Since prefabricated exterior walls are assembled in pieces, we will inevitably encounter the problem of waterproofing the connecting joints. Therefore, we must attach great importance to processing waterproof nodes of prefabricated exterior walls. This article will analyze and introduce several existing prefabricated exterior wall panel waterproofing technologies, and also discuss some issues that need attention and attention in the waterproof construction of prefabricated exterior wall panels.
Design Concept Of Waterproofing Of Precast Concrete Buildings：
Precast concrete construction is to disassemble the building structure such as wall panels, columns, beams, floor slabs, stairs, etc. according to certain specifications, and then prefabricate them in the factory, and then transport them to the site for assembly. Since the components are assembled on-site, a large number of assembly joints will be left. These joints can easily become channels for water penetration. Therefore, precast concrete buildings have certain inherent weaknesses in waterproofing. In addition, to resist the influence of earthquake forces, the exterior wall panels of some precast concrete buildings are designed to be movable within a certain range. The movable wall panels further increase the difficulty of waterproofing the joints of the wall panels.
Given the above factors, the design concept of waterproofing of precast concrete buildings must be adjusted. We believe that for the waterproofing of prefabricated buildings, water conduction is better than water blocking, and drainage is better than waterproofing. Simply put, it is necessary to consider the possibility of certain problems during design. The water flow will break through the outer waterproof layer, and the water that breaks through will be guided to the drainage structure through a well-designed drainage path and then discharged to the outside to prevent it from further penetrating indoors.
In addition, using the principle that water flows naturally due to gravity, the wall panel joints are designed into a tongue-and-groove shape with a high inside and low outside, combined with a certain pressure-reducing cavity design to prevent water from crawling backward into the room through capillary action. In addition to concrete In addition to structural waterproofing measures, the use of rubber waterstops and multi-component weather-resistant waterproofing glue to complete the waterproofing system of the entire precast wall panel can truly ensure that there is no leakage.
Precast Concrete Exterior Wall Panel Joint Waterproofing Treatment
At present, the joint waterproofing forms of prefabricated exterior wall panels commonly used in practical applications include the following:
1. Prefabricated Exterior Wall Panels
(i.e. PCF panels) with internal pouring and external hanging mainly adopt the drainage cavity and glue on the outside and rely on the self-waterproofing of the joints of the cast-in-place concrete on the inside.
This form of exterior wall panel joint waterproofing is currently the most commonly used. Its advantage is that the construction is relatively simple and fast. The disadvantage is that the waterproofing quality is difficult to control, and cavities are often blocked. Once the inner concrete cracks, it will directly lead to The siding failing to waterproof.
2. The Closed Line Waterproof Form Used In External Precast Concrete Exterior Wall Panels
This type of wall panel waterproofing mainly has three waterproofing measures. The outermost part uses highly elastic weather-resistant waterproof silica gel, the middle part is a decompression space formed by the physical cavity, and the inner part uses waterproof rubber strips pre-embedded in the concrete to press each other up and down. To achieve a waterproofing effect, add a layer of polyurethane waterproofing in addition to the rubber water stop at the cross joint between the walls. Its main function is to use the good elasticity of polyurethane to block the slight differences that may occur when the rubber waterstops move against each other. For rooms or buildings with particularly high waterproofing requirements, polyurethane waterproofing can be fully constructed on the inside of the rubber water stop to enhance the reliability of waterproofing. A drainage pipe is installed on the waterproof silica gel of the exterior wall every 3 floors or so, which can effectively guide the rainwater that has penetrated the decompression space to the outdoors.
The waterproof structure of closed-line waterproofing adopts a method of combining internal and external waterproofing and blocking. Its waterproof structure is very complete, so the waterproofing effect is also very good. The disadvantage is that the accuracy during construction is very high, and the wall panel misalignment cannot be greater than 5mm, otherwise, the water-stop rubber strip cannot be pressed tightly. The weather-resistant and waterproof glue used has relatively high-performance requirements. It must not only have high elasticity and aging resistance but also have a service life of not less than 20 years. The cost is relatively high, and the quality requirements during the construction of structural glue are It is relatively high and must be operated by a professional and experienced construction team.
3. Open-line Waterproofing
This form of waterproofing is the same as closed-line waterproofing in that the two waterproofing measures on the inside are the tongue-and-groove decompression space and the pressure-tight waterproofing rubber strip on the inside. However, the waterproofing measures on the outside of the wall panel are open. Line waterproofing does not use glue. Instead, one end is embedded in the wall panel, and the other end extends outside the wall panel. Curtain-shaped rubber strips overlap each other up and down to play a waterproof role. At the same time, the outer rubber strips are spaced Stainless steel air guide grooves are set up at a certain distance to balance internal and external air pressure and drainage.
