Admixtures for cement, cement compositions, hardened cement products, and methods for manufacturing hardened cement products.

Abstract

To provide an admixture that can impart crack self-healing properties and resistance to sulfuric acid degradation to cement-based materials, a cement composition containing this admixture, a hardened product thereof, and a method for manufacturing cement-based materials using the admixture. [Solution] The present invention provides a cement admixture that contains microorganisms that generate carbon dioxide through metabolism and a growth inhibitor for bacteria with sulfur-oxidizing ability, and does not contain blast furnace slag fine powder. According to the present invention, corrosion of hardened cement can be suppressed even in the presence of sulfuric acid-producing microorganisms, such as in sewage treatment facilities, and even if cracks occur, the cracks can self-repair. The present invention also provides a cement composition, a hardened cement, and a method for producing a hardened cement.

Description

Technical Field

[0001] The present invention relates to a cement admixture, a cement composition, a cement hardened body, and a method for producing a cement hardened body. In particular, it relates to a cement admixture, a cement composition, a cement hardened body, and a method for producing a cement hardened body, which contain microorganisms that generate carbon dioxide through metabolism and are added to cement to impart self-repair ability to the cement hardened body.

Background Art

[0002] Hardened products of cement such as concrete and mortar crack over time. When water and oxygen penetrate thereinto, rusting occurs on the surface of the reinforcing bars, and the concrete on the surface of the reinforcing bars peels off due to this rusting, resulting in symptoms of deterioration. Patent Document 1 discloses a cement-based material containing a repair agent that utilizes the power of microorganisms to repair such cracks.

[0003] Further, Patent Document 2 discloses that by applying a bacterial material, a silicate, a calcium salt, and a liquid nutrient for bacteria to the surface of concrete having cavities such as cracks, a gel is formed in the cracks to assist in the bio-based repair of the cracks.

[0004] Regarding the deterioration of hardened products of cement other than cracks, for example, in concrete structures such as sewer pipes used in sewers such as sewer facilities, there is a problem that concrete is corroded early by sulfuric acid produced by sulfur-oxidizing bacteria.

[0005] Patent Documents 3, 4, and 5 disclose adding a growth inhibitor that inhibits the activity of microorganisms (sulfur-oxidizing bacteria) that generate sulfuric acid to a cement composition. According to this, it is possible to suppress the corrosion of hardened cement products such as concrete even in the presence of microorganisms that generate sulfuric acid.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] According to the cement-based material of Patent Document 1, cracks that occur in concrete over time can be self-repaired, and if the liquid of Patent Document 2 is applied to the cracked area of ​​the concrete, the bio-based repair of the crack is assisted.

[0008] According to the growth inhibitors for sulfur-oxidizing bacteria described in Patent Documents 3, 4, and 5, as mentioned above, corrosion of hardened cement can be suppressed even in the presence of sulfuric acid-producing microorganisms, such as in sewage treatment facilities.

[0009] However, while technologies existed to address the challenges of concrete self-healing and sulfuric acid resistance, no technology existed that combined both. Therefore, in order to produce a concrete composition that possesses both self-healing and sulfuric acid resistance, the inventors added a commercially available sulfur-oxidizing bacteria growth inhibitor to a commercially available concrete composition containing a microbial agent with crack self-healing properties and prepared concrete. However, they were unable to confirm the self-healing ability of the resulting concrete. One possible reason for this is that the commercially available sulfur-oxidizing bacteria growth inhibitor may have affected the activity of the microorganisms in the microbial agent, but the direct cause has not yet been clarified.

[0010] In view of the above-mentioned problems, the object of the present invention is to provide an admixture that can impart crack self-healing properties and resistance to sulfuric acid degradation to cement-based materials, a cement composition containing this admixture, a hardened body thereof, and a method for manufacturing cement-based materials using the admixture. [Means for solving the problem]

[0011] The inventors diligently conducted studies to achieve the above objective. As a result, they discovered that the inhibition of the activity of the microorganism responsible for self-repair by the sulfur-oxidizing bacteria growth inhibitor was not due to the growth inhibitor itself, but rather to the blast furnace slag fine powder contained in the growth inhibitor as a diluent. They found that by not including the blast furnace slag fine powder in the admixture of the microorganism and the growth inhibitor, the activity of the microorganism responsible for self-repair could be maintained even in the presence of the growth inhibitor, thus completing the present invention.

[0012] In other words, the invention described in claim 1 for achieving the above objective is a cement admixture comprising a microorganism that generates carbon dioxide through metabolism and a growth inhibitor of bacteria having sulfur-oxidizing ability, characterized in that it does not contain blast furnace slag fine powder.

[0013] According to this invention, since the cement admixture does not contain blast furnace slag fine powder, the activity of microorganisms that generate carbon dioxide through metabolism by blast furnace slag fine powder is not inhibited. Therefore, when mixed into a cement composition, a hardened cement body can be obtained that possesses both self-healing properties for cracks and resistance to sulfuric acid degradation.

