Reso 2007-1150 - Laserfiche WebLink

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IVI IL4 constituents of "pumping" or migration of air. All vibrators shall be supplemented by proper wooden spade puddling adjacent to forms to removed included bubbles and honeycomb. This is essential for the top lifts of walls. All vibrators shall travel at least 10,000 rpm and be of adequate capacity. At least one vibrator shall be used for every 10 cubic yards of concrete placed per hours. In addition, one spare vibrator in operating condition shall be on the site. Concrete slabs on the ground shall be well- tamped into place and foundation material shall be well- tamped, and rolled until thoroughly compacted prior to placing concrete. K. Concrete shall be deposited continuously in layers of such thickness that no concrete will be deposited on concrete which has hardened sufficiently to cause the formation of seams and planes of weakness within the section. If a section cannot be placed continuously, construction joints may be located at points as provided for in the Drawings or approved by the Engineer. 3.08 CURING AND PROTECTION A. Protect all concrete work against injury from the elements and defacements of any nature during construction operations. Special curing procedures shall be implemented as described herein to minimize the cracking of concrete in water retaining structures. B. Concrete placed at air temperature below 40 degrees F shall have a minimum temperature of 60 degrees F. When the air temperature is below 40 degrees F and falling, the water and aggregates shall be heated before mixing. Accelerating chemicals shall not be used prevent freezing. All concrete shall be so protected that the temperature at the surface will not fall below 50 degrees F for at least 7 days after placing. The Contractor shall submit for approval by the Engineer the methods he proposes to use against low temperatures. No salt, manure, or other chemicals shall be used for protection. C. All concrete, particularly exposed surfaces, shall be treated immediately after concreting or cement finishing is completed to provide continuous moist curing above 50 degrees F for at least 7 days, regardless of the ambient air temperature. Walls and vertical surfaces may be covered with continuously saturated burlap, or other approved means; horizontal surfaces, slabs, etc., shall be ponded to a depth of 1/2 inch or kept continuously wet by use of wet burlap. 1. Slabs of water retaining structures shall be wet cured continuously with wet burlap or other approved means for a minimum of 14 days if Type II cement is used for 3 days if Type III cement is used. 2. Walls of water retaining structures shall have all their exposed surfaces covered from direct sunlight and forms left in place for a minimum of 3 days. Curing shall commence within four hours after concrete placement. D. In cold weather supplementary continuous warm curing (above 50 degrees F) shall provide a total of 350 -day degrees (i.e., 5 days 70 degrees F, etc.) of heat. E. In hot weather, concrete when deposited shall have a placing temperature which will not cause difficulty from loss of slump, flash set or formation of cold joints. In no case shall the temperature of concrete being placed exceed 90 degrees F. F. Finished surface and slabs shall be protected from the direct rays of the sun to prevent checking and crazing. 16101 03300 -10 03 -4197