The outermost waterproofing of the open line waterproofing form uses pre-embedded rubber strips, making the product quality easier to control and inspect. Workers do not need to apply glue on the outside of the wall panels during construction, eliminating the need for construction measures such as scaffolding or hanging baskets, making it safer and more convenient. , the disadvantage is that it requires high product protection, it is difficult to replace the embedded rubber strip once it is damaged, and the cost of weather-resistant rubber water-stop strips is also relatively high. Open-line waterproofing is currently the most advanced form of exterior wall waterproofing joint treatment, but it is a patented technology developed by a foreign company. Due to the impact of patent usage fees, there are currently very few domestic projects using this technology.
Construction Points For Waterproofing Joints Of Prefabricated Exterior Wall Panels
At present, the waterproofing treatment technology of prefabricated exterior wall panel joints is relatively complex in terms of technology, so it is also relatively difficult to construct. During actual construction, we should make targeted formulations based on different exterior wall panel joint design requirements. construction plans and measures. Specifically, we should pay attention to the following construction points during construction:
1. Carry out product quality inspection before wall panel construction
The processing accuracy and concrete maintenance quality of prefabricated wall panels directly affect the installation accuracy and waterproofing of the wall panels. Before installing the wall panels, you must carefully review the geometric dimensions and flatness of the wall panels, and check the surface of the wall panels and the concrete around the embedded window frames. Whether it is dense and whether there are cracks, wall panels with unqualified concrete quality are strictly prohibited from use.
In addition, we also need to carefully check the installation quality of the embedded rubber strips around the wall panels, check whether the rubber strips are pre-embedded firmly, whether there is damage at the corners, and whether there is concrete slurry leaking into the rubber strips, causing the rubber strips to harden and lose elasticity. , the rubber strips must be strictly inspected to ensure that they are flawless. If there are quality problems, they must be replaced before lifting.
2. Strictly control the installation accuracy during wall panel construction and carefully measure and set out the wall panels before hoisting them.
Not only should the reference line be placed, but also the position lines of the wall panels should be laid out to facilitate the positioning of the wall panels during hoisting. The accuracy adjustment of wall panels is generally divided into two steps: coarse adjustment and fine adjustment. Coarse adjustment is to decouple the wall panels in place based on the control line. Fine adjustment requires adjusting the wall panel axis position and verticality deviation to within the allowable deviation range of the specification. In actual practice, It is generally required not to exceed 5mm during construction.
3. During the waterproofing construction of wall panel joints, strictly follow the process and conduct a quality inspection of each process.
Gluing on the outside of wall panel joints must be carried out in strict accordance with the design process, and the base layer and reserved cavity must be cleaned with high-pressure air. The depth of the backing should be carefully checked before gluing. The thickness of the gluing must meet the design requirements. The wall panels in the gluing area should be treated with primer to enhance the bonding force between the glue and the concrete wall panels. When gluing is interrupted, the construction should be left. The construction joints should be high on the inside and low on the outside, and the overlap should not be less than 5cm.
The connecting iron parts and cross joints on the inside of the wall panels are sealed with polyurethane. Since there are no rubber water stops on the iron parts, rust removal and rust prevention of the iron parts must be done carefully before applying polyurethane, and the polyurethane must be applied tightly. No gaps should be left. After the construction is completed, a water splash test must be conducted to ensure that there is no leakage before the cover can be sealed.
4. After the construction is completed, conduct a waterproofing effect test to properly and effectively deal with leakage problems promptly.
After the waterproof construction of the wall panels is completed, a water spray test should be carried out in time to check the effectiveness of the waterproofing. The focus of water spraying is the cross joints of the wall panels, the connection between the prefabricated wall panels and the cast-in-place structure, and the window frame. It is recommended to use a fire extinguisher when spraying water. Spray the test area with a water hose, check the outside to see if there is degumming in the glued area, and whether the drainage pipe drains smoothly, and carefully observe whether there are watermarks or water stains on the inside. If local leakage is found, records must be carefully recorded to find out the cause and dealt with promptly. If necessary, a layer of polyurethane waterproofing can be added to the inside of the wall panel to improve the safety factor against leakage.
Summarize
Precast concrete buildings are a new technology that is being vigorously promoted in the construction industry. From a technical perspective, the waterproof performance of exterior walls can be effectively guaranteed by taking a series of improvement measures. On-site construction personnel should be proficient in prefabricated exterior wall waterproofing construction. The key points are to operate strictly by the relevant standard procedures and to control the waterproofing quality. Only in this way can the waterproofing of prefabricated walls be ensured and prefabricated residential products can be recognized by the majority of users and the market.
