As per IS 456:2000 (Indian Standard code of practice for plain and reinforced concrete), de-shuttering time refers to the time after which formwork (shuttering) can be removed from a concrete structure without causing any damage or deformation to the concrete.
The recommended de-shuttering time for different types of structural elements (such as slabs, beams, columns, etc.) varies based on the grade of concrete used, environmental conditions, and the type of formwork used.
De-shuttering time of formwork as per IS 456
The general guidelines for a de-shuttering time are as per IS 456:2000 cl11.3 are as follows:
| Structural Element | Type of Formwork | Recommended De-Shuttering Time |
| Columns, walls, beams | Vertical | 16-24 hours |
| Slabs | Soffit | 3 days (Props to be refixed immediately after removal of formwork) |
| Beams | Soffit | 7 days (Props to be refixed immediately after removal of formwork) |
| Slabs | Props | – |
| Spanning up to 4.5 m | – | 7 days |
| Spanning over 4.5 m | – | 14 days |
| Beams, arches | Props | – |
| Spanning up to 6 m | – | 14 days |
| Spanning over 6 m | – | 21 days |
1. Formwork
It is a temporary structure or mold that is used in construction to support the concrete until it sets and gains sufficient strength to support its own weight and any other imposed loads. It is also known as shuttering in some regions.
2. Soffit
Refers to the underside of a structural element, such as a slab or beam. Soffit formwork is used to support the concrete as it is poured onto the underside of the structural element.
3. Props
These are vertical or inclined supports that are used to provide temporary support to the formwork and the concrete until it gains sufficient strength. Props are typically made of steel or timber and can be adjusted to the desired height and angle.
4. Vertical formwork
It is used for constructing vertical structural elements such as columns, walls, and other vertical surfaces. Vertical formwork typically consists of panels or sheets that are connected together to create a mold into which concrete is poured.
Factors affecting de-shuttering time of formwork
Factors affecting the deshuttering time can be broadly categorized into two groups – concrete-related factors and environmental factors. Here are some of the key factors that can affect the deshuttering time of concrete structures:
Concrete-Related Factors:
- Grade of Concrete: The strength of concrete is an important factor that affects the deshuttering time. Higher-grade concrete takes longer to gain sufficient strength and requires a longer deshuttering time.
- Type of Cement: The type of cement used also affects the rate of strength gain of the concrete. Rapid hardening cement can reduce the deshuttering time.
- Mix Design: The mix design of the concrete, including the water-cement ratio and the type and amount of aggregate used, can affect the strength gain and setting time of the concrete.
- Curing Method: The curing method used after pouring the concrete can affect the strength gain and setting time of the concrete. Proper curing is essential to achieve the desired strength and durability of the concrete.
Environmental Factors:
- Temperature: Temperature can affect the setting time and strength gain of the concrete. Higher temperatures can accelerate the setting time and strength gain, while lower temperatures can delay it.
