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<br />n <br /> <br />L.J <br /> <br />n <br /> <br />L.J <br /> <br />n <br /> <br />LJ <br /> <br />" <br /> <br />u <br /> <br />" <br /> <br />u <br /> <br />n <br /> <br />L.J <br /> <br />II <br /> <br />LJ <br /> <br />" <br /> <br />u <br /> <br />II <br /> <br />LJ <br /> <br />II <br /> <br />u <br /> <br />Il <br /> <br />LJ <br /> <br />" <br /> <br />LJ <br /> <br />n <br /> <br />3.08 CURING AND PROTECTION <br /> <br />A. <br /> <br />Protect all concrete work against injury from the elements and defacements of any nature <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 /> <br />B. <br /> <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 /> <br />C. <br /> <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 112 inch or kept continuously wet by use of wet <br />burlap. <br /> <br />1. <br /> <br />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 ill cement is used. <br /> <br />2. <br /> <br />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 /> <br />D. <br /> <br />In cold weather supplementary continuous warm curing (above 50 degrees F) shall provide <br />a total of350-day degrees (i.e., 5 days 70 degrees F, etc.) of heat. <br /> <br />E. <br /> <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 />Finished surface and slabs shall be protected from the direct rays of the sun to prevent <br />checking and crazing. <br /> <br />F. <br /> <br />L..J 3.09 REMOVAL OF FORMS <br /> <br />A. <br /> <br />Except as otherwise specifically authorized by the Engineer, forms shall not be removed <br />before the concrete has cured as specified above in subparagraph 3.08C and the concrete <br />has attained a strength of at least 30 percent of the ultimate strength prescribed by the <br />design, and not before reaching the following number of day-degrees (whichever is the <br />longer): <br /> <br />" <br /> <br />LJ <br /> <br />" <br /> <br />LJ <br /> <br />Il <br /> <br />L.J <br /> <br />n <br /> <br />L.J <br /> <br />Il <br /> <br />LJ <br /> <br />Il <br /> <br />L..J <br /> <br />06/05 <br /> <br />Forms for <br /> <br />Day-Degree* <br /> <br />Beams and slabs <br />Walls and vertical surfaces (non- <br />water retaining) <br />Walls and vertical surfaces (water <br />retaining) <br /> <br />500 <br /> <br />100 <br /> <br />150 <br /> <br />03300-10 <br /> <br />03-4138.8 <br />