The presence of water is an essential requirement for the development of high strength concrete.Cement by itself doesn’t have any binding properties. However, the reaction of cement and water produces a compound calcium silicate hydrate( better known as the C-S-H gel) which is the best binder.
Water used in concrete should be free from any impurities and should be portable water which is clean and fit for drinking. Since the presence of acidic and basic salts can affect the strength of concrete. However, if nothing can be done to make clean water available than sea water can also be used taking into consideration the strength losses incurred by the utilization of the former.
The presence of water imparts a natural flow to the concrete making it easier to be used and applied to the surface of the masonry.
The water cement ratio is an essential property for a ready mix design; masons have a bad habit of increasing the proportion of water content in cement compared to the standards which enhance the workability and makes it easier to transport, handle, mix, place and consolidate. However, excessive water content decreases the compressive strength of concrete, according to the inverse relation of water cement ratio and strength of concrete given by Abraham.
A significant use of water is in the curing of concrete. Curing is the process of keeping concrete in contact with water for a minimum period of seven days for its ultimate strength develop. Since water has a high specific gravity, it can take the heat escaping out from the surface of concrete and help in the prevention of thermal cracks formed due to the excessive heat evolved during the process of hydration. The tests done by quality control unit involves testing the compressive strength of a 150 mm concrete cube kept in a curing tank for 3,7,14 and 28 days respectively. A similar test procedure for flexural strength involves curing the briquettes in water and determination of its strength.
Concrete is strong in compression, but weak in tension and hence the tensile strength comes out to be negligible. However, its test is recommended to calculate the amount of reinforcement needed below neutral axis at zones subjected to high tensile stresses and in the development of prestressed concrete. For a newly created structure, the surface is kept moist for several days by putting burlaps and jute sacks over the columns and staircases and enclosing a region full of water for curing the roof, this allows slow escape of heat from the structure and prevents the development of any cracks. Researchers have experimentally found out that steam curing is the best form of curing for ultimate strength development of concrete.
The factors mentioned above prove the importance of water in concrete to be crucial.