JP6966967B2 - Construction method of salt-shielding mortar - Google Patents

Description

The present invention relates to a method for constructing a salt-shielding mortar.

Alumina cement is known to be superior in chemical resistance to, for example, Portland cement (for example, Patent Document 1 and the like).

Japanese Unexamined Patent Publication No. 2008-174429

However, alumina cement may have a decrease in compressive strength due to aging and high temperature curing. Further, alumina cement has a problem that cracks are likely to occur due to shrinkage.

A main object of the present invention is to provide a method for constructing a salt-shielding mortar that can realize excellent salt-shielding property, excellent long-term durability and excellent crack resistance.

As a result of diligent research, the present inventors have obtained the salt-shielding property and long-term durability of the salt-shielding mortar cured product by using the alumina cement composition for salt-shielding mortar that satisfies the following conditions 1) to 4). We came up with the idea of improving crack resistance, and as a result, we came up with the present invention.

1) It 2) alumina cement comprising alumina cement and gypsum hemihydrate is, CA55 mass% to 75 _{mass%, C} 12 _{A 7} 5 wt% to 8 _wt%, C 4 AF10 wt% to 28 wt% and _C 2 AS2 including wt% to 6 wt% 3) Blaine specific surface area of the alumina ^{cement, 2000cm 2 / g~4000cm 2 / g} 4 it is) to the alumina cement 100 parts by weight, the hemihydrate gypsum 15 parts by weight to 35 In other words, in the method for constructing a salt-shielding mortar according to the present invention, a salt-shielding mortar prepared by kneading an alumina cement composition for salt-shielding mortar and water is applied to a concrete structure. .. A forming step of forming a salt-shielding mortar cured product is performed by curing the salt-shielding mortar. The construction method for shielding salt mortar according to the present invention, as the alumina cement compositions for barrier salt mortar comprises alumina cement and hemihydrate gypsum, alumina cement, CA55 mass% to 75 mass%, C ₁₂ A ₇ 5 wt% to 8 _wt%, comprising a C 4 AF10 wt% to 28 wt% and _C 2 AS2 wt% to 6 wt%, Blaine specific surface area of the alumina cement ^is 2000cm ² / g~4000cm 2 / g, alumina An alumina cement composition for a salt-shielding mortar containing 15 parts by mass to 35 parts by mass of hemihydrate gypsum with respect to 100 parts by mass of cement is used.

In the method for constructing a salt-shielding mortar according to the present invention, it is preferable that the alumina cement composition for salt-shielding mortar further contains at least one of calcium carbonate and silica fume.

In the method for constructing a salt-shielding mortar according to the present invention, the alumina cement composition for a salt-shielding mortar contains 15 parts by mass to 35 parts by mass of calcium carbonate and 5 parts by mass to 5 parts by mass of silica fume with respect to 100 parts by mass of alumina cement. It is preferably contained in an amount of 12 parts by mass.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for constructing a salt-shielding mortar that can realize excellent salt-shielding property, excellent long-term durability and excellent crack resistance.

It is a schematic cross-sectional view of the apparatus for measuring the length change amount at the time of curing of a salt-shielding mortar. It is a schematic cross-sectional view in the line (b)-(b) of FIG.

(Construction method of salt-shielding mortar)
In the method of constructing the salt-shielding mortar of the present embodiment, the construction process is first performed. In the construction process, a salt-shielding mortar prepared by kneading an alumina cement composition for salt-shielding mortar and water is applied to a concrete structure. Specifically, first, an alumina cement composition for a salt-shielding mortar is prepared. Then, the alumina cement composition for salt-shielding mortar and water are kneaded to obtain a salt-shielding mortar.

The kneading of the alumina cement composition for salt-shielding mortar with water can be performed by using a mixer such as a hand mixer or a mortar mixer.

The amount of water added to the alumina cement composition for salt-shielding mortar is preferably 2 parts by mass to 18 parts by mass, and more preferably 4 with respect to 100 parts by mass of the alumina cement composition for salt-shielding mortar. It is 16 parts by mass to 16 parts by mass, more preferably 10 parts by mass to 14 parts by mass, and further preferably 11 parts by mass to 13 parts by mass. When the synthetic resin emulsion described later is contained, it is necessary to subtract the amount of water contained in the synthetic resin emulsion from the amount of water to be added.

(Formation process)
Next, a forming step is performed. In the forming step, a salt-shielding mortar cured product is formed by curing the salt-shielding mortar. Specifically, for example, the concrete structure is repaired by supplying and hardening the salt-shielding mortar to the missing portion formed by removing the deteriorated portion of the concrete structure.

