Abstract: To improve tensile strength without impairing flexibility and adhesion to concrete, and to form a thick coating in a surface layer part for preventing a basis material from being exposed by damage to the coating, a method of forming double coatings on a prestressing strand includes a primary painting process after a pre-treatment process, in which a resin coating is formed only at the surface layer, a secondary painting process in which respectively individual state resin coating is formed on an outer peripheral face of each of the core wire and surrounding wires under a loosened and separated state, thereby forming a double coating for each surrounding wire, and a finishing process of tightening and retwisting the surrounding wires about the core wire to an original state. The obtained prestressing strand has the double coating portions only at the surface layer and sufficient flexibility and adhesion to concrete.

Abstract: To improve tensile strength without impairing flexibility and adhesion to concrete, and to form a thick coating in a surface layer part for preventing a basis material from being exposed by damage to the coating, a method of forming double coatings on a prestressing strand includes a primary painting process after a pre-treatment process, in which a resin coating is formed only at the surface layer, a secondary painting process in which respectively individual state resin coating is formed on an outer peripheral face of each of the core wire and surrounding wires under a loosened and separated state, thereby forming a double coating for each surrounding wire, and a finishing process of tightening and retwisting the surrounding wires about the core wire to an original state. The obtained prestressing strand has the double coating portions only at the surface layer and sufficient flexibility and adhesion to concrete.

Abstract: To improve tensile strength without impairing flexibility and adhesion to concrete, and to form a thick coating in a surface layer part for preventing a basis material from being exposed by damage to the coating, a method of forming double coatings on a prestressing strand includes a primary painting process after a pre-treatment process, in which a resin coating is formed only at the surface layer, a secondary painting process in which respectively individual state resin coating is formed on an outer peripheral face of each of the core wire and surrounding wires under a loosened and separated state, thereby forming a double coating for each surrounding wire, and a finishing process of tightening and retwisting the surrounding wires about the core wire to an original state. The obtained prestressing strand has the double coating portions only at the surface layer and sufficient flexibility and adhesion to concrete.

Abstract: To improve a tensile strength without impairing flexibility and adhesion strength to concrete, and to form thick coating in a surface layer part for preventing a basis material from being exposed by a damage of the coating, a method of forming double coatings on a prestressing strand includes a primary painting process after a pre-treatment process, in which a resin coating is formed only in the surface layer, a secondary painting process in which respectively individual state resin coating is formed on outer peripheral face of each of the core wire and the surrounding wires under a loosened and separated state, thereby forming a double coating in each surrounding wire, and a finishing process of tightening and retwisting the surrounding wires about the core wire to an original state. The obtained prestressing strand has the double coating portions only in the surface layer thereof and enough flexibility and adhesion strength to concrete.

Abstract: Disclosed is a method of forming corrosion protection coatings on prestressing strands. It comprises the steps of untwisting sequential lengths of a prestressing strand; keeping the surrounding steel wires apart from the core steel wire to coat these steel wires with a synthetic resin; and twisting the coated steel wires to provide a prestressing strand of the original shape, thus permitting the separate coating of each steel wire, leaving, on the prestressing strand surface, the helical dent as deep and wide as the noncoated prestressing strand to assure the bond of the twisted wire to the surrounding concrete as firm as the noncoated prestressing strand. Also, an apparatus for carrying out such coating method is disclosed.

Abstract: A corrosion resistant PC steel stranded cable for a pretensioning method has a core wire and a plurality of side which are coated firmly for the corrosion proof with paint of a synthetic resin material while maintaining a stabilized stranded condition. The cable comprises the single core wire and the plurality of side wires disposed in a closely contacting relationship with each other and also with the core wire in such a manner as to define a plurality of spiral air gaps between the core wire and the side wires and also to define a plurality of spiral recessed grooves between individual adjacent ones of the side wires on the outer side of the side wires. Each of the core wire and the side wires are processed by blueing in advance. Paint of a synthetic resin material is filled in the spiral air gaps, and a coating layer of paint of a synthetic resin material is formed substantially with a uniform thickness on an entire outer periphery of the side wires including the spiral recessed grooves.