JP2005281037A - Conductive polymer cement mortar and protective material for electrolytic protection using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive cement mortar having excellent conductivity, improved sticking property to concrete and excellent workability, particularly capable of reducing the resistivity and preventing inactivation of an anode in an electrolytic protection method of a concrete structure, and to provide an anode protective material for electrolytic protection using the conductive cement mortar. <P>SOLUTION: The conductive cement mortar contains cement, lithium nitrite, a cement mixing retarder, a synthetic surfactant-based foaming agent and a cement mixing polymer. The cement mixing polymer having ≥0.3 μm particle diameter is used. The conductive polymer cement mortar is used as the anode protective material in the electrolytic protection method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a conductive polymer cement mortar and a protective material for anticorrosion using the mortar, and particularly to a polymer cement mortar having excellent conductivity, high strength and improved workability, and the mortar. It relates to the protective material for anticorrosion.

When a steel material such as a reinforcing bar in a reinforced concrete structure is exposed to a state of a certain salt concentration or more, a corrosion battery is generated, and an electric corrosion of the reinforcing bar in the anode portion is generated.
As a means to prevent the corrosion of reinforcing bars induced by the occurrence of such corrosion batteries, an anti-corrosion method that suppresses the corrosion reaction of steel in concrete by continuing to flow current from the anode installed on the concrete surface to the reinforcing bars in the concrete Is recommended and is used as one of the repair methods for reinforced concrete structures.

However, when corrosion protection is applied to reinforcing steel bars in concrete, which has a relatively high resistivity, the anode current required for corrosion protection decreases with the passage of time in the above galvanic anode method. It was difficult to maintain an effective potential difference.
As an anode material used in the cathodic protection method, a metal such as Ti is used. After this anode is installed on the surface of a reinforced concrete structure, the anode is reduced in resistivity and inactivated. In the case of the anticorrosion of the reinforcing bars in the concrete, it is necessary to cover the periphery of the anode with a protective material for protecting the performance of the anode.

The performance required as a protective material for the anode used in such an anticorrosion method is to maintain a higher electrical conductivity for a long time than the concrete of the concrete structure.
Further, in the cathodic protection method, an anode is provided on the concrete surface of the concrete structure, and the anode is installed and protected, so that a protective material having excellent adhesion to concrete is required.
A polymer cement mortar is used as a protective material with good adhesion to concrete, but it has a drawback that it has a lower electrical conductivity than ordinary cement mortar, and there is a problem in using it in an anticorrosion method.

JP-A-4-74747 discloses a conductive mortar composition that exhibits high elasticity, electromagnetic wave shielding, rapid hardening, and strength development, specifically, cement, gypsum, alumina cement, carbon fiber, and A conductive mortar composition based on a polymer admixture is disclosed.
Japanese Patent Application Laid-Open No. 7-206502 discloses a conductive polymer cement mortar that can be used for anticorrosion, and specifically, a conductive polymer cement mortar containing carbon fibers and conductive fine particles. ing.
However, since many of the protective mortar materials with improved conductivity described above improve the conductivity of the mortar by mixing a carbon material, the carbon is oxidized by current conduction to become CO ₂ , and in the long term There is a problem that the conductivity is significantly reduced.

JP-A-4-103785 discloses an anticorrosion backfill containing a non-flowable and non-water-retaining material and nitrite as an anticorrosion backfill.
Since such lithium nitrite has an action of promoting hardening on cement, there is a problem that when lithium nitrite is mixed, the working time is remarkably shortened and the work becomes impossible. Also, the adhesion strength is low and not practical.
Japanese Patent Laid-Open No. 4-74747 JP-A-7-206503 JP-A-4-103785

An object of the present invention is to provide a conductive cement mortar having excellent conductivity, improved adhesion to concrete, and excellent workability.
Another object of the present invention is to provide a conductive cement mortar capable of preventing reduction and inactivation of the anode resistivity in the cathodic protection method.
Still another object of the present invention is to provide an anode protection material for anticorrosion using the conductive cement mortar of the present invention, which can prevent the decrease in resistivity and inactivation of the anode.

  In order to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be achieved by setting the particle size of the polymer used in the polymer cement mortar containing lithium nitrite to a certain level or more, and have reached the present invention. .