[0014] Furthermore, it is preferable that the microorganisms that produce carbon dioxide through metabolism are selected from the group consisting of the genera Planococcus, Bacillus, and Sporosarcina.

[0015] Furthermore, it is preferable that the bacterial growth inhibitor having sulfur-oxidizing ability is selected from the group consisting of nickel and nickel compounds, tungsten and tungsten compounds, dicarboxylic acid compounds, hydroxy acid compounds, and mixtures thereof.

[0016] Moreover, it is preferable that the poly lactic acid is included as a nutrient source for the microorganisms that generate carbon dioxide by metabolism.

[0017] The above object can also be achieved by a cement composition including the admixture for cement of the present invention and cement, and a hardened cement body.

[0018] Furthermore, the above object can also be achieved by a manufacturing method of a hardened cement body, including: an admixing step of admixing a cement composition including an inhibitor for growth of microorganisms that generate carbon dioxide by metabolism and bacteria having sulfur oxidizing ability; and a hardening step of hardening the cement composition to obtain a hardened body thereof.

Advantages of the Invention

[0019] According to the present invention, since the admixture for cement does not include fine powder of blast furnace slag, the activity of microorganisms that generate carbon dioxide by metabolism due to the blast furnace slag fine powder is not inhibited. Therefore, when admixed to a cement composition, a hardened cement body having both self - healing property for cracks and resistance to sulfate deterioration can be obtained.

[0020] Therefore, corrosion of the hardened cement body can be suppressed even in the presence of microorganisms that generate sulfuric acid, such as in sewer facilities, and even when cracks occur, the cracks can be self - healed. Thus, the maintenance management cost and labor of the hardened cement body can be reduced, and the product life of the hardened cement body is prolonged, so that the life - cycle cost including the manufacture and maintenance management of the hardened cement body can also be reduced.

[0021] In addition, the prolongation of the product life of the hardened cement body may simultaneously bring an effect of reducing the environmental load.

Brief Description of the Drawings

[0022] [Figure 1] It is a flowchart showing a manufacturing method of a hardened cement body of the present invention. [Figure 2] This bar graph shows the results of the microorganism inhibitory effect test conducted using a bacterial growth inhibitor with sulfur oxidation ability, as described in the example. [Figure 3] This is a schematic diagram showing the formwork for forming the cement hardened body used in the water leakage test of the example. [Figure 4] This is a schematic diagram showing compression testing machine B for obtaining crack samples of hardened cement used in the water leakage test of the example. [Figure 5] This is a schematic diagram illustrating the water leakage test in the example. [Figure 6] This graph shows the results of the water leakage test in the example. [Figure 7] This graph shows the results of the water leakage test for the comparative example. [Modes for carrying out the invention]

[0023] <Cement admixture> The cement admixture of the present invention comprises microorganisms that generate carbon dioxide through metabolism and a growth inhibitor of bacteria having sulfur-oxidizing ability.

[0024] [Microorganisms that produce carbon dioxide through metabolism] Microorganisms that produce carbon dioxide through metabolism are those that metabolize nutrients directly or indirectly to generate carbon dioxide. These microorganisms metabolize organic carbon sources, described later, in the presence or absence of oxygen, to produce carbon dioxide.

[0025] The mechanism by which these microorganisms self-repair cement is as follows: carbon dioxide reacts with water to generate carbonate ions, which then react with calcium ions derived from calcium hydroxide in the hardened cement to precipitate calcium carbonate, filling cracks in the cement.

[0026] As for the microorganisms, one or more species can be selected from obligate (absolute) anaerobic microorganisms, facultative anaerobic microorganisms, obligate aerobic microorganisms, and microaerophilic microorganisms. However, from the viewpoint of consuming oxygen within the cement hardened body, as described later, and preventing corrosion of the steel embedded in the hardened body, facultative anaerobic microorganisms, obligate aerobic microorganisms, and microaerophilic microorganisms are preferred, with obligate aerobic microorganisms being particularly preferred. Furthermore, from the viewpoint of oxygen consumption, it is preferable that the microorganisms be selected from the group consisting of the genera Planococcus, Bacillus, and Sporosarcina.

[0027] Species of the genus Planococcus include, for example, Planococcus alkanoclasticus, Planococcus anarcticus, Planococcus chinensis, Planococcus citreus, Planococcus columbae, Planococcus donghaensis, Planococcus faecalis, Planococcus glaciei, Planococcus halocryophilus, Planococcus halotolerans, Planococcus kocurii, Planococcus koreensis, Planococcus maitriensis, Planococcus maritimus, Planococcus mcmeekinii, Planococcus okeanokoites, Planococcus plakortidis, Planococcus psychrophilus, Planococcus rifietoensis, Planococcus ruber, Planococcus salinarum, Planococcus Examples include salinus, Planococcus stackebrandtii, and Planococcus versustus.