More specifically, first, the position and region of the deteriorated part of the concrete structure are specified by observing the appearance and investigating the tapping method. Next, the removal area is determined including some healthy parts around the deterioration area so that the deterioration area of the concrete structure is completely removed. A notch of, for example, about 10 mm is made in the depth direction from the concrete surface using an electric cutter or the like along this removal area. Finally, depending on the area and depth of the removal area, the deteriorated concrete is scraped off by using a hammer, a hand breaker, a shot blast, a water jet or the like as appropriate.

The concrete structure from which the portion including the deteriorated region is removed has a recess formed by scraping the concrete, and the reinforcing bar may be exposed depending on the depth of the recess. When the exposed reinforcing bar is corroded, it is preferable to remove the rust by a method such as a wire brush or shot blasting and apply a rust preventive material. Examples of the rust preventive material preferably used include a cement composition, a synthetic resin (polymer), a rust preventive component, a polymer cement-based rust preventive material containing water and the like. The rust preventive material can be applied using, for example, a brush, a ricing gun, or the like. At this time, it is preferable to apply the reinforcing bar so that there are no unapplied portions on the surface of the reinforcing bar.

Further, the recess formed by scraping the surface of the concrete structure may be protected by applying a water absorption adjusting agent (primer) to form a primer layer. As the water absorption adjusting agent, a synthetic resin emulsion diluted with water can be preferably used. The water absorption adjusting agent can be applied using, for example, a brush, a ricing gun, or the like.

It is preferable that the salt-shielding mortar is supplied (constructed) in a plurality of times.

When the area of the concave portion region of the concrete structure filled with the salt-shielding mortar is ^{less than 10 m 2} , it is preferable to supply the salt-shielding mortar by, for example, the plastering method. In the plastering method, an appropriate amount of salt-shielding mortar is placed on a trowel plate and applied to the recesses in several steps using a trowel or the like. For example, in the first construction, it is preferable to apply the coating to a thickness of, for example, about 5 mm, and in the second and subsequent constructions, it is preferable to repeat the coating to a thickness of 10 mm or less. The coating thickness for one day is preferably about 30 mm.

When the plastering method is used, in the final construction, the surface is finished flat with a trowel so that the salt-shielding mortar and the concrete structure are integrated.

If recessed area of the concrete structure to fill the salt mortar shielding is 10m ² ~100m ^2, for example, it is preferable to supply the salt mortar barrier in spraying method or the like. The spraying method is a method of filling the recesses of the concrete structure with the salt-shielding mortar by spraying the salt-shielding mortar onto the concrete structure.

In the spraying method, it is preferable to spray the salt-shielding mortar into the recesses of the concrete structure in several times. In the first construction, it is preferable to spray the salt-shielding mortar so as to have a thickness of, for example, about 5 mm, and in the second and subsequent constructions, it is preferable to repeatedly spray the salt-shielding mortar so as to have a thickness of 30 mm or less. In the final construction, it is preferable to spray a salt-shielding mortar so as to have a thickness of about 15 mm. After that, the surface of the salt-shielding mortar is finished flat with a trowel so that the concrete structure and the salt-shielding mortar filled in the concave region of the concrete structure are integrated. As a result, the concave portion region of the concrete structure is filled with the salt-shielding mortar, and a concrete structure integrated with the salt-shielding mortar can be obtained.

In the construction process, an alumina cement composition for salt-shielding mortar that satisfies the following conditions 1) to 4) is used. Therefore, according to the construction method of the salt-shielding mortar of the present embodiment, excellent salt-shielding property, excellent long-term durability (for example, excellent strength maintenance performance at high temperature curing), and excellent crack resistance. And can be realized.

1) It 2) alumina cement comprising alumina cement and gypsum hemihydrate is, CA55 mass% to 75 _{mass%, C} 12 _{A 7} 5 wt% to 8 _wt%, C 4 AF10 wt% to 28 wt% and _C 2 AS2 including wt% to 6 wt% 3) Blaine specific surface area of the alumina ^{cement, 2000cm 2 / g~4000cm 2 / g} 4 it is) to the alumina cement 100 parts by weight, the hemihydrate gypsum 15 parts by weight to 35 Contains by mass

The salt-shielding property is based on the test method described in JSCE-G571-2010 "Test method for effective diffusion coefficient of chloride ions in concrete by electrophoresis (draft)", and "Appendix (reference) electrophoresis". It can be obtained by using the "apparent diffusion coefficient calculation method using the effective diffusion coefficient by the test".

The compressive strength can be measured according to the test method described in JIS R 5201-2015 “Physical test method for cement”.

The crack resistance can be determined by a test method for a length change amount (shrinkage amount) described later.

The apparent diffusion coefficient of the salt-shielding mortar cured product measured by the above test method is preferably 0.14 cm ² / year or less, more preferably 0.12 cm ² / year or less, and further preferably 0. .10 cm ² / year or less.

