Precast concrete bodies

Abstract

To provide a precast concrete molding which is excellent in at least one of air content stability, substance invasion prevention and freeze-thaw resistance in addition to a high strength.SOLUTION: A precast concrete molding is a cured product of a concrete composition which contains a microcapsule having a core-shell structure having a core composed of a water-repellent organosilicon material selected from the group consisting of organosilane, organosilane partial condensate and a branched siloxane resin, and a shell of a silicone-based network polymer including a silica unit, and cement and at least one aggregate, and contains 0.01 or more and less than 0.5 pt.wt. of the microcapsule per 100 pts.wt. of the cement.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to precast concrete bodies containing specific chemical admixtures. [Background technology]

[0002] In recent years, there has been an increasing need to extend the service life of concrete structures, such as those made of reinforced concrete (RC). Furthermore, as society develops, concrete structures have become larger, taller, and more diverse, necessitating even greater strength and durability. Meanwhile, numerous cases of deterioration have been reported for concrete structures and secondary concrete products, posing a social problem. One cause of early deterioration in concrete structures and secondary concrete products is cracks that appear on the concrete surface in the early stages of their life. These cracks allow deterioration factors such as salt, carbon dioxide, and water to penetrate the concrete, causing serious problems such as salt damage, carbonation, alkali-aggregate reaction, and frost damage. Furthermore, salt damage and carbonation corrode the steel within the reinforced concrete, reducing the durability of reinforced concrete structures and secondary concrete products. Furthermore, alkali-aggregate reaction and frost damage accelerate cracking and, in some cases, cause steel fracture, reducing the load-bearing capacity of concrete structures and secondary concrete products.

[0003] The above-mentioned salt damage and carbonation degradation factors do not act singly; rather, multiple factors can interact with each other, resulting in a serious deterioration problem. For example, carbonation of concrete accelerates corrosion of steel materials within concrete structures. Salt damage has been reported to increase the rate of carbonation (carbonation). This leads to the expansion of cracks in concrete structures. Furthermore, airborne salt, which causes salt damage, increases the osmotic pressure of concrete pore water, which, combined with the freeze-thaw action (frost damage) on the concrete surface, causes surface peeling and promotes further salt penetration. Furthermore, snow-melting agents sprayed in snowy areas react with components in the concrete, causing volume expansion and collapsing the concrete surface. When these combined effects are combined with cyclic loading (fatigue) caused by running wheel loads, the progression of deterioration is further accelerated.

[0004] As a method for suppressing or preventing deterioration of these concrete structures and secondary concrete products, various chemical admixtures for concrete, surface impregnation agents, etc., including water repellents, have been proposed.

[0005] Patent Document 1 proposes a method of blending a hydrolyzable organosilane, which is a water repellent (hydrophobic substance), in addition to an amine derivative into a cement composition, and realizes cement concrete that has the properties of preventing water absorption, preventing chloride ion penetration, and inhibiting carbonation, but the compressive strength of the hardened product is clearly reduced.

[0006] Patent Document 2 proposes a method of blending a silane compound having a hydrolyzable group, which is a water repellent, into mortar and concrete as a salt-blocking agent for cement, and achieves mortar and concrete with water absorption prevention properties and chloride ion penetration prevention properties. However, the compressive strength of the hardened product is clearly reduced, and in particular, the air content has increased beyond the 4.5±1.5% specified by the Japan Society of Civil Engineers, raising concerns about a reduction in freeze-thaw resistance.

[0007] Patent Document 3 proposes a method for achieving waterproofing without reducing strength by incorporating silicone oil as a water repellent when producing foam concrete. However, the concrete production is divided into two major steps, which makes concrete production difficult at actual construction sites and increases the product price even when produced in a factory, which can be problematic from an economic standpoint.

[0008] Patent Document 4 also proposes a method of achieving waterproofing without reducing strength by adding silicone oil as a hydrophobic substance to an aqueous slurry of calcium silicate, a constituent mineral of cement. However, since silicone oil is used in a relatively large amount, about 1.0 to 5.0% by weight of cement, compared to other admixtures for concrete, it has an effect on fluidity and the amount of air entrained, and increases the price of concrete, which can be problematic from an economic standpoint.

[0009] Patent Document 5 proposes a method of adding alkylalkoxysilane and using reactive aggregate containing reactive silica to suppress the decrease in strength that occurs when a hydrophobic substance is blended to make the mortar waterproof, thereby generating silica gel inside and filling the air holes. However, reactive aggregate containing reactive silica cannot be used in Japan because it causes the so-called alkali-aggregate reaction, a serious deterioration phenomenon that can cause the internal steel to fracture.

[0010] Patent Document 6 proposes a method of adding inorganic fine particles with a diameter of 0.02 to 20 microns that have been surface-treated with a fatty acid, which is a water-repellent agent, and having these fine particles block the pores inside the concrete, thereby achieving waterproofing without reducing strength.However, this method may reduce the amount of air required to obtain freeze-thaw resistance.

[0011] Patent Document 7 proposes a method for achieving cement concrete with good workability and compressive strength by adding an organosilane as a water repellent to a polymer dispersion for cement admixture, which prevents water absorption and chloride ion penetration. However, the use of two types of chemical admixtures can result in reduced strength depending on their ratio. Furthermore, the organosilane is used in relatively high amounts, about 0.5 to 2.0% by weight of cement, and about 5 to 20% by weight of the polymer, which is relatively high for a concrete admixture. This can have an adverse effect on fluidity, the amount of air entrained, and the cost of the concrete, which can be problematic from an economic standpoint.

[0012] Patent Document 8 proposes a method of achieving waterproofing without reducing strength by adsorbing a water repellent agent onto the surface of a filler such as calcium carbonate and then blending it in. However, this method requires the time and effort of separately preparing a filler with a water repellent agent adsorbed onto its surface, which can be problematic from an economic standpoint.

[0013] Patent Document 9 proposes a method for achieving sufficient waterproofing performance without using large amounts of expensive alkylalkoxysilane and without reducing strength by increasing the concentration of alkylalkoxysilane, a water repellent agent, near the surface of a hardened cement product and decreasing its concentration internally. However, this type of uneven waterproofing performance can lead to harmful substances such as salt reaching the reinforcing bars when cracks progress beyond the surface, causing rust and corrosion of the reinforcing bars.

[0014] Patent Document 10 proposes a method for improving the waterproofing of a hardened body by adding a water repellent agent whose main component is a fatty acid ester compound in an amount of about 0.01 to 5.0% by weight based on the amount of cement. However, this method does not aim to, and has not achieved, a hardened body that simultaneously satisfies not only waterproofing but also strength, drying shrinkage suppression, freeze-thaw resistance, and air entrainment stability.

[0015] Patent Document 11 proposes a method for improving the waterproofing properties of hardened cement paste by mixing aggregate obtained by adding Portland cement, water, and sand to a waterproofing agent, water-stopping agent, or deterioration inhibitor containing an agent that reacts with calcium hydroxide in the hardened cement paste to produce a water-insoluble substance. However, with this method, it is sometimes difficult to determine the optimal amount of water repellent to be added.

[0016] Patent Document 12 proposes a method for improving the waterproofing properties of concrete by using a self-healing cement admixture containing a water repellent and calcium sulfoaluminate or silica powder. However, in this method, the cement admixture for imparting waterproofing is prepared separately, which increases the price of the concrete, which can be problematic from an economic standpoint.

[0017] Patent Document 13 proposes a method of using a concrete modifier made of an alkoxysilane derivative to modify the surface condition of hardened cement paste and prevent water infiltration and escape, thereby reducing drying shrinkage, improving the durability of the hardened cement paste, and preventing deterioration over the long term. However, because it is used in relatively large amounts of about 1.0 to 10.0% by weight based on the cement, which is a relatively large amount compared to other concrete admixtures, it can have a significant impact on fluidity, the amount of air entrained, etc. Furthermore, the examples do not clearly indicate the compressive strength or resistance to freeze-thawing, particularly the degree of the desired reduction in drying shrinkage.

[0018] Patent Document 14 proposes a method for improving the waterproofing of hardened concrete bodies by using a creamy aqueous emulsion of an organosilicon compound consisting of alkylalkoxysilane, polyorganosiloxane, and an emulsifier, which can be applied to the surface of hardened concrete bodies without dripping. However, the method does not aim to, and has not achieved, a hardened concrete body that simultaneously satisfies not only waterproofing but also strength, drying shrinkage suppression, freeze-thaw resistance, and air entrainment stability.

[0019] Patent Document 15 proposes a method of improving the resistance of concrete that uses fly ash cement to the freeze-thaw action by mixing an admixture consisting of an air-entraining agent and an antifoaming agent, dimethylpolysiloxane, into the concrete when it is mixed. However, this method is not intended to provide waterproofing and is limited to concrete that contains fly ash, making it less versatile.

[0020] Patent Document 16 proposes a method for improving the water absorption prevention and shrinkage reduction properties of hardened concrete by mixing in a dense layer forming agent for concrete composed of a fatty acid ester mixture and an alkoxysilane derivative, but this method does not aim to simultaneously satisfy all of these requirements, as well as compressive strength, resistance to freeze-thaw cycles, and stability of entrained air.

