Average response time: under 24 hours
After stripping self-leveling compound (SLC), grind the slab with soft-bond diamond tooling at light pressure to open the concrete back up. Run two dry passes with a 30/40 grit metal-bond plate, then a fine 60/80 pass, and stop when a water sheen soaks in within 60 seconds. Never skip the moisture test, because SLC traps water under it and the slab can still be wet when it looks dry. Expect to wear diamond plates 20 to 30 percent faster than on bare concrete.
Self-leveling compound is cementitious but much finer and denser than the underlying slab. Once you have chipped, ground, or mechanically removed it, a thin haze of cured SLC dust still seals the surface pores. New epoxy, urethane, or polished concrete cannot bond through this haze, and polishing it will show cloudy patches under sheen. The grind is the step that restores the natural porosity of the slab so the new coating grips instead of sitting on a film.
Plan the tooling change before you start. A PCD scraper got the big SLC chunks up; now the diamond bond must do the fine work. JOY TECH trapezoid holders like the JOY-TP-R3 clip on in seconds and run the correct segment count for a planetary head, so the switch from scraping to grinding costs only a few minutes.
Wet a small patch. If water beads or rolls, SLC haze is still present. If it soaks in unevenly but leaves chalky residue, you have a mix of cured SLC dust and laitance. Hard raised spots where the SLC poured thick must be flagged with chalk, because those take two extra passes. Walk the whole slab once with a flashlight at grazing angle; it catches the cloudy patches that a straight-on look misses.
Test relative humidity with in-situ probes or a plastic sheet taped down for 16 hours. SLC holds water long after it feels dry, and grinding a wet slab glazes diamonds in minutes. Run a pH test on a damp rag held against the slab for a minute: anything above 9 means efflorescence is still leaching, and coating adhesion will fail even if the grind looks perfect. Fix moisture with drying time or a vapor barrier before coating.
Start with a coarse 30/40 grit metal-bond plate on a planetary floor grinder, at 0.05 to 0.1 mm per pass, overlapping lanes by one third. The first pass opens the haze; the second levels the patchy scratch. Follow with 60/80 grit, then stop and wipe the floor with a damp mop. If water darkens the slab evenly within a minute, porosity is back and you are ready for coating.
On hand grinder edges where the floor machine cannot reach, use a double-row cup wheel such as JOY-CW-DR, because the dense SLC haze loads a single row fast. Two rows share the abrasive load and keep cutting twice as long on the same corners.
A planetary floor grinder with three or six heads runs most reliably on SLC residue because the rotating heads overlap and do not leave swirl marks. Set the drum pressure just heavy enough to bite, and raise the machine at lane ends so you do not dig a trench where the operator turns. Keep the water tank off; dry grinding shows the open porosity immediately, and wet grinding hides haze under a slurry film.
Assign one operator to the grinder, one helper on the vacuum and dust bin, and one person on edges with a hand grinder. The helper pre-loads the next set of plates so the swap takes under a minute. This parallel work keeps 90 percent of the shift on actual cutting instead of walking to the truck.
Grinding after SLC removal is a restoration step, not a polish. Open the slab with soft-bond tooling, verify porosity with water and moisture tests, and match tooling wear expectations. Browse metal-bond holders and cup wheels at the grinding tooling category to keep the prep line moving.
Written and reviewed by JOY TECH - an SGS & BV audited, CE/RoHS certified diamond tools manufacturer founded in 2004, exporting to 50+ countries.
Our factory and quality management system are audited by SGS and Bureau Veritas. Products meet CE/RoHS requirements and every piece is 100% inspected before packing.
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