How to Apply Curing Compound

Curing compound is the easiest cure to get wrong because it looks done the moment it is on. A thin, streaky or late coat still looks like curing compound from the truck. The steps below are the ones that decide whether the film holds water in for the next week.

How do you apply curing compound to concrete?

Mix it, wait for the sheen to go, and spray an even film at the rate on the data sheet, usually in two light coats. Each step below comes from a manufacturer data sheet or a DOT spec.

1. Check the weather and the sheet. Many data sheets set a 40°F (4°C) floor. The W.R. Meadows 1100 data sheet says not to apply below that air or concrete temperature.
2. Mix the pail. Kaufman’s field procedures call for 1 to 3 minutes with a low-speed mixer. Do not add water or thinner.
3. Work out the gallons. Divide the slab area by the data sheet rate. The curing compound coverage calculator does this and rounds up to pails.
4. Wait for the cue. The sheen is gone and finishing is done. See when to apply curing compound for the full list of cues.
5. Spray the first coat. Keep the wand at one height, walk at one pace and overlap your passes.
6. Spray the second coat across the first. Two light coats at right angles fill the gaps a single pass leaves.
7. Check the film and protect it. Compare gallons used to area, re-coat thin spots, and keep rain and boots off it.

Dayton Superior warns water-based compounds should be stirred to bring the solids back up, but not with high-speed mixing equipment.

Should you spray or roll curing compound?

Spray when you can. The Dayton Superior J11W data sheet allows a low pressure sprayer or a roller but says spray is the preferred method. ACI’s curing specification, as summarized by the FHWA, requires power spraying unless the area is under 200 m² (about 2,150 ft²).

A pump-up garden sprayer is fine for a patio. The Quikrete 8730 data sheet calls for one, with two thin layers at right angles and a brush to spread any puddle. For tank sizes, tips and cleanup, see our curing compound sprayer guide.

How much curing compound do you put on?

Put on what the data sheet says, and no less. Many compounds list about 200 ft²/gal (4.9 m²/L), the same rate used to test products under ASTM C309. Some list a rate by finish: Dayton’s J11W gives 200 ft²/gal on broomed exterior concrete and 400 ft²/gal on tight steel-troweled floors.

The common mistake is spraying too thin. The Dayton Superior Guide to Curing calls it a major problem on most jobsites: crews spray at 300 to 400 ft²/gal instead of 200, and “as a result, the quality of the concrete goes down dramatically!”

Too heavy causes its own trouble. The Meadows 1100 sheet warns the surface “may discolor and/or yellow due to over-application,” and the Euclid Kurez DR VOX data sheet says heavy or uneven coats dissipate slowly and are harder to remove.

Do you need two coats of curing compound?

Two light coats are the safer habit, and some specs require them. Kaufman says to make two applications at right angles. ACI 301 requires two coats at right angles on rough surfaces, and the AASHTO spec summarized by the FHWA wants the second coat within 30 minutes of the first.

Check whether the data sheet rate is per coat or for the total before you plan quantities. The TxDOT pavement manual calls for two separate coats, each at no more than 180 ft²/gal, so plan quantities for both.

Walls, curbs and other vertical faces

Vertical faces shed compound, so go light. The J11W sheet calls for two light coats, with the second applied while the first is still wet.

How do you check that you put enough on?

Count the gallons. The FHWA notes there is no standard field test for in-place application rate, but you can estimate it by “measuring the amount of curing compound used to cover a known surface area.” Divide the area by the gallons you sprayed and compare that to the data sheet rate.

Once it dries, sprinkle water on it. TxDOT says a dried compound beads water. If a spot darkens instead of beading, it is thin there and needs another coat right away.

Can you use curing compound indoors?

Yes, if the product is rated for interior use. Read the data sheet for two things: whether the product suits interior work, and whether it has to come off before the floor finish. Many compounds block tile adhesive and coatings, so check curing compound and flooring bond before you spray a slab that will get a floor covering.

If it rains or the film goes on streaky

Rain on a fresh film is the most common reason to re-coat. Kaufman wants at least 3 to 4 hours of protection at 72°F (22°C), and the Kurez sheet says no rain or water for 4 hours. The Corps of Engineers spec quoted by the FHWA has the whole area redone if it rains within 3 hours.

After the rain, let the surface dry and run the water bead check. TxDOT calls for an additional coat wherever rain damaged the fresh compound.

For streaks, drips and puddles:

• Puddles while wet: brush or back-roll them out, as Quikrete and Kaufman both say.
• Missed strips: re-spray them as soon as you see them.
• Uneven color on colored concrete: Quikrete says even application is “extremely important” there. Keep the second coat light and even rather than spot-spraying dark areas.