JP4634212B2 - Alumina cement composition and repair method using the same - Google Patents

Description

  The present invention relates to an alumina cement composition used for repairing a concrete structure, particularly repairing a concrete structure in a sewage treatment facility that has been deteriorated by sulfuric acid, and a repair method using the same.

In concrete structures in sewage treatment facilities, sulfuric acid is generated due to the effect of sulfate-reducing bacteria generated in the sewage, and the concrete is eroded. In addition, corrosion of the internal reinforcing bars creates rust expansion pressure, which causes cracks and floats in the concrete. However, the concrete pieces are peeled off. As a repair method in such a sewage treatment facility, a method of removing a deteriorated portion with a water jet and repairing a cross section and then performing resin lining is often performed. The cross-sectional restoration material used for this is a material containing a polymer blended with blast furnace granulated slag (Patent Document 1), a material made of alumina cement (Patent Documents 2 and 3), and a large amount of fine powder such as blast furnace granulated slag and silica fume. Mixed cement mortar is used (Patent Document 4). Further, a material using alumina cement and blast furnace slag fine powder, and a material containing 5 μm or less of alumina cement particles of 25 μ% or less and containing a lithium salt has been proposed (Patent Document 5).
Japanese Patent Laid-Open No. 03-290348 JP 2003-89565 A JP 2004-292245 A JP 2000-128618 A JP 2002-293603 A

However, the deterioration of concrete structures due to sulfuric acid proceeds due to the reaction of calcium hydroxide and sulfuric acid generated by cement hydration, so there is a slight pinhole in the resin lining in repair materials using ordinary Portland cement. Then, there was a problem that long-term durability could not be expected. In addition, sewage treatment facilities have open pits and waterways with low humidity and good wind passage, and in the cold season of winter, the setting time of cement is delayed, so initial shrinkage cracks are likely to occur. was there. Furthermore, a material in which a large amount of fine powder is mixed has a problem that self-shrinkage is larger than that of polymer cement, initial cracking is likely to occur not only in winter, but mortar has a strong stickiness and workability is poor.
In order to solve the above problems, the present inventors provide a specific alumina cement composition and a repair method using the same.

That is, the present invention includes (1) an alumina cement composition containing an alumina cement, a pozzolanic material, and hectorite having a Li ₂ O content of 0.7 to 2.5% by mass , and an aggregate ; (1) Alumina cement composition containing molecular fibers, (3) Alumina cement composition (2) having a fiber length of 2 to 15 mm and an aspect ratio of 300 to 1000, (4) Fluidization The alumina cement composition according to any one of (1) to (3) containing an agent, (5) The alumina cement composition according to any one of (1) to (4) containing a polymer for admixture with cement, (6) Water absorption containing inhibitor (1) either alumina cement composition to (5), (7) (1) repairing method of the concrete structure using any of the alumina cement composition to (6), der .

  Repair of concrete structures excellent in workability, low-temperature curing properties, initial crack resistance, strength development, sulfuric acid resistance, etc., and long-term durability by the alumina cement composition of the present invention and the repair method using the same Can be performed.

  Hereinafter, the present invention will be described in detail.

The alumina cement used in the present invention is obtained from a clinker pulverized product containing monocalcium aluminate as a main mineral. For example, alumina cement 1 or alumina cement 2 can be used. The fineness of the alumina cement is preferably 2000 to 8000 cm ² / g in terms of hydration activity. Moreover, the particle size of the alumina cement is adjusted, and particles having a particle diameter of 5 μm or less and less than 30% by mass are preferable because shrinkage when cured is reduced.

The pozzolanic substance used in the present invention is a substance that exhibits pozzolanic activity by alkali stimulation, and is used in combination with alumina cement for the purpose of suppressing strength reduction due to phase transition of hydrate, and dripping of mortar during construction. It is used for the purpose of improving resistance. Examples include blast furnace granulated slag, blast furnace slow-cooled slag, converter slag, silica fume, fly ash, and the like.
The fineness of the pozzolanic material is preferably a brane specific surface area of 3000 cm ² / g or more in terms of hydration activity.
Usually, the amount of the pozzolanic material is preferably 80 to 200 parts by mass and more preferably 100 to 150 parts by mass with respect to 100 parts by mass of the alumina cement. Silica fume is preferably 1 to 10 parts by mass with respect to 100 parts by mass of alumina cement.

