In brick manufacturing and drying, what is the principal effect of adding adequate sand to the brick earth? Select the most accurate primary benefit recognized in practice.

Introduction / Context:
Brick earth composition is tuned to minimize defects during drying and firing. Sand acts mainly as an inert, non-plastic aggregate within the clay matrix. This question checks whether you know the primary reason sand is added at all to brick earth mixtures on yards and in small plants.

Given Data / Assumptions:

• Clay alone is highly plastic and shows large drying shrinkage.
• Sand is non-plastic and remains dimensionally stable during drying.
• Cracking and warping are symptoms largely driven by shrinkage stresses.

Concept / Approach:

The root cause of many green and dried brick defects is excessive plastic shrinkage. By diluting the plastic clay fraction with sand, total shrinkage reduces. Lower shrinkage directly lowers tensile stresses that would otherwise cause cracking and edge warping. Thus, preventing shrinkage is the primary mechanism; reduced cracking and warping are natural consequences.

Step-by-Step Solution:

Verification / Alternative check:

Traditional brickmaking guides prescribe sand additions to control shrinkage percentages measured on test bars before batch production.

Why Other Options Are Wrong:

Prevents cracking/warping: these are effects, not the primary mechanism. Excessive vitrification: unrelated; vitrification depends on flux content and firing temperature, not on added inert sand.

Common Pitfalls:

Confusing symptom (cracks/warps) with cause (shrinkage); believing that more sand is always better, whereas too much sand reduces strength.

Final Answer:

Prevents shrinkage of bricks