JP5706281B2 - Reinforcing method with suppression of deterioration of concrete structure - Google Patents

Description

  The present invention relates to a reinforcing method with suppression of deterioration of a concrete structure.

  In recent years, there has been a tendency to increase repair and reinforcement work aimed at restoring and improving the function of existing concrete structures. Remove the old part of the existing concrete surface and apply mortar etc. to the removed part. A reinforcing method has attracted attention (see, for example, Patent Document 1).

  In the reinforcing method described in Patent Document 1, the adhesion between the concrete surface of the existing concrete structure and the newly applied mortar is improved by using a polymer cement mortar containing a polymer in the newly applied mortar. .

JP 2002-81041 A

  However, when the reinforcing bars disposed in the existing concrete structure have deteriorated over time, the deteriorated reinforcing bars must be repaired. For example, in the case where rust is generated in the reinforcing bars disposed in the existing concrete structure, the following steps are required to repair the reinforcing bars in addition to reinforcing the existing concrete structure. That is, a step of removing a part of an existing concrete structure, a step of removing rust generated on the surface of a reinforcing bar disposed in the existing concrete structure, and a step of forming a protective film on the surface of the reinforcing bar from which the rust has been removed And a step of covering the reinforcing bar on which the protective film is formed with concrete.

  Therefore, if the reinforcing bars installed in the existing concrete structure have deteriorated over time, the reinforcement work for the existing concrete structure becomes complicated and the reinforcement work is prolonged due to an increase in the repairing process. At the same time, there was a problem that the cost for the reinforcement work increased.

  Therefore, the present invention has been devised to solve the above-described problem, and it is possible to reinforce an existing concrete structure and to deteriorate a concrete structure capable of repairing a reinforcing bar embedded in the existing concrete. It aims at providing the reinforcement method with suppression.

In order to solve the above-mentioned problem, the invention according to claim 1 is a method of removing a deteriorated part of an existing concrete surface or an aging part such as a foreign object in a reinforcement of an existing concrete structure provided with a reinforcing bar inside. a processing step, the reinforcing rebar fixation step for fixing the reinforcing rebar with an anchor attached to a position away from the reinforcing rebar engaging said reinforcing rebar through brackets to the existing concrete surface, wherein A polymer cement mortar application step for applying a polymer cement mortar so as to cover the reinforcing reinforcing bar and the existing concrete surface, and a crack followability larger than the polymer cement mortar surface on the polymer cement mortar surface to which the polymer cement mortar is applied coating a highly elastic special mortars with has a coating process, wherein the anchor Is a twist and lock anchor, screw the axis of the anchor is screwed, the polymer cement mortar, was reinforced method involving the deterioration suppression of the concrete structure, characterized by containing nitrite .

  The invention according to claim 2 is the reinforcing method with the suppression of deterioration of the concrete structure according to claim 1, wherein the polymer cement mortar is a mixture of short fibers, and the high elasticity special mortar is It was decided to have a greater crack followability than polymer cement mortar.

  The invention according to claim 3 is the reinforcing method for suppressing deterioration of the concrete structure according to claim 1 or 2, wherein the nitrite is sodium nitrite.

  According to the first aspect of the present invention, the reinforcing steel bars are disposed on the existing concrete surface and the existing concrete surface is covered with the polymer cement mortar, so that the existing concrete can be reinforced. In addition, since polymer cement mortar contains nitrite, the nitrite penetrates into the existing concrete and forms a protective film on the surface of the reinforcing steel in the existing concrete. First, various deterioration symptoms can be suppressed. It is also possible to reduce the cost and extend the life.

  Further, according to the invention of claim 2, short fibers are mixed into the polymer cement mortar, and the use of the high-elastic special mortar suppresses cracking of the concrete surface after construction, so that salt rain is externally applied. Etc. can be suppressed.

  According to the invention described in claim 3, the use of sodium nitrite as the nitrite can reduce the reinforcement cost.

  In addition, according to the invention described in claim 4, since the rotation-fixed anchor is used as the anchor for fixing the reinforcing reinforcing bars, the existing concrete damage can be reduced and the removal can be easily performed.