[0021] Patent Document 17 proposes a method for obtaining ready-mixed concrete having a slump and strength conforming to JIS A 5038 by incorporating a cement dispersant and an alkyltrimethoxysilane, and for providing a hardened body that is prevented from deterioration due to alkali-silica reaction. However, since the main purpose of this method is to suppress the alkali-silica reaction, the type of cement dispersant that can be used and the ratio of this cement dispersant to alkyltrimethoxysilane are limited, and therefore the range of application is limited, which may cause problems with versatility. [Prior art documents] [Patent documents]

[0022] [Patent Document 1] Japanese Patent Application Publication No. 2-124751 [Patent Document 2] Japanese Patent Application Publication No. 2-199048 [Patent Document 3] Japanese Patent Application Publication No. 57-92561 [Patent Document 4] Special Publication No. 2-15511 [Patent Document 5] Special Publication No. 58-500061 [Patent Document 6] Japanese Patent Application Publication No. 62-292660 [Patent Document 7] Japanese Patent Application Publication No. 1-275454 [Patent Document 8] Japanese Patent Application Publication No. 1-317140 [Patent Document 9] Japanese Patent Application Publication No. 10-36157 [Patent Document 10] Japanese Patent Application Publication No. 7-69696 [Patent Document 11] Japanese Patent Application Laid-Open No. 2002-97045 [Patent Document 12] Japanese Patent Application Laid-Open No. 2011-126729 [Patent Document 13] Japanese Patent Application Laid-Open No. 2012-132002 [Patent Document 14] Japanese Patent Application Laid-Open No. 2017-25181 [Patent Document 15] Japanese Patent Application Publication No. 4-317447 [Patent Document 16] Japanese Patent Application Laid-Open No. 2013-193884 [Patent Document 17] Japanese Patent Application Publication No. 6-305803 Summary of the Invention [Problem to be solved by the invention]

[0023] The various chemical admixtures, such as water repellents, that have been proposed or put into practical use so far are limited to addressing the various causes of deterioration, such as imparting water repellency to the surface of the hardened concrete, and therefore present a trade-off, such as improving waterproofing but decreasing compressive strength. Therefore, there has been no proposal to use a single chemical admixture to provide precast concrete bodies that not only have high strength but also excellent in at least one of air content stability, resistance to material intrusion, and freeze-thaw resistance.

[0024] An object of the present invention is to provide a precast concrete molded body that has high strength and is excellent in at least one, and preferably all, of air content stability, resistance to material intrusion, and resistance to freezing and thawing. [Means for solving the problem]

[0025] The object of the present invention is to a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units Microcapsules having a core-shell structure having and Cement, and At least one type of aggregate The above object is achieved by a precast concrete molded body which is a hardened product of a concrete composition containing the microcapsules in an amount of 0.01 to less than 0.5 parts by weight per 100 parts by weight of the cement.

[0026] Preferably, the organosilane is an organosilane containing at least one silicon-bonded alkyl group having 1 to 30 carbon atoms.

[0027] The branched siloxane resin has the formula RSiO 3 / 2 It is preferable that the siloxane resin contains the siloxane unit (R is an alkyl group) of the formula:

[0028] The amount of air contained in the concrete composition as measured in a test based on JIS A 1128 is preferably 3 to 6% by volume.

[0029] The precast concrete body preferably has a compressive strength ratio of more than 100% after 7 days of air curing in a compression test based on JIS A 1108 (Method for testing compressive strength of concrete) and JIS A 6204 (Chemical admixtures for concrete).

[0030] The present invention also relates to a waterway structure, coastal structure, or marine structure made of the precast concrete molded article.

[0031] The present invention also relates to a road structure comprising the precast concrete body.

[0032] The present invention also relates to a retaining wall structure comprising the precast concrete body.

[0033] The present invention provides a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units A preparation step of preparing an unhardened concrete composition containing microcapsules having a core-shell structure having the following structure: A hardening and shaping step of hardening and shaping the unhardened concrete composition. A method for producing a precast concrete body, comprising: the unhardened concrete composition comprises cement and at least one aggregate; The present invention also relates to a method for producing a precast concrete molded body, wherein the microcapsules are mixed in the preparation step in an amount of 0.01 to less than 0.5 parts by weight per 100 parts by weight of the cement.

[0034] The present invention also provides a method for improving at least one of the strength, substance penetration resistance, freeze-thaw resistance, and air content stability of a precast concrete body, the method comprising: a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units A blending step of blending microcapsules having a core-shell structure having the above-mentioned structure into a concrete composition for the precast concrete molded body, the concrete composition comprises cement and at least one aggregate; In the blending step, the microcapsules are blended in an amount of 0.01 to less than 0.5 parts by weight per 100 parts by weight of the cement. The present invention also relates to a method for improving the strength of a precast concrete body, as well as at least one of its resistance to substance intrusion, resistance to freeze-thaw cycles, and stability of air content.

[0035] In this specification, "wt %" and "parts by weight" have the same meanings as "% by mass" and "parts by mass", respectively. [Effects of the Invention]

[0036] The precast concrete molded body of the present invention is a hardened product of an (unhardened) concrete composition, and has high strength (for example, compressive strength).

[0037] The microcapsules used in the present invention, when used as a chemical admixture in a predetermined amount, can provide precast concrete bodies that have high strength and excellent air content stability, resistance to material intrusion, and resistance to freezing and thawing, and preferably all of these properties.

[0038] The concrete composition has resistance to defoaming, and for example, the air content of the composition is stable before and after mixing. Therefore, the concrete composition itself also has excellent stability of air content. For example, the concrete composition can have an air content measured in a test based on JIS A 1128 (Test method for air content of fresh concrete by pressure - air chamber pressure method) within the range of 3 to 6 volume %. This also applies to the precast concrete molded product of the present invention. Furthermore, the concrete composition can have excellent fluidity and workability.

[0039] The precast concrete molded article of the present invention has high strength (for example, compressive strength) and is excellent in at least one, and preferably all, of air content stability, resistance to material intrusion, and resistance to freezing and thawing.

[0040] The precast concrete molded body of the present invention can stably maintain the air content within the range of, for example, 3 to 6% by volume.

[0041] The precast concrete body of the present invention is also capable of inhibiting the penetration of various substances, including water, and has particularly excellent substance penetration resistance not only on the surface but also relatively deep inside. Therefore, the precast concrete body of the present invention can exhibit excellent resistance to water penetration, for example.

[0042] Furthermore, the precast concrete bodies of the present invention have excellent resistance to freezing and thawing, and therefore can exhibit high resistance to weakening caused by repeated freezing and thawing cycles, for example, in winter or in cold regions. [Brief explanation of the drawings]

[0043] [Figure 1] The vertical distribution of the permeability suppression rate up to 50 mm from the top surface is shown. [Figure 2] The apparent and effective diffusion coefficients of chloride ions are shown. [Figure 3] The saltwater permeability is shown for depths of 5 mm and 50 mm from the surface. [Figure 4] The relationship between freeze-thaw cycles and relative dynamic modulus of elasticity is shown. [Figure 5] The relationship between the freeze-thaw cycle and the mass loss rate is shown. DETAILED DESCRIPTION OF THE INVENTION

[0044] As a result of extensive research, the inventors have discovered that a concrete composition containing a predetermined amount of microcapsules having a specific core-shell structure as a chemical admixture can provide a precast concrete product as a hardened product of the composition, which has high strength and excellent air content stability, resistance to material intrusion, and resistance to freeze-thaw cycles, and preferably all of these properties, thereby completing the present invention.

[0045] In the present invention, microcapsules having a specific core-shell structure are not applied to the surface of a hardened concrete composition, but are blended in a predetermined amount into the concrete composition.

[0046] Conventionally, surface impregnation methods and surface treatment methods using anti-absorption agents have been widely used to prevent harmful substances from penetrating into hardened concrete compositions because they are easy to apply and do not damage the appearance. However, depending on the application conditions and deterioration of the impregnated layer over time, the method may not be able to fully demonstrate its inhibitory effect. Furthermore, if cracks extend deeper than the impregnated layer of the anti-absorption agent, the crack surface no longer retains the inhibitory effect on the penetration of harmful substances, and harmful substances will penetrate deep into the hardened concrete through the cracks.

[0047] However, in the present invention, a predetermined amount of microcapsules having a specific core-shell structure is blended into the concrete composition, and therefore the precast concrete molded body of the present invention, which is the hardened product of the composition, can exhibit properties such as preventing the intrusion of substances not only on its surface but throughout its entire interior.

[0048] The present invention will be described in further detail below.

[0049] [Precast concrete molding] A first aspect of the present invention is a precast concrete molded body. A precast concrete molded body is a concrete object that has been preformed into a predetermined shape and is produced in a factory or the like. The precast concrete molded body of the present invention (hereinafter sometimes simply referred to as the "molded body of the present invention") is a hardened concrete composition containing microcapsules having a specific core-shell structure, cement, and at least one type of aggregate, and the amount of the microcapsules mixed is within a predetermined range.

