[7] Main method curing of concrete meaning and purpose and why its important

What is the Curing of concrete?

Curing of concrete meaning the process curing of concrete↗️keeping the finished concrete surface moist to enable it to gain strength is called curing. The physical properties of cement concrete↗️generally based upon the extent of hydration of cement and therefore the resultant microstructure of the hydrated cement. The chemical activity between cement and water, which ends within the setting and hardening of concrete or mortar, relies on the due to the presence of water.  Although there is normally an adequate quantity of water for full hydration when the concrete or mortar mix is prepared, it is important to ensure that the water is either retained or replenished to enable the activity to be continued till such time the specified strength is gained.

A significant loss of water because of evaporation from the concrete surface may end in slowing down or stopping the hydration process and leading to a consequent reduction of strength and sturdiness. so as to assist the hydration process to continue, water within the capillaries should be prevented from evaporating. It is, necessary to keep up an environment of high humidity around the freshly placed concrete or mortar till it attains reasonably for achieving good strength. This process is known as the curing of concrete. 

Why curing of concrete is important The objective of Curing?

The curing plays a vital role and governs the properties of hardened concrete. The objectives of curing are following below.

• It prevents the loss of moisture from concrete.
• It reduces shrinkage in concrete.
• It improves the wear-resisting property of concrete.
• It improves the weather resisting properties of concrete.
• It improves the properties of hardened concrete like strength, durability, impermeability,
• It improves the properties of hardened concrete like strength, durability, impermeability, etc.

Factor-affecting of Curing

There are various methods of curing. The curing methods↗️are generally selected depending on the following factors.

• Specifications
• Availability of curing materials
• Economics
• Type of concrete structure (precast/cast-in-situ)
• Shape and size of the concrete surface
• Aesthetic appearance
• Position of concrete surface (Vertical/horizontal) 

Main types curing of the concrete method 

The following are the main types of curing of concrete methods of curing given below.

1. Ponding Method
2. Membrane Curing  
3. Steam Curing
4. Chemical Curing
5. Sprinkling of water
6. Covering with moist gunny bags
7. Shading the concrete surface

1. Ponding Method

The best curing method is that the total immersion is practically not possible unless the concrete is a laboratory test specimen or a small precast member which can be easily handled and placed in the curing pond. However, curing of flat surfaces such as those of floor slabs,  pavements, concrete roads, sidewalks, etc. can be the best and most popular method in this method cured by ponding water on the exposed top surface. For the first 24 hours, the exposed surface of the concrete is covered with most hessian or canvas. After 24 hours these covers are removed and the complete area is divided into the number of rectangular ponds by small banks of sand or clay. These ponds are filled with fresh water. A large quantity of water is required, for curing, in this method. However, the following precautions are necessary.

• The most water lost because of due to evaporation should be continuously replenished.
• Water should also cover the corner and edges and should be able to cover the entire surface uniformly to avoid dry spots wherein curing is deficient.
• Water used for curing should be of similar properties as that was used for concrete mixing.
• Adequate water should be available at the site throughout the curing period.
• The height of banks of ponds should be so selected that there is at least 20 - 25 mm water on the highest surface.

2. Membrane Curing

It states that applying membrane-forming on the cement concrete↗️ structure is generally known as membrane curing. In this method, a newly laid concrete surface is covered, by using solid or liquid membranes, for 7 days so as to prevent evaporation of moisture from concrete. These curing membranes provide a barrier to prevent loss of water from the freshly placed concrete. Curing with a good membrane for 28 days would give strength equal to two-week moist curing. Commonly used curing membranes (also called sealing compounds) are Bituminised waterproof paper, plastic films, resins, etc. This method is used in regions where the air is dry and there is a scarcity of water.

A more number of sealing compounds have been developed in past years. The main method is to obtain a continuous seal over the exposed surface of the concrete surface by means of a firm impervious film to prevent the escape of moisture by evaporation. 

Also read :-

   👉What is Mineral Admixture Function, types and Uses in concrete
   👉What is Chemical Admixture Function, types and Uses in concrete
   👉Main Properties of Concrete In Hardened Stage And Their Explanation
   👉Main Properties of Concrete in Plastic Stage, Explain Causes And Prevention

 

3. Steam Curing

The process in which steam is used for cur steam curing. This method is in the process in which steam is used for curing of concrete is known as effectively controlled. This procs useful in two ways I .e. temperature and humidity can be his process ensure even heating of products all over, even if the spacing between members is with a low water-cement ratio than for high water-cement ratio mixes. This method of curing is more favorable for mixes The development of strength is very rapid with steam curing. This method is a very used pre-cast industry where members are stacked with minimum spacing. It has been suggested, through researches, that the steam curing of concrete sound followed by water curing for a period of at least 7 days.

Mixes containing water-cement ratios ranging from 0.3 to 0-7 can be cured effectively with the help of steam curing. Steam curing is adopted only for achieving 50 - 70% of specified strength in a shorter period, which would result in the economy in the reuse of molds and types of equipment.

• Note - Steam curing is not adopted when high alumina cement is used.

 4. Chemical Curing

This method of curing includes spraying of sodium silicate (water glass) solution on the concrete. It should be approximately 500 gm of sodium silicate mixed with water that can cover 1 m2 of surface and forms a hard and insoluble calcium silicate film. After hardening calcium silicate results in a thin varnish-like film which helps in filling the pores and surface voids, thus sealing the surface and preventing the evaporation of moisture from concrete.

5. Sprinkling of Water 

This method is one of the simplest methods of curing concrete. This method can be applied to horizontal, vertical, or inclined surfaces of concrete. But the strategy isn't very more efficient effective because it is difficult to ensure that all the parts of concrete be moist all the time. The sprinkling of water can be obtained with the help of plastic or rubber hose pipes or it can be achieved with the help of fine nozzles placed in series at set intervals.

To make the process efficient it is necessary to provide a continuous supply of water. If this operation is done manually, then the workers deployed should be inadequate number and should be deployed round the clock. Frequency of spraying may reduce within the evening or night hours but wetting of surfaces will be required to avoid drying. 

6. Covering with moist gunny bags 

Covering the surface with moist gunny bags or hessian helps in preventing the drying out of the exposed surface of the concrete↗️. This method can be used for both horizontal and vertical members. The gunny bags or hessian cloth have water retention capacity. These are wrapped around the vertical surfaces of concrete and made moist by sprinkling water over them.

7. Shading of concrete work 

Shading of freshly laid concrete can be achieved by using canvas stretched on frame. This method is very useful in hot and dry climates to prevent the evaporation of moisture. In cold climates, it is required to preserve the heat of hydration.

This method of preserving the moisture of concrete is useful for large concrete surfaces such as road or floor slabs. This method may not prove to be successful in case of strong winds. 

conclusion

The curing of concrete is very important because without not proper curing of the concrete is not gain strength properly and the structure is weak. The curing of the concrete method is many but all method depends upon the situation and type of structure and climates. The concrete is after placing it is gaining strength due to proper curing. consistent with the Indian Standard IS, 456 – 2000 highly recommends that the curing duration of concrete must be a minimum of seven days in case of ordinary cement↗️, a minimum of ten days, and far more for any kind of concrete structure.

For more information related curing watch this video