---
title: "Define porosity in brief"
subject: "Civil Engineering Materials"
chapter: 1
key: "semester_3/civil_engineering_materials:property-porosity"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/property-porosity
site: BCT Engineering
---

# Define porosity in brief

Civil Engineering Materials · Chapter 1: Introduction to Civil Engineering Material

- Asked in: 2081 Bhadra, 1 marks; 2078 Bhadra, 1 marks; 2068 Chaitra, 1 marks (asked 3 times)
- Video: [Porosity](https://www.youtube.com/watch?v=Vwo9qgnNrc8) — EarthScienceMovies
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/property-porosity
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-1

## Question

Explain briefly the property porosity.

## Short answer

Porosity is the ratio of void volume to total volume, expressed as a percentage. High porosity leads to low density, low strength, high water absorption and poor frost resistance, while dense materials like granite have very low porosity.

## Answer

**Porosity** is the ratio of the volume of voids (pores) in a material to its total volume, usually expressed as a percentage.

$$
n = \frac{V_v}{V}\times 100
$$

A porous material has low density, low strength, high water absorption and low resistance to frost. Brick and stone with high porosity are less durable, while dense materials such as granite have very low porosity.

## Check yourself

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

1. Porosity is the ratio of
   A. mass to volume
   B. volume of voids to total volume
   C. volume of solids to volume of voids
   D. water absorbed to dry mass of voids
   Answer: B. n = Vv / V x 100. (Key point: Definition)

2. A highly porous material has
   A. high strength and low absorption
   B. high density
   C. low strength and high water absorption
   D. high frost resistance
   Answer: C. High porosity gives low density, low strength, high absorption and low frost resistance. (Key point: Effect)

3. Which material has very low porosity?
   A. Soft brick
   B. Porous stone
   C. Dry sponge
   D. Granite
   Answer: D. Dense materials such as granite have very low porosity. (Key point: Example)

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