JP2020105772A - Repair method of salt-shielding mortar - Google Patents

Abstract

To provide a repair method of salt-shielding mortar capable of exhibiting little initial length change in association with its curing and forming a mortar hardened body with salt-shielding upon being integrated with a concrete structural body.SOLUTION: A repairing method of salt-shielding mortar comprises: a construction step of constructing mortar on a concrete structural body; and a forming step of forming a mortar cured body through curing the mortar, wherein the mortar is a mixture of an alumina cement composition of salt-shielding mortar and water. The alumina cement composition of the salt-shielding mortar includes the alumina cement and gypsum hemihydrate, the alumina cement including 55 mass% to 75 mass% of CA, 5 mass% to 8 mass% of C12A7, 10 mass% to 28 mass% of C4AF, and 2 mass% to 6 mass% of C2AS. A Blaine specific surface area of the alumina cement is from 2,000 cm2/g to 4,000 cm2/g, and a Blaine specific surface area of the gypsum hemihydrate is from 3,000 cm2/g to 6,000 cm2/g. A content of the gypsum hemihydrate is from 10 pts.mass to 24 pts.mass relative to 100 pts.mass of the alumina cement.SELECTED DRAWING: None

Description

The present disclosure relates to a method for repairing salt-barrier mortar.

In order to use the concrete structure for a long period of time, it is repaired with restoration materials. In particular, it is said that it is effective to adsorb or fix chloride ions from the viewpoint of suppressing deterioration due to permeation of salt and the like.

It is known that, for example, a cement composition containing lithium nitrite is effective for adsorbing chloride ions. However, since lithium nitrite is toxic, there is a problem that it is expensive in addition to consideration for the surrounding environment.

In Patent Document 1, mainly composed of Portland cement and fine aggregate, including a salt adsorbent and a quick-setting material, the quick-setting material contains anhydrous gypsum powder and calcium aluminate composition powder, and the anhydrous gypsum powder has a Blaine specific surface area. A cross-section restoration material for repairing salt damage, which is characterized by being 8000 cm ² /g or more, has been proposed.

JP, 2013-227210, A

Alumina cement containing calcium aluminate etc. has excellent chemical stability. However, in the case of alumina cement, a cured product may be cracked as the length changes due to curing. In addition, in the case of high temperature curing, voids may occur due to the transition of the phases constituting the cured body. When a hardened body formed by using the above-mentioned alumina cement is used for repairing a concrete structure, even if the material has excellent salt barrier properties, due to voids and cracks in the hardened body, the interior of the concrete structure It is feared that the generation of rust in the above steel materials cannot be sufficiently suppressed.

The present disclosure discloses a method of repairing salt-shielding mortar, which has a small amount of change in initial length due to curing and can form a mortar cured body having excellent salt-shielding properties when integrated with a concrete structure. The purpose is to provide.

One aspect of the present disclosure is a method for repairing salt-blocking mortar, comprising a construction step of applying mortar to a concrete structure, and a formation step of forming a mortar hardened body by hardening the mortar, wherein The mortar is a mixture of an alumina cement composition for salt-barrier mortar and water, the alumina cement composition for salt-barrier mortar contains alumina cement and hemihydrate gypsum, and the alumina cement has a CA of 55 mass. % To 75% by mass, C ₁₂ A ₇ at 5% to 8% by mass, C ₄ AF at 10% to 28% by mass, and C ₂ AS at 2% to 6% by mass, and the above-mentioned alumina cement brane. specific surface ^area, is 2000cm ² / g~4000cm 2 / g, the Blaine specific surface area of the hemihydrate gypsum ^is a 3000cm ² / g~6000cm 2 / g, the content of the hemihydrate gypsum, the alumina cement A method for repairing salt-blocking mortar, which is 10 to 24 parts by mass with respect to 100 parts by mass, is provided.

The method for repairing the salt-barrier mortar uses a specific alumina salt cement composition for salt-barrier mortar, so the amount of initial length change accompanying curing is small, and is excellent when integrated with a concrete structure. It is possible to form a cured mortar having salt barrier properties. Therefore, it is possible to obtain a concrete structure having excellent rust preventive properties after repair.

The alumina cement composition for salt-barrier mortar may further contain at least one selected from the group consisting of calcium carbonate and silica fume. The alumina cement composition for mortar further contains at least one selected from the group consisting of calcium carbonate and silica fume, thereby improving the compressive strength of a mortar hardened product formed using the alumina cement composition for mortar. Can be made

The content of the calcium carbonate may be 15 parts by mass to 35 parts by mass with respect to 100 parts by mass of the alumina cement. When the content of calcium carbonate is within the above range, it is possible to improve the compressive strength of the hardened mortar formed using the alumina cement composition for mortar.

The content of the silica fume may be 3 parts by mass to 12 parts by mass with respect to 100 parts by mass of the alumina cement. When the content of silica fume is within the above range, it is possible to improve the compressive strength of the mortar cured product formed using the above-mentioned alumina cement composition for mortar.

According to the present disclosure, the amount of initial length change accompanying curing is small, and it is possible to form a mortar cured body having excellent salt-shielding properties when integrated with a concrete structure. A repair method can be provided.

FIG. 1 is a schematic view showing an example of a mortar construction method by a spraying method. FIG. 2 is a schematic top view of the length change amount measuring device. FIG. 3 is a schematic cross-sectional view taken along the line II-II of FIG.

Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are examples for describing the present disclosure, and are not intended to limit the present disclosure to the following contents.

In the present specification, the "initial" means a period from the placing of the mortar to the lapse of 24 hours.

