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1 <br /> constituents of "pumping" or migration of air. All vibrators shall be supplemented <br /> by proper wooden spade puddling adjacent to forms to removed included bubbles <br /> and honeycomb. This is essential for the top lifts of walls. All vibrators shall travel <br /> at least 10,000 rpm and be of adequate capacity. At least one vibrator shall be <br /> used for every 10 cubic yards of concrete placed per hours. In addition, one spare <br /> 1 vibrator in operating condition shall be on the site. <br /> J. Concrete slabs on the ground shall be well-tamped into place and foundation <br /> material shall be well-tamped, and rolled until thoroughly compacted prior to <br /> placing concrete. <br /> K. Concrete shall be deposited continuously in layers of such thickness that no <br /> concrete will be deposited on concrete which has hardened sufficiently to cause <br /> the formation of seams and planes of weakness within the section. If a section <br /> cannot be placed continuously, construction joints may be located at points as <br /> 1 provided for in the Drawings or approved by the Engineer. <br /> 3.08 CURING AND PROTECTION <br /> 1 A. Protect all concrete work against injury from the elements and defacements of any <br /> nature during construction operations. Special curing procedures shall be <br /> implemented as described herein to minimize the cracking of concrete in water <br /> 1 retaining structures. <br /> B. Concrete placed at air temperature below 40 degrees F shall have a minimum <br /> e temperature of 60 degrees F. When the air temperature is below 40 degrees F <br /> and falling, the water and aggregates shall be heated before mixing. Accelerating <br /> chemicals shall not be used prevent freezing. All concrete shall be so protected <br /> that the temperature at the surface will not fall below 50 degrees F for at least 7 <br /> days after placing. The Contractor shall submit for approval by the Engineer the <br /> methods he proposes to use against low temperatures. No salt, manure, or other <br /> chemicals shall be used for protection. <br /> tC. All concrete, particularly exposed surfaces, shall be treated immediately after <br /> concreting or cement finishing is completed to provide continuous moist curing <br /> above 50 degrees F for at least 7 days, regardless of the ambient air temperature. <br /> Walls and vertical surfaces may be covered with continuously saturated burlap, or <br /> other approved means; horizontal surfaces, slabs, etc., shall be ponded to a depth <br /> of 1/2 inch or kept continuously wet by use of wet burlap. <br /> 1. Slabs of water retaining structures shall be wet cured continuously with wet <br /> burlap or other approved means for a minimum of 14 days if Type II <br /> cement is used for 3 days if Type III cement is used. <br /> 2. Walls of water retaining structures shall have all their exposed surfaces <br /> covered from direct sunlight and forms left in place for a minimum of 3 <br /> days. Curing shall commence within four hours after concrete placement. <br /> D. In cold weather supplementary continuous warm curing (above 50 degrees F) shall <br /> provide a total of 350-day degrees (i.e., 5 days 70 degrees F, etc.) of heat. <br /> ' E. In hot weather, concrete when deposited shall have a placing temperature which <br /> will not cause difficulty from loss of slump, flash set or formation of cold joints. In <br /> no case shall the temperature of concrete being placed exceed 90 degrees F. <br /> 1 F. Finished surface and slabs shall be protected from the direct rays of the sun to <br /> prevent checking and crazing. <br /> 05/08 03300-10 05-4893 <br />