Compressive strength test

The mechanical test known as the compressive strength test determines the maximum compressive load that a material can withstand before breaking. A gradually applied load compresses the test item, which often takes the shape of a cube, prism, or cylinder, between the platens of a compression-testing machine.

Despite having high compressive strengths, brittle materials including rock, brick, cast iron, and concrete eventually shatter. Concrete has a crushing strength of roughly 3 tons per square inch, granite has a crushing strength of 10 tons per square inch, and cast iron has a crushing strength ranging from 25 to 60 tons per square inch, which is measured by shattering a cube.

Some ductile metals, like mild steel, have extremely high compressive strengths, although it can be challenging to measure the precise numbers. A ductile metal will initially deform elastically when a load is applied, but at a certain point, plastic deformation will take place. Increased stresses may even fully flatten a test piece without any discernible fracture developing, rendering the compressive strength measurement useless. In these situations, it is customary to quote tensile strength figures, which is incorrect but safe because compressive strength is almost always larger.