Prescribed - ready-mixed concrete
British Standard BS 8500-1: has been used by the ready-mixed concrete industry since December 2003 (replacing BS 5328).
Prescribed concrete is a mix for which the purchaser prescribes the exact composition and constituents of the concrete and is responsible for ensuring that these proportions produce a concrete with the required performance. Effectively the purchaser selects the materials and mix proportions to satisfy the required strength and durability needs but does not specify these parameters.
The mix is ordered by its constituent materials and the properties or quantities of those constituents to produce a concrete with the required performance. The assessment of the mix proportions will form an essential part of the conformity (compliance) requirements if the purchaser so requires.