BeginnerTopic 13 of 112Civil & Structural
Compressive strength testing
Cubes or cylinders tested at 28 days define grade.
In depth
Standard 150 mm cubes or 150×300 mm cylinders are cured 28 days and crushed in a compression testing machine. Characteristic strength f_ck is the value below which no more than 5% of results fall. Non-destructive tests: rebound hammer, ultrasonic pulse velocity, core tests.
Key points
- Cube vs cylinder ratio ≈1.25
- Acceptance criteria
- Early-age testing at 7 days
ExampleGrade M30 means 30 MPa characteristic cube strength.
What is Compressive strength testing?
Cubes or cylinders tested at 28 days define grade.
Why is it important to understand compressive strength testing?
Compressive strength tests confirm that concrete meets the specified grade, which is needed for acceptance on site and for the design check.
What is the characteristic strength?
The strength below which only a small percentage of test results, usually five percent, are expected to fall.
Why are cubes tested at 28 days?
Twenty-eight days is the standard age at which the design strength is specified, although tests may be taken earlier for early checks.
How is Compressive strength testing used in practice?
Typical applications include sampling and testing cubes for each pour during a building project, checking that a delivered concrete meets its specified 28-day strength and testing a core from an existing wall to assess its strength.
What should I learn before Compressive strength testing?
Study "Curing of concrete" first (topic 12 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of Compressive strength testing?
Cube vs cylinder ratio ≈1.25. Acceptance criteria. Early-age testing at 7 days.
Can you give an example of Compressive strength testing?
Grade M30 means 30 MPa characteristic cube strength.
What comes after Compressive strength testing?
The next topic is "Reinforced concrete concept", which builds directly on this one.
How difficult is Compressive strength testing?
It is classed as Beginner in Civil & Structural (topic 13 of 112). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.