---
title: "Concrete ingredients; concrete versus steel"
subject: "Concrete Technology and Masonry Structure"
chapter: 1
key: "semester_5/concrete_technology_and_masonry_structure:concrete-ingredients-vs-steel"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/concrete-ingredients-vs-steel
site: BCT Engineering
---

# Concrete ingredients; concrete versus steel

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

- Asked in: 2071 Chaitra, 6 marks
- Video: [Introduction Of Concrete Technology](https://www.youtube.com/watch?v=VI21Ec8wkYM) — Civil Engineer
- 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/concrete-ingredients-vs-steel
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-1

## Question

Explain concrete ingredients and concrete as a structural material over steel.

## Short answer

Concrete contains cement, fine and coarse aggregates, water, and optional admixtures. Compared to steel, concrete is cheaper, fire-resistant, needs little maintenance, can be cast to any shape, has good compressive strength, and bonds well with steel owing to similar thermal expansion coefficients.

## Answer

#### Concrete ingredients
- **Cement**: the binder (OPC, PPC), which reacts with water.
- **Fine aggregate**: sand (below 4.75 mm); fills the voids between the coarse particles.
- **Coarse aggregate**: crushed stone or gravel (above 4.75 mm, usually 10-40 mm); forms the bulk and the strength skeleton. Fine and coarse aggregates together make up about 70-75% of the volume of concrete.
- **Water**: for hydration and workability (clean, potable; IS 456 cl. 5.4).
- **Admixtures** (optional): plasticisers, retarders, air-entraining agents, fly ash, silica fume.

Typical mix: M20 is 1:1.5:3 by volume, with w/c about 0.5.

#### Concrete as a structural material over steel
- Cheaper and made from local materials; steel is costlier and often imported.
- Fire-resistant, whereas steel loses strength rapidly at 400-500 °C.
- Needs little maintenance and no painting (steel needs repeated corrosion protection).
- Can be cast to any shape and gives monolithic, rigid structures.
- Good compressive strength, mass for stability, and good sound and thermal insulation.
- Works well with steel: concrete resists compression, steel resists tension, and they have nearly equal thermal expansion ($\approx 10-12 \times 10^{-6}$/°C).

Limitations: heavy self-weight, low tensile strength, slow construction and cracking; steel is better for very long spans and for faster erection.

## Check yourself

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

1. Coarse aggregate forms about:
   A. 10% of volume
   B. Only binder
   C. 70-75% of volume as strength skeleton
   D. 30% of volume
   Answer: C. It forms the bulk. (Key point: Coarse aggregate)

2. Compared with concrete, steel:
   A. Resists fire better
   B. Is cheaper
   C. Needs no protection
   D. Loses strength rapidly at 400-500 °C
   Answer: D. Concrete has good fire resistance. (Key point: Fire)

3. Concrete and steel work together partly because:
   A. They have nearly equal thermal expansion
   B. Steel carries compression
   C. Concrete is ductile
   D. Steel is alkaline
   Answer: A. Both are about 10-12 x 10^-6 per °C. (Key point: Thermal expansion)

4. Steel is preferred over concrete for:
   A. Foundations
   B. Long spans and faster erection
   C. Dams
   D. Low rise buildings
   Answer: B. Concrete's self-weight and slow construction limit it. (Key point: Limitation)

## Related in Concrete Technology and Masonry Structure

- [Concrete as a structural material](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aconcrete-structural-material) — Concrete Technology and Masonry Structure, chapter 1, asked 3×
- [Ingredients of olden and modern concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aolden-modern-concrete) — Concrete Technology and Masonry Structure, chapter 1
- [Basic ingredients of concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aconcrete-basic-ingredients) — Concrete Technology and Masonry Structure, chapter 1
- [Structural concrete and its types](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Astructural-concrete-types) — Concrete Technology and Masonry Structure, chapter 1
- [Rationale for reinforcing concrete with steel](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Arationale-steel-reinforcement) — Concrete Technology and Masonry Structure, chapter 1
- [Bond between steel and concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Abond-steel-concrete) — Concrete Technology and Masonry Structure, chapter 5

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- [Structural steel and its classification](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Astructural-steel-classification) — Design of Steel and Timber Structure, chapter 1
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- [Reinforced concrete column stresses in steel and concrete](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Arc-column-8-bars) — Strength of Materials, chapter 3