JP5697357B2 - Spraying mortar with low electrical resistance, mortar hardened body for spraying, and method for preventing corrosion of steel in concrete structure using the same - Google Patents

Description

  The present invention relates to a mortar for spraying used for electric protection of a concrete structure subjected to corrosion by a steel material due to salt damage, a cured body using the same, and a method for preventing corrosion of a steel material inside the concrete structure using the mortar.

When a steel material such as a reinforcing bar in a concrete structure is exposed to a state of a certain salt concentration or more, a corrosion battery is generated, and an electric corrosion is generated in the steel material serving as an anode.
As a means for preventing such corrosion of steel caused by the generation of corrosion batteries, an anode is installed in a concrete structure, and a direct current is allowed to flow from the anode to the steel in the concrete, thereby making the steel in the concrete. An anti-corrosion method that controls the electric potential of the steel and electrochemically suppresses the corrosion reaction of the steel material is recommended, and is used as one of the repair methods for concrete structures.

  For example, there is a corrosion prevention method in which an anode is installed in concrete near the surface, and current is continuously passed from the anode toward a steel material (cathode) in the concrete. As long as this current flows appropriately, the progress of deterioration due to corrosion of the steel material can be suppressed.

However, with this method, as the time elapses, the anticorrosion current necessary for anticorrosion decreases, and it has been difficult to maintain an effective potential difference between the anode and the steel material over a long period of time.
As the anode material used in this anticorrosion method, titanium-based or carbon-based rods or ribbons are often used. In order to reduce the resistivity of the anode or to prevent inactivation, the anode material is used. It is necessary to fill and cover the periphery of the anode with a protective material to protect the performance of the steel and integrate it with the existing concrete. Mortar is used as this protective material.

  In order to increase the anticorrosion effect of the steel material, it is necessary to reduce the electrical resistance of the hardened mortar filled around the anode so that the current flows easily. In addition, when cracks occur in the cured mortar, it is difficult for current to flow, so it is necessary to reduce the shrinkage that is the cause of the cracks.

In order to reduce the electrical resistance of the mortar cured body, it is preferable to increase the amount of free water in the mortar cured body by increasing the water binder ratio and unit water amount.
However, when the water binder ratio and the unit water amount are increased, the flowability of the mortar increases and sagging occurs, so that it may not be used as it is. Further, when the water binder ratio and the unit water amount are increased, drying shrinkage increases, so it is difficult to achieve both reduction in electrical resistance and reduction in shrinkage.

As a method for reducing the electric resistance of the mortar cured body, a method using mortar containing lithium nitrite or clay mineral has been proposed (see Patent Document 1 and Patent Document 2).
However, there is a problem that moisture is dissipated from the surface of the cured mortar body due to drying, and electrical resistance increases in the long term.

  On the other hand, as a method for reducing the shrinkage of the cured mortar, an expansion material, a shrinkage reducing agent, and fibers are used in combination, and as the expansion material to be used, two types of expansion materials having different compositions and particle sizes are used in combination. Has been proposed (see Patent Document 3 and Patent Document 4).

By applying organic-inorganic composite coating curing agent to the surface of mortar and concrete hardened bodies, in addition to reducing moisture dissipation due to drying and suppressing drying shrinkage, neutralization and external It has been proposed to suppress salt penetration (see Patent Document 5).
However, it is not known what effect the application of the organic-inorganic composite type film curing agent to the surface of a cured body of mortar or concrete will have on the electrical resistance.

  In cathodic protection, when oxygen is generated from the anode and the potential of the anode rises to the chlorine generation potential, chloride ions that have moved to the anode side by electrophoresis become hypochlorous acid or chlorine gas, which deteriorates the mortar near the anode. Therefore, it is necessary to make these hypochlorous acid and chlorine gas permeate easily in the mortar cured body.

JP 2005-281037 A JP 2006-248792 A JP 2007-238745 A JP 2007-320832 A JP 2007-308354 A

  The present invention provides a spraying mortar that does not sag even when the water binder ratio is increased, has low electrical resistance, and has low shrinkage. Moreover, the corrosion prevention method of the steel materials inside a concrete structure using the mortar hardening body which reduces shrinkage further, keeps electrical resistance small for a long term, and does not prevent permeation | transmission of chlorine gas etc. is provided.