One embodiment of a method of repairing salt-barrier mortar includes a step of removing a part of a concrete structure (hereinafter, also referred to as a removal step) and a step of applying mortar to the concrete structure (hereinafter, also referred to as a construction step). And a step of forming a cured mortar by curing the mortar (hereinafter, also referred to as a forming step). The method of repairing salt-barrier mortar according to the present embodiment can also be regarded as a method of repairing a concrete structure.

The removing step is a step of removing the deteriorated portion of the concrete structure in advance before the mortar construction. The deteriorated portion of the concrete structure can be identified by, for example, observing the appearance and investigating the tapping method. In the removal step, the concrete structure may be broadly removed so as to include the sound part around the deteriorated part so that the deteriorated part is completely removed. As a means for removing the deteriorated portion of the concrete structure, for example, an electric cutter, a hammer, a hand breaker, a shot blast, a water jet, or the like can be used. Since the salt-shielding mortar repairing method has a removing step, a more sufficient repairing effect can be obtained. The removing step may be omitted if necessary.

The concrete structure from which the deteriorated portion has been removed has a concave portion corresponding to the removed deteriorated portion. The steel material and the like in the concrete structure may be exposed depending on the width and depth of the recess. In such a case, the method may further include the step of applying a rust preventive agent to the steel material or the like. When the steel or the like is corroded, it is preferable to remove the rust in advance by a method such as a wire brush or shot blasting and then apply the rust preventive agent. As the rust preventive agent, for example, a polymer cement rust preventive agent or the like can be used. The polymer cement-based rust preventive agent includes a cement composition, a synthetic resin, a rust preventive component, water and the like.

Before the construction step, a step of providing a primer layer on the concrete structure (for example, a recess formed in the concrete structure) may be further included. The primer layer may include, for example, a water absorption adjusting agent. As the water absorption regulator, for example, a synthetic resin diluted with a solvent such as water can be used. The primer layer can be formed, for example, by applying the water absorption regulator on the surface of the concrete structure to reduce the amount of solvent. A brush, a resin gun, or the like can be used to apply the water absorption modifier.

The construction step is a step of filling a predetermined portion of the concrete structure (for example, a recess from which the deteriorated portion has been removed) with mortar. The above mortar is a mixture of a specific alumina cement composition for mortar described below and water, and may be kneaded after mixing. The kneading of the alumina cement composition for mortar and water may be performed using a mixer such as a handle mixer and a mortar mixer.

The method of filling a predetermined portion of the concrete structure with mortar may be, for example, a plastering method or a spraying method. When the area of the predetermined portion of the concrete structure is less than 10 m ^2, it is preferable to perform mortar construction by the plastering method. The area of a predetermined portion of the concrete structure is 10 m ² or more ^(e.g., 10m ^{2 ~100m} 2, etc.) in the case of, it is preferable to carry out construction of the mortar by spraying method.

In the plastering method, a plasterer puts an appropriate amount of mortar on a mortarboard, and uses a metal trowel or the like to apply the mortar to a predetermined portion of a concrete structure by applying the mortar in several portions. In the first application, for example, application is performed with a thickness of about 5 mm, and in the second and subsequent operations, application is repeated with a thickness of 10 mm or less. The coating thickness for one day is preferably about 30 mm.

In the spraying method, the mortar is sprayed onto a predetermined portion of the concrete structure by using an apparatus used in the spraying method to fill the mortar. FIG. 1 is a schematic diagram showing a construction method by a spraying method. As shown in FIG. 1, in the spraying method, a predetermined portion (not shown) of the concrete structure 50 is sprayed with the mortar 30 to fill the mortar 30. The apparatus used for the spraying method shown in FIG. 1 includes a mixer 41, a mortar pump 42 with a hopper, an air source 43, a pressure-resistant hose 44, and a spray gun 45. As a device used for the spraying method, a hopper and a mortar pump may be separated.

In the spraying method, it is preferable to spray the mortar in several steps. In the first construction, for example, mortar is sprayed to a thickness of about 5 mm, and in the second and subsequent constructions, mortar is sprayed to a thickness of 30 mm or less. Mortar is sprayed so that the final construction is about 15 mm thick. After that, the surface of the mortar portion may be finished with a trowel so that the surface of the mortar portion is flattened so that the mortar filled in a predetermined portion of the concrete structure and the concrete structure can be more sufficiently bonded.

The forming step is a step of hardening the mortar filled in a predetermined portion of the concrete structure in the construction step to form a hardened mortar body. The filled mortar forms a hardened mortar body, for example, by drying.

The alumina cement composition for salt-barrier mortar used in the present embodiment will be described. The alumina cement composition for salt-blocking mortar contains alumina cement and hemihydrate gypsum. The alumina cement, CA 55 wt% to 75 _{wt%, C} 12 _{A 7} 5 wt% to 8 _{wt%, C} 4 AF 10 wt% to 28 wt%, and _C 2 AS 2 mass% to 6 Contains mass%. Blaine specific surface area of the alumina cement ^is 2000cm ² / g~4000cm 2 / g. Blaine specific surface area of the hemihydrate gypsum ^is 3000cm ² / g~6000cm 2 / g. The content of the hemihydrate gypsum is 10 to 24 parts by mass with respect to 100 parts by mass of the alumina cement.

Mortar, which is a mixture of the above-described salt-shielding alumina cement composition for mortar and water, can be used as a repair material for concrete structures, for example. The concrete structure may include a concrete part and a metal part. The shape of the metal part may be, for example, a rod shape. The metal part may include a metal such as iron and steel, for example. Since the cured product of mortar (hereinafter, also referred to as a cured mortar) is also excellent in salt-shielding property, it is possible to suppress the generation of rust in the steel material inside the concrete structure.

