---
title: "Sphericity of aggregate"
subject: "Concrete Technology and Masonry Structure"
chapter: 1
key: "semester_5/concrete_technology_and_masonry_structure:sphericity-aggregate"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/sphericity-aggregate
site: BCT Engineering
---

# Sphericity of aggregate

Concrete Technology and Masonry Structure · Chapter 1: Introduction to concrete and concrete materials

- Asked in: 2080 Bhadra, 4 marks; 2080 Baisakh, 3 marks (asked 2 times)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/sphericity-aggregate
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-1

## Question

Define sphericity. Give an example and state the effect of particles with higher sphericity value.

## Short answer

Sphericity measures how close a particle is to a sphere (ratio of surface area of a sphere of equal volume to actual surface area). Particles with higher sphericity need less water and paste, give better workability and packing, and produce denser concrete with higher compressive strength, though smooth rounded surfaces may weaken bond.

## Answer

**Sphericity** is the degree to which a particle approaches the shape of a sphere. It is the ratio of the surface area of a sphere having the same volume as the particle to the actual surface area of the particle:

$$
\text{Sphericity} = \frac{\text{surface area of equal-volume sphere}}{\text{actual surface area of particle}}
$$

Its value lies between 0 and 1; a perfect sphere has sphericity = 1. In practice it is also estimated as the ratio of the particle's smallest to largest dimension, or as the ratio of the diameter of the equal-volume sphere to the diameter of the smallest circumscribing sphere.

#### Example
- A rounded river gravel or a cube-shaped crushed stone has a sphericity of about 0.8-0.9.
- A flaky (slab-like) stone or a needle-like elongated particle has a low sphericity of about 0.3-0.5.
- A glass bead or a marble (a sphere) has sphericity = 1.

#### Effect of particles with higher sphericity
- Lower surface area per unit volume, so **less water and paste** are needed.
- **Better workability** and easier compaction; lower tendency to segregate.
- Better packing, so a **denser concrete** with higher compressive strength at the same cement content.
- Less stress concentration and cracking under load, since there are no thin flaky pieces to split.
- Smooth, rounded particles may reduce bond (interlock), so angular but equidimensional particles (high sphericity with rough texture) are best for high strength.

## Check yourself

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

1. Sphericity is the ratio of:
   A. Actual area to sphere area
   B. Surface area of equal-volume sphere to actual particle surface area
   C. Volume of particle to bounding box
   D. Length to thickness
   Answer: B. A perfect sphere gives 1. (Key point: Definition)

2. Sphericity values lie between:
   A. 1 and 10
   B. 0 and 100
   C. 0 and 1
   D. -1 and 1
   Answer: C. 1 is a perfect sphere. (Key point: Value)

3. Which has low sphericity?
   A. Marble
   B. Rounded river gravel
   C. Cubical crushed stone
   D. Flaky or needle-like particle
   Answer: D. Flaky/elongated particles have about 0.3-0.5. (Key point: Example)

4. Higher sphericity gives:
   A. Less paste, better workability and denser concrete
   B. More water demand
   C. Harsher mix
   D. More segregation
   Answer: A. Lower surface area per volume and better packing. (Key point: Effect)

## Related in Concrete Technology and Masonry Structure

- [Aggregate crushing value determination](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaggregate-crushing-value) — Concrete Technology and Masonry Structure, chapter 1
- [Effect of shape and size of aggregate on workability](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaggregate-shape-size-workability) — Concrete Technology and Masonry Structure, chapter 1, asked 2×

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