Patent ID: 8833050

Claim:
A double rustproof PC strand comprising: a single core wire and six surrounding wires that are made and rustproofed by a process comprising: (1) a first drawing of said single core wire and said six surrounding wires prior to plating; (2) plating said single core wire and said six surrounding wires after the first drawing to form a plated layer on each of said single core wire and said six surrounding wires; (3) a second drawing of said single core wire and said six surrounding wires after the plating so that said single core wire and said six surrounding wires have a diameter relationship with respect to each other that is selected from the group consisting of: (A) diameter of said single core wire: 4.42±0.05 mm, diameter of each of said six surrounding wires: 4.25±0.05 mm, (B) diameter of said single core wire: 5.22±0.05 mm, diameter of each of said six surrounding wires: 5.06±0.05 mm, and (C) diameter of said single core wire: 5.40±0.05 mm, diameter of each of said six surrounding wires: 5.25±0.05 mm; (4) twisting said six surrounding wires around said single core wire after the second drawing; and (5) forming a synthetic resin coating by applying resin powder coating material with an electrostatic powder coating system either on an outer peripheral surface of the strand or on each of said single core wire and said six surrounding wires after the plating; wherein the PC strand has (1) the synthetic resin coating on an outer peripheral surface of the strand or on each of said single core wire and said six surrounding wires; (2) the diameter relationship of said single core wire and said six surrounding wires thereof that is selected from the group consisting of: (A) diameter of said single core wire: 4.42±0.05 mm, diameter of each of said six surrounding wires: 4.25±0.05 mm, (B) diameter of said single core wire: 5.22±0.05 mm, diameter of each of said six surrounding wires: 5.06±0.05 mm, and (C) diameter of said single core wire: 5.40±0.05 mm, diameter of each of said six surrounding wires: 5.25±0.05 mm; and (3) a tensile strength of 1850 N/mm 2 or higher.