JP2019006667A - Alumina cement composition for salt shielding mortar - Google Patents

Abstract

To provide an alumina cement composition for salt shielding mortar capable of achieving excellent salt shielding mortar, excellent long term durability and excellent crack resistance.SOLUTION: The alumina cement composition for salt shielding mortar is an alumina cement composition for salt shielding mortar containing alumina cement and gypsum hemihydrate, in which alumina cement contains CA of 55 mass% to 75 mass%, CAof 5 mass% to 8 mass%, CAF of 10 mass% to 28 mass% and CAS of 2 mass% to 6 mass%, Blaine specific area of the alumina cement is 2000 cm/g to 4000 cm/g, and the gypsum hemihydrate is contained at 15 pts.mass to 35 pts.mass based on 100 pts.mass of the alumina cement.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an alumina cement composition for salt-insulating mortar.

  Alumina cement is known to have better chemical resistance than Portland cement or the like (for example, Patent Document 1).

JP 2008-174429 A

  However, alumina cement may cause a decrease in compressive strength due to aging or high temperature curing. Alumina cement also has a problem that cracks are likely to occur due to shrinkage.

  The main object of the present invention is to provide an alumina cement composition for a salt-blocking mortar capable of realizing excellent salt-blocking properties, excellent long-term durability and excellent crack resistance.

As a result of diligent research, the inventors of the present invention, in an alumina cement composition for a salt-blocking mortar containing alumina cement and hemihydrate gypsum, have an alumina cement content of CA 55 mass% to 75 mass%, C ₁₂ A ₇ 5 mass% to 8 _wt%, C 4 intended to include AF10 wt% to 28 wt% and _C 2 AS2 wt% to 6 wt%, the Blaine specific surface area of the alumina ^cement, and 2000cm ² / g~4000cm 2 / g, alumina cement 100 parts by weight On the other hand, it is conceived that the salt-insulating property, long-term durability and crack resistance of the alumina cement composition for salt-insulating mortar can be improved by containing hemihydrate gypsum in an amount of 15 to 35 parts by mass. As a result, the present invention has been achieved.

That is, the alumina cement composition for salt-blocking mortar according to the present invention is an alumina cement composition for salt-blocking mortar containing alumina cement and hemihydrate gypsum, wherein the alumina cement is CA 55 mass% to 75 mass%, C ₁₂ A ₇ 5 mass% to 8 mass%, C ₄ AF 10 mass% to 28 mass% and C ₂ AS 2 mass% to 6 mass%, the brane specific surface area of the alumina cement is 2000 cm ² / g to 4000 cm ² / It is g and contains 15 to 35 parts by mass of hemihydrate gypsum with respect to 100 parts by mass of the alumina cement.

  The alumina cement composition for salt-insulating mortar according to the present invention preferably further contains at least one of calcium carbonate and silica fume.

  The alumina cement composition for salt-insulating mortar according to the present invention preferably contains 15 to 35 parts by mass of calcium carbonate and 5 to 12 parts by mass of silica fume with respect to 100 parts by mass of the alumina cement.

  ADVANTAGE OF THE INVENTION According to this invention, the alumina cement composition for salt-insulating mortar which can implement | achieve the outstanding salt-insulating property, the outstanding long-term durability, and the outstanding crack resistance can be provided.

It is typical sectional drawing of the apparatus for measuring the amount of length changes at the time of curing of salt-insulating mortar. It is typical sectional drawing in line (b)-(b) of FIG.

(Alumina cement composition for salt-blocking mortar)
The alumina cement composition for salt-insulating mortar according to the present invention can be suitably used, for example, for repairing concrete structures.

  The alumina cement composition for salt-blocking mortar according to the present invention is an alumina cement composition for salt-blocking mortar containing alumina cement and hemihydrate gypsum.