In order to solve the above problems, the present invention has the following configuration.
(1) A mortar composition containing cement-containing binder, fine aggregate, water reducing agent, and water is used. The water binder ratio is 35 to 55%, and the unit water volume is 250 to 400 kg / m ^3. Obtained by adding 0.3 to 5.0 parts in terms of solid content of sodium aluminate to 100 parts of cement to a mortar with a 0-stroke mortar flow value of 200 to 320 mm prepared using a mortar formulation of A spraying mortar with a body electrical resistivity of 100 kΩ · cm or less and a length change rate of −800 × 10 ⁻⁶ or less.
(2) A mortar cured body obtained by curing the spraying mortar.
(3) A mortar cured body obtained by applying an organic-inorganic composite coating film curing agent to the surface of the mortar cured body.
(4) The mortar cured body according to (3), wherein the organic-inorganic composite-type film curing agent contains a synthetic resin aqueous dispersion, a water-soluble resin, and a swellable clay mineral.
(5) The mortar cured body according to (4), wherein the swellable clay mineral of the organic-inorganic composite-type coating film curing agent is a synthetic fluorine mica.
(6) The mortar cured body according to any one of (3) to (5), wherein the organic-inorganic composite-type coating curing agent is used in an amount of 100 to 500 g / m ² .
(7) Using the mortar cured body of (2) above , an anode is installed in a concrete structure, and a direct current is continuously passed from the anode to the steel material in the concrete, thereby inhibiting the corrosion reaction of the steel material electrochemically. This is an anticorrosion method for steel inside a concrete structure.
(8) Using the mortar hardened body according to any one of (3) to (6) above, by installing an anode in a concrete structure and continuously flowing a direct current from the anode to the steel material in the concrete, This is a method for preventing corrosion of a steel material inside a concrete structure, which electrochemically suppresses the corrosion reaction of the steel material.

The present invention provides a mortar for spraying that does not sag even when the water binder ratio is increased, has low electrical resistance, and has low shrinkage. Further, the present invention provides a corrosion prevention method for spraying mortar that further reduces shrinkage, keeps electric resistance small in the long term, and does not prevent permeation of chlorine gas or the like.
By using these for electrocorrosion protection, a high anticorrosion effect is obtained in the anticorrosion of the steel material in the concrete structure.

Hereinafter, the present invention will be described in detail.
In the present invention, “part” and “%” are based on mass unless otherwise specified.

In the present invention, a cement-containing binder, fine aggregate, water reducing agent and the like are used, the water binder ratio is 35 to 55%, the unit water amount is 250 to 400 kg / m ³ , and the zero-stroke mortar flow value is 200 to Add 0.3 to 5.0 parts of sodium aluminate to 320 parts of cement with high fluidity of 320 mm. The electrical resistivity of the hardened mortar is 100 kΩ · cm or less, and the rate of change in length is -800. Prepare spraying mortar that is × 10 ^-6 or less.

In the present invention, a binder containing cement is used.
The binder refers to cement or a combination of cement and various admixtures such as silica fume, blast furnace granulated slag, fly ash, expansion material, rapid hardening material, and high-strength admixture used in combination as necessary.

  As the cement used in the present invention, various portland cements such as normal, early strength, very early strength, low heat, and moderate heat, various mixed cements obtained by mixing these portland cements with blast furnace slag, fly ash, or silica, , Limestone powder and blast furnace slow-cooled slag fine powder, and environmentally friendly cement made from various industrial wastes as main raw materials, so-called eco-cement. More than species can be used.

The fine aggregate used in the present invention is not particularly limited. Specific examples thereof include silica sand, lime sand, blast furnace granulated slag fine aggregate, recycled fine aggregate, and heavy fine aggregate.
In addition, blast furnace slow-cooled slag fine aggregate, electric furnace oxidation stage slag fine aggregate, and non-ferrous smelted slag fine aggregate that collectively refers to ferronickel slag, ferrochrome slag, copper slag, zinc slag, lead slag, etc. , Peridotite fine aggregates, so-called olivine sand, emery ore and the like. In the present invention, one or more of these can be used.
The amount of fine aggregate used is not particularly limited, and is appropriately adjusted according to the application and required workability.

