What is Curing of Concrete?
Curing of concrete is the process of maintaining adequate moisture and temperature conditions in freshly placed concrete to allow it to properly hydrate and gain strength. During curing, water is essential for the hydration of cement particles, which leads to the formation of calcium silicate hydrates (CSH) gel and other cementitious compounds that give concrete its strength and durability. Moreover, improper curing of concrete leads to:
- Reduced strength
- Increased permeability
- Cracking
- Surface defects
- Decreased durability
- Increased maintenance and repair costs
Methods of Curing of Concrete
There are various methods of curing of concrete some of which are discussed here:
Water Curing
Water curing is a method used to cure concrete by continuously wetting its surface with water. This process involves keeping the concrete moist for an extended period after it has been placed and finished. It is commonly used for curing concrete pavements, slabs, and other horizontal surfaces, especially in hot and dry climates where moisture evaporation is rapid. It can be done in the following ways:
Immersion
Immersion is a specific type of water curing method. In this process, freshly placed concrete is completely submerged or immersed in water for a certain period to facilitate hydration and curing. During immersion water curing, the concrete is typically placed in tanks, pools, or containers filled with water. This method ensures constant moisture availability around the concrete, allowing for continuous hydration of cement particles. This method is commonly used for precast concrete members.
Ponding
This method is used to cure concrete by creating a shallow pool of water on its surface. This process involves forming a barrier around the perimeter of the concrete surface and then filling the enclosed area with water to a specified depth, typically around 1 to 2 inches (2.5 to 5 centimeters).
Once the water is in place, it forms a protective layer over the concrete, preventing moisture loss through evaporation. Ponding is particularly effective for curing large horizontal surfaces, such as concrete pavements, slabs, and bridge decks.
Spraying or Fogging
This method of curing of concrete involves applying a fine mist or spray of water onto the surface of freshly poured concrete using specialized equipment such as misting nozzles or fogging machines. The concrete surface is sprayed or fogged at regular intervals to ensure continuous moisture retention. This method is particularly useful in situations where other curing methods, such as ponding or covering with wet materials, may not be feasible or practical.
Wet Covering
This method of curing of concrete involves covering the freshly placed concrete with wet materials like burlap, mats, or cotton mats, to maintain moisture and promote proper hydration of cement. These materials are first soaked in water and then carefully spread over the entire surface of concrete. Wet coverings helps to maintain a moist environment. This method is particularly useful in hot and dry climates or when water curing methods are not feasible.
Membrane Curing
Membrane curing of concrete is a method used to cure freshly poured concrete by applying a liquid membrane or coating to its surface. This membrane acts as a barrier, preventing moisture from escaping and allowing the concrete to retain its required level of hydration during the curing process.
Membrane curing is particularly useful in situations where water curing may not be feasible or practical, such as in vertical surfaces, overhead structures, or areas with limited access to water.
Heat Curing of Concrete
The application of heat for curing of concrete is known as heat curing or accelerated curing. This method involves applying controlled heat to the concrete surface or enclosing the concrete in a heated environment to accelerate the curing process. Heat curing speed up the hydration process of cement in concrete, allowing for faster strength gain and earlier removal of formwork or early loading of structures.
Infra-Red Curing
Curing of concrete using infrared radiation involves the application of heat energy emitted by infrared lamps to accelerate the curing process. Instead of relying on traditional methods like water curing or covering with insulation blankets, infrared radiation provides a direct and targeted source of heat to the concrete surface.
Electrical Curing of Concrete
In electrical curing, electrodes are embedded in the concrete at regular intervals, and an electric current is passed through them. This current generates heat within the concrete, which helps to speed up the hydration process of cement and promote the development of strength and durability in the concrete. This technique is also known as electrochemical curing or electrically accelerated curing.
Curing with wet sand
Curing concrete with wet sand involves spreading a layer of damp sand over the freshly poured concrete surface. This method helps to retain moisture and maintain a humid environment around the concrete, which is crucial for proper hydration of the cement and the development of strength.
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