[0028] Bacillus strains and strains of B. acidicel、B. acidicola、B. acidproducens、B. acidocaldarius、B. acidoterrestrial、B. aeolius、B. aerius、B. aerophilus、B. agaradhaerens、B. agri、B. aidingensis、B. akibai、B. alkalophilus、B. algicola、B. alginolyticus、B. alkalidiazotrophicus、B. alkalinitrilecus、B. alkalisediminis、B. alkalitelluris、B. altitudinis、B. alveayuensis、B. alvei、B. amyloliquefaciens、B. amylolyticus、B. andresenii、B. aneurinilyticus、B. anthracis、B. aquimaris、B. arenosis、B. arsenicselenatis、B. arsenicus、B. aurantiacus、B. arvi、B. aryabhattai、B. asahii、B. atrophaeus、B. axarquiensis、B. nitrogen fixans、B. azotoformans、B. badius、B. barbaricus、B. bataviensis、B. beijingensis、B. benzoevorans、B. beringensis、B. berkeley、B. beveridgei、B. bogoriensis、B. boroniphilus、B. borstelensis、B. brevis Migula、B. butanolivorans、B. canavelius、B. carboniphilus、B. cecembensis、B. cellulosilyticus、B. centrosporus、B. cereus、B. chagannorensis、B. chitinolyticus、B. chondroitinus、B. choshinensis、B. chungangensis、B. cibi、B.circulans, B. clarkii, B. clausii, B. coagulans, B. coahuilensis, B. cohnii, B. composti, B. curdlanolyticus, B. cycloheptanicus, B. cytotoxicus, B. daliensis, B. decisifrondis, B. decolorationis, B. deserti, B. dipsosauri, B. drentensis, B. edaphicus, B. ehimensis, B. eiseniae, B. enclensis, B. endophyticus, B. endoradicis, B. farraginis, B. fastidiosus, B. fengqiuensis, B. firmus, B. flexus, B. foraminis, B. fordii, B. formosus, B. fortis, B. fumarioli, B. funiculus, B. fusiformis, B. galactophilus, B. galactosidilyticus, B. galliciensis, B. gelatini, B. gibsonii, B. ginsengi, B. ginsengihumi, B. ginsengisoli, B. globisporus, B. glucanolyticus, B. gordonae, B. gottheilii, B. graminis, B. halmapalus, B. haloalkaliphilus, B. halochares, B. halodenitrificans, B. halodurans, B. halophilus, B. halosaccharovorans, B. hemicellulosilyticus, B. hemicentroti, B. herbersteinensis, B. horikoshii, B. horneckiae, B. horti, B. huizhouensis, B. humi, B. hwajinpoensis, B. idriensis, B. indicus, B. infantis, B. infernus, B. insolitus, B. invictae, B. iranensis, B.isabeliae, B. isronensis, B. jeotgali, B. kaustophilus, B. kobensis, B. kochii, B. kokeshiiformis, B. koreensis, B. korlensis, B. kribbensis, B. krulwichiae, B. laevolacticus, B. larvae, B. laterosporus, B. lautus, B. lehensis, B. lentimorbus, B. lentus, B. licheniformis, B. ligniniphilus, B. litoralis, B. locisalis, B. luciferensis, B. luteolus, B. luteus, B. macauensis, B. macerans, B. macquariensis, B. macyae, B. malacitensis, B. mannanilyticus, B. marinus, B. marisflavi, B. marismortui, B. marmarensis, B. massiliensis, B. megaterium, B. mesonae, B. methanolicus, B. methylotrophicus, B. migulanus, B. mojavensis, B. mucilaginosus, B. muralis, B. murimartini, B. mycoides, B. naganoensis, B. nanhaiensis, B. nanhaiisediminis, B. nealsonii, B. neizhouensis, B. niabensis, B. niacini, B. novalis, B. oceanisediminis, B. odysseyi, B. okhensis, B. okuhidensis, B. oleronius, B. oryzaecorticis, B. oshimensis, B. pabuli, B. pakistanensis, B. pallidus, B. pallidus, B. panacisoli, B. panaciterrae, B. pantothenticus, B. parabrevis, B. paraflexus, B.pasteurii, B. patagoniensis, B. peoriae, B. persepolensis, B. persicus, B. pervagus, B. plakortidis, B. pocheonensis, B. polygoni, B. polymyxa, B. popilliae, B. pseudalcaliphilu, B. pseudofirmus, B. pseudomycoides, B. psychrodurans, B. psychrophilus, B. psychrosaccharolyticus, B. psychrotolerans, B. psychrodurans, B. psychrophilus, B. pulvifaciens, B. pumilus, B. purgationiresistens, B. pycnus, B. qingdaonensis, B. qingshengii, B. reuszeri, B. rhizosphaerae, B. rigui, B. ruris, B. safensis, B. salarius, B. salexigens, B. saliphilus, B. schlegelii, B. sediminis, B. selenatarsenatis, B. selenitireducens, B. seohaeanensis, B. shacheensis, B. shackletonii, B. siamensis, B. silvestris, B. simplex, B. siralis, B. smithii, B. soli, B. solimangrovi, B. solisalsi, B. songklensis, B. sonorensis, B. sphaericus, B. sporothermodurans, B. stearothermophilus, B. stratosphericus, B. subterraneus, B. subtilis, B. taeanensis, B. tequilensis, B. thermanarcticus, B. thermoaerophilus, B. thermoamylovorans, B. thermocatenulas, B. thermocloacae, B. thermocopriae, B. thermodenitrificans, B.thermoglucosidasius, B. thermolactis, B. thermoleovorans, B. thermophilus, B. thermoruber, B. thermosphaericus, B. thiaminolyticus, B. thioparans, B. thuringiensis, B. tianshenii, B. trypoxylicola, B. tusciae, B. validus, B. vallismortis, B. vedderi, B. velezensis, B. vietnamensis, B. vireti, B. vulcani, B. wakoensis, B. weihenstephanensis, B. xiamenensis, B. xiaoxiensis, B. zhanjiangensis, etc. .

