Section 4105. Liquid Curing Compounds.
Liquid compounds for curing concrete shall comply with AASHTO M 148 and the following requirements.
Compounds shall be of a consistency that they can be readily applied by spraying to a uniform coating at a material temperature above 40°F (4°C).
When tested in accordance with Iowa DOT Materials Laboratory Test Method 901, the efficiency index of the material shall not be less than 95.0%, except that material showing moisture loss of less than 1.0% of the quantity of water remaining in the test specimen at the time the curing material is applied will be acceptable.
Liquid curing compounds shall dry to the touch in not more than 4 hours. After 12 hours, the compounds shall not track off the concrete when walked upon.
WHITE PIGMENTED COMPOUNDS.
White pigmented compounds shall consist of finely ground, white pigment and vehicle, ready mixed for use without alteration. The pigment shall not settle excessively or cake in the container, and the compound shall not thicken in storage to cause a change in consistency which may result in a non-uniform spray. After the compound sprayed on a test slab has dried, it shall have an apparent daylight reflectance not less than 60% relative to magnesium oxide. The rate of application shall be not less than 0.067 gallon per square yard (0.3 L/m2) (15 square yards per gallon (3.3 m2/L)). The compound shall be agitated just prior to being removed from the container and continuously during application.
DARK COLORED COMPOUNDS.
Dark colored compounds shall consist of asphalt emulsion or asphalt cut back with a volatile solvent and shall contain not less than 50.0% asphalt. The rate of application shall be not less than 0.08 gallon per square yard (0.36 L/m2) (12.5 square yards per gallon (2.8 m2/L)).
When clear curing compounds are specified, the following shall apply in lieu of other requirements of this section:
Clear liquid membrane curing compounds shall comply with requirements of AASHTO M 148, Type 1, Class A. Only one type of material shall be used on a structure.
Approvals of individual lots of curing compound are valid for the year in which the compound is manufactured. Lots of 5 barrels (1000 L) or more of white pigmented compound which have been carried over the winter will be retested if stored in a heated warehouse. Carryover lots of white pigmented compound of less than 5 barrels (1000 L) shall not be used.
Carryover lots of all curing compounds, which have been frozen shall not be used.