METHODS OF CONCRETE CURING

Concrete Curing

Concrete curing is the process of maintaining adequate moisture in concrete within a proper temperature range in order to aid cement hydration at early age.Curing will increase the strength and decrease the permeability of hardened concrete.Curing is also helps in reducing thermal and plastic cracks, which can severely impact durability of structure.

A curing practice involves keeping the concrete damp or moist until the hydration of concrete is complete and strength is attained.Hydration is the chemical reaction between cement and water that results in the formation of various chemicals contributing to setting and hardening.Curing of concrete should being soon after initial setting time of concrete or formwork/shuttering is removed and must continue for a reasonable period of time as per specified standards, for concrete to achive its desired strength and durability.

Method Of Concrete Curing

1. Pounding Method
2. Sprinkling of Water
3. Steam Curing
4. Membrane Curing
5. Covering with Wet Sheets
6. Shading Concrete 

1. Pounding Method

Pounding is the best method of curing.It is suitable for curing horizontal surface such as floors, roof slabs, lintels, road and air field pavements.A temporary pond is made by mortar made up of less amount cement and sand or clay.The area is thus divided into a number of rectangles and this is filled with water for curing.This is the best and efficient method curing however this is very water extensive.

2. Sprinkling Of Water

Sprinkling of water continuously on the surface provides an efficient curing.It is mostly used for slabs curing.In this method water is sprayed over the concrete surface when ambient temperature is more than freezing temperature and humidity is low for keeping surface moist, as low humidity and high temperature causes quick evaporation.

3. Steam Curing

Steam curing method is adopted during cold weather condition that facilitates rapid hardening of concrete.This is the fastest method of curing compared to other curing methods.This method is used in Pre-cast concrete work.In steam curing the temperature of steam should be restricted to a maximum of 75℃ as in the absence of proper humidity (about 90%) the concrete may dry soon.In case of hot water curing, temperature may be raised to any limit at 100℃.At this temperature the development of strength is about 70% of 28 days strength after 4-5 hours.

4. Membrane Curing

Membrane curing comes under the category of moist curing.In this method of curing is to cover the wetted concrete surface by a layer of water proof material, which is kept in contact with the concrete surface of 7 days. A membrane will prevent the evaporation of water from the concrete.This membrane can be either in solid or liquid form.They are also known as sealing compounds. Bituminised water proof paper, wax emulsions, bitumen emulsions and plastic films are common types of membrane used.

Whenever bitumen is applied over the surface for curing, it should be done only after 24 hours curing with gunny bags.The surface is allowed to dry out so that loose water is not visible and then liquid asphalt sprayed throughout.The moisture in the concrete is thus preserved.It is quite enough for curing.

5. Covering with Wet Sheets

This is a widely used method of curing, especially for structural concrete.In this method exposed surface of concrete is prevented from drying out by covering it with jute bags or empty cement bags.The covering over vertical and sloping surface should be secured properly.These are periodically wetted.The interval of wetting will depend upon the rate of evaporation of water.It should be ensured that the surface of concrete is not allowed to dry even for a short time during the curing period.

6. Shading Concrete

The object of shading concrete work is to prevent the evaporation of water from the surface even before setting.This is adopted mainly in case of large concrete surface such as road slabs.This is essential in dry weather to protect the concrete from heat, direct sun rays and wind.It also protect the surface from rain.In cold weather shading helps in preserving the heat of hydration of cement thereby preventing freezing of concrete under mild frost conditions.Shading may be achived by using canvas stretched on frames.This method has a limited application only.