High percentage presence of free silica in lime exhibits
- Agood cementing and quick setting properties
- Bhigh strength and cementing properties
- Cgood cementing and hydraulic properties
- Dpoor cementing and hydraulic propertiesCorrect
Solution
Concept
Effect of silica in lime
Step-by-step solution
1. Free (uncombined) silica is inert sand, not reactive clay-silica. 2. It does not combine with lime to form hydraulic compounds. 3. A high percentage of free silica gives poor cementing and hydraulic properties.
Explanation
Hydraulic properties come from silica and alumina combined as clay. Free silica behaves like sand and dilutes the lime, so the product has poor cementing and hydraulic properties.
Why the other options are wrong
Options (a), (b) and (c) credit lime with good cementing, strength or hydraulicity, which a high free silica content does not give.
Shortcut
Free silica = inert; clay = hydraulic.
Common mistake
Assuming that all silica makes lime hydraulic.
Correct answer: D) poor cementing and hydraulic properties