JP2022170699A - Freeze-thaw resistance improver for hydraulic inorganic hardened body, hydraulic inorganic hardened body, and method for producing hydraulic inorganic hardened body - Google Patents

Abstract

To provide an agent that can be used as a substitute for an air-borne agent such as an AE agent and can effectively improve the freeze-thaw resistance of a hydraulic inorganic hardened body, a hydraulic inorganic hardened body, and a method for producing a hydraulic inorganic hardened body.SOLUTION: A freeze-thaw resistance improver for hydraulic inorganic hardened materials contains cellulose fibers as an active ingredient.SELECTED DRAWING: Figure 5

Description

TECHNICAL FIELD The present invention relates to a freeze-thaw resistance improver for a hydraulic inorganic hardened material, a hydraulic inorganic hardened material, and a method for producing a hydraulic inorganic hardened material.

Concrete used in cold climates undergoes rapid cycles of freezing and thawing. When the water in the concrete freezes and expands, pressure is applied to the concrete, and when this pressure reaches the tensile strength, cracks may occur. Since water easily penetrates into the concrete where cracks occur, the moisture that penetrates from the outside will generate even greater expansion pressure in the next freeze, expanding the cracks and causing further damage, creating a vicious cycle. It is easy to fall into

Various methods have been proposed to increase the freeze-thaw resistance of concrete.

Patent Document 1 discloses a method of mixing an appropriate amount of a chemical admixture such as an air entraining agent (AE agent) into fresh concrete in order to form fine air bubbles in the concrete. Further, Patent Document 2 discloses a method of adding an AE agent as a liquid air-entraining agent to improve the frost damage resistance of concrete.

JP-A-10-259050 JP-A-2000-95551

However, the air entraining agent such as the AE agent used in the methods of Patent Documents 1 and 2 cannot obtain the effect of improving frost damage resistance unless it is added in a relatively large amount. There was a risk of causing a decrease in the strength of the

The present invention has been made in view of the above circumstances, and an agent that can be used as a substitute for an air entraining agent such as an AE agent and can effectively improve the freeze-thaw resistance of a hydraulic inorganic hardened material, An object of the present invention is to provide a hydraulic inorganic hardened body and a method for producing the hydraulic inorganic hardened body.

In order to achieve the above object, the freeze-thaw resistance improver of the hydraulic inorganic hardening material according to the first aspect of the present invention is
It contains cellulose fiber as an active ingredient.

For example, the cellulose fibers are bacterial cellulose.

For example, the bacterial cellulose fiber content is 0.005 to 0.5% by weight with respect to the hydraulic inorganic hardened material.

The hydraulic inorganic hardening material according to the second aspect of the present invention contains bacterial cellulose.

For example, the bacterial cellulose fiber content is 0.005 to 0.5% by weight with respect to the hydraulic inorganic hardened material.

A method for producing a hydraulic inorganic hardened material according to a third aspect of the present invention includes:
A step of adding bacterial cellulose is included.

For example, the bacterial cellulose is added at a bacterial cellulose fiber content of 0.005 to 0.5% by weight relative to the hydraulic inorganic hardened material.

According to the present invention, an agent that can be used as a substitute for an air entraining agent such as an AE agent and that can effectively improve the freeze-thaw resistance of a hardened hydraulic inorganic material, a hardened hydraulic inorganic material, and a hydraulic inorganic material. A method for producing a cured product can be provided.

(a) is a photograph of the appearance of B (NFBC culture solution) used in this example, and (b) is a photograph of the appearance of P (purified NFBC) used in this example. It is a graph showing the measurement result of the flow of mortar of a present Example. It is a graph showing the measurement result of the air amount of mortar of a present Example. It is a graph showing the measurement result of the cell spacing coefficient of the mortar of the present example. FIG. 4 is a graph showing the relationship between the relative dynamic modulus of elasticity and the number of times of freezing and thawing in the mortar of the present example. FIG. 4 is a graph showing the relationship between the relative dynamic modulus of elasticity and the number of times of freezing and thawing in the mortar of the present example.

(1. Freeze-thaw resistance improver)
First, the freeze-thaw resistance improver of the hydraulic inorganic hardening material according to the present invention will be described in detail.

The freeze-thaw resistance improver for hydraulically hardened inorganic substances according to the present invention contains cellulose fibers as an active ingredient.

