Today I am going to describe the types of water in hydrated cement paste.I believe that you know the types of voids present in hcp or hydrated cement paste.If you don’t know please read it.
The various types of water in hydrated cement paste are :
Types of Water in Hydrated Cement Paste
- Water present in voids larger than about 50 Å.
- It may be pictured as the bulk water that is free from the influence of the attractive forces exerted by the solid surface
- Free water – water in large voids of the order of >50 nm (0.05 μm), (because its removal does not cause any volume change)
- Water held by capillary tension in small capillaries (5 to 50 nm), the removal of which may cause shrinkage of the system
- Water that is close to the solid surface
- Under the influence of attractive forces, water molecules are physically adsorbed onto the surface of solids in the hydrated cement paste.
- A major portion of the adsorbed water can be lost when hydrated cement paste is dried to 30 percent relative humidity
- The loss of adsorbed water is responsible for the shrinkage of the hydrated cement paste.
- The water associated with the C-S-H structure is held by hydrogen bonding.
- The interlayer water is lost only on strong drying (i.e., below 11 percent relative humidity). The C-S-H structure shrinks considerably when the interlayer water is lost.
4.Chemically combined water
- Chemically combined water is another types of water in hydrated cement paste.
- The integral part of the microstructure of various cement hydration products.
- This water is not lost on drying; it is evolved when the hydrates decompose on heating.
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