EP0110542A1 - Concrete strengthening members, particularly prestressing tendons, having improved corrosion resistance and/or bonding characteristics, and methods relating thereto - Google Patents
Concrete strengthening members, particularly prestressing tendons, having improved corrosion resistance and/or bonding characteristics, and methods relating thereto Download PDFInfo
- Publication number
- EP0110542A1 EP0110542A1 EP83306399A EP83306399A EP0110542A1 EP 0110542 A1 EP0110542 A1 EP 0110542A1 EP 83306399 A EP83306399 A EP 83306399A EP 83306399 A EP83306399 A EP 83306399A EP 0110542 A1 EP0110542 A1 EP 0110542A1
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- EP
- European Patent Office
- Prior art keywords
- strand
- concrete
- coating
- prestressing
- plastic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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- 239000004567 concrete Substances 0.000 title claims abstract description 61
- 238000005260 corrosion Methods 0.000 title claims abstract description 36
- 230000007797 corrosion Effects 0.000 title claims abstract description 36
- 238000005728 strengthening Methods 0.000 title claims abstract description 12
- 238000000034 method Methods 0.000 title claims description 22
- 210000002435 tendon Anatomy 0.000 title abstract description 42
- 238000000576 coating method Methods 0.000 claims abstract description 39
- 239000011248 coating agent Substances 0.000 claims abstract description 37
- 239000000843 powder Substances 0.000 claims abstract description 27
- 238000012546 transfer Methods 0.000 claims abstract description 24
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 19
- 239000002245 particle Substances 0.000 claims abstract description 19
- 239000010959 steel Substances 0.000 claims abstract description 19
- 239000006223 plastic coating Substances 0.000 claims abstract description 17
- 230000004927 fusion Effects 0.000 claims abstract description 10
- 230000001464 adherent effect Effects 0.000 claims abstract description 7
- 230000000694 effects Effects 0.000 claims abstract description 5
- 229920001187 thermosetting polymer Polymers 0.000 claims abstract description 5
- 239000004033 plastic Substances 0.000 claims description 14
- 229920003023 plastic Polymers 0.000 claims description 14
- 229920006334 epoxy coating Polymers 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 12
- 239000011513 prestressed concrete Substances 0.000 claims description 5
- 238000010791 quenching Methods 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 4
- 238000005452 bending Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 230000000171 quenching effect Effects 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims 1
- 238000007906 compression Methods 0.000 claims 1
- 239000000155 melt Substances 0.000 claims 1
- 238000002844 melting Methods 0.000 claims 1
- 230000008018 melting Effects 0.000 claims 1
- 239000004593 Epoxy Substances 0.000 abstract description 14
- 229920005989 resin Polymers 0.000 abstract description 11
- 239000011347 resin Substances 0.000 abstract description 11
- 238000005507 spraying Methods 0.000 abstract description 2
- 238000011161 development Methods 0.000 description 10
- 230000003014 reinforcing effect Effects 0.000 description 10
- 239000007921 spray Substances 0.000 description 6
- 230000008569 process Effects 0.000 description 5
- 230000002787 reinforcement Effects 0.000 description 5
- 239000011440 grout Substances 0.000 description 3
- 239000011253 protective coating Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 238000005299 abrasion Methods 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 239000004519 grease Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 238000005270 abrasive blasting Methods 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 125000003700 epoxy group Chemical group 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/20—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to wires
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
- B05D5/02—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain a matt or rough surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B1/00—Constructional features of ropes or cables
- D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
- D07B1/0693—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core having a strand configuration
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
- E04C5/015—Anti-corrosion coatings or treating compositions, e.g. containing waterglass or based on another metal
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/08—Members specially adapted to be used in prestressed constructions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
- B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
- B05D1/06—Applying particulate materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D2401/00—Form of the coating product, e.g. solution, water dispersion, powders or the like
- B05D2401/20—Aqueous dispersion or solution
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2015—Strands
- D07B2201/2042—Strands characterised by a coating
- D07B2201/2044—Strands characterised by a coating comprising polymers
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2083—Jackets or coverings
- D07B2201/2084—Jackets or coverings characterised by their shape
- D07B2201/2086—Jackets or coverings characterised by their shape concerning the external shape
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2207/00—Rope or cable making machines
- D07B2207/40—Machine components
- D07B2207/404—Heat treating devices; Corresponding methods
- D07B2207/4068—Heat treating devices; Corresponding methods for curing
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2501/00—Application field
- D07B2501/20—Application field related to ropes or cables
- D07B2501/2015—Construction industries
- D07B2501/2023—Concrete enforcements
Definitions
- This invention relates to steel members for strengthening concrete, particularly prestressing tendons of wire and strand types for prestressing by pretensioning or postten- sioning, but applicable in some respects to reinforcing bars, wires, or the like.
- the invention more particularly relates to improvements in corrosion resistance and/or bond control of such members.
- PC wire or strand used for prestressing concrete
- Strand is formed by spinning a number of wires (typically six) together around a central core.
- the magnitude of the problem is exemplified by the fact that use of PC strand or wire is discouraged or prohibited in certain areas where it advantageously could be used.
- galvanized strands are not as strong as stress-relieved strands of the same size, and they cannot be fabricated so that they possess all of the desirable properties that are obtained by stress-relieving uncoated strands. They are appreciably more expensive per unit of strength, their bond properties are not consistent, and there can be a chemical reaction between the zinc coating and the cement paste in concrete. Although galvanized strands have been available since before the development of prestressed concrete, they are seldom used.
- Single unbonded posttensioned strands are used in the construction of flat slab floors for garages, apartment and office buildings, etc., and tendons made of several parallel wires are used in a similar manner.