It is a figure which shows the structure of the existing concrete structure of a bridge deck. It is the schematic which shows the reinforcement part 50 of the bridge deck reinforced by the method of this embodiment. It is a flowchart which shows the reinforcement process of the concrete structure which concerns on this embodiment. It is a figure which shows the reinforcement process of the concrete structure which concerns on this embodiment. It is a figure which shows the example of arrangement | positioning of the reinforcing bar which concerns on this embodiment. It is a figure which shows the anchor which concerns on this embodiment. It is explanatory drawing which shows the generation | occurrence | production mechanism of rust. It is a figure which shows the result of the bending strength test of the concrete structure reinforced by this embodiment.

  Next, modes for carrying out the invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the accompanying drawings. In this embodiment, after reinforcing reinforcing bars are laid on the floor bottom of an existing concrete structure such as a bridge girder or beam, polymer cement mortar (Polymer-Cement Mortar: PCM) is sprayed or thickened by trowel coating. An example of reinforcing an existing concrete structure will be described.

  FIG. 1 is a view showing a structure of a reinforcing bar 11 in an existing concrete structure 10 of a bridge floor slab.

  FIG. 2 is a schematic view showing a reinforcing part 50 of a bridge floor slab reinforced by the method of the present embodiment, and the reinforcing part 50 includes a reinforcing bar 30.

  Next, with reference to FIG. 3, a reinforcing method with the suppression of deterioration of the concrete structure according to the present embodiment will be described in detail. In addition, this embodiment demonstrates the example which performs bridge floor slab lower surface reinforcement.

  First, in step S101, a ground processing step is performed. In this step, as shown in FIG. 4A, prior to reinforcement of the floor slab surface 10a (corresponding to the “existing concrete surface” of the present invention) 10a of the existing concrete structure 10, Clean the water with high pressure water and remove the deteriorated parts of the existing concrete surface and aging parts such as foreign objects. In this ground treatment process, the rust of the reinforcing bars in the existing concrete structure 10 is removed by performing cleansing, and the adhesion of the reinforcing material to the floor slab surface 10a of the existing concrete structure 10 is enhanced by washing with high pressure water. It is done. At this time, if there is an inconvenience such as an environmental problem, the deteriorated portion and dirt on the surface to be a vacuum blast are completely removed, and the convex portion such as the mold step is removed with a chisel or the like.

  Next, in step S102, a first polymer cement mortar spraying (first primer coating) step is performed. In this step, as shown in FIG. 4B, a polymer cement paste 20 is applied as an undercoat material to the floor slab surface 10a of the existing concrete structure 10 subjected to the base treatment. For application of the polymer cement paste 20, a ricin gun or a brush is used.

  As the polymer cement paste 20 described above, for example, an admixture composed of an acrylic polymer dispersion, Fremix powder composed of ordinary Portland cement, fine aggregate, and various additives, nitrite (for example, nitrous acid) A mixture of (sodium nitrate) is used. In addition, for example, CP-A main material is used for the mixed solution, and CP-A powder is used for the Fremix powder.

At that time, 6.5 kg of the mixed liquid (CP-A main material), 19.9 kg of Fremix powder (CP-A powder), and 0.1 kg of nitrite are mixed to obtain a polymer cement paste 20. . In this case, the specific gravity of the polymer cement paste 20 is 1800 kg / m ³ . The coating amount is 1.8 kg / m ² .

  By performing the first undercoat material application step, it is possible to increase the adhesive force between the floor slab surface 10a of the existing concrete structure 10 subjected to the base treatment and the polymer cement mortar 22 serving as an intermediate coat material to be described later.

  Next, in step S103, a reinforcing bar fixing (rotation fixed type anchor) step is performed. In this step, first, as shown in FIG. 4 (c), the reinforcing reinforcing bars 30 are temporarily fixed to the floor slab surface 10 a of the existing concrete structure 10. At this time, the reinforcing reinforcing bars 30 are thermally welded and assembled in a lattice shape, thereby facilitating the temporary fixing operation.

  Next, as shown in FIGS. 4D and 5, the temporarily fixed reinforcing bar 30 is fixed to the reinforcing bar 30 with a predetermined pitch of 300 mm using an anchor 31 (fixing bracket), for example. As the anchor for fixation, a rotary anchor is used to minimize the deterioration of the existing floor slab concrete.

The force against the load of the existing concrete structure 10 (hereinafter referred to as “loading force”) can be set by the pitch and number of reinforcing bars 30. In the present embodiment, for example, 16 / m ² anchors 31 are used to fix the reinforcing reinforcing bars 30.

