With the application of wet concrete spraying technology, various countries have developed a series of wet concrete spraying machines. According to the working principle of wet concrete spraying machines, they are divided into two categories: pumping type and pneumatic type.
2.1 Pumping type
2.1.1 Plunger pump type wet spray machine
As shown in Figure 1, this kind of wet spray machine uses a plunger As the basic body of the wet concrete spraying machine, the concrete pump is equipped with a nozzle at the outlet of the delivery pipe and compressed air is introduced here to spray the concrete. This type of wet spray machine is generally bulkier, but has a long conveying distance. Used in some large-scale water conservancy projects such as Ertan and Xiaolangdi, such as the Robojet041 concrete spraying machine of the Swiss MEYNADIER company.
2.1.2 Screw pump type wet spray machine
As shown in Figure 2, this wet spray machine is based on the change in the volume of the joint angle space when the screw and the stator sleeve mesh with each other. Conveying materials. This type includes the SB-3 wet spray from German UELMAT company. Relevant units in our country have also conducted research and development. The main disadvantages of this model are low productivity and serious wear of the screw and stator sleeve, so its application range is limited.
2.1.3 Hose squeeze pump wet spray machine
As shown in Figure 3, this wet spray machine consists of a mixing bucket, a pumping hose, a pump body and a conveyor Composed of material tubes and other components. The pump body is cylindrical, and the planetary transmission mechanism in the middle drives two rollers to rotate, continuously squeezing the wet material in the pumping pipe, causing it to enter the feeding pipe and be sent out under pressure. Japan's Jitong PC08-60M CHALLENGE concrete spraying machine belongs to this type of wet spraying machine. It is reported that this spraying machine has been widely used abroad, but judging from the introduction of Guoxian in recent years, it has been rarely used. The main problem is the short life of the extruded tube.
2.2 Air-fed wet concrete spraying machine
This type of wet spraying machine uses compressed air to transport the material in the hose in the form of a "thin flow" to the nozzle and spray it directly. . Figure 4 shows the working principle diagram of the British COMPERNASS-208 wet spray machine. This machine has two tanks side by side, one for spraying and one for material preparation. There is a horizontal screw conveyor at the bottom of each tank. Compressed air is introduced into the spray tank, and the wet mixture is sent into the feeding pipe through the spiral. At the nozzle, the compressed air introduced through the air ring causes the mixture to be sprayed out. The disadvantage of this kind of wet spray machine is that it is troublesome to add materials into the tank, and it is also inconvenient to clean the tank.
Figure 5 shows the working principle diagram of the Japanese Deskumarn wet spray machine. The wet spray is made of two vertical tanks. The upper tank is for mixing materials and the lower tank is for spraying. Both the upper and lower tanks have sealed doors that open and close alternately to achieve continuous spraying. There is a horizontal screw at the bottom of the lower tank that drives the wet mixture into the material tube and ejects it out. The disadvantage of this wet spray machine is the large feeding height. Relatively bulky.
Figure 6 shows the working principle diagram of the Swiss Ava 280 wet spray machine. The machine has a rotor structure and adopts a hydraulic drive device. The load variable pump drives the rotor to rotate through the hydraulic motor, and the rotation speed is adjustable, so that the injection volume is adjustable. The hydraulic rotor is used to rotate and the speed is adjusted, so that the injection amount is adjustable. A hydraulic rotor pressing mechanism is adopted, and the pressing force is adjustable. During operation, the wet mixture in the hopper falls into the rotor hole. After rotating 180°, the hole is connected to the compressed air inlet. The wet mixture is pressed to the discharge pipe in a suspended state, and mixes with the liquid in the nozzle mixing chamber. After the quick-setting agent is quickly and thoroughly mixed, it is sprayed from the nozzle at high speed. The disadvantages of this machine are large equipment investment and heavy maintenance workload. Since its dead weight reaches more than 2t, its maneuverability is poor.
3 Domestic wet concrete spraying machine
3.1 SPZ-6 wet concrete spraying machine
The SPZ-6 wet concrete spraying machine is developed by Beijing Mining and Metallurgy Research A gas-feed rotor-type wet concrete spraying machine successfully developed by the General Institute is shown in Figure 7. The working principle is similar to the Swiss Aliva 280 model. Its rotor is rotated by an electric motor through a reducer. This machine has low equipment investment, high productivity, light weight and good maneuverability.
The SPZ-6 wet concrete spraying machine conducted industrial experiments at the Daliushu construction site of Beijing Urban Construction and Gansu Jinchuan Nonferrous Metals Company, and achieved excellent results. In December 1996, it passed the China Nonferrous Metals The technical appraisal of the Industrial Corporation was granted national patent rights in August 1998 (Patent No. ZL98207689.4).
3.2 TK-961 wet concrete spraying machine
The TK-961 wet concrete spraying machine is a rotor piston wet spraying machine developed by the Southwest Branch of the Railway Science Research Institute in recent years. , as shown in Figure 8. The machine uses a set of pistons to push the wet material to the mixing chamber at the top of the machine. After mixing with air, it is transported to the nozzle through the hose, where the accelerator is mixed with the nozzle and then sprayed out. The main advantages of this machine are no residual air emissions, good feeding continuity, and excellent control over the workability of concrete. It is reported that it has been applied in projects such as Baocheng Branch Line and Yuchang Expressway. And obtained the national patent (Patent No. ZL9232716.5).
3.3 Impeller-type wet concrete spraying machine
The impeller-type wet concrete spraying machine is a wet spraying machine developed by Anqing Hengte Engineering Machinery Research Institute, as shown in Figure 9. This uses an impeller feeding device (Patent No. ZL96202768.5), which has the advantages of reliable operation, long service life, and adaptability to a large range of aggregate particle sizes. At present, AH series products have been produced.
4 Some problems that need to be solved in the promotion and application of wet concrete spraying machines
At present, due to the obvious advantages of wet spraying technology, wet concrete spraying machines are increasingly used in various projects. Come more and more. However, due to the existence of some problems that need to be solved, the promotion and application of wet concrete spraying machines have been hindered to a certain extent, so that in our country, the current main method of spraying concrete operations is still dry spraying.
(1) Wet concrete spraying machines mostly use liquid accelerating setting agents. The prices of imported and joint venture products are relatively high (up to RMB 6,000-8,000/t), while domestic liquid accelerators are not yet produced. The corresponding powdery quick-setting agent for dry spraying is sold at a low price (more than 1,000 yuan/t).
(2) Labor costs are low and people’s environmental awareness needs to be improved.
(3) When wet concrete spraying machines operate, equipment investment is more complicated, and operation and maintenance are not as convenient as dry spraying machines.
(4) When using a wet concrete spraying machine, the equipment investment is relatively high.
The above factors cause the construction cost of wet sprayed concrete to be higher than the construction cost of dry sprayed concrete, which limits the promotion of wet concrete spraying machines in China to a certain extent. However, with the strengthening of environmental awareness and people's higher requirements for the quality of shotcrete construction, wet concrete sprayers will increasingly replace dry concrete sprayers and become the main machine for shotcrete operations.