JP2017088965A - Pc steel corrosion suppression structure of pre-stressed concrete structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the PC steel corrosion suppression structure of a pre-stressed concrete structure capable of suitably suppressing the corrosion of PC steel.SOLUTION: Provided is a pre-stressed concrete structure, comprising: a through hole 7 passing through a sheath 3 from the surface 2a of a concrete structure 2 to reach the vicinity of a PC steel 4; an anode material 8 inserted into the through hole 7; and an anode side filling part 9 obtained by filling a filler 5 between the through hole 7 and the anode material 8, in which the PC steel 4 and the anode material 8 are connected, and, by utilizing a potential difference between the PC steel 4 and the anode material 8, electric current is fed to the PC steel 4.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a PC steel material corrosion-inhibiting structure of a prestressed concrete structure in which prestress is mainly introduced by a post-tension method.

  Conventionally, in a post-tension type prestressed concrete structure (hereinafter referred to as a PC structure), a PC steel material is inserted through a sheath embedded in the concrete structure, and a cement-based filler (see FIG. Grout) and the PC steel material and the concrete structure are integrated.

  In this case, the PC steel material is covered with a cement-based filler, is in a highly alkaline atmosphere, and is protected from corrosion by the filler coating and the non-conductive film.

  However, the filling operation is performed so that an unfilled portion does not occur in the sheath. However, a part of the sheath is not filled with the filler due to material separation of the filler or insufficient viscosity. May be formed.

  In particular, such an unfilled portion (gap) is formed when the end fixing portion of the PC steel material is under the pavement and the end portion of the sheath is disposed obliquely upward like the PC girder of the elevated road. It is likely to occur when the sheath is crushed for some reason and the flow of the filler is prevented, or when the sheath is arranged in a wave shape.

  In addition, after inserting the PC steel material into the sheath and for a certain period before the filler is filled, the PC steel material is exposed to the sheath in a state where the filler is not filled.

  If there is an unfilled portion of the filler in the sheath, and the incoming salt or antifreeze agent enters the unfilled portion, the PC steel will be corroded by the chloride ions, and the strength will decrease due to the deterioration of the PC steel. There was a risk of causing cracks in the concrete structure due to the expansion of the steel material due to corrosion.

  Therefore, conventionally, a method is known in which the unfilled portion is refilled with a filler to be repaired by covering the PC steel material (see, for example, Patent Document 1).

  On the other hand, in order to prevent or suppress corrosion of steel materials such as reinforcing bars embedded in the concrete structure, an anode is embedded in the surface portion of the concrete structure, and the potential difference between the anode and the reinforcing bar is used to prevent corrosion of the reinforcing bars. An anticorrosion method that suppresses corrosion of reinforcing bars by supplying current is also known (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2005-023567 JP-T-08-511581

  However, in the method using refilling of the filler as described above, even if the unfilled portion is filled and repaired with the filler, it is not easy to prevent the progress of deterioration of the already corroded portion.

  Moreover, it is difficult to completely refill the unfilled portion with the filler, particularly when the PC steel is a stranded wire, the filler is filled up to the gap between the single wires constituting the PC steel. It was not easy to fill.

  Further, in this method, even when the PC steel material is protected by refilling of the filler and deterioration due to chloride ions can be avoided, the existing filler and the newly filled filler in the sheath When the chloride concentrations of the old and new fillers are different, there is a concern that new corrosion may be caused by the formation of macrocells (macroscopic cells) in the sheath due to the chloride concentration difference.

  On the other hand, the above-described cathodic protection method suppresses or prevents the corrosion of steel materials such as reinforcing bars embedded in a position relatively close to the surface of the concrete structure, and is positioned relatively away from the surface of the concrete structure. There is a possibility that the effect is not exerted on the corrosion of the PC steel material to be arranged.

  Also, in this type of cathodic protection method, when the sheath embedded in the concrete structure is made of a conductive metal material, the anticorrosion current flowing from the anode is shielded by the sheath and does not flow to the PC steel material. There was also a problem of not functioning as a structure.

  Conventionally, it is widely known that deterioration of concrete structures due to salt damage is caused by diffusion of deterioration factors such as chloride ions from the surface of the concrete structure to the inside. There is little known about the phenomenon in which deterioration factors such as matter ions diffuse to the surroundings, and no effective solution has been found for such an event.

