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At the sole option of the Agency, the Engineer may accept concrete at a reduced pay when it is determined that the concrete will serve its intended function. 344-3.6 Placing Concrete: 344-3.6.1 Concreting in Cold Weather: Do not place concrete when the temperature of the concrete at placement is below 45°F. Meet the air temperature requirements for mixing and placing concrete in cold weather as specified in Section 346. During the curing period, if NOAA predicts the ambient temperature to fall below 35°F for 12 hours or more or to fall below 30°F for more than 4 hours, enclose the structure in such a way that the concrete and air within the enclosure can be kept above 60°F for a period of 3 days after placing the concrete or until the concrete reaches a minimum compressive strength of 1,500 psi. Assume all risks connected with the placing and curing of concrete. Although the Engineer may give permission to place concrete, the Contractor is responsible for satisfactory results. If the placed concrete is determined to be unsatisfactory, remove, dispose of, and replace the concrete at no expense to the Agency. 344-3.6.2 Concreting in Hot Weather: Meet the temperature requirements and special measures for mixing and placing concrete in hot weather as specified in Section 346. When the temperature of the concrete as placed exceeds 75°F, incorporate in the concrete mix a water -reducing retarder or water reducer if allowed by Section 346. Spray reinforcing steel and metal forms with cool fresh water just prior to placing the concrete in a method approved by the Engineer. Assume all risks connected with the placing and curing of concrete. Although the Engineer may give permission to place concrete, the Contractor is responsible for satisfactory results. If the placed concrete is determined to be unsatisfactory, remove, dispose of, and replace the concrete at no expense to the Agency. 344-3.7 Mixers: Ensure that mixers are capable of combining the components of concrete into thoroughly mixed and uniform mass, free from balls or lumps of cementitious materials, and capable of discharging the concrete uniformly. Operate concrete mixers at speeds per the manufacturer's design. Do not exceed the manufacturer's rated capacity for the volume of mixed concrete in the mixer, mixing drum, or container. 344-3.8 Small Quantities of Concrete: With approval of the Engineer, small quantities of concrete, less than 3 yd 3 placed in one day and less than 0.5 yd placed in a single placement may be accepted using a pre -bagged mixture. The Agency may verify that the pre - bagged mixture is prepared in accordance with the manufacturer's recommendations and will meet the requirements of this Specification. 344-3.9 Sampling and Testing: 344-3.9.1 Category 1: The Engineer may sample and test the concrete at his discretion to verify its quality. The minimum 28 day compressive strength requirement for this concrete is 2,500 psi. 344-3.9.2: Category 2: Provide a statement of certification from the manufacturer of the precast element that the element meets the quality control and inspection testing requirements of the Contract Documents. 344-3.9.3 Category 3: The Agency will randomly select a sample from each 200 yd3 or one day's production to determine plastic properties and to make three 4 x 8 inch cylinders for testing by the Agency at 28 days to ensure that the design compressive strength has been met. The Agency may, at its discretion, test additional concrete samples to ensure compliance with the specifications. 01025-34 Technical Specifications FAPublic Works\ENGINEERING DIVISION PROJECTS\0455-8th Street Sidewalk Improvements 18th Ct to Old Dixie\Admim\bid documents\Technical Specifications.doc