When shotcreting, concrete (shotcrete concrete) is applied to the surface using special installations. The concrete mixture is fed through a nozzle under high pressure. Concrete is sprayed onto the surface. Technology - shot concrete.
Shotcrete is carried out using a shotcrete installation, consisting of a cement gun (or concrete injection machine) and a compressor.
Shotcrete equipment:
Shotcrete installation SSB 14 FILAMOS.
Country of origin: Czech Republic.
The shotcrete installation is designed for spraying concrete using the dry and wet method for concreting underground and water structures and on engineering buildings.
It is also used for repair and renovation work during conventional and railway construction. In the energy and metallurgy industries, the installation is used for spraying heat-resistant materials in the manufacture of linings for steel-smelting furnaces, boilers, coke oven batteries, etc. in both cold and warm conditions.
The installation can be used at temperatures from +5C to +40C. Shotcrete installations are not as complicated as they might seem at first glance, but at the same time they cope with the task perfectly.
Technical specifications:
| AIR CONSUMPTION - SUPPLY DISTANCE 40 M | 2-5 m3/min. |
| AIR PRESSURE | 0.5-0.6 MPa |
| ELECTRIC MOTOR PERFORMANCE | UP TO 2 KW |
| CONNECTION TO ELECTRICAL NETWORK | 380 |
| GRAIN GRIND OF THE TRANSPORTED MATERIAL A MAX. | 8 MM FOR DIA. 32 MM 16 MM FOR DIA. 40 MM |
| SUPPLY DISTANCE - HORIZONTAL. MAX. | 300 M (FOR 32 MM 150 M) |
| FEED DISTANCE - VERTICAL MAX. | 100 M |
| LENGTH | 1130 MM |
| WIDTH | 805 MM |
| HEIGHT | 980 MM |
| WEIGHT | 300 KG |
During the construction or repair of various concrete structures, it is often necessary to carry out work to strengthen their surfaces, increase frost resistance and waterproofing properties. An excellent solution to such problems is to apply an additional layer of concrete to the surface of the structures. A special technology for applying concrete mortar, called shotcrete, helps to achieve a strong connection of the material with the existing surface.
The process is a layer-by-layer application of a solution to the surface to be treated, carried out under high pressure of compressed air, due to which the material is firmly connected to the surface. To perform shotcrete, special installations are used, consisting of a cement gun and a compressor.
The concrete solution used consists of cement, aggregate, and special additives (setting accelerators, plasticizers). Depending on the size of the aggregate, two types of material are distinguished.
First - shotcrete concrete, obtained using filler with a particle size of up to 10 mm. This material is used to create a coating layer 3-4 cm thick.
The second material is called shotcrete, for its production a filler is used - crushed stone with a particle size of up to 25 mm. Using this material you can create coatings up to 15 cm thick.
The main difference in the use of these materials is the following: shotcrete concrete is usually used for repair, strengthening or finishing of various structures. In addition to all this, shotcrete can also be used to create load-bearing structures.
Shotcrete - advantages and applications
Compared to other methods of protecting and repairing surfaces, pressure concreting has a number of advantages:
- the mechanical strength, water resistance and frost resistance of structures increases;
- thanks to mechanization, worker productivity increases and the cost of work decreases;
- Shotcrete allows you to process large surfaces of structures in one cycle and apply a sufficiently thick layer of material;
- high quality, durability and reliability of the applied coating.
The shotcrete method is used for:
- construction of vertical thin-walled structures;
- protection of slopes and slopes;
- repair of hydraulic structures, tunnels, bridges;
- repair of facades of buildings and structures;
- sealing joints, seams, eliminating surface defects;
- strengthening structures;
- increasing water resistance, frost resistance, and fire-resistant properties of structures;
- surface finishing.
Surface shotcrete methods
There are two main methods of concreting under air pressure: dry shotcrete and wet.
In the first method of concreting, a dry concrete mixture from a special bunker is fed into the nozzle of a cement gun using compressed air in a rarefied stream. At the base of the nozzle, concrete is mixed with water and applied to the surface under high pressure.
With the wet concreting method, the finished concrete mixture is supplied using a mortar pump through a hose into the nozzle; compressed air is also supplied there, which forcefully pushes the mixture out of the nozzle, applying it to the surface to be treated.
The main advantages of dry shotcrete: high productivity; the ability to apply a thick layer of concrete in one pass; no equipment clogging and increased service life. Advantages of wet concreting: homogeneous composition of concrete, the possibility of final, “finishing” surface finishing, absence of dust, minimal loss of material.
The constant development of construction technologies contributes to the improvement and expansion of the scope of application of the method of concreting structures under pressure.
Surface shotcrete is a reliable and economical way to protect building structures.
Application experience:
Gunning of concrete walls of METROPOLITAN ventilation shafts in the MOSCOW Hotel, Okhotny Ryad, 2. Customer STRABAG AG.
CEMENT GUNS- an installation for spraying onto the surface of building structures and structures mortar and concrete mixture - shotcrete, which has water resistance and increased strength, elasticity, fire resistance, frost resistance, acid resistance, etc. Gun cement is used in the construction and repair of hydraulic, industrial and civil structures, and also as a sandblasting machine.
The technological process of shotcrete involves introducing a dry concrete mixture through a cement gun feeder into a rubber hose, through which it is supplied with a stream of compressed air to the work site. At the outlet of the hose, the mixture is moistened in a special nozzle with water, which is supplied under pressure from a centrifugal pump or water tank through another hose. The moistened mixture flies out of the nozzle at a speed of 50-70 m/sec, covers the surface, building up a layer of shotcrete on it. The main indicator of a cement gun is the dry mix output in m3/hour.
