Concrete curing, purpose, types and curing time

The concrete curing is the process of keeping newly placed concrete moist and at a favorable temperature, usually for a specified period of time after it has been placed and compacted. 

Curing helps to ensure that concrete develops the desired strength and durability by allowing it to fully hydrate and harden.

Purpose Of Concrete Curing

1. Helps to maintain proper moisture levels in the concrete during the early stages of hydration, which promotes the chemical reaction that hardens the concrete.
2. Reduces the risk of surface defects and improves the overall appearance of the finished concrete.
3. Minimizes cracking, shrinkage, and reduced durability by preventing the concrete from drying out too quickly.
4. Enhances the strength and durability of the concrete by allowing it to fully hydrate and harden over time.
5. Improves the resistance of concrete to various environmental factors such as freeze-thaw cycles, chemical attacks, and abrasion.
6. Ensures that the concrete meets the required specifications and standards for strength and durability.
7. Allows the concrete to reach its full potential, providing the desired performance and service life.

Methods of concrete curing

There are several methods for curing concrete, each with its advantages and disadvantages. The selection of the curing method depends on various factors such as the type of concrete, the environmental conditions, the desired strength and durability, and the curing duration. 

Here are some of the common types of concrete curing methods:

1. Water curing
2. Ponding
3. Wet covering
4. Chemical curing
5. Steam curing
6. Membrane curing

Water Curing: Water curing is a traditional and effective method of curing concrete, which involves keeping the concrete surface continuously wet with water for a specified period. 

It can be done by sprinkling water over the concrete surface, using a sprinkler, or covering it with wet burlap. 

Water curing helps to maintain a favorable moisture level for concrete to hydrate and develop strength. However, it requires a continuous water supply and may not be suitable in cold weather.

Ponding: Ponding curing is a type of water curing method in which a pond or a temporary pool of water is created over the concrete surface, and the concrete is kept submerged in water for a specified period. 

This method involves creating a shallow pond using sandbags, earth embankments, or other barriers around the concrete surface, and then filling it with water to a depth of at least 50mm.

Wet Covering: Wet covering is similar to water curing, but it involves covering the concrete surface with a wet material such as wet gunny bags, burlap, canvas, or plastic sheeting. 

Wet covering helps to retain moisture and heat within the concrete, promoting hydration and reducing the risk of shrinkage and cracking. 

It can be a more practical option than water curing, especially in hot or windy conditions.

Chemical Curing: Chemical curing involves the application of curing compounds or sealers that form a protective film over the concrete surface, preventing moisture loss and promoting hydration. 

These compounds can be either water-based or solvent-based and are available in different forms such as sprayable, rollable, or paintable. Chemical curing is easy to apply and provides a uniform curing environment, but it may affect the appearance or surface quality of the concrete.

Steam Curing: Steam curing is a faster and more efficient method of curing concrete, which involves exposing the concrete surface to high temperature and high humidity using steam or hot water. 

This method can accelerate the strength gain and reduce the curing time of concrete, but it requires special equipment and careful monitoring to avoid thermal shock or cracking.

Membrane Curing: Membrane curing involves the use of impermeable membranes such as polyethylene sheeting or special curing paper that covers the concrete surface, preventing moisture loss and promoting hydration. 

This method is easy to apply and can be useful in windy or dry conditions, but it requires careful handling to avoid membrane puncture or delamination.

Concrete Curing time as per IS 456:2000

According to IS 456:2000, the minimum duration of curing for different types of cement and environmental conditions are as follows:

Ordinary Portland Cement (OPC):

• Minimum curing period for concrete exposed to dry and hot weather conditions: 10 days.
• Minimum curing period for concrete exposed to other weather conditions: 14 days.

Concrete Curing time for different concreting work

Here are some guidelines for curing time for different concrete works:

Slabs and Floors:

• Minimum curing time for concrete slabs and floors: 7 days.
• Recommended curing time for concrete slabs and floors: 14 to 28 days.

Columns and Beams:

• Minimum curing time for concrete columns and beams: 7 days.
• Recommended curing time for concrete columns and beams: 14 to 28 days.

Walls:

• Minimum curing time for concrete walls: 7 days.
• Recommended curing time for concrete walls: 14 to 28 days.

Footings and Foundations:

• Minimum curing time for concrete footings and foundations: 7 days.
• Recommended curing time for concrete footings and foundations: 14 to 28 days.

Bricks:

• Minimum curing time for bricks: 7 days.
• Recommended curing time for bricks: 14 to 28 days.

Plaster:

• Minimum curing time for plaster: 7 days.
• Recommended curing time for plaster: 14 to 28 days.