The term "salt barrier" as used herein means that the apparent diffusion coefficient of chloride ions is low. The low apparent diffusion coefficient of chloride ions means, for example, 0.05 cm ² /year or less. Alumina cement composition for salt-blocking mortar means that when a mortar cured product is formed using the alumina cement composition for mortar, an apparent diffusion coefficient of chloride ion of the salt-blocking mortar cured product is low. Means

The alumina cement contains calcium aluminate as a main component. Calcium aluminate, for example, CaO · _Al 2 _{O 3} (hereinafter also referred to as _{CA), 12CaO · 7Al 2 O} 3 ( _hereinafter also referred to as _{C 12 A 7), CaO ·} 2A l2 O 3 ( hereinafter, CA ₂ also referred _{to), 4CaO · Al 2 O 3} · Fe 2 O 3 ( _hereinafter also referred to as _C 4 AF), and _{2CaO · Al 2 O 3 · SiO} 2 ( _hereinafter, also referred to as _C 2 aS), and the like. In the present specification, the “main component” means that the content of the component is 50% by mass or more, for example.

The mineral composition of the above-mentioned alumina cement is measured by analyzing the powder X-ray diffraction data of the alumina cement by the profile fitting method. As the profile fitting method, a Rietveld analysis method or a WPF (Whole pattern fitting) analysis method is used (see Reference Document 1 below).

Reference 1: Practice of powder X-ray diffraction-Introduction to Rietveld method, Japan Society for Analytical Chemistry, X-ray analysis research conference [edit]

The mineral composition of the alumina cement is, for example, 55 mass% to 75 mass% of CA, 5 mass% to 8 mass% of C ₁₂ A ₇ , 10 mass% to 28 mass% of C ₄ AF, and ₂ masses of C ₂ AS. The composition may contain from 6% by mass to 6% by mass. The alumina cement is preferably 58% by mass to 72% by mass of CA, 5.6% by mass to 7.8% by mass of C ₁₂ A ₇ , 13% by mass to 25% by mass of C ₄ AF, and C ₂ AS. 2.5 mass% to 5.5 mass %, more preferably 62 mass% to 68 mass% CA, 5.4 mass% to 7.6 mass% C ₁₂ A ₇ , and 16 C ₄ AF. wt% to 22 wt%, and a _C 2 AS 3.0 wt% to 5.0 wt%. When the mineral composition of the alumina cement is within the above range, the salt-barrier property of the formed mortar cured product can be further improved. Further, when the mineral composition of the alumina cement is within the above range, it is possible to further reduce the initial amount of change in length associated with the hardening of the alumina cement composition for mortar.

Blaine specific surface area of the alumina cement may be, for ^example, 2000cm ² / g~4000cm 2 / g. Blaine specific surface area of the alumina cement is preferably a 2300cm ² / g~3500cm ² / g, more preferably 2500cm ² / g~3300cm ² / g. When the Blaine specific surface area of the alumina cement is within the above range, a dense mortar cured product can be formed. The Blaine specific surface area of the alumina cement means a value measured according to JIS R 2521:1995 “Physical test method of alumina cement for fire resistance”.

The hemihydrate gypsum may contain at least one selected from the group consisting of α-type hemihydrate gypsum and β-type hemihydrate gypsum.

Blaine specific surface area of the hemihydrate gypsum, for ^example, may be 3000cm ² / g~6000cm 2 / g. Blaine specific surface area of the hemihydrate gypsum is preferably 3700cm ² / g~5500cm ² / g, more preferably 4100cm ² / g~5350cm ² / g. When the brane specific surface area of the hemihydrate gypsum is within the above range, it is possible to make the initial length change amount due to the curing of the alumina cement composition for salt-barrier mortar smaller. The Blaine specific surface area of hemihydrate gypsum means a value measured according to JIS R 5201:2015 “Physical test method for cement”.

The content of hemihydrate gypsum is 10 to 24 parts by mass with respect to 100 parts by mass of the alumina cement. The content of hemihydrate gypsum is preferably 12 parts by mass to 20 parts by mass, and more preferably 13 parts by mass to 18 parts by mass with respect to 100 parts by mass of the alumina cement. When the content of the hemihydrate gypsum is within the above range, the initial amount of change in length due to the curing of the alumina cement composition for salt-barrier mortar can be made smaller.

The alumina cement composition for salt-blocking mortar may contain other components in addition to alumina cement and hemihydrate gypsum. Examples of other components include admixtures, fine aggregates, water reducing agents, setting retarders, antifoaming agents, and resins. The alumina cement composition for salt-barrier mortar preferably contains an admixture.

Examples of the admixture include calcium carbonate and silica fume. The alumina cement composition for salt-blocking mortar may further include at least one selected from the group consisting of calcium carbonate and silica fume.

A commercial item can be used for calcium carbonate. Calcium carbonate may be supplied using, for example, a material containing calcium carbonate as a main component. Examples of the material containing calcium carbonate as a main component include limestone powder obtained by crushing limestone and concrete powder obtained by crushing waste concrete.

Blaine specific surface area of calcium carbonate is preferably 2000cm a ² / ^{g~6000cm 2} / g, more preferably 2400cm ² / g~5400cm ² / g and may be, more preferably 2700cm ² / g~5100cm ² / It is g. When the Blaine specific surface area of calcium carbonate is within the above range, the compression strength of the formed mortar cured product can be further improved. When the Blaine specific surface area of calcium carbonate is within the above range, a dense mortar hardened product can be formed, and salt-blocking properties can be further improved. The Blaine specific surface area of calcium carbonate means a value measured according to JIS R 5201:2015 “Physical test method for cement”.

