The concrete spraying machine has the advantages of high mechanization, simple process and high production efficiency. It is widely used in underground and ground concrete projects in construction, municipal, railway, mining and other industries. It has been widely used in many countries and has shown good technical and economic benefits.
According to different methods of adding water to concrete mix, it can be divided into dry type, wet type and semi-wet type between the two
1 dry type. According to a certain proportion of cement and aggregate, after being evenly mixed, it is blown to the nozzle by compressed air, mixed with pressurized water from the pressure water tank, and then ejected. The construction method in this way is simple and the speed is fast, but the dust is too large, the amount of rebound of the spray material is large, and high-grade cement is used. Most of the domestic production is dry.
2 wet type. Entering the jet is a concrete mix that has been added with water. Therefore, the dust content in the injection is low, and the amount of rebound is also reduced, which is an ideal injection method. However, the wet material tends to condense in the tank and the pipeline, causing troubles of clogging and cleaning, and thus has not been promoted.
The quality of concrete jets has a lot to do with the mix ratio of the mix. The specific requirements are:
1. Cement. Grade 32.5 Portland cement should be used;
2. Aggregate. Should be sieved before use, its maximum particle size should not exceed 20mm; its moisture content should be controlled within 5% to 8% (volume fraction);
3. Accelerator. The blending amount is 3% to 4% of the mass of the cement and should be added before spraying;
4. Mixing ratio of concrete mix. Cement: Sand: Stone = 1:2:2 ~ 1:2: 2.5 is better.