The conductive polymer cement mortar of the present invention contains cement, lithium nitrite, a cement admixture retarder, a synthetic surfactant-based foaming agent, and a cement admixture polymer, and the cement admixture polymer has a particle size of 0.3 μm. It is the above.
Preferably, the conductive polymer cement mortar of the present invention is the conductive polymer cement mortar, wherein 1 to 10 parts by weight of lithium nitrite and 0.1 to 0.1 parts of the cement admixture retarder are added to 100 parts by weight of cement. 1.0 part by weight, a synthetic surfactant-based foaming agent is blended in a proportion of 0.1 to 1.0 part by weight, and the cement admixing polymer is 0.5 to 0.5 parts in terms of solid content with respect to 100 parts by weight of cement. 20 weight part is mix | blended, It is characterized by the above-mentioned.
Furthermore, the protective material for anticorrosion of the present invention uses the conductive polymer cement mortar of the present invention.

The conductive polymer cement mortar of the present invention has a lower resistivity than a normal cement mortar and can improve conductivity without mixing a conductive material such as a carbon material. It becomes possible to hold.
Furthermore, the conductive polymer cement mortar of the present invention can ensure sufficient working time without lowering the strength even when lithium nitrite blended for improving conductivity is mixed in the polymer cement mortar, Because of its excellent adhesion to the steel, it is possible to exert an excellent effect on the repair of the reinforced concrete structure in the cathodic protection method.

  In addition, the protective material for cathodic protection of the present invention can use the conductive polymer cement mortar of the present invention as a protective material for the anode for cathodic protection, thus reducing the anode generation current required for cathodic protection. In other words, it is possible to maintain an effective potential difference between the anode and the reinforcing bar over a long period of time.

The present invention will be described with reference to preferred examples, but is not limited thereto.
The conductive polymer cement mortar of the present invention contains cement, lithium nitrite, a cement admixture retarder, a synthetic surfactant-based foaming agent, and a cement admixture polymer, and the cement admixture polymer has a particle size of 0.3 μm. It is necessary to be above.
By having such a configuration, it is possible to obtain a cement mortar with improved conductivity and adhesion between concrete and excellent workability.

  The cement that can be used for the conductive polymer cement of the present invention means a cement mainly composed of a hydraulic calcium silicate compound, and the kind thereof is not particularly limited. For example, various portland cements such as normal and early strength, , Various cements available in the market such as blast furnace cement, mixed cement of silica cement and fly ash cement, white Portland cement and alumina cement can be exemplified, and these can be used alone or in combination. it can. In particular, it is preferable to use early strong cement from the viewpoint of conductivity.

Moreover, although lithium nitrite used for the conductive polymer cement mortar of the invention may be used as it is, it can also be used as an aqueous solution.
The mixing amount is 1 to 10 parts by weight, preferably 3 to 6 parts by weight of lithium nitrite with respect to 100 parts by weight of cement, and the workability and strength development of the conductive polymer cement mortar of the present invention is achieved. This is desirable because it can improve the performance.

Furthermore, by making lithium nitrite present in the polymer cement mortar, it becomes possible to suppress macrocell corrosion generated in the reinforcing bars of the concrete structure.
Further, when lithium nitrite is used as an aqueous solution, the concentration thereof is not particularly limited, but it is usually sufficient to use an aqueous solution having a concentration of 10 to 50% by weight.

  In addition, as a cement admixture retarder used in the conductive polymer cement mortar of the present invention, oxycarboxylic acid, dicarboxylic acid, ketocarboxylic acid, fatty acid, sugar alcohol, saccharide, lignin sulfonic acid, Various retarders available on the market can be used. As the amount of the mixture, 0.1 to 1.0 parts by weight of the cement mixing retarder, preferably 0.5 to 1.0 parts by weight, with respect to 100 parts by weight of cement, Even when lithium nitrite is mixed, it is preferable because a sufficient working time can be secured. On the other hand, when the amount exceeds 1.0 part by weight, the working time is remarkably reduced due to the promoting action on the hydration reaction of the cement.