The content of calcium carbonate is preferably 15 parts by mass to 35 parts by mass, more preferably 20 parts by mass to 29 parts by mass, and further preferably 22 parts by mass to 27 parts by mass with respect to 100 parts by mass of the alumina cement. Parts by mass, and even more preferably 24 parts by mass to 25 parts by mass. When the content of calcium carbonate is within the above range, the compressive strength of the formed mortar cured product can be further improved. When the content of calcium carbonate is within the above range, a dense mortar hardened product can be formed, and the salt barrier property can be further improved.

The silica fume may be, for example, a silica fume specified in JIS A 6207:2016 “Silica fume for concrete”. Since the alumina cement composition for salt-barrier mortar contains silica fume, it is possible to form a dense mortar hardened body, and it is possible to further improve the compression strength of the formed mortar hardened body and the salt-barrier property. it can.

BET specific surface area of silica fume is preferably ^{10m 2} / ^g~28m 2 / g, more preferably ^{14m 2} / ^g~26m 2 / g, even more preferably at ^{16m 2} / ^g~24m 2 / g .. When the BET specific surface area of the silica fume is within the above range, a dense mortar cured product can be formed, and the compression strength and salt-shielding property of the formed mortar cured product can be further improved. The BET specific surface area of silica fume means a value measured by the BET multipoint method. BELSORP-mini II (product name) manufactured by Nippon Bell Co., Ltd. can be used for the measurement.

The content of silica fume is preferably 3 parts by mass to 12 parts by mass, more preferably 5 parts by mass to 10 parts by mass, and further preferably 6 parts by mass to 9 parts by mass with respect to 100 parts by mass of the alumina cement. Parts, and even more preferably 6 parts by mass to 8 parts by mass. When the content of silica fume is within the above range, a dense mortar cured product can be formed, and the compression strength and salt-shielding property of the formed mortar cured product can be further improved.

Examples of the fine aggregate include sands such as silica sand, river sand, land sand, sea sand, and crushed sand. The maximum particle size of the fine aggregate is preferably 1700 μm or less, more preferably 1500 μm or less. The particle size of the fine aggregate means a value measured by using several sieves having different nominal sizes specified in JIS Z 8801-1:2006 "Test sieve-Part 1: Metal mesh sieve". To do.

The proportion of the fine aggregate having a particle diameter of 1200 μm or more is preferably 20% by mass or less, more preferably 0.05% by mass to 20% by mass, and further preferably 0% with respect to the total amount of the fine aggregate. It is 0.01 mass% to 15 mass% or less, still more preferably 0.05 mass% to 10 mass%, and even more preferably 0.1 mass% to 3.0 mass%. When the ratio of the fine aggregate having a particle diameter of 1200 μm or more is within the above range, the uniformity of the formed mortar cured product can be further improved and the salt-barrier property can be further improved. In the present specification, the “proportion of fine aggregate having a particle size of 1200 μm or more” means the mass% of particles remaining on the screen when a screen having a mesh size of 1200 μm is used.

The content of fine aggregate is preferably 90 parts by mass to 200 parts by mass, more preferably 110 parts by mass to 180 parts by mass, and further preferably 120 parts by mass to 100 parts by mass of the alumina cement. 170 parts by mass. When the content of the fine aggregate is within the above range, it is possible to further improve the compressive strength of the formed mortar cured body.

Examples of the water reducing agent include lignin-based, naphthalene sulfonic acid-based, amino sulfonic acid-based, polycarboxylic acid-based water reducing agents, high-performance water reducing agents, and high-performance AE water reducing agents. When the water reducing agent contains at least one selected from the group consisting of polycarboxylic acid type water reducing agents, high-performance water reducing agents, and high-performance AE water reducing agents, the fluidity of the mortar can be improved. The content of the water reducing agent can be appropriately adjusted within a range that does not impair the effects of the invention.

Examples of the setting retarder include organic acids such as oxycarboxylic acids, sugars such as glucose, maltose and dextrin, sodium bicarbonate, and sodium phosphate. Examples of oxycarboxylic acids include oxycarboxylic acids and salts thereof. As the oxycarboxylic acid, for example, citric acid, gluconic acid, tartaric acid, glycolic acid, lactic acid, hydroacrylic acid, α-oxybutyric acid, glyceric acid, tartronic acid, and aliphatic oxy acids such as malic acid, and salicylic acid, Examples thereof include aromatic oxyacids such as m-oxybenzoic acid, p-oxybenzoic acid, gallic acid, mandelic acid, and tropic acid.

Examples of salts of oxycarboxylic acids include alkali metal salts and alkaline earth metal salts. Examples of the alkali metal salt include sodium salt and potassium salt. Examples of the alkaline earth metal salt include calcium salt, barium salt, magnesium salt and the like. The salt of the above-mentioned oxycarboxylic acid is preferably a sodium salt, more preferably sodium tartrate. As the salt of oxycarboxylic acid, it is preferable to use sodium tartrate and sodium bicarbonate in combination.

The content of the setting retarder is preferably 0.01 parts by mass to 1.5 parts by mass, more preferably 0.05 parts by mass to 1.2 parts by mass with respect to 100 parts by mass of the above-mentioned alumina cement. , And more preferably 0.1 part by mass to 1.0 part by mass. When the content of the setting retarder is within the above range, the workable time (so-called pot life) after preparing the mortar can be extended without inhibiting the curing.

Examples of the antifoaming agent include silicone-based, alcohol-based, and polyether-based synthetic substances, and plant-derived natural substances. The content of the defoaming agent can be appropriately adjusted within a range that does not impair the effects of the invention.

