Generally a concrete mix is required to provide a specified strength, the most common measure of concrete strength is the compressive strength determined in either a cube test or a cylinder test. The user can specify whether cube or cylinder strengths are to be used for the mix designs. The process of strength growth is called ‘hardening’ this is often confused with ‘setting’ but setting and hardening are not the same.
Setting is the stiffing of the concrete after it has been placed. A concrete can be ‘set’ in that it is no longer fluid, but it may still be very weak; you may not be able to walk on it, for example. Setting is due to early-stage calcium silicate hydrate formation. The terms ‘initial’ set’ and ‘final set’ are arbitrary definitions of early and later set; there are laboratory producers for determining these using weighted needles penetrating into cement paste.