What is tensile splitting strength?
Tensile splitting strength is the tensile strength of a material such as concrete, determined by splitting a specimen in two under a line load. Concrete can carry a lot of compression but little tension. In unreinforced concrete, tensile strength still matters, for example in concrete paving blocks: under a wheel they bend very slightly, creating tensile stresses that the concrete itself has to resist.
How does the test work?
A cylinder (or cube or prism) is placed between two platens, with thin packing strips (usually hardboard) in between. The load acts along two opposite lines. This produces an almost uniform tensile stress in the plane between those lines, and the specimen splits down the middle. The test is set out in EN 12390-6 (Testing hardened concrete – Part 6: Tensile splitting strength of test specimens). The load is increased at a stress rate of 0.04 to 0.06 MPa per second.
The tensile splitting strength is calculated as:
f = 2F / (π · L · d)
- f = tensile splitting strength [N/mm²]
- F = maximum load at failure [N]
- L = length of the line of contact with the platens [mm]
- d = diameter or thickness of the specimen [mm]
Application
- Concrete paving blocks. EN 1338 requires a characteristic tensile splitting strength of at least 3.6 MPa. The test follows the same principle, with a correction factor for block thickness.
- Converting to axial tensile strength. Eurocode 2 (EN 1992-1-1) takes the axial tensile strength as 0.9 times the tensile splitting strength.
- Only compare like with like. Splitting, flexural and axial tensile strength give different values for the same concrete.
- State the specimen shape. Cylinders are the reference method; for other shapes, always state which specimen was used.
Common mistake: using the tensile splitting strength directly as a design value for tension. It must be converted first and is higher than the axial tensile strength.
Related terms
- Compressive strength
- Cube compressive strength
- Flexural strength
- Unreinforced concrete
- Concrete strength class
- Concrete paver
- Eurocode
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