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The 88th floor of the main building of Hong Kong International Financial Center, 420m high, is the fifth largest in the world and the tallest building in Asia. The maximum height of concrete pumping is 408m, which has high requirements on construction safety, reliability, environmental protection and automation. All the main buildings of C60 concrete are used to ensure project quality and structural strength, which poses a severe challenge to concrete conveying equipment. To this end in the concrete recipe has also taken some measures conducive to pumping, and the mixing station built in the site, about 300m away from the concrete pump to ensure concrete in 20min to reach the pouring surface, reducing slump loss.
This project each layer of concrete dosage about 240m3, divided into two construction, using two Sany Heavy Industry HBT90CH-2122D high pressure concrete pump, while laying the same two sets of pipes , two pumps can be pumped at the same time. Pumping process in the 400m high concrete pump hydraulic system working pressure of 24 ~ 25MPa, concrete outlet pressure of 16MPa, 10 to 11 times per minute commutation, the delivery of about 40m3 / h.
2 equipment status
2.1HBT90CH concrete pump
2.1.1 Technical Features
1) double dynamic structure
In order to ensure the reliability of the construction process, the whole engine uses two diesel engines to drive two sets of pumps respectively. The application of dual power and power confluence technology, usually two sets of pump work at the same time, when a group of fault can cut off the group, the other group still maintain 50% of the displacement to continue to work, to avoid the construction process interruption caused loss.
2) Automatic high and low pressure switch
Hydraulic system high and low pressure pump mode switching process all controlled by the computer, just press the 1 button to complete the switch in an instant, without downtime, no pollution.
3) High-pressure concrete piston
Due to the maximum pumping height of 408m, the concrete inside the pipe has a great counter-pressure to the concrete piston. According to the characteristics of this key working condition, the high-pressure concrete piston adapted to the ultra-high-rise pumping structure was developed by using the reinforced polyurethane material.
4) glasses board, cutting ring
Hydraulic systems High and low pressure pump mirror plate thrust, resulting in seal failure, and the pair of coupling between the seal is to ensure ultra-high-level pumping the key. HBT90CH concrete pump to reduce the flow of S pipe to reduce the thrust, while using high preload technology to make the cutting ring and the lens plate close fit, to ensure reliable sealing.
5) washed
In the 408m super high-rise pumping concrete pump still in use in HBT90CH pumping high, how high the water and created the legendary world record of the highest waste water technology, concrete is minimized, the entire project can save concrete 2640m3, Equivalent to 1.9 million Hong Kong dollars. In addition, there is no residual concrete, which reduces the burden of sediment treatment and management and reduces the workload and cost of the construction process. ?
2.2 Auxiliary equipment
With the engineering requirements supporting the design of a cloth radius of 32.5m tailless drag automatic climbing cloth rod, the main parameters
Cloth radius (m) 32.5
Tower height (m) 31
Climbing automatically climbs
Climbing speed (m / s) 0.5
Total power (kW) 30
Machine quality (t) 24
Boom deceleration hydraulic motor unit 4 is driven to achieve automatic continuous climbing machine rack and pinion driven boom support frame and increase interaction, the whole process may be a person climbing operation is complete. Due to the restriction of the structure of the building, the maximum span of the supporting rod of the cloth rod is up to 10m and the minimum is only 3.5m. Sany Heavy Industry has specially designed a large-span luffing beam for this purpose.
2.3 duct
At the outlet of the pump, 100m horizontal tubes, 4 90 ° elbows, 1 45 ° elbow and 2 15 ° elbows were arranged. On the 32-storey 140m high, 30m horizontal tubes and 90 ° elbows were arranged. Two 90 ° elbows are arranged on the 45th floor of 200m high; two 90 ° elbows are arranged on the 55th floor of 240m high; then, the whole pipeline including the tower body of the cloth machine is exposed 10m and the arm length is 32m, 44m, length 622m. Straight pipe ends are rigid support firm fixed.
3 pumping construction technology key
There are many technical problems in the pumping construction of super high-rise building concrete structures. Measures should be taken in the following aspects.
3.1 equipment pumping capacity
The maximum pumping capacity of the equipment should have a certain reserve, to ensure smooth delivery, to avoid plugging. In this pumping height of 408m, the working pressure of the concrete pump hydraulic system is 24 ~ 25MPa, the concrete outlet pressure is 16MPa, while the working pressure of the hydraulic system of the HBT90CH super high pressure concrete pump can reach 35MPa and the maximum pressure of the concrete outlet can reach 22MPa , Which is also the key factor for HBT90CH successfully pumping 400m super high-rise pumping.
3.2 equipment configuration reliability
Equipment configuration should be based on reliability as the first principle, reasonable layout of super high-rise concrete transportation pipeline is crucial, once the equipment failure due to stop pumping more than 2h, concrete in the pipe will appear bleeding, segregation, the entire pipeline The system of concrete scrapped and seriously affect the construction quality. Trinity HBT90CH pump with two engines , can work simultaneously to improve work efficiency, but also a separate operation, even if there is a failure of the standby engine to continue to work, greatly improving the reliability of the construction process. In addition, two independent pumps and piping systems are also a strong guarantee of smooth construction.
