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Aluminum formwork construction methods and advantages and disadvantages

Posted by: Zhouhanping 2021-10-28 Comments Off on Aluminum formwork construction methods and advantages and disadvantages

Aluminum template is called aluminum alloy template for construction. It is a new generation formwork system following the wooden formwork and steel formwork. The aluminum template is designed according to the modulus, extruded by special equipment, and can be freely combined according to different structural sizes. The emergence and improvement of aluminum alloy formwork technology is the choice of market economy. Compared with other forms of formwork, it contains high technological components and is relatively cost-effective.

Aluminum formwork construction methods and advantages and disadvantages

Aluminum formwork construction method

The aluminum formwork construction process is divided into multiple steps, and the fine operation of each step is related to the final project quality. According to the characteristics of the block B project of Yuhu New City in Putian, Fujian Vanke, the shear walls, beams, columns, floor formwork and support system of B13, 15, 16, and 17 standard floors of this project adopt aluminum alloy formwork construction technology. The following is an analysis of several key steps in combination with the specific construction situation of the aluminum alloy formwork.

1.1 Template selection

According to the structural characteristics of this project and the actual situation on site, the template selection for each part is as follows:

1.2 Measuring and setting out

  • (1) Measuring and setting of shear wall control line. It is required to eject the shear wall control line on the concrete floor 300mm outward from the shear wall position line to facilitate the correction and review of the shear wall formwork position after the formwork is installed.
  • (2) Measurement and setting of 1000mm elevation line and plate thickness control line. There are two specific requirements for this operation: ① After the lower concrete is poured, the 1m elevation line must be marked on the shear wall reinforcement in time, and the elevation point must be given for each shear wall corner reinforcement. This is conducive to the accurate marking of the 1000mm elevation line. ②The thickness control line needs to be marked on the steel bars according to the floor elevation, and three or more floor elevation points are required to be measured on each side of the shear wall. This step is the key to the thickness control line measurement and setting.

1.3 Wall thickness positioning reinforcement installation

After the concrete pouring of the floor is completed, the installation of the wall thickness positioning steel bars will also begin. First, we need to weld the wall thickness positioning steel bars. The welding point of the welding wall thickness positioning steel bars is on the wall vertical steel bars 50-100mm from the floor surface, and the horizontal spacing of the positioning steel bars is 800mm. The length of the positioning steel bar is determined according to the wall thickness, and its welding position is determined according to the pop-up wall line. The deviation between the steel bar and the wall line control line should be less than 3mm to ensure the accuracy of the wall thickness and position of the lower part of the shear wall when the formwork is installed.

1.4 template design

  • (1) Shear wall template. When both ends of the shear wall are L-shaped, in order to make the formwork easy to be removed after pouring, the inner wall is equipped with easy-to-remove formwork. When the wall and elevator shaft are equipped with formwork, the upper horizontal formwork is 50mm higher than the floor to prevent the external wall formwork from overflowing when the floor concrete is poured.
  • (2) Column template. The column formwork adopts all-aluminum alloy formwork. The two outer ends of the column are clamped with the back corrugated by the buckling bolts as the column hoops. The back corrugation and the buckling bolts are alternately arranged as a column hoops. The column hoops are about 300mm away from the bottom. The distance between the hoops is about 600mm.
  • (3) Beam formwork. The beam bottom and beam side formwork adopts all-aluminum alloy formwork. The beam side formwork and the beam bottom formwork are connected by aluminum male corner formwork, the main and secondary beam side forms are connected by aluminum female corner formwork, and the beam side formwork and the floor formwork are connected by aluminum female corner formwork. connect.
  • (4) Floor template. The bottom of the floor slab is made of all-aluminum alloy formwork, equipped with an early disassembly support system to improve the turnover efficiency of the formwork, and independent steel supports are used, and the support spacing is 1300mm×1300mm.

1.5 beam support system

Independent steel support for this system. The retractable and fine-tuned single support roof is an early dismantling support system with obvious technical and economic effects. It has been applied to the corners of construction projects, and plays an important role in the vertical support of the horizontal structure of the building, bearing the weight of the beam and slab structure and the construction load, as well as diagonal bracing and horizontal bracing.

The floor height of this project is 2.9m, and it is directly supported by 2000-3500 single roofs, as shown in the following figure:

The main features of this support system are as follows:

  • (1) This system is a support system that can realize early dismantling in a true sense. When the concrete reaches the strength of demoulding, except for the single roof and the early demolishing head, the rest can be demolished, which not only ensures the continuous construction of the superstructure but also speeds up the turnover of the formwork, which can greatly save the amount of formwork input at a time and reduce the amount of formwork configuration. /3——1/2.
  • (2) The application range is wide, and the support rods are not restricted by the fixed plane size. Therefore, they can be used freely for irregular building planes. The spacing of the support rods and the spacing of the vertical and horizontal beams can be adjusted in time according to the load of the beams and plates. The buckle is easy to use.
  • (3) Under the condition of the same mold support area, the amount of steel consumed by this system is only equivalent to 30% of the amount of steel used in the bowl buckle. In this way, on the one hand, the vertical transportation of materials can be reduced, and on the other hand, the speed of the mold support is also increased. Has increased. Take the tower house as an example, it only takes half a day for each floor of 600-800m2 mold area, which is one-half to one-third of the time of other supporting systems.
  • (4) After removing the aluminum alloy formwork and the steel support, they can be unified on the unloading platform and transported by means of a tower crane. Of course, it can also be transported manually, which is more flexible.

