Curing Process Of Concrete

What is CURING ?

Curing is the process of controlling the rate and extent of moisture loss from concrete during cement hydration (Hydration means the chemical combination of cement and water). Since the hydration of cement does take time – days, and even weeks rather than hours – curing must be undertaken for a reasonable period of time if the concrete is to achieve its potential strength and durability.

When to cure?
Curing is done just after finishing the concrete surface, as soon as it will not be damaged. However, In hot and/or windy weather a concrete mix may stiffen rapidly and not be workable. IN COLD WEATHER Frozen or very cold water will also slow down the setting time which can cause costly delays. In extremely cold weather water turns to ice, EXPANDS and can CRACK hardened concrete. In these conditions, we must take extra care while curing.

How to cure?
In hot weather : Keep the concrete continuously moist.

Method 1 →APPLYING WATER
Put a continuous fine, misty spray of water over the concrete or else it will damage the surface of the concrete.

Method 2 →PLASTIC SHEETS

Slow down water loss. The sheets must be held down to stop them blowing away and the concrete surface drying out. The sheets also can be overlapped and stuck together or held down with sand, timber or bricks to prevent them blowing away. We must always check under the plastic from time to time to make sure the concrete is evenly moist. If it feels dry, sprinkle with water and put back the plastic sheets carefully.

Method 3→MEMBRANE-FORMING CURING COMPOUNDS
Curing compounds are liquids which are usually sprayed directly onto concrete surfaces and which then dry to form a relatively impermeable membrane that retards the loss of moisture from the concrete.

Method 4→WET COVERINGS

Fabrics such as hessian, or materials such as sand, can be used like a ‘mulch’ to maintain water on the surface of the concrete. On flat areas, fabrics may need to be weighed down. Also, it is important to see that the whole area is covered. Wet coverings should be placed as soon as the concrete has hardened sufficiently to prevent surface damage. They should not be allowed to dry out as they can act as a wick and effectively draw water out of the concrete.

How Long To Cure?
Concrete keeps getting HARDER AND STRONGER over TIME. Household concrete jobs MUST be cured for AT LEAST 3 DAYS while for better strength and durability, cure concrete for 7 DAYS. The longer concrete is cured, the closer it will be to its best possible strength and durability.