---
title: "Hardened concrete properties; elastic behaviour"
subject: "Concrete Technology and Masonry Structure"
chapter: 4
key: "semester_5/concrete_technology_and_masonry_structure:hardened-properties-elastic-behaviour"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/hardened-properties-elastic-behaviour
site: BCT Engineering
---

# Hardened concrete properties; elastic behaviour

Concrete Technology and Masonry Structure · Chapter 4: Properties of hardened concrete

- Asked in: 2079 Bhadra, 4 marks
- Video: [1.07 |  Properties of Hardened Concrete](https://www.youtube.com/watch?v=loaiToRn_t8) — MANI MOHAN
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/hardened-properties-elastic-behaviour
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-4

## Question

List out the properties of hardened concrete. Describe the elastic behaviour of hardened concrete.

## Short answer

Hardened concrete properties include strength, elasticity, and durability. The stress-strain behaviour is nonlinear; linear only up to ~30% of f_c. IS 456 gives secant modulus E_c = 5000√f_ck MPa and Poisson’s ratio 0.15–0.20. Modulus is higher with stiffer aggregate, lower w/c, and age; creep reduces effective modulus.

## Answer

#### Properties of hardened concrete
1. Strength: compressive, tensile (direct, splitting, flexural), shear and bond strength.
2. Elastic properties: modulus of elasticity and Poisson's ratio.
3. Dimensional changes: shrinkage, creep and thermal movement.
4. Durability: permeability, resistance to chemicals, freeze-thaw, abrasion and carbonation.
5. Density and unit weight.
6. Fatigue, impact and fire resistance.
7. Water tightness and porosity.

#### Elastic behaviour
Concrete is a heterogeneous material with a curved stress-strain relation, so it is only approximately elastic.

- Linear up to about 30% of $f_c$, then curved because of microcrack growth; peak strain about 0.002, ultimate strain 0.0035 (IS 456, Cl. 38.1).
- On unloading, part of the strain is recovered (elastic) and the rest is permanent.
- Different moduli are defined: initial tangent, tangent, secant, chord and dynamic.
- IS 456 (Cl. 6.2.3.1): $E_c = 5000\sqrt{f_{ck}}$ N/mm$^2$ (secant, short-term). Poisson's ratio is 0.15 to 0.20.
- Stiffer aggregate, higher strength, lower W/C and older age give a higher modulus; creep reduces the effective value in long-term loading ($E_{ce} = E_c/(1+\theta)$, Annex C).

## Check yourself

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

1. The stress-strain curve of concrete is linear up to about:
   A. 100% of f_c
   B. 30% of f_c
   C. 90% of f_c
   D. 5% of f_c
   Answer: B. Beyond that, microcrack growth curves the relation. (Key point: Linear range)

2. IS 456 ultimate compressive strain of concrete is:
   A. 0.0035
   B. 0.0003
   C. 0.035
   D. 0.002
   Answer: A. Peak strain is about 0.002 and ultimate strain is 0.0035. (Key point: Ultimate strain)

3. On unloading concrete from a high stress:
   A. all strain recovers
   B. none recovers
   C. part of strain is recovered and the rest is permanent
   D. strain doubles
   Answer: C. Concrete is only approximately elastic. (Key point: Unloading)

4. Effective modulus considering creep is:
   A. E_c (1 + theta)
   B. E_c x theta
   C. E_c - theta
   D. E_c / (1 + theta)
   Answer: D. Creep reduces the effective modulus in long-term loading. (Key point: Long-term modulus)

## Related in Concrete Technology and Masonry Structure

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