Concrete protective agent, manufacturing method of concrete protective agent, concrete modifier, manufacturing method of concrete modifier, and steel bar corrosion inhibitor

Abstract

To provide a concrete protective agent, a concrete modifier, and a steel bar corrosion inhibitor that can sufficiently suppress corrosion of a steel bar even in an environment where a steel bar in a concrete structure tends to be corroded and a concrete protective agent of these, and a manufacturing method of a concrete modifier.SOLUTION: A concrete protective agent includes an alkali metal silicate and a solvent, wherein the solvent includes water and an aluminate-derived tetrahydroxoaluminic acid ion.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a concrete protective agent, a method for producing a concrete protective agent, a concrete modifier, a method for producing a concrete modifier, and a reinforcing bar corrosion inhibitor. [Background technology]

[0002] Recently, in order to prevent concrete structures from being deteriorated due to salt damage, neutralization, frost damage, alkali-aggregate reaction, etc., concrete structures have been reinforced by coating, spraying, or impregnating (hereinafter, these are collectively referred to as "attaching concrete protective agents") concrete structures. Hydrogen ions, chloride ions, etc. are known as deterioration factors of concrete structures. Various studies have been conducted on concrete protective agents that reinforce concrete structures, and Patent Document 1 proposes a silicate-based concrete protective agent containing an alkali metal. According to the silicate-based concrete protective agent proposed in Patent Document 1, it is said that a CSH gel can be generated through a reaction with calcium ions present inside the concrete structure, and the generated CSH gel can block capillaries, cracks, etc. of the concrete structure that serve as a route for the infiltration of deterioration factors.

[0003] The application of a concrete protective agent to reinforce a concrete structure may be performed not only during the construction of the concrete structure, but also as a maintenance task after a certain period of time has passed since the construction of the concrete structure. Incidentally, calcium ions present in a concrete structure decrease over time due to (i) consumption due to reaction with carbon dioxide that has infiltrated into the concrete structure, (ii) consumption due to reaction with a silicate-based concrete protective agent when the concrete protective agent is applied during the construction of the concrete structure, and (iii) leaching out to the outside due to rainwater, etc., and the inside of the concrete structure after a certain period of time has passed since the construction of the concrete structure is often insufficient in calcium ions required to sufficiently generate CSH gel. In such a situation, Patent Document 2 proposes a reaction accelerator (corresponding to a concrete modifier) ​​that accelerates the reaction between a silicate-based surface impregnating agent (corresponding to a concrete protective agent) and concrete, and is a solution containing a calcium component and a nitrite. It is said that the reaction accelerator proposed in Patent Document 2 can supply calcium components (calcium ions) to a concrete structure lacking calcium components, thereby improving the reinforcing effect of the silicate-based surface impregnation method.

[0004] However, even if a concrete structure is reinforced using a silicate-based concrete protective agent, it is difficult to suppress the corrosion of the reinforcing bars of the concrete structure for a long period of time. For example, concrete structures in areas where snow melting agents, antifreeze agents, etc. need to be sprayed, and concrete structures in coastal areas are constantly exposed to conditions where the reinforcing bars are likely to corrode due to chloride ions. In addition, even if sea sand or chloride-containing admixtures are used in the construction of concrete structures, the reinforcing bars are likely to corrode due to chloride ions derived from the concrete materials. In other words, there is still room for improvement in suppressing the corrosion of the reinforcing bars of concrete structures. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-52815 A [Patent Document 2] JP 2014-201929 A Summary of the Invention [Problem to be solved by the invention]

[0006] The main object of the present invention is to provide a concrete protective agent, a concrete modifier, and a rebar corrosion inhibitor that can sufficiently inhibit corrosion of rebars even in environments where the rebars in concrete structures are prone to corrosion, and to provide methods for producing these concrete protective agents and concrete modifiers. [Means for solving the problem]

[0007] A concrete protective agent according to one embodiment of the present invention comprises an alkali metal silicate and a solvent, the solvent comprising water and tetrahydroxoaluminate ions derived from an aluminate.