  Then, in view of such a conventional problem, the present invention was made for the purpose of providing a PC steel material corrosion inhibiting structure and a PC steel material corrosion inhibiting method for a prestressed concrete structure that can suitably inhibit the corrosion of PC steel material. .

  The feature of the invention according to claim 1 for solving the conventional problems as described above and achieving an intended object is that a PC steel material inserted through a sheath embedded in a concrete structure, the sheath and the PC A prestressed concrete structure in which a prestress is introduced into the concrete structure by the tensioned PC steel material, and a PC-side filling portion filled with a filler between the steel material, In the PC steel material corrosion inhibiting structure of the prestressed concrete structure for inhibiting corrosion, a through-hole extending from the surface of the concrete structure to the vicinity of the PC steel material through the sheath was inserted into the through-hole. An anode material, and an anode side filling portion in which a filler is filled between the through hole and the anode material, and the PC steel material and the anode material are connected to each other. The PC steel material corrosion-inhibiting structure of the prestressed concrete structure is configured to supply a current to the PC steel material using a potential difference between the PC steel material and the anode material.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the PC-side filling portion has an existing filling portion and a refilling portion having different chloride concentrations, and the through-hole has It exists in the vicinity of the boundary of the said existing filling part and the said refilling part.

  According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the anode material is a galvanic anode formed of a metal material having a low oxidation-reduction potential with respect to the PC steel material. is there.

  According to a fourth aspect of the present invention, in addition to the structure according to any one of the first to third aspects, an insulating covering made of an insulator is provided in the through hole and outside the anode material, and the insulation is provided. The covering body is disposed across the inside and outside of the sheath.

  The feature of the invention described in claim 5 is that, in addition to the structure of any one of claims 1 to 4, the through holes are formed at intervals in the longitudinal direction of the PC steel material.

  As described above, the PC steel material corrosion inhibiting structure of the prestressed concrete structure according to the present invention is filled with a filler between the PC steel material inserted through the sheath embedded in the concrete structure and the sheath and the PC steel material. A prestressed concrete structure for suppressing corrosion of the PC steel material, wherein the prestressed concrete structure is provided with prestressed into the concrete structure by the strained PC steel material In the PC steel material corrosion-inhibiting structure, the through hole extending from the surface of the concrete structure through the sheath to the vicinity of the PC steel material, the anode material inserted into the through hole, the through hole, and the An anode-side filling portion filled with a filler between the anode material and the PC steel material and the anode material connected to each other Is, by that so as to supply current to the PC steel member by using a potential difference between the anode material and the PC steel, it is possible to suppress corrosion of PC steel the current as a protective current.

  In the present invention, the PC-side filling portion has an existing filling portion and a refilling portion having different chloride concentrations, and the through hole is a boundary between the existing filling portion and the refilling portion. By being arranged in the vicinity, there is a difference in chloride concentration between the existing filling part and the refilling part, and the macrocell corrosion caused by the difference is suppressed, and the protective effect by refilling the filler is complemented Can do.

  Furthermore, in the present invention, the anode material is a galvanic anode formed of a metal material having a low oxidation-reduction potential with respect to the PC steel material. It can be expected and an external power supply or the like is unnecessary, and the introduction cost and the maintenance cost can be reduced.

  Furthermore, in the present invention, an insulating covering made of an insulating material is provided in the through hole and outside of the anode material, and the insulating covering is disposed across the inside and outside of the sheath. Current can be prevented, and current can be supplied to PC steel reliably.

  Furthermore, in the present invention, since the through holes are formed at intervals in the longitudinal direction of the PC steel material, whether or not there is an unfilled portion of the filler (a portion where corrosion is a concern) or its position is unknown. Even so, corrosion of the PC steel material can be preferably suppressed.

