Grinding and Polishing

Concrete is ground with a concrete grinder fitted with diamond segments — tools with diamond grit set in a metal bond. Coarse stripping of coatings and adhesive uses grit 16–30, levelling uses 40–70, and smoothing and polishing use 100–200 and 400–3000. A hand-held angle grinder only works for patches of a few square metres and edges. Larger floors need a machine paired with a class M or H industrial vacuum, because silica dust is harmful to the lungs.

Choosing a concrete grinder starts with three factors: floor area, substrate hardness and the stage of work. Renovation and rooms up to around 100 m² call for a light single-disc machine; floors above 100–200 m² and polishing call for a planetary machine with 3 counter-rotating satellites. Concrete hardness sets the segment bond — hard for soft concrete, soft for hard concrete — and the stage of work sets the grit, from 16–30 for coarse grinding up to 400–3000 for polishing.

A planetary grinder has a main disc with 3 counter-rotating satellites (smaller plates carrying the segments), giving a flatter floor and the highest output above 100–200 m² and during polishing. A single-disc grinder has one working head — lighter, cheaper and more manoeuvrable, so it suits renovation, rooms up to around 100 m² and edge work. In our range, planetary machines are Husqvarna Construction and Toolsa; single-disc machines are Dr. Schulze and Husqvarna Construction.

Renting a concrete grinder usually costs 100–300 PLN a day plus a deposit and the diamond segments used; buying a professional machine runs from a few thousand to over a dozen thousand złoty, depending on type and power. Renting pays off for a one-off job up to a few hundred square metres, while buying suits companies that finish floors regularly, since the cost pays back after several to a dozen jobs. Consumable segments add to the running cost; current prices are listed on the product pages.

Taking off 2 cm (20 mm) of concrete in a single pass is not possible with a diamond grinder — one pass with a coarse segment of grit 16–30 typically removes 1–3 mm of material. A layer of a dozen or so millimetres up to 20 mm is removed with a concrete milling machine fitted with spinning knives or flails, in several passes of a few millimetres each. A segment grinder is used only at the finishing stage — levelling and smoothing after coarse milling — not for stripping thick allowances in one go.

Grit describes the grain size of the diamond — the lower the number, the coarser the grain and the faster it removes material. Coarse grinding and removing adhesives use grit 16–30, levelling uses 40–70, and smoothing and polishing use 100, 200, 400 and up to 3000. Each following stage roughly doubles the grit, to remove the scratches left by the previous pass. Our range includes segments in grit 30, 50, 70 and 120, among others.

A planetary concrete grinder, fitted with segments and pads of increasing grit from around 100 to 3000, carries out the whole floor-polishing process — from smoothing to a high gloss. A full cycle is usually 6–8 passes with increasing grit, combined with a lithium hardener (an impregnator that penetrates the concrete) that closes the pores and raises abrasion resistance. A single-disc grinder suits mainly the coarse and levelling stages (grit 16–70) — a planetary machine is needed for the final shine.

Working with a concrete grinder requires a full set of diamond segments in increasing grit — from coarse 16–30 up to finishing 100–200 — plus polishing pads of grit 400–3000 for polishing work. A class M or H industrial vacuum rated at least 200–400 m³/h is also essential, because silica dust is harmful to the lungs. Polishing adds a lithium hardener to the list. The full set is available in grinding and polishing accessories.

Grinding hard industrial concrete over large areas needs a planetary grinder rated at 5–11 kW, usually three-phase 400 V, with a working width of 500–800 mm. Hard concrete also needs a segment with a soft bond, which exposes fresh diamond grain faster — otherwise the tool would glaze over and stop cutting. In halls above 1000–2000 m², work runs continuously, paired with an industrial vacuum rated at least 200–400 m³/h.

In small rooms — bathrooms, corridors, garages up to around 100 m² — a light single-disc grinder works well: it reaches edges and corners easily, and fits through a standard door. Large halls above a few hundred square metres need a planetary grinder with a working width of 500–800 mm and 5–11 kW of power, covering a wide strip of floor in one pass. In practice, the two types are combined — the planetary machine handles the main floor area, the single-disc machine finishes off along the walls.