What is the Shotcrete Concrete?
Shotcrete concrete is a mixture of aggregate and Portland cement that is transferred by compressed air to the spray gun nozzle and then water is added. After that, the mixture is sprayed in place and troweling can be done almost immediately. For structural use, shotcrete is usually applied to a grid of reinforcing bars and steel mesh.
Concrete Shotcrete is used for a variety of concrete structures including walls, zoo enclosures, canopy roofs, fireproof linings, swimming pools. and dams are used. Sometimes used in tunneling to connect tunnel walls to prevent leakage and fragmentation.
Shotcrete is a high-performance concrete that is sprayed on the surface through a hose and pneumatically at a high speed. The spraying action leads to concrete compaction and then forms layers of concrete with the required thickness. Shotcrete has been proven to be the best method for building curved surfaces.
With the advent of shotcrete technology, building tunnel lines and domes is now much easier than before. Shotcrete is an accepted and used method of placing materials of a cementitious nature that is used for a wide variety of applications. Since ****, we have seen many advances in this field, both in equipment and in Specialized techniques required for pneumatic application of mortar or concrete! Today, this type of concrete has become a vital material due to its diversity in shape, high strength, durability and good bonding ability, and it can be easily sprayed on the surface at a high speed in hard-to-reach areas.
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⏬ Concrete concrete ingredients ⏬
Cement, water and aggregate are the raw materials used in shotcrete along with various softeners and additives to increase its performance. The high ratio of water to cement and the amount of moisture in sand and gravel are effective in the quality of the final product. The optimal ratio of water to cement is about 0.45. The composition of sand and aggregate depends on water demand, efficiency, accelerators, shrinkage and durability. Now we introduce the ingredients of shotcrete separately:
*️⃣ Portland cement
Cement requirements for shotcrete concrete are similar to the requirements of ordinary concrete. Low alkali cement should be specified when the aggregates used are chemically reactive with the alkalis in the cement. Air entraining cement is used in the concrete production process and has obtained different results. In general, the air content is much lower than normal concrete, and the use of air-entraining cement is not recommended because the air content is affected by external factors such as air pressure, hose length, and type of equipment. When added to the Portland cement matrix, the pozzolan reacts with calcium hydroxide and water to produce more calcium silicate gel. - Water required for concrete: Drinking water should be used. If potable water is not available, the proposed water source should be tested.
- Water for the curing process: There are no special requirements for the water used in the curing of shotcrete. Water for processing shotcrete must be free of elements that cause stains. *️⃣ Aggregates
In shotcrete, light aggregates for the concrete process. It is done. Since the contact of moisture and aggregate begins in the nozzle, a sharp decrease in efficiency in the production of lightweight concrete does not occur. , must have the same specifications as normal concrete. It will not be suitable to use bars larger than 16 mm in diameter. Large rebars make it difficult to get enough shotcrete behind them. In general, the distance of rebars from 150 mm to 300 mm is recommended to strengthen shotcrete. Additives in shotcrete are not the same as regular concrete. Before use in large projects, concrete mixes should be tested on site to ensure that the desired properties are achieved. Chemical additives used in shotcrete must comply with the requirements of the project.
🔽 Types of concrete shotcrete 🔽
Shotcrete is divided into the following two categories:
◀️ Dry mix
The dry mix method includes placing dry materials in a funnel and then transferring them as Pneumatic through the hose to the nozzle. The operator controls the addition of water in the nozzle. The water and dry mix are combined as the mix hits the receiving surface.
The advantage of the dry mix process is that the amount of water can be adjusted instantaneously by the nozzle, making it effective in vertical applications without the use of an accelerator. to occur The dry mix process is useful in repair applications.
◀️ Wet mix
Wet mix shotcrete involves pumping ready-mixed concrete into a nozzle. Compressed air enters the nozzle to move the mixture to the surface of the receiver. The wet method generally has less waste and no dust compared to the dry mix process.
The biggest advantage of the wet mix process is that all the materials are mixed with the required water and additives, as well as the volume More of it can be concreted in place in less time than dry mix.
