Mortar or concrete, and structure using the same

Abstract

To provide mortar or concrete capable of exhibiting superior chemical stability and ensuring long-lasting antibacterial effect, and a structure using the same.SOLUTION: Mortar or concrete 2a comprises cement and aggregate, and further comprises a composite oxide ceramic containing a rare-earth element and at least one element selected from molybdenum, tungsten, and vanadium.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to mortar or concrete containing an antibacterial agent, and a structure using the same. [Background technology]

[0002] In recent years, corrosion and deterioration of concrete has become a problem in water treatment facilities such as water supply and sewerage systems. The cause of this is thought to be that anaerobic sulfate-reducing bacteria and sulfur-oxidizing bacteria present in sewage and sewage sludge produce sulfuric acid, which chemically reacts with concrete, causing it to deteriorate. In addition, hydrogen sulfide is also produced during the concrete corrosion process, further deteriorating the concrete. Therefore, a technology has been developed in which concrete contains compounds such as Ag (silver) and Cu (copper), which are antibacterial and antiviral materials (Patent Document 1).

[0003] Meanwhile, in addition to the above-mentioned Ag (silver), Cu (copper), and photocatalysts, composite oxide ceramics that combine water-repellent properties with antibacterial and antiviral properties have been developed as antibacterial and antiviral materials (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-175772 [Patent Document 2] International Publication No. W202O / 017493 Summary of the Invention [Problem to be solved by the invention]

[0005] However, antibacterial agents made of silver or copper are not chemically stable, particularly against hydrogen sulfide, and sulfurization with H2S reduces the amount of elution, potentially reducing the antibacterial effect. Also, photocatalysts such as tungsten trioxide do not provide antibacterial effects in dark places such as inside sewer pipes.

[0006] Therefore, an object of the present invention is to provide mortar or concrete that has excellent chemical stability and has a long-lasting antibacterial effect, and a structure using the same. [Means for solving the problem]

[0007] In order to solve the above problems, the mortar or concrete of the present invention is a mortar or concrete containing cement and aggregate, and further containing a composite oxide ceramic containing a rare earth element and at least one element selected from molybdenum, tungsten, and vanadium.

[0008] This mortar or concrete has excellent chemical stability of the antibacterial composite oxide ceramics, and therefore the antibacterial effect lasts for a long period of time.

[0009] In the mortar or concrete of the present invention, the content of the composite oxide ceramic in the mortar or concrete may be 0.1 mass % or more. This mortar or concrete can exert antibacterial effects while ensuring the strength of the mortar or concrete.

[0010] In the mortar or concrete of the present invention, the rare earth element may be at least one selected from La, Ce, and Gd.

[0011] In the mortar or concrete of the present invention, the composite oxide ceramics (La 2-x Ce x )(Mo 2-y W y )O9 (where x=0 to 2, y=0 to 2).

[0012] In the mortar or concrete of the present invention, the composite oxide ceramics is La2(Mo 2-y W y)O9 (where y=0 to 2). In the mortar or concrete of the present invention, the composite oxide ceramic may be represented by La2Mo2O9. In the mortar or concrete of the present invention, the composite oxide ceramic may be represented by La2MoWO9.

[0013] The structure of the present invention is characterized by having the above-mentioned mortar or concrete on its surface. The structure of the present invention may be in the form of a pipe and have the mortar or concrete on its inner surface. [Effects of the Invention]

[0014] According to the present invention, it is possible to obtain mortar or concrete having a long-lasting antibacterial effect, and a structure using the same. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional perspective view of a structure according to an embodiment of the present invention. [Figure 2] FIG. 1 is a flowchart showing an example of manufacturing a composite oxide ceramic by a complex polymerization method. [Figure 3] FIG. 1 is a flowchart showing an example of manufacturing composite oxide ceramics by a precipitation method. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a cross-sectional perspective view of a structure 10 according to an embodiment of the present invention. In this example, the structure 10 is a cylindrical sewer pipe, and is made up of a main body 2b made of a known reinforced concrete pipe and mortar or concrete (mortar in this example) 2a provided on the inner surface of the main body 2b. In this example, in order to repair the corroded inner surface of the main body 2b, which is an existing sewer pipe, a composition that will become mortar 2a is applied to the inner surface of the main body 2b later. However, for example, when manufacturing a new structure 10, the main body 2b forming the outer shell can be manufactured first using a centrifugal method or the like, and then a composition that will become concrete 2a can be poured into the inner surface of the main body 2b using a centrifugal method or the like, and molded to manufacture the entire structure. That is, when the structure 10 is newly manufactured, it is preferable to use the concrete 2a, and when applying it to the main body 2b of the structure 10 later, it is preferable to use the mortar 2a, which is easy to work with.

