All You Need to Know about Concrete Curing

The most important step to maintain the strength of a concrete structure is to ensure that it does not develop cracks. One of the major problems that occurs due to the hardening of concrete is shrinkage cracks. It weakens the structure with time. So to ensure that it does not happen, concrete curing is performed.
Curing is the process of ensuring that moisture stays on the concrete to avoid it from hardening and developing cracks. Due to proper hydration, the strength and durability of concrete structure also increases. Various concrete suppliers too emphasize the importance of curing to the buyers beforehand. 
Curing takes place immediately after placing the concrete and deals with maintenance of the desired temperature and moisture for extended periods of time. Just after the structure has been constructed and the surface is hard enough, such that a person can walk on it without damaging the concrete, curing should be started then and there. 
Methods of curing depend upon the type of surface:
  • Ponding (Used for flat members/slabs): This process of curing is viable for flat surfaces like rooftops or slabs. Here the surface is impounded by about 50mm of water and is surrounded by bunds of mortar or mud to retain the water pond. After frequent intervals, this pond is refilled.
   
  • Wet Coverings(Used for columns, sloped surfaces, beams, concrete walls/retaining walls): Here the concrete structures are covered with wet jute bags, straws etc. then water is sprinkled on these coverings continuously, for consistent wetness. The surfaces here should not be allowed to remain dry even for a short period of time.
Intermittent curing is not good for structures overall strength and durability.
The length of curing time depends upon many factors such as the weather conditions, the size and shape of the concrete member, mixture proportions and strength of the mixture. Other factors may also include the grade of concrete provided to you by the concrete dealership.
How curing benefits?
A compound called C-S-H gel is produced when a chemical reaction between cement & water occurs. It bonds the ingredients of concrete, namely coarse & fine aggregates, mineral admixture, etc. and converts these fragments into a solid mass. 
This is possible when curing is uniformly done for at least 14 days. So the blended cement is required to go through curing in order to convert calcium hydroxide into C-S-H gel.
To have a dense microstructure and impermeability, prolonged curing is a must which leads to enhanced durability. Well-designed concrete may give poor durability if not properly cured and on the other hand, a moderately designed concrete if well cured can give better durability.
It influences the property of concrete in the following ways:
  • Gives concrete a better surface hardness and makes it strong enough to withstand surface wear and abrasion.
  • Makes it impermeable i.e. no moisture or waterborne chemicals could seep through its surface.
  • Improves its long term appearance and makes it shrinkage proof.
  • Prevents grazing, dusting , surface disintegration and scaling. 
Such is the importance of this process. 
In addition, to improvise the steps of curing, you can also involve well trained concrete contractors, who could guide you to keep the quality of concrete in check.

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