Curing of Concrete

We have heard this advice or instruction from superior “Ensure proper concrete curing” all the time.

Why?. Because using the right grade of concrete and making a proper mix ratio is just 50% of concrete work. The structure needs to be in a moist condition for at least 28 days to attain its ultimate strength.

The curing of concrete alone plays a vital role in concrete strength.

What is the Curing of Concrete?

Curing is the process of developing concrete strength by moisturizing its surface. When curing, concrete absorbs the necessary water (moisture content) for its complete chemical action to reach its maximum strength. 

The concrete will not attain the design strength immediately. The concrete will take 24 hours to reach its 16% of design strength, and the concrete achieves its full strength in 28 days.

Days	Strength Percentage
Day 1	16%
Day 3	40%
Day 7	65%
Day 14	90%
Day 28	100%

Importance of Concrete Curing

• Proper curing makes the concrete attain its full compressive strength.
• Without moisture content, the concrete will be exposed to hot weathering conditions, which creates shrinkage cracks on the initial hardened concrete.
• Proper curing increases the durability of the structure. 

Curing Period of Concrete

The curing period should continue depending upon the atmospheric conditions such as temperature, humidity, and wind velocity.

The curing period also depends upon the type of cement and the nature of the work.

• In case portland cement is used for concrete, then the curing period should not less than 7 to 14 days.
• If rapid hardening cement is used, then the curing period will be 7 to 10 days.
• In cold weather conditions, the concrete should be cured for 14 days.

Types of Curing

We have to consider the below-mentioned factors before selecting any mode of curing.

• The water loss must be prevented.
• The temperature must be kept to a minimum to scatter the heat of hydration.

Based on the type of construction work, the concrete will be cured by any of the following methods. 

• Water Ponding
• Wet Hessian or Gunny Bags Curing
• Sealing Curing Compounds
• Chemical Curing
• Membrane Curing
• Steam Curing

Water Ponding

The water ponding curing method is a widely used method to cure the concrete.

This method is applied for flat surfaces. A small clay bund or water-retaining material is provided around the perimeter of the surface. The whole surface is divided into small portions by the bund and those enclosed areas filled with water.

The water ponding curing is generally used for pavements and floor slabs.

Wet Hessian or Gunny Bags Curing

A best curing way for a vertical member of a structure is by covering it with wet Hessians and by frequent water spraying method.

The column and walls are cured by spraying water on the surface at regular intervals.

Sealing Curing Compounds

The concrete surface is applied with a coat of solvent or water-based sealing curing compound immediately after finishing. 

The coat prevents the evaporation of water from the concrete and moist remains for long periods.

Chemical Curing

The chemical curing of concrete methods applied when water is scarce. In this method, water is added to the hygroscopic material and sprinkled over the surface.

The hygroscopic material absorbs moisture from the atmosphere and keeps the surface damp.

Membrane Curing

The membrane curing method is widely used in highway construction. The membrane curing of concrete methods is also used in water scarcity areas.

The membrane covering the surface retards the water evaporation from the structure and retains the moisture.

Steam Curing

Curing done by water vapor known as steam curing. It is done under 2 conditions such as 

• Under atmospheric pressure
• Under high pressure

Steam curing is done to gain rapid early strength on concrete. It will be applied on hardened concrete after 3 hours in a controlled manner. The precast concrete element is often cured by steam pressure.

Happy Learning 🙂