- These tendons are typically coated with a corrosion resisting grease, encased in tubing, fastened in place and the concrete slab is cast around them. When the concrete has cured the tendon is tensioned and then permanently held under tension by an anchor at each end.
- tendons of this type are being coated with grease and encased in plastic tubing. This is an improvement on the former paper wrap, but they are still subject to corrosion in the anchorage area because typically the tubing must be removed to permit the anchor to grip the strand. Additionally, the relatively thin plastic is sometimes damaged during handling.
- Posttensioned grouted tendons have been in use as long as prestressed concrete itself.
- the tendon is threaded through a cavity that has been cast in the concrete, or the tendon is encased in an oversized flexible metal or other type of tube before concrete is cast.
- the tendon is tensioned, and the cavity around the tendon is pumped full of liquid cement grout.
- the cavity can be filled if the tendon is properly detailed and fabricated, and if the grout is properly injected. In actual practice, this is frequently not the case, and areas susceptible to corrosion are left in the cavity.
- the tendons In precast pretensioned members, the tendons typically are seven-wire strands which are tensioned and anchored in the forms. Concrete is cast around the strands. When the concrete has cured, the strands are released from their external anchors, and their prestressing force is transferred to the concrete by bond between the steel and the concrete.
- pretensioned PC tendons there is a problem not only of corrosion protection, but also one of bond transfer between the pretensioned PC tendon and the concrete.
- Patent 3,030,664 discloses reinforcing elements provided with a coating comprising a suspension of a hydraulic cement and rubber in suitable proportions as to be converted by steam curing of the concrete into a hard strong layer having good adhesion to the reinforcing elements and the concrete, and supposedly serving also as a rust-protective film.
- Rice U. S. Patent 3,293,811 discloses an epoxy resin coating on PC strand to protect against notching by serrated teeth carried by anchor wedges.
- Mager U. S. Patent 3,377,757 relates to steel storage tanks prestressed by plastic coated tendons extending about the tank, the plastic coating being for the purpose of protecting the tendons from corrosion forces. Lang U. S.
- Patent 3,513,609 relates to posttensioned type tendons, including one embodiment in which the tendon incorporates a curable plastic material such as an epoxy resin between the wire or strand and an outer plastic coating, the curable resin being cured while the wire is held under tension so as to anchor the wire to the outer plastic coating and thus to the concrete structure along the length of the wire.
- the curable resin initially provides a lubricating effect and, after curing, provides a bonding effect. Curing of the resin is by passing electric current through the core wire.
- Lang U. S. Patent 3,579,931 is of the same substance. Scott U. S.
- Patent 3,596,330 discloses a structural tensile member made of steel wire or like material provided with a sheath or coating of polypropylene or other impermeable corrosion resistant material.
- Lang U. S. Patent 3,646, 748 discloses a PC strand encased in a corrosion inhibitor, and encompassed by a seamless plastic jacket tightly covering the encased strand.
- Palm U. S. Patent 3,755,003 discloses concrete reinforcing elements coated with a coating comprising a pulverulent metal in intimate mixture with the residue from a composition containing an organic component plus a hexavalent-chromium-providing substance. The coating is stated to provide corrosion resistance and enhanced adhesion for concrete to the coated element.
- Kitta U. S. Patent 3,922,437 involves coating of PC strand with an inner resin layer and then with a lubricant-containing thermoplastic material, and mentions increased corrosion protection provided by the inner resin layer.
- concrete strengthening members particularly PC tendons having formed thereon a strongly adherent plastic coating which may be substantially impermeable for improved corrosion resistance, and/or which may have embedded therein abrasive or grit-form particles to provide improved bond with the concrete, and particularly to provide controllable bond transfer in PC tendons of the pretensioned type.
- a strongly adherent plastic coating which may be substantially impermeable for improved corrosion resistance, and/or which may have embedded therein abrasive or grit-form particles to provide improved bond with the concrete, and particularly to provide controllable bond transfer in PC tendons of the pretensioned type.
- the plastic coating preferably is applied electrostatically from an aerated cloud of charged particles of resin powder, and fusion bonded by heat.
- the abrasive preferably is applied by spraying during a viscous state of the heated resin at a time when the resin has become fusion bonded into an integral coating, and can be varied as to size and spacing density so as to control the surface condition and the bonding effect.
- three forms of improved PC strand may be provided.
- a corrosion resistant strand designed primarily for postten- sioning, utilizing only the plastic coating, where bond transfer is not a consideration.
- the prestressing strands or wires are placed in the empty forms, stretched to a high tension and held at that tension by temporary anchors located beyond the ends of the forms.
- the forms are then filled with concrete which completely surrounds each tendon.
- the temporary anchors are removed, and the load in the tendon that was carried by the anchors is transferred to the member by bond between the tendon and the concrete.
- the tension in the tendon at the extreme end of the member is zero.
- Transfer length can be defined as the distance from the end of the member to the point at which the full load in a fully bonded tendon has been transferred to the concrete. Transfer length is influenced by tendon size, shape, material and surface condition and by the consistency of the concrete placed around it.
- test length When a pretensioned bonded prestressed concrete flexural member is loaded from its normal working load to ultimate flexural capacity, there is a large increase in the tension in the strand. As the tension in the strand increases, the length of strand required to transfer the tension to the concrete also increases. The length required to develop the tension which exists at the time of ultimate flexural failure is called the “development length.” For an uncoated seven-wire strand, the development length is much greater than the transfer length.
- the transfer length is computed to be approximately twenty-five inches, whereas the development length is approximately eighty inches. In most cases for a strand that is debonded at the end of the member, the development length becomes 160 inches.
