Talking about the application of concrete pump in construction

Abstract: As the pace of urbanization continues to accelerate, urban traffic is particularly important for urban development. In urban traffic construction, bridge construction is one of the main measures to relieve traffic pressure. Generally, the length of the bridge is more than 200 meters. Therefore, the continuous conveying of concrete and the vertical and horizontal conveying speed play a decisive role in the construction quality and project schedule of the bridge.

Keywords: transfer pump concrete blockage measures

Text: In today's society, whether it is any country or any city, it is often judged by the number of high-rise buildings and the height of super high-rise buildings in the city. This is not absolute, but it can be said that the height of the building reflects its technological level. Especially in China, this phenomenon is even more prominent. Now the highest building in our country has reached more than 500 meters. However, as the main component of the building, how can concrete be sent to such a high place? ? Undoubtedly, the concrete pump is the best answer. The concrete pump, like the concrete mixer truck, is another type of special machinery for conveying concrete. They are powered by a pump and continuously transport concrete along the pipeline, which can complete horizontal and vertical transportation at one time and transport the concrete directly to the pouring site. There are few intermediate links and high production efficiency, especially for the construction of narrow construction sites, small pouring working surfaces, or densely reinforced buildings, which is an effective and economical conveying machine. Because the pumping concrete operation has the advantages of high degree of mechanization, good mobility, large conveying capacity, less manpower, low labor intensity of workers, simple construction organization, fast project progress, low cost, and high quality of concrete. Therefore, people measure the level of mechanization of concrete construction through the degree of use of concrete mixing plants, concrete mixing trucks and concrete pumps or pump trucks.

In recent years, concrete pumps have been widely used in construction. However, concrete pumps have a series of technical requirements during construction. If they are not handled properly, it will be counterproductive. What should we pay attention to in construction and what are the technical requirements?

1. The pipeline laying requirements of the concrete pump.

The pipeline layout should be laid according to the shortest distance and the least elbow; ensure that the connection is firm and stable, and fixed points are added at the elbow; all pipe clamps must be in place. Ensure that the joints are tightly sealed; in summer, when the pipeline is exposed to strong sunlight, the pipeline should be covered with wet grass bags for protection; in winter, when the temperature is 15°C, attention should be paid to cover and heat preservation; the transportation pipe directly connected to the pump outlet cone must be fixed so that it is easy to disassemble and assemble while the pumping stops for pipe cleaned. The vertical upward structure pipeline arrangement such as pouring columns and risers shall be provided with support points for each vertical upward pipe. As the height of the vertical pipeline increases, the conveyed concrete tends to flow back. A certain length of horizontal pipeline should be laid on the pump and the vertical pipeline to ensure that there is sufficient resistance to prevent the concrete from flowing back. The length of horizontal pipelines should generally not be less than 15% of the length of vertical pipelines.

2. Requirements for concrete

(1) Cement

The role of cement in the pumping process：

The pumping pressure of concrete is transmitted by the liquid phase substance in it. The liquid phase material and the solid phase material move together to complete the pumping process. The role of cement has two aspects: one is cementation, which enables the concrete to maintain a state where the solid phase material is surrounded by the liquid phase material during pumping; the other is lubrication, so the amount of cement should be appropriate. If the amount of cement is insufficient, the pumping volumetric efficiency will be reduced, and the transportation resistance will increase significantly, and the water retention of this kind of concrete is very poor, prone to bleeding, segregation and clogging; if the amount of cement is too large, the concrete will become too viscous and the transportation resistance will increase largely, but the pumping volumetric efficiency does not change much. Compared with gravel aggregates with the same particle size and gradation of pebble aggregates, gravel concrete uses a larger amount of cement.

(2) Aggregate

Among them, aggregates are divided into fine aggregates and coarse aggregates; fine aggregates can be divided into river sand, sea sand, mountain sand, and artificially broken sand according to their source. According to the average particle size, fine aggregates can be divided into three types: coarse sand, medium sand and fine sand. Concrete prepared with medium sand has the best pumpability, with an average particle size of 0.25-0.3 mm. If the average particle size is too small (that is, too much fine sand) the performance will also be not good, because it will increase the water consumption of concrete and cement consumption. Coarse aggregate pumping concrete can be made of pebbles, crushed stones or mixed aggregates of pebbles and crushed stones. For the maximum particle size of coarse aggregate, please refer to the table below. The maximum particle size of the coarse aggregate for pumping concrete is limited by the minimum diameter of the conveying pipeline. It is required that the maximum particle size of pebbles does not exceed 1/3 of the caliber; the gravel does not exceed 1/4 of the caliber. A small amount of super-diameter aggregates are allowed to be mixed. For example, in a 100mm diameter conveying pipe, a small amount of aggregates with a particle size of 50mm can be passed, but the proportion of such super-diameter aggregates must not exceed 1%, and they must be dispersed.