Technical treatment methods for aluminum veneer in wall dry hanging construction

Aluminum veneer is the second generation product in metal curtain walls. Aluminum veneer is made of high-quality aluminum veneer as the substrate, and advanced CNC bending technology is used to form it, ensuring that the board can be flat and not deformed after processing. During installation, it has excellent resistance to external forces. The surface coating is made of fluorocarbon spray coating, ensuring uniform surface color, UV radiation resistance, oxidation resistance, and super strong corrosion resistance, Decorate the building into the luxurious or noble elegance that the designer wants to express.

So far, aluminum veneer curtain wall decoration has only been applied in high-end office buildings and iconic buildings in large and medium-sized cities. However, due to its high cost, it has not been widely used yet. With the rapid development of China's economy, aluminum veneer curtain wall decoration will inevitably be widely used.

Based on my practical experience in the construction of dry hanging aluminum veneers on the walls of the KTV decoration project in Shenmu Zunrong Lefu, I have summarized the problems that occurred during the construction process, such as the framework being not vertical and the board surface not matching; The sealant at the joints is not dense and has varying widths; The technical quality reasons for the loose connection of the closure and the lack of meticulous installation are discussed, and how to generate these three technical quality reasons and how to deal with them are discussed.

1、 Skeleton not perpendicular, board surface not matching

（1） Causes during construction

1. Before construction, there was no joint review of drawings and investigation of the actual construction site situation, and workers were not properly trained and provided with technical disclosure.

2. Before the installation of the skeleton, the actual size of the wall was not measured and the wall layout was not carried out, resulting in inconsistent distance between the skeleton arrangements. During the installation of the skeleton, the flatness and verticality of the skeleton were not measured.

3. The lack of positioning during the drilling of the skeleton resulted in mismatched positions of the holes, bolts, and pins connecting the skeleton to the aluminum veneer.

（2） Quality control points and prevention measures

1. Before the start of the entire project, the project manager must organize all engineering and technical personnel, as well as the leaders of the construction team, to carefully study the design drawings and strengthen their understanding of the drawings. Any technical issues found in the drawings should be communicated between the technical leader and the design institute to avoid quality issues during construction. Construction workers should first carefully carry out technical and safety disclosures, which must provide a detailed description of how each process is carried out. For important processes, parts, or links, appropriate training should be provided to workers to improve their technical quality. During construction, the method of layer by layer disclosure should be implemented to control the entire process.

2. Before the installation of the skeleton, due to the large error in the civil wall, the actual size of the wall should be measured based on the actual situation on site. The layout should be symmetrically arranged from the middle to both sides according to the actual size. After confirming the layout with the Party A and the supervisor, the wall positioning axis and horizontal line should be marked. Then, the spacing of the keel should be arranged according to the design requirements, and the keel grid line should be marked on the elevation horizontal line. Based on the suspension line, first determine the positions of the leftmost, rightmost, and middle three embedded parts, and then pull a horizontal line to determine the position of each embedded part on the horizontal line. After determining the position of the embedded parts, draw the bolt hole position of the embedded steel plate in a prominent color at the embedding location, and then use an electric drill to drill holes. After the anchor hole is formed, the construction process of chemical bolts should be strictly followed. Firstly, the slag and dust inside the hole should be blown out with a blowing cylinder, and then a special brush should be used to clean the hole. Then, the dust should be blown out with a blowing cylinder, and a medicine bag should be inserted. Special tools should be used to drive the bolts in. Wait for the chemical bolt agent to solidify before applying the steel plate. After installation, the elevation deviation should not exceed 10mm, and the left and right deviation of the buried position should not exceed 20mm. Strictly control the cutting size of column and horizontal materials based on on-site setting out data. Before cutting, the raw materials should be adjusted. For the finished product, the deviation of the column should not exceed ± 1mm, and the deviation of the horizontal materials should not exceed ± 0.5mm; The cutting end should not be deformed during processing to avoid burrs.

