§ 6-125. Cold weather concreting specifications.

(a)

Concrete production.

(1)

Adequate equipment shall be provided for heating the concrete materials. No frozen materials or materials containing ice shall be used.

(2)

At air temperatures below forty (40) degrees Fahrenheit and when the temperature is forecast to fall below forty (40) degrees Fahrenheit within the next twenty-four (24) hours, the concrete shall be heated.

(3)

When heated, the concrete temperature at time of delivery shall be not less than fifty (50) degrees Fahrenheit, nor greater than eighty (80) degrees Fahrenheit. It is recommended that the concrete be delivered as close as possible to a temperature of seventy (70) degrees Fahrenheit.

(4)

Heating of the concrete may be accomplished by heating the aggregates and/or mixing water. The cement must not come in contact with water having a temperature above one hundred sixty-five (165) degrees Fahrenheit. In cases where the water temperature is above one hundred sixty-five (165) degrees Fahrenheit the aggregates must be premixed with the water for one (1) minute before adding the cement.

(5)

Calcium chloride shall not be used in concrete mixes without written approval. Plants must be equipped to add calcium chloride in solution form not exceeding two (2) percent of cement weight.

(b)

Placing and finishing.

(1)

No concrete shall be deposited on nor come into contact with frozen subgrade or forms and appurtenances containing ice or snow.

(2)

Concrete surface temperature must not fall below fifty (50) degrees Fahrenheit after placement.

(3)

Slump of concrete at point of placement must not be greater than four (4) inches for flat work nor greater than five (5) inches for walls and columns.

(4)

Heating of enclosures for flat slab finishing shall be accomplished by vented heating methods, never open flame methods.

(5)

Finishing time shall be delayed in cold weather in order to properly finish the surface without bringing an excess of fines to the surface.

(6)

Slabs shall be protected from wind to prevent loss of heat and rapid drying.

(c)

Protection.

(1)

When freezing temperatures may be expected during the curing period, suitable and adequate means and facilities shall be provided for maintaining the concrete surfaces at temperatures as follows:

a.

Type I (normal) cement concrete not less than fifty (50) degrees Fahrenheit for five (5) days or seventy (70) degrees Fahrenheit for two (2) days.

b.

Type III (high-early-strength) cement concrete fifty (50) degrees Fahrenheit for three (3) days or seventy (70) degrees Fahrenheit for two (2) days.

(2)

Sudden cooling of protected concrete shall not be permitted. Protection provided shall remain in place for not less than four (4) days after artificial heating is discontinued during which time temperature of the concrete shall not be permitted to fall below forty (40) degrees Fahrenheit.

(3)

Newly constructed flat work shall be covered and protected from exposure to rain, sleet and ice for a minimum of fourteen (14) days in cold weather.

(4)

Methods of protecting concrete shall be subject to approval of the city engineer or the inspection department of the city.

(5)

Insulated forms may be used for the protection of concrete; provided, that the internal concrete temperature shall not exceed one hundred thirty (130) degrees Fahrenheit between initial and final set. Upon completion of protection period sudden cooling will not be permitted. (See paragraph (c)(2) above.)

(6)

During the entire cold-weather protection period adequate means shall be provided to prevent loss of moisture from the concrete surface.

(Code 1974, § 5-14)