Hectorite having a Li ₂ O (lithium oxide) content of 0.7 to 2.5% by mass used in the present invention is a kind of clay mineral belonging to smectites and has a layered structure. Characteristically, various metal ions with water molecules are contained between the layers, and the metal ions between the layers have exchangeability. Hectorite is characterized by containing lithium. The Li ₂ O content of hectorite is preferably 0.7 to 2.5% by mass. If it is less than 0.7% by mass, the effect of promoting curing at low temperatures is small, and if it exceeds 2.5% by mass, the fluidity is affected. There is a case. Although the conventional use of hectorite has thixotropy, it is used for the purpose of improving the rheological properties of cementitious materials. However, when applied to alumina cementitious materials, the curing properties at low temperatures are improved.
0.1-10 mass parts is preferable with respect to 100 mass parts of alumina cement, and, as for the usage-amount of hectorite, 0.3-5 mass parts is more preferable. If it is less than 0.1 parts by mass, the effect of promoting curing at low temperatures is small, and if it exceeds 10 parts by mass, curing may become too fast and affect the fluidity of the mortar.

The polymer fiber used in the present invention is used for the purpose of suppressing large cracks due to shrinkage when the alumina cement is cured. Examples of the polymer fiber include vinylon fiber, polypropylene fiber, acrylic fiber, and nylon fiber. Although not particularly limited, it is preferable to use vinylon fibers or acrylic fibers, which have relatively good fiber adhesion in mortar. In particular, it is preferable for suppressing large cracks caused by shrinkage when polymer fibers having a fiber length of 2 to 15 mm and an aspect ratio of 300 to 1000 are cured.
The amount of the polymer fiber used is preferably 0.02 to 0.6 parts by mass, more preferably 0.05 to 0.4 parts by mass with respect to 100 parts by mass in total of the alumina cement, pozzolanic substance, hectorite and aggregate. preferable. If it is less than 0.02 parts by mass, the effect of suppressing cracking is small, and if it exceeds 0.6 parts by mass, it may affect the fluidity of the mortar.

The fluidizing agent used in the present invention is used for the purpose of imparting an appropriate fluidity to the mortar. For example, a polycarboxylic acid compound, a melamine compound, a lignin sulfonic acid compound, a naphthalene sulfonic acid compound, etc. Is mentioned. Among these, it is preferable to use a polycarboxylic acid compound or a melamine compound from the viewpoint of giving appropriate fluidity and hardly affecting the strength development.
The amount of the fluidizing agent used is preferably 0.01 to 1 part by mass and more preferably 0.05 to 0.5 part by mass with respect to 100 parts by mass of the alumina cement. If it is less than 0.01 part by mass, it is difficult to give an appropriate fluidity, and if it exceeds 1 part by mass, strength development may be affected.

The cement-mixing polymer used in the present invention is a cement-mixing polymer (polymer dispersion) defined in JIS A 6203, which improves the durability of neutralization, salt damage, frost damage, etc., and adheres to mortar. Used to improve strength properties such as strength, bending strength, and tensile strength. For example, rubber latex such as acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, and natural rubber, ethylene-vinyl acetate copolymer, polyacrylate ester, vinyl acetate vinyl versatate copolymer, and styrene-acrylic Examples include acid ester copolymers, acrylic ester copolymers represented by acrylonitrile / acrylic acid esters, epoxy resins, liquid polymers represented by unsaturated polyester resins, and the like. Mixtures can be used.
The amount of the cement-mixing polymer used is preferably 0.5 to 20 parts by mass, more preferably 2 to 15 parts by mass, based on 100 parts by mass of the alumina cement. If it is less than 0.5 part by mass, the effect of improving the durability is small, and if it exceeds 20 parts by mass, the strength development may be affected.

The water absorption inhibitor used in the present invention is used for the purpose of lowering the water absorption of the cured mortar, and has an effect of suppressing permeation of sulfate ions dissolved in moisture. For example, there are higher fatty acid compounds such as calcium stearate and silanes such as paraffin and alkylalkoxysilane. Among these, the use of a silane-based water absorption inhibitor is preferable because it hardly affects the fluidity of the mortar and has a large water-repellent effect. Both liquid and powder can be used, but it is preferable to use a powdery water absorption inhibitor that can be premixed in advance.
0.2-8 mass parts is preferable with respect to 100 mass parts of alumina cement, and, as for the usage-amount of a water absorption inhibitor, 0.5-5 mass parts is more preferable. If the amount is less than 0.2 parts by mass, the effect of suppressing the permeation of sulfate ions is small. If the amount exceeds 8 parts by mass, the strength development may be affected.

The alumina cement composition of the present invention can be mixed with water and used as a paste containing no aggregate, or as a mortar or concrete containing aggregate, but the type of aggregate to be used is not particularly limited. However, it is preferable to use an aggregate having acid resistance. Examples thereof include silica aggregate, alumina aggregate, mullite aggregate, chamotte aggregate, silicon carbide aggregate, alumina cement clinker aggregate, and the like.
The amount of the aggregate used is preferably 0 to 250 parts by mass with respect to 100 parts by mass in total of the alumina cement, the pozzolanic substance, and hectorite, and if it exceeds 250 parts by mass, the fluidity and adhesion strength tend to decrease. Moreover, it is preferable to use the paste which does not contain an aggregate when thinly coating 2 mm or less, and to use the mortar and concrete containing an aggregate when ensuring the thickness exceeding 2 mm.