3. According to the setting out, determine the benchmark position of the column installation. First, connect the connecting parts to the column, then connect the connecting parts to the main embedded parts, and repeatedly adjust the spot welding and fixation. The installation position of the column should be accurate, and the deviation of the column installation elevation should not exceed 3mm. The deviation of the axis before and after should not exceed 2mm, and the deviation of the left and right should not exceed 3mm. The installation elevation deviation of two adjacent columns shall not exceed 3mm, and the distance deviation of two adjacent columns shall not exceed 2mm. The installation of horizontal materials on the same layer should be carried out from bottom to top. When a layer of height is installed, it should be inspected, adjusted, corrected, and fixed to meet the design and quality requirements. The horizontal elevation deviation of the installation of horizontal materials should not exceed 1mm, and the elevation deviation of the same layer should not exceed 5mm. A 1.5mm expansion joint should be left at both ends of the crossbeam and the fixed position of the upright column. After fixing, it should be sealed with sealant. After the installation of columns and beams, the diagonal deviation of each grid frame should meet the requirements of the specifications. When the diagonal is less than or equal to 2mm, the diagonal difference should be less than or equal to 3mm; When the diagonal is greater than 2mm, the diagonal difference is less than or equal to 3.5mm.

4. When installing aluminum veneers, concealed acceptance must be carried out on pipes, conduits, insulation and sound insulation, and other equipment inside the wall. All processes must pass the acceptance before proceeding. It is necessary to first recheck whether the snap line division is accurate and whether there are accumulated errors. Check whether the specifications and dimensions of the aluminum single plate meet the design requirements, whether the color of the aluminum single plate is uniform and consistent, and whether the surface is flat, clean, and free of cracks and defects. If there are any problems, they should be adjusted or replaced in a timely manner. If there are no problems, they must be in place according to the plate number position and the original snap line position on the plate distribution diagram. Use rivets to fix the aluminum single plate on the vertical keel, First, install from the bottom of the wall to the top, with a gap of 15mm between the aluminum veneer and the aluminum veneer. Then, install the door opening and joint, and perform closing treatment. The board surface is required to be flat, with neat seams and consistent dimensions.

2、 The sealant at the joint is not dense and has varying widths

（1） Causes during construction

1. When applying sealant, ordinary sealant was used instead of silicone sealant.

2. Insufficient cleaning of gaps between panels (especially bonding surfaces) during caulking and drying. The filling depth of polyethylene foam is inconsistent. When filling silicone sealant with caulking gun, a certain pressure cannot be formed, resulting in poor bonding and sealing with the plate seam.

3. The operation of caulking is unskilled, and the distance between the caulking gun and the seam filling (polyethylene foam filling surface) is not consistent, the force is uniform, the compression is slow and the action is continuous, resulting in more and less caulking sealant, more joints, and air entrainment, resulting in the uneven surface of the joint sealant, and the phenomenon of bubble seepage.

（2） Quality control points and prevention measures

1. Choose silicone sealant with reliable quality. Silicone sealant is always soft and has a texture similar to rubber. Ordinary sealant and sealant will harden after air drying, and will break over time.

2. Polyethylene foam must be tightly plugged when filling. It should be rolled into a strip slightly thicker than the seam width according to the seam width, and then carefully plugged in. It should be noted that the distance between the filling surface and the board surface should be consistent, and no entry or exit is allowed. Only when the depth of the sealant joint is consistent and there is a blockage behind it, can the joint be dense and the joint surface be straight.

3. When applying glue, it should be noted that the temperature is above 15 ℃, below 30 ℃, and the relative humidity is above 50%. When operating the caulking gun, proper parameters such as the force of pulling, the speed of running, and the distance between the muzzle and the polyethylene foam filling surface should be tested at the inconspicuous joints first. After obtaining mature experience, the caulking gun should be driven in a straight line, from top to bottom, from left to right. Individual uneven joints such as butt joints should be immediately leveled with a pointing trowel. Pay attention to the operating techniques and do not allow air to enter. Air should be discharged during the caulking operation to prevent the generation of bubbles. Once bubbles occur, they should be punctured with iron wire and immediately pressed out with a pointing trowel in one direction until the sealing is smooth.

