Shuttering, also known as formwork, plays a crucial role in any concrete construction. It provides temporary support to the wet concrete, allowing it to harden into the desired shape and structure. Ensuring proper shuttering is essential for maintaining the quality, strength, and durability of the structure. This blog will outline a comprehensive checklist for shuttering, helping engineers, contractors, and construction workers maintain high standards in their projects. We’ll also reference relevant Indian Standards (IS codes) to ensure that construction practices are in compliance with the latest regulations.
What is Shuttering?
Shuttering refers to the temporary molds made of materials such as wood, steel, or plastic, into which concrete is poured to form structural elements like columns, beams, and slabs. After the concrete sets, the shuttering is removed. Proper formwork ensures that the concrete takes the intended shape and supports the load without any defects.
Importance of Shuttering
- Structural Integrity: Well-constructed formwork supports the wet concrete, ensuring it holds the desired shape.
- Safety: Proper shuttering prevents collapses and accidents on-site.
- Surface Finish: Good shuttering ensures a smooth finish, reducing the need for plastering or surface correction.
Checklist for Shuttering
- Material Selection
- Wooden Formwork: Check for quality wood that is free of cracks and is treated with waterproofing agents.
- Steel Formwork: Ensure steel panels are clean, free from rust, and have smooth surfaces.
- Plastic or Composite Formwork: Ensure they are clean, undamaged, and capable of withstanding the pressure of wet concrete.
- IS Code Reference: Refer to IS 4990: 2011 for plywood shuttering material, ensuring its quality and durability.
- Inspection Before Installation
- Surface Cleanliness: The formwork should be free from dust, dirt, and oil to avoid any bonding issues with the concrete.
- Proper Alignment: Ensure all shuttering materials are aligned according to the drawing and design specifications.
- Waterproofing: Wooden formwork should be treated with a waterproofing agent to prevent water absorption, which can weaken the formwork and affect the concrete setting.
- IS Code Reference: Use IS 14687: 1999 for guidelines on high-quality steel formwork, ensuring better durability and performance.
- Safety Checks
- Bracing and Support: Ensure all supports, braces, and props are installed correctly to prevent any movement or collapse during the concrete pour.
- Tight Fitting: The joints between shuttering panels should be tight to prevent any leakage of cement slurry, which can weaken the concrete.
- Adequate Support: For beams, columns, and slabs, ensure that proper props and supports are in place to bear the load of wet concrete.
- IS Code Reference: Refer to IS 2750: 1964 for steel scaffolding guidelines, ensuring safety and stability during formwork installation.
- Level and Plumb Check
- Correct Leveling: Ensure that the formwork is set to the correct level, especially for floor slabs and beams.
- Plumb for Columns: For vertical elements like columns, check the plumb (vertical alignment) using a spirit level or plumb bob.
- Diagonal Bracing: For tall shuttering, use diagonal bracing to avoid buckling or tilting of the formwork during concrete pouring.
- Leakage Control
- Sealing Joints: Make sure joints between the formwork panels are properly sealed with tape or foam to prevent leakage of cement slurry.
- Check for Gaps: Inspect all formwork for any gaps or holes that could cause leakage. Fill them with suitable sealing materials before pouring concrete.
- Control Slurry Loss: Leakage of slurry can lead to a reduction in concrete strength, so it’s essential to address any leaks promptly.
- Release Agents Application
- Applying Release Agents: Before pouring concrete, apply a suitable release agent (oil or chemical) to the shuttering to make it easier to remove without damaging the concrete surface.
- Uniform Application: Ensure the release agent is applied uniformly to avoid any patchiness or defects in the surface finish of the concrete.
- Final Pre-Pour Inspection
- Strength of Support: Double-check all props, supports, and scaffolds for stability.
- Reinforcement Clearance: Ensure that the reinforcement bars have adequate clearance from the shuttering, as specified in the design.
- Re-check for Leakage: Do a final inspection to make sure there are no leaks in the shuttering.
- Post-Pouring Checks
- Formwork Removal Timing: Follow the correct schedule for removing formwork, as early removal can lead to collapse or surface damage. Generally, for slabs, the formwork should be removed after 14 days, while for columns and walls, it can be removed after 7 days.
- IS Code Reference: Refer to IS 456: 2000 for recommendations on concrete curing and formwork removal.
- Reusing Shuttering Materials
- Cleaning After Use: Clean all formwork materials thoroughly after use. For steel formwork, remove any rust and oil it before storing. For wooden formwork, check for damages and replace any cracked or deformed pieces.
- Storage: Store the shuttering material in a dry, secure area to avoid damage or decay.
- Reusability Check: Inspect shuttering materials for reuse in future projects, ensuring that they remain in good condition.
Common Errors to Avoid in Shuttering
- Weak Supports: Avoid using weak or inadequate supports, which can lead to formwork collapse.
- Poor Alignment: Misaligned shuttering can result in uneven or deformed concrete structures.
- Inadequate Sealing: Not sealing joints properly can lead to slurry leakage, reducing the concrete’s strength.
Conclusion🎯
Shuttering is a critical part of any construction project, as it directly impacts the shape, strength, and quality of concrete structures. Following a comprehensive checklist for shuttering will help ensure the successful execution of concrete work, leading to durable and safe buildings. By adhering to the relevant IS codes, such as IS 4990 for plywood shuttering and IS 14687 for steel formwork, you can ensure compliance with the highest standards in construction.