This document specifies the scheme for the assessment and verification of constancy of performance (AVCP) of ground granulated blast furnace slag, including certification of constancy of performance. The document provides technical rules for the factory production control, further testing of samples taken at the manufacturing plant (autocontrol testing) and the assessment of the performance of the ground granulated blast furnace slag, initial inspection of the manufacturing plant and of the factory production control and audit-testing of samples. It also provides rules for actions to be followed in the event of non-conformity and the requirement for depots. This document is linked with the Annex ZA of the European Standard covering ground granulated blast furnace slag, i.e. EN 15167-1:2006.