The C-630A model cement gun has two chambers instead of a sluice drum: a sluice chamber (upper) and a working chamber (lower). The chambers are equipped with bell valves, with which you can load the upper chamber and transfer the mixture to the lower one without interrupting the technological process. The mixture is fed into the material hose by a disc feeder located in the lower chamber and rotated by an air motor. The design of the S-630A cement gun allows the use of aggregate with a particle size of up to 52 mm at a humidity of up to 6-8%.
To waterproof rooms such as swimming pools, reservoirs, and damp basements, dense waterproof plaster - gunite - plaster is used.
Shotcrete - plaster is applied using a cement gun. The method of applying plaster with a cement gun is called shotcrete. Shotcrete occurs under high pressure of compressed air, due to which the solution jet is imparted a high speed. Layer of shotcrete - plaster 15-25 thick mm, applied to the surface, is a fairly reliable waterproofing, since the applied solution is highly compacted. After 28 days of hardening under natural conditions, shotcrete plaster reaches a tensile strength of 15 kg/cm 3 .
Units for applying shotcrete - plasters. Shotcrete plaster is applied using a unit that includes a cement gun, an air purifier, a water tank and a compressor. The main machine is a cement gun.
Cement guns come in various brands: SSSM-067, S-165A, S-165B, S-320A and 0-54. Regardless of the design of the cement gun, the operating principle is the same.
Cement gun SSSM-067 (Fig. 128, a) consists of an upper 11
and lower 15
truncated cones-reservoirs, or chambers, fastened into one whole.
The upper tank has a loading funnel through which it is filled with dry mixture. A steel pipeline runs from the outside of the housing; Flexible hoses are connected to it from the compressor. Compressed air is supplied to the cement gun through these hoses.
Cement gun S-165B (Fig. 128, b) has the same device as SSSM-067. It can also be used as a sandblaster to clean the surfaces of various structures from dirt, soot, and rust.
An air purifier is necessary to clean the compressed air pumped by the compressor into the cement gun.
The air cleaner is a welded cylinder. At the top of the bottom there is an inlet pipe to which a hose is connected to supply compressed air from the compressor. The cover has an outlet pipe: an air hose is connected to it, supplying compressed air purified from water and oil to the cement gun. Inside the air purifier there is a porous porcelain filter that cleans the air supplied by the compressor from dust, moisture and oil.
Before applying shotcrete plaster, water is supplied to the nozzle under pressure of 0.5 atm higher than the air pressure in the cement gun. This can be achieved by connecting a water hose to the water supply. If there is no water supply or there is very little pressure in it, then a special tank is used to supply water, to which a compressor is connected, with which you can increase the pressure.
Rubber hoses are used to connect the cement gun, air cleaner, water tank and compressor, as well as to supply water to the workplace from the cement gun to the dry mixture nozzle and from the water tank.
The hoses through which the dry cement-sand mixture is supplied are called material, through which air is supplied - air, and through which water - water. For strength, the hoses are reinforced with 3-5 layers of cord (special durable fabric). The hoses are covered with soft, wear-resistant rubber on the inside, and harder rubber on the outside, which protects them from being pressed through.
Material hoses are produced with a diameter of 25-38 mm. It is more advisable to use hoses with a diameter of 32 mm. The use of hoses of smaller diameter reduces the productivity of the cement gun and leads to the rapid formation of plugs. Water hoses are used with a diameter of 13 mm. The individual hose sections are connected with screw-on couplings. Couplings with hoses are fastened with rivets or countersunk bolts. To prevent hoses from leaking air, the connections must be strong and tight.
. A nozzle is used to mix the dry mixture with water and apply the solution to the surface (Fig. 129). The nozzle consists of a body 1
and a ring-shaped chamber with inserted mixers 2
. The mixer is a ring with eight inclined radial holes. A metal conical barrel is attached to the mixer body on the front side 3
with inner liner 4
made of rubber, protecting the barrel from rapid abrasion. A material hose is secured to the rear side of the housing using a half-nut. 5
, through which the dry mixture is supplied to the nozzle. A pipe is attached to the top of the body 6
with valve 7
, a water hose is connected to the valve 8
. Water supplied from the pipe enters the mixing chamber in streams and, meeting the cement-sand mixture, mixes - a solution is formed. The solution is forcefully ejected by compressed air from the nozzle onto the surface, penetrates into all its irregularities and is firmly connected to it.
More advanced are the cement guns S-320A and O-54. They have water pumps that can supply water at the right pressure to the nozzle from any source. They can operate without an air purifier, making the unit more compact. In addition, they are mobile continuous machines.
Cement gun S-320A (Fig. 130) is intended for applying a waterproofing layer to various surfaces, for cleaning them with an air-sand jet. It consists of a bunker 4
, housing, four wheels, sluice drum 8
, dispenser 10
with drive mechanism and water pump. Bunker 4
has a mesh, which is necessary for control sifting of the dry mixture.
An electric motor is installed on the cement gun; it drives the dispenser and the gear water pump, which supplies the nozzle with water.
Technical characteristics of the cement gun S-320A
Productivity in terms of dry material consumption, m 3 /h .... 1,5
The average thickness of the layer applied at one time is mm ...... 20
Acceptable grain size, mm............... 8
Dry mixture supply range, m:
horizontal........................... 70
vertical............................. 30
Highest air pressure kg/cm 2 ............ 3-3,5
Water pump (performance), l/sec, at pressure up to 40 m.... 0,23
Weight, kg:
without hose........................ 800
with hose........................ 950
The 0-54 cement gun is a smaller version of the S-320 cement gun. The productivity of the cement gun 0-54 is lower. Its main purpose is to clean facades using air-sand and water-emulsion mixtures, as well as to apply compacted plaster in one layer.