In the alumina cement composition for salt-insulating mortar according to the present invention, the alumina cement is composed of CA 55 mass% to 75 mass%, C ₁₂ A ₇ 5 mass% to 8 mass%, C ₄ AF 10 mass% to 28 mass%, and C. ₂ AS 2 mass%-6 mass% is included. Blaine specific surface area of the alumina cement ^is 2000cm ² / g~4000cm 2 / g. The alumina cement composition for salt-insulating mortar according to the present invention contains 15 to 35 parts by mass of hemihydrate gypsum with respect to 100 parts by mass of the alumina cement. Therefore, by using the alumina cement composition for salt-insulating mortar according to the present invention, excellent salt-insulating property, excellent long-term durability and excellent crack resistance can be realized.

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

Among the alumina cements, there is an alumina cement containing 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 to 6% by mass of C ₂ AS. Preferably used, CA 58 mass% to 72 mass%, C ₁₂ A ₇ 5.6 mass% to 7.8 mass%, C ₄ AF 13 mass% to 25 mass%, C ₂ AS 2.5 mass% to 5.5 mass% % Is more preferably used, and CA 62 mass% to 68 mass%, C ₁₂ A ₇ 5.4 mass% to 7.6 mass%, C ₄ AF 16 mass% to 22 mass%, C ₂ AS3.0. Alumina cement containing from mass% to 5.0 mass% is more preferably used. By using the alumina cement having the above composition, the salt barrier property, long-term durability and crack resistance can be further improved.

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

(Half water plaster)
The alumina cement composition for salt-insulating mortar according to the present invention contains hemihydrate gypsum. As the hemihydrate gypsum, both α-type hemihydrate gypsum and β-type hemihydrate gypsum can be used. Both α-type hemihydrate gypsum and β-type hemihydrate gypsum may be mixed and used.

  The content of hemihydrate gypsum in the alumina cement composition for salt-insulating mortar according to the present invention is 15 to 35 parts by mass, preferably 18 to 32 parts by mass with respect to 100 parts by mass of the alumina cement. More preferably, it is 22 parts by mass to 28 parts by mass. By making the content of hemihydrate gypsum within the above range, the amount of shrinkage during curing can be made smaller. Therefore, the crack resistance can be further improved.

Blaine specific surface area of the hemihydrate gypsum is preferably 3500cm ² / g~12000cm ² / g, more preferably from 3500cm ² / g~10000cm ² / g, more preferably 3500cm ² / g~5500cm ² / g , and still more preferably from 4000cm ² / g~5000cm ² / g, more preferably from 4200cm ² / g~4600cm ² / g. By setting the brane specific surface area of hemihydrate gypsum within the above range, the amount of shrinkage during curing can be further reduced. Therefore, the crack resistance can be further improved. In addition, the brane specific surface area of hemihydrate gypsum can be calculated | required according to JISR5201: 2015.

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

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

  The content of calcium carbonate is preferably 15 parts by mass to 35 parts by mass with respect to 100 parts by mass of alumina cement, more preferably 18 parts by mass to 32 parts by mass, and 20 parts by mass to 30 parts by mass. More preferably it is. Long-term durability can be further improved by adjusting the content of calcium carbonate within the above range.

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

(Silica fume)
The alumina cement composition for salt-insulating mortar according to the present invention may contain silica fume. Examples of silica fume preferably used include silica fume defined in JIS A 6207-2006 “Silica fume for concrete”. By including silica fume in the alumina cement composition for salt-blocking mortar according to the present invention, the mortar cured body can be densified, so that a mortar-cured body with higher strength and superior salt blocking properties is realized. obtain. The alumina cement composition for salt-insulating mortar according to the present invention may contain only one type of silica fume or may contain a plurality of types of silica fume.

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

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

(Fine aggregate)
The alumina cement composition for salt-insulating mortar according to the present invention may contain fine aggregate. Examples of the fine aggregate preferably used include sands such as quartz sand, river sand, land sand, sea sand, and crushed sand. The alumina cement composition for salt-insulating mortar according to the present invention may contain only one type of fine aggregate, or may contain a plurality of types of fine aggregate.