The compressive strength of the salt-shielding mortar cured product measured by the above test method at 20 ° C. and 28 days of age is preferably 40 N / mm ² or more, more preferably 45 N / mm ² or more, still more preferable. Is 50 N / mm ² or more.

The rate of change in compressive strength of the salt-shielding mortar cured product measured by the above test method at 50 ° C. and 28 days of age is preferably -15% or more, more preferably -12% or more, still more preferable. Is -5% or more, more preferably 0% or more. Here, when the sign of the rate of change in compressive strength is minus (−), it indicates that the compressive strength at the age of 28 days (50 ° C.) is lower than the compressive strength at the age of 28 days (20 ° C.).

The length change amount of the salt-shielding mortar cured product obtained by the method for measuring the length change amount (shrinkage amount) described later is preferably −200 μm / m or more, more preferably −150 μm / m or more. , More preferably −120 μm / m or more. Here, when the sign of the length change amount is minus (-), it indicates that the salt-shielding mortar cured product is contracted.

By keeping the apparent diffusion coefficient, compressive strength, compressive strength change rate and length change amount during high-temperature curing within the above ranges, it is more excellent in integrating the salt-shielding mortar hardened body with the concrete structure. It is possible to realize salt barrier property, better long-term durability, and better crack resistance.

Hereinafter, the salt-shielding mortar used in the present embodiment will be described in detail.

(Alumina cement composition for salt-shielding mortar)
The alumina cement composition for salt-shielding mortar used in the present invention is an alumina cement composition for salt-shielding mortar containing alumina cement and hemihydrate gypsum.

In barrier salt mortar for alumina cement compositions used in the present invention, alumina cement, CA55 mass% to 75 _{mass%, C} 12 _{A 7} 5 wt% to 8 _wt%, C 4 AF10 wt% to 28 wt% and C ₂ AS contains 2% by mass to 6% by mass. Blaine specific surface area of the alumina cement ^is 2000cm ² / g~4000cm 2 / g. The alumina cement composition for salt-shielding mortar used in the present invention contains 15 parts by mass to 35 parts by mass of hemihydrate gypsum with respect to 100 parts by mass of alumina cement. Therefore, by using the alumina cement composition for salt-shielding mortar used in the present invention, excellent salt-shielding property, excellent long-term durability and excellent crack resistance can be realized.

(Alumina cement)
The alumina cement composition for salt-shielding mortar used in the present invention contains alumina cement. The main component of alumina cement is calcium aluminate. Examples of calcium aluminate preferably used as the main component of aluminum cement include CA, C ₁₂ A ₇ , C ₄ AF, C ₂ AS and the like. The alumina cement may contain only one of these calcium aluminates, or may contain a plurality of types of calcium aluminates.

Among the alumina cement, the alumina cement containing CA 55% by mass to 75% by mass, C ₁₂ A ₇ 5% by mass to 8% by mass, C ₄ AF 10% by mass to 28% by mass, and C ₂ AS 2% by mass to 6% by mass Preferredly used, CA 58% by mass to 72% by mass, C ₁₂ A ₇ 5.6% by mass to 7.8% by mass, C ₄ AF 13% by mass to 25% by mass, C ₂ AS 2.5% by mass to 5.5% by mass. Alumina cement containing% is more preferably used, CA 62% by mass to 68% by mass, C ₁₂ A ₇ 5.4% by mass to 7.6% by mass, C ₄ AF 16% by mass to 22% by mass, C ₂ AS 3.0. Alumina cement containing% by mass to 5.0% by mass is more preferably used. By using alumina cement having the above composition, salt shielding property, long-term durability and crack resistance can be further improved.

Blaine specific surface area of the alumina cement ^is 2000cm ² / g~4000cm 2 / g, and preferably is 2500cm ² / g~3500cm ² / g, more preferably 2700cm ² / g~3300cm ² / g. By setting the brain specific surface area of the alumina cement to the above range, the hydration reaction of the alumina cement composition for salt-shielding mortar proceeds suitably, and a dense mortar cured product can be produced. The brain specific surface area of the alumina cement composition for salt-shielding mortar can be determined according to JIS R 2521: 2015.

(Semi-water plaster)
The alumina cement composition for salt-shielding mortar used in the present invention contains hemihydrate gypsum. As the hemihydrate gypsum, either α-type hemihydrate gypsum or β-type hemihydrate gypsum can be used. Both α-type hemihydrate gypsum and β-type hemihydrate gypsum may be mixed and used.

