Question

The approximate Calcium oxide composition limits of Ordinary Portland cement is
1. 60 - 65%
2. 17 – 25%
3. 3 – 8%
4. 0.1 – 4%

Answer 1

Correct Answer - Option 1 : 60 - 65%

Explanation:

Ingredients of cement	Percentage
Lime (CaO)	62 - 65 %
Silica	17 - 25 %
Alumina	3 - 8 %
Gypsum	3 - 4 %
Iron Oxide	3 - 4 %
Magnesia	1 - 3 %
Alkalies	In traces

 

The excess of different ingredients causes different affects in the cement as given below:

Ingredient in excess	Affect
Lime	Excess lime causes unsoundness i.e. it expands and disintegrates. If it is in deficiency then strength is reduced.
Silica	Excess silica increases the strength of cement and hence, enhance the setting time i.e. cement sets slowly.
Alumina	Excess of alumina decreases the strength of cement.
Calcium Sulphate or Gypsum	Excess gypsum slowdown the quick setting of cement.
Iron Oxide	Excess iron oxide imparts more coloured to the cement.
Magnesia	Excess magnesia causes unsoundness i.e. it expands and disintegrates.
Sulphur	Excess sulphur causes unsoundness i.e. it expands and disintegrates.