[0008] In the above concrete protective agent, the solvent may be an alkaline solvent containing hydroxide ions. In the above concrete protective agent, the hydroxide ions may be hydroxide ions ionized by dissolving an alkali metal hydroxide in water. In the above concrete protective agent, the aluminate may be any one of potassium aluminate, sodium aluminate, and calcium aluminate.

[0009] In one embodiment of the present invention, a method for producing a concrete protective agent includes mixing water, an alkali metal silicate, and an aluminate.

[0010] In the above-mentioned method for producing a concrete protective agent, an alkali metal hydroxide may be further mixed.

[0011] A concrete modifier according to one embodiment of the present invention comprises calcium ions and a solvent, the solvent comprising water and tetrahydroxoaluminate ions derived from an aluminate salt.

[0012] In the above concrete modifying agent, the solvent may be an alkaline solvent containing hydroxide ions.

[0013] In a method for producing a concrete modifier according to one embodiment of the present invention, water, a calcium compound, and an aluminate are mixed together.

[0014] In the above-mentioned method for producing a concrete modifying agent, an alkali metal hydroxide may be further mixed.

[0015] A rebar corrosion inhibitor in one embodiment of the present invention comprises a mixture of water and tetrahydroxoaluminate ions derived from an aluminate salt. Effect of the Invention

[0016] The concrete protective agent and concrete modifier of the present invention can sufficiently suppress the corrosion of reinforcing bars even in an environment where reinforcing bars in a concrete structure are likely to corrode, while satisfying the functions required of these concrete protective agents and concrete modifiers. Furthermore, the reinforcing bar corrosion inhibitor of the present invention can sufficiently suppress the corrosion of reinforcing bars even in an environment where reinforcing bars in a concrete structure are likely to corrode. Furthermore, the manufacturing method of the concrete protective agent and concrete modifier of the present invention can manufacture the above-mentioned concrete protective agent and concrete modifier. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The concrete protective agent, the manufacturing method of the concrete protective agent, the concrete modifier, the manufacturing method of the concrete modifier, and the reinforcing bar corrosion inhibitor of the present invention will be described below. The present invention is not to be construed as being limited to the description of the embodiments exemplified below.

[0018] <<Concrete protection agent>> The concrete protective agent according to the embodiment of the present disclosure (hereinafter, referred to as the concrete protective agent of the embodiment) contains an alkali metal silicate and a solvent. The alkali metal silicate contained in the concrete protective agent of the embodiment can generate CHS gel through a reaction with calcium ions in the concrete structure. Therefore, by attaching the concrete protective agent of the embodiment to the concrete structure, defects in the concrete structure can be filled with CHS gel, and as a result, the concrete structure can be reinforced.

[0019] (Alkali metal silicates) The concrete protective agent of one embodiment includes an alkali metal silicate. Examples of the alkali metal silicate include sodium silicate (sodium silicate), potassium silicate (potassium silicate), and lithium silicate (lithium silicate). The alkali metal silicate included in the concrete protective agent of one embodiment may be one type or two or more types. An example of the concrete protective agent includes sodium silicate and potassium silicate.

[0020] The molar concentration of silicon dioxide derived from the alkali metal silicate is preferably 0.1 mol / L or more, more preferably 0.3 mol / L or more and 10 mol / L or less. The concrete protective agent of one embodiment containing the alkali metal silicate at the above molar concentration can better reinforce the concrete structure.

[0021] (solvent) The concrete protective agent of one embodiment includes a solvent. Here, in the concrete protective agent of one embodiment, the solvent includes water and tetrahydroxoaluminate ions derived from an aluminate. In the concrete protective agent of one embodiment, the tetrahydroxoaluminate ions derived from an aluminate can not only reinforce the concrete structure as described above, but also inhibit corrosion of the reinforcing steel of the concrete structure. Hereinafter, when the term tetrahydroxoaluminate ions is used, it means tetrahydroxoaluminate ions derived from an aluminate.

[0022] Although the mechanism by which the concrete protective agent of one embodiment can suppress corrosion of reinforcing bars in concrete structures is not clear at present, it is presumed that the tetrahydroxoaluminate ion contained in the concrete protective agent of one embodiment can eliminate deterioration factors that cause corrosion of reinforcing bars and can impart corrosion resistance to the reinforcing bars themselves. Even if not based on this mechanism, it is clear from the results of the examples and comparative examples described below that the tetrahydroxoaluminate ion contained in the concrete protective agent of one embodiment contributes to suppressing corrosion of reinforcing bars in concrete structures.