The content of hemihydrate gypsum in the alumina cement composition for salt-shielding mortar used in the present invention is 15 parts by mass to 35 parts by mass, preferably 18 parts by mass to 32 parts by mass with respect to 100 parts by mass of alumina cement. It is more preferably 22 parts by mass to 28 parts by mass. By setting the content of hemihydrate gypsum within the above range, the amount of shrinkage during curing can be further reduced. Therefore, the crack resistance can be further improved.

Blaine specific surface area of the hemihydrate gypsum is preferably 3500cm ² / g~12000cm ² / g, more preferably from 3500cm ² / g~10000cm ² / g, more preferably 3500cm ² / g~5500cm ² / g , and still more preferably from 4000cm ² / g~5000cm ² / g, more preferably from 4200cm ² / g~4600cm ² / g. By setting the brain specific surface area of the hemihydrate gypsum within the above range, the amount of shrinkage during curing can be further reduced. Therefore, the crack resistance can be further improved. The brain specific surface area of hemihydrate gypsum can be determined according to JIS R 5201: 2015.

(Other ingredients)
The alumina cement composition for salt-shielding mortar used in the present invention may further contain components other than alumina cement and hemihydrate gypsum as long as the effects of the present invention are not impaired.

(Calcium carbonate)
The alumina cement composition for a salt-shielding mortar used in the present invention may contain calcium carbonate. As the calcium carbonate, for example, chemically purified calcium carbonate may be used, or a material containing calcium carbonate as a main component, such as limestone fine powder obtained by crushing limestone or crushed waste concrete or the like, can be used. .. Limestone is more preferably used from the viewpoint of reducing the raw material cost of the alumina cement composition for salt-shielding mortar. The alumina cement composition for a salt-shielding mortar used in the present invention may contain only one type of calcium carbonate, or may contain a plurality of types of calcium carbonate.

The content of calcium carbonate is preferably 15 parts by mass to 35 parts by mass, more preferably 18 parts by mass to 32 parts by mass, and 20 parts by mass to 30 parts by mass with respect to 100 parts by mass of alumina cement. It is more preferable to have. By setting the content of calcium carbonate in the above range, long-term durability can be further improved.

Blaine specific surface area of calcium carbonate ^is preferably 3500cm ² / g~5500cm 2 / ^g, more preferably 4000cm ² / g~5000cm 2 / ^g, is 4300cm ² / g~4700cm 2 / g Is even more preferable. By setting the brain specific surface area of calcium carbonate within the above range, the compressive strength and long-term durability can be further improved. The specific surface area of calcium carbonate can be determined according to JIS R5201: 2015.

(Silica fume)
The alumina cement composition for a salt-shielding mortar used in the present invention may contain silica fume. Preferred silica fume includes, for example, silica fume specified in JIS A 6207-2006 "Silica fume for concrete". By containing silica fume in the alumina cement composition for salt-shielding mortar used in the present invention, the cured mortar can be densified, so that a cured mortar with higher strength and better salt-shielding property can be realized. obtain. The alumina cement composition for a salt-shielding mortar used in the present invention may contain only one type of silica fume, or may contain a plurality of types of silica fume.

The content of silica fume is preferably 5 parts by mass to 12 parts by mass, more preferably 6 parts by mass to 11 parts by mass, and further preferably 7 parts by mass to 9 parts by mass with respect to 100 parts by mass of alumina cement. Is. By setting the content of silica fume in the above range, long-term durability and salt-shielding property can be further improved.

BET specific surface area of silica fume is a preferably ^{11m 2} / ^g~22m 2 / g, more preferably ^{12m 2} / ^g~21m 2 / g, more preferably ^{13m 2} / ^g~20m 2 / g .. By setting the BET specific surface area of silica fume within the above range, long-term durability and salt-shielding properties can be further improved.

(Fine aggregate)
The alumina cement composition for a salt-shielding mortar used in the present invention may contain a fine aggregate. Examples of fine aggregates preferably used include sands such as silica sand, river sand, land sand, sea sand, and crushed sand. The alumina cement composition for a salt-shielding mortar used in the present invention may contain only one kind of fine aggregate, or may contain a plurality of kinds of fine aggregate.

The content of the fine aggregate is preferably 50 parts by mass to 250 parts by mass, more preferably 80 parts by mass to 200 parts by mass, and further preferably 110 parts by mass to 180 parts by mass with respect to 100 parts by mass of alumina cement. It is by mass, more preferably 130 parts by mass to 165 parts by mass. By setting the content of the fine aggregate in this way, the salt-shielding property and the strength can be further improved.

