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15.6 Repair of Damaged Sheathing <br />The following is a recommended guideline for determining when damaged sheathing is fo be <br />repaired, and what methods and materials are to be used in the repair process. <br />The purpose of the sheathing material istwo-fold, First, it prevents the concrote.from bonding to <br />the prestressing steel so that it can be tensioned after concrete placement. Second, it conta(ns <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 t>Q prestressing steel is to be exposed and that III rips, tears, or <br />gaps in the tendon sheathing are to be repaired using one of the methods described below. <br />In anon-aggressive environment, where the designer has specified the use of a ar d_a d <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 to length maybe <br />left un-repaired; however, all gaps (total disconllnuities) 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 />piss and tears In the sheathing greater than i inch in length should be repaired according to <br />method #1 or #2 (described below} in order to protect the strand and prevent excess friction <br />during stressing. All aaos (total discontinuillas) in iho sheathing should bo repaired using only <br />method #1 described below. <br />Repair Method #1. <br />1 1. Restore tendon P-T coating fn 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 /> <br /> <br />es <br />