The resin may be, for example, powder, emulsion or fibers. When the above-mentioned salt-shielding alumina cement composition for mortar contains a resin in the form of powder or emulsion, the salt-shielding property of the formed mortar cured product can be further improved. When the salt-shielding alumina cement composition for mortar contains a resin as a fiber, it is possible to further suppress the occurrence of cracks in the formed mortar cured product. The emulsion means a resin emulsified and dispersed in water or a water-containing solvent.

The glass transition temperature (Tg) of the resin may be, for example, 0° C. or higher, 5° C. or higher, and 10° C. or higher. Since the glass transition temperature of the resin is within the above range, the mortar exhibits excellent adhesiveness to the surface of the concrete structure even when repairing the concrete structure in a wet state. obtain.

The glass transition temperature of a resin means a value that can be measured using a differential scanning calorimeter. More specifically, the glass transition temperature of the resin can be measured by the following method. First, the resin to be measured was heated for 10 minutes from room temperature to 0.99 ° C. (1 ^st heating), held to erase the thermal history of the resin for 10 minutes at 0.99 ° C.. Then, lowering the temperature to -100 ° C. ^{(quenching, 1 st} cooling), temperature was raised at a heating rate 15 ° C. / min up again 0.99 ° C. ^{(2 nd} heating) were Tg first measurement. Cooling rate from 0.99 ° C. to a temperature below the measured Tg of at ^{1 st} heating: the temperature was lowered at 15 ° C. / min ^{(2 nd} cooling) were Tg second measurement. The value of Tg obtained by the second Tg measurement is taken as the glass transition temperature of the resin to be measured. When the resin to be measured is in the form of an emulsion, an appropriate amount of the emulsion is dropped on a glass plate to reduce the content of water or a water-containing solvent to form a coating film, and the coating film is measured. Can be

When the composition of the resin to be measured is known, the estimated temperature range of the glass transition temperature T obtained according to the following calculation formula (1) may be used to determine the DSC measurement temperature range in advance. .. That is, after holding at 150° C. for 10 minutes, the temperature is lowered to a temperature lower by 50° C. than the estimated value T of the glass transition temperature of the resin to be measured, and otherwise the Tg of the resin to be measured is the same as above. May be measured.

For the glass transition temperature (Tg) of the resin, the estimated species T is calculated from the following formula (1) using the Tg of the homopolymer of the monomer, by specifying the monomer species and the composition ratio that give the structural unit that constitutes the resin. can do. Since the estimated value T is calculated in degrees Fahrenheit (unit: K), it can be converted into degrees Celsius (unit: °C) for use. The following formula (1) is a formula assuming a resin which is a copolymer of n monomer species. As the Tg of the homopolymer, data described in, for example, Polymer Handbook 4th edition can be used. For example, Tg of polystyrene is 100°C, Tg of poly(n-butyl acrylate) is -52°C, and Tg of poly(n-ethylhexyl acrylate) is -70°C.

1/T=(C _a /Tg _a )+(C _b /Tg _b )+...+(C _n /Tg _n )... (1)
In the above formula (1), T represents an estimated value (degree F, unit: K) of the glass transition temperature of the resin to be measured. In the above formula (1), C _a represents the weight fraction of the monomer A, C _b represents the weight fraction of the monomer B, and C _n represents the weight fraction of the monomer N. In the above formula (1), a homopolymer glass transition temperature (degrees Fahrenheit, unit: K) of Tg _a monomer A indicates, Tg _b are the glass transition temperature (Fahrenheit degrees of the homopolymer of monomer B, unit: K) indicates, Tg _n is the glass transition temperature (Fahrenheit degrees of the homopolymer of the monomer n, unit: K) shows a. Note that (C _a +C _b +...+C _n )=1.

Examples of the powder (hereinafter, also referred to as resin powder) include a styrene-acrylic copolymer, an acrylic polymer, a vinyl acetate-veova-acrylic copolymer, an ethylene-vinyl acetate copolymer, and the like. The content of the resin powder is preferably 1 part by mass to 10 parts by mass, more preferably 2 parts by mass to 8 parts by mass, and further preferably 4 parts by mass to 6 parts by mass with respect to 100 parts by mass of the alumina cement. Parts by mass. When the content of the resin powder is within the above range, it is possible to further improve the salt barrier property of the formed mortar cured body.

The resin constituting the resin emulsion may be a homopolymer or a copolymer. The resin constituting the resin emulsion includes, for example, (meth)acrylic acid, (meth)acrylic acid derivatives such as (meth)acrylic acid ester, olefins such as vinyl acetate, ethylene and butadiene, and polymerizable components such as styrene. It may be a polymer of the polymerizable composition containing. The polymerizable component may include at least one selected from the group consisting of (meth)acrylic acid, a (meth)acrylic acid derivative, and styrene from the viewpoint of further improving the salt-barrier property of the obtained mortar cured product. Examples of the (meth)acrylic acid derivative include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

The content of the resin emulsion is preferably 1 part by mass to 10 parts by mass, more preferably 2 parts by mass to 7 parts by mass, and further preferably 100 parts by mass of the alumina cement in terms of solid content. The amount is 2.5 parts by mass to 6 parts by mass, and more preferably 3 parts by mass to 5 parts by mass. By setting the content of the resin emulsion within the above range, the adhesiveness to the concrete structure and the salt-barrier property can be further improved. The solid content of the resin emulsion means the solid content remaining after evaporation of water or the water-containing solvent in the resin emulsion.

The fiber (hereinafter, also referred to as resin fiber) may be a fiber made of resin. Examples of the resin that constitutes the resin fiber include polyolefin such as polyethylene and polypropylene, ethylene-vinyl acetate copolymer (EVA), polyester, polyamide, polyvinyl alcohol, vinylon, and polyvinyl chloride.