[0017] Next, the mortar or concrete 2a will be described. The mortar or concrete 2a contains cement and aggregate, and further contains composite oxide ceramics containing a rare earth element and at least one element selected from molybdenum, tungsten, and vanadium. In the present invention, "antibacterial" is not limited to reducing or killing bacteria, but also includes "antiviral."

[0018] The cement may be any known cement such as ordinary Portland cement as specified in JIS-R5210, other Portland cement, blast furnace cement, etc., but is not limited to these. Two or more types of cement may also be used in combination. It goes without saying that the mortar or concrete 2a is a hardened composition (ready-mixed concrete) containing the above-mentioned cement, aggregate, and composite oxide ceramics, as well as water to harden (hydrate) the cement (hydraulic). In this composition, the ratio of water to cement (water-cement ratio) may be appropriately set so as to ensure strength and fluidity, and is not particularly limited, but can be, for example, 10 to 90 mass %, more preferably 20 to 60 mass %.

[0019] Known aggregates can be used. For example, in the case of mortar 2a, sand, which is a fine aggregate, can be used. In the case of concrete 2a, a mixture of sand, which is a fine aggregate, and gravel (crushed stone), which is a coarse aggregate, can be used. Note that fine aggregate is, for example, 5 mm or less in diameter, and coarse aggregate is, for example, greater than 5 mm in diameter.

[0020] The mixing ratio of cement and aggregate can be appropriately determined depending on the desired strength, and can be a known ratio. For example, the mass ratio can be 1 part cement to 2 to 3 parts fine aggregate and 4 to 6 parts coarse aggregate, but is not limited to these.

[0021] The mortar or concrete 2a may contain other components, such as chemical admixtures such as a water-reducing agent and a thickener.

[0022] The composite oxide ceramics that can be used are essentially the composite oxide ceramics described in the above-mentioned Patent Document 2 (International Publication No. W2020 / 017493). The composite oxide ceramics have excellent chemical stability, and do not undergo chemical changes, particularly when exposed to hydrogen sulfide, so that the antibacterial effect lasts for a long period of time. Furthermore, when composite oxide ceramics exert their antibacterial properties, they do not generate active oxygen, which causes concrete deterioration, and therefore concrete deterioration can be suppressed.

[0023] As described above, according to the present invention, mortar or concrete having excellent chemical stability and having a long-lasting antibacterial effect can be obtained.

[0024] The content of the composite oxide ceramic in the mortar or concrete is preferably 0.1 mass % or more, more preferably 0.5 to 10 mass %, and even more preferably 1.0 to 5.0 mass %. If the content of the composite oxide ceramic is less than 0.1% by mass, the antibacterial effect may be insufficient, whereas if the content of the composite oxide ceramic is more than 10% by mass, the curing time may be delayed and the strength may be reduced.

[0025] The composite oxide ceramic contains at least the above elements, and usually further contains oxygen atoms, and may further contain other elements as long as the effects are not impaired. Each component of such composite oxide ceramic will be described below.

[0026] The composite oxide ceramic of this embodiment contains a rare earth element. The rare earth element is usually contained as an oxide. In this embodiment, the rare earth element is a collective term for Sc (scandium), Y (yttrium), and lanthanoids (elements with atomic numbers 57 to 71), and these elements can be used alone or in combination of two or more. In this embodiment, from the viewpoint of water repellency, it is preferable that the rare earth element contains a lanthanoid, and it is more preferable that the rare earth element contains at least one selected from La (lanthanum), Ce (cerium), and Gd (gadolinium). Furthermore, from the viewpoint of antibacterial and antiviral properties, it is preferable to contain La and Ce as rare earth elements, and it is particularly preferable to contain La. The combination of La and Mo provides excellent antibacterial and antiviral properties.

[0027] The composite oxide ceramic of this embodiment also contains at least one element selected from Mo (molybdenum), W (tungsten), and V (vanadium), which are usually contained as oxides. The composite oxide ceramic of this embodiment has antibacterial and antiviral properties due to the inclusion of at least one selected from molybdates, tungstates, and vanadates.