- the size and number of strands in a particular member are frequently determined by the development length, and a more economical design can be achieved if the development length is shorter. It is probable that a much shorter development length can be obtained with a grit-coated strand in accordance with the invention.
- the process generally involves the sequential steps of cleaning the tendon, heating the tendon to a predetermined temperature, electrostatically coating the heated tendon in a fluidized bed, optional grit application during the gel phase of the plastic coating heated by the heated tendon, and quenching at a desired stage of curing of the plastic coating.
- the process preferably is a continuous one whereby tendon or strand passes from a pay-off sequentially through the various steps of the process to a take-up.
- the process line can include a known holiday detector, e.g., a sixty- seven one-half volt DC holiday detector, as specified in the previously mentioned ASTM standard specifications. Such detection normally would occur at the last stage before take-up.
- the cleaning step preferably is accomplished by passing the strand from the pay-off through a known ultrasonic washer and a rinse tank. This is a known manner of cleaning using well-known equipment. Abrasive blasting is unnecessary.
- the strand passes through an induction heater where it is heated to a temperature determined by, inter alia, the fusion and curing characteristics of the plastic to be coated.
- a temperature determined by, inter alia, the fusion and curing characteristics of the plastic to be coated.
- the strand is heated to between 350°F and 550°F, preferably 400°F to 450°F, so as to be at a temperature of approximately 400°F to 410°F when contacted by the resin powder.
- the heated strand is contacted with the resin powder and coated electrostatically immediately after leaving the induction heater.
- this is accomplished by passing the heated strand through a coater to be coated by electrostatic fluidized bed powder deposition.
- This is a known coating technique using commercially available coating equipment.
- powder particles are aerated in a fluidizing chamber and are electrostatically charged by ionized air which passes through a porous plate at the base of the chamber. As the powder particles become charged, they repel each other and rise above the chamber, forming a cloud of charged particles.
- the grounded strand or wire is conveyed through the cloud, the charged powder particles, because of their opposite potential, are attracted to the wire.
- the powder particles form a generally uniform coating, being more attracted to exposed areas than to those already insulated. Coating thickness is controlled by applied voltage to the charging media and exposure time to the cloud.
- a suitable commercially available coater is produced by Electrostatic Equipment Corporation, New Haven, Connecticut, U.S.A., designated as Model 700. The coater includes a powder management system for handling the resin powder.
- a suitable resin coating powder is SCOTCHKOTE brand 213, produced by Minnesota Mining and Manufacturing Company, Saint Paul, Minnesota.
- This is a fusion bonded epoxy coating comprising a one-part heat curable, thermosetting powdered epoxy coating, known for use in providing corrosion protection of pipe, girth wells and concrete reinforcing bars. It is stated to have a gel time at 400°F of 5-8 seconds.
- the cure schedule specifies a minimum time to quench of twenty-eight seconds for an application temperature of 450°F to 463°F.
- Degree of cure can be approximated by solvent tests of the epoxy coating, and can be regulated by application temperature and time of quench.
- the SCOTCHKOTE 213 product is usable, we find that a somewhat longer gel time is desirable as giving better flow of the melted epoxy powder, thus helping to avoid the occurrence of pin holes or holidays.
- Gel time can be determined to some extent by the temperature of the wire at the time of application of the epoxy powder.
- epoxy powders having longer gel times are available, and good results have been obtained using an epoxy powder of Hysol Division of Dexter Corporation, having a gel time of approximately twenty seconds. In general, prolonging the gel time facilitates obtaining a somewhat thinner, but still impermeable, coating.
- acceptable corrosion-protective coatings of approximately thirty-five mils to forty-five mils have been obtained with a gel time of approximately seven seconds, whereas acceptable corrosion-protective coatings of approximately twenty-five mils thickness have been obtained using a product with an approximately twenty second gel time.
- coating thicknesses of from ten mils to fifty mils are workable and obtainable, with a range of about twenty mils to about forty mils being presently preferred.
- the heated strand leaves the powder coater with its epoxy coating in a viscous state, ready to receive the optional grit.
- the grit should be applied as soon as possible after the melted epoxy has flowed sufficiently to close all holidays, but while the viscosity is sufficient to prevent the grit from penetrating to the metal.
- the grit may be applied in a number of manners, but preferably it is applied by pneumatic spray guns, and four such spray guns oriented at 90° from each other have been found satisfactory.
- the spray force should be regulated in keeping with the particle sizes and the viscosity condition of the epoxy so as to partially, but firmly, embed the grit in the viscous epoxy, short of contact with the steel strand or the like, so as to minimize the possibility of creating flow paths for corrosive elements along the interfaces of the grit particles and the epoxy in which they are embedded, such that they will have exposed external surfaces to bond with the concrete.
- Grit sizes of from about seventy to about 200 mesh Standard Tyler Series have been found to be satisfactory, depending on the bond characteristics desired.
- the grit may be of any of various materials, including glass frit or beads, or sand.
- contact of the grit with the steel strand is not a consideration, and the epoxy coating may be only of such thickenss as to firmly embed the grit for bond transfer purposes.
- the coated strand, with or without applied grit, is then passed through a quench tank at the desired stage of curing of the epoxy, passes therefrom optionally through a spark tester to detect pin holes and holidays, and thence to the take-up.
- epoxies are the presently preferred coatings
- other plastic resins can be used. It has been found that excellent corrosion resistance under high tension is obtainable by an epoxy coating. The coating is strongly adherent to the strand or other member, is tough, and firmly embeds the grit. It is of compatible ductility with PC strand and wire, as well as reinforcing bar material. It has good abrasion resistance, and good integrity under the conditions of stress and bending angles to be encountered.