It is a longitudinal cross-sectional view which shows an example of the PC steel material corrosion suppression structure of the prestressed concrete structure based on this invention. It is a cross-sectional view which shows the outline of PC steel material corrosion suppression structure same as the above. FIG. 3 is an enlarged sectional view taken along line AA in FIG. 2. (A)-(c) is sectional drawing which shows the construction method of PC steel material corrosion suppression structure same as the above, (a) is the state before construction, (b) is the state of a through-hole drilling process, (c) is It is a figure which shows the completed state. It is sectional drawing for comparing the flow of the electric current when not using the insulation coating body in the structure of the present invention and when not, (a) when the insulation coating body is used, (b) when not using the same is there.

  Next, an embodiment of the PC steel material corrosion inhibiting structure of the prestressed concrete structure according to the present invention will be described based on the examples shown in FIGS. In the figure, reference numeral 1 denotes a prestressed concrete structure such as a PC girder.

  As shown in FIG. 1, this prestressed concrete structure (hereinafter referred to as a PC structure) 1 includes a PC steel material 4 inserted through a sheath 3 embedded in a concrete structure 2, a PC steel material 4 and a sheath 3. A PC-side filling portion 6 filled with a filler 5 is provided between them, the PC steel material 4 and the concrete structure 2 are integrated, and prestress is introduced by the strained PC steel material 4.

  Further, in this PC structure 1, the end fixing portion 7 of the PC steel material 4 is positioned on the upper surface side of the concrete structure 2, the end portion of the sheath 3 is disposed obliquely upward, and the end fixing portion 7 is below the end fixing portion 7. In the initial grouting operation, an unfilled portion 8 is generated at the end of the sheath, and the unfilled portion 8 is refilled with a filler 5 such as cement grout.

  The end fixing unit 7 is provided in a concave portion 9 formed on the surface of the concrete structure 2, and after fixing the PC steel material 4 by tension, the grout operation and post-processing are performed, and the fixing unit protective concrete 10 is placed. The end fixing portion 7 is protected by filling the concave portion 9.

  The sheath 3 is formed in a spiral tube shape or a tubular shape in which a strip-shaped steel plate is spirally wound without a gap, and is embedded in the entire length of the concrete structure 2.

  The PC steel material 4 is composed of a PC steel wire obtained by simply bundling a plurality of single wires 4a, 4a ... made of steel, a PC steel stranded wire obtained by twisting the single wires 4a, 4a, or a PC steel rod, and is inserted into the sheath 3. In this state, prestress is introduced into the concrete structure 2 by a post-tension method.

  The PC-side filling portion 6 has an existing filling portion 6a previously filled with the filling material 5 and a refilling portion 6b formed by refilling the filling material 5 into the unfilled portion 8 generated at the sheath end. The existing filling portion 6a and the refilling portion 6b are adjacent to each other.

  The existing filling portion 6a and the refilling portion 6b have different chloride concentrations, the chloride concentration on the existing filling portion 6a side is high, and the chloride concentration on the newly filled refilling portion 6b side is low. However, it is assumed that a macro cell is formed due to this chloride concentration difference, and in this macro cell, the existing filling portion 6a side forms a cathode (cathode) and the refilling portion 6b side forms an anode (anode).

  The PC steel material corrosion-inhibiting structure of the PC structure 1 includes through holes 11, 11... Formed in the concrete structure 2, anode materials 12 inserted into the through holes 11, through holes 11 and anodes. An anode side filling portion 13 formed by filling a filler 5 with the material 12, the PC steel material 4 and the anode material 12 are connected, and a PC using the potential difference between the PC steel material 4 and the anode material 12 By supplying an electric current to the steel material 4, corrosion of the PC steel material 4 is suppressed.

  The through holes 11, 11... Are formed in a shape extending from the surface of the concrete structure 2 to the vicinity of the PC steel material 4 through the sheath 3 and directed in a direction intersecting the longitudinal direction of the sheath 3. The PC steel material 4 is arranged with an appropriate interval in the longitudinal direction.

  Here, the vicinity of the PC steel material 4 refers to a position separated by a distance capable of passing a current between the PC steel material 4 and the anode material 12 through the filler 5.

  These through holes 11, 11... May be arranged at regular intervals, and when corrosion of the PC steel material 4 is confirmed in advance, the through holes 11, 11.

  In a portion where macro cell corrosion is a concern, it is preferable that the through hole 11 is disposed in the vicinity of the boundary 6c between the existing filling portion 6a and the refilling portion 6b.