[0050] The concrete composition contains cement and is a hydraulic composition that hardens due to the action of water based on the hydration reaction of cement. The microcapsules have a core-shell structure, and the water-repellent organosilicon material that constitutes the core is encapsulated in the capsule formed by the shell, so they do not inhibit the hydration reaction of cement.

[0051] (microcapsules) The microcapsules to be blended in the concrete composition which will become the molded body of the present invention after hardening are: a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units It has.

[0052] Organosilanes usable as the water-repellent organosilicon material in the present invention preferably contain at least one silicon-bonded hydrolyzable group. This allows the organosilanes to react with components contained in concrete compositions. Examples of such hydrolyzable groups include alkoxy and acyloxy groups. The organosilanes may be, for example, dialkoxysilanes, trialkoxysilanes, or mixtures thereof, or mixtures of at least one of these with organopolysiloxanes. Dialkoxysilanes generally have the formula R2Si(OR')2, and trialkoxysilanes generally have the formula RSi(OR')3, where R in each formula represents an alkyl group, substituted alkyl group, aryl group, or substituted aryl group having 1 to 20 carbon atoms, and each R' represents an alkyl group having 1 to 4 carbon atoms, preferably 1 or 2 carbon atoms. Examples of aryl groups include phenyl groups. The substituent of the substituted alkyl group or the substituted aryl group may be, for example, a halogen atom such as a fluorine atom, an amino group, or an epoxy group. Furthermore, the substituted aryl group may be an alkyl group having 1 to 4 carbon atoms, preferably 1 or 2 carbon atoms, and the substituted alkyl group may be a phenyl group.

[0053] Preferred organosilanes contain at least one silicon-bonded alkyl group having 1 to 30 carbon atoms. By silicon-bonded, we mean that the alkyl group is directly bonded to silicon by a Si-C bond that is not hydrolyzed under normal conditions. Examples of preferred alkyl groups are those having 6 to 18 carbon atoms, such as n-octyl, 2-ethylhexyl, decyl, dodecyl, or hexyl groups. Preferred organosilanes include n-octyltrimethoxysilane, 2-ethylhexyltriethoxysilane, and n-octyltriethoxysilane.

[0054] The organosilane can be partially condensed to an organosilane partial condensate by hydrolysis of the alkoxy or acyloxy hydrolyzable group and siloxane condensation of the resulting Si-OH group. Such organosilane partial condensates can be used as water-repellent organosilicon materials. The degree of condensation of the organosilane partial condensate is preferably limited so that the organosilane still has at least one alkoxy or acyloxy hydrolyzable group per silicon atom.

[0055] The water-repellent organosilicon material used in the present invention may be a branched siloxane resin. The branched siloxane resin has the formula RSiO 3 / 2 Siloxane units (T units) of the formula SiO 4 / 2 and optionally comprising siloxane units (Q units) of the formula RSiO 2 / 2 Siloxane units (D units) of the formula RSiO 1 / 2 wherein each R represents a hydrocarbyl or substituted hydrocarbyl group. Branched siloxane resins have the formula RSiO 3 / 2 It is preferable that the siloxane resin contains the siloxane unit (R is an alkyl group) of the formula:

[0056] Formula RSiO 3 / 2 The branched siloxane resin containing T siloxane units of the formula RSiO may, for example, be a silsesquioxane resin consisting entirely or predominantly of T units. 3 / 2 The R group in the units of formula RSiO may be, for example, an alkyl group. 3 / 2 It may be preferred that some or all of the alkyl groups in the units are alkyl groups having 1 to 30 carbon atoms, for example, alkyl groups having 6 to 18 carbon atoms, such as octyl groups. The branched siloxane resin may be, for example, an n-octyl silsesquioxane resin or an n-octyl methyl silsesquioxane resin. The formula RSiO 3 / 2The R group in the unit may be an aryl group, such as a phenyl group. Branched siloxane resins containing both alkyl and aryl groups may also be used. The branched siloxane resin may be, for example, a phenyl silsesquioxane resin or a phenyl methyl silsesquioxane resin.

[0057] The branched siloxane resin has the formula RSiO 3 / 2 T siloxane units of the formula RSiO 2 / 2 D siloxane units of formula SiO 4 / 2 The branched siloxane resin may comprise Q siloxane units of the formula RSiO. The branched siloxane resin may be, for example, a DT resin, a TQ resin, or a DTQ resin. The branched siloxane resin may alternatively comprise Q siloxane units of the formula RSiO. 1 / 2 M siloxane units and formula SiO 4 / 2 The resin may also be an MQ resin containing Q siloxane units of the formula: Such MQ resins preferably contain as R an alkyl group having 1 to 30 carbon atoms, such as an octyl group.

[0058] The water-repellent organosilicon material, e.g., a water-repellent organosilane, as defined above, may be mixed with an organopolysiloxane having reactive groups, e.g., an organopolysiloxane containing Si—H groups. Any organopolysiloxane present is preferably present in a lesser amount by weight than the water-repellent organosilicon material, as defined above.

[0059] The water-repellent organosilicon material defined above, for example, a water-repellent branched siloxane resin that is solid at room temperature, may be solubilized in a solvent such as an alkylalkoxysilane or polydimethylsiloxane, a hydrocarbon, or the like, having a viscosity of 0.5 to 10,000 mPa.s. The weight ratio of solvent to branched siloxane resin may be in the range of 10:1 to 1:10.

[0060] The microcapsules to be incorporated into the concrete composition have a core of a water-repellent organosilicon material selected from organosilanes, organosilane partial condensates, and branched siloxane resins, and silica units (SiO ) are arranged around the core. 4 / 2It can be produced by forming a shell of a network polymer (silicon-based network polymer) containing silicon-based units.

[0061] For example, the microcapsules to be incorporated into the concrete composition can be produced by adding a tetraalkoxysilane to an aqueous emulsion of a water-repellent organosilicon material selected from organosilanes, organosilane partial condensates, and branched siloxane resins, and then condensing and polymerizing the tetraalkoxysilane at the interface of a dispersed phase (preferably in the form of droplets) consisting of the water-repellent organosilicon material in the emulsion.

[0062] In the above preparation example, tetraalkoxysilane is added to an aqueous emulsion of a water-repellent organosilicon material. The water-repellent organosilicon material is emulsified in an aqueous medium, preferably with the aid of a surfactant. The particle size of the water-repellent organosilicon material emulsion is generally within the range of 0.01 to 500 μm, preferably 0.1 to 50 μm. Alternatively, the emulsion may be a microemulsion with a particle size of 10 to 150 nm. The surfactant may be a cationic, nonionic, or amphoteric surfactant. Cationic and / or amphoteric surfactants, which readily form emulsions with a positive zeta potential, may be preferred. The present inventors have discovered, as described in EP 1471995, that a positive zeta potential promotes condensation and polymerization of the tetraalkoxysilane at the interface of emulsified droplets of the water-repellent organosilane.

[0063] The nonionic surfactants can be used alone or in combination with cationic or amphoteric surfactants, for example, the cationic or amphoteric surfactant can be mixed with up to an equal weight amount of the nonionic surfactant.

[0064] In another preferred embodiment, the method is performed in situ: the water-repellent organosilicon material is mixed with a tetraalkoxysilane, and then an emulsion is formed, for example with a cationic surfactant.

[0065] Examples of cationic surfactants include quaternary ammonium hydroxides, such as octyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, octyldimethylbenzylammonium hydroxide, decyldimethylbenzylammonium hydroxide, didodecyldimethylammonium hydroxide, dioctadecyldimethylammonium hydroxide, tallowtrimethylammonium hydroxide, and cocotrimethylammonium hydroxide, as well as the corresponding salts of these materials. Chloride salts, such as hexadecyltrimethylammonium chloride, may be preferred. Further examples of suitable cationic surfactants include fatty amines and fatty acid amides and their derivatives, basic pyridinium compounds, quaternary ammonium bases of benzimidazoline, and polypropanol polyethanolamines.

[0066] Cationic surfactants containing organosilicon groups can be used, such as N-octadecyl-N,N-dimethyl-trimethoxysilylpropylammonium chloride, of the formula: [ka]

[0067] However, such cationic alkoxysilanes may be more beneficial when added after emulsion formation as a precipitation aid, as described below.

[0068] Examples of suitable amphoteric surfactants include cocamidopropyl betaine, cocamidopropyl hydroxysulfate, cocobetaine, sodium cocoamidoacetate, cocodimethylbetaine, N-coco-3-aminobutyric acid, and imidazolinium carboxyl compounds.

[0069] The above surfactants may be used alone or in combination.