- Bond transfer is easily satisfactorily controllable by varying grit size and density of application, and unlike conventional coated reinforcing bar, a coating thickness adequate to provide the desired corrosion resistance can be used without losing control of the bond characteristics, since the grit or abrasive readily compensates for the changed surface condition arising from the plastic coating. Indeed, the plastic coating with applied grit provides a new range of bond control or transfer length.
- the coated strand handles satisfactorily in shipping and in the field, and, for posttensioned strands that are to be grouted, avoids the problem of rust or corrosion before the grout is injected. Such strands are often exposed at the job site for a considerable time before being placed in the concrete structure. Furthermore, most specifications require that the tendons or strands be tensioned and grouted within seven days of placement in the concrete structure. This is often a severe handicap to the engineer specifying job procedure and to the contractor who cannot schedule his operation in the best manner.
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- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Reinforcement Elements For Buildings (AREA)
- Laminated Bodies (AREA)
- Wire Processing (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Moulds, Cores, Or Mandrels (AREA)
- Adhesives Or Adhesive Processes (AREA)
- Ropes Or Cables (AREA)
Abstract
Description
- This invention relates to steel members for strengthening concrete, particularly prestressing tendons of wire and strand types for prestressing by pretensioning or postten- sioning, but applicable in some respects to reinforcing bars, wires, or the like. The invention more particularly relates to improvements in corrosion resistance and/or bond control of such members.
- Corrosion of steel strengthening members in concrete has long been a problem in the art, and has received a great deal of attention. For instance, it is known to coat conventional reinforcing bars with an epoxy coating applied by electrostatic spray guns, and the American Society for Testing and Materials has issued standard specifications for epoxy-coated reinforcing bars and steel, under ASTM designations A 775-81 and D 3963-81, covering deformed and plain steel reinforcing bars with protective epoxy coating applied by the electrostatic spray method. This approach is not without its problems in that the coating thickness is specified as 5 to 12 mils, apparently in order to avoid bond problems encountered at greater thicknesses, and the lesser thicknesses involve problems of integrity or permeability of the coating, exemplified by the ASTM specifications permitting two holidays (pin holes not discernible to the unaided eye) per linear foot of the coated bar. Epoxy coating materials are available on the market for use specifically in coating reinforcing bars. A problem remains, however, in assuring an adequate corrosion-protective coating while maintaining good bonding qualities with the concrete. Ir
- Corresponding problems, but of greater magnitude and importance, exist in the case of high strength steel wire and strand used for prestressing concrete (hereafter referred to as PC wire or strand). Strand, of course, is formed by spinning a number of wires (typically six) together around a central core. The magnitude of the problem is exemplified by the fact that use of PC strand or wire is discouraged or prohibited in certain areas where it advantageously could be used. Thus, in a Memorandum dated February 10, 1981, of the Federal Highway Administration, U. S. Department of Transportation, captioned "Corrosion Protection of Reinforcement in Bridge Decks," and dealing with criteria to be applied to all reinforcement in bridge decks, prestressed or otherwise, where deicing salts or a salt water environment present the potential for corrosion, it is suggested that all conventional reinforcement be epoxy coated, but that "Pretensioning should not be permitted in bridge decks since there is no known way of eliminating the potential for corrosion," and that "Polyethylene ducts should be provided for protection of posttensioned tendons in addition to grouting." In a follow-up Memorandum dated April 14, 1981, indicating that epoxy coating of rebars (reinforcing bars or'rods) was not intended to be the only method of corrosion protection of bridge decks, it was stated that "In pretensioned work, there are currently no known methods for epoxy coating the strands, and the potential for corrosion exists in a salt water environment as well as in areas where deicing chemicals are used."
- There have been efforts to develop corrosion resistant PC tendons, and some are in use because nothing more efficient and/ or more economical was available. Thus, the use of galvanized strand is often suggested by designers concerned about corrosion and not familiar with the properties of galvanized strands. Galvanized strands are not as strong as stress-relieved strands of the same size, and they cannot be fabricated so that they possess all of the desirable properties that are obtained by stress-relieving uncoated strands. They are appreciably more expensive per unit of strength, their bond properties are not consistent, and there can be a chemical reaction between the zinc coating and the cement paste in concrete. Although galvanized strands have been available since before the development of prestressed concrete, they are seldom used. Single unbonded posttensioned strands are used in the construction of flat slab floors for garages, apartment and office buildings, etc., and tendons made of several parallel wires are used in a similar manner. These tendons are typically coated with a corrosion resisting grease, encased in tubing, fastened in place and the concrete slab is cast around them. When the concrete has cured the tendon is tensioned and then permanently held under tension by an anchor at each end. At present, tendons of this type are being coated with grease and encased in plastic tubing. This is an improvement on the former paper wrap, but they are still subject to corrosion in the anchorage area because typically the tubing must be removed to permit the anchor to grip the strand. Additionally, the relatively thin plastic is sometimes damaged during handling.
- Posttensioned grouted tendons have been in use as long as prestressed concrete itself. The tendon is threaded through a cavity that has been cast in the concrete, or the tendon is encased in an oversized flexible metal or other type of tube before concrete is cast. After the concrete is cured, the tendon is tensioned, and the cavity around the tendon is pumped full of liquid cement grout. The cavity can be filled if the tendon is properly detailed and fabricated, and if the grout is properly injected. In actual practice, this is frequently not the case, and areas susceptible to corrosion are left in the cavity.
- In precast pretensioned members, the tendons typically are seven-wire strands which are tensioned and anchored in the forms. Concrete is cast around the strands. When the concrete has cured, the strands are released from their external anchors, and their prestressing force is transferred to the concrete by bond between the steel and the concrete. Thus, in such pretensioned PC tendons, there is a problem not only of corrosion protection, but also one of bond transfer between the pretensioned PC tendon and the concrete.