In this specification, the term "hydraulic inorganic hardening material" refers to a material produced by mixing a hydraulic inorganic material, an inorganic admixture, and water. Examples of hydraulic inorganic materials used for the hydraulic inorganic hardening material include cements such as portland cement, fly ash cement, silica cement, blast furnace cement, gypsum cement, microcement, alumina cement, semi-water, dihydrate, and hexahydrate. Gypsums such as gypsum can be mentioned. Cement may be of ordinary hardening type, fast hardening type, rapid hardening type, or ultra fast hardening type. Examples of inorganic admixtures used for hydraulically hardened inorganic substances include fine aggregate, coarse aggregate, crushed sand, crushed stone, silica sand, sea sand, recycled aggregate, mountain sand, river sand, mica, stone powder, and glass. Powder, aluminum powder, silica fume, fly ash, blast furnace slag and the like can be mentioned.

In the present specification, cellulose fiber is not limited to its origin, manufacturing method, properties, etc., but refers to plant-derived cellulose such as pulp-derived cellulose, bacterial cellulose, etc., and fibers that constitute cellulose in the microstructure of cellulose. refers to As cellulose fibers, for example, cellulose nanofibers (eg, pulp-derived cellulose nanofibers, bacterial cellulose nanofibers, etc.) having an average width and an average thickness of 100 nm or less are preferably used.

The cellulose fibers used in the freeze-thaw resistance improver according to the present invention may, for example, have such high dispersibility as to disperse almost uniformly in a liquid (aqueous solvent or organic solvent). The degree of dispersibility of cellulose fibers can be measured, for example, by using the light transmittance as an index. It can be determined by irradiating with light and measuring the amount of transmitted light. Regarding the light transmittance of the cellulose fibers, for example, even if the light transmittance of water containing cellulose fibers at a final concentration of 0.1±0.006% (w/w) at a wavelength of 500 nm is 35% or more. Well, and without being limited thereto, for example, 36% or more, 37% or more, 38% or more, 39% or more, 40% or more, 35% or more and 99% or less, 36% or more and 99% or less, 37% or more 99% or less, 38% to 99%, 40% to 99%, 35% to 95%, 36% to 95%, 37% to 95%, 38% to 95%, 40% to 95% % or less, 35% to 90%, 36% to 90%, 37% to 90%, 38% to 90%, 40% to 90%, 35% to 85%, 36% to 85% Below, 37% to 85%, 38% to 85%, 40% to 85%, 35% to 80%, 36% to 80%, 37% to 80%, 38% to 80% , 40% or more and 80% or less.

In the freeze-thaw resistance improving agent according to the present invention, bacterial cellulose can be suitably used as the cellulose fiber from the viewpoint of the effect of improving freeze-thaw resistance. As used herein, bacterial cellulose refers to cellulose produced by bacterial cellulose-producing bacteria. Bacterial cellulose-producing bacteria can be known bacteria capable of producing bacterial cellulose. Specifically, for example, Gluconacetobacter xylinus ATCC53582 strain, Gluconacetobacter hansenii ATCC23769 strain, and Gluconacetobacter xylinus ATCC700178 strain (BPR2001). BPR3001E strain, Acetobacter xylinum JCM10150 strain, Enterobacter sp. CJF-002 strain, Gluconacetobacter intermedius strain SIID9587 (accession number NITE BP-01495), and the like can be used.

When bacterial cellulose is used for the freeze-thaw resistance improver according to the present invention, the bacterial cellulose fiber content may be, for example, 0.005 to 0.5% by weight relative to the hydraulic inorganic hardened material. By adding 0.005 to 0.5% by weight of bacterial cellulose to the hydraulic inorganic hardening material, the freeze-thaw resistance (freezing damage resistance) of the hydraulic inorganic hardening material is improved. A high improvement effect is obtained. Since this addition amount is smaller than that of the existing AE agents, the effect of improving freeze-thaw resistance (freeze damage resistance) is effectively exhibited while maintaining the strength of the hydraulically hardened inorganic substance. The bacterial cellulose fiber content is, for example, 0.005-0.5% by weight, preferably 0.006-0.4% by weight, more preferably 0.007-0. .3 wt%, even more preferably 0.0075 to 0.1 wt%. The bacterial cellulose fiber content can be calculated based on the amount of bacterial cellulose added, for example, by measuring the amount of cellulose fiber of bacterial cellulose to be added using light transmittance in the same manner as described above.

