What is the Tensile Strength of Concrete? Explained in 1-minute.

Thu 26th Jun 2025 by ilyas

Usually many practitioners focus on the compressive capacity of concrete. The tension capacity is usually ignored for design capacity purposes since it is significantly lower AND presents a very brittle failure.

However, the concrete tensile capacity can be useful for analysing crack widths as well as checking the "cracked" moment capacity of the concrete alone (without any steel reinforcement).

As a general approximate rule, the tensile capacity of concrete is usually about 10% of it's compressive strength. For example, a 30 MPa compressive strength concrete will have about a 3 MPa tensile strength.

Various equations from different codes are presented below, applicable to normal weight concrete rather than lightweight concretes. Note that fck is the concrete cylinder compressive strength.

Eurocode

In the Eurocode, the mean tensile strength of concrete is estimated as follows:

f subscript t equals 0.3 cross times f subscript c k end subscript to the power of 2 divided by 3 end exponent

for < 50 MPa strength

ACI

In the American concrete codes, the tensile strength is mostly referred to as the modulus of rupture, and is calculated as:

f subscript t equals 0.62 cross times square root of f subscript c k end subscript end root

Japanese (AIJ)

In the Japanese AIJ standards, the tensile strength of concrete is as follows:

f subscript t equals 0.56 cross times square root of f subscript c k end subscript end root

Cracking Moment

The cracking moment represents the bending moment beyond which the concrete will be cracked, so it's a useful check. In general, it can be calculated as follows:

M subscript c r end subscript equals f subscript t cross times Z

where Z is the section modulus of the concrete (bd^2/6)

Example:

Consider a 600 x 1000 mm RC beam (B x D) using C32/40 grade concrete and with an applied bending moment (ULS) of 250 kN-m.

ft = 0.3*(32)^2/3 = 3.0 N/mm2
Z = 60cm x (100cm)^2 / 6 = 100,000 cm3
Therefore...
Mcr = 3 N/mm2 x (100,000 x 1000) mm3 = 3x10^8 N-mm = 300 kN-m

This is greater than the maximum applied bending moment, therefore the concrete may be considered to be uncracked. Note that this is just an example with a particularly low applied bending moment.

Generally an efficiently designed section will employ steel reinforcement, and the cracked moment will tend to be smaller than the applied bending moments in most practical cases.

Last Update 27/07/25 09:03 JST

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What is the Tensile Strength of Concrete? Explained in 1-minute.

Eurocode

ACI

Japanese (AIJ)

Cracking Moment

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