Types and development of the hottest wet concrete

  • Detail

The type and development of wet concrete sprayer Abstract This paper introduces the type and development process of wet concrete sprayer. Use at home and abroad 2. Sample interception methods and main advantages and disadvantages. The working principles of various types of wet concrete sprayers abroad are emphatically introduced. At the same time, several representative wet concrete sprayers developed in China in recent years are also introduced

key words: type and principle development of wet concrete sprayer

concrete sprayer is a kind of construction equipment widely used in underground engineering, geotechnical engineering, municipal engineering and other fields. It uses compressed air or other power to transport the mixture mixed in a certain proportion through the pipeline and spray it at a high speed to the sprayed surface for solidification and hardening, so as to form a concrete support layer. In recent years, spray wet concrete support layer. In recent years, spray concrete technology has shown vigorous vitality in various construction fields with its simple process, unique effect, economic cost and wide range of uses

1 development of wet concrete sprayers at home and abroad

abroad, aliva company developed a dry rotor concrete sprayer in 1992. In 1947, BSM company of Federal Germany developed a double tank dry concrete sprayer. After that, Britain, the former Soviet Union and Japan successively developed various dry-type concrete spraying machines

China began to develop concrete spraying equipment in the 1960s. It has successively developed various dry concrete sprayers, such as metallurgical construction-65 (Construction Research Institute of the Ministry of metallurgical industry), pH (Yangzhou Machinery Plant), hlp-701 (Coal Research Institute)

the main advantages of dry concrete spraying are long conveying distance, simple equipment and durability. However, because it mixes the outside of the dry mixing concrete nozzle with water, the construction dust has a large rebound. The dust produced by dry spraying is harmful to the health of workers, especially in the small window roadway project. Dust pollution is more serious

since the 1960s, in the western developed countries, the wet shotcreting technology has been gradually implemented, and various wet concrete shotcreting methods have been developed. The basic principle of the so-called wet shotcreting is to add the finished concrete mixed with water into the wet shotcreting machine, transport it to the nozzle, and spray it to the construction surface after adding accelerator

at present, in western countries, wet concrete sprayers have gradually become the main shotcrete machines and tools (see Table 1)

Table 1 proportion of dry spraying and wet spraying in shotcrete operations in some western countries

national wet spraying (%) dry spraying (%)

France 6040

Italy 9010

Japan 8020

Norway 991

Switzerland 6535

United States 6040

in China, At present, due to various reasons, dry spraying machine is still the main spraying equipment. However, with the enhancement of people's awareness of environmental protection and the improvement of the quality requirements for shotcrete, more and more wet concrete sprayers have been put into use. In some large-scale water conservancy projects subject to international bidding, such as Ertan Hydropower Station, Xiaolangdi Project on the Yellow River, Three Gorges project, etc., wet concrete spraying is adopted. At present, various wet concrete spraying machines used in China are mostly imported equipment from abroad. In recent years. Some domestic units have also begun to develop several wet concrete sprayers, but the production scale still needs to be expanded. To sum up, the main advantages of wet concrete spraying machine are:

(1) the dust concentration beside the machine and outside the nozzle is greatly reduced, and the harm to workers' health is eliminated

(2) high productivity. Dry concrete sprayer shall not exceed 5m/h generally. The wet concrete sprayer can reach 10m/h during manual operation; When the manipulator is used for operation, it can reach 20m/h

(3) low springback. During dry spraying, the concrete resilience can reach 15%-50%. Adopt wet spraying technology. The rebound rate can be reduced to less than 10%

(4) during wet spraying, because the water cement ratio is easy to control and the concrete does not melt, the mouth quality of sprayed concrete can be greatly improved and the uniformity of concrete can be improved. During dry spraying, the water cement ratio of concrete is adjusted by the sprayer according to experience and visual inspection, and the quality of concrete largely depends on the correct operation of the sprayer

2 types and working principle of wet concrete spraying machine

with the application of wet concrete spraying technology, countries have developed a series of wet concrete spraying machines. According to the working principle of wet concrete sprayer, the concrete can be divided into two types: pumping type and pneumatic type

2.1 pumping type

2.1.1 plunger pump wet shotcreting machine

as shown in Figure 1, this kind of wet shotcreting machine takes the plunger concrete pump as the basic body of the wet concrete shotcreting machine, installs a nozzle at the outlet of the delivery pipe, and injects compressed air here to spray the concrete. This kind of wet spraying machine is generally bulky, but the conveying distance is long. However, it still needs to be improved in some fields, such as the robojet041 concrete sprayer of Swiss menadier company, which is used in some large-scale hydraulic projects such as beach and Xiaolangdi

2.1.2 screw pump wet sprayer

as shown in Figure 2, this wet sprayer transports materials based on the change of the volume of the corner space when the screw and the stator sleeve mesh with each other. This type includes SB-3 wet spray of German uelmat company. Relevant units in China have also carried out research and development. The main disadvantages of this model are low productivity, serious wear of screw and stator sleeve, so its application range is not large

2.1.3 hose extrusion pump wet sprayer

as shown in Figure 3, this wet sprayer is composed of mixing bucket, pumping hose, pump body, feeding pipe and other components. The pump body is cylindrical, and the planetary transmission mechanism in the middle drives two rollers to rotate, continuously extruding the wet material in the pumping pipe, so that it enters the feeding pipe and is sent out. Japanese Jidong PCM charlenge concrete sprayer belongs to this type of wet sprayer. It is reported that this sprayer was widely used abroad, but it has been rarely used in recent years according to the introduction of Guoxian. The main problem is that the service life of the extrusion pipe is short

