---
title: "Harmful ingredients in brick earth"
subject: "Civil Engineering Materials"
chapter: 3
key: "semester_3/civil_engineering_materials:harmful-ingredients-brick-earth"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/harmful-ingredients-brick-earth
site: BCT Engineering
---

# Harmful ingredients in brick earth

Civil Engineering Materials · Chapter 3: Clay Products

- Asked in: 2075 Asoj, 2 marks; 2073 Shrawan, 2 marks; 2071 Chaitra, 2 marks (asked 3 times)
- Video: [Harmful ingredients of bricks |SSC JE  | Civil Engg. | Building Materials, Bricks (Part-2)](https://www.youtube.com/watch?v=kvzn3eI3-Rk) — EXAM GUIDE
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/harmful-ingredients-brick-earth
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-3

## Question

Explain the harmful ingredients of brick earth and their effects on the properties of bricks.

## Short answer

Lime lumps cause cracking, iron pyrites disintegration, alkalies efflorescence and distortion, pebbles and grit weaken, organic matter leaves voids, excess sand makes bricks brittle, and excess iron oxide darkens and fuses bricks.

## Answer

Harmful ingredients in brick earth reduce the quality of the finished brick.

| Ingredient | Harmful effect |
|---|---|
| Lime (excess, as lumps) | Absorbs moisture after burning, slakes and expands, causing the brick to crack and break |
| Iron pyrites | Oxidise and cause the brick to disintegrate |
| Alkalies (soda, potash) | Cause efflorescence and fuse the brick, making it distorted |
| Pebbles, gravel, grit | Prevent uniform mixing and make the brick weak |
| Excess iron oxide | Gives dark blue colour and fusion |
| Vegetation and organic matter | Burns, leaves voids and makes the brick porous and weak |
| Excess sand | Makes the brick brittle |

## Check yourself

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

1. Lumps of lime in brick earth cause cracking because they:
   A. Melt
   B. Burn to ash
   C. Increase plasticity
   D. Absorb moisture after burning, slake and expand
   Answer: D. Slaking expansion cracks the brick. (Key point: Lime lumps)

2. Iron pyrites in brick earth:
   A. Oxidise and cause disintegration
   B. Give red colour
   C. Strengthen the brick
   D. Reduce shrinkage
   Answer: A. Pyrites oxidise and break the brick. (Key point: Iron pyrites)

3. Alkalies (soda, potash) cause:
   A. Increased strength
   B. Efflorescence and fusion giving distortion
   C. Lower absorption
   D. Bright red colour
   Answer: B. They cause white deposits and distortion. (Key point: Alkalies)

## Related in Civil Engineering Materials

- [Harmful ingredients of cement](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aharmful-ingredients-opc) — Civil Engineering Materials, chapter 5, asked 2×
- [Constituents of brick earth and functions](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aconstituents-brick-earth-functions) — Civil Engineering Materials, chapter 3, asked 9×
- [Characteristics of good brick earth](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acharacteristics-good-brick-earth) — Civil Engineering Materials, chapter 3
- [Characteristics of good bricks](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acharacteristics-good-bricks) — Civil Engineering Materials, chapter 3, asked 4×
- [Efflorescence in bricks](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aefflorescence-in-brick) — Civil Engineering Materials, chapter 3, asked 2×
- [Preparation of clay for bricks](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aclay-preparation-for-bricks) — Civil Engineering Materials, chapter 3

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