[0029] Examples of species in the genus Sporosarcina include Sporosarcina luteola, Sporosarcina aquimarina, Sporosarcina contaminans, Sporosarcina globispora, Sporosarcina newyorkensis, Sporosarcina pasteurii, Sporosarcina psychrophile, Sporosarcina saromensis, Sporosarcina siberiensis, Sporosarcina soli, Sporosarcina terrae, Sporosarcina thermotolerans, and Sporosarcina ureae.

[0030] Furthermore, microorganisms can be broadly used, including bacteria, yeasts, fungi, protists, and protozoa. Among these, spore-forming microorganisms capable of forming spores (ascospores, spores, and dimers) are preferred, considering that the microorganisms are included in the cement admixture and the hardened cement is in an alkaline environment.

[0031] Microorganisms that produce carbon dioxide through metabolism may be in-house cultured or commercially available. For example, microbial preparations described in the examples of this specification can be purchased, or strains such as Sporosarcina pasteurii DSM 33 (Sporosarcina genus), Bacillus cohnii DSM 6307 (Bacillus genus), Bacillus halodurans DSM 497 (Bacillus genus), and Bacillus pseudofirmus DSM 8715 (Bacillus genus) can be purchased from DSMZ (German Collection of Microorganisms and Cell Cultures).

[0032] [Inhibitors for the growth of bacteria with sulfur-oxidizing ability] The growth inhibitor for sulfur-oxidizing bacteria can be any substance that can inhibit the growth of sulfur-oxidizing bacteria.

[0033] Bacteria with sulfur-oxidizing ability that affect the corrosion of hardened cement used in sewage systems include, for example, sulfur-oxidizing bacteria such as Acidithiobacillus albertensis, Acidithiobacillus thiooxidans, Halothiobacillus neapolitanus, Thiomonas sp., and Acidithiobacillus ferrooxidans. It should be noted that bacteria with sulfur-oxidizing ability are not limited to sulfur-oxidizing bacteria, but also include iron-oxidizing bacteria (such as Acidithiobacillus ferrooxidans) that can oxidize sulfur compounds.

[0034] Examples of bacterial growth inhibitors with sulfur-oxidizing ability include nickel, tungsten, lead, zinc, cobalt, tin and their compounds, hydroxy acid compounds, and dicarboxylic acid compounds.

[0035] However, from the viewpoint of maintaining the activity of microorganisms that generate carbon dioxide through metabolism, it is preferable that the growth inhibitor of sulfur-oxidizing bacteria be selected from the group consisting of nickel and nickel compounds, tungsten and tungsten compounds, dicarboxylic acid compounds, hydroxy acid compounds, and mixtures thereof.

[0036] Nickel and tungsten are supplied as fine powders of the metal (with zero oxidation state).

[0037] Nickel compounds include nickel oxides, nickel phthalocyanine powder, and nickel phthalocyanine derivative powders. Nickel phthalocyanine powder is a powder of a compound in which nickel atoms are coordinated to a phthalocyanine skeleton that does not have substituents.

[0038] Nickel phthalocyanine derivative powder is a powder of a compound having a substituted atom other than a hydrogen atom or a substituent on the benzene ring of a nickel phthalocyanine skeleton molecule. It is typically a water-insoluble compound that is almost insoluble in acids.

[0039] The substituted atoms or substituents of nickel phthalocyanine derivatives are as described in Japanese Patent Publication No. 3320074, but specifically include halogen atoms, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted thioalkoxy groups, alkyl-substituted amino groups, carbocyclic aromatic amino groups, mono or disubstituted amino groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted arylthio groups, substituted or unsubstituted aromatic ring groups, and the like.