  As shown in FIG. 6, the anchor 31 includes a cylindrical shaft core 31a, a head portion 31c formed at one end of the shaft core 31a via a handle portion 31b, and screws screwed on the surface of the shaft core 31a. Part 31d. The head 31c of the anchor 31 is formed in a polygonal shape, and an instrument such as an impact driver can be used to attach the anchor 31, so that the anchor 31 can be attached quickly. Further, since the anchor 31 has the above-described configuration, the anchor 31 can be removed when the existing concrete structure 10 is reconstructed.

  Next, in step S104, a second polymer cement mortar spraying (second primer coating) step is performed. In this step, a polymer cement paste (not shown) is applied to the floor slab surface 10a of the existing concrete structure 10 after the reinforcing reinforcing bars 30 are fixed.

  Examples of the polymer cement paste (not shown) include an admixture composed of an acrylic polymer dispersion, Fremix powder composed of ordinary Portland cement, fine aggregate, and various additives, and nitrite ( For example, a mixture of sodium nitrite) is used. In addition, for example, CP-A main material is used for the mixed solution, and CP-A powder is used for the Fremix powder.

At that time, 6.5 kg of the mixed liquid (CP-A main material), 19.9 kg of Fremix powder (CP-A powder), and 0.1 kg of nitrite are mixed to obtain a polymer cement paste 20. . In this case, the specific gravity of the polymer cement paste 20 is 1800 kg / m ³ . The coating amount is 1.8 kg / m ² .

  The purpose of increasing the adhesion between the floor slab surface 10a of the existing concrete structure 10 after fixing the reinforcing reinforcing bars 30 and the polymer cement mortar 22 (described later) as an intermediate coating material by performing the second primer coating step. And spray CP-A (priming material).

  Next, in step S105, a polymer cement mortar iron coating (intermediate coating material coating) step is performed. In this step, as shown in FIG. 4E, polymer cement mortar 22 is applied as an intermediate coating material using a spraying tool such as a trowel. The application of the intermediate coating material is divided into several times until reaching a predetermined thickness (for example, 21 mm). The thickness increase per layer is about 10 mm.

  As the polymer cement mortar 22 described above, for example, an admixture composed of an acrylic polymer dispersion, Fremix powder composed of ordinary Portland cement, fine aggregate, and various additives, nitrite (for example, nitrous acid) A mixture of (sodium nitrate) is used. In addition, for example, CP-E main material is used for the mixture, and CP-E powder is used for the Fremix powder.

At that time, 3.1 kg of admixture (CP-E main material), 19.9 kg of Fremix powder (CP-E powder), and 0.1 kg of nitrite are mixed to form polymer cement mortar 22. . In this case, the specific gravity of the polymer cement mortar 22 is 2060 kg / m ³ . The coating amount is 43.26 kg / m ² .

  As described above, in the present embodiment, the reinforcing steel bar 30 and the polymer cement mortar 22 are integrally formed so that the load applied to the existing concrete structure can be received by the reinforcing steel bar 30 and the polymer cement mortar 22. This makes it possible to improve the load-bearing force.

  Next, in step S106, a vinylon mesh attaching step is performed. In this step, as shown in FIG. 4 (f), for the purpose of suppressing cracking, a vinylon mesh 40 is applied simultaneously with application of a polymer cement paste (not shown) as an undercoat material.

  Examples of the polymer cement paste (not shown) include an admixture composed of an acrylic polymer dispersion, Fremix powder composed of ordinary Portland cement, fine aggregate, and various additives, and nitrite ( For example, a mixture of sodium nitrite) is used. In addition, for example, CP-A main material is used for the mixed solution, and CP-A powder is used for the Fremix powder.

At that time, 6.5 kg of admixture (CP-A main material), 19.9 kg of Fremix powder (CP-A powder), and 0.1 kg of nitrite are mixed to form polymer cement mortar 22. . In this case, the specific gravity of the polymer cement paste is 1800 kg / m ³ . The coating amount is 1.8 kg / m ² .

  Next, in step S107, a highly elastic special mortar coating (coating material coating) step is performed. In this step, high-elastic special mortar 24 is applied as a top coating material. This highly elastic special mortar 24 is uniformly applied by using a tool such as a trowel.

  As the high-elasticity special mortar 24 described above, for example, an admixture composed of an acrylic polymer dispersion, and Fremix powder composed of ordinary Portland cement, fine aggregate, and various additives are used. Note that, for example, a CP coat main material is used for the mixed solution, and CP coat powder is used for the Fremix powder.

