---
title: "Properties of pozzolanic materials"
subject: "Civil Engineering Materials"
chapter: 4
key: "semester_3/civil_engineering_materials:properties-pozzolanic-materials"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/properties-pozzolanic-materials
site: BCT Engineering
---

# Properties of pozzolanic materials

Civil Engineering Materials · Chapter 4: Lime

- Asked in: 2069 Chaitra, 2 marks
- Video: [Supplementary Cementitious Materials Overview](https://www.youtube.com/watch?v=HSePcq93rYs) — ETHZ - Physical Chemistry of Building Materials
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/properties-pozzolanic-materials
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-4

## Question

Enumerate the properties of pozzolanic material.

## Short answer

Pozzolanic materials are rich in reactive silica and alumina, very fine, and harden only with lime and water, forming insoluble compounds that give strength, impermeability, sulphate resistance and high long-term strength.

## Answer

Properties of pozzolanic materials:

1. Rich in reactive silica and alumina (over 70% SiO₂ + Al₂O₃ + Fe₂O₃).
2. Very fine in grain size, often finer than cement; fineness gives more reaction surface.
3. Do not harden by themselves, but react with lime in the presence of water at normal temperature.
4. Form insoluble cementing compounds that give strength and impermeability.
5. Impart hydraulic character to lime and reduce the heat of hydration.
6. Give good resistance to sulphates, chemical attack and alkali–aggregate reaction.
7. Have a slow strength gain, but higher long-term strength.
8. Low specific gravity and low cost.

## Check yourself

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

1. Pozzolana is rich in:
   A. Free lime
   B. Iron only
   C. Reactive silica and alumina
   D. Carbon
   Answer: C. Over 70% SiO2+Al2O3+Fe2O3. (Key point: Composition)

2. Fineness gives:
   A. Less reactivity
   B. Higher weight
   C. Lower cost only
   D. More reaction surface
   Answer: D. Finer than cement often. (Key point: Fineness)

3. Pozzolana has:
   A. Slow strength gain but higher long-term strength
   B. Fast gain
   C. No gain
   D. Loss of strength
   Answer: A. It reacts slowly. (Key point: Strength gain)

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