---
title: "Descriptive tests of aggregate"
subject: "Transportation Engineering I"
chapter: 6
key: "semester_6/transportation_engineering_i:aggregate-descriptive-tests"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/aggregate-descriptive-tests
site: BCT Engineering
---

# Descriptive tests of aggregate

Transportation Engineering I · Chapter 6: Highway Materials

- Asked in: 2080 Chaitra, 2 marks
- Video: [All Important Tests on Aggregate🔥 | IS Codes, Purpose & Equipment Explained](https://www.youtube.com/watch?v=82PizJz9t1w) — REINFORCE
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/aggregate-descriptive-tests
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-6

## Question

Discuss descriptive tests of aggregate.

## Short answer

Descriptive tests include flakiness and elongation indices, specific gravity, water absorption, bulk density, surface texture, colour, petrographic examination, gradation, adhesion and cleanliness. They describe physical character rather than strength and are used alongside mechanical tests for aggregate acceptance.

## Answer

Descriptive tests of aggregate are simple (visual or physical) tests that describe the character of the aggregate rather than its strength.

1. **Particle shape tests** - flakiness index, elongation index and angularity number; show the proportion of flat, long and angular particles.
2. **Specific gravity and water absorption** - show the density and porosity of the aggregate.
3. **Bulk density and voids** - used for mix proportioning.
4. **Surface texture** (smooth, rough) and **colour** - indicate the skid resistance and the affinity for bitumen.
5. **Petrographic examination** - rock type and mineral content, including alkali-silica reactive minerals.
6. **Gradation (sieve analysis)** - particle size distribution.
7. **Stripping/adhesion** test and **cleanliness** tests (clay, silt and organic content).

These tests are descriptive in the sense that they give a physical description of the aggregate; they are used together with the strength tests (crushing, impact, abrasion) for acceptance.

## Check yourself

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

1. Descriptive tests of aggregate mainly describe
   A. Only the crushing strength
   B. Physical character such as shape, density and size rather than strength
   C. The bitumen grade
   D. Cement setting time
   Answer: B. They describe the aggregate, and are used along with strength tests. (Key point: Purpose)

2. Which tests give the proportion of flat and long particles?
   A. Los Angeles abrasion
   B. Soundness
   C. Flakiness and elongation index
   D. Aggregate impact
   Answer: C. Shape tests show flat, long and angular particles. (Key point: Shape tests)

3. Which test gives particle size distribution?
   A. Specific gravity
   B. Petrographic examination
   C. Stripping test
   D. Sieve analysis
   Answer: D. Gradation is determined by sieve analysis. (Key point: Gradation)