At that time, the mixed liquid (CP coat main material) is mixed at a ratio of 18.0 kg and Fremix powder (CP coat powder) is mixed at a ratio of 18.0 kg to obtain a highly elastic special mortar 24. The coating amount is 1.7 kg / m ² .

Next, in step S108, a water-based acrylic urethane resin is applied. In this step, for example, 0.3 kg / m ^{2 of} an aqueous acrylic urethane resin is uniformly applied using a tool such as a roller brush.

  Through the above-described steps, the existing concrete structure 10 is reinforced and the reinforcing portion 50 is completed.

(Rebar corrosion mechanism)
Next, a mechanism for preventing corrosion of reinforcing bars disposed in the existing concrete structure 10 reinforced by the above-described reinforcing method will be described.

  In describing the mechanism of corrosion prevention of reinforcing bars, first, the mechanism of corrosion of reinforcing bars will be described. In addition, FIG. 7 is explanatory drawing which showed the generation | occurrence | production mechanism of rust.

  The existing concrete structure 10 has a property of being highly alkaline, for example, pH = 12 or more. Due to the highly alkaline nature of the existing concrete structure 10, a passive film is formed on the surface of the reinforcing steel 11 of the existing concrete disposed in the existing concrete structure 10. This passive film functions as a protective film that protects the existing concrete rebar 11 from being oxidized and generating rust.

  However, when the properties of the existing concrete structure 10 are neutralized and, for example, pH = 10 or less, the function as a protective film of the passive film formed on the surface of the reinforcing steel 11 of the existing concrete is deteriorated. As a result, the surface of the existing concrete reinforcing bar 11 is oxidized, and rust is generated on the surface of the existing concrete reinforcing bar 11. Thus, the existing concrete rebar 11 corrodes.

Further, even when the existing concrete structure 10 is not neutralized, for example, when salt water is mixed in the existing concrete structure 10 by rainwater penetrating into the existing concrete structure 10, Due to the mixed chloride ions (Cl ⁻ ) of the salt, the passive film formed on the surface of the reinforcing steel 11 of the existing concrete is partially destroyed, and rust is generated at the part where the passive film is destroyed. Thus, the existing concrete rebar 11 corrodes.

(Rebar corrosion prevention mechanism)
Next, a mechanism for preventing corrosion of the reinforcing bars will be described. Hereinafter, an example will be described in which corrosion of reinforcing steel bars is prevented by regenerating a passive film destroyed by chloride ions (Cl ⁻ ) using nitrite ions (NO ₂ ⁻ ).

First, the mechanism by which the passive film is destroyed will be described.
The passive film is formed using iron oxide (Fe ₂ O ₃ ) as a component. Then, chloride ions (Cl ⁻ ) that destroy the passive film are formed on the surface of the reinforcing steel 11 of the existing concrete and the reinforcing steel 11 of the existing concrete, as shown in the formula (1). A passive film made of oxide (Fe ₂ O ₃ ) is dissolved.

[Formula 1]
Fe ²⁺ + 2Cl ⁻ → FeCl ₂

In this way, chloride ions (Cl ⁻ ) decompose iron oxide (Fe ₂ O ₃ ) that becomes a passive film, and destroy the passive film formed on the surface of the reinforcing steel 11 of the existing concrete. .

Next, the regeneration mechanism of the passive film using nitrite ions (NO ₂ ⁻ ) will be described.
Nitrite ions (NO ₂ ⁻ ) react with iron ions (Fe ₂ ⁺ ) generated by the decomposition of iron oxide (Fe ₂ O ₃ ) as shown in formula (2).

[Formula 2]
Fe ₂ ⁺ + 2OH ⁻ + 2NO ₂ ⁻ → Fe ₂ O ₃ + H ₂ O + 2NO

In this way, iron oxide (Fe ₂ O ₃ ) that becomes a passive film is regenerated by nitrite ions (NO ₂ ⁻ ), and the passive film is also regenerated.

Chloride ion (Cl ^-) and nitrite ion (NO ₂ ^-) and if there are both a chloride ion regeneration by (Cl - ^-) and the destruction of the passive film by the nitrite ion (NO ₂₎ And competitive reaction. At this time, by setting the molar ratio of nitrite ions (NO ₂ ⁻ ) to chloride ions (Cl ⁻ ) to be 0.6 or more, a more dense passive film can be regenerated, and chloride ions (Cl ^-) destruction by can be prevented.

