Curing Compound Glossary

These are the terms you will see on curing compound data sheets, project specs and DOT approved lists, grouped by what they describe. Each definition names where it comes from, so you can check the wording against the sheet in your hand.

What do the curing compound types and classes mean?

Type tells you what the compound looks like, and Class tells you what its solids are made of. The FHWA tech brief on curing paving mixtures lists them under AASHTO M 148 (ASTM C309): Type 1 clear, Type 1D clear with fugitive dye, Type 2 white pigmented, Class A unrestricted and Class B resin based.

• Type 1. Clear or translucent curing compound with no dye. The ASTM C309 summary says Types 1 and 1-D “shall be clear or translucent.”
• Type 1-D. A Type 1 compound with a fugitive dye added so you can see where you sprayed. Iowa DOT Section 4105 calls for clear compounds meeting ASTM C309 Type 1-D, Class A.
• Type 2. Curing compound made of finely divided white pigment and vehicle. The ASTM C309 summary requires a daylight reflectance of at least 60 percent, and FHWA recommends white pigmented compound on hot, sunny days because it lowers concrete temperature.
• Class A. No restriction on the vehicle solids in the compound. The Dayton Superior Guide to Curing says these are typically wax based.
• Class B. The vehicle solids must be all resin, per Dayton Superior. Many resin products are listed as meeting Classes A and B.
• Fugitive dye. A temporary color, usually red, that shows where the compound has gone on and then fades. W.R. Meadows says the red fugitive dye in CC-309-10WS “aids in visual application and will dissipate from the surface.” Compare the options in clear, dyed or white curing compound.

What do membrane, dissipating and cure and seal mean?

These terms describe what the film does on the slab and how long it stays. A membrane holds water in, a dissipating membrane wears off on its own, and a cure and seal stays on as a sealer.

• Membrane-forming. A liquid that dries to a continuous film on the concrete surface. ASTM C309 covers “liquid membrane-forming compounds” used “to reduce the loss of water during the early-hardening period.”
• Dissipating. A membrane built to break down and wear off. The W.R. Meadows 1100 page says it begins to break down after about four weeks of UV exposure; Dayton says wax membranes do not dissipate. More in dissipating curing compound.
• Cure and seal. A product that cures fresh concrete and later works as a sealer. ASTM C1315 covers membrane-forming liquids used as curing compounds on fresh concrete and as sealers on hardened concrete, per the ASTM C1315 summary.
• Solids content. The percent of the product that is resin, wax or pigment rather than carrier. The Euclid Chemical guide to cure and seal says higher solids give a thicker film, and that C1315 requires at least 25 percent solids.
• Dry film thickness. How thick the film is once the carrier evaporates, measured in mils (thousandths of an inch). Euclid gives about 0.8 mil (20 µm) at 15 percent solids, 1.3 mils (33 µm) at 25 percent and 1.6 mils (41 µm) at 30 percent, for one coat at 300 ft²/gal (7.4 m²/L).
• Blush. A white or cloudy haze in a cure and seal film. Euclid’s sealer troubleshooting sheet blames solvent-based cure and seal that turns white on heavy application and trapped moisture, and fixes it with a xylene solvent wash. Water-based product put down in cool, damp weather can go white and chalky.

What do VOC and g/L mean on a data sheet?

VOC is the solvent content that air rules limit, and g/L is the unit that limit is written in. Check the number on the data sheet against the rule where the job is.

• VOC. Volatile organic compound. Euclid defines VOCs as “carbon-based materials that evaporate under normal conditions” and says cure and seal VOC content has been regulated across the US since 1999. See VOC limits for curing compounds.
• g/L. Grams of VOC per liter of product, the unit on data sheets and in air district rules. The South Coast AQMD Rule 1113 table sets 100 g/L for concrete-curing compounds and 350 g/L for those used on roadways and bridges.

What do the moisture and test terms mean?

These are the lab and field measurements that show up in specs, submittals and flooring requirements. Some test the compound, some test the air, and some test the slab before a floor goes down.

• Water retention. How well a compound keeps water in the concrete, tested by ASTM C156. The test measures a compound’s ability “to reduce moisture loss from mortar specimens during the early hardening period.” FHWA notes the highway version is AASHTO T 155.
• Moisture loss. The number C156 reports, as weight of water lost per area. Dayton Superior gives the C309 limit as 0.55 kg/m² (about 0.11 lb/ft²) in 72 hours. C309 says compounds with better water retention are covered by C1315.
• Evaporation rate. How fast water leaves a fresh slab, set by air and concrete temperature, humidity and wind. FHWA says a common critical value is 0.20 lb/ft²/hr (0.98 kg/m²/hr), and that plastic shrinkage cracking risk rises when evaporation exceeds bleeding.
• MVER. Moisture vapor emission rate, the rate water vapor comes out of a slab. ASTM F1869 measures it with anhydrous calcium chloride, in pounds of moisture over 1,000 ft² in 24 hours.
• CSP. Concrete surface profile, the ICRI roughness scale for prepared concrete. It runs from CSP 1 (nearly flat) to CSP 10 (very rough, amplitude over ¼ in [6 mm]), checked against molded ICRI CSP chips.

What do bleed water, wet curing and curing duration mean?

These terms set when curing starts and how long it lasts. You spray after bleed water is gone, and you keep the slab cured for the full period whatever method you use.

• Bleed water. Free water that rises to the top of fresh concrete as the heavier solids settle, per the National Precast Concrete Association. FHWA says membrane-forming compound should go on once finishing is done and bleeding has ceased.
• Wet curing. Keeping the surface moist for the whole curing period with water, wet burlap or sheeting. FHWA says moist curing also supplies extra water for hydration. Dayton says burlap, water spray and plastic sheets work only if the concrete stays constantly damp for 7 days.
• Curing duration. How long curing lasts. The Indiana Ready Mixed Concrete Association says curing “should commence within minutes after placement and extend a minimum of 7 days,” by compound, polyethylene, water or wet burlap under poly.

If your spec and the data sheet use different labels

Most of the time they mean the same thing written two ways. Dayton Superior writes “Type I” and “Type ID” where ASTM writes Type 1 and Type 1-D, and FHWA treats AASHTO M 148 as the same spec as ASTM C309 and AASHTO T 155 as ASTM C156.

Read the fine print on any “meets” claim. Dayton’s guide lists its City White Cure J8 as meeting ASTM C309 Type 2, Class A “except daylight reflectance,” so it is not a full Type 2 product. If the spec names a Type and Class, the sheet should list both with no exceptions.