JP5312526B2 - Method for inhibiting corrosion of PC tendons - Google Patents

Description

  The present invention relates to a method of inhibiting corrosion of a PC tension member, and more specifically, a PC tension member in a poorly filled portion of a grout material in a sheath detected by an existing PC structure of a post tension type, or a new post tension type PC structure. The present invention relates to a method for inhibiting corrosion of a PC tendon rusting before injecting a grout material into the sheath of the metal.

  Generally, in a prestressed concrete structure (hereinafter referred to as a PC structure), a PC tension material of a post tension type is used in a highly alkaline atmosphere due to a cement-type grout material injected into a gap between a sheath and a PC tension material. In addition to being protected against corrosion, it is integrated with the frame concrete through a sheath.

  Post-tension grout material injection is carefully performed so as not to create a void in the sheath, but depending on the case, clogging in the middle of the sheath, material separation of the grout material, pre-flow due to insufficient viscosity of the grout material, etc. As a result, a gap may remain in the sheath. In such a case, chloride ions generated by salt inflow from the ocean, spraying of antifreeze, etc. enter the voids, rust the PC tendon, and deteriorate the stress state due to damage of the PC tendon, The performance deterioration of the PC structure such as cracking of the concrete frame due to the expansion pressure due to the rusting of the PC tendon may occur.

  Also, during the construction of a new post-tension type PC structure, the PC tendon is left unprotected in a corrosive environment without being protected by the grout, and rusts. Even if the grout is injected later, the PC tendon It is also conceivable that the performance of the PC structure deteriorates due to the progress of corrosion.

  It is difficult to judge the state of grouting material not filled in existing PC structures and the state of rusting / deterioration of PC tendons by external observation of PC structures, and external deformations such as rust juice and cracks In many cases, it is not possible to confirm the presence of an unfilled portion of the grout material until the material becomes apparent. Therefore, when the grout material unfilled state can be confirmed, the rusting / deterioration of the PC tendon has already been considerably advanced.

  When the external deformation of the PC structure becomes apparent, the concrete is repaired and the grout material is reinjected into the space not filled with the grout material and repaired. Further, when it was discovered that there was an unfilled space for the grout material, reinjecting the grout material into the space was a conventional measure for processing. Regarding a technique for reinjecting grout material into an existing PC structure, a technique relating to securing an injection path and an injection method is known (see, for example, cited document 1).

  However, it is extremely difficult to guarantee that the grout material is completely filled into the unfilled space of the grout material under the condition that the grout material is not filled by re-injection of the grout material at a later date. Even if measures are taken, it cannot be said that it is 100% certain. If the grout material unfilled space is left again, there is a possibility that corrosion further proceeds.

  By the way, it is well known as a metal anticorrosion technique that a metal having a large tendency to ionize is effectively protected when its surface is subjected to a passivation treatment so that the corrosion rate is almost zero. In general, the metal passivation treatment is performed by, for example, immersing iron in a concentrated nitric acid solution or performing electrolysis using a metal such as nickel or cobalt as an anode (see, for example, Non-Patent Document 1).

  As described above, the PC tendon is protected against corrosion in a highly alkaline atmosphere, a technology for passivating the metal surface, and a technology for protecting the metal surface against corrosion by coating with a highly alkaline hydraulic substance. Is a contradictory technical idea and contradiction. Therefore, there has never been a technical idea for the passivation of the surface in the PC tension material.

  In addition, electrochemical means using a reference electrode or the like for corrosion prediction or corrosion detection of steel in concrete is also known (see, for example, Patent Documents 2, 3, and 4).

  In the case where the PC tension member is corroded in the unfilled space of the grout material in the sheath in the post-tension type existing PC structure, or in the sheath of the new post-tension type PC structure. In the case where the PC tendon has rusted before the injection, the research on the protection of the PC tendon by the contradictory technical idea has been repeated and the present invention has been created.

Japanese Patent Laid-Open No. 2005-023567 JP 2007-163324 A Japanese Patent No. 3847300 Japanese Patent No. 3205291

“Chemical Dictionary (Volume 7)”, Kyoritsu Publishing Co., Ltd., October 15, 1981, p. 911

  In the existing post-tension PC structure, the grout material is not completely filled in the sheath, the grout material unfilled space remains between the sheath and the PC tension material, and the corrosion degradation factor enters the PC tension. When the material rusted and deteriorated, it was not easy to stop the progress of rusting of the PC tendon and prevent the deterioration of the performance of the PC structure even if the grout material was reinjected. In addition, it is difficult to fill the grout material between the strands of the PC tendon material or the minute unfilled space of the grout material.

