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15.6 Repair of Damaged Sheathing <br />The following is a recommended guideline for determining when damaged sheathing is to be <br />repaired, and what methods and materials are to be used in the repair process. <br />The purpose of the sheathing material is two -fold. First, it prevents the concrete -from bonding to <br />the prestressing steel so that it can be tensioned after concrete placement. Second, it contains <br />the P-T coating and serves as a barrier against corrosion. <br />In an aggressive environment, where the designer has specified an encapsulated system, the <br />requirements call for the tendon to be completely watertight from end anchor to end anchor. <br />This Is strictly Interpreted that 114 prestressing steel is to be exposed and that ail rips, tears, or <br />gaps In the tendon sheathing are to be repaired using one of the methods described below. <br />In a non -aggressive environment, where the designer has specified the use of a standard <br />system, the requirements are typically not as stringent as those referenced above for aggressive <br />environments. Typically, for standard system applications, a maximum of 1 inch of exposed <br />prestressing steel Is allowed behind the stressing -end anchors and a maximum of 12 inches <br />is allowed at the fixed -end anchors. In addition, rips and tears 1 Inch or less In length may be <br />left un-repaired; however, all gaps (total discontinuities) in the sheathing should be repaired as <br />described below. In some non -aggressive environment applications, the engineer may specify <br />more stringent requirements than those noted above. <br />Rios and tears In the sheathing greater than 1 inch in length should be repaired according to <br />method #t or #2 (described below) in order to protect (he strand and prevent excess friction <br />during stressing. All gaps (total discontinuities) in the sheathing should be repaired using only <br />method #1 described below. <br />Repair Method #1: <br />1. Restore tendon P-T coating in damaged area If needed. <br />2. Place a section of split tubing over the damaged area (tendon sheathing can be used if <br />two pieces are overlapped). It should overlap at least 3 inches (75 mm) past each end <br />of the original tendon's sheathing. <br />3. Spirally wrap the entire length of the repair area with tape, overlap 50%, and extend <br />the tape past the end of the repair section by 3 inches (75 mm) In both directions. <br />89 <br />