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

# Hardness test of aggregate

Transportation Engineering I · Chapter 6: Highway Materials

- Asked in: 2080 Chaitra, 6 marks; 2079 Ashwin, 4 marks (asked 2 times)
- Video: [L-73 Hardness Test on Aggregate – Important for GATE, ESE, SSC JE, RRB JE, PSUs #buildingmaterials](https://www.youtube.com/watch?v=oiv9SK4nkDo) — Civil Site Plus
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/hardness-test
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-6

## Question

Describe the laboratory procedure for determining hardness of aggregate with a neat sketch and mention its significance.

## Short answer

Hardness is resistance to wear measured by Los Angeles abrasion test. Procedure: place 5-10kg oven-dried aggregate with specified steel balls in a rotating cylinder (30-33 rpm, 500-1000 revolutions), sieve on 1.7mm, calculate loss percentage. LAAV = (W1-W2)/W1 × 100%. Values ≤30% for wearing course, ≤35-40% for base, ≤50% for lower layers. Indicates aggregate durability under traffic.

## Answer

**Hardness** of aggregate is its resistance to wear (abrasion and attrition) caused by the rubbing action of vehicle wheels and by the movement of the particles themselves. It is measured by the **Los Angeles abrasion test** (IS:2386 Part IV; ASTM C131), and also by the Deval abrasion test.

#### Los Angeles abrasion test - apparatus
- Los Angeles machine: hollow steel cylinder 700 mm diameter and 500 mm long, closed at both ends, with a shelf fixed inside, rotating about the horizontal axis.
- Abrasive charge of steel balls (about 48 mm diameter, 390-445 g each; 6 to 12 balls).
- IS sieve of 1.7 mm and a balance.

```text
        axis (30-33 rpm)
     .-----------------.
    /   o o  <- balls    \
   |  aggregate  | shelf  |
    \               ____ /
     '-----------------'
         cylinder 700 x 500 mm
```

#### Procedure
1. Take oven-dried aggregate of 5 kg or 10 kg, according to the grading (A to G).
2. Place it with the specified number of balls in the cylinder; close the cover.
3. Rotate at **30 to 33 rpm** for 500 revolutions (gradings A-D) or 1000 (E-G).
4. Remove the material, separate the steel balls, and sieve on a **1.7 mm IS sieve**; wash and oven-dry the retained portion and weigh it.

$$
\text{LAAV} = \frac{W_1 - W_2}{W_1}\times 100\%
$$

where $W_1$ = original weight and $W_2$ = weight retained on 1.7 mm sieve.

#### Significance
- It indicates the ability of the aggregate to withstand the wear from traffic, and the crushing and impact in rolling.
- Good aggregate has a low value: **below 30% for the wearing course**, up to 35-40% for the base, 50% for the lower layers (IRC/NRS 2070). A value below 20% is considered hard.
- It is a simple, reliable test used in aggregate source selection.

## Check yourself

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

1. Which test is used to measure hardness of aggregate?
   A. Aggregate impact test
   B. Soundness test with sodium sulphate
   C. Flakiness index test
   D. Los Angeles abrasion test
   Answer: D. Hardness is resistance to wear, measured by Los Angeles or Deval abrasion. (Key point: Hardness meaning)

2. How is the aggregate abraded in the Los Angeles machine?
   A. Rotated with steel balls at 30-33 rpm for 500 or 1000 revolutions
   B. Struck by a 14 kg hammer 15 times
   C. Compressed with 40 t load
   D. Soaked in sulphate solution for 5 cycles
   Answer: A. The cylinder with the steel ball charge rotates at 30-33 rpm. (Key point: Procedure)

3. What is the Los Angeles abrasion value?
   A. Percentage retained on the 1.7 mm sieve
   B. Percentage of original weight that passes the 1.7 mm sieve after the test
   C. Percentage passing 2.36 mm after 15 blows
   D. Percentage of flat particles
   Answer: B. LAAV = (W1 - W2)/W1 x 100, where W2 is the weight retained on 1.7 mm. (Key point: Calculation)

4. What value is acceptable for aggregate in a wearing course?
   A. Above 50%; higher means harder
   B. Exactly 100%
   C. Below about 30%; lower value means better aggregate
   D. Above 35% only
   Answer: C. Good aggregates have a low abrasion value, below 30% for wearing course. (Key point: Significance)

## Close variants set in other exams

- [Soundness test of aggregate](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aaggregate-soundness-test) — Transportation Engineering I, chapter 6, asked 3×

## Related in Transportation Engineering I

- [Aggregate crushing value test](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Acrushing-value) — Transportation Engineering I, chapter 6, asked 7×
- [Hardness, toughness and aggregate blend](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahardness-toughness-blend) — Transportation Engineering I, chapter 6
- [Aggregate impact value test](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aimpact-value) — Transportation Engineering I, chapter 6, asked 3×
- [Marshall stability test procedure](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Amarshall-stability-test) — Transportation Engineering I, chapter 6, asked 3×
- [Penetration test of bitumen](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Apenetration-test) — Transportation Engineering I, chapter 6, asked 6×
- [Los Angeles abrasion test](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ala-abrasion) — Transportation Engineering I, chapter 6, asked 10×

## Related in other subjects

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- [Soundness test of cement and procedure](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acement-soundness-test-procedure) — Civil Engineering Materials, chapter 5
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- [Workability and slump test procedure](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aslump-test-procedure) — Concrete Technology and Masonry Structure, chapter 3