As the bacterial cellulose, it is preferable to use bacterial cellulose bound with a dispersant from the viewpoint of dispersibility in the hardened hydraulic inorganic material. As a dispersant, hydroxypropyl cellulose (hereinafter sometimes abbreviated as "HPC"), carboxymethyl cellulose (hereinafter sometimes abbreviated as "CMC"), hydroxyethyl cellulose (hereinafter abbreviated as "HEC") There are cases.) etc. can be used.

In the dispersant-bound bacterial cellulose, the amount of binding of the dispersant can be set as appropriate. /w), it is possible to obtain bacterial cellulose that is well dispersed in water. It is believed that the dispersant and bacterial cellulose are bonded by intermolecular forces (hydrogen bonds, van der Waals forces).

Bacterial cellulose to which a dispersant is bound can be obtained, for example, by culturing bacterial cellulose-producing bacteria in a medium supplemented with a dispersing agent with agitation or aeration, and removing bacterial components from the resulting culture to purify bacterial cellulose. can be obtained by A commercially available dispersant can be used. The amount of dispersant added to the medium can be, for example, a final concentration of 0.5 to 5% (w/v) in the medium. can be set. Dispersant-bound bacterial cellulose includes, for example, commercially available nanofibrillated bacterial cellulose (Fibnano (registered trademark) CM-NFBC, Fibnano (registered trademark) HE-NFBC, Fibnano (registered trademark) HP-NFBC (above, For example, at a final concentration of 0.1±0.006% (w/w), the transmittance of light having a wavelength of 500 nm in water containing bacterial cellulose becomes 35% or more. For example, if the final concentration of CMC in the medium is 0.5 to 2.0% (w / w), the final concentration is 0.1 ± 0.006% ( w/w), the transmittance of water containing bacterial cellulose at a wavelength of 500 nm can be adjusted to 35% or more.

The culture conditions for bacterial cellulose-producing bacteria can be the known culture conditions used for culturing the bacteria described above. Culture conditions for periods of 1 to 7 days can be mentioned. Also, a known medium used for culturing the bacteria described above, such as Hestrin-Schramm standard medium (HS medium), can be used.

An example of purification of bacterial cellulose from a culture solution is given below. For example, first, an aqueous solution of sodium hydroxide (NaOH) is added to the culture medium, and the mixture is heated to about 60° C. and shaken for several hours to dissolve the cells. This is subjected to centrifugation, and the supernatant is removed to remove the fungal components and collect the precipitate. Subsequently, after adding water to the precipitate and centrifuging, the operation of removing the supernatant is repeated until the pH of the precipitate becomes 7 or less. As a result, a liquid (bacterial cellulose dispersion) in which bacterial cellulose bound with a dispersing agent is dispersed in water can be obtained.

The bacterial cellulose dispersion obtained as described above (excluding the dispersing agent) has a very high cellulose purity, and analysis of its constituent sugars reveals that 90% or more is glucose. Analysis of constituent sugars can be performed, for example, by a liquid chromatography-post-column derivatization method (H. Mikami et al., 32, E207 (1983)). Table 1 shows the results of analyzing purified products of bacterial cellulose and pulp-derived cellulose by this method. Table 1 shows the ratio of each sugar as a percentage when the total amount of sugars detected is taken as 100%. In the chromatogram obtained by this method, the purified bacterial cellulose does not show any conspicuous peaks other than the glucose peak. On the other hand, in the chromatogram of purified pulp-derived cellulose, in addition to glucose, conspicuous peaks such as xylose, mannose, and cellobiose are observed, and the content of glucose is less than 90%. In this respect, a distinction can be made between purified bacterial cellulose and purified pulp-derived cellulose.

The freeze-thaw resistance improver according to the present invention can improve the freeze-thaw resistance (freeze damage resistance) of a hydraulic inorganic hardening material.

Evaluation of freeze-thaw resistance can be performed, for example, by measuring the relative dynamic modulus of elasticity according to JIS A 1148 (freeze-thaw test method for concrete) A method (freeze-thaw method in water). More specifically, for example, for the hydraulic inorganic hardening material to which the freeze-thaw resistance improver according to the present invention is added, the relative dynamic elastic modulus is measured according to the A method of JIS A 1148, and freeze-thaw cycles are performed 150 times and 300 times. etc., when the measured value increases compared to the relative dynamic elastic modulus of the hydraulic inorganic hardening material to which the freeze-thaw resistance improver is not added, it is determined that the freeze-thaw resistance is improved. can do