As the fine aggregate, a fine aggregate is preferably used, which does not contain particles having a particle diameter of 1700 μm or more and has a mass ratio of particles having a particle diameter of 1200 μm or more of 20% by mass or less with respect to the entire fine aggregate. By setting the content of coarse particles having a particle size of 1200 μm or more to 20% by mass or less, the homogeneity in the cured mortar obtained from the alumina cement composition for salt-shielding mortar can be improved, so that the salt-shielding property can be improved. It can be further improved. From the viewpoint of realizing better salt shielding property, the mass ratio of the particles having a particle diameter of 1200 μm or more is more preferably 0.05% by mass to 20% by mass, still more preferably 0, with respect to the entire fine aggregate. It is 0.01% by mass to 15% by mass, more preferably 0.05% by mass to 10% by mass, and further preferably 0.1% by mass to 3% by mass.

The particle size of the fine aggregate can be measured using several sieves having different nominal dimensions specified in JIS Z8801-2006. In the present invention, the "mass ratio of particles having a particle diameter of 1200 μm or more" refers to the mass ratio of particles remaining on the sieve when a sieve having a mesh size of 1200 μm is used.

(Fluidizer)
The alumina cement composition for a salt-shielding mortar used in the present invention may contain a fluidizing agent. Preferred fluidizing agents include, for example, a formaldehyde condensate of melamine sulfonic acid, casein, casein calcium, a polycarboxylic acid-based fluidizing agent, a polyether-based fluidizing agent, and poly, which have both a water-reducing effect and suitable fluidity. Examples include ether carboxylic acid. Among them, a polycarboxylic acid-based fluidizing agent, a polyether-based fluidizing agent, and a polyether carboxylic acid are more preferably used as the fluidizing agent, and a polycarboxylic acid ester is further preferably used. The alumina cement composition for a salt-shielding mortar used in the present invention may contain only one type of fluidizing agent, or may contain a plurality of types of fluidizing agents.

The content of the fluidizing agent is preferably 0.02 parts by mass to 1.00 parts by mass, more preferably 0.04 parts by mass to 0.50 parts by mass, and further preferably 0 with respect to 100 parts by mass of alumina cement. It is 0.7 part by mass to 0.40 part by mass, more preferably 0.10 part by mass to 0.30 part by mass. By setting the content of the fluidizing agent in the above range, the long-term durability of the cured mortar can be further improved, and the suitable fluidity of the mortar can be realized.

(Condensation retarder)
The alumina cement composition for a salt-shielding mortar used in the present invention may contain a setting retarder. Examples of the setting retarder preferably used include organic acids such as oxycarboxylic acids, saccharides such as glucose, maltose and dextrin, sodium bicarbonate, sodium phosphate and the like. Specific examples of the oxycarboxylic acids include oxycarboxylic acids and salts thereof. Specific examples of the oxycarboxylic acid include aliphatic oxy acids such as citric acid, gluconic acid, tartrate acid, glycolic acid, lactic acid, hydroacrylic acid, α-oxybutyric acid, glyceric acid, tartronic acid and malic acid, salicylic acid, and the like. Examples thereof include aromatic oxy acids such as m-oxybenzoic acid, p-oxybenzoic acid, galvanic acid, mandelic acid and tropic acid. Examples of the salt of oxycarboxylic acid include alkali metal salts (specifically, sodium salt and potassium salt, etc.) and alkaline earth metal salts (specifically, calcium salt, barium salt, magnesium salt, etc.) and the like. .. Among these, a sodium salt is more preferably used, sodium tartrate is more preferably used, and it is further preferable to use sodium tartrate and sodium bicarbonate in combination. The alumina cement composition for a salt-shielding mortar used in the present invention may contain only one type of setting retarder, or may contain a plurality of types of setting retarding agents.

The content of the setting retarder is preferably 0.01 part by mass to 2 parts by mass, more preferably 0.1 part by mass to 1.5 parts by mass, still more preferably, with respect to 100 parts by mass of alumina cement. Is 0.3 parts by mass to 1.2 parts by mass, more preferably 0.5 parts by mass to 1.0 part by mass. By setting the content of the setting retarder within the above range, a suitable pot life can be secured.

(Synthetic resin fiber)
The alumina cement composition for a salt-shielding mortar used in the present invention may contain synthetic resin fibers. By containing the synthetic resin fiber, it is possible to effectively suppress the occurrence of cracks in the cured mortar.

Preferred synthetic resin fibers include, for example, polyolefins such as polyethylene, ethylene-vinyl acetate copolymer (EVA) and polypropylene; synthetic resin components such as polyester, polyamide, polyvinyl alcohol, vinylon and polyvinyl chloride. .. The alumina cement composition for a salt-shielding mortar used in the present invention may contain only one kind of synthetic resin fiber, or may contain a plurality of kinds of synthetic resin fiber.

The fiber length of the synthetic resin fiber is preferably 0 from the viewpoint of handleability when mixed with the salt-shielding alumina cement composition, improvement of dispersibility in the salt-shielding mortar composition, and improvement of the characteristics of the cured mortar. It is .5 mm to 15.0 mm, more preferably 1.0 mm to 12.0 mm, still more preferably 2.0 mm to 8.0 mm, still more preferably 2.5 mm to 7.0 mm.

