Guide to Curing Compounds

See Curing Compounds for information on individual products

Suggestions for Curing Compounds include, but are not limited to, the following:

Curing concrete is critical for superior performance and is the final and most important step in producing good concrete. Retention of moisture in fresh concrete during the hydration process builds strength, improves abrasion resistance and freeze-thaw resistance. It is very important to cure the concrete immediately after finishing.
Membrane-applied curing compounds are preferred to wet curing. Wet burlap, water spray and plastic sheets are effective methods only if it is possible to keep the concrete constantly damp for 7 days. If concrete is not cured, then the strength can be reduced by up to 40% and can result in surface cracking, crazing, dusting and other surface defects.
The main performance specification for curing compounds: "ASTM-C-309 Liquid Membrane-Forming Compounds for Curing Concrete. The curing compound shall not allow the concrete specimen to lose more than .55 kg of water per square meter of surface area in 72 hours. The white pigmented compound shall exhibit a reflectance of at least 60% of that of a standard magnesium oxide reference plate."

Types of curing compounds:

Type 1 - Clear or translucent without fugitive dye Type 1D - Clear or translucent with fugitive dye.

Type 2 - White pigmented.

The curing compound shall also be one of the following classes:

Class A - No restrictions on the vehicle solids in the curing compound - typically wax-based materials.

Class B - The vehicle solids in the curing compound must be all resin.

(According the ASTM Committee on Curing, no sodium silicate curing compound will meet the ASTM-C-309 specifications.)

Water-based products need thorough agitation before each use, but do not over agitate them or use high speed mixing equipment.
Always uniformly apply the curing compound at the specified rate (typically 200 ft²/gallon, 4.9 m²/liter). The quality of the concrete decreases dramatically if the curing compound is applied at higher application rates. Curing compound should be applied at a rate heavy enough to create a slight flood of material on the concrete surface or in two applications, one at right angles to the other.
Most curing compounds will have to be removed before a hardener (sodium silicate), sealer (acrylic or urethane), water repellent (silane or siloxane) or other concrete treatment can be applied.
Resin-based curing compounds, like Resi-Chem Clear, will normally oxidize and begin to wear off in 30 to 60 days. However, this process depends on the sunlight, temperature and traffic exposure the surface receives. Typically, stiff brooming or low pressure water blasting is the only cleaning required after 30 to 60 days of exposure. If the resin-based curing compound did not oxidize, or if it has been less than 30 days since the application of the curing compound, then additional cleaning with high pressure, warm water blasting (2000 psi, 13.8 MPa), light sand blasting, or chemical removal may be necessary.