Concrete and Steel Material Properties

Handout: Download class handout.

Code: See Chapters 3 to 5 for specific ASTM standard material tests, steel material specifications, number of tests conducted in the field, etc.

The rest of the presentation here focuses on the stress-strain properties of hardened concrete and reinforcing steel, both of which are necessary for design.

Concrete

Must be fabricated with components (cement, aggregates, water, admixtures) conforming to sections 3.2, 3.3, and 3.4 in the ACI 318 Building Code.

Uniaxial Stress-Strain Properties

Concrete compresive stress-strain properties are determined using standard cylinder tests (ASTM C 39). The most common cylinder dimensions (in the U.S.) are either 6 in. (diameter) by 12 in. (height), or 4 in. by 8 in. These tests are used primarily to determine the compressive strength of concrete. A standard measure of strength is f 'c, the cylinder strength after 28 days of casting. Other properties, such as modulus of elasticity and Poisson's modulus can also be determined from these tests.

The table below lists typical values of concrete properties:

Property
Notation
Comments/Equation
Units
Typical Values

Compressive Strength

f 'c
28-day compressive strength
psi
3500-15000
Tensile Strength
ft
Tensile strength: determined from split cylinder tests
psi
300-1000
Modulus of Rupture
fr
Determined from beam tests
psi
300-1000
Modulus of Elasticity
Ec
See ACI 318 section 8.5
ksi
Poisson's Ratio
ν
-
-
0.15-0.20

 

 

Steel

Must meet the following specifications(ACI 318 3.5.3): ASTM A 615 (most common), ASTM A 706 (where control of tensile strength is needed, e.g. seismic applications), or ASTM A 996.

Uniaxial Stress-Strain Properties

Stress-strain properties of reinforcing steel are determined following ASTM standard E-. The main properties of importance for design are the yield stress, fy, the yield strain, and the modulus of elasticity. Stress and strain are related through the modulus of elasticity of steel, which is approximately 29000 ksi. The figure below presents a typical stress-strain curve for reinforcing steel.