3、 The closure connection is not firm and the installation is not meticulous

（1） Causes during construction

1. Before installation, the design drawings were not studied and the node structure was not understood. There were unreasonable aspects in the design of the drawings, and they were not discussed with the design unit. They were handled independently to ensure that the connection was firm and adjust its flatness and straightness.

2. During installation, the material was not carefully cut and drilled, the node structure and connecting parts did not meet the requirements on the drawings, the closing was not laid out beforehand, and the installation was not meticulous, resulting in errors in the installation of various components.

（2） Quality control points and prevention measures

1. Before installation, carefully study the design drawings to understand the specific structure of the nodes. If there are indeed unreasonable aspects in the design of the local node structure of the skeleton, and there are improvement methods, the improvement methods should be submitted in writing to the supervising unit. After discussion between the construction unit, supervising unit, and design unit, changes can only be made with the consent of the design unit.

2. During installation, each connecting rod must be carefully cut and drilled. At the reserved openings, vents, and other locations of the skeleton, keels and connectors should be set up according to the corresponding node structure on the drawing, so that the structure meets the requirements on the drawing and ensures the rigidity of the skeleton. Before the closure of complex parts, a layout trial assembly should be carried out to ensure that all components can cooperate with each other without errors.

3. Develop a special construction technology plan at the construction node to ensure the correct installation method, ensure that the connections are firm, smooth, and sealed, and minimize errors in various installation processes.

4、 Board surface pollution, inadequate protection of finished products

（1） Causes during construction

1. After the installation of the aluminum veneer, there was no dedicated person responsible for product protection, resulting in heavy objects colliding with the aluminum veneer in the next process, resulting in uneven or defective surface of the aluminum veneer.

2. The aluminum veneer protective paper was removed too early and not properly protected, resulting in contamination during other unfinished construction processes.

（2） Quality control points and prevention measures

1. After the installation of the aluminum veneer, a dedicated person is assigned to be responsible for the protection of the finished product and dedicated settings are set up for protection. If any protective facilities are found to be damaged, they should be promptly restored. The handover of the process should be fully in written form and signed by both parties for approval. The operators of the next process should conduct product protection disclosure. If the finished product is contaminated, damaged or lost, they should be directly responsible, and the product protector should be responsible for supervising and inspecting the protection of the finished product.

2. The protective surface paper of aluminum veneer should be placed near the completion acceptance of the project or after the relevant processes in the vicinity have been completed before being removed. After removing the face paper, other materials should be avoided from colliding with the aluminum veneer during transportation.

3. Aluminum veneers and other materials should be strictly managed during transportation, entry, storage, and use to ensure that they do not deform, become damp, or rust. When transferring other materials from door and window openings to objects, attention should also be paid not to collide with aluminum veneer walls.

4. Once the aluminum veneer surface is contaminated, it should be promptly wiped clean with clean cotton sand (without sand particles).

5、 Conclusion

Aluminum veneer is not widely used at present due to its high cost. However, with the rapid development of China's economy, aluminum veneer curtain wall decoration will inevitably be widely used. Aluminum veneers are generally installed using a skeleton. Before installation, carefully study the design drawings to understand the specific structure. During installation, each connecting rod must be carefully cut and drilled to ensure that all components can cooperate with each other without errors. At the same time, appropriate installation methods should be developed, especially considering measures that are convenient for adjusting various installation errors. During the construction process, attention should be paid to: 1. The skeleton is not vertical and the board surface does not match; 2. The sealant at the joint is not dense and has varying widths; 3. The closure connection is not firm and the installation is not meticulous; 4. Pay attention to the protection of finished products, and only after handover can the plastic protective film be removed to prevent surface pollution and dents caused by impact.