Quality of Water:

In the previous units, the importance of various ingredients like, cement, coarse and fine aggregates, etc. have been elaborates. Water is one of the most important and least expensive ingredients of concrete which, in general, is used for various purposes like as, hydration of cement, workability of fresh concrete and curing of hardened concrete. It is not just the quantity but also the quality of water, which plays an important role in ensuring the good quality of concrete as water is responsible for proper hydration of cement, adequate workability of fresh concrete and strength and durability of hardened concrete. If appropriate quantity and adequate quality of water is not monitored during manufacturing of concrete, it may lead to poor quality of concrete in spite of using all other ingredients of fine quality. As per IS: 456 - 2000, mixing and curing of concrete with sea water is not recommended because of the presence of harmful salts in sea water. Generally, water found satisfactory for mixing is also suitable for curing concrete.

The quantity of water should be sufficient to perform the complete hydration of cement and to provide proper workability to the concrete mix. If quantity of water is too less then complete hydration of cement will not take place, also the workability of concrete mix will be too harsh. If quantity of water is too excessive then it will lead to poor strength of concrete, large porosity and poor durability. So, the quantity of water should be carefully controlled. In actual practice at construction sites it has been observed that the people are least concerned about the quantity and, within particular, about the quality of water used for manufacturing the concrete.

In order to define the quality of water it is necessary to know the effects of various impurities on the quality of concrete. The impure water may be rich in suspended particles; it may contain various inorganic salts or organic compounds; it may be acidic or alkaline in nature; it may contain algae, oil or other contamination. Commonly, the water that is fit for drinking purpose may be considered suitable for making concrete. We will now discuss these impurities and their effect on the quality of concrete.