JP5259360B2 - Plastering mortar with low electrical resistance, a hardened body using the same, and a method for preventing corrosion of steel in a concrete structure using the mortar - Google Patents

Description

  The present invention relates to a plastering mortar used for electrocorrosion protection of a concrete structure subjected to steel corrosion due to salt damage or the like, a cured body using the mortar, and a corrosion prevention method for 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 for protecting the performance of the material, and to integrate with the existing concrete.
Mortar is used as this protective material.

And in order to raise the corrosion-proof effect of steel materials, it is necessary to make small the electrical resistance of the hardening body of the mortar with which the circumference | surroundings of the anode were filled, and to make an electric current flow 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, the 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).

Also, 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 the permeation of salt from (see Patent Document 5).
However, it has not been known what effect the application of the organic-inorganic composite type film curing agent to the surface of a mortar or concrete hardened body with respect to electrical resistance.

  In the case of 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, and mortar near the anode. It is also 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 plastering 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.

The present invention uses a mortar composition containing a cement-containing binder, fine aggregate, water reducing agent, and water, with a water binder ratio of 35 to 55% and a unit water volume of 250 to 400 kg / m. ^A water-soluble acrylic polymer that is one of sodium polyacrylate, polyacrylamide, and a polyacrylamide partial hydrolyzate is added to a mortar having a 0-stroke mortar flow value of 200 to 320 mm, prepared using a mortar formulation of ^3. It is obtained by adding sodium aluminate and kneading. 0.2-100 parts of water-soluble acrylic polymer and 0.01-5 parts of sodium aluminate with respect to 100 parts of cement. Is a plastering mortar having no sagging to be used for troweling, with a shrinkage of −800 × 10 ⁻⁶ or less, with a shrinkage amount of −800 × 10 ⁻⁶ or less, Plastering mortar curing A mortar cured product obtained by applying an organic-inorganic composite-type coating curing agent to the surface of the resin, and the organic-inorganic composite-type coating agent comprising a synthetic resin aqueous dispersion, a water-soluble resin, and a swellable clay mineral. The mortar cured product comprising the swellable clay mineral of the organic-inorganic composite coating agent is the synthetic fluorinated mica, and the amount of the organic-inorganic composite coating agent used is The mortar cured body of 100 to 500 g / m ² , by using the plastered mortar cured body, installing an anode on a concrete structure, and continuously flowing a direct current from the anode to the steel in the concrete A method for preventing corrosion of steel in a concrete structure by controlling the potential of the steel in the concrete and electrochemically inhibiting the corrosion reaction of the steel. The anode is applied to the concrete structure using the cured mortar. Install the anode By controlling the potential of the steel in the concrete by electrochemically directing a direct current from the steel to the steel in the concrete, the corrosion reaction of the steel is controlled electrochemically. A method for producing a plastering mortar, comprising adding a system polymer and sodium aluminate after kneading mortar and kneading.

The present invention provides a plastering mortar 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 plastering mortar anticorrosion method that further reduces shrinkage, keeps electric resistance small for a long period of time, and does not interfere with 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 A plasterer in which water-soluble acrylic polymer and sodium aluminate are added to 320 mm high-fluidity mortar, and the cured product has an electrical resistivity of 100 kΩ · cm or less and a shrinkage of −800 × 10 ⁻⁶ or less. Prepare mortar for use.

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 blast furnace slag, fly ash, or silica with these portland cements, and , 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 may not provide a sufficient anticorrosive effect. Addition of a polymer and sodium aluminate may cause sagging and impair workability as a plastering mortar.

  Here, the plastering mortar is a mortar used for trowel coating, and is required to have no sagging and low viscosity. When sag occurs, the mortar cannot be filled well due to the construction of the wall or ceiling part, etc., and flows, and if the viscosity is large, the detachment of the iron is bad and workability is poor. 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 is too small, and when the mortar is applied with a trowel, the mortar does not stretch and the workability may be deteriorated, and 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. If it is less than 250 kg / m ³ , the amount of free water in the plastered mortar cured body or mortar cured body (hereinafter referred to as the main cured body) decreases, so that there is a possibility that the electrical resistance increases and sufficient anticorrosion effect cannot be obtained. If it exceeds 400 kg / m ³ , sagging may occur even when the water-soluble acrylic polymer and sodium aluminate are added, and the workability as a plastering mortar may be impaired.

  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 increases, 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. Plastering mortar with good workability without adding dripping even if the water binder ratio is high by adding water-soluble acrylic polymer and sodium aluminate to mortar with high fluidity of 200-320mm To prepare.

