Definition of Concrete Curing
Curing is a procedure that is adopted to promote the hardening of concrete under conditions of humidity and temperature which are conducive to the progressive and proper setting of the constituent cement. Curing has a major influence on the properties of hardened concrete such as durability, strength, water-tightness, wear resistance, volume stability, and resistance to freezing and thawing.
Concrete that has been specified, batched, mixed, placed, and finished can still be a failure if improperly or inadequately cured. Curing is usually the last step in a concrete project and, unfortunately, is often neglected even by professionals.
Methods of Curing Concrete
The best curing method depends on:
- Application equipment required
- Materials available
- Size and shape of the concrete surface
1. Keep concrete in water
Keep the concrete immersed in water during the curing period to fulfill the moisture requirements of concrete. This can be done by:
- Ponding or immersion
- Spraying or fogging
- Fogging minimizes moisture loss during and after placing and finishing of concrete.
- Saturated wet coverings
Such methods provide some cooling through evaporation, which is beneficial in hot weather.
2. Prevent the loss of the existing water
Prevent the loss of the mixing water from concrete by sealing its surface. This can be done by:
- Covering the concrete with impervious paper or plastic sheets.
- Polyethylene film is an effective moisture barrier for curing concrete and easily applied to complex as well as simple shapes. To minimize discoloration, the film should be kept as flat as possible on the concrete surface.
- Applying membrane-forming curing compounds.
- Penetrating sealers help protect reinforcing steel in bridge decks from corrosion due to chloride infiltration without reducing surface friction
3. Steam Curing
Strength gain can also be accelerated with:
- Live steam
- Heating coils
- Electrically heated forms or pads
Requirements for curing
- Time - 3-7 Days
- Temperature - 50-100 F
- Moisture - Saturated at all times
Effect of Curing on concrete performance
The purpose of curing is to ensure that the concrete does not dry out prematurely, but retains moisture so that it will build up strength and gain durability and resistance to wear. The concrete should be kept continuously damp for at least 7 days to achieve satisfactory curing. The easiest method is to cover the concrete with plastic sheeting immediately after finishing.
- Increases Strength
- Increases Water tightness
- Increases Abrasion resistance
- Increases Freeze-thaw resistance
- Increases Volume stability
- Decreases permeability
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