[0040] Examples of tungsten compounds include alkali metal salts of tungstic acid, hydrates of alkali metal salts of tungstic acid, tungsten(VI) oxide (WO3), and hydrates of tungsten(VI) oxide. Specific examples of tungsten compounds include, for example, W 28 O 58Examples include Na2WO4, CaWO4, CaWO4·H2O, CaWO4·2H2O, or 5(NH4)2O·12WO3·nH2O (n=0~5).

[0041] Dicarboxylic acid compounds can be provided, for example, in the form of alkali metal salts of oxalic acid, succinic acid, malonic acid, glutaric acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid.

[0042] Hydroxy acid compounds can be provided, for example, in the form of alkali metal salts of glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid.

[0043] A bacterial growth inhibitor having sulfur-oxidizing ability is incorporated into the cement admixture in a proportion of 0.01% by mass or more, preferably 0.05% by mass or more, relative to the total cement composition, from the viewpoint of resistance to sulfuric acid degradation.

[0044] Furthermore, bacterial growth inhibitors with sulfur-oxidizing ability are blended into cement admixtures in an amount of 100 mmol (mmol / CFU) or less per 1 CFU of microorganism, preferably 50 mmol / CFU or less, from the viewpoint of maintaining the activity of microorganisms that generate carbon dioxide through metabolism.

[0045] Furthermore, the cement admixture of the present invention does not contain blast furnace slag fine powder. In the present invention, when referring to blast furnace slag fine powder, it means a specific surface area of ​​7000 cm² obtained by the specific surface area test of JIS R 5201 8.1. 2 This refers to blast furnace slag fine powder of 1 / g or more. It is believed that using blast furnace slag fine powder with a large specific surface area and therefore small particle size increases the opportunity for contact with microorganisms that generate carbon dioxide through the above metabolism, thereby inhibiting the self-healing performance of the cement hardened body by these microorganisms.

[0046] Therefore, the above specific surface area is 7000 cm². 2Blast furnace slag powder of less than / g may be included in the cement admixture of the present invention, but if blast furnace slag powder is included, the above specific surface area must be 5000 cm². 2 It is preferable that the amount be less than / g.

[0047] The cement admixture of the present invention preferably contains a nutrient source for microorganisms that generate carbon dioxide through the above-mentioned metabolism (hereinafter referred to as a microbial nutrient source).

[0048] Microbial nutrients can include one or more organic carbon sources (sugars, starches, lipids, etc.), inorganic carbon sources (sodium carbonate, etc.), organic nitrogen sources (amino acids, peptides, proteins, etc.), inorganic nitrogen sources (ammonia salts, nitrates, etc.), and inorganic nutrients (P, S, K, Na, etc.).

[0049] Any organic carbon source that can be metabolized by microorganisms is acceptable, but from the viewpoint of mechanical strength, compatibility, and assimilation by microorganisms of the hardened cement, biodegradable plastics are preferred.

[0050] Examples of biodegradable plastics include polylactic acid, polycaprolactone, polyhydroxyalkanoate (microbially produced polyester), polyglycolic acid, modified polyvinyl alcohol, casein, modified starch, and low-substituted polysaccharide derivatives (such as low-substituted cellulose acetate), with polylactic acid being preferred.

[0051] When the cement admixture of the present invention contains a biodegradable plastic as an organic carbon source, the blending ratio of the biodegradable plastic to the total mass of the cement admixture is 40% by mass or more and 90% by mass or less, preferably 50% by mass or more and 80% by mass or less.

[0052] The cement admixture of the present invention can be used by mixing it with cement for the purpose of creating hardened bodies of various cement compositions such as concrete and mortar.

[0053] From the viewpoint of maintaining the strength of the hardened cement, the cement admixture of the present invention is blended into the cement composition in a proportion of 5% by mass or less, preferably 2% by mass or less, relative to the total amount of the cement composition.

[0054] <Cement composition> The cement composition of the present invention comprises the cement admixture of the present invention and cement.

[0055] [cement] There are no particular limitations on the cement used in the cement composition of the present invention. For example, one or more types of Portland cement (JIS R5210), blended cement (JIS R5211, R5212, R5213), eco-cement, etc., can be used.

[0056] As explained above, the admixtures for cement are as described above, and their explanation will be omitted here.

[0057] The cement composition of the present invention optionally contains fine aggregate (sand, etc.) and coarse aggregate (gravel, etc.). It may also optionally contain admixtures such as air-entraining agents, water-reducing agents (air-entraining water-reducing agents, water-reducing agents, high-performance air-entraining water-reducing agents, etc.), fluidizers, setting and hardening regulators, rapid setting agents, rust inhibitors, and waterproofing agents.

[0058] Furthermore, the cement composition of the present invention may contain powders that undergo a hydration reaction under alkaline conditions, such as silica powder, blast furnace slag powder, fly ash, and rice husk ash, but the specific surface area of ​​these particles is 7000 cm². 2 It is less than / g and 5000cm 2 It is preferable that the amount be less than / g.

[0059] Furthermore, other admixtures such as cement admixture polymers and expansives may be included.