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

  As the fine aggregate, a fine aggregate which does not contain particles having a particle diameter of 1700 μm or more and whose mass ratio of particles having a particle diameter of 1200 μm or more with respect to the whole fine aggregate is 20 mass% or less is preferably used. By making the content of coarse particles having a particle diameter of 1200 μm or more 20% by mass or less, the homogeneity in the mortar cured body obtained from the alumina cement composition for salt-blocking mortar can be improved. This can be further improved. From the viewpoint of realizing superior salt barrier properties, the mass ratio of particles having a particle diameter of 1200 μm or more with respect to the entire fine aggregate is more preferably 0.05% by mass to 20% by mass, and still more preferably 0. It is 0.01 mass%-15 mass%, More preferably, it is 0.05 mass%-10 mass%, More preferably, it is 0.1 mass%-3 mass%.

  In addition, the particle diameter of the fine aggregate can be measured using several sieves having different nominal dimensions as defined in JIS Z 8801-2006. In the present invention, the “mass ratio of particles having a particle diameter of 1200 μm or more” refers to the mass ratio of particles on the sieve when a sieve having a sieve mesh of 1200 μm is used.

(Fluidizer)
The alumina cement composition for salt-insulating mortar according to the present invention may contain a fluidizing agent. Preferable fluidizing agents include, for example, formaldehyde condensates of melamine sulfonic acid, casein, calcium caseinate, polycarboxylic acid based fluidizing agents, polyether based fluidizing agents, Ether carboxylic acid etc. are mentioned. Of these, polycarboxylic acid-based fluidizing agents, polyether-based fluidizing agents, and polyether carboxylic acids are more preferably used as fluidizing agents, and polycarboxylic acid esters are more preferably used. The alumina cement composition for salt-insulating mortar according to the present invention may contain only one kind of fluidizing agent, or may contain plural kinds of fluidizing agents.

  The content of the fluidizing agent is preferably 0.02 parts by mass to 1.00 parts by mass, more preferably 0.04 parts by mass to 0.50 parts by mass, and still more preferably 0 with respect to 100 parts by mass of the alumina cement. 0.07 to 0.40 parts by mass, more preferably 0.10 to 0.30 parts by mass. By setting the content of the fluidizing agent in the above-described range, the long-term durability of the mortar cured product can be further improved, and suitable fluidity of the mortar can be realized.

(Setting retarder)
The alumina cement composition for salt-blocking mortar according to the present invention may contain a setting retarder. Examples of the setting retarder preferably used include organic acids such as oxycarboxylic acids, sugars such as glucose, maltose, and dextrin, sodium bicarbonate, sodium phosphate, and the like. Specific examples of the oxycarboxylic acids include oxycarboxylic acids and salts thereof. Specific examples of the oxycarboxylic acid include, for example, citric acid, gluconic acid, tartaric acid, glycolic acid, lactic acid, hydroacrylic acid, α-oxybutyric acid, glyceric acid, tartronic acid, malic acid and other aliphatic oxyacids, salicylic acid, Examples thereof include aromatic oxyacids such as m-oxybenzoic acid, p-oxybenzoic acid, gallic acid, mandelic acid and tropic acid. Examples of the oxycarboxylic acid salt include alkali metal salts (specifically, sodium salt and potassium salt) and alkaline earth metal salts (specifically calcium salt, barium salt, magnesium salt, etc.) and the like. . Of these, sodium salts are more preferably used, sodium tartrate is more preferably used, and sodium tartrate and sodium bicarbonate are more preferably used in combination. The alumina cement composition for salt-blocking mortar according to the present invention may contain only one type of setting retarder, or may contain a plurality of types of setting retarders.

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

(Synthetic resin fiber)
The alumina cement composition for salt-insulating mortar according to the present invention may contain synthetic resin fibers. By containing synthetic resin fiber, it can suppress effectively that a crack arises in mortar hardened | cured material.

  Examples of the synthetic resin fibers preferably used include polyolefins such as polyethylene, ethylene / vinyl acetate copolymer (EVA) and polypropylene; and synthetic resin components such as polyester, polyamide, polyvinyl alcohol, vinylon and polyvinyl chloride. . The alumina cement composition for salt-insulating mortar according to the present invention may contain only one type of synthetic resin fiber, or may contain a plurality of types of synthetic resin fibers.

