Excess of alumina in the clay
- AMakes the brick brittle and weak
- BMakes the brick wrap and crack on drying and burning.Correct
- CChanges the colour of the brick from red to yellow
- DImproves impermeability and durability of the brick
Solution
Concept
Effect of excess alumina in brick clay
Formula
NONE
Step-by-step solution
1. Alumina is a principal constituent of brick earth, imparting plasticity needed for molding. 2. If alumina is present in excess, it causes raw bricks to shrink excessively during drying and burning. 3. This excessive shrinkage leads to warping and cracking of the bricks. Answer: B
Explanation
Alumina provides the necessary plasticity for molding clay into brick shapes. However, an excess of alumina causes the clay to absorb too much water during preparation. As a consequence, raw bricks warp and crack as they dry and burn in the kiln.
Why the other options are wrong
A) Excess silica makes bricks brittle and weak. C) Iron oxide gives bricks a red color, while excess lime turns them yellow. D) Excess alumina causes warping and cracking, reducing durability.
Shortcut
Excess Alumina = Warping and cracking of brick upon drying.
Common mistake
Confusing the warping and cracking caused by excess alumina with the brittleness caused by excess silica.
Correct answer: B) Makes the brick wrap and crack on drying and burning.