---
title: "Grade of cement; Bogue's compounds"
subject: "Concrete Technology and Masonry Structure"
chapter: 1
key: "semester_5/concrete_technology_and_masonry_structure:grade-of-cement-bogue"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/grade-of-cement-bogue
site: BCT Engineering
---

# Grade of cement; Bogue's compounds

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

- Asked in: 2072 Chaitra, 4 marks
- Video: [Bogues Compounds - Properties of Concrete - Advanced Concrete Technology](https://www.youtube.com/watch?v=3TbMZp6ToWI) — 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/grade-of-cement-bogue
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-1

## Question

Define grade of cement. Explain the role of Bogue's compound of cement.

## Short answer

G rade is the minimum 28-day compressive strength of 1:3 cement-sand mortar cubes in MPa. B ogue's compounds: C3S gives early strength, C2S later strength, C3A causes flash set and low sulphate resistance, C4AF acts as flux and imparts color.

## Answer

**Grade of cement** is the minimum compressive strength, in MPa (N/mm$^2$), of 70.6 mm mortar cubes (1:3 cement : standard sand, w/c = (P/4 + 3.0)%) at **28 days**, tested as per IS 4031 (Part 6). For example, in IS 269:2015, OPC 33 grade means a minimum 28-day strength of 33 MPa, OPC 43 gives 43 MPa and OPC 53 gives 53 MPa. Higher grades are finer and have more C$_3$S, giving higher early strength.

#### Role of Bogue's compounds
| Compound | Role |
|---|---|
| C$_3$S (alite, 40-55%) | Rapid hydration; gives early strength (7 days) and also strength at 28 days; high heat |
| C$_2$S (belite, 20-30%) | Slow hydration; provides later strength (after 28 days); low heat, good chemical resistance |
| C$_3$A (8-12%) | Reacts at once (flash set, controlled by gypsum); little strength; high heat; poor sulphate resistance |
| C$_4$AF (8-12%) | Little effect on strength; acts as a flux in the kiln and gives colour; slightly sulphate resistant |

C$_3$S and C$_2$S together make about 70-75 per cent of cement and provide the strength through C-S-H gel; C$_3$A and C$_4$AF mainly influence setting, heat and durability. More C$_3$S gives rapid-hardening cement, more C$_2$S gives low-heat cement, and low C$_3$A gives sulphate-resisting cement.

## Check yourself

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

1. Grade of cement is:
   A. Fineness
   B. Setting time
   C. Weight of bag
   D. Minimum 28-day compressive strength of mortar cubes in MPa
   Answer: D. E.g. OPC 43 gives 43 MPa. (Key point: Grade)

2. More C3S gives:
   A. Rapid-hardening cement
   B. Low-heat cement
   C. Sulphate-resisting cement
   D. Slow strength
   Answer: A. C3S gives early strength. (Key point: C3S)

3. More C2S gives:
   A. Rapid hardening
   B. Low-heat cement
   C. Flash set
   D. High heat
   Answer: B. C2S is slow with low heat. (Key point: C2S)

4. Low C3A gives:
   A. Rapid hardening
   B. High heat
   C. Sulphate-resisting cement
   D. Flash set
   Answer: C. C3A is the compound attacked by sulphates. (Key point: C3A)

## Related in Concrete Technology and Masonry Structure

- [Bogue's compounds and their role](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Abogue-compounds-role) — Concrete Technology and Masonry Structure, chapter 1, asked 7×
- [Hydration of cement and role of compounds](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Ahydration-compounds-strength) — Concrete Technology and Masonry Structure, chapter 1, asked 3×

## Related in other subjects

- [Meaning of grade 43 cement](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Agrade-43-cement) — Civil Engineering Materials, chapter 5
- [Clinker compounds and their functions](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acement-clinker-compounds-functions) — Civil Engineering Materials, chapter 5, asked 9×
- [Clinker compounds strength-time graph](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aclinker-strength-graph) — Civil Engineering Materials, chapter 5