Composite formwork is a relatively new development in the construction industry, combining the properties of different materials to offer a balance of strength, durability, and reusability. It’s gaining popularity due to its versatility and potential cost savings.
Composite Slabs
Composite slabs comprise reinforced concrete cast on top of profiled steel decking, which acts as formwork during construction and external reinforcement at the final stage. The decking may be either re-entrant or trapezoidal, as shown below. Trapezoidal decking may be over 200 mm deep, in which case it is known as deep decking.
Additional reinforcing bars may be placed in the decking troughs, particularly for deep decking. They are sometimes required in shallow decking when heavy loads are combined with high periods of fire resistance. Bars in troughs are also a requirement for single spanning slabs and decks designed as single spanning to ensure continuity and ductile failure in fire design.
Key Advantages of Composite Formwork:
- Strength: Composite formwork is designed to be strong and durable, capable of handling heavy loads and resisting wear and tear.
- Lightweight: Many composite materials are lightweight, making them easier to handle and transport.
- Versatility: Composite formwork can be molded into various shapes and sizes, accommodating a wide range of architectural designs.
- Reusability: Composite forms can be reused multiple times, reducing waste and costs.
- Corrosion Resistance: Some composite materials are resistant to corrosion, making them suitable for environments with moisture or chemicals.
Types of Composite Formwork:
- Plastic-Reinforced Composite Formwork: This type combines plastic with reinforcing materials like fiberglass or steel. It offers a balance of strength, lightweight, and corrosion resistance.
- Wood-Composite Formwork: Made from a combination of wood and other materials, this type offers the benefits of both wood and composite formwork.
- Metal-Composite Formwork: This combines metal with other materials to enhance its properties, such as strength or durability.
Formwork Process:
The process of using composite formwork is similar to other types of formwork:
- Design and Planning: The formwork design is based on the architectural drawings and engineering calculations.
- Assembly: The composite formwork panels are assembled on-site, using temporary supports and connectors.
- Reinforcement: Steel reinforcement bars (rebar) are placed within the formwork.
- Concrete Pouring: The concrete is poured into the formwork, ensuring proper compaction and leveling.
- Curing: The concrete is allowed to cure for a specified period.
- Stripping: Once the concrete has hardened, the composite formwork is removed.
Best Practices for Composite Formwork:
- Proper Handling: Handle composite formwork carefully to avoid damage.
- Cleaning: Clean composite formwork after each use to remove any concrete residue or debris.
- Storage: Store composite formwork in a protected area to prevent exposure to harsh weather conditions.
- Inspection: Regularly inspect composite formwork for signs of wear or damage.
Composite formwork is a promising development in the construction industry, offering a combination of benefits that can improve efficiency and reduce costs. As technology continues to advance, we can expect to see even more innovative composite formwork solutions in the future.
