Curing of Concrete: How Many Days, Methods and Mistakes
How many days to cure concrete? IS 456 asks for exposed concrete to be kept continuously moist for at least 7 days with ordinary Portland cement (OPC), and at least 10 days with blended cements such as PPC or mixes with fly ash or slag. In hot, dry weather the minimum rises to at least 10 days, and up to 14 days is recommended for blended cements. Curing means keeping the concrete wet and not too hot so the cement can keep reacting. Stopping early leaves weaker, more porous concrete that cracks and lets steel rust.
On many sites, curing is the step that gets cut short: the slab looks hard after a day, the water tank is far away, and the workers move on. Yet the strength and durability of every RCC member depend on it. This guide explains why curing matters, how many days each element needs, the right methods for slabs, columns, walls and plaster, and the common mistakes.
Last updated: 24 October 2026
Why curing matters
Concrete hardens through a chemical reaction between cement and water, called hydration, which continues for weeks. If the surface dries out early:
- Strength is lower, because the cement near the surface stops reacting.
- The surface is weak and dusty, and wears or flakes.
- Cracks appear, from plastic and drying shrinkage.
- Durability drops: the outer layer, the cover that protects the steel, becomes porous, so water and air reach the bars sooner and they rust.
Curing does two things: it keeps water in the concrete, and it keeps the temperature from rising too high, especially in Indian summers.
How many days? Curing periods at a glance
| Situation | Minimum moist curing (IS 456) |
|---|---|
| Concrete with OPC, normal weather | At least 7 days |
| Concrete with blended cement (PPC, PSC) or mineral admixtures | At least 10 days |
| Hot and dry weather | At least 10 days |
| Blended cements or mineral admixtures, recommended | Extended to 14 days |
These are minimums. Many engineers specify 10–14 days for slabs and roofs in summer whatever the cement. For the difference between cement types, see OPC vs PPC cement.
Typical strength gain with good curing (OPC)
| Age | Approximate share of 28-day strength |
|---|---|
| 3 days | About 40% |
| 7 days | About 65% |
| 14 days | About 90% |
| 28 days | About 100% |
These are common rule-of-thumb figures for OPC concrete; PPC gains strength more slowly at first. Actual values depend on the mix, cement and temperature, which is why cube tests are done; see M20 vs M25 concrete.
When to start curing
Start as soon as the surface has hardened enough not to be damaged by water, usually a few hours after finishing, once a fingernail no longer leaves a mark. In hot, windy weather, protect fresh concrete from the start with wet hessian kept off the surface, a sunshade, or polythene. Do not wait until the next morning; the first 24 hours are when plastic shrinkage cracks form.
Curing methods by element
| Element | Method | Tips |
|---|---|---|
| Roof and floor slabs | Ponding: small bunds of mortar or clay, flooded with water | Keep a continuous layer of water, commonly about 25 mm, topped up daily; cover the edges and chajja with wet hessian |
| Columns | Wrap in wet hessian or gunny bags, or polythene after wetting | Keep the wrapping wet; spraying twice a day is not enough in summer |
| Beams and sides of slabs | Wet hessian, frequent spraying | Formwork left in place also slows drying |
| Footings | Wet hessian, then backfill with moist soil | Do not leave exposed to sun after stripping |
| Walls and plaster | Spraying several times a day | Masonry and cement plaster are commonly cured for about 7 days |
| Where water is scarce | Curing compound sprayed on the surface | Apply right after finishing; it forms a film that holds moisture |
| Precast elements | Steam curing in a factory | Speeds up early strength |
Use clean water that would be acceptable for mixing concrete. Do not cure with sea water or dirty water.
Curing and formwork removal
Formwork removal is a separate question from curing: removing the props too early can crack or deflect a slab even if it is kept wet. IS 456 gives minimum stripping times; for example, props under slabs spanning up to 4.5 m stay at least 7 days with OPC in normal weather. Longer spans, blended cements and cold weather need longer. See RCC full form and the site process. After the sides or soffit are stripped, continue curing the newly exposed faces.
Common curing mistakes
- Stopping after one or two days because the concrete “looks hard”.
- Spraying a slab once in the morning and once in the evening in May sun, letting it dry in between.
- Ponding the middle of a slab while the edges, beams and chajja dry out.
- Leaving columns unwrapped because they are vertical and hard to keep wet.
- Starting curing the next day, after plastic shrinkage cracks have already formed.
- Assuming PPC or ready-mix concrete needs less curing; blended cements need more.
Hindi terms used on site
Curing is तराई (tarai), or simply “pani dena” (giving water). The mortar bunds for ponding on a slab are often called क्यारी (kyari). Hessian or gunny bags are बोरी (bori) or टाट (taat).
FAQ
How many days should concrete be cured?
At least 7 days for OPC concrete and at least 10 days for PPC or other blended cements, with longer periods in hot, dry weather, as recommended by IS 456. Many engineers specify 10–14 days for slabs.
How many days should a roof slab be cured?
At least 7 days with OPC and 10 days with PPC; in summer, 10–14 days by ponding is good practice.
When should curing start?
As soon as the surface is hard enough not to be marked by water, usually a few hours after finishing. In hot or windy weather, protect it from drying even before that.
What happens if concrete is not cured?
It reaches lower strength, has a weak and dusty surface, cracks more, and its cover becomes porous, so the steel inside can rust sooner.
Does PPC need more curing than OPC?
Yes. PPC gains strength more slowly, so IS 456 asks for at least 10 days instead of 7.
How long should plaster and brickwork be cured?
Cement plaster and brick masonry are commonly kept moist for about 7 days. Gypsum plaster does not need water curing; see cement vs gypsum plaster.
Related guides: OPC vs PPC cement · M20 vs M25 concrete · PCC vs RCC · Slump test · All construction guides
Disclaimer: Educational only. Curing periods, methods and formwork removal times must follow your project specification and IS 456, as directed by a qualified engineer. Disclaimer
Tanmay Arora, is an Architect with an experience of 13+ years. He is a Management Grad with a post Graduate Diploma in Building Construction and Materials. Tanmay has worked with renowned firms. He has graduated in Bachelor of Architecture. His deep interest in Architecture and Civil Engineering and his experience has made him one of the best architects a client can think of.