Technical characteristics of cement gun 0-54
Surface area to be cleaned, m 3 /h:
using an air-sand mixture...........up to 50
using water-emulsion mixtures..........up to 15
Consumption of dry materials, m 3 /h...............up to 1
Air consumption, m3/min:
with air-sand mixture...................up to 2.5
for water-emulsion mixtures..............up to 1
Air pressure, kg/cm 3 ...................up to 5
Feeding range m:
air-sand mixture.............up to 30
water-emulsion mixtures................up to 40
Electric motor power, kW..........................2,8
Dimensions, mm:
length........................1100
width........................580
height........................1100
Weight, kg..............................250
Preparation of dry mixture for shotcrete plaster. The dry mixture is prepared in stationary installations and delivered by truck to the place of work. It is prepared both on a construction site in mixers and, as an exception, on a striker by hand using the prancing method.
To protect the dry mixture from moisture, it is necessary to have a chest with a tight-fitting lid at the work site.
Before use, it is recommended to additionally sift the mixture brought from a stationary mortar unit or prepared at a construction site through a sieve with cells with a cross section of 8X8 mm so that it mixes better and becomes more homogeneous. This mixture is well transported through hoses.
To prepare shotcrete plaster, grade 300 or 400 cement and river sand are used. The ratio between cement and sand ranges from 1:1 to 1:8.
The sand used must be sufficiently dry and clean; Sand contamination reduces the strength of shotcrete plaster. Permissible sand moisture content is 6-10%. If its humidity is less than 4%, sand should not be used, since the prepared mixture will separate when transported through material hoses. Overdried sand does not mix well with water in the nozzle, resulting in a cement mortar that is uneven in composition. The use of excessively fine sand reduces the strength of shotcrete plaster by two or more times.
To speed up the setting of shotcrete plaster, add calcium chloride or liquid glass. Calcium chloride is introduced no more than 5% by weight of cement. Calcium chloride is used only in low temperature conditions (below + 5° C). Liquid glass is administered in the amount specified by the laboratory.
To obtain greater water resistance, ceresite can be added to shotcrete plaster in a ratio of 1: 10 (1 part ceresite and 10 parts water) or sodium aluminate from 1: 6 to 1: 15, where 6 to 15 parts of water are taken per 1 part. These chemical additives are dissolved in water and poured into the dosing tank.
Shotcrete with a cement gun. Before starting work with a cement gun, first of all, install a gunite unit (Fig. 131): near the cement gun 1
air purifier 4
, storage tank 3
for water and a little further on the compressor. A hose with two branches is connected from the compressor. One end is connected to the air purifier, the other to a water tank. The hose from the air purifier is connected to a cement gun. Thus, compressed air will be supplied to the cement gun from the compressor. A material hose is connected to the nozzle from the cement gun, and a water hose is connected from the tank.
After installing the unit, you need to check how it works and make sure that there is no air leaking anywhere.
The cement-sand mixture is loaded into the upper chamber of the cement gun, and under the influence of its own weight the mixture is poured into the lower chamber. The shutter closes and compressed air is admitted into the chamber. The mixture is supplied to the nozzle using a distribution plate. Compressed air passing through the nozzle picks up the mixture and blows it through the nozzle and material hose to the nozzle.
As soon as the loosened, suspended mixture, picked up by a stream of compressed air, approaches the nozzle, it is moistened with water, mixed in the mixer, turned into a solution and ejected with a strong jet from the nozzle.
The amount of water supplied to the mixer is controlled by a valve. The dosage of water supplied to the mixture is checked by the color of the jet ejected from the nozzle and by the color of the applied shotcrete plaster.
With an excessive dosage of water (Fig. 132, a), a liquid solution is obtained that slides off the applied surface. If there is a lack of water (Fig. 132, b) in the mixture, the solution is not completely wetted and when ejected from the nozzle it generates a lot of dust.
Driver is obliged not only to monitor the operation of the cement gun and the air pressure, which must correspond to that specified in the machine’s passport, but also the presence of water in the tank; Periodically, 3-4 times per shift, he should blow out the air filter.
Shotcrete of surfaces is carried out by a team consisting of two plasterers of the 4th category, one plasterer of the 3rd category and a machinist of the 4th category.
The responsibilities of the unit include washing the shotcrete surfaces with water, preparing a dry mixture, loading it into a cement gun and gunning. During a shift, the link must shootcrete at least 100 m 2 surfaces.
In a properly equipped unit, productivity reaches 150 m 2 per shift with applied layer thickness 20 mm. With centralized preparation of the mixture, productivity increases.
Motor mechanic, In addition to managing the cement gun, he is also required to take part in loading the cement gun with mixture.
A 4th category plasterer washes surfaces, supervises the preparation of the mixture, applies a layer of mortar to the surface, tightens and removes hoses, identifies formed mortar plugs and eliminates them, monitors the operation of the machine, the quality of work and performs various auxiliary work.
The second plasterer of the 3rd category helps the first and, if necessary, replaces him; In addition, he is the liaison between the plasterer and the minder. With a 4th category plasterer, he prepares the dry mixture and loads the cement gun.
If the dry mixture is prepared on site, then a 3rd category plasterer delivers sifted sand and cement to the work site, pours them onto the striker and shovels them together with a 4th category plasterer, and loads the prepared mixture together with the mechanic into a cement gun.