[0028] In this embodiment, the content ratio of the rare earth element (element A) to at least one element selected from Mo, W, and V (element B) is not particularly limited, and may be adjusted appropriately depending on the application. In order to achieve both water repellency and antibacterial and antiviral properties, the molar ratio of element A to element B is preferably in the range of 1:9 to 9:1, more preferably 3:7 to 7:3, and particularly preferably 1:1.

[0029] A preferred embodiment of the composite oxide ceramic is (La 2-x Ce x )(Mo 2-y W y )O9, where x=0-2 and y=0-2. A further preferred embodiment of the composite oxide ceramic is La2(Mo 2-y W y )O9, where y=0-2. For example, the composite oxide ceramic of this embodiment may be La2Mo2O9, La2W2O9, La2(Mo 0.5 W 1.5 )O9, La2MoWO9, La2(Mo 1.5 W 0.5 )O9, La 1.8 Ce 0.2 It has a chemical composition such as Mo2O9.

[0030] The composite oxide ceramic of this embodiment may further contain other elements to the extent that the effect is not impaired. Examples of other elements include transition metal elements. The transition metal elements may be contained as oxides or in other forms without forming oxides. In this embodiment, the content of the other elements is preferably 20 mass % or less, more preferably 10 mass % or less, and even more preferably 5 mass % or less, based on the total amount of the composite oxide ceramic containing the other elements.

[0031] The composite oxide ceramic of this embodiment may be crystalline, such as a single crystal or polycrystal, or amorphous, such as glassy, ​​or may be a combination of crystalline and amorphous parts. The crystalline phase may be a single phase, or a combination of two or more different phases.

[0032] The method for producing the composite oxide ceramic of this embodiment is not particularly limited, and the composite oxide ceramic can be obtained by forming a composite oxide containing a rare earth element and at least one element selected from molybdenum, tungsten, and vanadium, and firing the composite oxide. Suitable production methods include the complex polymerization method and precipitation method described below, but the solid-state reaction method and other production methods described below may also be used. The complex polymerization method, precipitation method, and solid-state reaction method will be described below.

[0033] <Complex polymerization> The complex polymerization method will be described with reference to Fig. 2. Fig. 2 is a flowchart showing an example of the complex polymerization method. In the following, as an example, a case where molybdenum is used as at least one element selected from molybdenum, tungsten, and vanadium will be described.

[0034] The complex polymerization method of the present embodiment includes a gelation step (S1) of adding an oxycarboxylic acid and a glycol to an aqueous solution containing a rare earth-containing compound and a molybdenum-containing compound, and then heating the solution to cause an ester reaction between the oxycarboxylic acid and the glycol to form a gel; a drying step (S2) of drying the gel obtained in the gelling step; A calcination step (S3) of calcining the powder obtained by drying the gel; a molding step (S4) of molding the powder after the calcination; and a firing step (S5) of firing the molded body after the molding. The complex polymerization method has the advantage that it is possible to obtain a composite oxide ceramic with excellent uniformity and high density at a relatively low temperature.

[0035] In the gelation step (S1), water is first added to a water-soluble rare earth-containing compound and a molybdenum-containing compound, and the resulting mixture is mixed to form an aqueous solution (S11). Next, an oxycarboxylic acid is added to the aqueous solution to form a metal-oxycarboxylic acid complex (S12). Glycol is then added (S13), and the oxycarboxylic acid and glycol undergo an esterification reaction to form a gel (S14).

[0036] Examples of rare earth-containing compounds that are soluble in water include rare earth nitrates. Examples of molybdenum-containing compounds that are soluble in water include ammonium molybdate. For example, lanthanum nitrate hexahydrate (La(NO3)3·6H2O) is used as the rare earth-containing compound, and ammonium molybdate tetrahydrate ((NH4)6Mo7O) is used as the molybdenum-containing compound. 24 4H2O) can be used.

[0037] Examples of the hydroxycarboxylic acid include citric acid, and examples of the glycol include ethylene glycol and propylene glycol.

[0038] The obtained gel is thoroughly dried in a drying step (S2). The drying method is not particularly limited, but heat drying is preferred. Next, the powder obtained by drying the gel is calcined (calcination step: S3). Although not particularly limited, calcination is preferably carried out at 500°C or higher. The atmosphere in which calcination is carried out is not particularly limited, and it can be carried out in air, for example. The obtained powder may be partially sintered, so it may be pulverized to a fine powder if necessary. Although not particularly limited, dry pulverization is preferred. The type of pulverizer is not particularly limited, and can be appropriately selected from known types.

