Due to the construction intensity requirements of bridges, sea square and so on, high-grade concrete construction is required. Due to the limited space and conditions of these projects, most of them are transported far away. The following to Qingdao two built in Court Court Plaza using HBT60A concrete pump pumping high-grade concrete, for example, to talk about how the level of concrete pumping high-level long-distance. Zhong Court Sea Square is used to stop the helicopter, its strength requirements are particularly high. At that time, C60 high grade concrete construction was adopted. The slump of concrete was 12-14cm, the horizontal conveying distance was 300m and the vertical distance was 10m. Four 90º × R1000 bends were used, and the amount of concrete for one pumping was 400m3. Pumping is the most difficult high-grade concrete, slump, viscosity, distance, high pumping pressure, resulting in low pumping efficiency or pumping out. Therefore, we must pay attention to the following aspects: (1) before pumping, the device should be fully checked. The main system pressure can be adjusted to 32MPa, mainly taking into account the pumping pressure is high, the main relief valve overflow problem. ② The main pump displacement regulation to a minimum, the sequence valve pressure can not be less than 10.5MPa, sufficient nitrogen in the accumulator. ③ slide valve cylinder seal can not have internal leakage, the cylinder buffer may be appropriate smaller, lubrication should be sufficient, smooth, otherwise it will be due to the concrete viscosity, resistance caused by sluggish or slow gate lift, resulting in leakage caused by Y Word tube or adjustable tube blocked. The gate wear gap can not be too large, otherwise it will also cause the same failure due to leakage of plasma. ⑤ Y-tube and the upper shell must be tight seal, otherwise it will lead to plugging due to leakage of slurry, to the construction of unnecessary losses. (2) on the tube requirements. ①long distance pumping resistance, pipe to minimize pipe bending, and should be used as far as possible instead of a small bend. Practice has proved that for each additional 90º × R1000 elbow, it is equivalent to an increase of 5m horizontal pipe. Therefore, when the pipe is used only four φ125A 90º × R1000 elbow, the rest are φ125A × 3m straight pipe and φ125A × 2m straight pipe, the total length of 310m. ② should pay attention to the reinforcement of pipe and pipe clamps. This long-distance pumping, there will be exacerbated pipe beats, pipe burst, pipe card explosion and so on. Therefore, we must be at the corner and some straight pipe in full reinforcement, slow down its impact. (3) before pumping concrete, water can not be too much, pump the right amount of water to lubricate the pipeline can be. Some operators may misunderstand that, due to the length of the pipe, sufficient water should be added to fully lubricate it. Pumping too much water during construction, resulting in some card stuck at the apron, water leakage. When playing mortar, the mortar and water contact interface for a long time soaked in water, the water to take away the grout, resulting in mortar segregation, pumping resistance increases, resulting in the slurry from the spoiler collapsed squeeze, resulting in blocking tube. (4) pumping, the concrete due to label high viscosity, resulting in pumping difficulties. C60 high-grade concrete, the coarse aggregate size below 30mm, grading reasonable; sand rate 39%, fine sand; and the amount of cement can meet the pumping requirements. However, the strength constraints, the water-cement ratio between O.2-0.3, resulting in slump of about 12cm, affecting the fluidity of concrete pumping, increasing the resistance. Increase the sand rate can improve its pumpability, but the impact of strength, less than the design and construction requirements. Therefore, the only way to solve this problem is the addition and subtraction of water, neither affect the strength, but also increase the slump. No superplasticizer was added when the pump was started, the pumping pressure was 26-28MPa, the pumping speed was slow and the effect was poor. If the pressure for a long time delivery, will affect the stability and reliability of concrete pumps. Later, a certain amount of superplasticizer (NF-2) was added, the slump reached 18-20m, the pumping pressure dropped obviously, only about 18MPa, which made the efficiency of pumping about doubled. In addition, the pumping process, should also remind the operator: the concrete hopper must be above the midline of the mixing shaft, otherwise it will lead to suction caused by concrete splashes around the wounding, or as a result of suction, gas compression caused by plugging. (5) after pumping, should promptly clean the pipeline. Pipeline cleaning should be disconnected from the middle, divided into two cleaning, in order to ensure safe and reliable. Note that when stuffing a sponge, add a cement bag, two sponge balls, and a cleaning piston in front of it.
