Concrete Formwork Checklist during Concreting and Striking

What is Concrete Formwork?

Concrete formwork is a temporary supporting structure used to contain and shape wet concrete until it has hardened. It is an essential component of any construction project, allowing concrete to be poured, spread and formed into a desired shape and size. The formwork must be strong and durable, and designed to withstand the weight of wet concrete and the forces of the environment. It must also be leak-proof to prevent water from seeping through, and properly aligned to ensure the concrete is poured and spread evenly.

Checklist for Concrete Formwork: Concrete formwork checklists are necessary to ensure that the formwork is safe, of good quality and properly stored. Checks should be carried out before, during and after the concrete is poured. Before concreting, checks should include checking the formwork for proper alignment, leak-proofing, and strength. During concreting, checks should include monitoring the concrete pour, ensuring the formwork is properly secured, and monitoring the curing process. After removal of formwork, checks should include inspection of the concrete surface, checking for any damage to the formwork, and ensuring proper storage of the formwork.

Concrete Formwork Checklist at Site

Formwork Checklist for Walls:

Lateral Bracings: Ensure lateral bracings provided firmly supports the forms at all points of support. Block out (stop end) braced to resist vertical and lateral loads. Form panels are adequately braced and tied with each other.

Formwork Corners: Formwork corners shall be adequately tied to prevent leakage or bulging and spreading of concrete. Ensure sufficient length is provided for wall ties and has sufficient strength and spacing as required.

Wales: Check wales for proper proper spacing and joints between should be staggered from one tier to the next. In double member wales, one member left continuous across the location of form ties. Wall ties and bolts tightened properly. In case double member wales is used, both wales should have identical depths.

Joints and Laps: Check for adequate lap between forms and previously cast concrete. Ensure that grout leakage does not occur at joints between panels and joints between old concrete and panels above them.

Uplift Resistance: Ensure the provision of resistance against uplift in case of sloping faces of concrete formwork.

Supervision: Ensure experienced supervisor is available at site while installing the wall forms and while placing concrete.

Formwork Checklist During Concreting

1. Ensuring Proper Access for Workers: Before commencing concreting, it is important to ensure proper access for the workers involved in placing, compacting and finishing the concrete. This will help ensure the safety of all personnel on the construction site.
2. Maintaining Alignment and Level: It is important to maintain alignment, camber, level, and plumb (verticality) while concreting is in progress. This will ensure that the effective depth between the top and bottom reinforcement is not disturbed.
3. Maintaining Concrete Cover Around Reinforcement: It is important to maintain the cover of concrete around reinforcement steel as specified. This will help ensure that the reinforcement is adequately protected from any potential damage.
4. Preventing Grout Loss: Grout loss can occur due to movement at joints and it is important to take corrective action against it. This will help ensure that the formwork is strong and stable.
5. Cleaning Spilt Concrete and/or Grout: It is important to clean any spilt concrete and/or grout immediately. This will help maintain a clean and safe working environment.
6. Removing Wooden Spreaders: After placing concrete, all wooden spreaders that were used to hold the vertical form faces apart must be removed. This will help ensure that the formwork is stable and secure.
7. Easing Wooden Members for Creating Pockets: It is important to ease the wooden members used to create pockets before the concrete sets fully. This will help ensure that the formwork holds its shape and is not damaged.
8. Maintaining Concreting Sequence: It is important to maintain the concrete pouring sequence as per the formwork drawing (avoiding eccentric loading). This will help ensure that the formwork is not subjected to excessive loading.
9. Preventing Heaping of Concrete: It is important to prevent heaping of concrete and high impact drops from concrete buckets. This will help ensure that the formwork is not damaged by excessive loading.
10. Maintaining Rate of Concreting: It is important to maintain the rate of concreting within allowable limits as shown on the working drawing or as assumed while designing the formwork against lateral pressures. This will help ensure that the formwork is not damaged by excessive loading.
11. Ensuring Bond Between Concrete Layers: In case concrete is placed in layers, it is important to ensure a proper bond between the layers by using a needle vibrator to vibrate the top layer and penetrate the lower layer. This will help ensure that the formwork is strong and stable.

Checklist During Formwork Striking (Stripping or Removal)

1. 1. Design and Layout of Formwork: The design and layout of formwork should be such that it can be smoothly struck in a sequential manner.
2. 2. Strength of Concrete: The strength of concrete should be such that it can bear its own weight and the construction load.
3. 3. Removal Time: The removal time must be ascertained based on the size, shape, and span of the member, grade of concrete mix, rate of gain of strength, type of cement, ambient temperature, weather conditions, and extent of curing.
4. 4. Protection of Corners and Edges: At the time of removal of side formwork, the corners and edges should not be damaged.
5. 5. Loosening and Removal of Ties, Clamps and Wedges: The ties, clamps and wedges should be loosened and removed gradually.
6. 6. Removal Time in Line with Code of Practice: The removal time should be in line with those specified in the code of practice (IS 456- 2000).
7. 7. Removal of Props in Stages: In case of beams and slabs, the props should be removed in stages from mid-span working outwards.
8. 8. Collection of Bolts, Nuts, Clamps and Wedges: The bolts, nuts, clamps and wedges should be collected in a box and not dropped carelessly.
9. 9. Avoidance of Crowbars: The use of crowbars to pry open forms should be avoided.
10. 10. Formwork Prised Loose using Wooden Wedges: The formwork should be prised loose using wooden wedges.
11. 11. Careful Lowering of Formwork: The formwork should be carefully lowered and not dropped and damaged.
12. 12. Removal and Lowering of Panel Faces: The panel faces should be carefully removed and lowered without them hitting the scaffold projections.
13. 13. Placing of Panels on Leveled Surface: The panels should be placed on a leveled surface after removal.
14. 14. Hammering Down of Nail Projections: The nail projections should be hammered down.
15. 15. Cordoning off of Area: The area below the location where formwork removal is proposed should be cordoned off.
16. 16. Presence of Competent Crane Operator and Foreman: The presence of a competent crane operator and foreman is essential.

Checklist for Cleaning and Storage of Formwork

1. When removing formwork, it should be cleaned with a stiff brush to ensure any dust, dirt, and stubborn bits of concrete or grout are removed. Timber surfaces and uncoated ply should be coated with a release agent before being stored. Steel formwork should be lightly coated with oil to prevent corrosion.
2. Repairing Damaged Formwork Any damaged formwork should be sorted out and repaired before storage. This includes repairing depressions, nail holes, and other damage with suitable materials and lightly rubbing down to give a smooth surface.
3. Storing Formwork Panels and plywood sheets should be stored on a horizontally leveled floor, face to face to protect the surface. The storage area should be protected from rain and moisture and well-ventilated. All formwork materials should be stacked off the ground. Loose wailing, soldiers (struts), bolts, nuts, champs, pins, wedges, keys, and ties should be stored with respective panels after numbering for proper match when reused. These should be stored in separate bins or boxes.