The content of the synthetic resin fiber is preferably 0.01 part by mass to 3 parts by mass, more preferably 0.03 part by mass to 1 part by mass, and further preferably 0. It is 04 parts by mass to 0.3 parts by mass, more preferably 0.05 parts by mass to 0.15 parts by mass.

By adjusting the fiber length and content of the synthetic resin fiber within the above range, the crack resistance of the cured mortar can be further improved without impairing the salt-shielding property and durability.

(Synthetic resin emulsion, synthetic resin powder)
The alumina cement composition for a salt-shielding mortar according to the present invention may contain a synthetic resin emulsion or a synthetic resin powder. By containing a synthetic resin emulsion or a synthetic resin powder, the salt-shielding property can be further improved. Here, the "synthetic resin emulsion" refers to those in which synthetic resin particles are emulsified and dispersed in water or a water-containing solvent.

The glass transition temperature (Tg) of the synthetic resin component contained in the synthetic resin emulsion is preferably 0 ° C. or higher, more preferably 5 ° C. or higher, still more preferably 10 ° C. or higher, and particularly preferably 15 ° C. or higher. When such a synthetic resin emulsion is used, excellent adhesiveness is realized even when the concrete base is in a wet state, and workability is also improved. From the same viewpoint, the glass transition temperature (Tg) of the synthetic resin powder is preferably 0 ° C. or higher, more preferably 5 ° C. or higher, still more preferably 10 ° C. or higher, and particularly preferably 15 ° C. or higher.

The glass transition temperature (Tg) of the synthetic resin component contained in the synthetic resin emulsion is determined by dropping an appropriate amount of the synthetic resin emulsion onto a glass plate and drying to obtain a dry coating film, and then using a differential scanning calorimeter (DSC). Can be measured under the following conditions. The glass transition temperature (Tg) of the synthetic resin component contained in the synthetic resin powder can be measured as it is in the powder using a differential scanning calorimeter (DSC) under the following conditions. In the present specification, the method of measuring the glass transition temperature (Tg) of the synthetic resin component using a differential scanning calorimeter is referred to as a DSC method.

The dry coating film of the synthetic resin emulsion or the synthetic resin powder is heated from room temperature to 150 ° C. for 10 minutes, held at 150 ° C. for 10 minutes, and then the temperature is raised to a temperature 50 ° C. lower than the Tg of the calculated sample. Lower. Then, the temperature is raised to 150 ° C. again in 10 minutes. In the process, the first glass transition temperature (Tg) is measured, and then the second Tg is measured in the process of lowering the temperature to 50 ° C lower than the first measured Tg, and this second Tg measurement is performed. The value is taken as the glass transition temperature of the synthetic resin emulsion.

Examples of the synthetic resin emulsion preferably used include acrylic emulsions and vinyl acetate emulsions. Examples of the synthetic resin of the synthetic resin emulsion include (meth) acrylic acid, (meth) acrylic acid ester and other (meth) acrylic acid derivatives; α-olefin compounds such as ethylene and vinyl acetate; vinyl compounds such as styrene; butadiene. Examples thereof include a polymer or a copolymer of a polymerization component such as.

Among them, an acrylic emulsion is more preferably used from the viewpoint of achieving excellent salt-shielding properties. Examples of the acrylic emulsion include (meth) acrylics such as acrylic acid and methacrylic acid; polymers of (meth) acrylic acid derivatives such as (meth) acrylic acid esters; and polymers of (meth) acrylic acid derivatives and styrene. Can be mentioned. Specifically, examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. The alumina cement composition for a salt-shielding mortar used in the present invention may contain only one kind of synthetic resin emulsion, or may contain a plurality of kinds of synthetic resin emulsions.

The content of the synthetic resin emulsion is preferably 1 part by mass to 10 parts by mass, more preferably 2 parts by mass, in terms of solid content with respect to 100 parts by mass of the powder portion of the alumina cement composition for salt-shielding mortar. It is 7 parts by mass to 7 parts by mass, more preferably 2.5 parts by mass to 6 parts by mass, and further preferably 3 parts by mass to 5 parts by mass.

The solid content of the synthetic resin emulsion is the mass of the solid content remaining after evaporating the water content in the synthetic resin emulsion. Moisture in the synthetic resin emulsion is obtained by subtracting the solid content from the synthetic resin emulsion. Further, the powder portion of the alumina cement composition for salt-shielding mortar means a powder portion excluding the liquid component when the alumina cement composition for salt-shielding mortar contains a liquid component. When the alumina cement composition for salt-shielding mortar does not contain liquid components and consists only of powder components, the powder part of the alumina cement composition for salt-shielding mortar is the alumina cement composition for salt-shielding mortar. It means the whole thing. By setting the content of the synthetic resin emulsion within the above range, the adhesiveness to concrete and the salt-shielding property can be further improved.

