Process of Sprayed Concrete Mix
In the construction of a sprayed concrete mix, there are primarily two steps involved. They are as follows: Concrete sprayed using the dry process Concrete sprayed with the Wet Process The workability of sprayed concrete guarantees that pumping and spraying operations are as simple as possible. Another constant necessity of sprayed concrete is its durability, which is mostly achieved by emphasising the following property gain:Early on, you build strength.
Flow delivery is dense during pumping.Workability, or user-Friendliness In the context, concrete with the right properties Good pliability, i.e. the capacity to spray The term “sprayed concrete mix” refers to the method of installation. When the manufacture is finished, the mix is transported to the processing equipment via traditional methods.
The Dry Process of Sprayed Concrete Mix
In the event of a dry procedure, a fixed amount of cement and aggregate are mixed in the proper ratios without the use of water. The combination is fed into a specially built machine, which is compressed and forced through a high-velocity airstream, allowing the mix to be transported through the hose to the spraying nozzle. An atomized spray arrangement sprays clean water at the nozzle area to moisten the dry mix being carried. The spray will supply the appropriate amount of water to achieve the desired consistency.
This level of consistency will aid in the spraying of the substance without interruption.The dry process is based on the idea that the aggregate/cement ratio of the mix should be kept at a reasonable level with a low water-cement ratio.
The slump trait is not used as a criterion. As a result, the dry technique is appropriate for restricted thickness and overhead construction.
Admixtures are added in dry form to the dry cement and aggregate content if necessary; in liquid form, they can be added to the sprayed water or a separate admixture injection can be supplied in the equipment. Steel fibres or other types of fibres can be incorporated into the pre-mix.
A wide range of machines are offered depending on the throughputs. They provide a precisely regulated rate of application, i.e. low application rates that can be used on thin layers or intrinsic structures. Tunnel slope building is also aided by high rates.
Sprayed Concrete Dry Mix Process Equipment Technique
The application of the nozzle is regulated by the hand. The nozzle man will direct the flow of materials and ensure that the water is added in precise amounts. The amount of water that can be changed can only be done within a certain range.
As a result, it’s important to remember that less water won’t offer enough compaction, while more water would cause the mix to sag excessively. Automated spraying equipment based on robotic systems are available in regions where it is dangerous for the nozzle man to apply the sprayed concrete.
This strategy is extremely adaptable and can be used in a variety of situations. Any type of cement, as well as traditional and light-weight aggregates, can be used. The mix’s aggregate to cement ratio is within the permitted range.
The cement content of the put mix will be larger than the batched pre-mix since the rebound is aggregate. The following are some of the aspects of dry performance on its performance:Density range is good. Increased strength from 40 to 50 N/mm2 Bonding to the substrate is stronger.The intrinsic qualities obtained by the dry process are more variable than those obtained by the standard approach or the wet procedure.
Sprayed Concrete Dry Mix Process Equipment
Twin chamber machines, such as the Boulder Gun and its variants, are the traditional means of having sprayed concrete mix. When using refractory materials or dry sand and cement mixes, this machine performed admirably. When a mix with a water percentage greater than 3% was required, this machine was found to have a disadvantage. In the classic machines discussed previously, more water content leads in material clogging. Other Boulder gun variants have been developed that use the sealed chamber principle, which allows for a continual supply of material into the chamber through a rotary valve.
Dry Process Equipment and Application for Sprayed Concrete Mix
The Rotor Type dry mix machines are currently available. The majority of the dry mix is fed into an open hopper on this machine. The material falls into a spinning barrel, which is then blown into the spraying hose by compressed air. They travel via the water injection nozzle and are treated with water. The amount of water is determined by the nozzle man’s judgement. The distance between the machine and the nozzle can be quite large, up to 600 metres. The machines that have been created for the dry process can handle moisture content up to 10%, resulting in an output volume of 10m3/hr. Liners are used to prevent blockages caused by high moisture content.
Special machinery have been created to allow only pre-bagged engineering materials to be used in the application. Lubricated sealing plates and bigger motors are used to achieve higher tension than other machines discussed previously. This configuration helps to prevent dust from escaping from the sealing plates to a greater extent.
Dry spray machines are the only ones that allow the mix (sand, cement, and aggregate) to be fed into the air stream at a consistent rate. If the feed rate is not continuous, the nozzle man finds it difficult to maintain the water cement ratio. Fire damage structural restorations, tunnelling, mining, swimming pools, zoo enclosure construction, bridge strengthening, and other applications are all possible using dry sprayed concrete mix.
Wet Process of Sprayed Concrete Mix
The wet technique uses a mixture of cement, aggregates, and a measured amount of water for the entire mix. Before beginning the pumping procedure, the entire mixture is prepared.High-velocity air is used to move the entire mix into place. The concrete will be sprayed to the area where it needs to be placed thanks to the high-pressure air that is supplied into the nozzle and the resulting velocity. Because of the speed gained during spraying, the sprayed mix will get compacted. Wet mixed sprayed concrete can be delivered either ready-mixed or through site batching. These can also be delivered in bags in a dry state (pre-blended components). These bags are ideal for little amounts.
With the use of the wet process, the water/cement ratio may be easily adjusted. Using decreasing plasticizers, a water/cement ratio of 0.45 can be easily achieved. Because of the larger cement concentration, the wet method has better strength qualities.The cement content utilised in most cases ranges from 350 to 450 kilogrammes per cubic metre. After 28 days, the cube strength is 30N/mm2 and 60N/mm2 respectively. With the help of hydration control admixtures, the mix’s working hours can be extended up to 72 hours. This allows for more freedom. This strategy avoids the need to wipe the entire system after each application. To improve strength and durability, the mix should be of high quality. A suitable balance of fine and coarse.
Wet Process Technique of Sprayed Concrete Mix
Spraying techniques vary depending on the nature of the job. In general, the concrete layer is built up to a thickness of 150mm. More thickness can be added to the final layer after it has fully dried.Care should be used while spraying a new concrete layer over an existing one. Any harmful compounds must be removed from the existing layer. If any are present, they must be cleaned by jet washing with water from the top to the bottom of the building.
The wet sprayed concrete mixture can be used as a structural element or as a decorative finish. This determines which system is used. The wet technique makes it difficult to create fine features. However, special requirements are required wherever they are.
This is a technique in which cement and aggregates are batched, mixed and delivered into a purpose-made machine.
Gunite and shotcrete are two trade terms for different types of sprayed concrete.
concrete or mortar conveyed through a hose and pneumatically projected at high velocity.
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