What is the percentage content of Alumina (Al 2 O 3 ) in Ordinary Portland Cement?
- A0.5 to 6.0
- B3.0 to 8.0Correct
- C17 to 25
- D60 to 67
Solution
Concept
Alumina content in Ordinary Portland Cement
Formula
NONE
Step-by-step solution
1. Alumina imparts quick setting property to Portland cement upon hydration. Answer: B
Explanation
Alumina acts as a flux in Ordinary Portland Cement, imparting quick-setting properties and lowering the clinkering temperature during manufacturing. In standard cement composition, the chemical percentage of alumina is strictly maintained within a range of 3.0% to 8.0% by mass. Therefore, option B accurately specifies the required alumina content in Ordinary Portland Cement.
Why the other options are wrong
A) The 0.5 to 6.0 percent range corresponds to magnesia or iron oxide content in OPC. D) The 60 to 67 percent range represents the lime content in Ordinary Portland Cement.
Shortcut
OPC Cement main ingredients by percentage: Lime (60-67%) > Silica (17-25%) > Alumina (3-8%).
Common mistake
Selecting option C or D by confusing the alumina content percentage with silica (17–25%) or lime (60–67%).
Correct answer: B) 3.0 to 8.0