Compressive Strength of Cement (Mortar Cubes)

A standard 1:3 cement-sand mortar is mixed at a specified water-cement ratio, cast into 70.6 mm cube moulds, cured in water, and tested to failure in a compression testing machine at 3, 7 and 28 days.

This is the standard way of confirming a cement batch develops the strength grade printed on the bag (e.g. 43 grade, 53 grade under IS 269) before it is approved for structural use.