- The patented technology is replete with various approaches to the problems of corrosion protection and/or bonding characteristics, including some incidental disclosures. For instance, Billner U. S. Patents 2,319,105 and 2,414,011 mention thermoplastic or thermosetting coverings which will harden and effect a bond between the concrete body and its reinforcement. Simonsson U. S. Patents 2,591,625 and 2,611,945 involve coatings including siliceous material. Wijard U. S. Patent 3,030,664 discloses reinforcing elements provided with a coating comprising a suspension of a hydraulic cement and rubber in suitable proportions as to be converted by steam curing of the concrete into a hard strong layer having good adhesion to the reinforcing elements and the concrete, and supposedly serving also as a rust-protective film. Rice U. S. Patent 3,293,811 discloses an epoxy resin coating on PC strand to protect against notching by serrated teeth carried by anchor wedges. Mager U. S. Patent 3,377,757 relates to steel storage tanks prestressed by plastic coated tendons extending about the tank, the plastic coating being for the purpose of protecting the tendons from corrosion forces. Lang U. S. Patent 3,513,609 relates to posttensioned type tendons, including one embodiment in which the tendon incorporates a curable plastic material such as an epoxy resin between the wire or strand and an outer plastic coating, the curable resin being cured while the wire is held under tension so as to anchor the wire to the outer plastic coating and thus to the concrete structure along the length of the wire. The curable resin initially provides a lubricating effect and, after curing, provides a bonding effect. Curing of the resin is by passing electric current through the core wire. Lang U. S. Patent 3,579,931 is of the same substance. Scott U. S. Patent 3,596,330 discloses a structural tensile member made of steel wire or like material provided with a sheath or coating of polypropylene or other impermeable corrosion resistant material. Lang U. S. Patent 3,646, 748 discloses a PC strand encased in a corrosion inhibitor, and encompassed by a seamless plastic jacket tightly covering the encased strand. Palm U. S. Patent 3,755,003 discloses concrete reinforcing elements coated with a coating comprising a pulverulent metal in intimate mixture with the residue from a composition containing an organic component plus a hexavalent-chromium-providing substance. The coating is stated to provide corrosion resistance and enhanced adhesion for concrete to the coated element. Kitta U. S. Patent 3,922,437 involves coating of PC strand with an inner resin layer and then with a lubricant-containing thermoplastic material, and mentions increased corrosion protection provided by the inner resin layer.
- From the foregoing, it will be apparent that the problems to which the instant invention is directed are long-standing and important, and that various solutions and approaches have been proposed. However, to our knowledge, the solutions and advantages provided by the present invention are not known in or reasonably derivable from the prior art.
- Generally in accordance with the invention, there are provided concrete strengthening members, particularly PC tendons having formed thereon a strongly adherent plastic coating which may be substantially impermeable for improved corrosion resistance, and/or which may have embedded therein abrasive or grit-form particles to provide improved bond with the concrete, and particularly to provide controllable bond transfer in PC tendons of the pretensioned type. While the basic thrust of the invention involves improving PC tendons, those aspects whereby an impermeable coating can be obtained while also controlling bond charcteristics are considered applicable also to conventional steel reinforcing bars, wire reinforcement for use in pressure vessels, pipe or the like, or other members. The plastic coating preferably is applied electrostatically from an aerated cloud of charged particles of resin powder, and fusion bonded by heat. The abrasive preferably is applied by spraying during a viscous state of the heated resin at a time when the resin has become fusion bonded into an integral coating, and can be varied as to size and spacing density so as to control the surface condition and the bonding effect. Among features achievable by the invention in its various aspects are corrosion resistance under high tension, ductility of strand and coating, adherence of the coating, toughness of the coating, abrasion resistance of the coating, integrity of the coating under stress and bending angles (an important feature because of the packaging of strand in coil packs), controllable bond transfer, and desired coating thicknesses while retaining overriding control of bond characteristics.
- In keeping with the invention, three forms of improved PC strand may be provided. Thus, there may be provided a corrosion resistant strand designed primarily for postten- sioning, utilizing only the plastic coating, where bond transfer is not a consideration. There may be provided also strand having greatly improved corrosion resistance, plus bond transfer characteristics equal to or exceeding bare strand, thus offering readily controllable bond transfer in a strand of good corrosion resistance. Thirdly, where corrosion resistance is not a major consideration, there may be provided strand of relatively modestly improved corrosion resistance, but with readily controllable bond transfer characteristics.
