The Development of Wet Spray Machine:
In fact, at the beginning, the first concrete industry appeared in the concrete industry. As early as 1992, the foreign endeavor Aliva Company developed a dry rotor concrete jet. In 1947, the Federal German BSM Company developed a two-tank dry concrete jet. Later, the United Kingdom, the former Soviet Union, Japan and other developed a variety of dry concrete jets. In the 1960s, the country began to develop concrete spraying equipment.
The main advantages of dry concrete jets are long conveyor intervals, simple equipment and durability. However, since it mixes the dry mixed concrete nozzle with water, the construction dust and rebound are large, and the dust generated by the dry spray operation endangers the health of workers, especially in the window and roadway engineering. Dust pollution is more serious.
Since the 1960s, in the developed countries of the West, wet spray technology has gradually been implemented, and various wet spray machines have been developed. The basic principle of wet spray is to add the finished concrete with water to the wet spray machine. It is conveyed to the nozzle and is sprayed to the construction surface after being accelerated by the accelerator.
At present, in the western countries, wet spray machines have gradually become the main shotcrete work tools. In China, dry spray machines are still the main spray equipment for various reasons. However, as people's environmental awareness has increased and the quality requirements for shotcrete have progressed, more and more wet spray machines have been used. In some large-scale water conservancy projects that are internationally tendered, such as Ertan Hydropower Station, Yellow River Xiaolangdi Project, and Three Gorges Project, wet concrete spraying operations are used. The various wet concrete sprayers currently used in China are mostly imported from abroad. In recent years. Some domestic units have also begun to develop several wet spray machines, but the scale of production has yet to be expanded.
In summary, the main advantages of wet spray machines are:
(1) The dust concentration outside the machine and outside the nozzle is greatly reduced, and the harm to workers' health is eliminated.
(2) High productivity. Dry concrete jets generally do not exceed 5 m3/h. With the wet spray machine, it can reach 10m3/h for manual operation and 20m3/h for robot operation.
(3) Low rebound. When dry sprayed, the concrete rebound can reach 15%-50%. Wet spray technology. The rebound rate can be reduced to less than 10%.
(4) When wet spraying, since the water-cement ratio is easy to control and the degree of concrete is not high, the quality of the shotcrete can be greatly improved, and the homogeneity of the concrete can be improved. When dry-spraying, the water-cement ratio of the concrete is sprayed. The hand is adjusted according to experience and visual inspection. The quality of the concrete depends to a large extent on whether the operator is operating correctly or not.