If the surface of the shotcrete plaster needs to be rubbed down, then a 3rd or 2nd grade plasterer is additionally attached to the link. When performing improved plaster, a 3rd category plasterer works, and when performing simple plaster, a 2nd category plasterer works.
For work, it is necessary to prepare such an area that could be shotcrete during one work shift. The surface must be cleaned in advance and only moistened with water before applying shotcrete plaster.
It is recommended to plaster from top to bottom. Moreover, the thinner the layers of plaster applied and the more of them, the stronger the shotcrete plaster and the more reliably it will provide water and gas impermeability.
It is recommended to apply each new layer on top of the previous one after it has set, but not earlier than after 60 min. The first layer of shotcrete plaster is most often applied with a thickness of 15 mm, then it is leveled by cutting off individual irregularities with a spatula or trowel. The first layer is kept for 24 h, then it is moistened with water and a second layer is applied.
When shotcreting nozzleman holds the nozzle perpendicular to the surface at a distance of 70-80 cm from her. Smaller grains of sand in the solution quickly clog into pores and cavities and are the first to settle on the surface; Larger grains of sand, hitting small ones, compact them, but at the same time partially bounce off. As the layer of gunite plaster grows, large grains of sand also begin to sink into it. At first, the rebound of coarse sand reaches 20-25%, but gradually, as the layer is applied, it decreases. Basically, grains of sand bounce off without a cement layer, so the loss of binder is insignificant. Before starting work, the joints of the shotcrete areas should be thoroughly cleaned of settled dust and moistened with water.
To avoid shrinkage cracks and increase the durability of the applied shotcrete plaster, it requires appropriate care. Shotcrete areas should be protected from drafts, excessive solar heat and mechanical damage. It is best to cover the surfaces with two or three sheets of tarpaulin, overlapping one another. The tarpaulin should be pre-moistened with water; To constantly moisten the tarpaulin, you need to install a perforated tube above it through which water is supplied. Where shotcrete plaster is used in the form of ordinary plaster, it is recommended to moisten it for 5-7 days.
Every day after work, the cement gun, hoses and nozzles should be thoroughly cleaned; first blow with a stream of compressed air, and then, without disassembling the machine, clean all accessible places. Regularly, at least once a week, it is necessary to disassemble, clean and lubricate the machine, and wash its individual parts with kerosene. Uninterrupted operation of the unit is possible only with proper and timely care.
Safety precautions. Before starting work, the team servicing the cement gun must be briefed on labor safety rules.
Since an almost semi-dry mixture is ejected from a cement gun, plasterers need to wear goggles and a respirator. You should work in thick overalls and gloves. When working at height, workers are required to wear safety belts and securely tie themselves to reliable structural elements of buildings.
The plasterer must be careful to ensure that no one gets caught in the spray of gunite plaster.
All electrical wires going to the unit must be carefully insulated and placed in boxes if they run on the ground, or suspended above a person’s height, since the unit operates from a lighting network with a voltage of 220 V.
Scaffold decks must be strong and continuous. Before starting work, the plasterer must carefully check all hose connections and, during work, ensure that the air pressure in the cement gun does not exceed that specified in the instructions.
When removing solution plugs, workers not associated with this operation are prohibited from being near the hoses; the nozzle and open mortar hose must be directed in a direction that is safe for workers.
When disconnecting the hose, pressing the assembled unit and testing there should be no unauthorized persons near the unit.
Shotcrete and shotcrete
Shotcrete method consists of applying one or several protective layers of cement-sand mortar (shotcrete) to vertical, inclined and horizontal surfaces using a cement gun or a concrete mixture injected concrete syringe machine.
This method is used to strengthen the surfaces of thin-walled structures in one-sided formwork (domes, shell vaults, tanks), to apply a dense and waterproof protective layer of underground structures, as well as to seal seams, correct defects in concrete, and during repair and restoration work and for strengthening reinforced concrete structures.
High-quality cements are used for shotcrete. Under normal conditions, Portland cement grade 500 is used, and for grouting, creating waterproof linings and repairs, quick-hardening cement. The sand should be as clean, dry as possible and not contain grains larger than 8 mm. To speed up the setting of the mixture, additives are dissolved in the mixing water. The shotcrete equipment set consists of cement gun, compressor, water tank, air and material hoses and nozzles
A dry cement-sand mixture of the appropriate composition, prepared in a mixer, is loaded into a cement gun. Under a compressed air pressure of 2-3.5 kg/cm2, the mixture is fed through a material hose into the nozzle. At the same time, water from the tank enters the nozzle, the pressure of which should be 1-1.5 kgf/cm2 higher than in the cement gun. The moistened mixture, flying out of the nozzle at a speed of up to 100 m/s, hits the gunite surface and sticks to it. The result is a dense and durable layer. shotcrete. Some of the cement-sand mixture bounces off the surface and falls near the shotcrete site. This loss is called a rebound.
Ceilings are shotcrete in several layers, floors - the entire thickness at once.
With multi-layer shotcrete, the time between application of individual layers is determined by the construction laboratory. This time should be such that the previous layer of gunite does not collapse under the action of the mixture jet. On the other hand, to ensure the incorporation of a fresh layer into the previously applied one and their better adhesion, the maximum break should not exceed the setting time of the cement.
To reduce rebound, surfactants (sodium abietate, soap naft) are added to the mixing water, which increase the adhesive ability of the mixture.