[0023] Deterioration factors that corrode reinforcing bars of concrete structures are mainly chloride ions and hydrogen ions. For example, chloride ions are supplied to the inside of a concrete structure by contacting a snow-melting agent or seawater with the concrete structure. In addition, when carbon dioxide present in the atmosphere dissolves in excess water or the like in a concrete structure, hydrogen ions are supplied to the inside of the concrete structure by hydrolysis. Hydrogen ions are also supplied to the inside of a concrete structure by acid rain or the like. As described above, the concrete protective agent of one embodiment can generate a CHS gel that fills defects in a concrete structure. However, even if the defects in a concrete structure are filled with the CHS gel, the supply (infiltration) of chloride ions and hydrogen ions from the outside to the inside of the concrete structure cannot be completely suppressed under the current circumstances. Therefore, in order to sufficiently suppress the corrosion of reinforcing bars of a concrete structure, it is necessary to eliminate (also referred to as consumption, reduction, or removal) chloride ions and hydrogen ions supplied from the outside or present inside the concrete structure.

[0024] Tetrahydroxoaluminate ions are reactive with chloride ions and hydrogen ions, which are deterioration factors. Specifically, tetrahydroxoaluminate ions react with chloride ions to produce aluminum chloride. Tetrahydroxoaluminate ions also react with hydrogen ions to produce aluminum hydroxide. Since deterioration factors are consumed in these reactions, it is presumed that deterioration factors can be eliminated even if they are supplied or present inside a concrete structure.

[0025] Furthermore, tetrahydroxoaluminate ions can provide corrosion resistance to the reinforcing bars themselves in concrete structures. Specifically, it is believed that tetrahydroxoaluminate ions receive electrons released from the iron component (Fe) of the reinforcing bars in concrete structures, forming an aluminum hydroxide coating on the surface of the reinforcing bars, and that this aluminum hydroxide coating acts to inhibit corrosion of the reinforcing bars caused by deterioration factors.

[0026] In other words, according to one embodiment of the concrete protective agent, corrosion of reinforcing bars in concrete structures can be sufficiently suppressed by both eliminating deterioration factors and imparting corrosion resistance to the reinforcing bars themselves.

[0027] Examples of tetrahydroxoaluminate ions include tetrahydroxoaluminate ions derived from sodium aluminate, tetrahydroxoaluminate ions derived from potassium aluminate, and tetrahydroxoaluminate ions derived from calcium aluminate. Among them, potassium aluminate is preferred because it has a higher effect of inhibiting corrosion of reinforcing bars caused by tetrahydroxoaluminate ions than other aluminates when the molar concentration of the aluminate added is the same. The tetrahydroxyaluminate ions may be tetrahydroxoaluminate ions derived from other aluminates.

[0028] An example of the solvent is one in which an aluminate is dissolved in water, and contains water and tetrahydroxoaluminate ions derived from the aluminate. Note that in the solvent obtained by dissolving an aluminate in water, the tetrahydroxoaluminate ions are present in an unstable state. In order to sufficiently enhance the above-mentioned effects of the tetrahydroxoaluminate ions, it is preferable that the tetrahydroxoaluminate ions are present in a stable state in the solvent.

[0029] A preferred form of the solvent is a solvent in which an aluminate is dissolved in water so that the molar concentration of the aluminate is 0.005 mol / L or more, more preferably 0.006 mol / L or more and 0.05 mol / L or less. According to an embodiment of the concrete protective agent containing such a solvent, the effect of inhibiting corrosion of reinforcing bars can be improved. In addition, the solution stability can be improved, and precipitation of aluminum oxide in the concrete protective agent can be suppressed. The molar concentration of the aluminate may be interpreted as the molar concentration of tetrahydroxoaluminate ions derived from the aluminate.

[0030] The molar concentration of aluminate relative to the molar concentration of silicon dioxide derived from an alkali metal silicate (molar concentration of aluminate / molar concentration of silicon dioxide) is preferably 0.0005 or more and 0.5 or less.

