Compressive Strength of Concrete Cubes

Cubes are cast from fresh concrete sampled at the point of placement, cured under standard conditions, and tested to failure in a compression testing machine — typically at 7 days (an early indicator) and 28 days (the design reference age).

Results are assessed against the acceptance criteria in IS 456 for the specified grade of concrete, based on the individual test results and their variation from the target mean strength. This is the primary quality-control record for structural concrete on a project.