Before gunning thin-walled structures, one-sided formwork is installed and secured, leaving one side open for applying gunite, and reinforcement is installed. Before applying protective linings, repairs and sealing, thoroughly clean and rinse the surfaces. To ensure better adhesion of the shotcrete layer to concrete, a notch is made on smooth surfaces. Before shotcreting, check the serviceability of all mechanisms, cleanliness and hose connections, and also apply a shotcrete sample to a portable wooden panel.
To obtain a dense shotcrete and reduce rebound, the nozzle during application should be kept at a distance of 0.7-1.0 m from the surface being shotcrete, and the mixture jet should be directed perpendicular to it. To obtain a layer of shotcrete of uniform thickness, the nozzle is moved in a circular motion during the application process.
Gunite is applied to vertical, inclined and curved surfaces from bottom to top. To prevent freshly applied shotcrete from slipping off, the water supply to the mixture and the thickness of the layers, which is controlled by beacons, are regulated. The optimal thickness of the shotcrete layer applied in one pass is 25-30 mm.
To obtain smooth surfaces concreted using shotcrete methods, immediately after applying the last layer it is smoothed and rubbed with steel trowels or trowels. Then the surface is ironed. After such processing, structures with smooth surfaces that are distinguished by density, water resistance and frost resistance are obtained.
Sprayed concrete method used for the construction of thin-walled structures, lining tunnels, grouting joints, as well as for correcting concrete defects and repair work. Unlike shotcrete The mixture applied by spraying contains, in addition to cement and sand, also crushed stone or gravel with a particle size of up to 25 mm.
Concrete is sprayed onto vertical, inclined and horizontal surfaces. Before starting work, install one-sided formwork and reinforcement, clean and wash the surfaces.
A set of equipment for applying sprayed concrete is mounted on a two-axle trailer (12-2). It includes a forced-action concrete mixer with a skip hoist, a multi-bucket elevator, a storage hopper, a C-630A type spraying machine, two water tanks, hoses, a nozzle and a compressor.
The dry mixture prepared in the mixer is fed by an elevator into the hopper, and the spraying machine is loaded from it. Under an air pressure of 4-5 kgf/cm2, the mixture is fed through a hose into a nozzle, into the mixing chamber of which water flows. The moistened mixture flies out of the nozzle at a speed of 120 m/s. The optimal distance between the concrete surface and the nozzle is 1-1.2 m. The rotational movements of the nozzle ensure a uniform layer thickness, which should be 50-70 mm.
Concreting using the sprayed concrete method ensures high quality surfaces of structures. Sprayed concrete has a dense structure, high strength, waterproof and frost-resistant. The shift productivity of the installation shown in 12-2, serviced by three workers, reaches 18-21 m3, which provides a very high output per person - 6-7 m3 per shift.
Welcome to CJSC "Structure Protection Service" - a team of professionals working in the field of protection and restoration of structures. Buildings and structures for civil, military, industrial and transport purposes are the basis of the economy of any state in the world. According to experts, a significant number of these objects, due to natural aging and corrosion, are in a pre-emergency and emergency condition, which creates the threat of man-made accidents and disasters. Constant monitoring of the condition of structures and timely measures for repair and restoration is the only way to resolve the issue of long-term and safe operation of fixed assets. One of the modern technological methods of protection and restoration of structures, widespread in the world and used by JSC "Structure Protection Service", is concrete shotcrete onto the surface of the structure being repaired or the object being protected. Shotcrete allows not only to restore operational characteristics, but also to adapt structures to changing natural and man-made conditions. Our experience and the experience of foreign companies in shotcrete indicates unlimited possibilities shotcrete in the field of general construction and repair and restoration work.
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ISO 9001-2000 |
The section "Regulatory Documents" provides regulatory and technical documentation for the application shotcrete concrete at marine, railway and road transport facilities, including those developed jointly with NIIZhB and OJSC TsNIIPromzdanii - Technical specifications TU 5745-001-16216892-06 "Guncrete" and "Guidelines for the use of shotcrete in the construction, repair and restoration of building structures of buildings and structures." These documents have been developed taking into account the requirements of the European Technical Specifications for shotcrete(European Specification for Sprayed Concrete). In the "Publications" section - articles from the American magazine "Shotcrete" about application experience shotcrete at various facilities in different parts of the world.
In the Russian market of professional construction work shotcrete takes a leading position, having established itself as a unique and indispensable technology for the repair and restoration of structures.
Shotcrete
Shotcrete is a method of applying one or several layers of cement-sand mortar or concrete mixture under compressed air pressure on vertical, inclined and horizontal surfaces.
Shotcrete is used to strengthen the surfaces of thin-walled structures in one-sided formwork (domes, shell vaults, tanks), to apply a dense and waterproof protective layer of underground structures, as well as to embed seams, correct defects in concrete, during repair and restoration work and to strengthen reinforced concrete designs.
Shotcrete is carried out using special equipment - a shotcrete installation. With the help of compressed air, the mixture is accelerated, flies out of the nozzle and, hitting the gunite surface, sticks to it.
Varieties
There are two types of applying working compositions to surfaces under pressure: dry and wet.
With the dry shotcrete method, the initial dry mixture in a suspended state is fed into the nozzle, where the mixture is mixed with mixing water. The mixture is mixed in the nozzle and then supplied under compressed air pressure to the surfaces to be concreted.
With the wet shotcrete method, a ready-made concrete mixture or solution enters the nozzle under compressed air pressure. In the nozzle, the mixture becomes suspended and is applied under pressure to the surfaces to be concreted.
Properties
The properties of the resulting shotcrete differ from those of conventional concrete or mortar. Shotcrete has a high density (approximately 2400 kg/m2), mechanical strength (40-70 MPa), water resistance (at least W8) and frost resistance (at least MP3 300).