  In addition, in the new post-tension type PC structure, if the PC tension material rusts before the grout material is injected into the sheath, the progress of rusting of the PC tension material is stopped even if the grout material is injected. Thus, it is not easy to prevent the performance deterioration of the PC structure.

  The present invention aims to solve these problems.

  The first PC tension member corrosion inhibiting method of the present invention is a method for inhibiting corrosion of PC tension members of a post-tension type PC structure. A neutral to weakly alkaline rust inhibitor aqueous solution is supplied to the filling space to form a passive film on the surface of the PC tendon, then the aqueous solution is removed, and the grout material is filled into the space from which the aqueous solution has been removed. Features.

  The second PC tension member corrosion suppression method of the present invention is also used to suppress the corrosion of the PC tension member of the post-tension type PC structure. Water is supplied to the material unfilled space to remove or reduce chloride ions present in the sheath or rust layer, then the water is removed, and the water is removed from neutral to weakly alkaline rust prevention An aqueous agent solution is supplied to form a passive film on the surface of the PC tendon, then the aqueous solution is removed, and a grout material is filled in the space from which the aqueous solution has been removed.

  In these cases, it can be carried out by confirming that a passive film has been formed on the surface of the PC tendon by electrochemical measurement such as nomination of the PC tendon potential.

  Further, in each of the above methods, if a grout material mixed with a rust preventive agent is used as the grout material, the effect of inhibiting the corrosion of the PC tension material can be more reliably ensured. As the rust preventive agent, any rust preventive agent may be used as long as it does not significantly adversely affect the workability and durability of the grout material, such as lithium nitrite and calcium nitrite. Nitrite and the like can be used.

  In addition, the grout material unfilled space referred to in the present invention is a space remaining between the sheath and the PC tendon material in the post-tension type existing PC structure, or before filling the grout material in the post-tension type PC structure. The space between the sheath and the PC tendon.

  The concentration of the rust preventive aqueous solution is determined by the degree of corrosion of the PC tendon, the presence or absence of water filling, the time determined by the construction restrictions that allow the rust preventive aqueous solution to be held in the voids in the sheath, and the like. More specifically, for example, the concentration of the rust inhibitor aqueous solution may be increased as the degree of corrosion of the PC tendon progresses or as the holding time decreases. In addition, when water is filled prior to filling with the rust inhibitor aqueous solution as in the second method, chloride ions present in the sheath or rust layer are removed or reduced when the rust inhibitor aqueous solution is filled. Therefore, the concentration of the rust inhibitor aqueous solution can be reduced.

  In terms of the rust prevention effect, it is desirable that the amount of the rust prevention agent mixed in the grout material to be filled is large. The reason is that when the corrosion of the passivated PC tendon progresses again due to an unpredictable cause, the progress of the PC tendon corrosion can be suppressed by the rust inhibitor supplied from the hardened grout material. It is.

  As described above, the amount of the rust preventive agent mixed in the grout material may be determined in consideration of construction performance such as pot life and viscosity of the grout material, or expression strength.

In addition, as what can be used as a rust inhibitor contained in a neutral to weak alkaline rust inhibitor aqueous solution or a rust inhibitor mixed in a grout material, for example,
Anode type rust preventive agent: chromate, nitrite Cathode type rust preventive agent: carbonate, phosphate, silicate, polyphosphate Adsorption type rust preventive: organic polymer compound and the like.

  According to the present invention, when the corrosion of the PC tendon of the post-tension type PC structure is suppressed, the neutral to weak alkaline rust inhibitor aqueous solution is first filled in the grout material unfilled space in the sheath. The rust preventive aqueous solution is supplied to the space between the strands of the PC steel, which is hard to be filled with the grout material, and even to the fine unfilled space of the grout material, and a completely new film is formed that forms a passivating film on the surface of the PC tendon material. A certain corrosion control effect can be expected by the technical idea.

  Moreover, even if the steel material corrosion factor invades for some reason after filling the grout material, the PC tendon material is double protected against corrosion by using the grout material mixed with the rust preventive agent.

