Brick earth composition – dominant constituent for good quality bricks The main ingredient that should dominate in a good brick earth is which of the following?

Introduction:
Brick performance depends strongly on the proportion of its raw constituents. Understanding the dominant component in a suitable brick clay (brick earth) helps ensure strength, shape retention, and resistance to shrinkage and warping during drying and burning.

Given Data / Assumptions:

• We refer to ordinary burnt clay bricks.
• “Dominant” means the largest proportion by percentage among the listed constituents.

Concept / Approach:

Good brick earth typically contains silica and alumina as major constituents, with silica usually the predominant fraction. Silica controls shrinkage, imparts hardness, and helps retain shape by preventing excessive warping during drying and firing. Minor constituents (lime, magnesia, iron oxide, alkalies) fine-tune vitrification and color.

Step-by-Step Solution:

Verification / Alternative check:

Standard texts consistently emphasize silica as the largest component for dimensional stability, while alumina gives plasticity for molding. Controlled lime aids fusion but remains a small fraction.

Why Other Options Are Wrong:

Magnesia: Usually minor; excess causes color change and potential durability issues.
Lime: Needed in small amounts; too much causes popping/spalling due to unsoundness.
Alumina: Important for plasticity but typically secondary to silica in proportion.

Common Pitfalls:

Assuming alumina should dominate because it provides plasticity; without sufficient silica, bricks can warp and shrink excessively.

Final Answer:

Silica