Freeze-thaw resistance may be evaluated, for example, by measuring the cell spacing coefficient. The bubble spacing coefficient is measured by, for example, the linear traverse method according to ASTM C 457 or the pressure method according to JIS A 1128. In general, it is said that the smaller the cell spacing coefficient, the better the freeze-thaw resistance (Noboru Sakata et al.: Consideration on the relationship between the cell structure of concrete and the resistance to frost damage, Concrete Kogaku Ronbunshu, Vol. 23, No. 1, pp. 35-47, 2012.1). For example, for the hydraulic inorganic hardened material to which the freeze-thaw resistance improver according to the present invention is added, the cell spacing coefficient is measured according to the linear traverse method according to ASTM C 457, and the hydraulic When the measured value is smaller than the cell spacing coefficient of the hardened inorganic material, it can be determined that the freeze-thaw resistance is improved.

Although not wishing to be bound by any particular theory, by adding the freeze-thaw resistance improver according to the present invention, the amount of air in the fresh state of the hydraulic inorganic hardening material increases, and the moisture freezes to increase the volume. It is thought that the freeze-thaw resistance (freeze damage resistance) can be improved because the expansion pressure is less likely to be applied to the hydraulic inorganic hardened material even if it expands.

(2. Hydraulic inorganic hardening body)
Next, the hydraulic inorganic hardened body according to the present invention will be described.

The hydraulic inorganic hardening material according to the present invention contains bacterial cellulose.

The details of the hydraulic inorganic hardened material and bacterial cellulose are the same as those described above. As the bacterial cellulose, it is preferable to use bacterial cellulose bound with a dispersant from the viewpoint of dispersibility in the hardened hydraulic inorganic material.

The bacterial cellulose fiber content may be, for example, 0.005 to 0.5% by weight relative to the hydraulic inorganic hardened material. A hydraulic inorganic hardening material containing 0.005 to 0.5% by weight of bacterial cellulose as bacterial cellulose fiber content has a higher effect of improving freeze-thaw resistance (freeze damage resistance). Since the amount of bacterial cellulose added to the hydraulic inorganic hardening material according to the present invention is smaller than that of existing AE agents, the strength of the hydraulic inorganic hardening material is effectively maintained while the freeze-thaw resistance (freezing damage resistance) is effectively improved. improvement effect is exhibited. The bacterial cellulose fiber content is, for example, 0.005-0.5% by weight, preferably 0.006-0.4% by weight, more preferably 0.007-0. .3 wt%, even more preferably 0.0075 to 0.1 wt%. The bacterial cellulose fiber content can be calculated based on the amount of bacterial cellulose added, for example, by measuring the amount of cellulose fiber of bacterial cellulose to be added using light transmittance in the same manner as described above.

(3. Manufacturing method of hydraulic inorganic hardened material)
Next, a method for producing a hydraulic inorganic hardened body according to the present invention will be described.

The method for producing a hydraulically hardened inorganic material according to the present invention includes the step of adding bacterial cellulose.

The details of the hydraulic inorganic hardened material and bacterial cellulose are the same as those described above. As the bacterial cellulose, it is preferable to use bacterial cellulose bound with a dispersant from the viewpoint of dispersibility in the hardened hydraulic inorganic material. In addition, from the viewpoint of the effect of improving freeze-thaw resistance (freezing damage resistance), the amount of bacterial cellulose added is, for example, 0.005 to 0.5% by weight of bacterial cellulose fiber content relative to the hydraulic inorganic hardening material. %, preferably 0.006 to 0.4 wt%, more preferably 0.007 to 0.3 wt%, still more preferably 0.0075 to 0.1 wt%. The bacterial cellulose fiber content can be calculated based on the amount of bacterial cellulose added, for example, by measuring the amount of cellulose fiber of bacterial cellulose to be added using light transmittance in the same manner as described above.

(4. Conclusion)
INDUSTRIAL APPLICABILITY As described above, the freeze-thaw resistance improver of the present invention contains cellulose fiber (preferably bacterial cellulose) as an active ingredient, can be used as a substitute for air entrainment agents such as AE agents, and effectively dissolves water. It is possible to improve the freeze-thaw resistance of the hard inorganic hardened material. Regarding the amount added to the hydraulic inorganic hardened material, the freeze-thaw resistance improver of the present invention can effectively exhibit the effect of improving freeze-thaw resistance with a smaller amount than existing air entrainment agents such as AE agents. Therefore, the amount of air does not become excessive, and the risk of causing a decrease in the strength of the hydraulic inorganic hardening material can be reduced, and a hydraulic inorganic hardening material excellent in freeze-thaw resistance can be obtained.