By adjusting the composition of the mixture, special properties can be imparted. The high adhesion of shotcrete allows concrete to be laid using one-sided formwork. Transporting the shotcrete mixture through a flexible hose allows you to work in confined spaces.
concrete spraying The moisture content of the applied shotcrete based on VBC cement should be: 12-13% in non-reinforced shotcrete, 13-15% in reinforced shotcrete in the layer under the mesh and 11 - 13% in the remaining layers, and in shotcrete based on Portland cement: 9- 11% in unreinforced shotcrete, 11% in reinforced shotcrete in the layer under the mesh and 9% in surface layers. On the surface of a properly applied shotcrete layer there should be no dry spots resulting from a lack of water, and no slipping of the layer when there is excess water. The supply of dry mixture should be adjusted by changing the rotation speed of the cement gun feeding plate. Normally a nutritional plate should do about; 100 rpm When applying shotcrete to poorly prepared surfaces that have ledges: other unevenness, the number of revolutions per minute of the feeding plate should be increased to 120, and when laying the last leveling layer of shotcrete, reduced to 75. The thickness of the shotcrete and the number of layers in it are established in the project; the total thickness of the shotcrete must be at least 3 cm. The thickness of the individual layers of shotcrete is checked during the process of applying a thin steel needle, awl or wire by immersing them in different places. Places of such a puncture should be sealed immediately. Each subsequent layer of shotcrete should be applied when using VBC, after 30 minutes. after laying the previous layer, and when using Portland cements after setting. The layer of gunite applied before a break in work should be with a gradual decrease in thickness towards the boundary of the site on a strip of 1 -1.5 m. Before resuming work, the surface of this strip of gunite should be cleaned with a steel brush or a jet of compressed air and moistened with water. After this, the thickness of the previously laid layer must be brought to the required value. When draining water from the lining surface with drainage tubes, the latter must be sealed after the first layer of gunite has hardened. The protruding part of the tube should be cut flush with the first layer, and the remaining part should be caulked with expanding cement (VRC, gypsum-alumina, etc.). The thickness of the last layer of shotcrete should be such as to cover the ends of anchor rods, reinforcement and drainage pipes by at least 15 mm. Sand rebound and sand from sand pockets under the reinforcement during work should be removed by blowing out with compressed air. To grout a shotcrete surface, if necessary, apply a layer of shotcrete on fine sand no earlier than 2 hours when using shotcrete on VBC cement and no earlier than 12 hours, but no later than 24 hours. when using shotcrete on Portland cement. The surface of such a freshly laid layer must be immediately rubbed down. During the period of setting and hardening, shotcrete must be protected from freezing, drying out, shock, mechanical damage and chemical influences for: 6 hours. - when using VBC cement and 7 days - when using Portland cement, counting from the moment of its application.
Shotcreting of concrete mixture
A universal and economical method of restoring and strengthening structures is shotcrete. The company "GidroPromStroy" is ready to perform shotcrete work of any volume and complexity at affordable prices.
Surface shotcrete: definition and types
Shotcrete work is the application of a layer of concrete mortar to building structures under compressed air pressure. As a result of this, cement particles come into close interaction with the treated surface, and filling of cracks, cavities and small pores is achieved. The use of such technologies makes it possible to achieve higher strength, frost resistance and other positive qualities for buildings and structures.
Shotcrete work is carried out using two methods: dry and wet. In the first case, shotcrete - the installation is filled with cement and the necessary additives in the required ratio, without adding water. The flow of dry mixture in the nozzle is moistened, as a result of which the material can be continuously supplied to the surface to be treated. If this method is implemented, there is no need to maintain a certain fluidity and viscosity of the concrete mixture during transportation and during operation. The low moisture content allows such shotcrete to be applied without thickness restrictions, including on vertical and ceiling surfaces.
When wet shotcrete is used, a mixture of cement, fillers, additives and water is prepared in advance, after which it is pumped into the transport hose. Here, shotcrete installations also often have special nozzles. They can supply moisture or compressed air to the mixture. The wet shotcrete method allows the application of concrete layers no more than 150 mm thick. To obtain greater thickness, work is carried out in several stages.
Stages of work when gunning a surface
The procedure for carrying out shotcrete work is as follows:
depending on the characteristics of the object and the requirements for the surface, the optimal set of equipment is selected;
a mixture of cement and necessary additives is prepared;
the surface is prepared for the procedure of shotcrete walls, including its cleaning, removal of destroyed elements, destructive layers, roughening, blowing, washing, moistening, and in some cases, reinforcement;
the mixture is loaded into the installation and sprayed;
final surface treatment is carried out.
Specifications
Shotcrete, due to the high speed of supply of the solution (120-180 m/s) to the surface, allows you to obtain a durable layer of concrete with unique properties. Shotcrete concrete has a significantly longer service life than conventional concrete; it is characterized by increased mechanical strength, water resistance and frost resistance. When repairing concrete using shotcrete technologies, it is possible to obtain surfaces with different structures.
Specialists from GidroPromStroy LLC are ready to inspect your facility, select suitable equipment, the composition of the concrete mixture and carry out shotcrete work at a low price.