[0070] Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, such as polyethylene glycol long chain (12-14C) alkyl ethers, polyoxyalkylene sorbitan ethers, polyoxyalkylene alkoxylate esters, polyoxyalkylene alkylphenol ethers, ethylene glycol propylene glycol copolymers, polyvinyl alcohols, and alkyl polysaccharides, such as those represented by the structural formula R 1 described in U.S. Pat. No. 5,035,832. 1 -O-(R 2 O) m -(G) n The material (wherein R 1 represents a linear or branched alkyl group, a linear or branched alkenyl group, or an alkylphenyl group; R 2 represents an alkylene group, G represents a reducing sugar, m represents 0 or a positive integer, and n represents a positive integer).

[0071] The concentration of surfactant in the aqueous emulsion of the water-repellent organosilicon material can be 0.01 to 5% by weight of the emulsion, but is preferably less than 2% by weight, most preferably 0.02 to 1% by weight, and especially 0.05 to 0.5% by weight.

[0072] The weight ratio of oil (water-repellent organosilicon material) phase to water phase in the emulsion can generally be 40:1 to 1:50, but a high ratio of water phase is economically disadvantageous, especially when forming an emulsion of microcapsules. Typically, the weight ratio of oil phase to water phase is 2:1 to 1:3.

[0073] The continuous phase of the emulsion may be a mixture of water and a water-miscible organic solvent such as an alcohol or lactam, provided that the continuous phase is immiscible with the water-repellent organosilicon material. The particle size (diameter) of the water-repellent organosilicon material in the emulsion may be reduced, for example, in a shear force generating device such as a homogenizer or microfluidizer, or in a sonolator (ultrasonic mixer) to produce an emulsion of microcapsules with particle sizes of 200 nm to 10 μm, most preferably 2 μm to 5 μm.

[0074] The alkoxy groups in the tetraalkoxysilanes used in the above embodiments preferably contain 1 to 4 carbon atoms, most preferably 1 or 2 carbon atoms. The tetraalkoxysilane may be, for example, tetraethoxysilane (tetraethyl orthosilicate or TEOS). Tetraalkoxysilanes such as TEOS may be used alone or as partial condensates.

[0075] In the above preparation example, when a tetraalkoxysilane is added to an aqueous emulsion of a water-repellent organosilicon material selected from organosilanes, organosilane partial condensates, and branched siloxane resins, the tetraalkoxysilane condenses and polymerizes at the interface of the dispersed phase (preferably in the form of droplets) of the water-repellent organosilicon material in the emulsion.

[0076] That is, the tetraalkoxysilane spontaneously hydrolyzes and condenses to form a silicon-based network polymer, i.e., a three-dimensional network of silicon-based material, around the particles of the water-repellent organosilicon material. Preferably, this three-dimensional network is substantially composed of SiO 4 / 2 It consists of units.

[0077] The particle size of the resulting microcapsules generally corresponds to the particle size of the starting emulsion and may range, for example, from 0.01 to 500 mm, most preferably from 200 nm to 10 mm. When microcapsules with particle sizes of 10 to 500 mm, particularly up to 50 or 100 mm, are required, the aqueous phase of the emulsion preferably contains a thickener, such as polyvinylpyrrolidone, polyvinyl alcohol, bentonite clay, cellulose derivatives, particularly cellulose ethers such as sodium carboxymethylcellulose, lightly crosslinked acrylic polymers, modified starch, alginate, or xanthan gum, to prevent the microcapsules from settling out of the emulsion during or after formation. The thickener is added to the emulsion before the addition of the tetraalkoxysilane.

[0078] In one alternative to the above embodiment, at least one of tri-, di-, and mono-alkoxysilanes may be used in combination with a tetraalkoxysilane to provide organofunctionality to the shell. At least one of tri-, di-, and mono-alkoxysilanes may be reacted with a tetraalkoxysilane to incorporate organofunctional units from the tri-, di-, or mono-alkoxysilane into the network polymer to form the shell of the microcapsule.

[0079] In a further alternative method of the above embodiment, a cationic alkoxysilane may be used in combination with a tetraalkoxysilane. N-octadecyl-N,N-dimethyl-trimethoxysilylpropylammonium chloride is one example of such a cationic alkoxysilane. The cationic alkoxysilane can improve the behavior of the microcapsules in the composition. The cationic alkoxysilane can be added to the aqueous emulsion before or simultaneously with the tetraalkoxysilane. The cationic alkoxysilane can react with the tetraalkoxysilane to incorporate siloxane units derived from the cationic alkoxysilane into the network polymer, forming the shell of the microcapsule.

[0080] The tetraalkoxysilane may be added to the emulsion of water-repellent organosilicon material as a neat solution or as a solution in an organic solvent. The tetraalkoxysilane and emulsion are generally mixed under shear during addition and subsequent condensation to form a silicon-based polymer shell on the surface of the emulsion droplets. Mixing can be achieved, for example, by stirring, but it is preferred to subject the emulsion and tetraalkoxysilane to high shear in a rotor-stator mixer, such as a Silverson™ mixer, either during the addition of the tetraalkoxysilane or after the addition of the tetraalkoxysilane and before the completion of microcapsule formation. High shear mixing immediately after the addition of the tetraalkoxysilane is preferred. This results in microcapsules with reduced particle size and appears to promote polymerization of almost all of the tetraalkoxysilane at the interface of the emulsion droplets.

[0081] The condensation reaction of tetraalkoxysilane can be carried out at acidic, neutral, or basic pH. The condensation reaction is generally carried out at room temperature and atmospheric pressure, but may be carried out at elevated temperatures, for example, up to 95°C, and with increased or decreased pressure, for example, under vacuum, to volatilize the volatile alcohol produced during the condensation reaction. The weight ratio of the water-repellent organosilicon material to the tetraalkoxysilane is preferably at least 1:1, and often at least 2:1, for example, 3:1 to 50:1. Smaller microcapsules, such as those formed from microemulsions, generally have a lower ratio of organosilane to water-reactive silicon compound.

[0082] A catalyst for the hydrolysis and / or condensation of tetraalkoxysilanes may be used to form silicon-based network polymers. The catalyst is preferably an oil-soluble organometallic compound, such as an organotin compound, particularly an organotin compound, such as a diorganotin diester, e.g., dimethyltin di(neodecanoate), dibutyltin dilaurate, or dibutyltin diacetate; a tin carboxylate, e.g., stannous octoate; or an organotitanium compound, such as tetrabutyl titanate. The organotin catalyst may be used, for example, at 0.05 to 2 wt. % relative to the tetraalkoxysilane. The organotin catalyst has the advantage of effective catalytic activity at neutral pH. The catalyst is most preferably mixed with the water-repellent organosilicon material prior to emulsification, since this promotes condensation of the tetraalkoxysilane on the surface of the emulsified lipophilic droplets. Alternatively, a catalyst can be added to the emulsion before, simultaneously with, or after the addition of the tetraalkoxysilane to harden the formed silicon-based polymer shell and make it more impermeable. However, encapsulation can be achieved without a catalyst. The catalyst (if used) can be added neat, as a solution in an organic solvent such as a hydrocarbon, alcohol, or ketone, or as a multiphase system such as an emulsion or suspension.

[0083] The product of the hydrolysis and condensation of the tetraalkoxysilane is an aqueous suspension of microcapsules. The aqueous continuous phase in the aqueous suspension can contain a water-miscible organic solvent, typically an alcohol such as ethanol, which is generated by hydrolysis of the Si-bonded alkoxy groups. It can be advantageous to use the suspension of microcapsules directly without separating the microcapsules from the suspension.

[0084] In other events, it may be advantageous to work with the microcapsules isolated from the aqueous medium. Recovery or isolation of the microcapsules from such a suspension can be achieved by any known liquid removal technique, for example, spray drying, spray chilling, filtration, oven drying or freeze drying.

[0085] The microcapsules may be further surface treated, either in suspension or in isolated (dried) form, by adding tri-, di-, or monoalkoxysilanes, which can modify the compatibility, pH resistance, and mechanical strength of the microcapsules.

[0086] Preferably, the microcapsules are in the form of an aqueous suspension. The concentration of the microcapsules in the aqueous suspension is not particularly limited, but can be, for example, 10 to 50% by weight, 20 to 40% by weight, or 25 to 35% by weight.

[0087] In the present invention, microcapsules having a specific core-shell structure are not applied to the surface of a hardened concrete composition, but are incorporated into the concrete composition.

[0088] The microcapsules react with alkali, silica, and the like derived from cement, aggregate, and other components contained in the concrete composition to form a network structure containing siloxane bonds on the surface of the cement particles and the molded body of the present invention, which is a hardened product of the concrete composition. In the network structure, hydrophobic groups such as alkyl groups are arranged toward the outside, forming a water-repellent layer. This water-repellent layer covers the surfaces of the cement particles and the molded body of the present invention, as well as the surfaces of the pores or voids dispersed within the molded body, thereby providing the molded body with high resistance to the penetration of substances, particularly high waterproofing, on both the surface and inside.

[0089] Generally, conventional silane-based water absorption inhibitors are applied to the surface of a hardened concrete composition, forming a water-repellent layer of hydrophobic inorganic crystals on the surface and within a limited range extending approximately 1 cm from there. However, the microcapsules used in the present invention form a water-repellent layer on the surface of the hardened concrete and extending to a depth of more than 1 cm from there. Therefore, even if a crack has progressed from the surface of the concrete to a depth of more than 1 cm, it is possible to prevent water and harmful substances from penetrating into the concrete, and to prevent rust and corrosion of the internal reinforcing bars, which can lead to a decrease in the load-bearing capacity of the concrete.