- Before discussing exemplary preferred embodiments of the invention, it is believed in order to mention two known concepts or characteristics relating to prestressed concrete members, these being the "transfer length" and the "development length." In a typical precast, pretensioned PC member, the prestressing strands or wires are placed in the empty forms, stretched to a high tension and held at that tension by temporary anchors located beyond the ends of the forms. The forms are then filled with concrete which completely surrounds each tendon. When the concrete has cured to the required strength, the temporary anchors are removed, and the load in the tendon that was carried by the anchors is transferred to the member by bond between the tendon and the concrete. The tension in the tendon at the extreme end of the member is zero. Within the member the tendon is trying to contract to the zero load length that existed before it was stretched. Bond or adhesion between the surface of the tendon and the concrete prevents this. Since the unit strength of the bond between the tendon and the concrete is small with respect to the total load in the tendon, an appreciable length of contact between concrete and tendon is required to transfer the full load from tendon to concrete. The length of contact required to transfer the full load is called "transfer length." "Transfer length" can be defined as the distance from the end of the member to the point at which the full load in a fully bonded tendon has been transferred to the concrete. Transfer length is influenced by tendon size, shape, material and surface condition and by the consistency of the concrete placed around it. Tests on seven-wire strands with diameters up to and including one-half inch indicate no difference in transfer length for concrete strengths of 1700 psi to 5000 psi. The second concept or characteristic is known as "development length." When a pretensioned bonded prestressed concrete flexural member is loaded from its normal working load to ultimate flexural capacity, there is a large increase in the tension in the strand. As the tension in the strand increases, the length of strand required to transfer the tension to the concrete also increases. The length required to develop the tension which exists at the time of ultimate flexural failure is called the "development length." For an uncoated seven-wire strand, the development length is much greater than the transfer length. For a typical one-half inch diameter uncoated strand, the transfer length is computed to be approximately twenty-five inches, whereas the development length is approximately eighty inches. In most cases for a strand that is debonded at the end of the member, the development length becomes 160 inches. The size and number of strands in a particular member are frequently determined by the development length, and a more economical design can be achieved if the development length is shorter. It is probable that a much shorter development length can be obtained with a grit-coated strand in accordance with the invention.
- In making improved tendons or other members in accordance with the invention, the process generally involves the sequential steps of cleaning the tendon, heating the tendon to a predetermined temperature, electrostatically coating the heated tendon in a fluidized bed, optional grit application during the gel phase of the plastic coating heated by the heated tendon, and quenching at a desired stage of curing of the plastic coating. The process preferably is a continuous one whereby tendon or strand passes from a pay-off sequentially through the various steps of the process to a take-up. Although not specifically necessary, the process line can include a known holiday detector, e.g., a sixty- seven one-half volt DC holiday detector, as specified in the previously mentioned ASTM standard specifications. Such detection normally would occur at the last stage before take-up.
- The cleaning step preferably is accomplished by passing the strand from the pay-off through a known ultrasonic washer and a rinse tank. This is a known manner of cleaning using well-known equipment. Abrasive blasting is unnecessary.
- From the rinse tank, the strand passes through an induction heater where it is heated to a temperature determined by, inter alia, the fusion and curing characteristics of the plastic to be coated. Typically the strand is heated to between 350°F and 550°F, preferably 400°F to 450°F, so as to be at a temperature of approximately 400°F to 410°F when contacted by the resin powder.
- The heated strand is contacted with the resin powder and coated electrostatically immediately after leaving the induction heater. Preferably this is accomplished by passing the heated strand through a coater to be coated by electrostatic fluidized bed powder deposition. This is a known coating technique using commercially available coating equipment. In this coating process, powder particles are aerated in a fluidizing chamber and are electrostatically charged by ionized air which passes through a porous plate at the base of the chamber. As the powder particles become charged, they repel each other and rise above the chamber, forming a cloud of charged particles. When the grounded strand or wire is conveyed through the cloud, the charged powder particles, because of their opposite potential, are attracted to the wire. The powder particles form a generally uniform coating, being more attracted to exposed areas than to those already insulated. Coating thickness is controlled by applied voltage to the charging media and exposure time to the cloud. A suitable commercially available coater is produced by Electrostatic Equipment Corporation, New Haven, Connecticut, U.S.A., designated as Model 700. The coater includes a powder management system for handling the resin powder.
- A suitable resin coating powder is SCOTCHKOTE brand 213, produced by Minnesota Mining and Manufacturing Company, Saint Paul, Minnesota. This is a fusion bonded epoxy coating comprising a one-part heat curable, thermosetting powdered epoxy coating, known for use in providing corrosion protection of pipe, girth wells and concrete reinforcing bars. It is stated to have a gel time at 400°F of 5-8 seconds. The cure schedule specifies a minimum time to quench of twenty-eight seconds for an application temperature of 450°F to 463°F. However, for purposes of the instant invention, it is preferred that the epoxy not be fully cured, but rather that curing be limited to approximately eighty percent to ninety percent of final cure. Degree of cure can be approximated by solvent tests of the epoxy coating, and can be regulated by application temperature and time of quench. Although the SCOTCHKOTE 213 product is usable, we find that a somewhat longer gel time is desirable as giving better flow of the melted epoxy powder, thus helping to avoid the occurrence of pin holes or holidays. Gel time can be determined to some extent by the temperature of the wire at the time of application of the epoxy powder. Alternatively, epoxy powders having longer gel times are available, and good results have been obtained using an epoxy powder of Hysol Division of Dexter Corporation, having a gel time of approximately twenty seconds. In general, prolonging the gel time facilitates obtaining a somewhat thinner, but still impermeable, coating. For instance, acceptable corrosion-protective coatings of approximately thirty-five mils to forty-five mils have been obtained with a gel time of approximately seven seconds, whereas acceptable corrosion-protective coatings of approximately twenty-five mils thickness have been obtained using a product with an approximately twenty second gel time. In general, depending on the particular characteristics desired in the fusion bonded coating, it is considered that coating thicknesses of from ten mils to fifty mils are workable and obtainable, with a range of about twenty mils to about forty mils being presently preferred.
- The heated strand leaves the powder coater with its epoxy coating in a viscous state, ready to receive the optional grit. In general, the grit should be applied as soon as possible after the melted epoxy has flowed sufficiently to close all holidays, but while the viscosity is sufficient to prevent the grit from penetrating to the metal. The grit may be applied in a number of manners, but preferably it is applied by pneumatic spray guns, and four such spray guns oriented at 90° from each other have been found satisfactory. The spray force should be regulated in keeping with the particle sizes and the viscosity condition of the epoxy so as to partially, but firmly, embed the grit in the viscous epoxy, short of contact with the steel strand or the like, so as to minimize the possibility of creating flow paths for corrosive elements along the interfaces of the grit particles and the epoxy in which they are embedded, such that they will have exposed external surfaces to bond with the concrete. Grit sizes of from about seventy to about 200 mesh Standard Tyler Series have been found to be satisfactory, depending on the bond characteristics desired. The grit may be of any of various materials, including glass frit or beads, or sand. Of course, for strand where corrosion is not a major consideration, contact of the grit with the steel strand is not a consideration, and the epoxy coating may be only of such thickenss as to firmly embed the grit for bond transfer purposes.
