Curing compound
Curing Compound vs Sealer vs Cure and Seal: What's the Difference
A curing compound is a thin film sprayed on fresh concrete to hold water in, and it wears off in weeks. A sealer goes on cured concrete to keep water and stains out. Cure and seal is a heavier curing compound that does both: it cures the fresh slab, then stays on as a sealer for 1 to 3 years.
What is the difference between a curing compound and a sealer?
Timing and job. A curing compound goes on fresh concrete within hours of finishing and keeps mix water from leaving so the surface gains strength. A sealer goes on cured concrete to keep water, salt and stains out. One protects the concrete while it hardens, the other protects it for years after.
The Euclid Chemical selection guide describes a curing compound as a thin film that restricts how much water can evaporate. It says to apply it as soon as the concrete is finished and won’t be marred, and that waiting until the next day is not as effective.
Sealers split into two families. Film-forming sealers, mostly acrylics, sit on top and add gloss. Penetrating sealers, such as silanes, siloxanes and siliconates, soak in and leave no visible film. Euclid says a penetrating sealer on a driveway lasts 5 to 10 years before it needs reapplying.
How does cure and seal fit in?
Cure and seal is a curing compound with enough resin to stay on as a sealer. You spray it on fresh concrete the same way, it does the curing, and the film remains as a light acrylic sealer with a darker, glossier look. Our concrete cure and seal guide covers when to use it.
| Curing compound | Cure and seal | Penetrating sealer | |
|---|---|---|---|
| Goes on | Fresh concrete, right after finishing | Fresh concrete, right after finishing | Cured, bare, dry concrete |
| Main job | Hold water in while it cures | Cure, then seal | Keep water and salt out |
| Standard | ASTM C309 | ASTM C1315 (often also C309) | None for curing |
| Minimum solids | None | 25% | Not applicable |
| Look | Little change; may be tinted or white | Darker, wet look, gloss | No change |
| How long it stays | Weeks, if dissipating | 1 to 3 years | 5 to 10 years on a driveway, per Euclid |
| Can go over it later | Depends; often must be removed | Only compatible products, after testing | Ask the coating maker; some won’t bond over it |
What do ASTM C309 and ASTM C1315 actually test?
Both are water-retention tests, but ASTM C1315 is tougher. It allows less water loss at a thinner application, requires 25% solids, and adds tests that ASTM C309 does not have. The Construction Specifier calls the C1315 water-loss requirement much more stringent than C309’s.
| Test | ASTM C309 curing compound | ASTM C1315 cure and seal |
|---|---|---|
| Max water loss in 72 hours | 0.55 kg/m² | 0.40 kg/m² |
| Test application rate | 200 ft²/gal (4.9 m²/L) | 300 ft²/gal (7.4 m²/L) |
| Minimum solids | None | 25% |
| Yellowing classes | Not covered | Class A non-yellowing, B moderate, C severe darkening |
| Extra tests | None | UV, acid and alkali resistance, tile adhesive bond |
Sources: Dayton Superior Guide to Curing for C309, Dayton Superior cure and seal notes for C1315, and the National Concrete Consortium presentation for the solids line.
C309 classes mean something different. Class A has no resin restriction and is often wax based. Class B is all resin. White-pigmented Type 2 products reflect sun on hot pours. Dayton also notes that sodium silicate products do not meet C309, so a “silicate cure” is not a curing compound under that standard.
Which should you use on your slab?
Let the spec decide if there is one. Euclid’s curing and sealing blog says the choice is simple when a specification governs the work. Without one, match the product to what happens to the slab next.
| Slab | Use | Why |
|---|---|---|
| Driveway, walk or patio you want glossy | Cure and seal | One trip; reseal every 2 to 3 years |
| Colored or stamped concrete | Cure and seal, C1315 Type I Class A | Non-yellowing, even color |
| Driveway you want sealed for the long haul | Dissipating curing compound, then a penetrating sealer | Euclid cleans the cure off after 4 to 6 weeks, then seals; 5 to 10 year life |
| Interior slab getting tile, vinyl, wood or epoxy | Curing compound the flooring maker accepts, or a removable one | Films can break the adhesive bond |
| Highway, DOT or commercial work | Whatever the spec names | The spec governs, per Euclid |
If you’re still unsure, run your job through the which curing compound tool.
Can you use a curing compound and a sealer on the same slab?
Yes, but in that order, and not stacked blindly. Cure first with a curing compound, then seal after it has dissipated or been removed. Euclid says a film-forming cure or cure and seal must be removed or completely worn away before a penetrating sealer goes on, because the sealer can’t soak through the film.
Using both a curing compound and a cure and seal on fresh concrete gets you nothing. The cure and seal already cures. Stacking two films only adds thickness, and thick films are where whitening, bubbling and peeling start.
If you already sprayed curing compound and now want to seal or floor it
Find out what went down first. Ask the finisher for the product name and pull its data sheet. If it is a dissipating cure, give it the weeks the sheet says, then clean the slab before you seal. If it is a resin cure or a cure and seal, plan on removal or a compatibility test.
Dayton’s Guide to Curing says curing compounds must be removed before epoxy, urethane and silane or siloxane sealers. Interior slabs getting flooring are the costly case: see our curing compound and flooring guide before any adhesive goes down.
Frequently asked questions
Can you put a sealer over curing compound?
Not a penetrating sealer. Euclid Chemical says any film-forming curing compound or cure and seal must be removed or allowed to wear away completely first. A film-forming acrylic sealer may go over a compatible acrylic cure, but check both data sheets and test a small area.
Do you need a curing compound if you use cure and seal?
No. A cure and seal that meets ASTM C1315 or ASTM C309 is the curing compound. Spray it on the fresh slab as soon as finishing is done. Adding a separate curing compound underneath just builds a thicker film.
Can you use cure and seal under tile or flooring?
Only with care. ASTM C1315 includes a bond test with a tile adhesive, but Dayton Superior's notes say meeting C1315 does not assure compatibility with every adhesive. Test the actual adhesive on the slab, or remove the film.
Does curing compound wear off?
Dissipating curing compounds are built to break down, and Euclid's guide has the residue cleaned off after 4 to 6 weeks. Resin-based curing compounds and cure and seals last longer, and Dayton Superior says curing compounds must be removed before epoxy, urethane or silane and siloxane sealers.