Concrete Curing and Formwork Stripping Calculator

Concrete gains strength through hydration, which needs moisture and time. Removing formwork too early can cause sagging, cracking or collapse, while stopping curing too soon leaves the surface weak and permeable. This calculator estimates the minimum curing duration and formwork removal times for common structural members.

How to use it

1. Choose the member type: vertical faces of columns, walls and beams, slab soffits, or beam soffits.
2. Enter the span where relevant.
3. Choose the cement type and exposure conditions.
4. Read the minimum curing period and the earliest formwork stripping times.

Typical IS 456 stripping times (OPC, normal temperature)

• Vertical formwork to columns, walls and beams: 16 to 24 hours.
• Slab soffits, props left under: 3 days.
• Beam soffits, props left under: 7 days.
• Props to slabs spanning up to 4.5 m: 7 days; over 4.5 m: 14 days.
• Props to beams and arches spanning up to 6 m: 14 days; over 6 m: 21 days.

Curing duration

IS 456 requires exposed surfaces to be kept continuously moist for at least 7 days with ordinary Portland cement, and at least 10 days with mineral admixtures or blended cements such as PPC and PSC, extended to 10 and 14 days in dry and hot weather.

Site tips

• Cold weather slows hydration: below about 10 °C, stripping times should be increased.
• Use cube test results where available; the engineer may permit earlier striking once required strength is reached.
• Use ponding on slabs, wet hessian on columns, or curing compounds where water is scarce.