In addition, since the hydraulic inorganic hardened material of the present invention containing bacterial cellulose is excellent in freeze-thaw resistance, it can be effectively used as a material for structures in cold regions, extending the service life of structures. be able to.

EXAMPLES The present invention will be specifically described below with reference to Examples. However, the present invention is not limited to these examples.

The freeze-thaw resistance improvement effect of mortar containing bacterial cellulose nanofibers was verified.

(Material used)
A mixture of cement, fine aggregate and water was used as mortar. The cement is ordinary Portland cement (density: 3.17 g/cm ³ ), and the fine aggregate is land sand produced in Noboribetsu (surface dry density: 2.73 g/cm ³ , absolute dry density: 2.68 g/cm ³ ). , water absorption: 1.72%) was used. In this experiment, the water-cement ratio was 50%, the cement-sand ratio was 1:3, and a test piece was prepared by adding bacterial cellulose to the kneading water amount.

As the bacterial cellulose, bacterial cellulose nanofiber (hereinafter referred to as NFBC) was used. Two types of NFBC were used: a culture solution (hereinafter referred to as B) produced by fermentation using sugar or molasses as a raw material, and a purified product (hereinafter referred to as P) obtained by removing the cells and medium components from this. The appearance of B (NFBC culture solution) and P (NFBC purified product) is shown in FIG. Also, the physical properties of B and P are shown below.
・ B (NFBC culture solution)
Cellulose nanofiber produced by fermentation Culture liquid containing bacterial cells and medium components in addition to fiber Amount of fiber: 0.3 wt%
Fiber width: 20-60 nm
Fiber length: 100-500 μm
・P (NFBC purified product)
Purified product obtained by removing bacterial cells and medium components from B Fiber content: 1 wt%
Fiber width: 20-60 nm
Fiber length: 100-500 μm

A method for preparing B (NFBC culture solution) is shown below. HS medium (composition; bacto peptone 0.5% (w/v), yeast extract 0.5% (w/v), Na ₂ HPO ₄ 0.27% (w/v), citric acid 0.115% ( w/v), glucose 2% (w/v)), to which a dispersant (carboxymethylcellulose: CMC) was added to a final concentration of 2% (w/v). Gluconacetobacter intermedius SIID9587 strain, which is a bacterial cellulose-producing bacterium (accession number NITE BP-01495; 2012 (December 21, 2012, National Institute of Technology and Evaluation Patent Microorganisms Depositary Center (Chiba, Japan 292-0818) (deposited at 2-5-8 Kazusa Kamatari, Kisarazu City, Room 122)), and perform aeration stirring culture for 3 days under the conditions of aeration rate of 7 to 10 L/min, rotation speed of 200 to 500 rpm, and temperature of 30 ° C. Bacterial cellulose was produced by this, and this was designated as B (NFBC culture solution).

As P (purified NFBC), commercially available nanofibrillated bacterial cellulose (Fibnano (registered trademark) CM-NFBC, Kusano Corporation) was used.

Based on a preliminary experiment, the addition rate of B was set to 2.5% by mass relative to cement, which is the maximum addition rate that can be removed from the mold at a material age of 1 day (bacterial cellulose fiber content: 0.0075 wt%). In addition, the addition rate of P is 0.75 wt% (bacterial cellulose fiber content: 0.0075 wt%), 2.5 wt% (bacterial cellulose fiber content: 0.025 wt%), 5.0 wt% (bacterial cellulose fiber 0.05 wt%) and 10.0 wt% (bacterial cellulose fiber content: 0.1 wt%). In addition, as a control (comparative example), a similar study was also conducted on test plots to which B or P was not added (“N” in FIGS. 2 to 6). The bacterial cellulose fiber contents of B and P in FIGS. 2 to 6 are shown below.
・B2.5: 0.0075 wt%
・P0.75: 0.0075 wt%
・P2.5: 0.025 wt%
・P5.0: 0.05 wt%
・P10.0: 0.1 wt%

(flow measurement)
Flow measurement was performed according to JIS R 5201.

