Tensile Strength and Flexural Strength

There is a general correlation between the tensile strength and the flexural strength of concrete. This correlation varies depending on the precise concrete mix design and for this reason it is recommended that where these parameters are critical to the design a specific relationship should be established through strength testing. In many cases however the below general relationship is adequate, particularly for preliminary design or where the estimate parameter is not critical to the design.

The CivilWeb Tensile Strength of Concrete spreadsheet includes the general relationship equation shown below between tensile strength and flexural strength. The spreadsheet suite also includes a tensile strength maturity relationship described in our Tensile Strength of Concrete post. The Tensile Strength of Concrete spreadsheet can be purchased for just £5 at the bottom of this page. Alternatively the CivilWeb Concrete Properties Suite of spreadsheets includes all our tensile, compressive and flexural strength spreadsheets for only £10.

Correlation between Tensile Strength and Flexural Strength

The indirect tensile or splitting tensile strength of the concrete can be determined from cores taken from the concrete and is seen as a much simpler and more reliable test than the flexural strength test. A correlation between the indirect tensile strength and the flexural strength of the concrete is included below relating the 28 day strengths for concrete mixes including angular crushed aggregates. This correlation is included in the CivilWeb Tensile Strength of Concrete spreadsheet.

f_cf = 28 day flexural strength (MPa)

f_cs = 28 day indirect tensile strength (MPa)

This correlation is a typical one only. Where indirect tensile strength is to be used as an indirect measure of the concrete flexural strength for quality control purposes a correlation specific to the concrete mix used should be developed from testing.