The water-soluble acrylic polymer used in the present invention is not limited to simply imparting plasticity by thickening mortar having high fluidity.
By mixing water-soluble acrylic polymer with mortar with high fluidity, mortar for plastering with low viscosity, good iron separation, and good workability can be obtained. Does not disturb sex. On the other hand, for example, when a methylcellulose-based compound that is frequently used as a thickener is used, the viscosity of the mortar is increased, the iron separation is poor, and the workability is deteriorated. In addition, a large amount of air is entrained to inhibit strength development.
Examples of the water-soluble acrylic polymer include sodium polyacrylate, polyacrylamide, and polyacrylamide partial hydrolyzate.
When the water-soluble acrylic polymer of the present invention is used, a plastering mortar having a low viscosity and good separation of the iron can be obtained, so that the filling ability into a narrow gap is good. The reason for this is not clear, but it is particularly prominent when used in combination with a naphthalene-based water reducing agent, and it is considered that some interaction with the water reducing agent is exerted.

  The amount of the water-soluble acrylic polymer used is preferably 0.2 to 3 parts, more preferably 0.3 to 1 part, with respect to 100 parts of cement. If it is less than 0.2 parts, sagging may occur, and even if it exceeds 3 parts, the effect of ensuring the workability of the plastering mortar will reach its peak.

The sodium aluminate used in the present invention is used in combination with a water-soluble acrylic polymer to thicken a highly fluid mortar to impart plasticity, and promotes the setting of the mortar to improve workability as a plasterer mortar. Secure. In particular, when the water binder ratio is high, dripping may occur even when a water-soluble acrylic polymer is added alone. However, when sodium aluminate is used in combination, dripping hardly occurs and workability is improved. A good plastering mortar can be obtained.
There are two types of sodium aluminate, one containing water of crystallization and the other with an anhydride, and both can be used. However, the use of an anhydride is preferred in terms of imparting strong plasticity and making the mortar difficult to sag.

  The amount of sodium aluminate used in the present invention is preferably 0.01 to 5 parts, more preferably 0.1 to 1 part, with respect to 100 parts of cement. If it is less than 0.01 part, sagging occurs, and if it is added in excess of 5 parts, the setting is greatly accelerated and the mortar flow value becomes small, and the workability of the plastering mortar may deteriorate.

  In the present invention, the method for adding the water-soluble acrylic polymer and sodium aluminate is not particularly limited, but by adding and kneading the mortar with a predetermined water binder ratio and unit water amount. It is preferable because a plastering mortar with good workability is easily obtained without sagging.

  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 cured product has an electrical resistivity of 100 kΩ · cm or less and a shrinkage of −800 × 10 ⁻⁶ or less.

  The electric resistivity of the cured product is 100 kΩ · cm or less, preferably 50 kΩ · cm or less. When the electrical resistivity exceeds 100 kΩ · cm, it is difficult for current to flow, and there is a possibility that sufficient anticorrosive effect cannot be obtained.

Further, the shrinkage of the cured product is −800 × 10 ⁻⁶ or less, preferably −600 × 10 ⁻⁶ or less. If the shrinkage amount exceeds −800 × 10 ⁻⁶ , cracks are likely to occur, current becomes difficult to flow, and a sufficient anticorrosion effect may not be obtained.

In the present invention, in order to reduce the shrinkage amount of the cured product, that is, to reduce the shrinkage amount to −800 × 10 ⁻⁶ or less, it is preferable to use an expansion material, a shrinkage reducing agent, and fibers 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 brain (hereinafter referred to as “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 the organic-inorganic composite type film curing agent to the surface of the cured body not only can further reduce the shrinkage and suppress cracking, but also can provide long-term electrical resistance of the 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 plastering of the plastering mortar 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.
By applying the film curing agent of the present invention to the plastering mortar cured body of the present invention, not only can the length change rate be further reduced to suppress cracking, but also the electrical resistance of the mortar cured body over the long term. Keeping it small can increase the anticorrosion 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.

Experimental example 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. A mortar for plastering with a mortar flow value shown in Table 1 was prepared using a mortar composition of water binder ratio and unit water amount shown in Table 1 with 1005 parts by volume of fiber in 100 parts by volume of the mortar composition. .
Thereafter, 0.5 part of a water-soluble acrylic polymer and 0.2 part of sodium aluminate were added to 100 parts of cement, and a plastering mortar was mixed. The mortar flow value was measured before and after the addition of the water-soluble acrylic polymer and sodium aluminate, and the presence or absence of dripping and the workability after the addition were 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. Plastering mortar was placed on the existing concrete board so that it was 30cm long, 30cm wide and 3cm 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 2.62 g / cm ³
Water-soluble acrylic polymer: polyacrylamide partial hydrolyzate, commercial product sodium aluminate: anhydrous salt, powder, commercial product