[0090] Furthermore, the water-repellent layer prevents the intrusion of water and the like from the outside without filling or blocking the pores or voids on the surface and inside of the molded body of the present invention, and also dissipates unnecessary moisture present inside the molded body that is not used in the hydration reaction of the binder such as the cement particles as water vapor to the outside of the molded body, thereby also having the effect of suppressing the progression of deterioration such as alkali-silica reaction that occurs when moisture remains inside the molded body.

[0091] The concrete composition that hardens to form the molded body of the present invention contains 0.01 to less than 0.5 parts by weight of microcapsules per 100 parts by weight of cement. The amount of microcapsules is preferably 0.02 to 0.4 parts by weight, more preferably 0.03 to 0.35 parts by weight, even more preferably 0.04 to 0.3 parts by weight, even more preferably 0.05 to 0.25 parts by weight, and even more preferably 0.06 to 0.21 parts by weight per 100 parts by weight of cement. This allows for excellent strength of the molded body of the present invention, stability of the air content of the concrete composition and its hardened product, and at least one, preferably all, of the molded body of the present invention's resistance to substance penetration and freeze-thaw resistance.

[0092] If the amount of microcapsules used in the concrete composition is less than 0.01 parts by mass per 100 parts by weight of cement, the amount is too small to achieve excellent strength of the molded body of the present invention, and at least one, preferably all, of the air content stability of the concrete composition and the molded body of the present invention, and the resistance to substance penetration and freeze-thaw resistance of the molded body of the present invention.On the other hand, if the amount of microcapsules used in the concrete composition is 0.5 parts by mass or more per 100 parts by weight of cement, the strength or freeze-thaw resistance of the hardened product will decrease, making it difficult to achieve excellent strength of the molded body of the present invention, and at least one, preferably all, of the air content stability, resistance to substance penetration and freeze-thaw resistance, and also resulting in poor economic efficiency.

[0093] (cement) The concrete composition includes cement.

[0094] The cement blended into the concrete composition is not particularly limited, and examples thereof include ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, sulfate-resistant Portland cement, moderate-heat Portland cement, low-heat Portland cement, white Portland cement, ultra-rapid-hardening Portland cement, expansive cement, acidic phosphate cement, self-hardening cement, lime slag cement, blast-furnace cement, high-sulfate slag cement, fly ash cement, Keene's cement, pozzolanic cement, alumina cement, Roman cement, white cement, magnesia cement, slag cement, calcium aluminate, silica cement, silica fume cement, jet cement, ecocement, gypsum or hemihydrate gypsum, and latent hydraulic substances such as blast-furnace slag. These cements can be used alone or in combination of one or more selected from these.

[0095] The amount of cement in the concrete composition is not particularly limited, but can be, for example, 1 to 50% by weight, 5 to 40% by weight, 10 to 30% by weight, or 15 to 20% by weight, based on the total weight of the composition.

[0096] (aggregate) The concrete composition may further comprise at least one aggregate.

[0097] The aggregate that can be blended into the concrete composition is not particularly limited, and for example, a mixture of coarse aggregate and fine aggregate that is generally used in the fields of civil engineering or construction can be used.

[0098] Examples of coarse aggregate include river gravel, mountain gravel, sea gravel, crushed stone, and blast furnace slag coarse aggregate.

[0099] Examples of fine aggregate include river sand, mountain sand, sea sand, and blast furnace slag fine aggregate.

[0100] The amount of aggregate in the concrete composition is not particularly limited, but can be, for example, 10 to 1000 parts by weight, 50 to 800 parts by weight, or 100 to 500 parts by weight per 100 parts by weight of cement.

[0101] (Other ingredients) The concrete composition may contain other components commonly used in the fields of civil engineering or construction, such as air-entraining agents, water-reducing agents (preferably air-entraining water-reducing agents, particularly high-performance air-entraining water-reducing agents), waterproofing agents, water-resistant agents, antifoaming agents, curing agents, release agents, shrinkage-reducing agents, surface aesthetic improvers, set accelerators, set retarders, self-leveling agents, paints, surface repair materials, thickeners, expanding agents, rust inhibitors, inorganic fibers, organic fibers, organic polymers, silica fume, fly ash, and ground granulated blast furnace slag.

[0102] Other components include water. The water is not particularly limited, but examples include tap water, industrial water, groundwater, river water, rainwater, distilled water, and high-purity water for chemical analysis (ultrapure water, pure water, ion-exchanged water). It is preferable that the water does not contain impurities such as chloride ions, sodium ions, and potassium ions that adversely affect the hydration reaction of cement in the concrete composition.

[0103] The amount of water in the concrete composition is not particularly limited, but can be, for example, 25 to 75 parts by weight, 30 to 70 parts by weight, 35 to 65 parts by weight, or 40 to 60 parts by weight per 100 parts by weight of cement.

[0104] (Air content stability) The concrete composition has excellent stability of the amount of air contained therein.

[0105] The concrete composition preferably has an air content of 3 to 6% by volume as measured in a test based on JIS A 1128 (Test method for air content in fresh concrete by pressure - air chamber pressure method). The air content specified by the Japan Society of Civil Engineers and the Architectural Institute of Japan is 4.5±1.5% by volume, and the concrete composition satisfies this standard.

[0106] Furthermore, the concrete composition is difficult to degas even when mixed. Therefore, the concrete composition can stably contain a predetermined amount of air before and after mixing. Usually, the concrete composition is hardened after being mixed, so the concrete composition and its hardened product can stably contain approximately the same amount of air.

[0107] The concrete composition becomes the molded article of the present invention upon hardening. That is, the molded article of the present invention is a hardened product of the concrete composition. Here, "hardening" means that the concrete composition reacts with water to set or solidify, and "hardened product" means the object after hardening is completed.

[0108] (Air content stability) The molded body of the present invention preferably has an air content of 3 to 6% by volume. The air content specified by the Japan Society of Civil Engineers and the Architectural Institute of Japan is 4.5±1.5% by volume, and the molded body of the present invention satisfies this requirement.

[0109] The molded article of the present invention can maintain a stable amount of air content.

[0110] The molded article of the present invention has fine bubbles (pores or voids) inside due to the contained air. The microcapsules form a water-repellent layer on the surface without destroying the bubbles (pores or voids). Therefore, when the molded article of the present invention contains moisture, the necessary amount of fine pores or voids (preferably 3 to 6 volume % air) required to absorb the expansion pressure generated when the moisture freezes and expands in volume is maintained. Therefore, the molded article of the present invention can exhibit excellent freeze-thaw resistance, for example, as described below.

[0111] (strength) The molded article of the present invention can exhibit excellent strength. For example, the molded article of the present invention can have excellent compressive strength and / or tensile strength. Therefore, the molded article of the present invention has high durability and load resistance.

[0112] For example, the molded article of the present invention can have a compressive strength ratio of more than 100% after 7 days of air curing in a compression test based on JIS A 1108 (Method for testing compressive strength of concrete) and JIS A 6204 (Chemical admixtures for concrete).

[0113] The above compressive strength ratio is calculated using the following formula for calculating the compressive strength ratio of concrete specified in JIS A 6204 (chemical admixtures for concrete): Compressive strength ratio = compressive strength of the molded product of the present invention, which is a hardened product of a concrete composition containing microcapsules, measured according to JIS A 1108 (Testing method for compressive strength of concrete) ÷ compressive strength of a hardened product of a concrete composition not containing microcapsules, measured according to JIS A 1108 (Testing method for compressive strength of concrete) It can be calculated as follows.

[0114] (Prevention of substance intrusion) The molded article of the present invention can prevent or inhibit the penetration of various substances, such as water and chloride ions, into the molded article.

[0115] The penetration suppression rate is calculated by the following formula, which calculates the suppression rate for deterioration factors specified in the Surface Protection Method Design and Construction Guidelines (Draft) Manual for Each Work Type, specified by the Japan Society of Civil Engineers: Performance ratio (%) of each test piece to the original condition test piece = (Test piece performance ÷ Original condition test piece performance) × 100 Suppression rate for each deterioration factor (%) = 100 - performance ratio for each original specimen (%) The deterioration factors include, for example, water and chloride ions, and the performance includes water permeability, water absorption rate, moisture permeability, carbonation depth, and chloride ion penetration depth.

[0116] For example, in a water permeability test based on JIS A 6909 (Architectural finishing coating materials (water permeability test method B)) and JSCE-K571 (Test method (draft) for surface impregnation materials), the molded article of the present invention can have a surface water permeability inhibition rate of 40% or more, preferably 50% or more, more preferably 70% or more after standard underwater curing for 28 days, and a water permeability inhibition rate of 60% or more within 10 mm or more, preferably 30 mm or more, more preferably 50 mm or more from the surface.