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Shotcrete and Shotcrete Technology shotcrete, concrete repair, lining |
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Shotcrete [from lat. (tec) tor (ium) - plaster and (con) cret (us) - compacted], a method of concrete work in which the concrete mixture is applied layer by layer to the concrete surface under compressed air pressure. Shotcrete is carried out using a shotcrete installation. (TSE. T. 26. M., “Soviet Encyclopedia”, 1977.) The material obtained as a result of shotcrete is called shotcrete. Shotcrete is used: during the construction of thin-walled reinforced concrete structures (shells, vaults, tanks, etc.); when installing lining in tunnels; strengthening slopes, slopes, coastlines; for waterproofing and sealing joints of prefabricated structural elements; when repairing and strengthening concrete and reinforced concrete structures and products, etc. There are two methods of shotcrete – “dry” and “wet” method. The “wet” method, in turn, is divided into “wet” with a continuous flow and “wet” with a discharged flow. Each of the listed methods has its own advantages and disadvantages. "Dry" shotcrete The “dry” shotcrete method was first used at the beginning of the twentieth century. With this method, a dry mixture of cement, aggregates (sand, crushed stone) and additives (if necessary) is first prepared. The mixture is fed into the installation for “dry” shotcrete. The mixture is supplied with compressed air through a hose to the nozzle, wetted in it with water supplied through another hose, and at high speed (130-170 m/sec) is thrown onto the shotcrete surface.
The process of building up a layer of shotcrete occurs as follows: in the first period (measured in milliseconds) almost the entire mixture bounces off the surface; only laitance remains on the surface, which forms an adhesive layer; the next moment the smallest aggregate remains on the surface, everything else bounces off; subsequently, increasingly larger aggregate remains on the surface until the rebound stabilizes. The resulting shotcrete layer has the following positive properties due to the application method: high adhesion due to the fact that the boundary layer is formed by cement laitance with the finest aggregate; high density and cohesion due to the high flight speed of the mixture particles - the particles are literally driven into the already applied layer of shotcrete; optimal water-cement ratio - an experienced nozzle operator supplies the amount of water not exceeding that required for the hydration reaction; possibility of applying a layer of up to 10-15 cm in one pass - high consistency of the applied composition, everything that is poorly fixed bounces off. However, up to 25% of the mixture goes into rebound “Wet” continuous flow shotcrete “Wet” shotcrete appeared half a century later. This was due, first of all, to the development of construction chemistry. With this method, the finished concrete mixture is fed into a “wet” shotcrete installation (concrete pump) and hydraulically (in a continuous flow) is supplied through a hose to the nozzle. Compressed air is supplied to the nozzle through another hose, with the help of which a continuous flow of the mixture is broken and delivered to the shotcrete surface. The speed at which spraying is carried out is significantly lower. As a result, the amount of rebound is reduced to 10%.
High quality shotcrete is achieved by introducing additives: adhesion to the surface - through forced application of an adhesive layer; applying a thick layer - by introducing setting accelerators, the solution of which is supplied to the nozzle with a separate hose; optimal water-cement ratio - using plasticizers. “Wet” shotcrete is more consistent with the industrial construction method. The concrete mixture can be prepared at a specialized enterprise (concrete plant), delivered by a concrete mixer truck, and when applying it, the qualifications of the nozzle player play a lesser role. However, the need to introduce additives significantly increases the cost of the applied mixture. In addition, transportation of mixed concrete through a hose eliminates the possibility of even short-term breaks in shotcrete without the labor-intensive operation of washing the hose (the concrete mixture sets in the hose). “Wet” shotcrete in a discharged flow With this method, the finished concrete mixture is placed in a pneumatic concrete pump and, using compressed air, is delivered to a nozzle from where it is thrown to the surface at high speed. This method occupies an intermediate position between the above methods. It is possible to prepare a ready-made (mixed) mixture at a concrete plant and there is no need to introduce plasticizers. The disadvantages of this method include high rebound of up to 25%, the need to apply an adhesive layer and the use of setting accelerators, and mandatory washing of the material hose during breaks in work. |
Dear colleagues, most likely this article will be relevant for construction companies wishing to carry out repair work on their own, as well as for operators who have quite large production and residential areas on their books, which are, to put it mildly, in poor condition.
I can’t resist the temptation to tell you about my first practical acquaintance with this amazing technology. It was about 25 years ago, in Azerbaijan, not far from Baku. Don’t be surprised, because it was there that there was then a kind of center for the development of offshore oil fields, and this technology was used in this industry too.
More specifically, in this way, large-diameter oil and gas pipes were weighted to lay them along the bottom of the seas so that they would not float up or move during waves. In short, in a huge workshop, a tube with a diameter of about 1 meter and a length of 20 meters was attached to a stand, a reinforcement frame was welded, and the pipe slowly rotated. Shotcrete machines with manipulators moved along the rails, next to the pipe, and gunite concrete was sprayed automatically in layers. The equipment was all German.
Well, in principle, I think everything is clear to you. I was invited just to look, or rather, I asked for it myself. Say. that I was delighted is an understatement; as a concrete worker, I was simply “shocked” by what I saw, of course in the good sense of the word. Of course, I previously knew in general terms about this technology, but what I saw amazed me with its technological splendor, clear organization of the process and, of course, excellent “German quality”. Well, of course, I didn’t fail to “jump in” and give some useful advice to the Germans, of course “on little things”, which of course they were incredibly surprised by, but after consulting with me they agreed, and so we, too, are “not cut out for it.”
And since then I have simply been “in love” with this technology. Sorry if anything is off topic. Well, okay, let's move on.
To begin with, just a few general provisions. Shotcrete (Latin tor - “plaster” + cret - “compacted”) - application to the surface of concrete, reinforced concrete. or other structures of a layer of concrete or other mortars (plaster, concrete mixture, clay and other repair compounds).Gunite concrete
or the shotcrete mixture is applied under compressed air pressure, as a result of which cement particles interact tightly with the surface of the structure, filling cracks, cavities, tiny pores or simply the surface of the product.
