The approximate Calcium oxide composition limits of Ordinary Portland cement is
- A60 – 67%Correct
- B17 – 25%
- C3 – 8%
- D0.1 – 4%
Solution
Concept
Calcium oxide content in Portland cement
Formula
NONE
Step-by-step solution
1. Calcium oxide (lime, CaO) is the primary raw chemical constituent of Ordinary Portland Cement. 2. Lime provides strength and soundness to the cement paste when hydrated with water. 3. The typical chemical composition range of Calcium oxide in Portland cement is between 60% and 67%. Answer: A
Explanation
Calcium oxide, commonly known as lime, is the predominant chemical ingredient in Ordinary Portland Cement. It reacts with silica, alumina, and iron oxide in the kiln to form the main binding compounds responsible for hydraulic strength. In standard cement manufacturing, calcium oxide forms approximately 60 to 67 percent of the total chemical composition.
Why the other options are wrong
B) 17 – 25% represents the typical composition range for Silica in cement. C) 3 – 8% corresponds to the approximate percentage range for Alumina in cement. D) 0.1 – 4% represents minor constituents like alkalis or sulfur trioxide.
Shortcut
Lime (CaO) makes up the largest proportion of OPC at 60–67%.
Common mistake
Confusing the high proportion of Calcium Oxide (60–67%) with the proportion of Silica (17–25%) in cement.
Correct answer: A) 60 – 67%