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1 6-02.3(25)B Prestressing <br /> 2 Each stressing system shall have a pressure gauge or load cell that will measure <br /> 3 jacking force. The gauge shall display pressure accurately and readably with a dial at <br /> 4 least 6 inches in diameter or with a digital display. Each jack and its gauge shall be <br /> 5 calibrated as a unit and shall be accompanied by a certified calibration chart. The <br /> 6 Contractor shall submit a Type 1 Working Drawing consisting of 1 copy of this chart. ' <br /> 7 The cylinder extension during calibration shall be in approximately the position it will <br /> 8 occupy at final jacking force. <br /> 9 <br /> 10 Jacks and gauges shall be recalibrated and recertified: <br /> 11 <br /> 12 1. Annually, <br /> 13 <br /> 14 2. After any repair or adjustment, and <br /> 15 <br /> 16 3. Anytime there are indications that the jack calibration is in error. <br /> 17 <br /> 18 The Engineer may use load cells to check jacks, gauges, and calibration charts before <br /> 19 and during tensioning. <br /> 20 <br /> 21 All load cells shall be calibrated and shall have an indicator that shows prestressing <br /> 22 force in the strand. The range of this cell shall be broad enough that the lowest 10 II <br /> 23 percent of the manufacturer's rated capacity will not be used to measure jacking force. <br /> 24 <br /> 25 From manufacture to encasement in concrete, prestressing strand shall be protected <br /> 26 against dirt, oil, grease, damage, and all corrosives. Strand shall be stored in a dry, <br /> 27 covered area and shall be kept in the manufacturer's original packaging until placement <br /> 28 in the forms. If prestressing strand has been damaged or pitted, it will be rejected. <br /> 29 Prestressing strand with rust shall be spot-cleaned with a nonmetallic pad to inspect for <br /> 30 any sign of pitting or section loss. Once the prestressing steel has been installed, no <br /> 31 welds or grounds for welders shall be made on the forms or the steel in the girder, <br /> 32 except as specified. <br /> 33 <br /> 34 Post-tensioning of spliced prestressed concrete girders shall conform to Section 6- <br /> 35 02.3(26) and the following requirements: <br /> 36 <br /> 37 1. Before tensioning, the Contractor shall remove all side forms from the cast-in- <br /> 38 place concrete closures. From this point until 48 hours after grouting the I <br /> 39 tendons, the Contractor shall keep all construction and other live loads off the <br /> 40 Superstructure and shall keep the falsework supporting the superstructure in <br /> 41 place. <br /> 42 <br /> 43 2. The Contractor shall not tension the post-tensioning reinforcement until the <br /> 44 concrete in the cast-in-place closures reaches the minimum compressive <br /> 45 strength specified in the Plans. This strength shall be measured with concrete <br /> 46 cylinders made of the same concrete and cured under the same conditions as <br /> 47 the cast-in-place closures. <br /> 48 <br /> 49 3. All post-tensioning shall be completed before placing the sidewalks and <br /> 50 barriers on the Superstructure. <br /> 51 I <br /> I <br /> AMENDMENTS TO THE 2014 STANDARD SPECIFICATIONS BOOK <br /> Revised: 8/3/15 <br />