In the present invention, when more rapid strength development is required at a low temperature, lithium salts such as carbonic acid, sulfuric acid, silicic acid, nitric acid, hydroxide, phosphoric acid, boric acid and organic acid can be used in combination.
The alumina cement composition of the present invention is used in combination with various additives such as an AE agent, a thickener, a foaming agent, a setting retarder, an antifreezing agent, a shrinkage reducing agent, and an antibacterial agent as long as the quality is not adversely affected. be able to.

  The repair method of the alumina cement composition of the present invention may be a mortar kneaded with a mixer, coated with a trowel, filled into a mold, or sprayed by blowing off the mortar using compressed air. You may construct.

  Examples will be described in detail below.

A compound was prepared by adding 120 parts by mass of pozzolanic material A to 100 parts by mass of alumina cement and 0.3 parts by mass of hectorite having the Li ₂ O content shown in Table 1. 170 parts by mass of the material was added to form dry mortar, and the flow, initial time, initial crack resistance, compressive strength, and sulfuric acid resistance of the mortar obtained by adding 16 parts by mass of water to 100 parts by mass of the dry mortar were measured. The results are shown in Table 1.

(Materials used)
Alumina cement: Alumina cement No. 1, commercial product pozzolanic substance A: ground granulated blast furnace slag, Blaine specific surface area 7000 cm ² / g, commercial product hectorite: density 2.6 g / cm ³ , maximum particle size 100 μm, commercial product montmorillonite : Density 2.7 g / cm ³ , maximum particle size 150 μm, commercial product aggregate: dry silica sand, maximum particle size 1.2 mm

(Measuring method)
Flow test, compressive strength test: Measured according to JIS R 5201.
First time: Measured according to JIS A 1147 (test temperature 5 ° C.).
Initial crack resistance: Kneaded mortar is applied to a concrete flat plate with a length of 30 cm x width 30 cm x thickness 6 cm to a thickness of 10 mm, temperature 5 ° C, humidity 40%, average wind speed: 2 m / s The total length of the crack after one day was measured.
Sulfuric acid resistance test: Kneaded mortar is molded into φ7.5 × 15cm, cured in water at 20 ° C for 28 days, and then immersed in 5% sulfuric acid aqueous solution at 20 ° C for 28 days. The depth was measured. The penetration depth was determined by the phenolphthalein method.

From Table 1, the alumina cement composition of the present invention is excellent in workability, low-temperature curing property, initial crack resistance, strength development, and sulfuric acid resistance, and in the case of hectorite having a Li ₂ O content outside the scope of the present invention. It can be seen that the fluidity decreases, and the initial cracking resistance decreases with montmorillonite.

  In Experiment No. 1-3 of Example 1, it carried out like Example 1 except having changed the usage-amount of hectorite as shown in Table 2 with respect to 100 mass parts of alumina cements. The results are shown in Table 2.

  From Table 2, it can be seen that the alumina cement composition of the present invention is excellent in workability, low-temperature curing property, initial crack resistance, strength development, and sulfuric acid resistance, and the initial crack resistance is improved by hectorite.

  In Experiment No. 1-3 of Example 1, the same procedure as in Example 1 was performed except that the kind and amount of the pozzolanic substance were changed as shown in Table 3. The results are shown in Table 3.

(Materials used)
Pozzolanic material B: fly ash, Blaine specific surface area 4500 cm ² / g, commercial product pozzolanic material C: silica fume, average particle size 0.1-0.2 μm, commercial product

  From Table 3, the alumina cement composition of the present invention is excellent in workability, low-temperature curability, initial crack resistance, strength development, and sulfuric acid resistance, and the pozzolanic substance improves strength development and sulfuric acid resistance. I understand.

  In Experiment No. 1-3 of Example 1, it carried out like Example 1 except having added polymer fiber as shown in Table 4 with respect to 100 mass parts of dry mortar. The results are shown in Table 4.

(Materials used)
Polymer fiber A: polypropylene fiber, fiber length 12 mm, fiber diameter 18 μm, aspect ratio 667, commercially available polymer fiber B: vinylon fiber, fiber length 6 mm, fiber diameter 14 μm, aspect ratio 429, commercially available product

  From Table 4, the alumina cement composition of the present invention is excellent in workability, low-temperature curing properties, initial crack resistance, strength development, and sulfuric acid resistance, and the initial crack resistance is improved by using polymer fibers. I understand that.

