Is there a difference between a concrete dry spray and a wet jet?
Dry spray: dry spray is to aggregate, cement and accelerating agent according to certain proportion dry mixing evenly, and then into the injection machine, dry with compressed air to aggregate in the suspended state in the hose pressure spray gun, then mix in the nozzle with high pressure water, with high speed jet into the rockface. The mechanical structure of dry spray is simpler, mechanical cleaning and fault handling are easy. But its drawback is easy to generate larger dust, the springback amount is big, water is controlled by the nozzle valve, water cement ratio control is difficult and is associated with the proficiency of handlers. Wet spray: according to the proportion of design is to aggregate, cement and water mixing evenly, with wet jet nozzle pressure, again after adding accelerator in nozzle jet. Wet shotcrete quality easy to control, little amount of dust and rebound in the injection process, should be development and application of the injection process, but the requirements for injection machine is high, more trouble mechanical cleaning and troubleshooting. It is not easy to use wet spray for the thick layer of soft rock and water seepage.
The tunnel jet concrete is divided into four kinds of spray, spray, wet and mixed spray according to the process flow. The main difference is that the processing procedure is different, especially the timing of the addition of water and the accelerator. Spray: it is to add a small amount of water to the aggregate, make it wet, add cement and mix, thus reducing the dust of the material, mixing and spray. But a large amount of water is still being added and guzzled at the shower head, and the jet process and the use of mechanical and dry jet technology. At present, the construction site is more using the spray technology. Mixed injection: it is also called the cement shell injection method, which is the first water mixed with water, and then the whole cement. Then add the second water and the water reducer and make the SCE mortar; Mix the other parts of the sand with the stone and the accelerator. The mixture is then applied to the mixing tube and then extruder. Mixed injection is the combination of the mixing process and the injection process, and the key is the cement coating (or sand, stone) shell technology. Mixed injection process using the main machinery and equipment and dry spray technology basic same, but the quality of concrete is relatively dry spray concrete quality is good, and the dust and rebound rate has greatly decreased. But there are more machines, more complicated processes, more mechanical cleaning and troubleshooting. Therefore, the hybrid jet technique is usually only used in the large and large section tunnel project.
Generally speaking, you have to look at the label on the machine, it will have a sign, or a big word "wet jet". In principle, the dry spray is put into a jet, which is mixed with water, and then added water to the shower head, and then sprayed with wind pressure. Wet shotcrete is in the mix (water) into the jet, after mixing in the nozzle and accelerator, and then under the action of wind pressure spray out, so as long as where the water, also can judge whether the wet spraying machine.