[0117] The molded article of the present invention has low water permeability, and therefore, deterioration of the physical properties of the molded article due to water penetration can be suppressed.

[0118] (freeze-thaw resistance) The molded article of the present invention can have a relative dynamic modulus of elasticity (durability index) of 80% or more, or a mass loss rate of 3.0% or less, after 300 freeze-thaw cycles after 4 weeks of standard underwater curing, in a freeze-thaw test based on JIS A 1148 (Freeze-thaw test for concrete (Method A)) and JIS A6204 (Chemical admixtures for concrete).

[0119] As described above, the molded article of the present invention has fine bubbles (pores) formed inside due to the air contained therein, and the microcapsules form a water-repellent layer on the surface of the bubbles (pores) without destroying them. Therefore, when the molded article of the present invention contains water, the necessary amount of fine pores or voids (preferably 3 to 6 volume % air) required to absorb the expansion pressure generated when the water freezes and expands in volume is maintained. Therefore, the molded article of the present invention can exhibit excellent freeze-thaw resistance. In other words, the molded article of the present invention has high resistance to weakening caused by repeated freeze-thaw cycles.

[0120] Furthermore, repeated freezing and thawing generally causes the surface of the molded body to flake off, which can result in, for example, the steel being exposed and corroding in the case of a molded body made of reinforced concrete. However, the molded body of the present invention has a low mass loss rate, which can prevent such inconvenience.

[0121] The molded article of the present invention may have a spacing factor of 330 μm or less, calculated based on ASTM C 457 (linear traverse method or modified point count method using a microscope).

[0122] The molded article of the present invention has fine bubbles (pores) inside, and the bubbles (pores) are uniformly distributed, so that the molded article of the present invention can exhibit uniform physical properties, such as resistance to substance penetration and freeze-thaw resistance.

[0123] [Water contact structure] A second aspect of the present invention is a waterway structure, coastal structure or marine structure made of the molded article of the present invention.

[0124] The explanation regarding the molded body in the first aspect of the present invention applies to the above molded body and its constituent elements or components.

[0125] Concrete pipes, culverts and the like are conceivable as waterway structures made of the molded article of the present invention, but the invention is not limited to these.

[0126] Coastal structures made of the molded article of the present invention may include wave-dissipating blocks, breakwaters, seawalls, etc., but are not limited to these.

[0127] Marine structures made of the molded article of the present invention are envisioned to include offshore oil wells, but are not limited thereto.

[0128] The concrete structures such as the above-mentioned waterway structures, coastal structures and marine structures include not only so-called reinforced concrete structures but also steel-concrete composite structures such as steel-framed concrete structures, steel-framed reinforced concrete structures and concrete-filled steel pipe structures.

[0129] Waterway structures, coastal structures, and marine structures made from the molded article of the present invention have excellent strength and at least one of, and preferably all of, air content stability, substance intrusion prevention, and freeze-thaw resistance, allowing for wide use regardless of environmental conditions or construction conditions. Therefore, waterway structures, coastal structures, and marine structures made from the molded article of the present invention are effective for construction of buildings and other structures that require both frost resistance and salt damage resistance. Furthermore, waterway structures, coastal structures, and marine structures made from the molded article of the present invention can be used as at least a portion of waterway structures, coastal structures, and marine structures in cold regions where frost resistance, salt damage resistance, and fatigue resistance are required. Therefore, for example, when the present invention is applied to structures in environments that may be subject to combined frost damage and salt damage, such as coastal and marine structures in cold, snowy regions, the excellent frost resistance and salt damage resistance are exhibited, thereby extending the service life of the structures compared to structures made from ordinary mortar or concrete.

[0130] [Road structures] A third aspect of the present invention is a road structure comprising the molded article of the present invention.

[0131] The explanation regarding the molded body in the first aspect of the present invention applies to the above molded body and its constituent elements or components.

[0132] Road structures made of the molded article of the present invention include roads, tunnels, bridges, bridge piers, etc., but are not limited to these.

[0133] Concrete structures such as the above road structures include not only so-called reinforced concrete structures, but also steel-concrete composite structures such as steel-framed concrete structures, steel-framed reinforced concrete structures, and concrete-filled steel pipe structures.

[0134] Road structures made from the molded article of the present invention have excellent strength and at least one of, and preferably all of, air content stability, substance intrusion resistance, and freeze-thaw resistance, allowing for wide use regardless of environmental or construction conditions. Therefore, road structures made from the molded article of the present invention are effective in the construction of buildings and other structures that require both frost resistance and salt damage resistance, as well as in locations where frost damage, salt damage, and fatigue degradation may occur in combination, such as expressways in snowy, cold, mountainous regions where chloride-based antifreeze or snow-melting agents are sprayed in winter. Furthermore, road structures made from the molded article of the present invention can be used as at least a portion of road structures in cold regions where frost resistance, salt damage resistance, and fatigue resistance are required. Therefore, when the present invention is applied to structures in environments where frost damage and salt damage may be combined, such as expressways in snowy, cold regions, the excellent frost resistance and salt damage resistance are exhibited, thereby extending the service life of the structure compared to structures made from ordinary mortar or concrete.

[0135] [Retaining wall structure] A fourth aspect of the present invention is a retaining wall structure made of the molded article of the present invention.

[0136] The explanation regarding the molded body in the first aspect of the present invention applies to the above molded body and its constituent elements or components.

[0137] Retaining wall structures made of the molded article of the present invention include block retaining walls, gravity retaining walls, L-shaped retaining walls, etc., but are not limited to these.

[0138] Concrete structures such as the above-mentioned retaining wall structures include not only so-called reinforced concrete structures, but also steel-concrete composite structures such as steel-framed concrete structures, steel-framed reinforced concrete structures, and concrete-filled steel pipe structures.

[0139] A retaining wall structure made of the molded article of the present invention has excellent strength and at least one of, and preferably all of, air content stability, substance intrusion prevention, and freeze-thaw resistance, and can therefore be widely used regardless of environmental conditions or construction conditions. Therefore, a retaining wall structure made of the molded article of the present invention can be used as at least a part of a retaining wall structure in a cold region where frost resistance, salt damage resistance, and fatigue resistance are required. Therefore, for example, when the present invention is applied to a structure in an environment where frost damage and salt damage may be combined, excellent frost damage resistance and salt damage resistance are exhibited, thereby extending the service life of the structure compared to structures made of ordinary mortar or concrete.

[0140] [Method of manufacturing precast concrete bodies] A fifth aspect of the present invention is a method for producing a precast concrete body.

[0141] The manufacturing method of the present invention comprises: a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units A preparation step of preparing an unhardened concrete composition containing microcapsules having a core-shell structure having the following structure: A hardening and shaping step of hardening and shaping the unhardened concrete composition. A method for producing a precast concrete body, comprising: the unhardened concrete composition comprises cement and at least one aggregate; In the preparation step, the microcapsules are mixed in an amount of 0.01 to less than 0.5 parts by weight per 100 parts by weight of the cement.

[0142] The explanations regarding the microcapsules and cement in the first aspect of the present invention apply to the above microcapsules and their components or constituents, as well as the cement and aggregate.

[0143] The form of preparation of the unhardened concrete composition containing microcapsules in the preparation step is not particularly limited. For example, the microcapsules themselves may be added to the unhardened concrete composition, or the microcapsules may be added to the unhardened concrete composition in the form of an aqueous suspension.

[0144] The unhardened concrete composition may contain water. Therefore, for example, in the preparation step, water may be added to the materials constituting the concrete, such as cement and aggregate, and then the microcapsules are added. It is preferable to mix them appropriately after each addition. Also, in the preparation step, water and the microcapsules may be added together to the materials constituting the concrete, such as cement and aggregate, and then mixed. Furthermore, in the preparation step, water may be added after the microcapsules are added to the materials constituting the concrete, such as cement and aggregate. It is preferable to mix them appropriately after each addition. Note that when the microcapsules are added in the form of an aqueous suspension, the water is different from the water that is the medium of the aqueous suspension.

[0145] The amount of water is not particularly limited, but can be, for example, 25 to 75 parts by weight, 30 to 70 parts by weight, 35 to 65 parts by weight, or 40 to 60 parts by weight per 100 parts by weight of cement. In particular, when the precast concrete molding has a viscosity of 20 to 55 N / mm 2 In order to exert the above compressive strength, the amount of water is preferably 35 to 65 parts by weight, more preferably 40 to 60 parts by weight, per 100 parts by weight of cement.

[0146] The hardening and molding step is a step of hardening the unhardened concrete composition (ready-mixed concrete composition) into a predetermined shape, and can be carried out by a method commonly used in the art. The hardening step can be carried out, for example, by allowing a hardening reaction between cement and water to proceed in air or water in a mold of a predetermined shape. Here, if the unhardened concrete composition does not contain water, water is added to the composition in the hardening and molding step.

[0147] The hardening and molding step may be carried out by pouring the unhardened concrete composition into a mold of a predetermined shape and then curing it for a predetermined period of time.

