What are the curing requirements for concrete pavement in New Hampshire?

"Curing shall begin as soon as the concrete has hardened sufficiently to prevent surface damage fro m the water spray. All exposed surfaces of the precast unit shall be kept wet with a continuous fine spray of water in an enclosure maintained at a temperature of not less than 68 F o for 72 hours or until 80% of the 28 day compressive strength is reached." [1] "All exposed concrete surfaces on the precast unit shall be covered with burlap, saturated w ith water before applying. The burlap will be kept saturated and the units kept at a temperature of not less than 68 degrees F for 72 hours or until 80% of the 28 day compressive strength is reached." [1] "3.10 Curing Concrete. 3.10.1 All exposed surfaces of concrete, except Class F, Flowable Fill, shall be cured in accordance with the requirements of Table 520 -9. All water used to wet cure concrete shall conform to 2.5. Failure to cure concrete by an approved method shall be cause for rejecting the work." [4] "TABLE 520 - 9 - CONCRETE CURING Type of Construction Curing Method Minimum Number of Days Be fore Membrane Application Horizontal Vertical Bridge Decks, approach slabs and overlays c per Section 538 per Section 538 Concrete to be treated w/ Item 534 a All other concrete except Class F, Flowable Fill a or b 14 7 Cure Method “ a” - Concret e shall be kept moist until it can support curing covers at which time it shall be completely covered with a vapor -proof barrier conforming to 2.6.2. Water shall be reapplied as necessary to keep the surface of the concrete wet for the entire 7 day cure period. Cure Method “ b” - Immediately after finishing, all exposed surfaces shall be treated with a liquid curing compound conforming to 2.6.3 at the rate of 1 gallon per 200 square feet or by fog spray, sprinkling or ponding of water conforming to 2.5 or any combination of the above, when the weather permits. Within 24 hours of finishing, these surfaces shall be completely covered with a vapor -proof barrier conforming to 2.6.2 for the remainder of the 7 days. Cure Method “ c” - The surface shall receive a wet cure utilizing water retaining material for at least 7 days. Water retaining material shall be b urlap conforming to 2.6.1 , cotton mats conforming to 2.6.4 or other approved water retaining material. Water retaining material shall be kept wet for the entire seven days." [4] "3.10.2. During the first 24 hours, the water retaining material shall be kept continuously wet by means of an approved automatic sprinkling or wetting system. After 24 hours, the Contractor may cover the wet water retaining material with a 4 mil minimum white polyethylene film for the remainder of the curing period in lieu of using a sprinkling or wetting system although wetting under the polyethylene may be required." [5] "3.10.2.1 Burlap shall be applied damp within 30 minutes after concrete has been finished." [5]

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