The pumped concrete should meet the pumpability requirements, and if necessary, the mix ratio of the pumped concrete should be determined through test pumping.
The ratio of the large particle size of the coarse aggregate to the diameter of the conveying pipe should be: when the pumping height is below 50m, it should not be greater than 1:3 for gravel and 1:2.5 for pebbles; when the pumping height is 50-100m, It should be in the range of 1:3 to 1:4; when the pumping height is above 100m, it should be between 1:4 and 1:5. The content of needle-like particles should not exceed 10%
2. After the concrete pump is started, an appropriate amount of water should be pumped first to wet the hopper, concrete cylinder and conveying pipe of the concrete pump and other parts that are in direct contact with the concrete.
After pumping water, use one of the following methods to lubricate the above parts: pumping cement slurry; pumping 1:2 cement mortar; pumping cement mortar with other ingredients except coarse aggregate. The grout or cement mortar used for lubrication should be dispersed and not poured in the same place.
3. When starting to pump, the concrete pump should be running at a slow and uniform speed, and then gradually accelerate. At the same time, the pressure of the concrete pump and the working conditions of each system should be observed. After each system works normally, the pump can be pumped at a normal speed.
4. The concrete pumping work should be carried out as continuously as possible. The piston of the concrete cylinder should be kept running with a large stroke, so as to exert the high efficiency of the concrete pump and make the concrete cylinder wear evenly in the length direction.