[0039] Next, the obtained calcined powder (calcined powder) is molded into a desired shape (molding step: S4). The molding method is not particularly limited, and can be appropriately selected from known molding methods such as uniaxial pressing. Next, the resulting molded body is fired to obtain a sintered body of the composite oxide ceramic (firing step: S5). The firing method is not particularly limited, but a suitable example is a method in which the molded body is heated in the atmosphere at about 900°C.

[0040] <Sedimentation method> Next, a precipitation method will be described as another method for producing composite oxide ceramics. Fig. 3 is a flowchart showing an example of the precipitation method. In the following, as an example, a case where molybdenum is used as at least one element selected from molybdenum, tungsten, and vanadium will be described.

[0041] The precipitation method in this embodiment includes a step (S21) of stirring and mixing aqueous solutions containing a rare earth-containing compound and a molybdenum-containing compound, and then heating the mixture to react with each other to obtain an intermediate substance (S22); a drying step (S23) of drying the obtained intermediate material; A calcination step (S24) of calcining the powder obtained by the drying; a molding step (S25) of molding the powder after the calcination; and a firing step (S26) of firing the molded body after the molding. The precipitation method has the advantage that it is possible to obtain a composite oxide ceramic with excellent uniformity and high density at a relatively low temperature.

[0042] Specifically, a water-soluble rare earth-containing compound is first dissolved in distilled water to prepare a rare earth-containing aqueous solution. A water-soluble molybdenum-containing compound is then dissolved in distilled water to prepare a molybdenum-containing aqueous solution. These aqueous solutions are then mixed and stirred at room temperature (S21). The mixed aqueous solution is then heated for a predetermined time (S22) to obtain an intermediate substance.

[0043] Examples of rare earth-containing compounds that are soluble in water include rare earth nitrates. Examples of molybdenum-containing compounds that are soluble in water include ammonium molybdate. For example, lanthanum nitrate hexahydrate (La(NO3)3·6H2O) is used as the rare earth-containing compound, and ammonium molybdate tetrahydrate ((NH4)6Mo7O) is used as the molybdenum-containing compound. 24 4H2O) can be used.

[0044] The obtained intermediate substance is thoroughly dried in a drying step (S23). The drying method is not particularly limited, but heat drying is preferred. Next, the dried intermediate substance (powder) is calcined to obtain a calcined powder (calcination step: S24). Although not particularly limited, calcination is preferably carried out at 500°C or higher. The atmosphere in which the calcination is carried out is not particularly limited, and the calcination can be carried out, for example, in air.

[0045] The obtained powder may be partially sintered, so it may be pulverized to a fine powder as needed. The pulverization method is not particularly limited, but dry pulverization is preferred. The type of pulverizer is not particularly limited, and can be appropriately selected from known types. Next, the obtained calcined powder (calcined powder) is molded into a desired shape (molding step: S25). The molding method is not particularly limited, and can be appropriately selected from known molding methods such as uniaxial pressing.

[0046] Next, the resulting molded body is fired to obtain a sintered body of the composite oxide ceramic (firing step: S26). The firing method is not particularly limited, but a suitable example is a method in which the molded body is heated in air at about 900°C.

[0047] <Solid-state reaction method> Next, we will explain the solid-state reaction method, another method for producing composite oxide ceramics. The solid-state reaction method involves mixing powder of a rare-earth-containing compound as raw materials with powder of molybdenum oxide (MoO3) and calcining the mixture to obtain a calcined powder. As the raw material rare-earth-containing compound, a rare-earth oxide such as lanthanum oxide (La2O3) can be used. Molybdenum oxide can be obtained, for example, by thermally decomposing powder of ammonium molybdate. The rare earth-containing compound and molybdenum oxide are mixed in a ball mill for 24 hours, and then calcined at, for example, 900°C or higher to obtain the desired single-phase composite oxide ceramic powder. The atmosphere for calcining and firing can be the same as that for the complex polymerization method. The molding method can also be the same as that for the complex polymerization method, and therefore a description thereof will be omitted here.

[0048] Next, in the firing step, the obtained molded body is fired to obtain a sintered body of the composite oxide ceramic. The firing method is not particularly limited, but a suitable example is a method in which the compact is heated in air at about 1200°C.