  Further, as the synthetic surfactant-based foaming agent that can be used for the conductive polymer cement of the present invention, various surfactants such as anionic, cationic, amphoteric surfactants, nonionic surfactants, and the like are used. be able to. For example, as an anionic surfactant, carboxylate, sulfate ester, sulfonate, phosphate ester salt, and as a cationic surfactant, primary amine salt, secondary amine salt, tertiary Examples of amine salts, quaternary ammonium salts, and amphoteric surfactants include amino acid type, betaine type, and nonionic surfactants such as polyethylene glycol type and polyhydric alcohol type.

  By mixing these synthetic surfactant-based foaming agents together with lithium nitrite, lithium nitrite is incorporated into the bubbles in the polymer cement, and the electrical conductivity can be further improved. The mixing amount is desirably 0.1 to 1.0 part by weight with respect to 100 parts by weight of cement. When a large amount is mixed, the unit volume mass is remarkably lowered and the compressive strength is also lowered, which is not preferable.

As the polymer for admixture with cement, which can be used for the conductive polymer cement of the present invention, a liquid polymer emulsion, rubber latex, powdered re-emulsified powder resin, or the like can be used. In particular, when using a re-emulsified powder resin, there is no need for on-site weighing, and quality control becomes easy.
As these admixture polymers, polyacrylic acid ester exemplified in JIS A 6203, styrene butadiene, ethylene vinyl acetate, vinyl acetate / versaic acid vinyl ester, vinyl acetate / vinyl versatate / acrylic acid ester and the like are the main components. Examples thereof include polymer dispersions and re-emulsifying powder resins.

These admixing polymers have a particle size of 0.3 μm or more, preferably 0.5 μm or more, in order to improve conductivity. When a polymer having a particle size of less than 0.3 μm is used, a dense polymer film is formed, so that the conductivity is significantly lowered.
Preferably, the admixing polymer tends to aggregate the polymer particles when the particle size is increased, but is not particularly limited as long as it does not adversely affect the production of cement mortar. In particular, when the polymer is used in an emulsion, its particle size is 0.3 to 3 μm, and when it is used in a powder form, its particle size is about 0.3 to about 300 μm for convenient handling. Therefore, it is preferably used.
Such an admixing polymer is preferably 0.5 to 20 parts by weight, preferably 2 to 10 parts by weight, in terms of solid content, with respect to 100 parts by weight of cement. The workability is further improved.

  In addition, the cement used in the present invention is a material having pozzolanic activity, such as blast furnace slag powder, fly ash, silica fume, limestone powder, quartz powder, in order to improve long-term strength, ease shrinkage, and prevent occurrence of cracks, Known admixtures that can be mixed with cement such as dihydrate gypsum, hemihydrate gypsum, type I and type II, and type III anhydrous gypsum can be blended alone or in combination.

  Further, among the other components to be blended in the polymer cement mortar of the present invention, as fine aggregates, fine sand with relatively fine particle diameter such as river sand, mountain sand, land sand, crushed sand, sea sand, silica sand Nos. 6-7, etc. Aggregate, or fine powders such as quartzite powder and limestone powder can be used. The amount of fine aggregate is usually 50 to 400 parts by weight, preferably 100 to 200 parts by weight, with respect to 100 parts by weight of cement, from the viewpoint of workability.

  The conductive polymer cement mortar of the present invention is made of the above-mentioned cement, lithium nitrite, cement admixture retarder, synthetic surfactant-based foaming agent, cement admixture polymer, aggregate and water, if necessary, However, the mixing method is not particularly limited, and a part of the above materials may be mixed in advance, and all the materials may be used on site. You may mix at once.

The amount of water used in the conductive polymer cement mortar of the present invention is not uniquely determined because it can be changed depending on the type and blending of the materials used. -60% is preferable, and 30-50% is particularly preferable. By blending water in such a range, sufficient workability and sufficient strength development will be obtained.
In addition, the water at the time of calculating the water / cement ratio in the present invention includes water contained in polymer dispersions such as polymer latex and resin emulsion in addition to kneaded water.

  The conductive polymer cement mortar of the present invention thus obtained is obtained by mixing lithium nitrite, a cement admixture retarder, and a synthetic surfactant-based foaming agent with the polymer cement mortar, so that the conductivity and concrete are mixed. Adhesion can be enhanced and workability can be improved, and therefore the cement mortar can be used for the secondary anode material and the anode coating material of the cathodic protection method.