2.2 air delivered wet concrete sprayer

this kind of wet concrete sprayer uses compressed air to transport materials in the form of "thin flow" in the hose to the nozzle for direct spraying. As shown in Figure 4, the working principle diagram of the UK compernass-208 wet sprayer is shown. The machine consists of two tanks side by side, one for injection and one for material preparation. There is a horizontal screw conveyor at the bottom of the tank. Compressed air is introduced into the spray tank, and the wet mixture is sent to the feed pipe through the screw. At the nozzle, the mixture is sprayed out through the compressed air introduced by the air ring. The disadvantage of this wet spraying machine is that it is troublesome to add materials to the tank and inconvenient to clean the tank

Figure 5 shows the working principle diagram of Japanese desguman wet sprayer. The wet spray nozzle consists of two vertical tanks. The upper tank mixes materials and the lower tank sprays. The upper and lower tanks are provided with sealing door, which is opened and closed alternately to realize continuous spraying. There is a horizontal screw at the bottom of the lower tank to drive the wet mixture into the material pipe and spray it out. The disadvantage of this wet spraying machine is that the feeding height is large. It is rather bulky

Figure 6 shows the working principle diagram of Swiss AVA 280 wet sprayer. The machine is of rotor structure and adopts hydraulic driving device. The load variable pump drives the rotor to rotate through the hydraulic motor. The speed is adjustable, so that the injection amount is adjustable. The hydraulic rotor is used to rotate, and the speed is adjustable, so that the injection amount can be adjusted. The hydraulic rotor pressing mechanism is adopted, and the pressing force is adjustable. During operation, the wet mixture in the hopper falls into the material hole of the rotor, which is connected with the compressed air inlet after being rotated 180 degrees. The wet mixture is then pressed to the discharge pipe in a suspended state. After being quickly and fully mixed with the liquid accelerator in the nozzle mixing chamber, it is ejected from the nozzle at a high speed. The disadvantages of this machine are large equipment investment and heavy maintenance workload. Since the self weight reaches more than 2T, the production process has a great impact on the safety of materials and poor mobility

3 domestic wet concrete sprayer

3.1 SPZ-6 wet concrete sprayer

spz-6 wet concrete sprayer is an air fed rotor type wet concrete sprayer successfully developed by Beijing Research Institute of mining and metallurgy, as shown in Figure 7. The working principle of this model is similar to that of the Ariva 280 model in Switzerland. Its rotor is driven by the motor through the reducer. The machine has the advantages of low equipment investment, high productivity, light weight and good mobility

spz-6 wet concrete sprayer has been tested in Daliushu construction site of Beijing urban construction and Gansu Jinchuan Nonferrous Metals Company, and achieved excellent results. It passed the technical appraisal of China Nonferrous Metals Industry Corporation in December, 1996 and obtained the national patent right (Patent No.: zl.4) in August, 1998

3.2 tk-961 wet concrete sprayer

tk-961 wet concrete sprayer is a rotor piston wet sprayer developed by Southwest Branch of Academy of Railway Sciences in recent years, as shown in Figure 8. The machine uses a group of pistons to push the wet barrier material to the mixing chamber on the top of the machine. After mixing with air, it is conveyed to the nozzle through a hose. At the nozzle, it is sprayed after adding a coagulant that pays more attention to the coordination and development with the ecological environment and resources. The main advantages of this machine are no residual gas discharge, good feeding continuity, and good workability of concrete. It is reported that it has been applied in Baoji Chengdu branch line, Chongqing Changsha Expressway and other projects. And obtained the national patent (Patent No.: zl.5)

3.3 impeller wet concrete sprayer

impeller wet concrete sprayer is a wet sprayer developed by Anqing Hengte Engineering Machinery Research Institute, as shown in Figure 9. This adopts an impeller feeding device (Patent No.: zl.5), which has the advantages of reliable operation, long service life and large aggregate size range. At present, ah series products have been produced

4 some problems to be solved in the popularization and application of wet concrete spraying machine

at present, due to the obvious advantages of wet spraying technology, wet concrete spraying machine is more and more used in various projects. However, there are still some problems to be solved, which has hindered the popularization and application of wet concrete spraying machine, so that in China, the main spraying concrete operation mode is still dry spraying

(1) liquid accelerator is mostly used in wet concrete spraying machine. The price of imported and joint venture products is relatively high (up to yuan/t), while the domestic liquid accelerator has not been produced yet. The price of the corresponding dry spray powdered accelerator is low (more than 1000 yuan/t)

(2) low labor cost and people's awareness of environmental protection need to be improved

(3) during the operation of wet concrete spraying machine, the equipment investment is relatively complex, and the operation and maintenance are not as convenient as that of dry spraying machine

(4) when the wet concrete sprayer is used for operation, the equipment investment is high

the above factors cause the construction cost of wet shotcrete to be higher than that of dry shotcrete, which limits the promotion of wet shotcrete in China to a certain extent. However, with the strengthening of environmental protection awareness and people's higher requirements for the construction quality of shotcrete, wet concrete sprayers will increasingly replace dry concrete sprayers and become the main equipment for shotcrete operations

Copyright © 2011 JIN SHI