The water reducing agent used in the present invention is not particularly limited. Specific examples thereof include, for example, naphthalene-based water reducing agents, manufactured by NMB, trade name "Leo Build SP-9" series, Kao Corporation, trade name "Mighty 2000" series, and Nippon Paper Industries, trade name " Sunflow HS-100 ". Examples of the melamine water reducing agent include Nippon Seika Co., Ltd., trade name “Sea Cament 1000” series, Nippon Paper Industries Co., Ltd., trade name “Sunflow HS-40”, and the like. Furthermore, examples of the aminosulfonic acid water reducing agent include a product name “FP-200” series manufactured by Floric. Polycarboxylic acid-based water reducing agents are manufactured by NMB, trade name "Leo Build SP-8" series, Grace Chemicals, trade name "Darlex Super 100PHX", and Takemoto Yushi Co., Ltd., trade name "Tupol HP- 8 "series and" Tupole HP-11 "series. In the present invention, one or more of these water reducing agents can be used.
The amount of water reducing agent used is not particularly limited, and is appropriately adjusted according to the application and required workability.

  In the present invention, limestone fine powder, blast furnace slow-cooled slag fine powder, sewage sludge incinerated ash and its molten slag, municipal waste incinerated ash and its molten slag, pulp sludge incinerated ash, etc. Admixtures, setting modifiers, antifoaming agents, rust inhibitors, antifreeze agents, fiber materials such as steel fibers, vinylon fibers, carbon fibers, and wollastonite fibers, clay minerals such as polymers and bentonite, and hydrotalcite It is possible to use 1 type or 2 types of anion exchangers etc., etc. in the range which does not inhibit substantially the objective of this invention.

In this invention, mortar is prepared using the mortar composition containing a binder, a fine aggregate, water, and a water reducing agent.
The water binder ratio in preparing the mortar is 35 to 55%, preferably 40 to 50%. If the water-cement ratio is less than 35%, the amount of free water in the mortar hardened body will be small, which may increase the electrical resistance and prevent sufficient corrosion protection. If it exceeds 55%, sodium aluminate Even when added, dripping may occur when sprayed.

  Here, the mortar for spraying is a mortar used for spraying, and is required to be free from dripping when sprayed. When sagging occurs, mortar flows through the construction of walls and ceilings. As a measure of sagging, a mortar flow value (15-stroke mortar flow value) according to JIS R 5201 is preferably about 120 to 180 mm. If it is less than 120 mm, the fluidity of the mortar is too small, and the adhesion to concrete may be reduced. If it exceeds 180 mm, sagging may occur.

The unit amount of water in the preparation of mortar is ^{250~400kg / m 3, 289~337kg / m} 3 is preferred. Is less than 250 kg / m ^3, mode for Rutaru amount of free water cured material became less, the electric resistance increases, there is a case where sufficient anticorrosion effect can not be obtained, and when it exceeds 400 kg / m ^3, aluminate Even if sodium is added, sagging may occur.

  The zero-strike mortar flow value refers to a mortar flow value in a stationary state without tapping the flow table in JISR 5201. In the present invention, it is 200 to 320 mm, and preferably 235 to 275 mm. If the thickness is less than 200 mm, the electric resistance may increase and a sufficient anticorrosion effect may not be obtained. If the thickness exceeds 320 mm, material separation may easily occur.

In the present invention, a mortar composition containing cement, fine aggregate, water, and a water reducing agent is used, the water binder ratio is 35 to 55%, the unit water amount is 250 to 400 kg / m ³ , and the zero-stroke mortar flow value. By adding sodium aluminate to a mortar having a high fluidity of 200 to 320 mm, a spraying mortar that does not sag even if the water binder ratio is high is prepared.

  The sodium aluminate used in the present invention promotes the setting of a mortar having a high fluidity to form a dripping mortar. Sodium aluminate includes powder containing water of crystallization, an anhydrous powder, and an aqueous solution, and any of them can be used. However, the use of an aqueous solution is preferable because of good mixing with mortar having high fluidity.

The amount of sodium aluminate used in the present invention is 0.3 to 5.0 parts in terms of solid content with respect to 100 parts of cement. If it is less than 0.1 part, sagging occurs, and if it is added in excess of 10 parts, the compressive strength may be reduced.

  In the present invention, the method for adding sodium aluminate is not particularly limited, but by adding the mortar having a predetermined water binder ratio and unit water amount after kneading, the mortar for good spraying without dripping is added. Is preferred because it is easy to obtain.

  As the mixing device, any existing device can be used, for example, a hand mixer, a grout mixer, a damacut mixer, a biaxial mixer, an omni mixer, a pan mixer, a planetary mixer, and a tilting mixer can be used. is there.

