1. Above-Ground Buildings
Above-ground buildings refer to structures situated above the natural ground level, exposed to long-term environmental factors such as sunlight, rain, and snow. These buildings require not only excellent waterproofing but also high durability. The exterior wall is the primary part of an above-ground building that interacts directly with the environment. Thanks to the superior waterproofing and durability of prefabricated components, the technology used to connect adjacent prefabricated elements has become a critical factor in ensuring building waterproofing.
1.1 External Wall Panels
External wall panels are commonly used in frame structures. Typically, these walls are designed as non-load-bearing or non-shear peripheral protection systems. When subjected to seismic or wind forces, the joints on three or four sides of the wall panel units open slightly, allowing elastic waterproof materials to absorb the movements caused by these forces. External wall panels can be classified into horizontal sliding, rotating, and fixed types, depending on their mode of movement under stress. Consequently, it is essential that the waterproof material at the joint remains crack-free, demanding high displacement capacity from the waterproofing materials.
Joints in external wall panels are primarily categorized as horizontal or vertical joints. They follow a waterproof design principle of “guiding as the main method and blocking as the auxiliary,” featuring two layers of waterproofing that combine material and structural waterproofing:
- For the exterior-facing parts, which endure prolonged exposure to natural elements like sunlight, the sealant used must exhibit excellent weather resistance. Additionally, it should not cause secondary pollution during extended use, preserving the building’s exterior appearance.
- On the interior side, where the environment is more stable, the waterproofing serves as the final barrier. The material here must have good flexibility and adhesion to prevent cracking and water leakage.
Figure 1 illustrates the waterproof structure of a horizontal joint. From outermost to innermost layers, these include weather-resistant sealant, a backer rod foam strip, a pier base, a waterproof rubber strip, and a final waterproof sealant. The weather-resistant sealant is typically made from materials such as polysulfide adhesive or modified silicone adhesive, known for their excellent weather resistance and environmentally friendly properties that do not harm building aesthetics. The pier base features a height difference to effectively prevent rainwater backflow. Meanwhile, the waterproof rubber strip and cross joint are reinforced with polyurethane or other waterproof sealants, forming a secondary waterproof layer that effectively blocks water infiltration.
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