[0031] A preferred form of the solvent is an alkaline solvent containing hydroxide ions. According to an embodiment of the concrete protective agent containing this type of solvent, tetrahydroxoaluminate ions can be present in a stable state, and the effect of inhibiting corrosion of reinforcing bars in a concrete structure can be further enhanced. In addition, due to the action of hydroxide ions, when the concrete protective agent of an embodiment is attached to a concrete structure, the concrete protective agent can have good permeability into the interior of the concrete structure, and defects in the concrete structure can be more effectively improved.

[0032] The pH of the alkaline solvent containing hydroxide ions is not limited, but is preferably 11 or more, and more preferably 12 or more. According to an embodiment of the concrete protective agent containing this type of alkaline solvent, the tetrahydroxoaluminate ions can be present in a more stable state, and the effect of inhibiting corrosion of reinforcing bars in concrete structures can be further enhanced. As an example, the pH of the concrete protective agent in one embodiment is 11 or more.

[0033] There is no limitation on the molar concentration of hydroxide ions, but it is preferably 0.001 mol / L or more, and more preferably 0.01 mol / L or more. There is no limitation on the preferred upper limit, but one example is 1 mol / L. By setting the molar concentration at this level, tetrahydroxoaluminate ions can be present in a more stable state in the alkaline solvent, and the effect of inhibiting corrosion of reinforcing bars in concrete structures can be further improved.

[0034] The molar concentration of hydroxide ions relative to the molar concentration of silicon dioxide derived from an alkali metal silicate (molar concentration of hydroxide ions / molar concentration of silicon dioxide) is preferably 0.0001 or more and 10 or less.

[0035] An example of an alkaline solvent contains hydroxide ions ionized by dissolving an alkali metal hydroxide in water. This form of alkaline solvent is preferred because it is easy to make hydroxide ions exist.

[0036] Examples of alkali metal hydroxides dissolved in water to cause ionized hydroxide ions to exist in the alkaline solvent include sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. An example of an alkaline solvent is water in which any one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide are dissolved.

[0037] (A) An example alkaline solvent includes lithium ions and hydroxide ions. (B) An example of an alkaline solvent includes sodium ions, potassium ions, or both, lithium ions, and hydroxide ions. (C) An example of an alkaline solvent contains sodium ions, potassium ions, or both, and hydroxide ions, but does not contain lithium ions.

[0038] Among these, the alkaline solvents (A) and (B) are preferred because they can form a sufficient amount of aluminum hydroxide coating on the surface of the reinforcing bar by the action of lithium ions. Although the alkaline solvent (A) is good from the viewpoint of forming an aluminum hydroxide coating, it is prone to consuming hydroxide ions in the alkaline solvent due to its large Stokes radius. In consideration of this point, it is preferred that the alkaline solvent contains, together with lithium ions, other alkali metal ions that consume hydroxide ions less easily than lithium ions. In other words, it is preferred that the alkaline solvent contains lithium ions and alkali metal ions that have a smaller Stokes radius than lithium ions.

[0039] An example of the alkaline solvent includes lithium ions and other alkali metal ions, and the molar concentration of the lithium ions relative to the molar concentration of all the alkali metal ions (including the lithium ions and other alkali metal ions) is 50% or more and 90% or less.

[0040] In the above, the hydroxide ions contained in the alkaline solvent are ionized hydroxide ions by dissolving a hydroxide of an alkali metal in water. However, an alkaline solvent containing hydroxide ions may be obtained by other methods. For example, an alkaline solvent containing hydroxide ions may be obtained by electrolysis of water. The alkaline solvent obtained by electrolysis of water also has the same effect as the alkaline solvent obtained by dissolving a hydroxide of an alkali metal in water. The same applies to the preferred form of the alkaline solvent. The method of dissolving a hydroxide of an alkali metal in water is preferable because it can easily produce an alkaline solvent containing hydroxide ions. There is no limitation on the method of obtaining an alkaline solvent containing hydroxide ions by electrolyzing water, and it can be obtained by appropriately selecting a method conventionally known in the field of alkaline electrolytic water.