[0060] The cement composition of the present invention is prepared by powder-mixing the admixture of the present invention with cement and optionally other powder components, adding water and liquid components and kneading to form a paste, and mixing in fine aggregate and coarse aggregate as needed.

[0061] <Hardened cement> The cement hardened body of the present invention is obtained by applying the cement composition of the present invention to an object or injecting it into a formwork and curing it for a predetermined period of time.

[0062] <Method for manufacturing hardened cement> Figure 1 is a flow chart showing the method for manufacturing a cement hardened body according to the present invention. As shown in the figure, the method for manufacturing a cement hardened body according to the present invention comprises a mixing step and a hardening step.

[0063] [Mixing process (S110)] In this process, a cement composition is mixed with cement and a cement admixture containing a growth inhibitor for microorganisms that generate carbon dioxide through metabolism and bacteria that have sulfur-oxidizing ability.

[0064] Since microorganisms that generate carbon dioxide through metabolism, growth inhibitors of bacteria with sulfur-oxidizing ability, and cement admixtures, cement, and cement compositions containing these have already been explained, their explanation will be omitted here.

[0065] The admixture of cement compositions can be carried out using well-known methods, for example, by powder mixing cement admixtures, cement, and other powder components, and then adding water and liquid components and kneading after the powder mixing.

[0066] The resulting cement composition is then poured into a formwork as appropriate and compacted to remove air bubbles. Compaction is carried out by tapping the surface of the poured cement composition with a tamper, poking it with a rod, or by vibrating with a vibrator (this constitutes the mixing process (S110)).

[0067] [Curing process (S120)] In this process, the cement composition is hardened to obtain a hardened body. The cement composition may be spread and hardened on the object using a trowel or similar tool, or it may be poured into a formwork and hardened. If reinforced concrete is to be used, reinforcing bars are placed in the formwork beforehand.

[0068] When injecting a cement composition into a formwork, it is preferable to compact it to remove air bubbles. Compaction is performed by tapping the surface of the injected cement composition with a tamper, poking it with a rod, or by vibrating with a vibrator.

[0069] The cement composition applied or poured into the formwork is cured until the required compressive strength is obtained, and a hardened cement body is obtained (this completes the hardening process (S120)).

[0070] As described above, according to the cement admixture, cement composition, hardened cement body, and method for producing a hardened cement body of the present invention, the cement admixture does not contain blast furnace slag fine powder, thus preventing inhibition of the activity of microorganisms that generate carbon dioxide through metabolism by blast furnace slag fine powder. Therefore, when mixed into a cement composition, a hardened cement body can be obtained that possesses both self-healing properties for cracks and resistance to sulfuric acid degradation.

[0071] Therefore, corrosion of the cement hardened body can be suppressed even in the presence of sulfuric acid-producing microorganisms, such as in sewage treatment facilities, and any cracks that do occur can be self-repaired. Thus, maintenance costs and labor for the cement hardened body can be reduced, and the extended product life of the cement hardened body can also reduce the life cycle costs, including manufacturing and maintenance.

[0072] Furthermore, extending the product lifespan of cement-hardened materials can simultaneously lead to a reduction in environmental impact. [Examples]

[0073] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0074] <1. Test to confirm the inhibitory effect of growth inhibitors on bacteria with sulfur-oxidizing ability on microorganisms> We conducted tests to confirm whether inhibitors of bacterial growth that possess sulfur-oxidizing ability inhibit the growth of microorganisms that produce carbon dioxide through metabolism.

[0075] First, a suspension was prepared by adding a microbial preparation (Basilisk HA, manufactured by Basilisk Contractions BV) to sterile water at pH 9 at a concentration of 0.5% (w / v). Then, growth inhibitors A (tungsten(VI) oxide (WO3)), B (nickel (metallic nickel fine powder, oxidation state = 0)), and C (calcium tartrate) were added to this suspension at concentrations of 1.0%, 0.5%, 0.1%, and 0.05%, respectively, to prepare a total of 12 suspensions containing microbial preparations with growth inhibitors.

[0076] Next, a suspension containing a microbial preparation without growth inhibitors (pH 9, 0.5% concentration (w / v) of the above microbial preparation) was selected as the target category.

[0077] The composition of the microbial preparation (Basilisk HA, manufactured by Basilisk Contractions BV) is as shown in Table 1 below.

[0078] [Table 1]

[0079] These 13 suspensions (100 ml each) were cultured with shaking at 30°C for 24 hours, and then the bacterial count was measured using the dilution method.

[0080] The results are shown in Figure 2. As shown in the figure, when nickel was added as a growth inhibitor for bacteria with sulfur oxidation ability, some inhibition of microbial growth was observed, but it was confirmed that there were still a number of bacteria that did not affect the self-repair function. Therefore, it was found that the growth inhibitor itself does not have a decisive negative impact on the self-repair function of microorganisms.

[0081] Furthermore, this study revealed that the optimal concentration of each growth inhibitor added to a 0.5% (w / v) microbial preparation was 0.1% (w / v).