  The fiber length of the synthetic resin fiber is preferably 0 from the viewpoints of handling property when mixed with the salt-blocking alumina cement composition, improvement of dispersibility in the salt-blocking mortar composition, and improvement of properties of the mortar cured body. It is 0.5 mm-15.0 mm, More preferably, it is 1.0 mm-12.0 mm, More preferably, it is 2.0 mm-8.0 mm, More preferably, it is 2.5 mm-7.0 mm.

  The content of the synthetic 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 still more preferably 0.001 parts by mass with respect to 100 parts by mass of the alumina cement. It is 04 mass part-0.3 mass part, More preferably, it is 0.05 mass part-0.15 mass part.

  By adjusting the fiber length and content of the synthetic resin fiber to the above ranges, the crack resistance of the mortar cured body can be further improved without impairing the salt barrier property and durability.

(Synthetic resin emulsion, synthetic resin powder)
The alumina cement composition for salt-insulating mortar according to the present invention may contain a synthetic resin emulsion or a synthetic resin powder. By containing a synthetic resin emulsion or a synthetic resin powder, the salt barrier property can be further improved. Here, “synthetic resin emulsion” refers to a synthetic resin particle emulsified and dispersed in water or a water-containing solvent.

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

  The glass transition temperature (Tg) of the synthetic resin component contained in the synthetic resin emulsion is a differential scanning calorimeter (DSC) after a suitable amount of the synthetic resin emulsion is dropped on a glass plate and dried to obtain a dry coating film. Can be measured under the following conditions. The glass transition temperature (Tg) of the synthetic resin component contained in the synthetic resin powder can be measured under the following conditions using a differential scanning calorimeter (DSC) as it is in the powder form. In this specification, a method for measuring the glass transition temperature (Tg) of a synthetic resin component using a differential scanning calorimeter is referred to as a DSC method.

  After the synthetic resin emulsion dry coating film or synthetic resin powder was heated from room temperature to 150 ° C. over 10 minutes and held at 150 ° C. for 10 minutes, the temperature was lowered to a temperature 50 ° C. lower than the Tg of the sample obtained by calculation. Lower. Thereafter, the temperature is raised again to 150 ° C. in 10 minutes. In the process, the first glass transition temperature (Tg) is measured, and then the second Tg is measured in the process of lowering the temperature to 50 ° C. lower than the Tg measured in the first, and the second Tg is measured. The value is defined as the glass transition temperature of the synthetic resin emulsion.

  Examples of synthetic resin emulsions preferably used include acrylic emulsions and vinyl acetate emulsions. Examples of the synthetic resin for the synthetic resin emulsion include (meth) acrylic acid derivatives such as (meth) acrylic acid and (meth) acrylic acid esters; α-olefin compounds such as ethylene and vinyl acetate; vinyl compounds such as styrene; Polymers or copolymers of polymerization components such as

  Among these, acrylic emulsions are more preferably used from the viewpoint of realizing excellent salt barrier properties. Examples of acrylic emulsions include (meth) acrylic such as acrylic acid and methacrylic acid; polymers of (meth) acrylic acid derivatives such as (meth) acrylic acid esters; polymers of (meth) acrylic acid derivatives and styrene, and the like. Can be mentioned. Specifically, examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. The alumina cement composition for salt-insulating mortar according to the present invention may contain only one type of synthetic resin emulsion, or may contain a plurality of types of synthetic resin emulsions.

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

  The solid content of the synthetic resin emulsion is the mass of the solid content remaining after evaporation of the water in the synthetic resin emulsion. The water content in the synthetic resin emulsion is obtained by subtracting the solid content from the synthetic resin emulsion. Moreover, the powder part of the alumina cement composition for salt-blocking mortar means a powder part excluding the liquid component when the alumina cement composition for salt-blocking mortar includes a liquid component. In the case where the alumina cement composition for salt-blocking mortar is composed of only the powder component without containing a liquid component, the powder part of the alumina cement composition for salt-blocking mortar is the alumina cement composition for salt-blocking mortar. It means the whole thing. By making content of a synthetic resin emulsion into the above-mentioned range, adhesiveness with concrete and salt-insulating property can be improved further.