Specific examples of the synthetic resin powder preferably used include styrene / acrylic copolymers, acrylics, vinyl acetate / beova / acrylic copolymers, ethylene-vinyl acetate copolymers and the like.

The content of the synthetic resin powder is preferably 0.1% by mass to 10% by mass, more preferably 0.3% by mass, based on 100 parts by mass of the powder portion of the alumina cement composition for salt-shielding mortar. % To 5.0% by mass, more preferably 1.0% by mass to 3.0% by mass.

Hereinafter, the present invention will be described in more detail based on specific examples, but the present invention is not limited to the following examples, and the present invention is appropriately modified without changing the gist thereof. It is possible to do.

(Examples 1 to 4, Comparative Examples 1 to 3)
In an atmosphere of a temperature of 20 ° C. and a humidity of 65% RH, the raw materials were mixed at the blending ratios shown in Table 1 below to obtain an alumina cement composition for a salt-shielding mortar. Next, the mass ratio of the total amount (P) of the powder and the amount of water (W) in the alumina cement composition for salt-shielding mortar to 2.0 kg of the obtained alumina cement composition for salt-shielding mortar. Water was added so that W / P = 0.128, and the mixture was mixed with a Chemisterler for 2 minutes to obtain a mortar.

The blending ratio of each component A1, A2, B1, B2, B3, B4, C, D1, D2, D3, D4, and E shown in Table 1 is the mass part when the hydraulic component is 100 parts by mass. Shows.

(evaluation)
(1) Salt barrier (apparent diffusion coefficient of chloride ions)
For each obtained mortar, the electricity of chloride ions is based on the concrete standard specification JSCE-G 571-2013 "Effective diffusion coefficient test method of chloride ions in concrete by electrophoresis (draft)" edited by the Japan Society of Civil Engineers. ^{Perform a migration test and obtain the apparent diffusion coefficient (cm 2} / year) of chloride ions in the mortar based on the "Appendix (reference) method for calculating the apparent diffusion coefficient using the effective diffusion coefficient by the electrophoresis test". rice field. The results are shown in Table 1.

(2) Compressive strength For each of the obtained mortars, the compressive strength after 28 days of age was measured at water curing temperatures of 20 ° C. and 50 ° C., respectively, in accordance with JIS R 5201 “Physical test method for cement”. From the measured value, the rate of change in compressive strength was calculated based on the following formula. The results are shown in Table 1.
x = (y2-y1) × 100 / y1
However,
x: Compressive strength change rate (%)
^{y1: Compressive strength (N / mm 2} ) after 28 days of age at a water curing temperature of 20 ° C.
^{y2: Compressive strength (N / mm 2} ) after 28 days of age at a water curing temperature of 50 ° C.
Is.

(3) Length change amount (shrinkage amount)
FIG. 1 is a schematic cross-sectional view of an apparatus for measuring the amount of change in length during curing of a salt-shielding mortar. FIG. 2 is a schematic cross-sectional view taken along the line (b)-(b) of FIG.

First, the configuration of a device for measuring the amount of change in length during curing of the salt-shielding mortar will be described. As shown in FIG. 1, the length change amount measuring device 10 includes a mold 11. A salt-shielding mortar is placed in the accommodating portion 20 formed by the formwork 11. In the length change amount measuring device 10 used in this embodiment, the height (h) of the mold 11 is 30 mm and the width (W) is 40 mm (see FIG. 2).

A cushioning material 14 is provided on each of the inner and outer surfaces of the side wall located at one end in the longitudinal direction of the formwork 11. A rod 13a is provided so as to penetrate both the side wall and the cushioning material 14 provided on both side surfaces of the side wall. The rod 13a is provided so as to be displaceable in the longitudinal direction of the length change amount measuring device 10. Discs 12a and 12b are provided at both ends of the rod 13a, respectively. The rods 13a and the discs 12a and 12b are made of SUS. Here, SUS refers to a stainless steel material specified in JIS.

A rod 13b is provided inside the side wall located at the other end of the formwork 11 in the longitudinal direction. The rod 13b does not penetrate the side wall. A disk 12c is provided at the tip of the rod 13b. Specifically, the disk 12c is provided at the end of the rod 13b on the side opposite to the side wall side of the mold 11. The disk 12c faces the disk 12b in the longitudinal direction of the formwork 11.

The distance d between the disc 12b and the disc 12c before the measurement is 210 mm.

As shown in FIG. 2, a fluororesin sheet 16 is provided on the inner wall surface of the mold 11.