[0082] <2. Leakage confirmation test for concrete (cement hardened material)> A cementite was prepared from a cement composition containing a microbial agent (Basilisk HA, manufactured by Basilisk Contraction BV) and a bacterial growth inhibitor with sulfur-oxidizing ability. A leakage test was then conducted on the cementite to confirm its self-healing performance.

[0083] 3-1. Examples i) Preparation of cement compositions for Examples 1-2 and Reference Example 1 9.45 parts by mass of ordinary Portland cement (product name: ordinary Portland cement, manufacturer: Taiheiyo Cement Corporation) was mixed with 0.15 parts by mass of a microbial preparation (Basilisk HA, manufactured by Basilisk Contraction BV) and 0.15 parts by mass of growth inhibitor 1 (super antibacterial agent, manufactured by Ando Hazama Kogyo Co., Ltd.). The mixture was then mixed into a powder. The microbial preparation was added externally, meaning at an amount of 5 kg per 1 m³ of the mixed powder of ordinary Portland cement, microbial preparation, and growth inhibitor 1.

[0084] To this mixed powder, 4.95 parts by mass of water (groundwater) was mixed to create a cement paste. Further mixing in 10.17 parts by mass of fine aggregate 1 (product name: Yufutsu, manufacturer: Sugawara Sangyo Co., Ltd.), 15.12 parts by mass of fine aggregate 2 (product name: Horonobe, manufacturer: Hokuko Kogyo Co., Ltd.), and 30.12 parts by mass of coarse aggregate (product name: Garo, manufacturer: Taiheiyo Cement Corporation) was performed to obtain the cement composition of Example 1 with a formulation of 30-18-20N.

[0085] Next, the materials were mixed and kneaded with the same composition and formulation as in Example 1, except that growth inhibitor 1 was replaced with growth inhibitor 2 (Celeb antibacterial agent, manufactured by Ando Hazama Kogyo Co., Ltd.) at a ratio of 0.15 parts by mass, to obtain the cement composition of Example 2.

[0086] Furthermore, the materials were mixed and kneaded with the same composition and formulation as in Example 1, except that a growth inhibitor was not added, to obtain the cement composition of Reference Example 1.

[0087] The compositions of growth inhibitor 1 and growth inhibitor 2 are as shown in Table 2 below.

[0088] [Table 2] *2 Metallic nickel *3 Tungsten(IV) trioxide (WO3)

[0089] ii) Preparation of crack samples from hardened cement for leakage testing. Figure 3 is a schematic diagram showing the formwork for forming the cement hardened body used in the water leakage test of the embodiment. As shown in the figure, three formwork A were created by sealing the bottom of a polyvinyl chloride pipe a with an inner diameter of w100 mm and a height of h80 mm with an acrylic plate b. The gap between the polyvinyl chloride pipe and the acrylic plate was filled with sealant c.

[0090] The cement compositions of Examples 1-2 and Reference Example 1 were filled into each polyvinyl chloride pipe a in a single layer through the open top surface of formwork A. After tamping with a tamping rod as needed and vibrating formwork A to remove air from the cement composition, the top surface was smoothed and leveled with a trowel.

[0091] The cement composition filled into formwork A was cured in the air at room temperature for 28 days to obtain the hardened cement bodies of Examples 1-2 and Reference Example 1.

[0092] After 28 days, the acrylic plate of formwork A was removed, and as shown in Figure 4, a load was applied to the hardened cement body 10 from both sides in the width direction using a compression testing machine B, forcibly inducing cracks 12 in the hardened body 10. The crack width of the hardened body 10 was measured with a crack gauge (FAC-5-F, manufactured by Tokyo Sokki Kenkyusho Co., Ltd.) and was 0.35 mm for the hardened bodies 10 of Reference Example 1 and Example 1, respectively, and 0.30 mm for the hardened body 10 of Example 2.

[0093] iii) Leakage test (evaluation of self-healing performance) Next, as shown in Figure 5, formwork a' and a'', which have the same diameter as formwork a, are joined to the top and bottom of formwork a with sealant, and a constricted section d, which has a smaller diameter than formwork a'', is provided at the bottom of formwork a''. The bottom of the constricted section d is open, and a container f is provided below the constricted section d.

[0094] On the side of formwork a', a hole e with a diameter of approximately 10 mm is provided at a height of 50 mm from the joint with formwork a.

[0095] The hole e is provided to maintain a constant hydrostatic pressure in the hardened body 10 inside the formwork a by draining the water poured in from the formwork a' through the hole e.

[0096] Then, water was poured into the formwork a' from the top of the formwork a' at a rate such that the water level inside the formwork a' remained constant at the height of the hole e, that is, so that the water head pressure of the hardened body 10 inside the formwork a remained constant by draining the poured water through the hole e. The water g that leaked out through the cracks 12 in the hardened body 10 was collected in a container f, and the amount of leakage per day was measured.