It is a schematic diagram explaining the hole-drilling process in the corrosion suppression method of the PC tendon which is one Embodiment of this invention. It is a schematic diagram explaining the aqueous solution injection | pouring process in the corrosion suppression method of the PC tendon which is one Embodiment of this invention. It is a longitudinal cross-sectional view of the sheath which has the grout material unfilled space shown in FIG. It is the A section enlarged view shown in FIG. It is a schematic diagram explaining the measuring method of the electric potential of PC steel materials. It is a graph which shows the time-dependent change of the steel material electric potential when the corroded PC steel material is immersed in the solution of various concentration. It is a schematic diagram explaining the grout material injection | pouring process in the corrosion suppression method of the PC tendon which is one Embodiment of this invention. It is a graph which shows the time-dependent change of the macrocell current which arises in the boundary of the grout material filling space and the part which grout material was reinjected into the grout material unfilled space.

  Embodiments of the present invention will be described below with reference to the drawings.

  Here, the form for implementing this technique to the existing post tension system PC structure is demonstrated.

  FIG. 1 is a schematic diagram for explaining a drilling step in a method for inhibiting corrosion of a PC tendon which is an embodiment of the present invention.

  FIG. 1 shows a grout material unfilled space 110 in the existing PC structure 100. The unfilled space 110 of the grout material is a void remaining in the sheath 10 due to, for example, blockage in the middle of the sheath 10, material separation of the grout material 30, pre-flow due to insufficient viscosity of the grout material 30, and the like. is there. Moreover, the sheath 10 used here is a sheath formed by winding a strip-shaped steel plate spirally without a gap.

  First, the position of the sheath 10 in the existing PC structure 100 and the grout material unfilled space 110 in the sheath 10 are detected using a general nondestructive inspection technique.

  Next, as shown in FIG. 1, the concrete of the existing PC structure 100 is drilled toward the grout material unfilled space 110, and the sheath 10 between the drilled hole 120 and the grout material unfilled space 110. Is deleted. Thereafter, the corrosion state of the PC steel material 20 and the sheath 10 is confirmed, and if it is corroded, an aqueous solution containing nitrite is injected from the drilled hole 120. This aqueous solution containing nitrite is an example of the neutral to weak alkaline rust inhibitor aqueous solution referred to in the present invention. Here, a lithium nitrite aqueous solution is used as the aqueous solution containing nitrite.

  FIG. 2 is a schematic diagram for explaining an aqueous solution injection step in the method for inhibiting corrosion of a PC tendon which is an embodiment of the present invention. 3 is a longitudinal sectional view of the sheath 10 having the grout material unfilled space 110 shown in FIG. 2, and FIG. 4 is an enlarged view of a portion A shown in FIG.

  As shown in FIG. 3, the aqueous solution 200 containing nitrite injected into the grout material unfilled space 110 from the drilled holes 120 reaches the space 111 between the strands of the PC steel material 20 and the minute grout material unfilled space 112. Immerse and spread throughout the grout material unfilled space 110. Further, as shown in FIG. 4, nitrite ions 210 enter the corroded PC steel 20 and the rust layer of the sheath 10.

  Here, the corrosion of the PC steel material 20 and the sheath 10 is mainly caused by the chloride ions 40 generated due to the salinity coming from the ocean, the spraying of the antifreezing agent, and the like entering the unfilled space 110 of the grout material.

  As the aqueous solution 200 containing nitrite enters the grout material unfilled space 110, chloride ions 40 existing in the space 110 are dissolved in the injected aqueous solution 200 containing nitrite, as shown in FIG. To do.

  Further, the nitrite contained in the aqueous solution 200 forms a passive film on the surface of the PC steel material 20 and the inner surface of the sheath 10 in the grout material unfilled space 110.

  Note that the concentration of nitrite in the aqueous solution 200 injected into the grout material unfilled space 110 is determined in consideration of the degree of corrosion of the PC steel material 20 and the sheath 10, the construction period, and the like. More specifically, for example, when the PC steel material 20 or the sheath 10 is greatly corroded or when the construction period is short, the aqueous solution 200 containing a higher concentration of nitrite is used.

  Next, it is confirmed whether or not a passive film is formed on the surface of the PC steel material 20. Here, the formation of the passive film is confirmed by measuring the potential of the PC steel material 20 as follows.

  FIG. 5 is a schematic diagram for explaining a method for measuring the potential of the PC steel material 20.

