Question

What is the requirement of water (expressed as % of cement w/w) for the completion of chemical reactions in the process of hydration of OPC?

• A. 10 to 15%
• B. 15 to 20%
• C. 20 to 25%
• D. 25 to 30%

Answer 1

The correct option is C 20 to 25%

It may be noted that $C_{3}S$ requires 23% of water by weight of cement and $C_{2}S$ requires 21%. It means that on an average 23% of water by weight of cement is required for chemical reaction with portland cement compounds. This 23% of water chemically combines with cement and therefore, it is called bound water. A certain quantity of water (about 15% by weight of cement) is imbedded within the gel pores. This water is known as gel-water. Therefore, a total 38% of water by weight of cement is required for the complete chemical reactions and to occupy the space within gel pores.