Difficulty: Easy
Correct Answer: Alumina (clay fraction) in excess
Explanation:
Introduction:
Understanding how each constituent of brick earth affects behavior during drying and firing is crucial for quality bricks. This question focuses on warping and shrinkage defects that appear when the clay fraction is not balanced properly.
Given Data / Assumptions:
Concept / Approach:
Alumina imparts plasticity and workability, but too much plastic clay causes large drying shrinkage. Without sufficient sand (silica) as a non plastic temper, bricks deform and warp as water leaves and during sintering.
Step-by-Step Solution:
Verification / Alternative check:
Standard brickmaking texts note that silica reduces shrinkage and helps maintain shape, while alumina increases plasticity and shrinkage.
Why Other Options Are Wrong:
Lime excess risks cracking or melting but is not the primary shrinkage driver. Iron oxide influences color and vitrification. Magnesia can improve color and reduce warpage at small amounts. Sand in excess reduces shrinkage rather than causing it.
Common Pitfalls:
Confusing the role of lime or iron oxide with the plasticity controlled by alumina and silica balance.
Final Answer:
Alumina (clay fraction) in excess
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