  Specific examples of the synthetic resin powder preferably used include styrene / acrylic copolymer, acrylic, vinyl acetate / veova / acrylic copolymer, and ethylene vinyl acetate copolymer.

  The content of the synthetic resin powder is preferably 0.1% by mass to 10% by mass, and more preferably 0.3% by mass with respect to 100 parts by mass of the powder part of the alumina cement composition for salt-insulating mortar. % To 5.0% by mass, and more preferably 1.0% to 3.0% by mass.

(Use of salt-blocking alumina cement composition)
The alumina cement composition for salt-insulating mortar according to the present invention can be suitably used, for example, for repairing a concrete structure. By using the alumina cement composition for salt-blocking mortar of the present invention, a salt-blocking mortar that can be easily applied with a glazing or spraying can be obtained.

  The salt-blocking mortar obtained from the alumina cement composition for salt-blocking mortar according to the present invention can be prepared by blending and kneading the alumina cement composition for salt-blocking mortar according to the present invention and water. .

  The amount of water added to the alumina cement composition for salt-inhibiting mortar is preferably 2 to 18 parts by mass, more preferably 4 to 100 parts by mass of the alumina cement composition for salt-inhibiting mortar. It is mass part-16 mass parts, More preferably, it is 10 mass parts-14 mass parts, More preferably, they are 11 mass parts-13 mass parts. In addition, when a synthetic resin emulsion is contained, it is necessary to subtract the amount of water contained in the synthetic resin emulsion from the amount of water added.

  The salt-blocking mortar can be cured by curing the salt-blocking mortar. The cured salt-blocking mortar formed in this way has excellent salt-blocking properties, compressive strength, strength maintenance performance during long-term curing (long-term durability), and crack resistance when integrated with concrete structures. It is suitable as a mortar hardened body for repairing concrete structures.

  In addition, the salt barrier property conforms to the test method described in JSCE-G571-2010 “Test method for effective diffusion coefficient of chloride ions in concrete by electrophoresis (draft)” and “Attachment (reference) electrophoresis”. The apparent diffusion coefficient calculation method using the effective diffusion coefficient by the test "can be used.

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

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

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

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

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

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

  When the apparent diffusion coefficient and compressive strength, and the rate of change in compressive strength and the amount of change in length during high-temperature curing are within the above-mentioned ranges, excellent barrier properties are obtained when integrating a salt-blocking mortar hardened body with a concrete structure. Saltiness, excellent long-term durability and excellent crack resistance can be achieved.

  Hereinafter, the present invention will be described in more detail on the basis of specific examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented without departing from the scope of the present invention. Is possible.

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

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

(Evaluation)
(1) Salt barrier (apparent diffusion coefficient of chloride ion)
About each obtained mortar, according to Japan Society of Civil Engineers, concrete standard specifications JSCE-G 571-2013 "Effective diffusion coefficient test method of chloride ion in concrete by electrophoresis (draft)" Conduct an electrophoresis test, and determine the apparent diffusion coefficient (cm ² / year) of chloride ions in mortar based on “Appendix (Reference) Method for calculating apparent diffusion coefficient using effective diffusion coefficient by electrophoresis test”. It was. The results are shown in Table 1.

(2) Compressive strength About each obtained mortar, based on JISR5201 "physical test method of cement", the compressive strength after 28 days of age in each underwater curing temperature 20 degreeC and 50 degreeC was measured. From the measured value, the compression strength change rate was calculated based on the following formula. The results are shown in Table 1.
x = (y2−y1) × 100 / y1
However,
x: Compressive strength change rate (%)
y1: compressive strength (N / mm ² ) after 28 days of age at an underwater curing temperature of 20 ° C.
y2: Compressive strength (N / mm ² ) after 28 days of age at an underwater curing temperature of 50 ° C.
It is.

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

  First, the structure of the apparatus for measuring the length change amount at the time of curing salt-inhibiting mortar will be described. As shown in FIG. 1, the length variation measuring device 10 includes a mold 11. By the mold 11, salt-insulating mortar is placed in the compartments 20 that are partitioned. In the length variation measuring apparatus 10 used in this example, the height (h) of the mold 11 is 30 mm and the width (W) is 40 mm (see FIG. 2).