[0049] Powder is produced using such composite oxide ceramics. For example, the sintered body sintered by the above-mentioned production method can be pulverized and, if necessary, classified to obtain powdery (granular) composite oxide ceramic particles. These composite oxide ceramic particles are then mixed with a composition consisting of cement, water, and aggregate, and hardened (hydrated) to produce mortar or concrete. The particle size of the composite oxide ceramic particles can be, for example, a calculated particle size of 10 to 1000 nm. Here, the calculated particle size d = 6(ρ × S), where ρ is the particle density (g / m 3 ), S:BET specific surface area (m 2 / g), which is an approximate spherical particle size. The BET specific surface area can be measured according to JIS-R1626 (1996). Particle density can be measured according to JIS-A1202 (2020).

[0050] Composite oxide ceramics exert an antibacterial effect by coming into physical contact with bacteria, deactivating them. This is thought to be because the rare earth elements on the surface of the composite oxide ceramics adsorb and inactivate negatively charged bacteria (Nakamura Kiminori et al., Journal of Intestinal Microbiology (2019)).

[0051] It goes without saying that the present invention is not limited to the above-described embodiments, but covers various modifications and equivalents that fall within the spirit and scope of the present invention. The shape of the structure is not limited. [Example]

[0052] <Production of composite oxide ceramic powder> LMWO (La2MoWO9) powder was produced as a composite oxide ceramic.

[0053] The BET specific surface area of ​​the obtained powder was 48.6 m 2 / g, with a calculated particle size of 24 nm. <Antibacterial activity value> The antibacterial activity of the composite oxide ceramic powder after 24 hours was evaluated as follows. 1.8 mg of the composite oxide ceramic powder was weighed and dispersed in an ethanol solution, which was then applied to one side of a glass plate and dried at 100°C. A test bacterial solution (Escherichia coli) was dissolved in 1 / 500 NB solution (medium) and 5.0 × 10 5 CFU / mL) was dropped onto the plate, and a 40mm x 40mm film was placed over it, followed by incubation at 35°C for 24 hours. The film was then removed, and the glass surface was washed with SCDLP medium solution. This solution was then diluted with BS (phosphate buffered saline) solution, and added and mixed with NA (Nutrient Agar) medium. Bacterial colonies were formed by culturing at 35°C for 48 hours. Next, the number of colonies on the NA medium was counted, and the resulting number of colonies was taken as the number of surviving bacteria (N). An activity value of 2 or more can be determined to have antibacterial activity. The results obtained are shown in Table 1.

[0054] [Table 1]

[0055] As is clear from Table 1, after 24 hours, the number of viable bacteria had decreased to below the lower limit of measurement, demonstrating that the composite oxide ceramic particles have antibacterial activity.

[0056] <Mortar manufacturing> Cement (Portland cement), water, aggregate (sand), and the above composite oxide ceramic (LMWO) powder were mixed in the proportions shown in Table 2, formed into plates, and then hardened (hydrated) to obtain plate-shaped mortar. When the content of the composite oxide ceramics in the mortar was 1.0 mass % and 5.0 mass %, respectively, mortar free from cracks was obtained.

[0057] [Table 2] [Explanation of symbols]

[0058] 2a Mortar or concrete 10 Structure

Claims

1. A mortar or concrete containing cement and aggregate, The mortar or concrete further comprises a composite oxide ceramic containing a rare earth element and at least one element selected from molybdenum, tungsten, and vanadium.

2. 2. The mortar or concrete according to claim 1, wherein the content of said composite oxide ceramics in said mortar or concrete is 0.1 mass % or more.

3. 3. The mortar or concrete according to claim 1, wherein the rare earth element is at least one selected from the group consisting of La, Ce, and Gd.

4. The composite oxide ceramics (La ２－ｘ Ce ｘ ) (Mo ２－ｙ W ｙ ) O ９ The mortar or concrete according to claim 1 or 2, characterized in that it is represented by (where x = 0 to 2, y = 0 to 2).

5. The composite oxide ceramic is La ２ (Mo ２－ｙ W ｙ ) O ９ The mortar or concrete according to claim 1 or 2, characterized in that it is represented by (where y = 0 to 2).

6. The composite oxide ceramic is La ２ Mo ２ O ９ 5. The mortar or concrete according to claim 4, characterized in that it is represented by the formula:

7. The composite oxide ceramic is La ２ MoWO ９ 5. The mortar or concrete according to claim 4, characterized in that it is represented by the formula:

8. A structure having the mortar or concrete according to claim 1 or 2 on at least its surface.

9. 9. The structure according to claim 8, which is in the shape of a pipe and has the mortar or concrete on its inner surface.

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