The result of shotcrete is an increase in the strength, density, water resistance, and frost resistance of the surface layer of products.
Most often, cement-sand mortar is used as shotcrete in a ratio of 1:2 - 1:6. The aggregate size is no more than 8 mm. Cement grade not lower than 400.
The main tool for shotcrete is a cement gun, which delivers the solution at a speed of 80-100 m/s. The air pressure is 1.5-5.0 atm.
But now, before moving on to specifics, I would advise you to watch several short videos on this topic, much in our conversation with you will become more clear, solook
Watch the video. This is the simplest installation, I would like you to see the process itself; with this simple installation you can carry out minor repairs and carry out plastering work. Next I will talk about this installation, by the way, this is wet shotcrete, a shotcrete mixture is supplied through a “thick” hose, a ready-to-use mortar mixture, and through a thin hose compressed air, which “sprays” this mixture onto the surface with force, is an ideal option for beginners for the first time master this technology.
Watch the video. This is dry shotcrete – appliedshotcrete concrete layers of shotcrete installation - The process of applying layers of concrete with a shotcrete machine is shown, obviously the process of repairing a hydraulic structure is underway. Please note that the dry mixture along with air is supplied through the large hose, and water is supplied through the smaller hose along with additives.
Watch the video. Wet shotcrete of the pre-reinforced basement section of the building, which is obviously located on a fairdilapidated foundation , shotcrete concrete is applied, which contains coarse aggregate, with a fraction of no more than 8 mm. The capabilities of this technology are very clearly shown; it is almost impossible to do this work in any other way.
Watch the video. This film may not be directly related to today's topic, but I really wanted you to watch it. This is a repair mixture for waterproofing basements and foundations with the addition of Penetron. The principle of operation is very popularly shown. The principle of capillaries in concrete and the influence of water-repellent penetrating compounds are explained very simply on an accessible but completely scientific level - this significantly increases the water resistance of concrete structures.
Installation for spraying onto the surface of building structures and structures mortar and concrete mixture - shotcrete, which has water resistance and increased strength, elasticity, fire resistance, frost resistance, acid resistance, etc. Gun cement is used in the construction and repair of hydraulic, industrial and civil structures, and also as a sandblaster.
Technological shotcrete process consists of introducing a dry concrete mixture through a cement gun feeder into a rubber hose, through which it is supplied with a stream of compressed air to the place of work. At the outlet of the hose, the mixture is moistened in a special. water nozzle, the edges are supplied under pressure from a centrifugal pump or water tank to another hose. The moistened mixture flies out of the nozzle at a speed of 50-70 m/sec, covers the surface, building up a layer of shotcrete on it. Ch. The indicator of a cement gun is the productivity of the dry mixture in m3/hour.
The C-630A model cement gun has two chambers instead of a sluice drum: a sluice chamber (upper) and a working chamber (lower). The chambers are equipped with bell valves, with the help of which you can load the upper chamber and transfer the mixture to the lower one without interrupting the process. process. The mixture is fed into the material hose by a disc feeder located in the lower chamber and rotated by an air motor. The design of the S-630A cement gun allows the use of aggregate with a particle size of up to 52 mm at a humidity of up to 6-8%.
Cement-a gun SB-117 (TU 22-3705-76) consists of a loading hopper, a drum, a drive mechanism, a material hose, and a control panel.
Workers serving cement-cannon or concrete syringe machine, must wear special safety glasses. When working with cement-cannon or...
To apply shotcrete plaster, use cement-cannon. ... From the compressor, compressed air is supplied directly to cement-cannon and for.
The main unit is cement-a gun SB-13 or S-117, which has almost the same operating principle.
For applying shotcrete it is used cement-guns, for applying syringe concrete - concrete syringe machines.
Recently, when installing fastenings for pit walls, the shotcrete method has been introduced using cement-guns or concrete syringe machines.
The shotcrete equipment set consists of cement-guns, compressor, water tank, air and material hoses and nozzles.
11. During operation of the mortar pump and cement-guns Do not bend the hoses or tighten the seals.
The bitumen-gasoline solution is applied mechanically using cement-guns or a simple installation consisting of a compressor, a sealed container...
In addition, water fills the intergranular spaces cement stone, pores and capillaries of solutions (concrete). ... Cement-a gun and concrete syringe machine.
The shotcrete solution is applied to the surface using cement-guns. During work, the air pressure in cement-cannon 25...0.3, MPa (with hose length 30...40 m...
Fine concrete is usually placed using shotcrete methods using cement-guns or pneumatic concrete.
Activated shotcrete (AT) is applied to the surface using cement-guns, During work, the air pressure in cement-cannon should be around 250...
Dry cement-sand mixture (1:2) is supplied pneumatically through a hose from cement-guns with its dosage using a plate feeder; it mixes with water in the plaster nozzle...
Shotcrete - a method of applying thin layers cement solution on the surface using compressed air from cement-guns. Shotcrete cement The layer has a high...
Cement-a gun SB-117. Direct-flow diaphragm mortar pumps with pneumatic attachment. Plastering and troweling machines SO-86A and SO-112A.
Between the nozzle and the operator cement-guns or spray installations must have visual or audio communication.
Cement-a gun and concrete syringe machine. When installing formwork and reinforcement... In this regard, workers are allowed to start concreting in winter conditions only after passing....
Cement-a gun consists of a cylindrical tank with a conical valve for loading dry mixture and an outlet for dispensing it, a flexible hose and a nozzle.
...cement- high-density sand waterproofing, including activated gunite, using an installation for spraying concrete mixture SB-67 and cement-a gun SB-117.
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