[0148] The amount of microcapsules to be mixed is preferably 0.02 to 0.4 parts by weight per 100 parts by weight of cement, more preferably 0.03 to 0.35 parts by weight, even more preferably 0.04 to 0.3 parts by weight, even more preferably 0.05 to 0.25 parts by weight, and even more preferably 0.06 to 0.21 parts by weight.

[0149] The precast concrete bodies obtained by the manufacturing method of the present invention have high strength (e.g., compressive strength) and are excellent in at least one, and preferably all, of air content stability, resistance to material intrusion, and resistance to freezing and thawing.

[0150] For example, the air content of the precast concrete molded body obtained by the manufacturing method of the present invention can be in the range of 3 to 6% by volume.

[0151] Furthermore, the precast concrete molded body obtained by the manufacturing method of the present invention can have a compressive strength ratio of more than 100% after 7 days of air curing in a compression test based on JIS A 1108 (Method for testing compressive strength of concrete) and JIS A 6204 (Chemical admixtures for concrete).

[0152] Furthermore, in a water permeability test based on JIS A 6909 (Architectural finishing coating materials (water permeability test method B)) and JSCE-K571 (Test method (draft) for surface impregnation materials), the precast concrete bodies obtained by the manufacturing method of the present invention have a surface water permeability suppression rate of 40% or more, preferably 50% or more, and more preferably 70% or more after 28 days of standard underwater curing, and a water permeability suppression rate of 60% or more within 10 mm or more, preferably 30 mm or more, and more preferably 50 mm or more from the surface.

[0153] Furthermore, the precast concrete bodies obtained by the manufacturing method of the present invention can have a relative dynamic modulus of elasticity (durability index) of 80% or more, or a mass loss rate of 3.0% or less, after 300 freeze-thaw cycles after four weeks of standard underwater curing, in a freeze-thaw test based on JIS A 1148 (Freeze-thaw test for concrete (Method A)) and JIS A6204 (Chemical admixtures for concrete).

[0154] Furthermore, the precast concrete molded article obtained by the manufacturing method of the present invention can have an air-void spacing coefficient of 330 μm or less, calculated based on ASTM C 457 (linear traverse method or modified point count method using a microscope).

[0155] [Method for improving physical properties] A sixth aspect of the present invention is a method for improving the strength (eg, compressive strength) and at least one, preferably all, of the resistance to material intrusion, freeze-thaw resistance, and air content stability of a precast concrete body.

[0156] The improvement method of the present invention is a method for improving at least one, preferably all, of the strength (e.g., compressive strength) of a precast concrete body, and the resistance to substance penetration, freeze-thaw resistance, and air content stability, comprising: a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units A blending step of blending microcapsules having a core-shell structure having the above-mentioned structure into a concrete composition for the precast concrete molded body, the concrete composition comprises cement and at least one aggregate; In the blending step, the microcapsules are blended in an amount of 0.01 to less than 0.5 parts by weight per 100 parts by weight of the cement.

[0157] The explanations regarding the microcapsules and cement in the first aspect of the present invention apply to the above microcapsules, their constituent elements or components, and cement.

[0158] The amount of microcapsules to be mixed is preferably 0.02 to 0.4 parts by weight per 100 parts by weight of cement, more preferably 0.03 to 0.35 parts by weight, even more preferably 0.04 to 0.3 parts by weight, even more preferably 0.05 to 0.25 parts by weight, and even more preferably 0.06 to 0.21 parts by weight.

[0159] The improvement method of the present invention can improve the strength (e.g., compressive strength) of precast concrete bodies, as well as at least one, and preferably all, of the air content stability, resistance to material intrusion, and resistance to freeze-thaw cycles.

[0160] In other words, when comparing a precast concrete body to which the method of the present invention has not been applied with a precast concrete body to which the method of the present invention has been applied, the physical properties of the latter are improved compared to the former in terms of strength (e.g., compressive strength), and at least one, and preferably all, of air content stability, resistance to substance intrusion, and freeze-thaw resistance.

[0161] For example, the improvement method of the present invention can reduce the air content of precast concrete bodies to within the range of 3 to 6% by volume.

[0162] Furthermore, the improvement method of the present invention makes it possible to produce precast concrete bodies having a compressive strength ratio of more than 100% after 7 days of air curing in a compression test based on JIS A 1108 (Method for testing compressive strength of concrete) and JIS A 6204 (Chemical admixtures for concrete).

[0163] Furthermore, the improvement method of the present invention can improve the ability of precast concrete bodies to be prevented from being invaded by various substances, such as water and chloride ions.

[0164] For example, the improvement method of the present invention can produce a precast concrete product that, after 28 days of standard underwater curing, in a water permeability test based on JIS A 6909 (Architectural finishing coating materials (water permeability test method B)) and JSCE-K571 (Test method (draft) for surface impregnating materials), has a surface water permeability suppression rate of 40% or more, preferably 50% or more, and more preferably 70% or more, and that has a water permeability suppression rate of 60% or more within a depth of 10 mm or more, preferably 30 mm or more, and more preferably 50 mm from the surface.

[0165] Furthermore, the improvement method of the present invention can produce precast concrete moldings that have a relative dynamic modulus of elasticity (durability index) of 80% or more or a mass loss rate of 3.0% or less after 300 freeze-thaw cycles after four weeks of standard underwater curing in freeze-thaw tests based on JIS A 1148 (Freeze-thaw test for concrete (Method A)) and JIS A6204 (Chemical admixtures for concrete).

[0166] Furthermore, the improvement method of the present invention can produce a precast concrete molded article having an air-void spacing coefficient of 330 μm or less as calculated based on ASTM C 457 (linear traverse method or modified point count method using a microscope). [Example]

[0167] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples in any way.

[0168] [Materials used] Portland cement: Ordinary Portland cement manufactured by Sumitomo Osaka Cement Co., Ltd. Compliant with JIS R 5210. Density: 3.15 g / cm 3 . Coarse aggregate: crushed stone from Kanayama, Ichikikushikino City. Compliant with JIS A 5005 crushed stone 2005. Density: 2.61g / cm 3 . Fine aggregate: crushed sand from Kanayama, Ichikikushikino City, and crushed sand from Shimizu, Kawabe-cho, Minamikyushu City. Complies with gravel and sand specified in Appendix A of JIS A 5308. Density: 2.61 g / cm 3 and 2.66 g / cm 3 Calcium carbonate manufactured by Sanyu Co., Ltd. Complies with the Japan Concrete Institute's "Quality Standards for Fine Limestone Powder for Concrete (Draft)." Density: 2.71 g / cm 3 . Water reducing agent Sikament 2200 (manufactured by Sika Japan Co., Ltd.). Compliant with JIS A 6204. Air-entraining agent: Sika AER-50 (manufactured by Sika Japan Co., Ltd.). Compliant with JIS A 6204. Silicon-based multi-functional admixture: DOWSIL IE 6686 manufactured by Dow Toray Industries, Inc., active solid content 30% by weight

[0169] [Example 1] According to JIS A 1138 (Laboratory concrete manufacturing methods), mixing water, calcium carbonate, coarse aggregate, fine aggregate, water-reducing agent, and air-entraining agent (AD2) were added in proportions of 170 kg of mixing water (W), 216 kg of calcium carbonate (FU), 973 kg of coarse aggregate (G), 650 kg of fine aggregate (S), 6.75 kg of water-reducing agent (AD1), and 0.04 kg of air-entraining agent (AD2) per 328 kg of ordinary Portland cement (C), and the mixture was kneaded in a forced twin-screw mixer to obtain a base composition. A silicon-based multifunctional admixture was added to the resulting base composition in a ratio of 0.2 parts by weight per 100 parts by weight of ordinary Portland cement (C) and mixed to obtain a cement (concrete) composition. DOWSIL IE 6686, a commercially available silicone emulsion product with a core-shell structure, was used as the silicon-based multifunctional admixture. DOWSIL IE 6686 has an active solid content of 30% by weight, so the core-shell microcapsules were included in an amount of 0.06 parts by weight per 100 parts by weight of cement (C).

[0170] [Example 2] A cement (concrete) composition was obtained in the same manner as in Example 1, except that 0.5 parts by weight of the silicon-based multifunctional admixture (X) was added to 100 parts by weight of ordinary Portland cement (C) and mixed. The microcapsules having a core-shell structure were contained in an amount of 0.15 parts by weight per 100 parts by weight of cement (C).

[0171] [Example 3] A cement (concrete) composition was obtained in the same manner as in Example 1, except that 0.7 parts by weight of silicon-based multifunctional admixture (X) was added to 100 parts by weight of ordinary Portland cement (C) and mixed. The microcapsules having a core-shell structure were contained in an amount of 0.21 parts by weight per 100 parts by weight of cement (C).

[0172] [Comparative Example 1] The base composition used in Example 1 was used as is.

[0173] Comparative Example 2 A cement (concrete) composition was obtained in the same manner as in Example 2, except that an admixture (Y) consisting of a silane compound was used instead of the silicon-based multifunctional admixture (X). The admixture (Y) consisting of the silane compound has the same overall composition as the silicon-based multifunctional admixture (X), but differs in that it does not have a core-shell structure.