The electric resistivity of the cured mortar is 100 kΩ · cm or less, and the rate of change in length is −800 × 10 ⁻⁶ or less.

The electric resistivity of the cured mortar is 100 kΩ · cm or less, preferably 50 kΩ · cm or less. When the electrical resistivity exceeds 100 kΩ · cm, it becomes difficult for current to flow, and a sufficient anticorrosion effect may not be obtained.

The length change rate of the cured mortar is −800 × 10 ⁻⁶ or less, preferably −600 × 10 ⁻⁶ or less. If the rate of change in length exceeds −800 × 10 ⁻⁶ , cracks are likely to occur, current may not flow easily, and a sufficient anticorrosion effect may not be obtained.

In the present invention, in order to reduce the amount of shrinkage of the cured mortar , that is, in order to make the length change rate to be −800 × 10 ⁻⁶ or less, it is preferable to use an expansion material, a shrinkage reducing agent, and a fiber in combination.

  Here, the expansion material is not particularly limited, and any material can be used. Although the thing containing free lime and free magnesia is mentioned as the kind, From the viewpoint of long-term stability, the expansion | swelling material containing free lime is preferable.

Examples of the expanding material containing free lime include a free lime-anhydrous gypsum-based expanding material, a free lime-hydraulic compound-based expanding material, and a free lime-hydraulic compound-anhydrous gypsum-based expanding material.
In this invention, since expansion | swelling performance is favorable, it is preferable to use a free lime-hydraulic compound-anhydrous gypsum-type expansion | swelling material.

Here, examples of the hydraulic compound include one or more of Auin, calcium ferrite, calcium aluminoferrite, calcium silicate, and calcium aluminate.
In the free lime-hydraulic compound-anhydrous gypsum-based expansive material, the expansive material in which the hydraulic compound is composed of one or more of Auin, calcium ferrite, and calcium aluminoferrite produces slaked lime from the free lime. At the same time, ettringite is also produced from hydraulic compounds and anhydrous gypsum. For this reason, there exist what is called a calcium sulfoaluminate type | system | group expansion | swelling material and what is called an ettringite-lime composite type | system | group expansion | swelling material in connection with ettringite.
As such an expanding material, an expanding material or a static crushing material marketed by each company can be used. A large number of inflatables and static crushed materials are commercially available, and representative examples thereof include those manufactured by Denki Kagaku Kogyo Co., Ltd., trade names “Denka CSA” and “Denka Power CSA”, Sumitomo Osaka Cement Co., Ltd. ", Trade name" Expan "," N-EX "," Breister ", and" Pacific Gypcal "manufactured by Taiheiyo Material.

The particle size of the intumescent material is not particularly limited, but usually it is preferably 2,500 to 10,000 cm ² / g in terms of the specific surface area of the brain (hereinafter referred to as the brain value).
The amount of the expansion material used is preferably 2 to 20 parts with respect to 100 parts of cement.

As the shrinkage reducing agent, the shrinkage reducing component is represented by the general formula RO (AO) nH (R is an alkyl group having 4 to 6 carbon atoms, A is one or two alkylene groups having 2 to 3 carbon atoms, and n is 1 to 10). Or an alkylene oxide adduct of a lower alcohol represented by the general formula X {O (AO) nR} m (where X is a residue of a compound having 2 to 8 hydroxyl groups, AO Is an oxyalkylene group having 2 to 18 carbon atoms, R is a hydrogen atom, a hydrocarbon group having 1 to 18 carbon atoms, or an acyl group having 2 to 18 carbon atoms, n is 30 to 1,000, and m is 2 to 8) A polyoxyalkylene derivative in which 60 mol% or more of the oxyalkylene group is an oxyethylene group can be used.
The amount of shrinkage reducing agent used is preferably 1 to 6 parts per 100 parts of cement.

The fibers are not particularly limited, and commercially available products can be used, and specific examples include high-strength vinylon fibers and polyethylene fibers.
The amount of fiber used is preferably 0.01 to 1.0 part by volume in 100 parts by volume of a mortar composition containing a binder, fine aggregate, and a water reducing agent.

In the present invention, applying an organic-inorganic composite type film curing agent to the surface of the mortar cured body not only can further reduce the shrinkage and suppress cracking, but also can provide long-term electrical resistance of the mortar cured body. Is preferable because it can be kept small.