  Here, the vicinity of the boundary 6c means a macrocell formed across the existing filling portion 6a and the refilling portion 6b across the boundary 6c due to a chloride concentration difference between the existing filling portion 6a and the refilling portion 6b. Within the corrosive range. In addition, although the arrangement | positioning of the through-hole 11 in the macrocell part of a present Example is arrange | positioned at the existing filling part 6a side of the boundary 6c vicinity, either the existing filling part 6a side and the refilling part 6b side which pinched | interposed the boundary 6c It may be on the side.

  As shown in FIGS. 2 and 3, the through holes 11, 11... Are provided with a cylindrical insulating cover 14 made of an insulating material inside and outside the anode material 12. A body 14 is disposed across the inside and outside of the sheath 3.

  Although the aspect of the insulating covering 14 is not particularly limited, the insulating covering 14 may be constituted by a tube made of an insulator such as a vinyl chloride tube, and may be inserted into the through hole 11. It may be an insulating coating film formed by applying a resin paint, or may be formed by attaching a rubber sheet or the like to the inner peripheral surface of the through hole 11.

  The anode material 12 is a galvanic anode formed of a metal having a low oxidation-reduction potential with respect to the PC steel material 4 such as zinc or aluminum, and is electrically connected to the PC steel material 4 via the lead wire 15 and the connection box 16. It is connected to the.

  The anode-side filling portion 13 is formed by filling the same cement-based filler 5 as the PC-side filling portion 6 and penetrates the sheath 3 so that the PC-side filling portion 6, that is, the existing filling portion 6 a or refilling. It is designed to be integrated with the portion 6b.

  Next, the case where the PC steel material corrosion suppression structure is applied to the existing PC structure 1 will be described. In addition, the same code | symbol is attached | subjected and demonstrated to the structure similar to the above-mentioned Example, and the code | symbol 1 in the figure is an existing PC structure.

  In order to suppress the corrosion of the PC steel material 4 in the PC structure 1, first, as shown in FIGS. 4A to 4B, the sheath 3 and the PC steel material 4 are removed from the surface 2 a of the concrete structure 2. A plurality of through holes 11, 11 that are drilled with a drill or the like in a direction crossing the axial direction, penetrate the sheath 3 from the surface of the concrete structure 2 to the vicinity of the PC steel material 4 in the PC-side filling portion 6. Are formed at appropriate intervals in the longitudinal direction of the PC steel material 4.

  At that time, in the boundary portion between the existing filling portion 6a and the refilling portion 6b constituting the PC-side filling portion 6, the through hole 11 is formed so as to be disposed in the vicinity of the boundary 6c.

  Next, when the through-holes 11, 11 ... are formed, the insulating cover 14 is provided inside each through-hole 11, 11 .... In that case, as shown in FIG. 3, the insulating covering 14 is disposed so that at least the tip portion straddles the inside and outside of the sheath 3.

  Then, as shown in FIG. 4C, the anode material 12 is connected to the inner side of the insulating cover 14 of the through holes 11, 11. Then, it is inserted to the vicinity of the PC steel material 4 and the other end side of the lead wire 15 is led out from the opening of the through hole 11.

  Further, as the anode material 12 is inserted, a cement-type filler 5 is injected into the through hole 11, and the gap between the through holes 11, 11... And the anode material 12 is filled with the filler 5. The material 5 is cured and solidified to integrate each anode-side filling portion 13 with the existing filling portion 6a or the refilling portion 6b.

  After that, the lead wire 15 is connected to the connection box 16 and is electrically connected to the PC steel material 4 connected to the connection box 16 via the lead wire 15.

  By repeating the above steps for each of the through holes 11, 11..., A PC steel corrosion prevention structure is constructed.

  The PC steel material corrosion suppression structure of the PC structure 1 configured as described above can suppress the corrosion of the PC steel material 4 by supplying current to the PC steel material 4 from the anode material 12 and using this current as a corrosion-proof current. .

  Furthermore, in this PC steel corrosion prevention structure, since the anode material 12 is a galvanic anode formed of a metal material having a low oxidation-reduction potential with respect to the PC steel material 4, the amount of generated current is small, but sufficient corrosion inhibition is achieved. The effect can be expected, and an external power source or the like is unnecessary, so that the introduction cost and the maintenance cost can be suppressed at a low cost.

