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Causes and treatment of water leakage in underground deformation joints
Causes and Treatment of Water Leakage in Underground Deformation Joints
A. Reason Analysis:
1. Before pouring the concrete, the waterstop strip in the deformation joint may not have been properly installed or fixed. As a result, after the concrete is poured, the position of the waterstop strip shifts, gets squeezed by the concrete, and may even become twisted, curled, or extruded outside the wall. This leads to an ineffective waterproofing function and inability to accommodate structural deformation.
2. Poor bonding at the joints of the waterstop strip can cause it to fall out or remain partially detached, preventing the formation of a complete waterproof ring. Additionally, since the waterstop is located in the middle of the deformation joint, it may be damaged by hard objects or improperly positioned connectors, further compromising its effectiveness.
3. In some cases, improper concrete mix ratios with high shrinkage coefficients lead to poor coverage of the waterstop wing. Especially at the bottom slab and corners, inadequate vibration during concrete placement can leave gaps, which become pathways for water leakage. Pressurized water can then seep through the gap between the two sides of the waterstop and the surrounding concrete.
4. Uneven foundation settlement can cause building deformation, pulling the waterstop beyond its elastic limit and resulting in leaks.
5. Some construction teams use simple methods like cement and water glass grouting, plug spirit filling, or polymer cement mortar to seal leaks. These approaches are rigid, lack flexibility, and cannot adapt to structural movement, often leading to recurring water seepage.
B. Preventive Measures:
To prevent water leakage, proper technical guidance must be provided for the installation and fixing of the waterstop strip during concrete pouring. The width control, joint filling, and sealing treatment should all be carefully managed. A dedicated person should supervise and inspect the implementation to ensure that the design specifications are fully followed during construction.
C. Repair Methods:
1. Manually clean the base surface within 400mm on both sides of the original deformation joint, removing any existing embedded materials such as cement grease or asphalt hemp.
2. Cut the base surfaces on both sides of the joint to a width of about 80–100mm.
3. Pre-embed a 5–10mm thick hemp into the lower part of the expansion joint near the rubber waterstop. Install a φ8@400–450mm aluminum grouting nozzle with quick-setting micro-expansion cement, then apply water-soluble grout for waterproofing.
4. Fill the groove with polymer cement mortar and flatten the base surfaces on both sides of the joint (note: the seam width should be 39mm, with a tolerance of -1mm).
5. Once the structure has gained sufficient strength, insert a 40mm-wide water-expandable rubber rod into the reserved joint (make sure to remove the original foam board during construction).
6. Place a 60×40mm polystyrene foam board as a cushion layer inside the deformation joint, pressing it tightly against the surface of the water-expanding rubber rod.
7. Apply a two-component polyurethane sealant to the joint with a thickness of 30mm.
8. Insert another 60×40mm polystyrene foam board as a secondary cushion layer, pressing it firmly against the polyurethane sealant.
9. Cover the sealed joint with a 2.0mm thick rubber-based waterproof membrane, with a width of 350mm (including the deformation joint), leaving appropriate expansion space. Seal the edges using 50mm wide single-sided isobutyl adhesive tape. Ensure the base surface is flat, compact, and free of dust.
10. Apply a 3mm thick rubber plate as a cushion layer for the waterproof membrane, using a floating method.
11. Install a 2mm thick stainless steel plate as a protective layer for the wall. The actual width should be 400mm, with a planar dimension of 300mm, pre-formed into a "U" shape and secured to the concrete using expansion screws.
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