  In the anticorrosion method, there is coating with an epoxy resin or the like. However, when the epoxy resin or the like is coated, chlorine gas generated at the anode does not permeate, so that the mortar near the anode is deteriorated and the coating film is discolored or peeled off. On the other hand, the organic-inorganic composite type coating curing agent of the present invention suppresses the dissipation of moisture, but chlorine gas and the like permeate slowly, so that the mortar and coating film do not deteriorate.

  The organic-inorganic composite type coating curing agent of the present invention is composed of a synthetic resin aqueous dispersion, a water-soluble resin, and a swellable clay mineral, and these and a crosslinking agent as main components.

Here, the synthetic resin aqueous dispersion is generally a synthetic resin emulsion, and includes an aromatic vinyl monomer, an aliphatic conjugated diene monomer, an ethylenically unsaturated fatty acid monomer, and other co-polymers. It is obtained by emulsion polymerization of one or two or more of polymerizable monomers. For example, styrene / butadiene latex mainly composed of styrene, styrene / acrylic emulsion, methyl methacrylate / butadiene latex copolymerized with styrene, and ethylene / acrylic emulsion. The synthetic resin emulsion is more preferably one having a carboxyl group or a hydroxy group.
Here, the emulsion polymerization is a general emulsion polymerization method in which a monomer to be polymerized is mixed, and an emulsifier, a polymerization initiator, etc. are added to the monomer and the reaction is carried out in an aqueous system.
In order to obtain blending stability with the swellable clay mineral, it is preferable to use a basic substance such as ammonia, amines, and caustic soda and adjust the pH to 5 or more.
The particle diameter of the synthetic resin aqueous dispersion is generally 100 to 300 nm, but preferably has a small particle diameter of about 60 to 100 nm.

Examples of water-soluble resins include modified starch or derivatives thereof, cellulose derivatives, saponified polyvinyl acetate or derivatives thereof, polymers having sulfonic acid groups or salts thereof, polymers or copolymers of acrylic acid or salts thereof, Examples include acrylamide polymers and copolymers, polyethylene glycol, and oxazoline group-containing polymers, and one or more of them can be used.
The water-soluble resin may be one having a solubility in pure water of 1% or more at room temperature, and preferably has 10 to 60% of hydrogen bonding groups or ionic groups per unit weight of the resin.
The average molecular weight is preferably 2,000 to 1,000,000.
The amount of the water-soluble resin used is preferably 0.05 to 200 parts in terms of solid content with respect to 100 parts of solid content of the synthetic resin aqueous dispersion.

Examples of swellable clay minerals include layered silicate minerals belonging to the scumite genus. For example, beidellite, nontronite, saponite, mica and bentonite. Any of natural products, synthetic products, and processed products can be used.
Among them, clay minerals having a swelling power of 20 ml / 2 g or more measured by a method according to the Japan Bentonite Industry Association, standard test method JBAS-104-77, particularly bentonite is preferred.
Further, the ion exchange equivalent is preferably 10 milliequivalents or more per 100 g.
Furthermore, those having an aspect ratio of 50 to 5,000 are preferred. The aspect ratio is the length / thickness ratio of the clay mineral dispersed in a layer form determined by an electron micrograph.
The amount of the swellable clay mineral used is preferably 1 to 50 parts with respect to 100 parts of the solid content of the synthetic resin aqueous dispersion.

A cross-linking agent reacts with a hydrophilic functional group such as a carboxyl group, an amide group, and a hydroxyl group contained in an aqueous dispersion of a water-soluble resin or synthetic resin to crosslink, polymerize (three-dimensional network structure), or hydrophobize. Those having an oxazoline group that undergoes an addition reaction with a carboxyl group are also preferable because they also serve as water-soluble resins.
The amount of the crosslinking agent used is preferably 0.01 to 30 parts in terms of solid content with respect to 100 parts of the total solid content of the synthetic resin aqueous dispersion and the water-soluble resin.

  In the present invention, an organic-inorganic composite type coating curing agent is prepared by mixing an aqueous synthetic resin dispersion, a water-soluble resin, and a swellable clay mineral, and further reacting these with a crosslinking agent. .

  As a method for synthesizing the organic-inorganic composite-type coating curing agent, a method in which a water-soluble resin and a swellable clay mineral are mixed in water in advance and then a synthetic resin aqueous dispersion and a crosslinking agent are mixed.

