---
title: "Clinker compounds strength-time graph"
subject: "Civil Engineering Materials"
chapter: 5
key: "semester_3/civil_engineering_materials:clinker-strength-graph"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/clinker-strength-graph
site: BCT Engineering
---

# Clinker compounds strength-time graph

Civil Engineering Materials · Chapter 5: Cement

- Asked in: 2075 Asoj, 3 marks
- Video: [Hydration of Cement | Hydration of C3S | Hydration of C2S | Hydration of C3A by Dr K Mohan](https://www.youtube.com/watch?v=tRA-L7_cB_k) — CementPDM by CemNex
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/clinker-strength-graph
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-5

## Question

Sketch out the graph related to the contribution of clinker compounds to strength with respect to time of cement compound.

## Short answer

C3S contributes mainly to early strength up to 28 days. C2S hydrates slowly and is responsible for long-term strength development from 28 days onward, while C3A gives slight early strength and C4AF contributes very little.

## Answer

The four clinker compounds contribute to strength at different rates:

- **C3S** (tricalcium silicate): hydrates fast and is responsible for early strength (up to 7 days); it keeps contributing up to 28 days.
- **C2S** (dicalcium silicate): hydrates slowly, contributes little in the first weeks and is mainly responsible for later strength (from 28 days to a year and beyond).
- **C3A**: reacts rapidly and gives a little strength in the first 1-3 days only.
- **C4AF**: contributes very little to strength.

```text
 Strength
   ^
   |                          ______________ C3S
   |                  ___---''
   |             _--''                ______ C2S
   |          _-'               ___--'
   |        /             ___--'
   |       /        ___--'
   |      /   ___--'
   |     / _-'
   |    /_' ____________________________ C3A
   |  _/.-'_____________________________ C4AF
   +-----+-----+-------+--------+-------> Age
        3d    7d      28d      90d     1 yr
```

Hence the early strength of cement depends on C3S and C3A, and the long-term strength on C2S (together with C3S).

## Check yourself

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

1. Which compound mainly contributes early strength (to about 7-28 days)?
   A. C2S
   B. C3S
   C. C4AF
   D. Gypsum
   Answer: B. C3S hydrates fast. (Key point: Early strength)

2. Strength after 28 days to one year is mainly due to:
   A. C3A
   B. C4AF
   C. C2S
   D. Free lime
   Answer: C. C2S hydrates slowly. (Key point: Later strength)

3. Which pair contributes little to strength?
   A. C3S and C2S
   B. C3S and C3A
   C. C2S and C3S
   D. C3A (only 1-3 days) and C4AF
   Answer: D. C3A gives some early strength; C4AF very little. (Key point: Minor contributors)

## Related in Civil Engineering Materials

- [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×
- [Compressive strength test of cement](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acement-compressive-strength-test) — Civil Engineering Materials, chapter 5, asked 3×

## Related in other subjects

- [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×
- [Grade of cement; Bogue's compounds](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Agrade-of-cement-bogue) — Concrete Technology and Masonry Structure, chapter 1
- [Effect of water cement ratio on strength](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Awc-ratio-effect-strength) — Concrete Technology and Masonry Structure, chapter 3, asked 4×
- [Gel/space ratio and strength (550 gm cement)](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Agel-space-ratio-550g) — Concrete Technology and Masonry Structure, chapter 4, asked 3×