<Measurement method>
Mortar flow value: Measure the prepared mortar according to JIS R 5201. However, before the addition of the water-soluble acrylic polymer and sodium aluminate, the mortar flow value is 0 strokes, and the mortar flow value is 15 strokes after the addition (the value in the stationary state without tapping the flow table, and after 15 taps) value).
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: Compliant with East Japan, Central Japan, West Japan Expressway Co., Ltd. test method (JHS 416-2004) "Cross-section restoration material quality standard test method". Evaluation of shrinkage: Presence / absence of sagging: The prepared plaster mortar was applied with a trowel, and no sagging occurred (x), and no sagging occurred (good).
Workability: Impossible (X) when it is difficult to handle with a trowel, such as strong viscosity or too soft mortar, and acceptable (◯) when the viscosity is small and easy to handle.
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 by adding water-soluble acrylic polymer and sodium aluminate to mortar with high fluidity, the mortar flow value is reduced, there is no sag, and viscosity A plastering mortar can be prepared that has a small workability, good workability and low electrical resistivity. Moreover, shrinkage | contraction can be reduced by combined use of an expansion material, a shrinkage reducing agent, and a fiber.

Experimental example 2
The water-soluble acrylic polymer shown in Table 2 has a water-binding material ratio of 42%, unit water volume of 300 kg / m ³ , and a 0-stroke mortar flow value before adding water-soluble acrylic polymer and sodium aluminate to 250 mm. And sodium aluminate, and the same procedure as in Experimental Example 1 was conducted except that the compressive strength was measured.
For comparison, the same procedure was performed when methylcellulose was added. The results are also shown in Table 2.

<Materials used>
Methylcellulose: Commercial product

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

  From Table 2, by adding a water-soluble acrylic polymer and sodium aluminate, it is possible to prepare a plastering mortar that has good workability, low electrical resistivity, and does not impair strength development. Since the viscosity is small and the trowel is good, the filling property is also good. On the other hand, when methylcellulose is added, the viscosity is strong and the separation of the iron is bad, and the strength development is inhibited.

Experimental example 3
The same procedure as in Experimental Example 1 was conducted except that the plastering mortar used in Experiment No. 1-4 was used and the organic-inorganic composite type coating 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 the anode titanium ribbon, it was filled with mortar for plastering in Experiment No.1-4. 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.
One year later, the polished steel bars were observed for rusting and for plastering mortars and coatings for deterioration.
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, by using the plastering mortar of the present invention and applying an organic-inorganic composite film curing agent on its surface, the electrical resistance of the cured mortar can be kept small over the long term. There is no deterioration of the 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 plastering mortar that does not sag even when the water binder ratio is increased, and that both electrical resistance and shrinkage are small. It keeps the resistance low and does not prevent the permeation of chlorine gas, etc., and when used for the electrical protection of concrete structures that have undergone steel corrosion due to salt damage, etc., it can enhance the corrosion protection effect of the steel materials inside the concrete structure. it can.

Claims (9)

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 A water-soluble acrylic polymer and sodium aluminate, which is either sodium polyacrylate, polyacrylamide, or polyacrylamide partial hydrolyzate, are added to a mortar with a 0-stroke mortar flow value of 200 to 320 mm prepared using It is obtained by adding and kneading, and 0.2 to 3 parts of water-soluble acrylic polymer and 0.01 to 5 parts of sodium aluminate with respect to 100 parts of cement. The electrical resistivity of the cured product is 100 kΩ · cm. Below, a mortar for plasterers with a shrinkage of -800 x 10 ^-6 or less and no sagging used for ironing. A plastering mortar cured product obtained by curing the plastering 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 for plasterers of Claim 2. The mortar hardened body according to claim 3, wherein the organic-inorganic composite coating agent contains an aqueous synthetic resin 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 coating agent is a synthetic fluorine mica. Organic - The amount of the inorganic composite coating agent, mortar cured body according to any one of claims 3 to 5 is 100 to 500 g / m ^2. Using the plastered mortar hardened body according to claim 2, installing an anode in a concrete structure, and controlling a potential of the steel material in the concrete by continuously passing a direct current from the anode to the steel material in the concrete, An anticorrosion method for steel inside a concrete structure, which electrochemically suppresses the corrosion reaction of the steel. By installing an anode on a concrete structure using the mortar hardened body according to any one of claims 3 to 6, and continuously flowing a direct current from the anode to a steel material in the concrete, An anticorrosion method for steel inside a concrete structure by controlling the electric potential of the steel inside and electrochemically inhibiting the corrosion reaction of the steel. The method for producing a plastering mortar according to claim 1, wherein the water-soluble acrylic polymer and sodium aluminate are mixed and then mixed.