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

  A rod 13b is provided on the inner side of the side wall located at the other end portion in the longitudinal direction of the mold 11. The bar 13b does not penetrate the side wall. A disk 12c is provided at the tip of the bar 13b. Specifically, the disk 12c is provided in the edge part on the opposite side to the side wall side of the formwork 11 among the stick | rods 13b. The disk 12 c faces the disk 12 b in the longitudinal direction of the mold 11.

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

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

  When the salt-blocking mortar is placed on the mold 11, when the salt-blocking mortar contracts, the disks 12a and 12b are displaced from the positions before measurement in the direction of the arrow x as the salt-blocking mortar contracts. . On the other hand, when the salt-blocking mortar expands, the disks 12a and 12b are displaced in the direction of the arrow y from the position before the measurement. A laser displacement sensor 15 capable of measuring the displacement of the disk 12a in the x and direction directions is provided outside the mold 11.

  The salt-blocking mortar immediately after kneading obtained in each of Example 1 and Comparative Examples 1 to 3 was placed in the accommodating portion 20 of the mold 11 up to the height of the mold, and the temperature was 20 ° C. and the humidity was 65% RH. Curing was performed in the atmosphere, and the amount of change in length 24 hours after the placement was measured.

The amount of change in length of the salt-blocking mortar was calculated based on the following formula. The results are shown in Table 1.
Length change = (a × 1000) / d
However,
a: Displacement (μm) of hydraulic mortar after 24 hours of curing
d: Distance d (2100 mm) before curing between the disk 12b and the disk 12c

  In Table 1, when the amount of change in length is a negative value, it indicates that it has contracted due to curing, and when it is a positive value, it indicates that it has expanded due to curing.

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

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

(2) Admixture B1: Hydrofluoric acid anhydrous gypsum (Brain specific surface area 4140 cm ² / g, mass ratio 2% of particles having a particle diameter of 300 μm or more, mass ratio 85% of particles having a particle diameter of less than 150 μm)
B2: hemihydrate gypsum (Blaine specific surface area 4380 cm ² / g)
B3: Calcium carbonate (Blaine specific surface area 4480 cm ² / g)
B4: Silica fume (BET specific surface area 19 m ² / g)

(3) Fine aggregate C: Silica sand (excluding particles with a particle diameter of 1700 μm or more, with respect to the entire fine aggregate, the mass ratio of particles having a particle diameter of 1200 μm or more is 1.48% by mass, and particles having a particle diameter of 600 μm or more. The mass ratio is 49.13 mass%, the mass ratio of particles having a particle diameter of 300 μm or more is 44.04 mass%, the mass ratio of particles having a particle diameter of 150 μm or more is 4.06 mass%, and the mass ratio of particles having a particle diameter of 75 μm or more. Is 1.26% by mass)

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

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

10: Length change measuring device 11: Forms 12a, 12b, 12c: Disks 13a, 13b: Rod 14: Buffer material 15: Displacement sensor 16: Fluororesin sheet 20: Housing

Claims (3)

Alumina cement composition for salt-blocking mortar comprising alumina cement and hemihydrate gypsum,
The alumina cement comprises CA55 wt% to 75 _{wt%, C} 12 _{A 7} 5 wt% to 8 _wt%, the C 4 AF10 wt% to 28 wt% and _C 2 AS2 wt% to 6 wt%,
Blaine specific surface area of the alumina cement ^is 2000cm ² / g~4000cm 2 / g,
An alumina cement composition for salt-insulating mortar, containing 15 to 35 parts by mass of the hemihydrate gypsum with respect to 100 parts by mass of the alumina cement.   The alumina cement composition for salt-insulating mortar according to claim 1, further comprising at least one of calcium carbonate and silica fume.   The alumina cement composition for salt-insulating mortar according to claim 2, comprising 15 parts by mass to 35 parts by mass of the calcium carbonate and 5 parts by mass to 12 parts by mass of the silica fume with respect to 100 parts by mass of the alumina cement. .

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