| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve strength by a method wherein when a spiral sheath is buried in concrete for insertion of a tension material for prestress concrete, integral ability for a grout material and the spiral sheath is kept. SOLUTION: A spiral sheath 1 is formed such that spiral protrusion parts 2a and 2b are continuously formed on the outer and inner peripheral surfaces of a pipe made of synthetic resin and a reinforcing wire 3, such as a steel wire, is disposed along. at least one of the protrusion parts 2a and 2b. Further, a part of the outer peripheral surface of the reinforcing wire 3 is exposed from the protrusion parts 2a and 2b. Further, a conductor for electric heating may be used as the reinforcing wire 3.</p> |