[0174] Table 1 shows the unit amounts of materials used to prepare the cement (concrete) compositions of Examples 1 to 3 and Comparative Examples 1 and 2.

[0175] [Table 1]

[0176] [evaluation] 1. Physical properties of cement (concrete) composition before hardening Regarding the cement (concrete) compositions before hardening in Examples 1 to 3 and Comparative Examples 1 and 2, Slump flow was measured according to JIS A 1150 (method of testing concrete slump flow). The air content was measured in accordance with JIS A 1128 (Test method for air content of fresh concrete by pressure - air chamber pressure method). The results are shown in Table 2.

[0177] [Table 2]

[0178] 2. Physical properties of cement (concrete) composition after hardening (1) Water permeability suppression rate In accordance with JIS A 1132 (method of preparing specimens for strength tests of concrete), cylindrical specimens (standard underwater curing for 28 days) were prepared by hardening the cement (concrete) compositions of Examples 1 to 3 and Comparative Examples 1 and 2, and the water permeability was measured using these specimens in accordance with JIS A 6909 (architectural finishing coating materials (water permeability test method B)) and JSCE-K 571 (test method (draft) for surface impregnation materials). The permeability was first measured on the top surface (circular) of the test specimen, then the test specimen was cut and polished every 5 mm in the height direction from the top surface, and the permeability was measured up to a position 50 mm below the top surface of the test specimen. From the measured values, the permeability ratio was determined using the following formula based on the calculation formula specified in JSCE-K 571 (Test method for surface impregnated materials (draft)), and the permeability inhibition rate was calculated using the following formula. Permeability ratio (%) = Permeability of each specimen of Examples 1 to 3 and Comparative Example 2 / Permeability of specimen of Comparative Example 1 × 100 Water permeability suppression rate (%) = 100 - water permeability ratio (%) The closer the water permeation inhibition rate is to 100(%), the more difficult the water permeation is compared to Comparative Example 1. The results are shown in Table 3 and FIG.

[0179] (2) Compressive strength ratio In accordance with JIS A 1132 (Method of preparing specimens for strength tests of concrete), JIS A 1108 (Method of testing compressive strength of concrete), and JIS A 6204 (Chemical admixtures for concrete), specimens were prepared by hardening the cement (concrete) compositions of Examples 1 to 3 and Comparative Examples 1 and 2 (air curing for 7 days), and compressive strength tests were conducted using these specimens. The compressive strength ratio was calculated from the measured compressive strength values ​​using the following formula based on the calculation formula specified in JIS A 6204. Compressive strength ratio = compressive strength of the hardened products of the compositions of Examples 1 to 3 and Comparative Example 2 measured according to JIS A 1108 (Testing method for compressive strength of concrete) ÷ compressive strength of the hardened product of Comparative Example 1 measured according to JIS A 1108 (Testing method for compressive strength of concrete) The results are shown in Table 3.

[0180] (3) Durability index In accordance with JIS A 1148 (Freezing and thawing test of concrete (Method A)) and JIS A 6204 (Chemical admixtures for concrete), specimens (standard underwater curing for 4 weeks) were prepared by hardening the cement (concrete) compositions of Examples 1 to 3 and Comparative Examples 1 and 2, and an underwater freeze-thaw test was conducted using these specimens to measure the primary resonance frequency and mass of the flexural vibration of the specimens. From these measurements, the relative dynamic modulus of elasticity and mass loss rate after 300 freeze-thaw cycles were calculated using the formula specified in JIS A 1148 (Freeze-thaw test for concrete (Method A)). The results are shown in Table 3 and in Figures 4 and 5, respectively.

[0181] (4) Bubble spacing coefficient In accordance with ASTM C 457 (linear traverse method using a microscope or modified point count method), specimens were prepared by hardening the cement (concrete) compositions of Examples 1 to 3 and Comparative Examples 1 and 2, and the air void spacing coefficient was calculated using the linear traverse method. The results are shown in Table 3.

[0182] [Table 3]

[0183] (5) Apparent and effective diffusion coefficients of chloride ions In accordance with JSCE-G571-2013 (Testing method for the effective diffusion coefficient of chloride ions in concrete by electrophoresis), specimens were prepared by hardening the cement (concrete) compositions of Examples 1 to 3 and Comparative Examples 1 and 2, and electrophoresis was performed using these specimens to calculate the apparent diffusion coefficient and effective diffusion coefficient of chloride ions. The results are shown in Table 4 and FIG.

[0184] [Table 4]

[0185] (6) Saltwater permeability In accordance with JIS A 6909 (Architectural Finishing Coating Materials (Water Permeability Test Method B)) and JSCE-K571 (Test Method for Surface Impregnation Materials (Draft)), test specimens were prepared by hardening the cement (concrete) compositions of Example 2 and Comparative Examples 1 and 2, and a water permeability test was carried out using these specimens. After 28 days of standard underwater curing, the saltwater permeability was measured at depths of 5 mm from the surface and 50 mm from the surface. The results are shown in Figure 3.

[0186] In Examples 1 to 3, the air content was 4.5±1.5%, which was within the range specified by the Japan Society of Civil Engineers and the Architectural Institute of Japan, and a high water permeability suppression rate was achieved without substantially impairing the high compressive strength ratio, relative dynamic modulus of elasticity, and frost resistance indicated by the air void spacing coefficient. In addition, in Examples 1 to 3, the effective diffusion coefficient of chloride ions was 1.60 cm 2 / year or less, and an apparent diffusion coefficient of 0.85 cm 2 / year or less, and in particular, Example 2 exhibited a saltwater permeation rate that was reduced to half of that of Comparative Example 1, thereby realizing high resistance to the intrusion of substances.

[0187] On the other hand, in Comparative Example 2, although the air content was within the specified range, the compressive strength was not improved compared to Comparative Example 1. Furthermore, in Comparative Example 2, the water permeability inhibition rate and material penetration resistance were improved, but the frost resistance indicated by the relative dynamic modulus of elasticity was significantly reduced, and practically acceptable strength and frost resistance could not be ensured. This result is due to the inhibition of the hydration reaction of cement and water in the water-containing cement composition and hardened concrete, and the resulting strength development.

Claims

1. a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units Microcapsules having a core-shell structure having and Cement, and At least one type of aggregate A hardened concrete composition containing 0.01 to 0.35 parts by weight of the microcapsules per 100 parts by weight of the cement, the organosilane is an organosilane containing at least one silicon-bonded alkyl group having 1 to 30 carbon atoms; the branched siloxane resin is a siloxane resin containing siloxane units of the formula RSiO 3 / 2 where R is an alkyl group; A precast concrete body, wherein the amount of air contained in the concrete composition is 3 to 6 volume % as measured in a test based on JIS A 1128.

2. 2. The precast concrete molded body according to claim 1, wherein the compressive strength ratio after 7 days of air curing exceeds 100% in a compression test based on JIS A 1108 and JIS A 6204.

3. A waterway structure, coastal structure or marine structure comprising the precast concrete molded article according to claim 1 or 2.

4. A road structure comprising the precast concrete molded article according to claim 1 or 2.

5. A retaining wall structure comprising the precast concrete molded article according to claim 1 or 2.

6. a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units A preparation step of preparing an unhardened concrete composition containing microcapsules having a core-shell structure having the following structure: A hardening and molding step of hardening and molding the unhardened concrete composition. A method for producing a precast concrete body, comprising: the unhardened concrete composition comprises cement and at least one aggregate; In the preparation step, the microcapsules are mixed in an amount of 0.01 to 0.35 parts by weight per 100 parts by weight of the cement, the organosilane is an organosilane containing at least one silicon-bonded alkyl group having 1 to 30 carbon atoms; the branched siloxane resin is a siloxane resin containing siloxane units of the formula RSiO 3 / 2 where R is an alkyl group; A method for producing a precast concrete body, wherein the concrete composition has an air content of 3 to 6 volume % as measured in a test based on JIS A 1128.

7. A method for improving at least one of the strength, substance intrusion resistance, freeze-thaw resistance, and air content stability of a precast concrete body, comprising: a core made of a water-repellent organosilicon material selected from the group consisting of organosilanes, organosilane partial condensates, and branched siloxane resins; and Silicon-based network polymer shell containing silica units A blending step of blending microcapsules having a core-shell structure having the above-mentioned structure into a concrete composition for the precast concrete molded body, the concrete composition comprises cement and at least one aggregate; In the blending step, the microcapsules are blended in an amount of 0.01 to 0.35 parts by weight per 100 parts by weight of the cement, the organosilane is an organosilane containing at least one silicon-bonded alkyl group having 1 to 30 carbon atoms; the branched siloxane resin is a siloxane resin containing siloxane units of the formula RSiO 3 / 2 where R is an alkyl group; The amount of air contained in the concrete composition as measured in a test based on JIS A 1128 is 3 to 6% by volume. A method for improving the strength of a precast concrete body, as well as at least one of its resistance to substance intrusion, resistance to freeze-thaw cycles, and stability of air content.

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