---
title: "Characteristics of good brick earth"
subject: "Civil Engineering Materials"
chapter: 3
key: "semester_3/civil_engineering_materials:characteristics-good-brick-earth"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/characteristics-good-brick-earth
site: BCT Engineering
---

# Characteristics of good brick earth

Civil Engineering Materials · Chapter 3: Clay Products

- Asked in: 2068 Chaitra, 3 marks
- Video: [Characteristics of good clay bricks](https://www.youtube.com/watch?v=YOapzGGsTsc) — Mounika Ganta
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/characteristics-good-brick-earth
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-3

## Question

Write the characteristics of good brick earth.

## Short answer

Good brick earth must be plastic, with proper composition (silica 50-60%, alumina 20-30%, lime 5-10%, iron oxide 5-6%), free from harmful impurities like lime lumps and organic matter, and exhibit low shrinkage, good binding power, and proper fusibility without melting.

## Answer

Good brick earth should have the following characteristics.

1. **Plasticity:** when mixed with water it should be workable and hold its shape on moulding. Alumina provides this.
2. **Proper composition:** silica 50-60%, alumina 20-30%, lime 5-10%, iron oxide 5-6% and magnesia below 1%.
3. **Free from harmful substances:** no lumps of lime, pebbles, iron pyrites, gravel, organic matter or excess alkalies.
4. **Low shrinkage:** should not warp, crack or shrink excessively on drying and burning.
5. **Uniform fineness:** fine-grained, with a balanced sand to clay ratio.
6. **Binding power:** strength after drying so that the green brick can be handled.
7. **Good fusibility:** it should fuse slightly (but not melt) at burning temperature to give a hard and strong brick.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which constituent gives plasticity?
   A. Alumina
   B. Silica
   C. Lime
   D. Magnesia
   Answer: A. Alumina gives the workability to hold shape. (Key point: Plasticity)

2. Good brick earth should:
   A. Melt completely
   B. Fuse slightly but not melt at burning temperature
   C. Not fuse at all
   D. Burn to powder
   Answer: B. Slight fusion binds particles. (Key point: Fusibility)

3. Brick earth must be free from:
   A. Silica
   B. Alumina
   C. Lumps of lime, pebbles, pyrites and organic matter
   D. Clay
   Answer: C. These cause cracks and weakness. (Key point: Harmful substances)

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