FIG. 2 shows the flow measurement results. When B was added, the flow increased. On the other hand, when P was added, the flow decreased as the addition rate increased. This may be due to the fact that the cement paste was constrained by the fibers in P. In previous research, it has been reported that the fluidity decreased due to the mixing of polypropylene short fibers and steel fibers (Concrete Engineering Annual Papers, Vol.39, No.1, pp.265-270, 2017.6 Proceedings of the Society of Agriculture and Rural Engineering, No.308(87-1), pp.I_117-I_122, 2019.6; Proceedings of the Japan Society of Civil Engineers, Vol.296, pp.111-119, 1980.4), other fibers Similarly, it was confirmed that the addition of P also lowered the fluidity. The reason why the flow increased due to the addition of B is that unlike P, it contains impurities such as bacterial cells and medium components. is unknown.

(Measurement of air volume)
The amount of air was measured according to JIS A 1128.

FIG. 3 shows the measurement results of the fresh air amount. When fresh, the addition of B and P increased the amount of air compared to the no NFBC added control (N). On the other hand, no difference in the amount of air due to the difference in the added amount of P was observed.

(Measurement of bubble spacing coefficient)
The bubble spacing factor was measured according to the linear traverse method of ASTM C 457. In addition, the test specimen was a 40 × 40 × 160 mm prism specimen after curing in water at 20 ° C. for 4 weeks, cut into 40 × 40 × 10 mm, and the cut surface was # 80, # 320, # 1000, # 1500 polishing sand and cleaned with an ultrasonic cleaner.

FIG. 4 shows the measurement results of the bubble spacing coefficient by the linear traverse method. It was confirmed that the addition of B and P reduces the cell spacing coefficient. From this, it is considered that the addition of B and P may improve the cell structure.

(Freeze-thaw test)
A prismatic specimen of 40×40×160 mm was cured in water at 20° C. for 4 weeks, and then measured for relative dynamic elastic modulus in accordance with A method of JIS A1148.

FIG. 5 shows the relationship between the relative dynamic modulus of elasticity and the number of freeze-thaw cycles. In the control (N) to which NFBC was not added, the relative dynamic modulus of elasticity fell below 60% at around 50 cycles of freezing and thawing, suggesting that the mortar had extremely low frost damage resistance. On the other hand, when B and P were used, the relative dynamic modulus of elasticity was maintained at 60% or more even when the number of freeze-thaw cycles exceeded 150 cycles, and deterioration due to freeze-thaw was suppressed. It was thought that the factors for the freeze-thaw resistance-improving effect of B and P were that the amount of air increased due to the addition of B and P, and the cell spacing coefficient decreased (generally, the smaller the cell spacing coefficient, the Excellent frost resistance (Concrete Kogaku Ronbunshu, Vol.23, No.1, pp.35-47, 2012.1)).

FIG. 6 shows the relationship between the relative dynamic modulus of elasticity of P10.0 (bacterial cellulose fiber content: 0.1 wt %) and the number of times of freezing and thawing. In the control (N) to which NFBC was not added, the relative dynamic modulus of elasticity fell below 40% at around 50 cycles of freezing and thawing, suggesting that the mortar had extremely low frost damage resistance. On the other hand, when P10.0 was used, the relative dynamic modulus of elasticity was maintained at 60% or more even when the number of freezing and thawing cycles exceeded 200 cycles, and deterioration due to freezing and thawing was remarkably suppressed.

As described above, the mortar of this example containing bacterial cellulose nanofibers has a small cell spacing coefficient, and even when the number of freeze-thaw cycles exceeds 150 cycles, the relative dynamic elastic coefficient is maintained at 60% or more. It was shown to be excellent in resistance (freezing damage resistance).

Claims (7)

A freeze-thaw resistance improver for a hydraulic inorganic hardening material containing cellulose fibers as an active ingredient. The cellulose fiber is bacterial cellulose,
The freeze-thaw resistance improver according to claim 1, characterized in that: The bacterial cellulose fiber content is 0.005 to 0.5% by weight with respect to the hydraulic inorganic hardened material.
The freeze-thaw resistance improver according to claim 2, characterized in that: A hydraulic inorganic hardening material containing bacterial cellulose. The bacterial cellulose fiber content is 0.005 to 0.5% by weight with respect to the hydraulic inorganic hardened material.
5. The hydraulic inorganic hardening body according to claim 4, characterized in that: A method for producing a hydraulic inorganic hardened body, comprising the step of adding bacterial cellulose. The amount of the bacterial cellulose added is 0.005 to 0.5% by weight of the bacterial cellulose fiber content relative to the hydraulic inorganic hardened material.
The method for producing a hydraulic inorganic hardened body according to claim 6, characterized in that:

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