Foreign body plugging

Theoretically, pipe plugging is easy to occur when three large stones meet and clamp on the same section. At this time, most of the section is occupied by stones, and the circulating area is very small. It is generally stipulated that the maximum particle size of stone and the inner diameter of pipe D: d < 1:3 (Note: this item is specified in the specification, which is 1:2.5 ~ 1:5 according to the conveying height and stone type), and a square grid is set on the pump hopper to prevent the mixing of oversized stone.

Poor concrete ratio

When the pressure gradient of the concrete mixture with poor ratio is large, the water will penetrate through the aggregate gap, so that the aggregate agglomerates and causes pipe blockage, which mostly occurs at the bending and reducing of the pipeline and the placement of hoses in the middle of the pipeline; In addition, when the water cement ratio of concrete is too large, it is easy to separate, resulting in the separation of mortar and aggregate and pipe blocking, which is mostly seen in the "segregation" pipe blocking during long-distance horizontal pumping and the lower end of vertical downward pipe laying. When the amount of cement is too small and the sand rate is too low, the workability of concrete is poor, the deformation is difficult, the friction resistance in the pipeline increases, and the pipe is very easy to be blocked. When the slump of concrete is too low (below 80mm), the pumping resistance increases significantly, making the pumping impossible.

The particle size of sand is unreasonable

When the content of fine sand passing through the 0.315mm sieve is small, the pipe will be blocked even if other technical indexes of the concrete meet the requirements. Because these fine sands play a ball like role in concrete, they can reduce the friction between pipe wall and concrete, improve the fluidity, increase the cohesion and water retention of concrete, and have a great impact on the pumpability of concrete. Therefore, JGJ / t10-95 technical specification for concrete pumping construction stipulates that the sand passing through the 0.315mm sieve shall not be less than 15%.