---
title: "Bond between steel and concrete"
subject: "Concrete Technology and Masonry Structure"
chapter: 5
key: "semester_5/concrete_technology_and_masonry_structure:bond-steel-concrete"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/bond-steel-concrete
site: BCT Engineering
---

# Bond between steel and concrete

Concrete Technology and Masonry Structure · Chapter 5: Testing of concrete and quality control

- Asked in: 2065 Shrawan (old course), 2 marks
- Video: [Concept and Expression of Bond as per IS:456-2000 | Concrete Structures - GATE](https://www.youtube.com/watch?v=nDTjE0WGAtI) — Ekeeda GATE & ESE
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/bond-steel-concrete
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-5

## Question

Write a short note on bond between steel and concrete.

## Short answer

Bond is the grip that allows stress transfer between steel and concrete, arising from chemical adhesion, friction, and mechanical interlock of bar ribs. Design bond stress for M20 plain bars is 1.2 N/mm², increased 60% for deformed bars. Development length L_d = φσ_s/(4τ_bd) ensures anchorage.

## Answer

**Bond** between steel and concrete is the grip which allows stress transfer from concrete to the reinforcing bar, so that the two act together in a member. It has three parts: **chemical adhesion** of cement paste to steel, **friction** caused by shrinkage-induced gripping, and **mechanical interlock** between ribs of deformed bars and concrete (the biggest contribution).

The bond stress is $\tau_b = \dfrac{T}{\pi \phi L}$, and the design bond stress for M20 is 1.2 N/mm$^2$ for plain bars (IS 456, Cl. 26.2.1.1), 60% more for deformed bars. The development length $L_d = \phi\sigma_s/(4\tau_{bd})$ provides the required anchorage. Bond is better with higher $f_{ck}$, deformed bars, adequate cover, and well-compacted concrete; it is reduced by oil, loose rust and by bleeding under horizontal top bars. It is tested by the pull-out test.

## Check yourself

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

1. Which is the biggest contribution to bond in deformed bars?
   A. Chemical adhesion
   B. Friction
   C. Mechanical interlock
   D. Gravity
   Answer: C. Rib interlock is the largest part. (Key point: Parts of bond)

2. What reduces bond?
   A. Deformed ribs
   B. Good cover
   C. Good compaction
   D. Oil, loose rust and bleeding below top bars
   Answer: D. Contaminants and bleeding weaken the grip. (Key point: Reducers)

3. Which test is used for bond?
   A. Pull-out test
   B. Split test
   C. Rebound test
   D. Slump test
   Answer: A. Bond is tested by pulling out a bar. (Key point: Test)

## Related in Concrete Technology and Masonry Structure

- [Concrete ingredients; concrete versus steel](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aconcrete-ingredients-vs-steel) — 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
- [Use of masonry; types of brick bond](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Amasonry-uses-bond-types) — Concrete Technology and Masonry Structure, chapter 7, asked 2×
- [English and Flemish bond](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aenglish-flemish-bond) — Concrete Technology and Masonry Structure, chapter 7, asked 2×
- [Plan and elevation of English bond wall](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aenglish-bond-plan-elevation) — Concrete Technology and Masonry Structure, chapter 7, asked 2×
- [Shear strength and bond strength](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Ashear-bond-strength) — Concrete Technology and Masonry Structure, chapter 5

## Related in other subjects

- [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
- [RCC column with footing: concrete and steel](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Arcc-column-footing-h) — Estimating and Costing, chapter 6
- [Gravity dam concrete volume from hydrostatic thrust](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Agravity-dam-width-hydrostatic-thrust) — Hydropower Engineering, chapter 4
- [WSM steel area and resistance, M15](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Awsm-steel-area-and-resistance-m15) — Design of RCC Structure, chapter 2