Curing and Protection. A. Curing and protection of concrete shall conform with ACI 301, Chapter 12, and as specified hereinafter. Curing to be used shall be by means of direct application of water, by continuous spraying, ponding, or continuously wetted covers. Curing compound will be permitted provided that the compound be compatible with sealer/hardener to be used. Water curing shall be continuous for a minimum of 7 days at temperature above 50 degrees F. Covering shall be left for an additional minimum of 4 days without wetting to allow concrete surface to dry slowly. Intermittent wetting and drying will not be allowed. Curing shall be maintained during non-working hours including weekends and holidays. 1. During hot weather, the form work and reinforcing shall be sprayed with water and cooled to a temperature of not more than 90 degrees F. and subgrades shall be dampened prior to concreting. Whenever the evaporation rate is expected to approach 0.2 lbs. Per square for per hour as per ACI 305R, Paragraph 2.1.5 and Fig. 2.1.5, windbreaks and sunshades shall be erected, fog nozzles shall be used to cool and moisten surrounding air, form work and reinforcing, and concrete shall be placed at the lowest practical temperature. The temperature of concrete when placed shall not exceed 90 degrees F., and if greater than 75 degrees F., preparations must be made to transport, place and consolidate, and finish the concrete at the fastest possible rate. Curing shall start as soon as finishing has been completed and/or the water sheen has disappeared. Forms shall be removed as soon as possible or loosened and water curing started immediately. 2. During cold weather, the temperature of the concrete as placed shall not be less than 55 degrees F. The curing temperature shall be maintained at not less than 50 degrees F. for a minimum period of 5 days. Drying of the concrete surface in heated enclosures is to be avoided by proper curing or by maintaining the relative humidity above 40 percent within the enclosure. Water curing should be terminated 12 hours before the end of the temperature protection period and the concrete shall be permitted to dry prior to and during the 24-hour of adjustment to ambient cold weather conditions as outlined in ACI 306R. No further curing is required as long as the air temperature remains below 50 degrees F., except normal curing practice shall apply when air temperatures remain above 50 degrees F. for more than half of any 24-hour period. 3. In addition to the Specification requirements for curing and protection outlined above, the curing and protection requirement not mentioned shall conform to ACI 505R, ACI 306R and ACI 308.
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