curing of concrete is the method to protect against loss of moisture required for hydration and kept within the recommended temperature range and curing fresh wet concrete is allowed to complete its reaction to attain its planned strength.
Curing of concrete will increase the strength and decrease the permeability of hardened concrete and maintain the moisture and temperature conditions of concrete for hydration reaction. As a result of chemical reaction between cementitious materials and water concrete sets and hardens and to develop the desire properties of concrete curing process maintain temperature and moisture conditions.
Moisture, heat and time for the curing process are the main components that need to take care and curing of concrete helps in mitigating thermal and plastic cracks which can impact the durability of the structure.
It is important to take steps to retain the water inside the concrete for 21 days and other ways of retaining the water is by covering the beam or column with a plastic sheet or gunny bags for keeping it wet for 24 hours and the time to start curing of concrete depends on the evaporation rate of moisture from concrete and evaporation rate influenced by wind, radiant energy from sunlight, climate conditions and concrete temperature.
When To Start Curing Of Concrete:
After its setting water is applied for few days over a concrete surface for the hydration reactions b/w cement and water due to which hardening of concrete takes place and gives it good strength.
Procedure Of Curing Concrete:
To the surface of concrete curing is done by draining water and for this purpose water cooler than 5 centigrade should not be used.
Using cold water like this may lead to cracking and also alternate drying and wetting on concrete surfaces.
Methods Of Curing Concrete:
Depending on type of structure and material parameters different types of curing methods are adopted such as;
Water Curing Of Concrete:
By wetting of the exposed surface of the concrete water curing prevents the water loss from the concrete surface and to ensure that the concrete surface is continuously moist the water curing of concrete is done by spraying water or curing agents over the concrete surface.
For the strength gain of concrete moisture from the concrete body is retained from evaporation, water curing methods are;
Fogging and sprinkling
in floor slabs this method is adopted, on slabs small ponds are created and filled with water continuously for 24 days
for columns, footing and bottom surface of slab this method is adopted, wet or gunny bags are used to cover the concrete to keep concrete moist.
Fogging or Sprinkling;
this method is the simplest like spraying the water from sprinklers on concrete surface but more time consuming.
Membrane Curing Of Concrete:
For moisture loss from concrete surface by wrapping it with impermeable membrane the membrane curing method is applied or adopted and the curing compounds are wax and water based liquid and to create an impermeable membrane these are sprayed over fresh concrete. This will reduce the loss of wetness from concrete.
The methods for membrane curing are;
plastic film is used as a moisture barrier for curing concrete and to cure concrete by retaining moisture and heat on concrete polyethylene sheeting is an effective way.
formwork should be left for long time because it helps in curing of concrete.
For quick strength achievement steam curing is used and steam curing keeps the surface moist and raises the temperature of concrete. This process is done because of fast hardening of concrete and mortars. For pre cast concrete plants this method is most commonly used.
To prevent concrete to dry out prematurely due to wind and solar radiation and this prevents plastic shrinkage of concrete
By allowing hydration process to maintain the concrete temperature, it releases heat and requires water to carry on
bond with internal materials and reinforcement and hardening
Helps in development of impermeable, durable and crack free concrete.
Curing Of Concrete Depends On:
The right time of curing of concrete depends upon following factors;
Initial Curing: (Bleeding Of Concrete)
When the concrete is compacted and placed and due to settlement of concrete bleeding of water occurs and rises through surface of concrete.
The rate of bleeding depends upon many factors such as concrete mix properties, method of compaction of concrete and depth or thickness of concrete etc.
From the surface bleed water stars to evaporate and drying of concrete starts when all bleeding water disappeared from the surface. Then to minimize the moisture loss and prevent plastic shrinkage cracks to concrete before and during finishing operations the initial curing of concrete is required. This is done by fogging or using evaporation reducers.
Intermediate Curing Of concrete:
Before the final setting of concrete intermediate curing is done when the concrete surface finishing operations has been carried out. When the setting of concrete is delayed or when the required surface texture of concrete member is achieved rapidly, this happens.
After the final setting of concrete when the concrete is finished the final curing of concrete should be done and this final curing of concrete helps to prevent surface drying of concrete because the loss of moisture from concrete surface occurs.
Points To Keep In Mind When Curing:
There are following points which are important to remember when curing of concrete such as;
After concrete has been place start curing as soon as possible
Concrete needs moisture for proper curing
In hot weather curing of concrete may be dry faster than the chemicals stop right at point where concrete loses its moisture