Your Position: Home - Formwork - A Complete Guide to Casting Water Stop Nuts: Function, Installation, Applications, and Specifications
A casting water stop nut plays a vital role in reinforced concrete structures where waterproofing is crucial, especially in construction joints of basements, tunnels, retaining walls, and water tanks. The primary function of a water stop nut is to prevent water seepage along the tie rods used in formwork during concrete pouring.
When tie rods pass through the formwork to hold both sides in place, they create a potential leakage path through the concrete wall. The water stop nut acts as a barrier inside the wall, breaking the direct path of water penetration. It effectively stops water from traveling along the steel tie rod by forming a dense, water-resistant seal within the concrete.
Moreover, the casting water stop nut also provides strong anchoring and structural stability. It ensures the tie rods are fixed securely, maintaining the desired wall thickness and alignment during concrete casting. The combination of structural reinforcement and waterproofing function makes it an essential accessory in any formwork system exposed to water pressure or damp environments.
Proper installation of a casting water stop nut is critical to achieving both waterproofing and structural stability. The typical installation process involves the following steps:
Preparation of the Formwork System
Before pouring concrete, ensure that the formwork panels are properly aligned and the tie rods are correctly positioned according to design requirements.
Positioning the Casting Water Stop Nut
Install the casting water stop nut at the middle section of the tie rod, where it will be embedded in the concrete wall. The nut should sit flush with the inner formwork to ensure even distribution of concrete around it.
Fixing the Tie Rod and Spacer
Attach the tie rod to the nut securely, using a washer or spacer as needed. Make sure the assembly is tightly fastened to prevent any movement during concrete pouring.
Concrete Pouring
Carefully pour concrete around the tie rod assembly, ensuring that no air pockets form near the water stop nut. Proper vibration will help compact the concrete and improve waterproofing performance.
Formwork Removal and Tie Rod Cutting
After the concrete has set, remove the formwork and cut off the protruding sections of the tie rod at both ends. The casting water stop nut remains embedded within the concrete as a permanent waterproof barrier.
Sealing and Finishing
Apply sealant or waterproof mortar on the exposed tie rod ends to enhance water resistance and ensure a smooth wall surface.
Casting water stop nuts are widely used in water-retaining and underground concrete structures. Common applications include:
Basement walls and underground garages – preventing groundwater infiltration.
Tunnels and subways – maintaining dry environments in high-pressure conditions.
Water treatment plants and reservoirs – ensuring leak-proof performance.
Retaining walls and foundations – protecting against moisture and hydrostatic pressure.
Dams, canals, and aqueducts – providing long-term durability in constant contact with water.
In addition, casting water stop nuts are also used in commercial and residential construction projects where waterproofing and formwork stability are required. Their versatility, reliability, and ease of installation make them a preferred choice among civil engineers and contractors.
Selecting the appropriate casting water stop nut depends on several factors related to project design, environment, and material requirements. Here are some key considerations:
Material
Carbon steel and ductile iron nuts are suitable for standard applications.
Stainless steel water stop nuts are ideal for corrosive or high-humidity environments.
Thread Size and Compatibility
Ensure the nut’s thread size matches the tie rod dimensions and conforms to formwork system standards (e.g., M12, M14, M16, M20, etc.).
Wall Thickness
The nut’s position and length should align with the concrete wall thickness to ensure the water stop section is fully embedded.
Water Pressure Level
For projects subject to high water pressure (e.g., dams, tunnels), use heavy-duty water stop nuts with larger flange diameters or thicker water stop plates.
Surface Treatment
Choose between galvanized, blackened, or epoxy-coated finishes depending on corrosion resistance requirements.
Typical specifications of casting water stop nuts include the following parameters (values may vary by manufacturer):
| Specification | Thread Size (mm) | Material | Surface Treatment | Water Stop Plate Diameter (mm) | Weight (kg) |
|---|---|---|---|---|---|
| Type A | M12 | Carbon Steel | Zinc Plated | 40–50 | 0.20–0.25 |
| Type B | M14 | Ductile Iron | Hot-dip Galvanized | 50–60 | 0.30–0.35 |
| Type C | M16 | Carbon Steel | Black Oxide | 60–70 | 0.40–0.45 |
| Type D | M20 | Stainless Steel | Polished | 70–80 | 0.50–0.60 |
All casting water stop nuts are typically produced through precision casting, ensuring high dimensional accuracy, excellent mechanical strength, and consistent waterproofing performance.
The casting water stop nut is a small yet crucial component in concrete construction projects, offering both formwork stability and waterproof protection. Understanding its function, correct installation method, and key selection factors ensures long-term structural safety and durability.
When sourced from a reliable manufacturer, casting water stop nuts can significantly improve construction efficiency, reduce maintenance costs, and ensure reliable performance under demanding water pressure conditions — making them indispensable in modern civil engineering and infrastructure projects.
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