(1) The concrete mixture has insufficient slurry, especially when the content of particles smaller than 0.315mm in the sand is less than 15%, the concrete mixture has poor cohesion and is not conducive to pumping. .
(2) The stone gradation is poor and the particle size is too large. The particle size of the stone is larger than one-third of the pump pipe. When pumping over a long distance, the stone particles The diameter is larger than a quarter of the pump pipe, and the excess diameter content should be reduced as much as possible. Generally, it should not be greater than 5% to prevent aggregates from accumulating each other during the pumping process and causing pipeline blockage. The fineness modulus of sand is required to be between 2.3 and 3.0. For medium sand in Zone 2, gravel with continuous particle gradation of 5mm to 25mm should be used. The content of needle-like flake particles should be <8%.
(3) The sand rate is improperly selected, and the sand rate is too small, resulting in some stones not being wrapped with mortar, or the sand rate is too large, and the amount of slurry wraps the aggregate surface The thickness is insufficient, the concrete mixture has no slurry, the concrete diverges, and the cohesion is poor.
(4) The water absorption rate of the aggregate is greater than 2%, resulting in slump loss of the concrete mixture, increased viscosity, difficulty in pumping, and pipe blockage. The high mud content of sand and stone results in a large amount of adsorption of water-reducing agent, a large slump loss of concrete, and poor fluidity, causing pipe blockage.
(5) The slump of concrete is not properly controlled. Excessive slump causes the separation of slurry and stone. During the pumping process, the slurry speed is faster than the stone, causing bone formation. The friction force of the material concentration increases and the pipe is blocked, the slump is too small, and the fluidity of the concrete mixture is poor, causing the pipe to be blocked.
(6) The pipeline layout is unreasonable. Air leakage at the pipeline interface reduces the pressure in the pipe and causes pipe blockage.
(7) The pump pipe is not thoroughly cleaned, there is hardened concrete in the pipe, or mortar is not used to moisten the pipe before pumping concrete.
(8) When the pumping process is interrupted, the concrete in the pipe loses fluidity during the intermittent time. Especially in high-temperature summers, pumping cannot be done for a long time.
(9) Adding water during the construction project and pursuing large slump one-sidedly will cause concrete segregation. Once pumping is suspended, it will cause pipe blockage.
(10) Improper operation by the pump truck operator.
(11) When transporting concrete, the tank truck does not rotate because the drum does not rotate, causing the concrete mixture to be uneven, the aggregate to sink, and the slurry to float. This occurs during pumping. Blocked pump. </p
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