  Furthermore, the insulation coating 14 is provided inside the through holes 11, 11... And outside the anode material 12, and the insulation coating 14 is arranged inside and outside the sheath 3, so that the sheath 3 becomes conductive. Even in the case of this metal, the current e can be suitably supplied to the PC steel material 4 as shown in FIG.

  On the other hand, when the insulating covering 14 is not used, as shown in FIG. 5B, a current e flows toward the sheath 3 made of a conductive metal material, making it difficult to supply current to the PC steel material 4. There is a case.

  Moreover, in this PC steel material anti-corrosion prevention structure, the through-hole 11 is disposed in the vicinity of the boundary 6c between the existing filling portion 6a and the refilling portion 6b constituting the PC-side filling portion 6, so that the existing through the boundary 6c. A current can be suitably supplied to the PC steel 4 within the influence range of the macrocell formed across the filling portion 6a and the refilling portion 6b, and the chloride concentration difference between the existing filling portion 6a and the refilling portion 6b Can suppress macro cell corrosion.

  In the above-described embodiment, an example in which the galvanic anode method is adopted has been described. However, the anode material 12 is made of an insoluble metal such as titanium, and a DC power source is provided between the insoluble anode and the PC steel material 4 constituting the cathode. An apparatus may be connected to supply current from the insoluble anode to the rebar.

  In the case of this external power supply method, since a stable potential difference can be secured, it is classified as an anticorrosion method rather than a corrosion inhibition method, but here, this type of anticorrosion method is also explained as a concept included in the corrosion inhibition method. doing.

  Furthermore, in the above-described embodiment, the case where the refilling portion 6b is formed in the unfilled portion of the inclined sheath end portion is described. However, the aspect of the refilling portion 6b is not limited to the above-described embodiment. The refilling portion 6b may be a refilling portion 6b in which a filling material is refilled in an unfilled portion of the inclined portion caused by the forward flow of the grout in the case where the sheath 3 is arranged in a wave shape up and down.

  In the above-described embodiment, the PC girder is described as an example of the PC structure 1, but the PC structure 1 is not limited to this.

1 Prestressed concrete structure (PC structure)
2 Concrete structure 3 Sheath 4 PC steel material 5 Filler 6 PC side filling part 6a Existing filling part 6b Refilling part 7 End fixing part 8 Unfilling part 9 Recess 10 Fixing part protective concrete 11 Through hole 12 Anode material 13 Anode side Filling section 14 Insulation coating 15 Lead wire 16 Connection box

Claims (5)

A PC steel material inserted in a sheath embedded in a concrete structure, and a PC-side filling portion in which a filler is filled between the sheath and the PC steel material; In the prestressed concrete structure in which prestress is introduced into the PC steel material corrosion inhibiting structure of the prestressed concrete structure for inhibiting the corrosion of the PC steel material,
A through hole extending from the surface of the concrete structure to the vicinity of the PC steel material through the sheath, an anode material inserted into the through hole, and a filler between the through hole and the anode material An anode-side filling part filled with
PC steel material corrosion of a prestressed concrete structure, wherein the PC steel material and the anode material are connected, and a current is supplied to the PC steel material using a potential difference between the PC steel material and the anode material. Suppression structure.   The PC-side filling portion has an existing filling portion and a refilling portion having different chloride concentrations, and the through hole is disposed in the vicinity of the boundary between the existing filling portion and the refilling portion. The PC steel corrosion prevention structure of the prestressed concrete structure according to claim 1.   3. The PC steel corrosion prevention structure for a prestressed concrete structure according to claim 1, wherein the anode material is a galvanic anode formed of a metal material having a low oxidation-reduction potential with respect to the PC steel material.   The insulation coating body which consists of an insulator in the said through-hole and the outer side of the said anode material is provided, and this insulation coating body is arrange | positioned ranging over the inside and outside of the said sheath. PC steel corrosion prevention structure of prestressed concrete structure.   The PC steel material corrosion-inhibiting structure for a prestressed concrete structure according to any one of claims 1 to 4, wherein the through holes are formed at intervals in the longitudinal direction of the PC steel material.

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