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3.08 CURING AND PROTECTION <br />1 <br />1 <br />1 12/04 03300 -10 03 -4138 <br />A. <br />Protect all concrete work against injury from the elements and defacements of any nature <br />' <br />during construction operations. Special curing procedures shall be implemented as <br />described herein to minimize the cracking of concrete in water retaining structures. <br />B. <br />Concrete placed at air temperature below 40 degrees F shall have a minimum temperature <br />of 60 degrees F. When the air temperature is below 40 degrees F and falling, the water and <br />aggregates shall be heated before mixing. Accelerating chemicals shall not be used prevent <br />freezing. All concrete shall be so protected that the temperature at the surface will not fall <br />below 50 degrees F for at least 7 days after placing. The Contractor shall submit for <br />approval by the Engineer the methods he proposes to use against low temperatures. No <br />salt, manure, or other chemicals shall be used for protection. <br />C. <br />All concrete, particularly exposed surfaces, shall be treated immediately after concreting or <br />cement finishing is completed to provide continuous moist curing above 50 degrees F for at <br />least 7 days, regardless of the ambient air temperature. Walls and vertical surfaces may be <br />covered with continuously saturated burlap, or other approved means; horizontal surfaces, <br />slabs, etc., shall be ponded to a depth of 1/2 inch or kept continuously wet by use of wet <br />burlap. <br />1. Slabs of water retaining structures shall be wet cured continuously with wet burlap <br />or other approved means for a minimum of 14 days if Type II cement is used for 3 <br />days if Type III cement is used. <br />' <br />2. Walls of water retaining structures shall have all their exposed surfaces covered <br />from direct sunlight and forms left in place for a minimum of 3 days. Curing shall <br />commence within four hours after concrete placement. <br />D. <br />In cold weather supplementary continuous warm curing (above 50 degrees F) shall provide <br />a total of 350 -day degrees (i.e., 5 days 70 degrees F, etc.) of heat. <br />E. <br />In hot weather, concrete when deposited shall have a placing temperature which will not <br />cause difficulty from loss of slump, flash set or formation of cold joints. In no case shall <br />the temperature of concrete being placed exceed 90 degrees F. <br />F. <br />Finished surface and slabs shall be protected from the direct rays of the sun to prevent <br />checking and crazing. <br />1 <br />1 <br />1 12/04 03300 -10 03 -4138 <br />