Correct Answer - Option 3 :
Alumina
The following table shows the composition of cement and their properties.
| Ingredients |
Within limit
|
If in excess
|
|
Lime
(62 – 65%)
|
Controls strength and soundness
|
Makes the cement unsound and it expands and disintegrate
|
|
Silica
(17 - 25 %)
|
Adds strength to cement, as it forms C2S and C3S
|
Causes slow setting of cement
|
|
Alumina
(3 - 8 %)
|
Provides quick setting of cement and lowers the clinkering temp
|
Lowers the strength
|
|
Iron oxide
(3 - 4 %)
|
Provides color, hardness , strength and helps in fusion of raw material
|
|
|
Magnesia
(1 - 3 %)
|
Provides hardness and color Decreases shrinkage
|
Makes the cement unsound
|
|
Alkalies
(0.2 - 1 %)
|
Should be in limit
|
Alkali aggregate reaction
Efflorescence and staining
|