- The coated strand, with or without applied grit, is then passed through a quench tank at the desired stage of curing of the epoxy, passes therefrom optionally through a spark tester to detect pin holes and holidays, and thence to the take-up.
- Satisfactory products have been made using continuous line speeds of ten feet per minute to thirty feet per minute, and it is anticipated that line speeds up to 400 feet per minute are obtainable.
- Especially in the case of PC strand, which typically is shipped in coil packs of long length, it is possible to vary the process during treatment of a single reel, so as to provide a coil having sections with different specified characteristics.
- Although epoxies are the presently preferred coatings, other plastic resins can be used. It has been found that excellent corrosion resistance under high tension is obtainable by an epoxy coating. The coating is strongly adherent to the strand or other member, is tough, and firmly embeds the grit. It is of compatible ductility with PC strand and wire, as well as reinforcing bar material. It has good abrasion resistance, and good integrity under the conditions of stress and bending angles to be encountered. Bond transfer is easily satisfactorily controllable by varying grit size and density of application, and unlike conventional coated reinforcing bar, a coating thickness adequate to provide the desired corrosion resistance can be used without losing control of the bond characteristics, since the grit or abrasive readily compensates for the changed surface condition arising from the plastic coating. Indeed, the plastic coating with applied grit provides a new range of bond control or transfer length. The coated strand handles satisfactorily in shipping and in the field, and, for posttensioned strands that are to be grouted, avoids the problem of rust or corrosion before the grout is injected. Such strands are often exposed at the job site for a considerable time before being placed in the concrete structure. Furthermore, most specifications require that the tendons or strands be tensioned and grouted within seven days of placement in the concrete structure. This is often a severe handicap to the engineer specifying job procedure and to the contractor who cannot schedule his operation in the best manner.
- It will be understood that the foregoing description of preferred embodiments of methods in accordance with the invention are exemplary, and are susceptible to variations and modifications. For instance, although electrostatic application of the resin powder in a fluidized bed is preferred, alternative methods of application include known electrostatic spray guns, liquid application methods, etc. The preferred embodiment is preferred because of its practicality, controllability, and superiority of product. Also, it is possible to powder coat the tendon unheated, and to fuse and cure the coating thereafter in curing ovens, although we consider this to be less practical and less effective.
Claims (18)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT83306399T ATE31338T1 (en) | 1982-10-28 | 1983-10-21 | REINFORCEMENT ELEMENTS IN CONCRETE, IN PARTICULAR GUYS WITH CORROSION RESISTANCE AND/OR CONNECTIVITY AND MANUFACTURING METHOD. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US43727482A | 1982-10-28 | 1982-10-28 | |
US437274 | 1982-10-28 |
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EP0110542A1 true EP0110542A1 (en) | 1984-06-13 |
EP0110542B1 EP0110542B1 (en) | 1987-12-09 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP83306399A Expired EP0110542B1 (en) | 1982-10-28 | 1983-10-21 | Concrete strengthening members, particularly prestressing tendons, having improved corrosion resistance and/or bonding characteristics, and methods relating thereto |
Country Status (8)
Country | Link |
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EP (1) | EP0110542B1 (en) |
JP (1) | JPS59130960A (en) |
AT (1) | ATE31338T1 (en) |
AU (1) | AU578589B2 (en) |
CA (1) | CA1228998A (en) |
DE (1) | DE3374885D1 (en) |
ES (1) | ES526828A0 (en) |
ZA (1) | ZA837766B (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3437107A1 (en) * | 1984-10-10 | 1986-04-10 | Dyckerhoff & Widmann AG, 8000 München | TIE LINK, ESPECIALLY SLOPED ROPE FOR A SLIDING ROPE BRIDGE |
WO1992008551A1 (en) * | 1990-11-09 | 1992-05-29 | Florida Wire And Cable, Inc. | Coated and filled metal strand composite materials |
CN101403212A (en) * | 2008-11-13 | 2009-04-08 | 中铁二局股份有限公司 | Construction method for pretensioned prestressing concrete simply supported T-beam |
CZ300302B6 (en) * | 2005-08-12 | 2009-04-15 | Slabý@Cyril | Coated bar stock, particularly armature, process of its manufacture and apparatus for making the same |
CN101784624B (en) * | 2007-08-23 | 2013-09-25 | 日本油漆株式会社 | Powder coating composition for PC strand coating, coating method, and coating film |
EP2889131A1 (en) * | 2013-12-17 | 2015-07-01 | Rolls-Royce plc | A Laminated Composite Structure and Related Method |
WO2019001872A1 (en) * | 2017-06-29 | 2019-01-03 | Nv Bekaert Sa | Pre-stressed concrete structure with galvanized reinforcement |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS61144121U (en) * | 1985-02-25 | 1986-09-05 | ||