The fiber length of the resin fiber is preferably 0.5 mm to 15.0 mm, more preferably 1.0 mm to 12.0 mm, further preferably 2.0 mm to 8.0 mm, and further preferably 2. It is 5 mm to 7.0 mm. By setting the fiber length of the resin fiber within the above range, it is possible to improve the handleability when mixed with other components such as alumina cement, and reduce the salt barrier property and durability of the obtained mortar cured product. Can be suppressed. Further, by setting the fiber length of the resin fiber within the above range, it is possible to further suppress the occurrence of cracks in the cured mortar. In addition, the fiber length of the resin fiber in this specification means the value measured by optical microscope observation.

The content of the resin fiber is preferably 0.01 parts by mass to 3 parts by mass, more preferably 0.03 parts by mass to 1 part by mass, and further preferably 0 with respect to 100 parts by mass of the alumina cement. 0.04 to 0.3 parts by mass, and even more preferably 0.05 to 0.15 parts by mass. By setting the content of the resin fiber within the above range, it is possible to further suppress the occurrence of cracks in the cured mortar while suppressing the deterioration of the salt barrier property and durability of the obtained cured mortar.

The above-mentioned mortar can be formed by mixing and kneading the above-mentioned salt-shielding alumina cement composition for mortar and water.

The amount of water added to the alumina cement composition for salt-blocking mortar is preferably 4 parts by mass to 25 parts by mass, and more preferably 100 parts by mass of the alumina cement composition for salt-blocking mortar. It is 5 parts by mass to 20 parts by mass, more preferably 8 parts by mass to 16 parts by mass, and even more preferably 10 parts by mass to 14 parts by mass. When the resin emulsion is contained, it is preferable that the water content in the resin emulsion is included in the water content.

Since the above-mentioned mortar uses the above-mentioned salt-shielding alumina cement composition for mortar, the initial amount of change in length due to hardening is small. The amount of initial length change associated with the hardening of the mortar can be, for example, -200 μm/m or more, -180 μm/m or more, -150 μm/m or more, -120 μm/m or more, or 0 μm/m or more. The amount of initial length change associated with the hardening of the mortar can be, for example, 1000 μm/m or less, 800 μm/m or less, 500 μm/m or less, 300 μm/m or less, or 200 μm/m or less. “Greater than or equal to” in the numerical value in the negative range means approaching zero. Here, when the value of the amount of change in length of the cured mortar is negative, it means that the cured mortar has shrunk. The “length change amount” in the present specification means a value determined by a method described in Examples described later.

Since the above-mentioned hardened mortar is formed by using the above-described salt-blocking alumina cement composition for mortar, it has excellent salt-blocking properties. The apparent diffusion coefficient of chloride ions mortar cured body, for example, 0.05 cm ² / year or less, 0.04 cm ² / year or less, 0.03 cm ² / year or less, 0.02 cm ² / year or less, or 0 It can be less than or equal to 0.01 cm ² /year.

The apparent diffusion coefficient of chloride ion of the cured mortar is based on the test method described in JSCE-G571-2013 "Test method for effective diffusion coefficient of chloride ion in concrete by electrophoresis (plan)", It means the value obtained by using "Appendix (reference) Apparent diffusion coefficient calculation method using effective diffusion coefficient by electrophoresis test".

Since the above-mentioned mortar hardened product is formed by using the above-mentioned salt-shielding alumina cement composition for mortar, it has excellent compressive strength. The curing strength: 20° C., age: 28 days, the compressive strength of the cured mortar can be, for example, 40 N/mm ² or more, 45 N/mm ² or more, or 50 N/mm ² or more. The curing strength: 50° C., age: 28 days, the compressive strength of the cured mortar can be, for example, 40 N/mm ² or more, 50 N/mm ² or more, or 60 N/mm ² or more.

The compressive strength of the cured mortar means a value measured according to the test method described in JIS R 5201:2015 “Physical test method for cement”.

Since the above-mentioned hardened mortar is formed by using the above-mentioned salt-shielding alumina cement composition for mortar, it is possible to suppress the generation of rust in the steel material and the like inside the concrete structure. When the concrete structure is repaired using the above-mentioned mortar hardened body, the firing rate can be, for example, 60% or less, 50% or less, 45% or less, or 40 or less.

In the present specification, the "generation rate" is the specimen (mortar hardening) molded in conformity with "3.6 Anti-rust Test Method" of "Quality Standard (Proposed) of Reinforced Concrete Repair Anti-corrosion Material" edited by Architectural Institute of Japan. (Corresponding to the body) is the value obtained by dividing the radiated area of the steel bar after curing in air for 2 weeks under the conditions of temperature: 20° C. and relative humidity: 65% RH divided by the effective area of the steel bar.

Although some embodiments have been described above, the present disclosure is not limited to the above embodiments. Moreover, the description of the above-described embodiments can be applied to each other.

Hereinafter, the content of the present disclosure will be described in more detail with reference to Examples and Comparative Examples. However, the present disclosure is not limited to the following examples.