3.3 ultra-high pressure resistant piping system
In the ultrahigh-pressure pump, the maximum pressure in the pipe can reach 22MPa, longitudinal will produce 27t pull, must be resistant to ultra-high pressure pipeline system. In addition, the conventional connection and sealing methods can not meet the requirements, the following solutions need to be taken.
1) The use of ultra-high pressure pipe wall thickness 9.5mm above, to protect the pipe blast resistance.
2) The connection between the pipes is guaranteed by the strength of the screw, the longitudinal tension is borne by the screw, so that the joint can be reliably guaranteed.
3) with high-pressure concrete skeleton seal ring to prevent the concrete under the high pressure of 22MPa squeeze out from the pipe clip gap to ensure long-term reliable seal.
4) The smaller the pipe diameter, the greater the transmission resistance, but too large duct explosion resistance is poor, and the concrete flow in the pipe slow, long residence time, affecting the performance of concrete, the best choice of diameter 125mm transport tube.
3.4 reasonable cloth tube
Piping should be based on the concrete pouring program to set and use less elbow and hose, pipe length as short as possible. The project pipeline laying along the floor or wall, the concrete floor or wall with expansion bolts to install a series of bearings, each pipe by two bearings fixed. In order to reduce the pipe concrete back pressure in the pump outlet layout of the horizontal pipe and a number of 100m elbow, and achieved good results.
3.5 reasonable mix of concrete
The principle of mix design is not only to meet the strength, durability requirements, but also economical and reasonable, with a good pumpability, so in addition to the usual factors to be considered must handle the following aspects.
1) the amount of cement
Suitable for pumping high-rise concrete cement content must take into account the strength and pumpability, less than the amount of cement with less than strength requirements, too large then the viscosity of concrete, pumping resistance increases the difficulty of pumping and increase, and reduce Inhalation efficiency. In this case, the amount of cement for the 375kg / m \ +3, in the construction has achieved good results.
2) coarse aggregate
Conventional pumping operation requires that the ratio of the maximum aggregate particle size to the pipe diameter is not greater than 1: 3; in ultra-high-rise pumping, the pipelines tend to segregate due to high pressure in the pipelines, and the ratio should be less than 1: 5, Less gravel, so as not to increase the amount of cement.
3) Slump
Ordinary pumping operation of concrete slump in about 160mm most conducive to pumping, high slump easily segregated, low mobility is poor. In the ultra-high-rise pumping to reduce pumping resistance, slump should be controlled at 180 ~ 200mm, at the same time to prevent the segregation of concrete can be incorporated zeolite powder to reduce bleeding.
4) fly ash and additives
The combined use of fly ash and additives can significantly reduce the amount of water and improve the workability of concrete mix. However, due to more varieties of admixtures, adaptability to fly ash are also different, the optimal dosage should be determined by testing.
3.6 to ensure continuous supply of concrete
In view of the characteristics of good viscosity and fast setting of concrete, in order to ensure the homogeneity of the concrete, the mixer rotates 20 ~ 30s in reverse direction before feeding to the pump, the pumping process should be continuously and continuously stirred to avoid Concrete in the pumping process to stay long caused by condensation blocking tube phenomenon.
3.7 to ensure the smooth pumping of concrete
Pressure feed before the application of water wet pump hopper, pump room, piping and other parts in contact with the concrete, check the pipeline without exception before the use of cement mortar lubrication pressure delivery.
Start the pump pumping should be in a low speed state, and observe the pressure of the pump portions of the work, only up to the normal transport speed pumped until smooth.
When the concrete pumping difficulties, the sudden increase in pump pressure will lead to pipe vibration, hit the pipe with a hammer to find the blockage of the pipe, using positive and negative pump jog handling or disassembly clean, after checking to confirm no blockage Continue pumping, so as not to damage the pump.
During the construction, the pipe withdrawal method from far to near and the second pipe laying method are adopted. The direction of the concrete pouring is the same as the pumping direction.
3.8 Other precautions
1) Do not use pipes that produce cracks and surface dents. The pipe clamps must be tight to prevent the pipes from being damaged.
2) timely fault handling and replacement of the necessary wearing parts;
3) Shutdown should be promptly cleaned and pay attention to the maintenance of the pump.
The use of commercial concrete pumping construction has been widely used in construction projects, but the height is greater than 300m high-rise pumping, because the pumping pressure is too high, the use of high strength concrete, high viscosity, particularly difficult to pump, with a pumping construction Come to a series of technical problems to be explored. With the popularization and rapid development of pumping concrete, continuous research on high-rise concrete pumping technology has considerable practical value and economic significance for improving the construction quality and construction efficiency of super high-rise buildings.