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Hardened concrete properties; elastic behaviour

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.

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

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 fcf_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): Ec=5000fckE_c = 5000\sqrt{f_{ck}} N/mm2^2 (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 (Ece=Ec/(1+θ)E_{ce} = E_c/(1+\theta), Annex C).

✓ Answer checked by Claude Sonnet 5.5

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