When salt-shielding BR> c crying is placed in the mold 11, when the salt-shielding mortar shrinks, the disks 12a and 12b are arrowed from the position before measurement as the salt-shielding mortar shrinks. Displace in the direction of x. On the other hand, when the salt-shielding mortar expands, the disks 12a and 12b are displaced in the direction of the arrow y from the position before the measurement. Outside the mold 11, a laser displacement sensor 15 capable of measuring the displacement of the disk 12a in the x direction is provided.

The salt-shielding mortar immediately after kneading obtained in each of Examples 1 and Comparative Examples 1 to 3 was cast into the accommodating portion 20 of the mold 11 to the height of the mold, and the temperature was 20 ° C. and the humidity was 65% RH. Curing was performed in the air, and the amount of change in length 24 hours after casting was measured.

The amount of change in length of the salt-shielding mortar was calculated based on the following formula. The results are shown in Table 1.
Length change = (a × 1000) / d
However,
a: Displacement amount (μm) of hydraulic mortar after 24 hours of curing
d: Distance between the disc 12b and the disc 12c before curing d (2100 mm)
In Table 1, when the amount of change in length is a negative value, it indicates that it has contracted due to curing, and when it is a positive value, it indicates that it has expanded due to curing.

A1, A2, B1, B2, B3, B4, C, D1, D2, D3, D4, and E shown in Table 1 are as follows.

(1) Water-hardening component A1: Alumina cement (brain specific surface area 3100 cm ² / g, mineral content ratio: CA: 64.8 mass%, C ₁₂ A ₇ : 6.6 mass%, C ₄ AF: 18.3 mass %, C ₂ AS: 4.1% by mass)
A2: Ordinary Portland cement (brain specific surface area 2500 cm ² / g)

(2) Admixture B1: Phosphoric anhydride gypsum (brain specific surface area 4140 cm ² / g, mass ratio of particles with a particle size of 300 μm or more 2%, mass ratio of particles with a particle size of less than 150 μm 85%)
B2: Semi-hydrated gypsum (brain specific surface area 4380 cm ² / g)
B3: Calcium carbonate (brain specific surface area 4480 cm ² / g)
B4: Silica fume (BET specific surface area 19 m ² / g)

(3) Fine aggregate C: Silica sand (does not contain particles with a particle diameter of 1700 μm or more, and the mass ratio of particles with a particle diameter of 1200 μm or more is 1.48% by mass with respect to the entire fine aggregate, and particles with a particle diameter of 600 μm or more The mass ratio is 49.13 mass%, the mass ratio of particles with a particle diameter of 300 μm or more is 44.04 mass%, the mass ratio of particles with a particle diameter of 150 μm or more is 4.06 mass%, and the mass ratio of particles with a particle diameter of 75 μm or more. Is 1.26% by mass)

(4) Admixture D1: Sodium gluconate D2: Sodium tartrate D3: Sodium bicarbonate D4: Polycarboxylic acid-based water reducing agent

(5) Synthetic resin powder E: Styrene / acrylic copolymer resin powder (glass transition temperature Tg: 21 ° C)
Tg was measured by the DSC method.

10: Length change amount measuring device 11: Formwork 12a, 12b, 12c: Disk 13a, 13b: Rod 14: Cushioning material 15: Displacement sensor 16: Fluororesin sheet 20: Accommodating part

Claims (3)

A construction process for constructing a salt-shielding mortar prepared by kneading an alumina cement composition for salt-shielding mortar and water on a concrete structure.
A forming step of forming a salt-shielding mortar cured product by curing the salt-shielding mortar, and
It is a construction method of salt-shielding mortar equipped with
As the alumina cement composition for salt-shielding mortar,
Contains alumina cement and semi-hydrated gypsum
The alumina cement comprises CA55 wt% to 75 _{wt%, C} 12 _{A 7} 5 wt% to 8 _wt%, the C 4 AF10 wt% to 28 wt% and _C 2 AS2 wt% to 6 wt%,
Blaine specific surface area of the alumina cement ^is 2000cm ² / g~4000cm 2 / g,
A method for constructing a salt-shielding mortar containing 15 parts by mass to 35 parts by mass of the hemihydrate gypsum with respect to 100 parts by mass of the alumina cement. The method for constructing a salt-shielding mortar according to claim 1, wherein the alumina cement composition for salt-shielding mortar further contains at least one of calcium carbonate and silica fume. Claim 2 that the alumina cement composition for a salt-shielding mortar contains 15 parts by mass to 35 parts by mass of the calcium carbonate and 5 parts by mass to 12 parts by mass of the silica fumes with respect to 100 parts by mass of the alumina cement. Construction method of salt-shielding mortar described in.

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