The organic-inorganic composite-type film curing agent coating method is not particularly limited as long as it can form a uniform curing coating film, and can be distributed, applied, or sprayed. Is possible.
The organic-inorganic composite-type film curing agent is preferably applied to the surface after the setting of the mortar for spraying is completed. Over time, the surface of the mortar dries and cracks tend to occur.
As such an organic-inorganic composite type film curing agent, “RIS full coat” and “Krakoff” manufactured by Denki Kagaku Kogyo Co., Ltd. and “CA2” series manufactured by Toagosei Co., Ltd. can be used.
The mortar cured body of the present invention, by applying a coating film curing agent of the present invention, not only suppress the cracks and further reduce the length variation rate, the electric resistance of the long-term mortar cured body decreases It can maintain and enhance the anti-corrosion effect.

Although the usage-amount of an organic-inorganic composite type coating film curing agent is not specifically limited, 100-500g per 1 m < ² > is preferable and 150-400g is more preferable. If it is less than 100 g, the effect of keeping the electrical resistance small in the long term may not be sufficient, and if it exceeds 500 g, chlorine gas or the like may be difficult to permeate.

  The present invention will be specifically described below with reference to experimental examples, but the present invention is not limited to these experimental examples.

"Experiment 1"
A mortar composition comprising a cement, a binder, a fine aggregate, a water reducing agent, and a fiber composed of an admixture of 5 parts of an expanding material, 5 parts of an expanding material, and 3 parts of a shrinkage reducing agent with respect to 100 parts of cement. The mortar of the mortar flow value shown in Table 1 was prepared using 100 parts by volume of the mortar composition, 0.15 parts by volume of the fiber, and using the mortar composition of the water binder ratio and unit water amount shown in Table 1.
Thereafter, 1 part of sodium aluminate was added to 100 parts of cement and sprayed. The mortar flow value was measured before and after the addition of sodium aluminate, and the presence or absence of dripping after the addition was evaluated. A 4 × 4 × 16 cm specimen was prepared, and the electrical resistivity and the rate of change in length were measured at a material age of 28 days. The mortar for spraying was sprayed on the existing concrete board so as to be 30 cm long, 30 cm wide and 3 cm thick, and the occurrence of cracks was observed at the age of 28 days. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, density 3.15g / cm ³ , brain value 3,100cm ² / g
Expansion material A: Ettlingite-lime composite expansion material, brain value 3,000 cm ² / g
Expansion material B: Calcium sulfoaluminate-based expansion material, brain value 6,000 cm ² / g
Shrinkage reducing agent: powder shrinkage reducing agent, commercial product fiber: vinylon fiber, density 1.30 g / cm ³ , commercial product water reducing agent: β-naphthalenesulfonic acid-based water reducing agent, commercial product fine aggregate: limestone crushed sand, density 2.70 g / cm ³
Sodium aluminate: aqueous solution (solid content 50%), commercial product

<Measurement method>
Mortar flow value: Measure the prepared mortar according to JIS R 5201. However, before the addition of sodium aluminate, the mortar flow value was 0 strokes, and after the addition, the mortar flow value was 15 strokes (values in a stationary state without tapping the flow table and values after 15 taps).
Electrical resistivity: Demolded the day after the specimen was prepared, cured at 20 ° C and 60% RH, and then measured by the four-electrode method (applied voltage 10V, measuring frequency 73.3Hz).
Length change rate: Conforms to JIS A1171. Evaluation of shrinkage: Presence or absence of dripping: The prepared spraying mortar was sprayed.
Cracking: Crack resistance, where cracking occurred was not possible (x), and when cracking did not occur (good).

  From Table 1, the ratio of water binder is high, the amount of unit water is large, and sodium aluminate is added to mortar with high fluidity to reduce the mortar flow value, no dripping, and low electrical resistivity. Mortar can be prepared. Moreover, shrinkage | contraction can be reduced by combined use of an expansion material, a shrinkage reducing agent, and a fiber.

"Experimental example 2"
The compressive strength was measured using 42% water binder ratio, 300kg / m ³ unit water volume, 250mm zero mortar flow value before adding sodium aluminate, and using sodium aluminate as shown in Table 2. Except for this, the same procedure as in Experimental Example 1 was performed. The results are also shown in Table 2.

<Measurement method>
Compressive strength: Measured at a material age of 28 days in accordance with JIS R5201.

  From Table 2, by adding sodium aluminate, it is possible to prepare a mortar for spraying with no sagging, low electrical resistivity, and good strength development.