(Example 1)
<Preparation of Alumina Cement Composition for Salt Barrier Mortar>
An alumina cement composition for salt barrier mortar having the following composition was prepared. The alumina cement composition for salt-barrier mortar has a mineral composition of CA: 64% by mass, C ₁₂ A ₇ : 7% by mass, C ₄ AF: 18% by mass, and C ₂ AS: 4% by mass. (Blaine specific surface area: 2700 cm ² /g) 100 parts by mass, hemihydrate gypsum (Blaine specific surface area: 4380 cm ² /g) 20.0 parts by mass, calcium carbonate (Blaine specific surface area: 3000 cm ² /g) 25. 6 parts by mass, silica fume (BET specific surface area: 19 m ² /g) 7.7 parts by mass, silica sand (mass ratio of particles having a particle diameter of 1200 μm or more, not including particles having a particle diameter of 1700 μm or more, and fine aggregate). Is 1.48 mass %, the mass ratio of particles having a particle diameter of 600 μm or more is 49.13 mass %, the mass ratio of particles having a particle diameter of 300 μm or more is 44.04 mass %, and the mass ratio of particles having a particle diameter of 150 μm or more is 4 0.06% by mass, the mass ratio of particles having a particle diameter of 75 μm or more is 1.26% by mass, 147.6 parts by mass, Na gluconate (sodium gluconate) is 0.09 parts by mass, and Na tartrate (sodium tartrate) is 0.37 parts by mass, Na bicarbonate (sodium bicarbonate) was 0.37 parts by mass, and the resin (styrene-acrylic copolymer, glass transition temperature: 21° C.) was adjusted to be 5.85 parts by mass. .. The water reducing agent was appropriately added to improve the fluidity. The resin used was powder.

<Preparation of mortar>
Into a container, 2.0 kg of the above-mentioned alumina cement composition for mortar and a predetermined amount of water are measured and mixed under a condition of temperature: 20° C. and relative humidity: 65% RH for 2 minutes using a chemi-stirrer. Thus, a mortar was prepared. The blending amount of water for preparing the mortar is such that the mass of water is W and the total mass of the alumina cement composition for mortar is P, and the total mass P of the alumina cement composition for mortar is water. The mass W ratio (W/P) was adjusted to 0.128.

[Mineral composition of alumina cement]
The mineral composition of the alumina cement was measured by the WPF analysis method using powder X-ray diffraction. The powder X-ray diffraction measurement uses a powder X-ray diffractometer (manufactured by Rigaku Corporation, product name: RINT-2500), and tube voltage: 35 kV, tube current: 110 mA, measurement range: 2θ=10 to 60°, step width. : 0.02°, counting time: 2 seconds, divergence slit: 1°, and light receiving slit: 0.15 mm.

As the WPF analysis method, powder X-ray diffraction pattern comprehensive analysis software (manufactured by Materials Data Inc., product name: JADE 6.0) was used. With respect to the mineral composition shown in Table 1, the reference document was used as an initial value, each crystal phase was refined and fitting was performed, and the mineral composition was measured with the total amount of each mineral being 100. The obtained mineral composition is shown in Table 2. Note that CaO is represented by C, Al ₂ O _{3 is represented} by A, SiO ₂ is represented by S, Fe ₂ O ₃ is represented by F, and SO ₃ is represented by S.

Reference 2: Ito, S. et al. , Suzuki, K., Inagaki, M.; , Naka, S.; Mater. Res. Bull. , V. 15, p. 925 (1980)
Reference 3: Natl. Bur. Stand. (U.S.), Circ. 539, vol. 9, p. 20 (1960)
Reference 4: Colville, A.; A. , Geller, S.; Acta Crystallogr. , Sec. B, vol. 27, p. 2311 (1971)
Reference 5: Louisnathan, S.; J. Can. Mineral. , V. 10, p. 822 (1971)

[Evaluation of initial length change due to hardening of mortar]
With respect to the mortar prepared as described above, the amount of change in initial length with hardening of the mortar was evaluated. More specifically, the evaluation was performed by measuring the amount of change in the initial length of the cured mortar cast in the device using a device for measuring the amount of change in length as shown in FIG.

FIG. 2 is a schematic diagram of a length change amount measuring device. FIG. 2 is a schematic top view of the length change amount measuring device 10. FIG. 3 is a schematic cross-sectional view taken along the line II-II in FIG. The length change amount measuring device 10 has a form 11 that forms a container 20 in which mortar is placed. The side wall 11a at one end in the longitudinal direction of the mold 11 has a surface (inner surface) on the housing portion 20 side of the side wall 11a and a surface (outer surface) opposite to the housing portion 20 side of the side wall 11a, respectively. It has a cushioning material 14. The length change amount measuring device 10 has the side wall 11a and a SUS rod 13a arranged so as to penetrate the two cushioning members 14 provided on both sides thereof. The rod 13a can move along the longitudinal direction of the mold 11 (direction indicated by x or y in FIG. 2). A disc 12a and a disc 12b made of SUS are provided at both ends of the rod 13a. SUS means a stainless steel material specified in JIS.

The length change amount measuring device 10 further includes a SUS rod 13b on a side wall 11b of the formwork 11 that faces the side wall 11a. A disk 12c made of SUS is provided at the end of the rod 13b opposite to the side wall 11b. The disk 12c is provided so as to face the disk 12b. The distance d between the disks 12b and 12c before the measurement of the amount of change in length is 210 mm. As shown in FIG. 3, a fluororesin layer 16 is provided on the inner surface of the mold 11. Here, the height of the inner wall of the mold 11 (shown as h in FIG. 3) is 30 mm, and the width of the bottom surface of the inner wall of the mold 11 in the lateral direction (shown as w in FIG. 3) is 40 mm. ..

When the mortar cast in the mold 11 contracts as it hardens, the positions of the disks 12a and 12b are displaced in the x direction from the positions before measurement. Further, when the mortar cast in the mold 11 expands as it hardens, the positions of the disks 12a and 12b are displaced in the arrow y direction from the positions before measurement. A displacement sensor 15 capable of measuring the displacement of the disk 12a in the xy direction is arranged outside the mold 11. The displacement sensor 15 detects displacement using a laser.

