Cementina Metal Bond Discs Another option for grinding hard concrete is using the Cementina metal bond discs. For soft concrete/terrazzo grinding, we recommend the special Cementina terrazzo bond. Cementina grinding discs are best suited for lightweight machines, such as LAVINA® 16 and LAVINA® 20-S, which have a relative grinding pressure of 2 to 6 lbs per square inch. Cementina achieves a very smooth and uniform finish, preparing the floor for resin polishing steps, if desired. Recommended for wet applications only.