"Experiment 3"
It was carried out in the same manner as in Experimental Example 1 except that the spraying mortar used in Experiment No. 1-4 was used and the organic-inorganic composite type film curing agent was applied in the coating amount shown in Table 3.
In addition, it carried out similarly about the case where the conventional coating film curing agent is used for the comparison. The results are also shown in Table 3.

<Materials used>
Organic-inorganic composite coating curing agent: Acrylic resin-fluorine mica composite coating curing agent Conventional coating curing agent: EVA coating curing agent, commercial product

  From Table 3, not only the shrinkage of the mortar is further reduced but also the electrical resistance is further reduced by applying the organic-inorganic composite type film curing agent. On the other hand, when a conventional coating film curing agent is applied, such an effect is not seen.

"Experimental example 4"
A 15 × 15 × 53 cm specimen was made of concrete having a unit cement amount of 330 kg / m ³ , a water cement ratio of 60%, an s / a of 52%, and a NaCl addition amount of 12 kg / m ³ .
At this time, a φ13 mm post-rolled steel bar was placed in the center of the specimen in the axial direction. After cutting near the surface of the concrete and embedding a titanium ribbon for the anode, the spraying mortar of Experiment No. 1-4 was filled. Thereafter, an organic-inorganic composite type coating curing agent was applied to the surface so as to be 200 g / m ² . Electrocorrosion protection was performed at a current density of 0.03 A / m ² , and the electrical resistivity of the mortar cured body was measured immediately after the start of the experiment, after 1 month, after 6 months, and after 1 year.
Further, after one year, the presence or absence of rusting of the polished steel bar and the presence or absence of deterioration of the mortar for spraying and the coating film were observed.
In addition, it carried out similarly about the case where an organic type coating material is apply | coated as a comparison with the case where an organic-inorganic composite type coating film curing agent is not used. The results are also shown in Table 4.

<Materials used>
Organic paint: Epoxy, commercially available

From Table 4, using the spray mortar of the present invention, the hardened surface of the mortar cured body in organic it - by applying the inorganic composite coating film curing agent, the electric resistance of the long-term mortar cured body It can be kept small, there is no deterioration of the mortar and the coating film, and a high anticorrosive effect is obtained.
On the other hand, when organic paint is used, rusting of polished steel bars is suppressed, but chlorine gas does not permeate and the mortar hardened body and coating film deteriorate. Resistance increases.

  According to the present invention, it is possible to obtain a mortar for spraying that has no sagging even when the water binder ratio is increased, and that both electric resistance and shrinkage are small. The electrical resistance is kept small and does not prevent the permeation of chlorine gas, etc., and when used for the electrical protection of concrete structures that have been subjected to steel corrosion due to salt damage, etc., enhance the corrosion protection effect of the steel materials inside the concrete structure Can do.

Claims (8)

Uses a mortar composition containing cement-containing binder, fine aggregate, water reducing agent, and water, with a mortar composition with a water binder ratio of 35-55% and unit water volume of 250-400 kg / m ³ It is obtained by adding 0.3 to 5.0 parts of sodium aluminate to 100 parts of cement in a mortar with a 0-stroke mortar flow value of 200 to 320 mm. A spraying mortar with a resistivity of 100 kΩ · cm or less and a length change rate of -800 × 10 ^-6 or less.   A mortar cured body obtained by curing the spraying mortar according to claim 1.   The mortar hardening body formed by apply | coating an organic-inorganic composite type coating film curing agent to the surface of the mortar hardening body of Claim 2.   The mortar hardened body according to claim 3, wherein the organic-inorganic composite-type film curing agent contains a synthetic resin aqueous dispersion, a water-soluble resin, and a swellable clay mineral.   The mortar hardened body according to claim 4, wherein the swellable clay mineral of the organic-inorganic composite type film curing agent is a synthetic fluorine mica. Organic - The amount of the inorganic composite coating film curing agent, mortar cured body according to any one of claims 3 to 5 is 100 to 500 g / m ^2. Using the mortar hardened body according to claim 2, an anode is installed in a concrete structure, and a direct current is allowed to flow from the anode to the steel in the concrete, thereby electrochemically suppressing the corrosion reaction of the steel . A method for preventing corrosion of steel in concrete structures. By using the mortar hardened body according to any one of claims 3 to 6 , an anode is installed in a concrete structure, and a direct current is allowed to flow from the anode to a steel material in the concrete, thereby producing a steel material. A method for preventing corrosion of steel inside a concrete structure, which electrochemically suppresses corrosion reactions .