Using the length change measuring device 10 as described above, the mortar immediately after being mixed with water is cast in the housing portion 20 of the mold 11 to the height of the mold, and the temperature is 20° C. and the relative humidity is 20° C. It was cured in the atmosphere under the condition of 65% RH. From the time immediately after placing to 24 hours later, the change in the length of the placed mortar (semi-hardened mortar) (displacement a of the disk 12a in the xy direction) was measured every one minute.

The initial amount of change in length of the cast mortar (semi-cured mortar) due to curing was calculated based on the following formula (2) using the measurement results as described above. The results are shown in Table 3.

Length change amount (μm/m)=(a/d)×1000 (2)
In the above formula (2), a represents the displacement a (μm) of the disk 12a in the xy direction, and d represents the distance d (m) between the disks 12b and 12c before measurement. A negative value for the length change means that the mortar is shrinking as it hardens, and a positive value for the length change means that the mortar is expanding as it hardens. To do.

<Evaluation of cured mortar>
With respect to the cured mortar formed using the mortar prepared as described above, the salt barrier property, the compressive strength, and the amount of corrosion were evaluated.

[Salt barrier]
About the mortar hardened body formed using the above mortar, "Effective diffusion coefficient test method of chloride ion in concrete by electrophoresis" (draft) in "Concrete Standard Specification JSCE-G 571-2013" edited by Japan Society of Civil Engineers Electrophoresis test of chloride ion in accordance with the above, and based on "Appendix (Reference) Apparent Diffusion Coefficient Calculation Method Using Effective Diffusion Coefficient by Electrophoresis Test" The diffusion coefficient was determined. The results are shown in Table 3.

[Compressive strength]
About the mortar hardened body formed by using the above mortar, a specimen molded in conformity with "3.6 Antirust Test Method" of "Quality Standard for Anticorrosive Materials for Repair of Reinforced Concrete (Draft)" edited by Architectural Institute of Japan ( (Corresponding to a hardened mortar) was cured for 2 weeks in air under the conditions of temperature: 20°C and relative humidity: 65% RH, and the emission area of the steel bar was divided by the effective area of the steel bar to obtain the emission rate. It was The results are shown in Table 3.

<Construction of mortar>
Mortar construction was performed outdoors using the above mortar by a spraying method onto a concrete structure. The spraying method was performed using an apparatus as shown in FIG. In addition, each spraying was adjusted so that the thickness after construction was 10 mm. After applying the mortar, the mortar was cured and the appearance of the cured mortar was evaluated. It was confirmed that the mortar hardened body did not crack and had good integrity with the concrete structure.

(Examples 2 to 4 and Comparative Examples 1 to 3)
An alumina cement composition for salt-blocking mortar was prepared in the same manner as in Example 1 except that the charged amount (parts by mass) of each component was changed as shown in Table 3. The amount of the water reducing agent was appropriately adjusted in order to secure the fluidity when preparing the mortar.

A mortar was prepared in the same manner as in Example 1 using the prepared alumina cement composition for salt-barrier mortar. Then, the initial length change amount of the mortar was evaluated in the same manner as in Example 1. Further, with respect to the mortar hardened body formed using the mortar, the salt barrier property, the compressive strength, and the corrosion amount were evaluated in the same manner as in Example 1. The results are shown in Table 3.

Mortar construction was performed on the mortars prepared in Examples 2 to 4 and evaluated in the same manner as in Example 1. It was confirmed that, when any of the mortars was used, the hardened mortar did not crack and had good integrity with the concrete structure.

According to the present disclosure, the amount of change in initial length due to curing is small, and it is possible to form a mortar cured product having excellent salt-shielding properties when integrated with a concrete structure. A repair method can be provided.

10... Length change amount measuring device, 11... Formwork, 12a, 12b, 12c... Disc, 13a, 13b... Rod, 14... Buffer material, 15... Displacement sensor, 16... Fluorine resin layer, 20... Housing part, 30 ... Mortar, 41... Mixer, 42... Mortar pump with hopper, 43... Air source, 44... Pressure-resistant hose, 45... Spray gun, 50... Concrete structure.

Claims (4)

The process of applying mortar to the concrete structure,
Forming a cured mortar by curing the mortar,
A method for repairing salt-barrier mortar, comprising:
The mortar is a mixture of an alumina cement composition for salt-barrier mortar and water,
The salt-blocking mortar alumina cement composition contains alumina cement and hemihydrate gypsum,
The alumina cement contains 55% by mass to 75% by mass of CA, 5% by mass to 8% by mass of C ₁₂ A ₇ , 10% by mass to 28% by mass of C ₄ AF, and 2% by mass of 6% of C ₂ AS. Including mass %,
Blaine specific surface area of the alumina cement ^is 2000cm ² / g~4000cm 2 / g,
The Blaine specific surface area of the hemihydrate gypsum ^is a 3000cm ² / g~6000cm 2 / g,
The salt-blocking mortar repair method, wherein the content of the hemihydrate gypsum is 10 parts by mass to 24 parts by mass with respect to 100 parts by mass of the alumina cement. The method for repairing salt-blocking mortar according to claim 1, wherein the alumina cement composition for salt-blocking mortar further contains at least one selected from the group consisting of calcium carbonate and silica fume. The salt-shielding mortar repair method according to claim 2, wherein the content of the calcium carbonate is 15 parts by mass to 35 parts by mass with respect to 100 parts by mass of the alumina cement. The method for repairing salt-blocking mortar according to claim 2 or 3, wherein the content of the silica fume is 3 to 12 parts by mass with respect to 100 parts by mass of the alumina cement.

Images