Diamond grinding
Also called: concrete grinding, floor grinding, surface profiling, CSP, concrete surface profile, grinding vs acid etching
Mechanically abrading a concrete slab with diamond-segment discs to remove laitance, sealers and old coatings and open the pores to a sandpaper-like profile (CSP 2–3) that a coating can bond to. $1–$2 per sq ft from a contractor, $120 a day to rent. The prep that decides whether a coating lasts.
Cured concrete has a smooth, weak skin on top — laitance — plus whatever curing compound, sealer, paint or tire residue has landed on it since. A coating applied to that surface bonds to the skin, and the skin lets go. Grinding removes it and leaves a textured, absorbent surface with the profile coatings are designed for. The International Concrete Repair Institute rates profiles from CSP 1 (smooth) to CSP 10 (very rough); thin-film coatings want CSP 2–3, about the texture of medium sandpaper.
The alternative in the box kits is acid etching: a muriatic or citric acid wash that dissolves a little of the surface. It cleans and lightly textures but doesn’t remove sealers or reach a consistent profile, leaves residue that must be neutralized and rinsed, and is the preparation behind most peeling garage floors. Contractors grind; the kits etch because a grinder doesn’t fit in a box.
For a 2-car garage a walk-behind single-head grinder with a dust shroud, a diamond cup wheel and a HEPA vacuum rents for $120–$180 a day, and the job is most of a day: overlapping passes in two directions until the whole slab is uniformly dull, edges with a hand grinder, then vacuum twice. It also removes old coatings, though a thick or well-bonded one takes longer or more aggressive segments. Shot blasting is the commercial alternative for large areas. Whatever the coating on top — 100%-solids epoxy, polyaspartic, or a kit — grinding is the variable that most changes how long it lasts.