcrete Concrete Mix Design
The mix ratio for shotcrete concrete the same as what we design conventional concrete but the mixing material and water-cement ratio will be changed to compare the normal concrete because the concrete may use in water logged area or seashore.
The concrete mix design may change as the requirement where it could to use!.
The components of the concrete mix shall be weight-batched before mixing by a proper weight watcher. Batch shall be based on the weight of single components with accuracy within ±1.0% of the values corresponding to the selected type of mix.
Selection of Material for shotcrete concrete
The primary mixing material of concrete is Cement, fine aggregate and coarse aggregate.
Mostly the OPC cement and sulphate resistant cement was used in shotcrete preparation.
The Sand shall be clean and free from injurious amounts of salt, alkali, deleterious substances or organic impurities and shall conform to IS:383 & it shall be tested for organic impurities as per IS 2386.
The fine aggregate used shall be graded from coarse aggregates, according to IS:383. The size of the coarse aggregate should be below 10mm.
If the size of the coarse aggregate exceeds 10mm, the concrete stuck on the nozzle.
Reinforcement for shotcrete concrete
The reinforcement for shotcrete concrete depends upon the purpose of use because sometimes steel fabric wire used as reinforcement. Mostly TMT will be used as reinforcement.
When the shotcrete concrete applying in MS pipe, 13 gauge or 14 gauge steel fabric wire used for reinforcement.
Shotcrete Application Procedure
- After selection of the right material, the material collected and dumped into the material pit of the shotcrete machine.
- The material mixed in dry condition and thereafter required water mixed with the material.
- At right velocity, the concrete sprayed eventually on the specified surface.
- After spraying the concrete the surface levelled uniformly.
Shotcrete Quality & Test
You may ask a question about the quality and strength of the shotcrete!.
As we discussed above there is no major difference between the conventional concrete and shotcrete concrete.
The curing will be executed properly as per mentioned in IS 456:2000 and if we membrane curing period shall not be less than 4 days.
The suggested curing period for a concrete minimum of 7 days. During this curing period, the applied concrete should not be disturbed.
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Shotcrete concrete Uses
- It is very effective in repair and rehabilitation works.
- We can pour concrete either horizontal or vertical surface.
- Mostly shotcrete used to construct a retaining wall where the soil is very loose.
- The shotcrete concrete is mainly used in underground oil or water pipeline where the pipe is buried under the earth to avoid the pipe corrosion.
- To avoid internal damages of the surface.
Advantages and Disadvantages of Shotcrete concrete
We found so many technologies but however, there will be an advantage and disadvantage. So now we discuss that also.
Advantages of Shotcrete concrete
- It can reduce manpower.
- Minimal formwork only required.
- Economically good to compare the conventional concrete.
- We can easily control the water-cement ratio.
- Economically furnish the repair and rehabilitation work.
Disadvantages of Shotcrete concrete
- Material wastage may high compared to the conventional concrete method.
- High skill manpower required to do the job.
- The concrete smooth finishing work is a little complicated.