Remove carpet glue and black mastic with PCD tooling for the bulk layer, then coarse metal-bond discs for the residue. PCD scrapes the sticky adhesive without loading up; the metal-bond pass cleans the film down to concrete and opens the surface profile.
Carpet adhesive and black mastic are soft, sticky and gummy. Metal-bond grinding discs clog quickly on mastic because the softened glue packs into the bond. PCD tooling works differently: the polycrystalline diamond tips shear and scrape the adhesive off the concrete, much like they remove epoxy. That is why mastic removal jobs almost always start with PCD.
Pull up the carpet and pad completely. Scrape off any loose adhesive with a floor scraper before grinding — this saves tooling life and speeds the job. For very thick mastic, a scraper or cold planer removes most of the bulk, leaving a thin film for the grinder.
Run a floor grinder with PCD tooling such as Husqvarna 9-PCD discs at low speed with steady pressure. The PCD tips shave the mastic layer off in strips. Keep passes overlapping and check the rotation direction matches your machine. Work the edges with a PCD cup wheel on an angle grinder.
Switch to coarse metal-bond discs (16# or 30/40) to remove the remaining adhesive film and the ridges left by PCD. This pass also opens the concrete profile so a new floor covering bonds properly. Vacuum the residue between passes — sticky dust loads tooling faster.
A>Not efficiently. Metal bond loads and glazes on sticky mastic. Use PCD for the bulk, metal bond for the residue.
A>Only if you grind too deep or tilt the machine. PCD scrapes rather than digs, so a flat machine removes the adhesive with minimal concrete loss.
A>Hard, brittle mastic can be scraped off with PCD and may chip in flakes. Still start with PCD, then clean with coarse metal bond.
A>Only if you plan to leave the concrete exposed. For new flooring, the open profile is ideal for the new adhesive or primer — do not seal.
Carpet glue and mastic come off fastest with a two-stage approach: PCD tooling shaves the bulk, coarse metal bond cleans the residue, and a good vacuum and inspection finish the job. Start with JOY PCD coating-removal discs matched to your grinder and the slab will be clean, open and ready for the next floor.