Examples 1-3; Comparative Examples 1-10
Using the following raw materials, each material was mixed at a blending ratio shown in Table 1 to prepare a polymer cement mortar. Table 1 also shows the unit volume mass.
・ Lithium nitrite: Reflet α40 (40% lithium nitrite aqueous solution, manufactured by Sumitomo Osaka Cement Co., Ltd.)
-Retarder: Jet setter (Sumitomo Osaka Cement Co., Ltd.)
・ Synthetic surfactant type foaming agent: Sumishield A (manufactured by Sumitomo Osaka Cement Co., Ltd.)
Re-emulsifying powder resin: Mobilis powder DM2072P (manufactured by Clariant Polymer Co., Ltd.)
・ Polymer dispersion; Lipotex PAC32C (manufactured by Lion Corporation)
・ Cement: Ordinary Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.)
・ Silica sand; Silica sand No. 6 ・ Water: Tap water

Test Example 1: Measurement of resistivity (production of test specimen)
The polymer cement mortar obtained in Examples 1 to 3 and Comparative Examples 1 to 10 was poured into a 40 × 40 × 160 mm mold, and at the same time, using stainless steel (Sus316, t = 0.3 mm) as an electrode plate. The electrode plate was embedded in a mortar in the mold with an interelectrode distance of 140 mm and an electrode area of 30 × 40 mm. After 24 hours, the test specimen was removed from the mold and a 40 × 40 × 160 mm test mortar was molded.
Next, after demolding, curing was carried out in an environment of a temperature of 20 ° C. and a humidity of 85% RH.

(Conductivity test)
Using an impedance measuring device (product name; LCR HiTester, manufactured by HIOKI Corporation), the conductance of the specimen after 28 days of age is measured, and the resistivity is calculated according to the following equation. The results are shown in Table 2. .
Resistivity (Ω · cm) = (R · A) / L, R = 1 / G
In the above formula, A represents the electrode area, L represents the distance between the electrodes, R represents resistance (Ω), and G represents conductance (S).

Test Example 2; Measurement of pot life For each polymer cement mortar obtained in Examples 1 to 3 and Comparative Examples 1 to 10, according to 11 (flow test) of JIS R 5201 (physical test method for cement), The flow values immediately after kneading and after 30 minutes were measured, and the results are shown in Table 3.

但し、表中、×はモルタルが固まってしまい、測定不能であることを示す。

However, in the table, x indicates that the mortar is hardened and cannot be measured.

Test Example 3; Measurement of Compressive Strength and Adhesive Strength For each test body 28 days after material age formed from each polymer cement mortar of Examples 1 to 3 and Comparative Examples 1 to 10 obtained in Test Example 1 above, The compressive strength was measured according to JIS A 6203 (compressive strength). In addition, each polymer cement mortar with a thickness of 1 cm is applied to a 300 x 300 x 600 mm JIS A 5304 pavement concrete plate, cured at 20 ° C and 60% humidity for 28 days, and cut into a concrete board to a size of 40 x 40 mm. After attaching the steel attachment with an epoxy adhesive, the bond strength was measured using a Kenken-type adhesion tester. The results are shown in Table 4.

Since the conductive polymer cement mortar of the present invention has the above-described effects, it can be usefully used in an anticorrosion method for concrete structures, and can be used particularly as an anode protection material for cathodic protection and as a secondary anode material. .

Claims (3)

  Containing a cement, lithium nitrite, a cement admixture retarder, a synthetic surfactant-based foaming agent and a cement admixture polymer, wherein the particle diameter of the cement admixture polymer is 0.3 μm or more, Polymer cement mortar.   2. The conductive polymer cement mortar according to claim 1, wherein 1 to 10 parts by weight of lithium nitrite, 0.1 to 1.0 parts by weight of a retarder for cement admixture, and a synthetic surfactant with respect to 100 parts by weight of cement. The system foaming agent is blended at a ratio of 0.1 to 1.0 parts by weight, and the polymer for cement admixture is blended at 0.5 to 20 parts by weight in terms of solid content with respect to 100 parts by weight of cement. Conductive polymer cement mortar. A protective material for cathodic protection using the conductive polymer cement mortar according to claim 1.