Advantages and disadvantages of aluminum formwork construction

In engineering construction, aluminum formwork has gradually been widely used. At present, the proportion of wood formwork in the construction formwork project is still relatively large. But in order to save wood and respond to the requirements of energy saving and environmental protection, people began to try to use various metal templates, such as all-steel or all-aluminum. Practice has proved that the use of all-steel formwork greatly reduces the loss of wood, and at the same time greatly shortens the construction period, but it also brings challenges to the construction. Compared with wooden formwork, it is self-heavy, so it relies on vertical transportation and is inconvenient to operate. The use of aluminum alloy formwork solves this problem well. It is much lighter than all-steel formwork, so after it was introduced, it was quickly promoted and gradually improved. At present, a complete set of all-aluminum alloy formwork construction technology has been formed.

2.1 Technically

(1) Advantages:

First of all, aluminum is a low-density metal with relatively light weight, but its bearing capacity is quite good, and it is especially suitable for mechanized operations; the same type of components can be mixed with standard boards, so the assembly limit is small. The speed is fast, the template is finalized and modularized. The template can be combined and assembled between the left and right, up and down, and vertical and horizontal. The template has good versatility and interchangeability, and can be used in large-scale formwork projects of various building plane shapes; several Different formwork is directly connected by pins, which is easy to install and does not require a lot of effort when disassembling; if the horizontal member formwork adopts the “early dismantling” design, it can be dismantled after only 36 hours; concrete After the strength reaches the design strength, the aluminum alloy formwork can be completely removed. At this time, it can be seen that the surface quality of the concrete is very good; in order to ensure the safety of construction, there will be a movable multi-level operation during the installation of the aluminum alloy formwork. Platform, which can reduce security risks. In general, the aluminum alloy formwork is light in weight, convenient in construction, and reliable in quality.

(2) Disadvantages:

Compared with other forms, aluminum alloy formwork has higher requirements for construction level. There are four main requirements for the installation quality of aluminum alloy formwork:

  • ① Formwork axis positioning, external dimensions, and horizontal elevation must be accurate.
  • ② The surface of the board should be flat and clean, with tight seams and no leakage.
  • ③The installation should be firm and stable to ensure that it does not shift or expand during the construction process.
  • ④The deviation of template installation should be controlled within the allowable range of the specification.

Five points need to be paid attention to in the process of using the template:

  • ①The pre-made templates such as wall, column large template, beam side, beam bottom template, etc., should be numbered management, and the templates should be sorted and stacked for easy use.
  • ②When installing and dismantling the template, it should be lifted and handled gently, and no collision is allowed. Do not knock the template hard to avoid deformation of the template.
  • ③The removed template should be cleaned up in time. If warping or deformation is found, it should be repaired in time, and the damaged board surface should be repaired in time.
  • ④The template to be assembled should have a relatively flat and compact storage space. If it is laid flat, it is best to use a wooden square cushion frame. If it is placed in a vertical position, it is best to set up some sorting template frames, and when they hit the bottom, they will be padded with wood to ensure that the mold will not be deformed to the greatest extent. These pre-assembled templates cannot be piled up randomly, and other scattered materials cannot be placed on them.
  • ⑤In the place where it has been installed, it is not allowed to collide with other templates during the construction process, nor can it be used as a temporary lean to prevent deformation of the template or vertical deviation. The plane template that has been installed on the working surface cannot be used as a temporary stacker and work platform to ensure the stability of the support and prevent the elevation and leveling of the plane template from deviation.

In addition, there are many requirements for demolition. Once the technology is not in place, common quality problems such as pockmarked surfaces, honeycombs, and missing edges and corners on the concrete surface will appear.

2.2 Economically

  • (1) Advantages: First of all, compared with wooden templates, aluminum alloy template is not easy to deform, so it can be used more frequently. Taking this project as an example, the combined all-aluminum alloy template used in the shear wall template can be used for more than 200-250 times. The amortization cost of the template each time is small, and the economic benefits are obvious. Practice has proved that all aluminum alloy formwork can be used more frequently than steel formwork, and this advantage is even more obvious in high-rise buildings. According to calculations, as long as the aluminum alloy template reaches more than 50 times, the amortization cost of the wooden template is almost the same. Secondly, the use of aluminum alloy formwork can accelerate the construction speed and shorten the construction period. At the same time, it can also reduce unnecessary large-scale equipment rent during the construction process, which is more convenient and quick. Thirdly, the construction of qualified and high-quality aluminum alloy formwork can make the structural surface show the effect of clear water concrete, which saves the plastering required during decoration and the material and labor costs required for leveling. Therefore, from the perspective of the entire construction process, the use of aluminum alloy formwork can reduce engineering costs. On the one hand, it saves the consumption of cement, sand and other raw materials, and on the other hand, it saves the labor costs required for plastering.
  • (2) Disadvantages: The cost of adding aluminum alloy templates is relatively high. Although its amortization cost is relatively low, it is also diluted due to its high turnover. Compared with wooden formwork, the initial investment of aluminum alloy formwork for construction will be very large. After comprehensive comparison and analysis, this project decided to use aluminum alloy formwork, which not only reduces the comprehensive amortization cost of formwork, but also improves the surface quality of concrete and reduces the cost of plastering. It is also very beneficial to saving wood, energy saving and environmental protection.

In short, aluminum alloy formwork has experienced more than 50 years of application practice abroad, and a set of construction technology has been formed up to now. In addition to the strict implementation of the specification requirements, the construction of this project using aluminum alloy formwork has also formulated a series of management measures for the construction of aluminum alloy formwork, including safety, quality, and finished product protection measures.

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