Concrete curing is one of the most important processes in achieving the desired properties of the concrete. The test cubes of any particular mix will be immersed in water till the day of testing. This is done in order to promote the hydration process of the concrete. The initial mixing water used to make concrete will not be sufficient to bring out the full performance of the concrete. However, the actual structures can not be immersed in water. That is why the structures will be covered with wet gunny sack or plastic sheet. The reason being that either we provide water (from gunny sack) to promote continuous hydration or we protect the initial water from evaporating. Then again, this is not as easy as it sounds. It is not widely practiced in construction industry (except in much regulated countries).
This is one of the main reasons why the concrete structure does not last through the design life (or at least half of it). Therefore, now it is time to think of a way to cure the concrete from inside without having to cover it with gunny sack or plastic sheet. This new technology is called self-curing concrete. As it name sounds, the concrete would be able to cure on its own without having to provide additional water. This concept is also known internal curing. How is that humanly possible? There have been many discoveries on this new technology, but not much commercial application.
The basic concept of this technology is to provide water for concrete, so that it can continue the curing process on its own. This is done by embedding the water inside the materials used to make concrete. If the water just added as mixing water; This would lead to many other quality related problems, such as bleeding, segregation, and etc. Therefore, a special material shall be used; so that some of the water can be hidden into the material. This water will be released into the concrete over time after the concrete has been placed in the structure and hardened. By doing this the hardened concrete will be able to undergo continuous curing for a long time, which will promote towards a better hydration product. There are many types of material that can be used to impregnate the water. One example is by using feldspar; which is capable of hiding the water into its porous microstructure. The water impregnated feldspar can be used to replace part of sand for the concrete mix. One disadvantages of feldspar is the cost, which is much higher than the normal sand.
Hope you have a basic idea of what is self curing concrete from this article.