What is the modulus of elasticity and the typical values for steel and concrete?

• A. E is the density; steel ~7800 kg/m3, concrete ~2400 kg/m3.
• B. E is the yield strength; steel ~500 MPa, concrete ~30 MPa.
• C. E is the slope of the stress-strain curve; ~200 GPa for steel and ~25–30 GPa for concrete.
• D. E is the heat capacity.

Answer: (C)

Modulus of elasticity measures stiffness. It is the slope of the stress–strain curve in the linear elastic region, meaning how much strain results from a given stress before any permanent deformation occurs. In other words, E = stress ÷ strain while the material behaves elastically.

For steel, the slope is very steep, giving about 200 GPa, so steel is very stiff. For concrete, the slope is much gentler, around 25–30 GPa, reflecting a lower stiffness due to its composite, porous nature. The exact values vary with grade, mix, age, moisture, and loading conditions, but these are typical order-of-magnitude values.

Note that E is not the density, yield strength, or heat capacity—those are different properties.