Concrete formworks, also known as shutterings, play a vital role in modern construction. They serve as temporary molds to support freshly poured concrete, enabling it to set in the desired shape and gain the necessary strength to bear its own weight and additional structural loads. This article explores the various types of formworks used in reinforced concrete construction and the specific requirements for different structural members.
Introduction to Concrete Formworks
Concrete formworks are indispensable in creating structural elements such as walls, slabs, beams, columns, and footings. Their primary purpose is to provide support and shape to fresh concrete until it solidifies. The materials used for formworks, their design, and the construction techniques depend on the nature of the structure being built. However, their fundamental role remains constant: ensuring the structural integrity of the construction by holding the concrete in place during the critical curing period.
Types of Formwork Based on Structural Members
Formworks are tailored to the needs of various structural components. Each type has unique design and functional requirements:
- Footing Forms – For foundations
- Column Forms – For reinforced concrete columns
- Wall Forms – For reinforced concrete walls
- Floor Forms – For reinforced concrete slabs
These specialized formworks ensure that each structural member achieves the desired shape, strength, and durability.
Footing Forms – Formworks for Foundation
Footing forms mark the beginning of any concrete construction project. Foundations can support either walls or columns, and the formwork design is determined by the type and dimensions of the footing.
- Design Considerations: The size and shape of footing forms are customized based on the foundation’s structural requirements. For instance, shallow footings for walls or columns require specific continuous formwork designs.
- Components of Footing Formwork:
- Side forms to retain concrete
- Supports to prevent lateral displacement
- Joints to ensure a leak-proof assembly
The durability and precision of footing forms directly impact the stability of the entire structure.
Column Forms – Formwork for RCC Column Construction
Reinforced concrete columns present unique challenges due to their narrow cross-sections and tall heights. These factors necessitate formwork with high lateral stability and resistance to the significant pressures exerted by fresh concrete.
- Key Requirements:
- Tight joints to prevent leakage
- Strong tie supports to maintain structural integrity
- Increased stiffness for larger columns through thicker sheathing or vertical stiffeners
- Challenges in Column Formwork:
High rates of concrete placement can lead to lateral deflection, requiring precise engineering to maintain alignment. The robustness of the column formwork ensures the durability of these critical load-bearing members.
Wall Forms – Formwork for RCC Wall Construction
Wall formworks are subjected to relatively lower lateral pressure compared to column forms, thanks to their broader cross-sections. However, they still demand meticulous design to ensure proper alignment and support.
- Components of Wall Formwork:
- Panel Sheathing: Shapes and retains the concrete until it sets.
- Studs: Provide structural support to the sheathing and keep it aligned.
- Braces: Prevent deflection under lateral pressure.
- Ties and Spreaders: Maintain the correct spacing of formwork sides.
Properly assembled wall formworks result in smooth and uniform concrete walls, enhancing the aesthetic and functional quality of the structure.
Floor Forms – Formwork for RCC Slabs
Floor formworks vary significantly based on the type of slab being constructed. These include structural slabs supported by beams or frames and slabs placed directly on compacted soil (slab-on-grade).
- Structural Slab Formwork Assembly:
- Position the girder or beam form at the bottom.
- Overlap girder side forms onto the bottom form, resting on shore heads.
- Secure side forms with ledger strips nailed to the shore heads.
- Stiffen larger girders to prevent buckling.
- Dismantle the formwork systematically, starting with beam and girder sides.
This detailed assembly ensures safe and efficient construction of structural slabs in high-rise buildings and industrial complexes.
- Slab-on-Grade Formwork:
Slab-on-grade formworks are simpler, as they involve laying concrete on compacted soil or gravel bases. The process typically involves: - Forming open edges using planks, plywood, or steel forms
- Securing the forms with wooden pegs
- Placing reinforcements per structural drawings
- Providing construction joints for shear transmission between sections
Both types of floor formworks demand precision and adherence to engineering standards to prevent structural defects.
Conclusion
Formworks are an essential element in concrete construction, offering both functionality and flexibility. From footings to walls, columns, and slabs, each type of formwork is designed to meet specific structural requirements. Properly executed formworks not only ensure the safety and strength of a structure but also contribute to the efficiency and quality of construction projects. By understanding the unique demands of each formwork type, engineers and builders can achieve optimal results in their concrete constructions.
By addressing the technical and practical aspects of concrete formworks, this guide provides a comprehensive overview of their significance in modern construction. Whether it’s the foundation of a skyscraper or the slab of a single-story home, formworks are the unsung heroes that ensure every concrete structure stands tall and strong.