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B. Cold -Weather Concreting - Conform to ACI 306. <br />1. Temperature of concrete when placed shall not be less than following: <br />Air Temp. IF. <br />Sections with Least Dimension <br />Under Twelve Inches (1211) <br />Sections with Least Dimension <br />Twelve Inches 12" and Over <br />Above 45 <br />55° F. <br />50° F. <br />30 to 45 <br />60° F. <br />55° F. <br />0 to 30 <br />70° F. <br />60° F. <br />Below 0 <br />70° F. <br />65° F. <br />2. When placed, the temperature of heated concrete shall not be more than ten degrees <br />Fahrenheit (10° F) higher than the above minimums. <br />3. Before placing concrete, all ice, snow, and surface and subsurface frost shall be <br />removed. The temperature of the surfaces to be in contact with the new concrete shall <br />be raised above thirty-five degrees Fahrenheit (3500F.) for a minimum of twelve (12) <br />hours. <br />4. Protect concrete from freezing during specified curing period. <br />5. Keep forms on for a minimum of five (5) days unless water curing. <br />6. Heated enclosures shall be strong and windproof to insure adequate protection of <br />corners, edges, and thin sections. <br />7. Do not permit heating units to locally heat or dry the concrete. <br />8. Do not use combustion heaters during the first twenty-four (24) hours unless the <br />concrete is protected from exposure to exhaust gases that contain carbon dioxide. <br />9. Cold weather protection shall be maintained at a minimum temperature of fifty <br />degrees Fahrenheit (50° F.) for a minimum of seven (7) days after the concrete is <br />placed. See ACI 306 for requirements on allowable temperature differential during <br />the curing period. <br />10. Maximum allowable gradient drop in the first 24 hours after curing period and end of <br />protection is fifty degrees Fahrenheit (50° F.) for sections with a least dimension <br />under twelve inches (12") and forty degrees Fahrenheit (40° F.) for sections with a <br />least dimension of twelve inches (12") or greater. <br />11. Provide maximum and minimum thermometers placed on concrete surfaces spaced <br />throughout Work to allow monitoring of concrete surface temperatures representative <br />of Work. <br />12. Refer to ACI 306 for further requirements. <br />Cast -In -Place Concrete February 2017 03300-6 <br />