  When measuring the potential of the PC steel material 20, as shown in FIG. 5, a verification electrode 300 for measuring the potential of the PC steel material 20 is installed in the drilled hole 120, and one end of the electric wire 310 is connected to the inner surface of the sheath 10. Then, the drilled hole 120 is sealed with a lid 320, and an aqueous solution 200 containing nitrite is injected. Thereafter, the potential of the PC steel material 20 is measured. As will be described with reference to FIG. 6, it is possible to grasp that the PC steel material 20 is reliably passivated by measuring the potential of the PC steel material 20.

  FIG. 6 is a graph showing the change over time in the steel material potential when the corroded PC steel material 20 is immersed in solutions of various concentrations. The horizontal axis of this graph represents the immersion time (hour), and the vertical axis represents the potential (mV, SCE).

  Here, the change of the natural potential to noble (minus minus) means that the corrosion of the PC steel material 20 is suppressed and passivated. As shown in FIG. 6, it can be seen that when immersed in an aqueous solution 200 containing nitrite (here, lithium nitrite), it is passivated. In addition, it can be seen that it is passivated earlier by immersion in an aqueous solution 200 containing a higher concentration of nitrite.

  FIG. 6 also shows the change over time in the steel material potential when the corroded PC steel material 20 is immersed in a saturated calcium hydroxide aqueous solution. This simulates the environment in concrete, and as shown in FIG. 6, it can be seen that such a PC steel material 20 is placed in a corrosive environment.

  Thus, after confirming formation of a passive film by measuring the electric potential of PC steel material 20, aqueous solution 200 containing nitrite is removed. At this time, the chloride ions 40 (see FIG. 4) existing in the grout material unfilled space 110 dissolved in the aqueous solution 200 are also removed.

  FIG. 7 is a schematic view for explaining a grout material injection step in the PC tension member corrosion inhibiting method according to an embodiment of the present invention.

  After the aqueous solution 200 containing nitrite is removed, a grout material 400 containing nitrite 400 is poured into the grout material unfilled space 110 as shown in FIG. Since the existing method is sufficient for the method of injecting the grout material 400 containing nitrite, detailed description thereof is omitted here.

  The concentration of nitrite added to the grout material 400 may be determined in consideration of the degree of corrosion of the PC steel material 20 and the sheath 10, the performance of the grout material 400, and workability. More specifically, for example, when the PC steel material 20 or the sheath 10 is greatly corroded, the grout material 400 containing a higher concentration of nitrite is used. However, it is known that in the grout material 400 to which nitrite is added, the fluidity deterioration with time tends to be faster as the grout material 400 contains a high concentration of nitrite. Therefore, when the grout material 400 containing a high concentration of nitrite is used, the grout material 400 is constructed in consideration of the pot life and viscosity.

  FIG. 8 is a graph showing the change over time of the macrocell current generated at the boundary between the grout material filling space and the portion where the grout material 400 is injected into the grout material unfilled space 110. The horizontal axis of this graph indicates time (days), and the vertical axis indicates macro cell current (mA).

Here, a large macro cell current means that the corrosion rate generated at the boundary is large. As shown in FIG. 8, it can be seen that by adding 6 kg / m ³ or more of nitrite to the grout material, the macrocell current becomes very small and the corrosion occurring at the boundary is suppressed.

  As described above, according to the present embodiment, when the corrosion of the PC steel material 20 of the post-tension type PC structure is suppressed, the aqueous solution 200 containing nitrite is added to the grout material unfilled space 110 in the sheath 10. By first filling, the aqueous solution 200 is also supplied between the strands 111 of the wire from the PC steel which is hard to be filled with the grout material and the minute unfilled space 112 of the grout material, and a passivating film is generated on the surface of the PC steel material 20 With this completely new technical idea, it is possible to expect a certain corrosion inhibiting effect.

  Moreover, even if a steel material corrosion factor invades for some reason after filling with the grout material 400, since the grout material 400 mixed with a rust preventive agent is used, the PC steel material 20 is double protected against corrosion. Is done.

  Next, another embodiment of the present invention will be described.

  In another embodiment described below, a water injection step is provided before the aqueous solution injection step described with reference to FIG.

  Hereinafter, the same elements as those in the above-described embodiment will be denoted by the same reference numerals, description thereof will be omitted, and only differences from the above-described embodiment will be described.

