---
title: "Aggregate properties and their influence on concrete"
subject: "Concrete Technology and Masonry Structure"
chapter: 1
key: "semester_5/concrete_technology_and_masonry_structure:aggregate-properties-influence"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/aggregate-properties-influence
site: BCT Engineering
---

# Aggregate properties and their influence on concrete

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

- Asked in: 2078 Kartik, 4+4 marks
- Video: [Aggregates and Its Classification - Properties of Concrete - Advanced Concrete Technology](https://www.youtube.com/watch?v=aB096M59Yec) — Ekeeda
- 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-properties-influence
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-1

## Question

Write down the properties of aggregates for concrete. How do the aggregate properties influence the concrete properties?

## Short answer

Key aggregate properties: grading, shape, texture, strength, absorption, soundness, deleterious matter. Grading controls voids and water demand; shape affects workability and bond; strength limits concrete strength; high absorption raises water demand; deleterious matter weakens bond and promotes corrosion; soundness prevents disintegration.

## Answer

#### Properties of aggregates for concrete
Physical: particle size and grading, shape, surface texture, specific gravity, bulk density, porosity, water absorption, moisture content (bulking), voids.
Mechanical: crushing, impact, abrasion value, hardness and strength.
Chemical/other: soundness, alkali-aggregate reactivity, deleterious matter (clay, silt, coal, salts), thermal properties, fineness modulus.

#### Influence on concrete properties
| Aggregate property | Influence |
|---|---|
| **Grading** | Fewer voids, less cement/water, better workability, less segregation, higher strength and density |
| **Maximum size** | Larger size reduces water demand (surface area); too large reduces strength at high grades |
| **Shape** | Rounded: better workability. Angular: better bond and strength. Flaky/elongated: poor workability, low strength and durability |
| **Surface texture** | Rough texture gives better bond (higher flexural strength), smooth gives better workability |
| **Strength (crushing/impact)** | Weak aggregate limits concrete strength, especially at high grades; affects modulus of elasticity |
| **Abrasion / hardness** | Wear resistance of floors and pavements |
| **Specific gravity / bulk density** | Determines weight of concrete (light or heavy concrete) and mix proportioning |
| **Porosity and absorption** | High absorption increases water demand, lowers frost resistance and durability; affects w/c control |
| **Moisture content** | Surface moisture changes w/c; bulking changes volume batching |
| **Soundness** | Unsound aggregate causes disintegration and pop-outs |
| **Deleterious material (clay, silt, organic, chloride)** | Reduces bond, strength, causes corrosion, retards set |
| **Alkali reactivity** | Expansion, map cracking, loss of durability |
| **Thermal properties and elasticity** | Affect shrinkage, creep, thermal cracking |

## Check yourself

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

1. Rough surface texture of aggregate mainly gives:
   A. Better bond and higher flexural strength
   B. Better workability only
   C. Lower strength
   D. Lower density
   Answer: A. Rough texture improves bond; smooth texture improves workability. (Key point: Surface texture)

2. High water absorption of aggregate:
   A. Improves frost resistance
   B. Increases water demand, lowers durability and affects w/c control
   C. Has no effect
   D. Reduces water demand
   Answer: B. Porous aggregate absorbs water and reduces frost resistance and durability. (Key point: Absorption)

3. Specific gravity and bulk density of aggregate determine:
   A. Weight of concrete (light or heavy) and mix proportioning
   B. Setting time
   C. Alkali reactivity
   D. Crushing value
   Answer: A. They fix concrete density and are used in mix proportioning. (Key point: Specific gravity)

4. Weak aggregate chiefly limits:
   A. Strength of concrete, especially at high grades, and modulus of elasticity
   B. Setting time
   C. Colour
   D. Cement hydration
   Answer: A. Aggregate strength limits concrete strength and affects elasticity. (Key point: Weak aggregate)

## Related in Concrete Technology and Masonry Structure

- [Mechanical properties of aggregates](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaggregate-mechanical-properties) — Concrete Technology and Masonry Structure, chapter 1, asked 2×
- [Mechanical properties; ranking aggregate grading](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaggregate-mech-props-rank-grading) — Concrete Technology and Masonry Structure, chapter 1
- [Stress-strain of paste, aggregate, concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Astress-strain-three-phase) — Concrete Technology and Masonry Structure, chapter 4
- [Requirements of aggregates; need of grading](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaggregate-requirements-grading) — Concrete Technology and Masonry Structure, chapter 1
- [Properties of hardened concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Ahardened-concrete-properties) — Concrete Technology and Masonry Structure, chapter 4, asked 3×
- [Physical properties of OPC and concrete behaviour](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Acement-physical-properties) — Concrete Technology and Masonry Structure, chapter 1

## Related in other subjects

- [Desirable properties of road aggregates](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aaggregate-desirable-properties) — Transportation Engineering I, chapter 6, asked 5×
- [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