  Moreover, this molar ratio is high in the case of a rusted reinforcing bar or when the concrete is neutralized, and the molar ratio needs to be 1.0 or more.

Moreover, existing concrete rebar 11 partially corroded, i.e., rust in a part of the surface nitrite reinforcing bars 11 of the existing concrete generated (NO ₂ ^-) in the case of adding the nitrite ions (NO ₂ ^-) reacts with iron ions (Fe _two ⁺⁾ of corroded portion not rebar 11, reproduces the passive film.

However, nitrite ion (NO ₂ ⁻ ) has a function of suppressing the progress of rust, but does not have a function of removing rust (for example, red rust) generated on the surface of the reinforcing steel 11 of the existing concrete. It is necessary to add nitrite ions (NO ₂ ⁻ ) before rust is generated on the surface of the reinforcing bars 11.

  FIG. 8A is a diagram showing the results of a bending strength test of a concrete structure that is not reinforced according to the present embodiment, and FIG. 8B is a bending strength of the concrete structure that is reinforced according to the present embodiment. It is a figure which shows the result of a test. In the figure, the horizontal axis represents displacement (mm) due to deflection, and the vertical axis represents load (kN).

  As is clear from these figures, the maximum load of the concrete structure reinforced by the present embodiment is 117 kN, and the strength is about 77.2 kN compared to the maximum load of the non-reinforced concrete structure. It became 2.05 times.

  As described above, according to the reinforcing method with the suppression of deterioration of the existing concrete structure according to the present embodiment, the reinforcing bars 30 are disposed on the floor slab surface 10a of the existing concrete structure 10, and the polymer cement mortar 22 is provided. Since the floor slab surface 10a is covered by this, the existing concrete structure 10 can be reinforced. Since the polymer cement mortar 22 contains nitrite, the nitrite penetrates into the existing concrete structure 10 and forms a protective film on the surface of the reinforcing bar 11 in the existing concrete structure 10. Various deterioration symptoms can be suppressed, including corrosion of the reinforcing bars disposed in the interior 10. It is also possible to reduce the cost and extend the life.

  In addition, by mixing short fibers into the polymer cement mortar 22 and using a highly elastic special mortar having crack following ability as a finishing material, cracking of the floor slab surface 10a of the existing concrete structure 10 after construction is suppressed, It is possible to suppress adverse effects such as salt rain from the outside.

  The short fiber used here refers to a synthetic fiber having a fiber length of 5 to 15 mm. Preferably, hydrophilic short fibers are used. Specifically, nylon fibers such as nylon 6 can be suitably used.

  Since such hydrophilic short fibers are excellent in dispersibility during kneading, the polymer cement mortar 22 can be made uniform and stable. Moreover, since it is excellent also in water retention, drying at the time of construction can be prevented.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this one embodiment.

DESCRIPTION OF SYMBOLS 10 Existing concrete structure 10a Floor slab surface 11 Reinforcement 20 Polymer cement paste 22 Polymer cement mortar 24 High elastic special mortar 30 Reinforcing reinforcement 31 Anchor 31a Shaft core 31b Handle 31c Head 31d Screw part 40 Vinylon mesh 50 Reinforcement part

Claims (3)

In reinforcing existing concrete structures with reinforcing bars inside,
A ground treatment process that removes the deteriorated part of the existing concrete surface and aging parts such as foreign matters, and performs the ground treatment,
Reinforcing rebar to the existing concrete surface, a reinforcing rebar fixation step for fixing the reinforcing rebar with an anchor attached to a position apart from said reinforcing rebar via the bracket that engages the reinforcing reinforcing bar ,
A polymer cement mortar application step of applying a polymer cement mortar so as to cover the reinforcing reinforcing bar and the existing concrete surface, respectively;
Coating the polymer cement mortar surface to which the polymer cement mortar has been applied with a high elasticity special mortar having a larger crack followability than the polymer cement mortar surface,
The anchor is a rotation-fixed anchor, and a screw is screwed on an axis of the anchor,
The polymer cement mortar contains nitrite. A reinforcing method with the suppression of deterioration of a concrete structure. The polymer cement mortar is a mixture of short fibers,
The reinforcement method with the suppression of deterioration of the concrete structure according to claim 1, wherein the high-elasticity special mortar has a larger crack followability than the polymer cement mortar. The reinforcing method with suppression of deterioration of a concrete structure according to claim 1 or 2, wherein the nitrite is sodium nitrite.

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