  The concrete of the existing PC structure 100 is drilled toward the grout material unfilled space 110, and the sheath 10 between the drilled hole 120 and the grout material unfilled space 110 is deleted. Thereafter, the corrosion state of the PC steel material 20 and the sheath 10 is confirmed, and if it is corroded, water is injected from the drilled hole 120 prior to injection of the aqueous solution containing nitrite. This water is an example of water referred to in the present invention.

  The water injected into the grout material unfilled space 110 from the drilled hole 120 soaks into the space 111 between the strands of the PC steel material 20 and the minute grout material unfilled space 112 and reaches the entire grout material unfilled space 110. . And the chloride ion 40 which exists in the grout material unfilled space 110 melt | dissolves in the inject | poured water.

  Thereafter, the water is removed. At this time, the chloride ions 40 existing in the grout material unfilled space 110 dissolved in the water are removed.

  Thereafter, an aqueous solution 200 containing nitrite is injected into the space from which water has been removed.

  Hereinafter, as in the above-described embodiment, after removing the aqueous solution 200 containing nitrite, a grout material 400 containing nitrite is injected into the grout material unfilled space 110 as shown in FIG.

  According to another embodiment described above, since water is injected from the drilled hole 120 prior to the injection of the aqueous solution 200 containing nitrite, chloride ions 40 existing in the grout material unfilled space 110 are injected. There is a high degree of certainty to remove. Also, chloride ions present in the sheath 10 and in the rust layer are removed or reduced by the water injected / removed prior to the injection of the aqueous solution 200 containing nitrite when the aqueous solution 200 containing nitrite is filled. Therefore, the concentration of nitrite can be reduced.

  In each of the above-described embodiments, the PC structure referred to in the present invention has been described with reference to an example of an existing PC structure. However, the PC structure referred to in the present invention is not limited to this, and is newly installed. It may be a PC structure.

  Moreover, in each embodiment mentioned above, although the rust preventive agent said to this invention demonstrated and demonstrated the example which is nitrite, the rust preventive agent said to this invention is not restricted to this, For example, chromium Acid salts, carbonates, phosphates, silicates, polyphosphates, organic polymer compounds, and the like may be used.

  In each of the above-described embodiments, the grout material referred to in the present invention has been described with reference to an example of a grout material containing nitrite. However, the grout material referred to in the present invention is not limited to this, A grout material containing no nitrate may be used.

DESCRIPTION OF SYMBOLS 100 Existing PC structure 110 Grout material unfilled space 111 Between strands 112 Minute grout material unfilled space 120 Hole 10 Sheath 20 PC steel material 30 Grout material 40 Chloride ion 200 Aqueous solution containing nitrite 210 Nitrite ion 300 Reference electrode 310 Electric wire 320 Lid 400 Grout material containing nitrite

Claims (5)

In order to suppress the corrosion of PC tension material that has already rusted in the grout material unfilled space of the existing PC structure of the post tension system, neutral to weak alkaline rust prevention in the grout material unfilled space in the sheath Reducing chloride ions in the rust layer by supplying an aqueous agent solution, forming a passive film on the surface of the PC tendon, then removing the aqueous solution and filling the space from which the aqueous solution has been removed with a grout material A method for inhibiting corrosion of PC tendons characterized by the following. In order to suppress the corrosion of the PC tension material that has already rusted in the grout material unfilled space of the existing PC structure of the post-tension method, water is supplied to the grout material unfilled space in the sheath. The chloride ions present in the rust layer are removed or reduced, the water is then removed, and a neutral to weak alkaline rust inhibitor aqueous solution is supplied to the space from which the water has been removed. A method for inhibiting corrosion of a PC tendon, comprising reducing ion ions, forming a passive film on the surface of the PC tendon, removing the aqueous solution, and then filling the space from which the aqueous solution has been removed with a grout material.   The PC tension according to claim 1 or 2, wherein the formation of a passive film on the surface of the PC tension material is confirmed by electrochemical measurement such as nobleness of the PC tension material potential. Material corrosion control method.   The method for inhibiting corrosion of a PC tendon material according to any one of claims 1 to 3, wherein a grout material mixed with a rust inhibitor is used as the grout material.   The method for inhibiting corrosion of a PC tendon according to claim 4, wherein nitrite is used as the rust inhibitor.

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