Why curing of concrete is important | Different way of curing

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What is the curing of concrete?

The process of maintaining the heat of hydration in the cement for getting the strength and protect from moisture loss within the proper temperature range is called the curing of concrete.

Due to the exothermic reaction, the heat produced in the concrete evaporates the water and it causes the moisture loss. In order to protect the water loss, water is sprayed on the outer layer of the concrete.

Concrete gain strength over 28 days of casting, the initial strength is developed in 7 to 10 days.

Why curing of concrete is important??

Curing directly affects the quality control and quality assurances of the overall structure. Good curing will directly boost the following features of concrete:

  • Durability
  • Strength
  • Water-tightness
  • Abrasion resistance
  • Volume stability
  • Resistance to freezing and thawing
  • Resistance to drying, shrinkage, and cracking.

Effect of curing duration on compressive strength:

Why curing of concrete is important | Different way of curing
Fig: compressive strength vs time.

The compressive strength of the concrete is affected by curing and its application. Significant Increase in the compressive strength of the concrete depends upon the age of curing.

When the concrete is cured, the pore structure gets improved and lower porosity means a greater degree of cement hydration and reaction occurs without the loss of moisture in a concrete structure which increases the compressive strength of the concrete.

The compressive strength of concrete is directly proportional to the time of curing. It will gain more strength when it is cured for a longer duration.

According to the American Concrete Institute, the minimum days of curing is to be done until the time concrete gains 70% of its compressive strength.

The minimum time to gain 70% of the compressive strength of the concrete is 7 days for OPC. In Nepal, curing is done for 28 days in order to gain its full compressive strength.

Effect of temperature on compressive strength:

Different ways of curing of concrete

Curing of the concrete can be done in various ways and some of them are given below.

Ponding:

Ponding is generally used for almost every constructional work.The process of providing thin layer of water on the top of concrete is called ponding. The small amount of clay puddle are made all around the area and is kept filled with this layer of water.

Why curing of concrete is important | Different way of curing
  Fig: ponding method.

Spraying water:

In this process water is sprayed continuously over the surface of concrete. The surface is covered with jute cloth to keep it wet. This types of curing is done where there is scarcity of water.

Why curing of concrete is important | Different way of curing
Fig: spraying method.

Fogging:

In this process a continuous mist is created around the concrete member instead of spraying water.

Steam curing:

This is very fast process of curing used for precast RCC member. The members are kept in the steam chamber for curing and steam under the pressure is sprayed over the concrete structure.

Addition of chemical:

In this method, chemicals are added to reduce the moisture loss from the concrete. No other curing method is required to be done if some construction chemical is added.

Membrane curing:

In this process the concrete surface is covered by some water proof membrane like bitumen emulsion, wax, rubber latex emulsion, plastic films, etc. 

What is the minimum curing period of concrete?

The minimum curing period of different structure like column, slab, beam, wall etc are given below.

According to the IS code:

Basis:Minimum day for curing
OPC7 days
Blended cement10 days
Mineral admixtures added14 days
Hot and dry condition10 days

I hope this post remains helpful for you.

Happy Learning – Civil Concept

Contributed by,

Civil Engineer – Shreya Parajuli

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