JPH0811791B2 (en) * | 1987-07-27 | 1996-02-07 | 神鋼鋼線工業株式会社 | Coating material for prestressed concrete tendons |
US5263307A (en) * | 1991-02-15 | 1993-11-23 | Hokkai Koki Co., Ltd. | Corrosion resistant PC steel stranded cable and process of and apparatus for producing the same |
JP2013022504A (en) * | 2011-07-20 | 2013-02-04 | Asahi Sunac Corp | Method for manufacturing winding grip |
CN111335645A (en) * | 2020-04-21 | 2020-06-26 | 中信国安建工集团有限公司 | Cast-in-place concrete floor slab construction thickness control structure and implementation method |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB894945A (en) * | 1958-08-28 | 1962-04-26 | Commw Scient Ind Res Org | Improvements in and relating to reinforcement for reinforced concrete structure and to such structures |
US3566833A (en) * | 1968-06-28 | 1971-03-02 | Anaconda Wire & Cable Co | Continuous coating apparatus |
DE2944878A1 (en) * | 1979-11-07 | 1981-05-21 | Dyckerhoff & Widmann AG, 8000 München | Concrete reinforcing rod or wire corrosion protection - involves tight full length metal sheath form locked round it |
EP0078564A2 (en) * | 1981-11-02 | 1983-05-11 | Estel Nederlandse Draadindustrie B.V. | Prestressing strand for concrete structures and concrete structures containing such strand |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE201894C (en) * | ||||
AU8593875A (en) * | 1975-10-22 | 1977-04-28 | Chemfix Pty Ltd | Metal rods and bolts |
CA1039126A (en) * | 1976-02-05 | 1978-09-26 | Mellapalayam R. Parthasarathy | Electrostatic powder deposition on elongated substrates in plural fusible layers |
JPS5523222A (en) * | 1978-08-05 | 1980-02-19 | Oiles Industry Co Ltd | Steel for prestressed concrete |
JPS6020948B2 (en) * | 1979-09-03 | 1985-05-24 | 富士ゼロックス株式会社 | Document image reading device |
-
1983
- 1983-10-19 CA CA000439302A patent/CA1228998A/en not_active Expired
- 1983-10-19 ZA ZA837766A patent/ZA837766B/en unknown
- 1983-10-21 DE DE8383306399T patent/DE3374885D1/en not_active Expired
- 1983-10-21 AT AT83306399T patent/ATE31338T1/en not_active IP Right Cessation
- 1983-10-21 EP EP83306399A patent/EP0110542B1/en not_active Expired
- 1983-10-25 AU AU20559/83A patent/AU578589B2/en not_active Expired
- 1983-10-27 ES ES526828A patent/ES526828A0/en active Granted
- 1983-10-28 JP JP58201130A patent/JPS59130960A/en active Granted
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB894945A (en) * | 1958-08-28 | 1962-04-26 | Commw Scient Ind Res Org | Improvements in and relating to reinforcement for reinforced concrete structure and to such structures |
US3566833A (en) * | 1968-06-28 | 1971-03-02 | Anaconda Wire & Cable Co | Continuous coating apparatus |
DE2944878A1 (en) * | 1979-11-07 | 1981-05-21 | Dyckerhoff & Widmann AG, 8000 München | Concrete reinforcing rod or wire corrosion protection - involves tight full length metal sheath form locked round it |
EP0078564A2 (en) * | 1981-11-02 | 1983-05-11 | Estel Nederlandse Draadindustrie B.V. | Prestressing strand for concrete structures and concrete structures containing such strand |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3437107A1 (en) * | 1984-10-10 | 1986-04-10 | Dyckerhoff & Widmann AG, 8000 München | TIE LINK, ESPECIALLY SLOPED ROPE FOR A SLIDING ROPE BRIDGE |
WO1992008551A1 (en) * | 1990-11-09 | 1992-05-29 | Florida Wire And Cable, Inc. | Coated and filled metal strand composite materials |
US5208077A (en) * | 1990-11-09 | 1993-05-04 | Florida Wire And Cable Company | Method for a composite material comprising coated and filled metal strand for use in prestressed concrete, stay cables for cable-stayed bridges and other uses |
CZ300302B6 (en) * | 2005-08-12 | 2009-04-15 | Slabý@Cyril | Coated bar stock, particularly armature, process of its manufacture and apparatus for making the same |
CN101784624B (en) * | 2007-08-23 | 2013-09-25 | 日本油漆株式会社 | Powder coating composition for PC strand coating, coating method, and coating film |
US9169403B2 (en) | 2007-08-23 | 2015-10-27 | Nippon Paint Co., Ltd. | Powder coating composition for PC strand coating, coating method, and coating film |
CN101403212A (en) * | 2008-11-13 | 2009-04-08 | 中铁二局股份有限公司 | Construction method for pretensioned prestressing concrete simply supported T-beam |
EP2889131A1 (en) * | 2013-12-17 | 2015-07-01 | Rolls-Royce plc | A Laminated Composite Structure and Related Method |
WO2019001872A1 (en) * | 2017-06-29 | 2019-01-03 | Nv Bekaert Sa | Pre-stressed concrete structure with galvanized reinforcement |
US10753095B2 (en) | 2017-06-29 | 2020-08-25 | Nv Bekaert Sa | Pre-stressed concrete structure with galvanized reinforcement |
Also Published As
Publication number | Publication date |
---|---|
EP0110542B1 (en) | 1987-12-09 |
CA1228998A (en) | 1987-11-10 |
ES8407543A1 (en) | 1984-09-16 |
JPS59130960A (en) | 1984-07-27 |
JPH0328551B2 (en) | 1991-04-19 |
ES526828A0 (en) | 1984-09-16 |
DE3374885D1 (en) | 1988-01-21 |
AU2055983A (en) | 1984-05-03 |
ATE31338T1 (en) | 1987-12-15 |
AU578589B2 (en) | 1988-11-03 |
ZA837766B (en) | 1984-09-26 |
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