  In Experiment No. 1-3 of Example 1, a blending agent was prepared by adding a fluidizing agent to 100 parts by mass of alumina cement as shown in Table 5, and 14.5% of water was added to 100 parts by mass of dry mortar. The same procedure as in Example 1 was performed except that 0.1 part by mass of polymer fiber B used in Example 4 was added. The results are shown in Table 5.

(Materials used)
Fluidizer A: Methylolmelamine compound, commercially available fluidizer B: Polycarboxylic acid fluidizer, powder, commercially available product

  From Table 5, the alumina cement composition of the present invention is excellent in workability, low-temperature curing properties, initial crack resistance, strength development, and sulfuric acid resistance, and the fluidity of the mortar is improved by using a fluidizing agent. I understand that.

  In Experiment No. 5-5 of Example 5, a blending polymer was prepared by adding a cement-mixing polymer (in terms of solid content) to 100 parts by mass of alumina cement as shown in Table 6, and into 100 parts by mass of this dry mortar. On the other hand, it carried out like Example 1 except having added 14.5 mass parts of water and 0.1 mass part of polymer fiber B used in Example 4. The results are shown in Table 6.

(Materials used)
Cement admixture polymer: Acrylic-styrene re-emulsifying powder resin, commercial product

  From Table 6, the alumina cement composition of the present invention is excellent in workability, low-temperature curing properties, initial crack resistance, strength development, and sulfuric acid resistance. Can be seen to improve.

  In Experiment No. 5-5 of Example 5, a blend was prepared by changing the amounts of the water absorption inhibitor and the cement-mixing polymer used in Example 6 to 100 parts by mass of alumina cement as shown in Table 7. Except that, the same procedure as in Example 6 was performed. The results are shown in Table 7.

(Materials used)
Water absorption inhibitor: Powdered alkylalkoxysilane water absorption inhibitor, commercial product

  From Table 7, the alumina cement composition of the present invention is excellent in workability, low-temperature curing properties, initial crack resistance, strength development, and sulfuric acid resistance, and is resistant to sulfuric acid by using an absorption inhibitor and a cement admixing polymer. It can be seen that the performance is improved.

  In Experiment No. 6-4 of Example 6, the same procedure as in Example 6 was performed except that the amount of aggregate used was changed as shown in Table 8 and the adhesion strength was measured. The results are shown in Table 8.

(Adhesion strength)
Measurement was performed in accordance with JIS A 1171.

  From Table 8, it can be seen that the alumina cement composition of the present invention is excellent in workability, low-temperature curing properties, initial crack resistance, strength development, and sulfuric acid resistance, and the adhesion strength varies depending on the amount of aggregate used.

Experiment 1 No. 1-3 of Example 1, Experiment No. 5-5 of Example 5 and Mortar of the alumina cement composition of Experiment No. 6-4 of Example 6 were controlled at a temperature of 5 ° C. and a humidity of 40%. A concrete plate placed on the ceiling surface in the room was coated with a iron so that the thickness was 20 mm (coating area: about 0.5 m ² ). As a result, the workability of the trowel application was good, and even if it was applied so that the thickness became 20 mm at a time, there was no peeling. Further, when a hammering test was conducted one day later, no floating was observed. Furthermore, when the adhesion strength test was performed on the 7th day of age in the same manner as in Example 8, it was 2.0 N / mm ² in the mortar of Experiment No. 1-3 in Example 1, and in Experiment No. 5- in Example 5. The mortar of 5 showed 2.3 N / mm ² , and the mortar of Experiment No. 6-4 of Example 6 showed high adhesion of 2.4 N / mm ² .

  Repair of concrete structures excellent in workability, low-temperature curing properties, initial crack resistance, strength development, sulfuric acid resistance, etc., and long-term durability by the alumina cement composition of the present invention and the repair method using the same Therefore, it can be widely applied in civil engineering fields such as sewage treatment facilities.

Claims (7)

An alumina cement composition containing an alumina cement, a pozzolanic material, hectorite having a Li ₂ O content of 0.7 to 2.5% by mass , and an aggregate . The alumina cement composition according to claim 1, comprising a polymer fiber. The alumina cement composition according to claim 2, wherein the polymer fiber has a fiber length of 2 to 15 mm and an aspect ratio of 300 to 1,000. The alumina cement composition according to any one of claims 1 to 3, comprising a fluidizing agent. The alumina cement composition according to any one of claims 1 to 4, comprising a cement admixing polymer. The alumina cement composition according to any one of claims 1 to 5, comprising a water absorption inhibitor. The repair method of the concrete structure using the alumina cement composition of any one of Claims 1-6 .