[0097] The results are shown in Figure 6. As shown in the figure, the hardened cement body of Reference Example 1, to which only the microbial agent was added, began to show a decrease in water leakage after 10 days from the start of the test, and by approximately 50 days, the amount of water leakage had decreased to less than 10% of the amount at the start of the test. This is thought to be due to the self-healing performance of the hardened body 10 by the microbial agent.

[0098] Furthermore, a similar trend was observed in the hardened bodies of Examples 1 and 2 obtained from cement compositions that did not contain blast furnace slag fine powder, indicating that the self-healing performance of the microbial preparation was fully demonstrated despite the addition of growth inhibitors.

[0099] Furthermore, the cured body of Example 2 was able to completely stop water leakage at a relatively early stage of approximately 46 days, which is thought to be due to the smaller crack width compared to the cured bodies of Reference Example 1 and Example 1.

[0100] 3-2. Comparative Examples i) Preparation of the cement compositions of Comparative Examples 1-2 and Reference Example 1 The materials were mixed and kneaded with the same composition and formulation as in Example 1, except that growth inhibitor 1 was replaced with growth inhibitor 3 (super antibacterial agent, manufactured by Ando Hazama Kogyo Co., Ltd.) at a concentration of 1.0 part by mass (per 100 parts by mass of cement), to obtain the cement composition of Comparative Example 1.

[0101] Next, the materials were mixed and kneaded with the same composition and formulation as in Example 1, except that growth inhibitor 1 was replaced with growth inhibitor 4 (Celeb antibacterial agent, manufactured by Ando Hazama Kogyo Co., Ltd.) at a concentration of 1.0 part by mass (per 100 parts by mass of cement), to obtain the cement composition of Comparative Example 2.

[0102] Furthermore, the cement composition of Reference Example 1 was used as the comparative category.

[0103] The compositions of the Super Antibacterial Agent and the Celebrity Antibacterial Agent are shown in Table 3 below.

[0104] [Table 3] *4 Metallic nickel *5 Tungsten trioxide (IVc)(WO3) *6: The blast furnace slag fine powder is Fine Cerament 5A (manufactured by Day-C, specific surface area: 10,000 cm²). 2 We adopted values ​​of / g or higher (Braine value).

[0105] ii) Preparation of crack samples from hardened cement for leakage testing. Crack samples of hardened cement for leakage testing were prepared from the cement compositions of Comparative Examples 1 and 2 and Reference Example 1, in the same manner as in the above examples. The crack width of the hardened body 10 was measured with a crack gauge (FAC-5-F, manufactured by Tokyo Measuring Instruments Laboratory Co., Ltd.) and was 0.4 mm for the hardened bodies 10 of Reference Example 1 and Comparative Example 2, and 0.35 mm for the hardened body 10 of Comparative Example 1.

[0106] iii) Leakage test (evaluation of self-healing performance) Leakage tests were conducted on each of the hardened cement compositions obtained from Comparative Examples 1 and 2 and Reference Example 1, in the same manner as in the Examples. The results are shown in Figure 7.

[0107] As shown in the figure, the cement hardened body of Reference Example 1, to which only a microbial agent was added, stopped leaking water approximately 40 days after the start of the test. In contrast, the hardened bodies of Comparative Examples 1 and 2 continued to leak water even after approximately 45 days from the start of the test, and the amount of leakage compared to the start of the test was still very large, at approximately 40% by the final day, March 14th.

[0108] This is thought to be because the blast furnace slag powder, which was included as a diluent in growth inhibitors 3 and 4 contained in the cement-based organisms of Comparative Examples 1 and 2, inhibited the activity of the microorganisms in the microbial preparations, thereby reducing their self-healing performance.

Claims

1. A cement admixture comprising a microorganism that generates carbon dioxide through metabolism and a growth inhibitor of bacteria having sulfur-oxidizing ability, A cement admixture characterized by not containing blast furnace slag fine powder.

2. The cement admixture according to claim 1, wherein the microorganism is selected from the group consisting of the genera Planococcus, Bacillus, and Sporosarcina.

3. The cement admixture according to claim 1, wherein the bacterial growth inhibitor having sulfur-oxidizing ability is selected from the group consisting of nickel and nickel compounds, tungsten and tungsten compounds, dicarboxylic acid compounds, hydroxy acid compounds, and mixtures thereof.

4. The cement admixture according to claim 1, comprising polylactic acid as a nutrient source for the microorganisms.

5. A cement composition comprising a cement admixture according to any one of claims 1 to 4, and cement.

6. A cementite-hardened body obtained by hardening the cement composition described in claim 5.

7. A cement composition comprising a cement admixture containing a growth inhibitor for microorganisms that generate carbon dioxide through metabolism and bacteria that have sulfur-oxidizing ability, and cement, is mixed in a mixing step. A method for producing a cementite hardened body, comprising a hardening step of hardening the cement composition to obtain a hardened body.

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