---
title: "Mechanical properties; ranking aggregate grading"
subject: "Concrete Technology and Masonry Structure"
chapter: 1
key: "semester_5/concrete_technology_and_masonry_structure:aggregate-mech-props-rank-grading"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/aggregate-mech-props-rank-grading
site: BCT Engineering
---

# Mechanical properties; ranking aggregate grading

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

- Asked in: 2073 Shrawan, 4 marks
- Video: [CH2 AGGREGATE | Properties of Coarse aggregate | CONCRETE TECHNOLOGY | SEM3 | CTE | K SCHEME | 31...](https://www.youtube.com/watch?v=ULHPzdNBT3M) — CIVILPOLY
- 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/aggregate-mech-props-rank-grading
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-1

## Question

Define mechanical properties of aggregate. How do you rank the aggregate grading in the lab?

## Short answer

Mechanical properties: crushing, impact, abrasion value and hardness. Grading is ranked by sieve analysis: dry sample, sieve, plot per cent passing curve; compare with IS 383 limits; well-graded if within limits and smooth. Fineness modulus further ranks fineness.

## Answer

**Mechanical properties of aggregate** are those that describe how an aggregate behaves under load, shock and wear. They include:
- **Crushing value** (strength under gradual compression), 
- **Impact value** (toughness under sudden load), 
- **Abrasion value** (resistance to wear, Los Angeles test), 
- **Hardness and toughness** (resistance to scratching, to breaking).
These are tested by IS 2386 Part 4 and they affect the strength and durability of concrete, particularly in pavements and wearing surfaces.

#### Ranking the grading of aggregate in the laboratory
Grading is checked by **sieve analysis** (IS 2386 Part 1):
1. Oven-dry a representative sample (e.g. 5 kg of coarse, 500 g of sand).
2. Sieve through the stack of IS sieves arranged in decreasing size (80, 40, 20, 10, 4.75 mm, 2.36 mm, 1.18 mm, 600, 300, 150 micron) on a mechanical shaker for about 10 min.
3. Weigh the material retained on each sieve; calculate % retained, cumulative % retained and % passing.
4. Plot % passing against sieve size (log scale) to get the **grading curve**.
5. Rank/classify: compare with the limits in IS 383 (Tables 7 and 9): well graded if within limits; classify sand into Zone I-IV; compute the **fineness modulus** (coarser = higher FM) to rank samples from fine to coarse.
The sample whose curve lies inside the limits and is smooth is ranked best; gap-graded or single-size samples rank lower.

## Check yourself

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

1. Which test measures toughness under sudden load?
   A. Crushing value
   B. Impact value
   C. Abrasion value
   D. Sieve analysis
   Answer: B. Impact value measures toughness under sudden load; crushing is gradual load; abrasion is wear. (Key point: Mechanical properties)

2. Abrasion resistance of aggregate is tested by:
   A. Los Angeles test
   B. Vicat apparatus
   C. Slump test
   D. Pycnometer
   Answer: A. The Los Angeles test gives abrasion value. (Key point: Abrasion)

3. Grading is checked in the lab by:
   A. Crushing test
   B. Sieve analysis, plotting % passing against log sieve size
   C. Specific gravity test
   D. Soundness test
   Answer: B. Sieve analysis and the grading curve are used. (Key point: Sieve analysis)

4. Which sample is ranked best?
   A. Gap-graded
   B. Single-size
   C. One whose smooth curve lies inside IS 383 limits
   D. One with a flat curve
   Answer: C. Smooth curve within limits ranks best; gap-graded and single-size rank lower. (Key point: Ranking)

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