The strength of concrete can vary depending on how it is tested. Two common testing methods are using a cube and a cylinder. Here's a simple explanation:
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Cube Strength:
- A cube is usually tested with dimensions of 150 mm x 150 mm x 150 mm.
- The strength measured is called the cube compressive strength.
- In general, cube strength is higher than cylinder strength because of the difference in shape and stress distribution during the test.
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Cylinder Strength:
- A cylinder is commonly tested with dimensions of 150 mm diameter and 300 mm height.
- The strength measured is the cylinder compressive strength.
- Cylinder strength is typically about 80% of the cube strength for the same concrete mix. For example, if the cube strength is 30 MPa, the cylinder strength might be around 24 MPa.
Why is there a difference?
- The shape and aspect ratio of the sample affect how stress is distributed during testing.
- Cylinders have more uniform stress distribution, leading to lower measured strength.
- Cubes have confinement effects on the edges, which can give a higher strength reading.
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