Curing Compound Before Epoxy, Tile, Polish or Densifier

If the slab was sprayed, the coating, tile or polishing sub will want that film gone. Every maker document below says so. The job is to know what profile and moisture numbers the finish needs, test for them, and price the grinding before anyone is surprised. The wider background is on the curing compound and flooring page.

Can you put epoxy over curing compound?

Not as a plan. Euclid’s coatings guide says the slab must be “free of grease, oil, curing compounds, soil, dust and other contaminants” and “roughened and made absorptive, preferably by mechanical means” (Euclid Chemical). A film of cured resin gives the epoxy nothing to bite into.

The garage-kit makers say the same thing in plainer words. Griot’s Garage wants concrete “free of wax, loose paint or curing compounds” and profiled to ICRI 2 (Griot’s Garage). Sika’s CTM kit guide warns that a smooth, poorly prepared slab keeps the epoxy from penetrating and “may result in peeling” (Sika Canada).

Even a curing product made by a coating company is not a free pass. GacoPoly E5691 is an epoxy primer that “meets ASTM C309 requirements for use as a concrete curing compound,” yet Gaco says “testing is ongoing to determine compatibility with GacoPoly coating systems when E5691 is used as a concrete curing agent” (Gaco).

What does each floor finish need from the slab?

Each finish has its own profile, age and moisture rules, but all of them want bare, open concrete. The table pulls the numbers from each maker’s published prep section. Use the maker sheet for the exact product you are installing; these are examples, not substitutes.

CSP numbers come from the ICRI scale, which runs from “CSP 1 (nearly flat) to CSP 10 (very rough)” (DeFelsko). A troweled slab with a film on it sits at the flat end of that scale. The coatings in the table want CSP 2 or rougher, which takes a grind or shot blast.

Euclid also sets a bond floor: an ASTM C1583 pull-off of “at least 250 psi (1.7 MPa)” on the prepared surface. Its moisture limit of 3 lb/1,000 ft²/24 h works out to about 14.6 g/m² per 24 hours.

Does tile or self-leveler bond to concrete with curing compound?

No, not reliably, and the tile standards say so directly. Custom Building Products quotes ANSI A108.02 4.1.1: “Concrete surfaces shall be free of from oil, curing compounds, laitance and cracks.” A108.01 goes further and says to cure the slab “without using liquid curing compounds or other coatings” (Custom Building Products).

LATICRETE explains why. Permanent compounds “fill the pores of the concrete, preventing the development of a mechanical bond,” so you scarify “to a depth below the penetration of the curing compound” (LATICRETE). It also says hardened surfaces are not suitable for direct adhesive tile.

MAPEI’s 2024 bulletin is just as blunt: slabs treated with topical curing agents “necessitate mechanical abrasion for complete removal,” then you verify porosity with a water drop test per ASTM F3191 (MAPEI). ARDEX lists treated concrete for test areas only and says sanding “is not an effective method” (ARDEX).

Can you polish or densify a slab that had curing compound?

Yes, but the compound has to come off first, and it will fight your diamonds on the way. Citadel wants new concrete cured “a minimum of 7 days” and “free of grease, oils, dust, curing compounds and other coatings” before its densifier goes on (Citadel).

Sherwin-Williams says the same for its H&C densifier: “Curing agents, clear sealers and any previous surface coating should be chemically or mechanically removed” (Sherwin-Williams). On exterior work it tells you to confirm the slab was never sealed with a curing compound.

Don’t count on a densifier to cure the slab either. Dayton Superior says densifiers are not membrane forming, so they cannot meet the C309 curing membrane requirement (Dayton Superior). Dayton also notes that its siliconate Sure Hard J17 “will not accept most any floor finish i.e. mastic or epoxy,” so check the densifier sheet if a coating might follow.

On a 60,000 ft² polished floor, Concrete Decor reports a heavy coat of dissipating cure in shaded areas loaded the diamonds and left scratch rows. The fix was to strip chemically or grind wet: a wet 40 grit “will cut like a 25,” followed by a dry 40 (Concrete Decor).

The same article suggests that under a roof, the compound may not be needed at all. If it is sprayed, it says to check the application rate and build the removal into the polisher’s bid.

How do you test the slab before epoxy, tile or polish?

Run three checks before you bid the prep, and run them again after the grind. The methods below come from the maker documents on this page; the step-by-step version is on how to test for curing compound.

1. Water drop test. Drop water on the slab in several spots. If it beads or sits, the surface is sealed. CBP says “If the water beads up, the surface must first be properly prepared,” and MAPEI and ARDEX point to ASTM F3191.
2. Moisture test. Euclid lists ASTM F2170 (in-slab RH) or F1869 (calcium chloride). The Sika kit allows an 18 x 18 in (45 x 45 cm) plastic sheet taped down for 24 hours; darkening or condensation means too much moisture.
3. Mockup or pull test. Euclid recommends a test section to confirm adhesion. CBP has you cure a tile mockup 7 to 28 days before pulling it, and notes “it may be more cost effective to shot blast” than to wait.

How do you get curing compound off before the finish goes down?

Grind it or shot blast it. CBP recommends mechanical abrasion before primers, membranes or cement products, and adds “This includes the removal of dissipating curing compounds.” LATICRETE lists shot blasting, bead blasting, high pressure water blasting and abrasive blasting. Methods and costs are covered on remove curing compound.

Skip acid and solvents for tile and underlayment. LATICRETE says acid removal “is not recommended,” and ARDEX calls acid etching, adhesive removers and solvents “bond breakers.” Euclid allows acid etching under coatings only if you neutralize it with water and baking soda or water and ammonia, and it still prefers mechanical prep.

Does a dissipating or cure and seal product change the answer?

A dissipating product shortens the odds of trouble but does not remove the prep step. LATICRETE says relying on breakdown “is not a reliable method unless the concrete is exposed to direct sunlight for an extended period,” and that dissipating products “may leave a residual film that must be completely removed.”

A cure and seal is worse news for the floor. It is built to stay on as a film. Products tested to ASTM C1315 include a tile adhesive bond test, but that test does not prove your specific coating or thinset will bond. Get the compound maker’s compatibility letter in writing, then do the mockup anyway.

If your epoxy or tile is already coming up

Stop installing and test the exposed slab with a water drop. If it beads, the curing compound or another sealer is still there, and patching over it will fail the same way. Remove the finish in the affected area, grind or shot blast to the maker’s CSP, and retest moisture before you reinstall.

Check the moisture numbers too. Euclid’s limit is 85% RH or 3 lb/1,000 ft²/24 h, and above that it calls for a moisture mitigation system. Euclid also says not to coat slabs on grade without an “uninterrupted vapor barrier,” so a failure can be moisture and film together.

Keep the samples, photos and test results. When the compound was sprayed by the concrete sub and the finish spec said “free of curing compounds,” the paper trail decides who pays for the redo.