[0041] The concrete protective agent of one embodiment may contain other functional components in addition to the alkali metal silicate and the solvent. Examples of the functional components include a filling rate improver, a surfactant, a water resistance improver, an abrasion resistance improver, a water repellent agent, and a rebar inhibitor. An example of the packing rate enhancer is colloidal silica. An example of the water resistance improver is sodium hexametaphosphate. An example of the wear resistance improver is magnesium silicofluoride. Examples of the water repellency agent include alkylalkoxysilanes.

[0042] <<Method of manufacturing concrete protection agent>> A method for producing a concrete protective agent according to an embodiment of the present disclosure (hereinafter, referred to as a method for producing a concrete protective agent of an embodiment) is a method for producing a concrete protective agent by mixing water, an alkali metal silicate, and an aluminate. According to the method for producing a concrete protective agent of an embodiment, a concrete protective agent can be produced that can satisfactorily reinforce a concrete structure and further sufficiently suppress corrosion of reinforcing bars in the concrete structure.

[0043] According to the method for producing a concrete protective agent of the embodiment, the concrete protective agent of the embodiment can be produced. Therefore, the components, mixing amounts (molar concentrations), etc. used in the method for producing a concrete protective agent of the embodiment can be appropriately selected from those described in the concrete protective agent of the embodiment, and description thereof will be omitted here.

[0044] A preferred method for producing the concrete protective agent of one embodiment is a method for producing a preferred concrete protective agent of one embodiment. A preferred method for producing the concrete protective agent of one embodiment includes a step of mixing an alkali metal hydroxide. According to this embodiment of the method for producing the concrete protective agent, the tetrahydroxoaluminate ion derived from the aluminate can be present in a stable state in the concrete protective agent. In other words, the solution stability of the concrete protective agent can be improved.

[0045] Furthermore, the mixing order (addition order) of each component in the manufacturing method of the concrete protective agent of one embodiment is not limited. For example, the alkali metal silicate and aluminate may be added to the water all at once, or the alkali metal silicate and aluminate may be added to the water stepwise. A preferred embodiment of the concrete protective agent is manufactured by preparing a solvent containing water and an aluminate, and then mixing the solvent with the alkali metal silicate. According to this embodiment, the concrete protective agent can be manufactured in which each component is uniformly mixed.

[0046] <<Concrete modifier>> The concrete modifier according to the embodiment of the present disclosure (hereinafter, referred to as the concrete modifier of the embodiment) contains calcium ions and a solvent. According to the concrete modifier of the embodiment, calcium ions can be supplied to a concrete structure. The concrete modifier of the embodiment differs from the concrete protective agent of the embodiment in that the alkali metal silicate is replaced by calcium ions, and in other respects, unless otherwise specified, the configuration described in the concrete protective agent of the embodiment can be appropriately selected.

[0047] In one embodiment, the concrete modifier contains a tetrahydroxoaluminate ion derived from an aluminate salt as a solvent. According to the concrete modifier of one embodiment, the same action and effect as the concrete protective agent of one embodiment can be obtained, and corrosion of reinforcing bars in a concrete structure can be suppressed.

[0048] (Calcium ion) The calcium ions contained in the concrete modifier of one embodiment are obtained by dissolving a calcium compound in water or a solvent. Examples of calcium compounds for obtaining calcium ions include calcium lactate, calcium acetate, calcium carbonate, calcium citrate, calcium gluconate, calcium phosphate, and calcium sulfate. Among these, calcium lactate is preferred because it has a higher solubility in water than other calcium compounds and can easily include calcium ions in a solvent.

[0049] The molar concentration of calcium ions is preferably 0.1 mol / L or more, and more preferably 0.3 mol / L or more and 2.5 mol / L or less. By setting the molar concentration in this range, a sufficient amount of calcium ions can be supplied to the concrete structure. In addition, the solubility of calcium compounds can be improved.

[0050] The molar concentration of aluminate relative to the molar concentration of calcium ions (molar concentration of aluminate / molar concentration of calcium ions) is preferably 0.002 or more and 0.15 or less.

[0051] (solvent) In one embodiment, the solvent of the concrete modifying agent includes water and tetrahydroxoaluminic acid derived from an aluminate. A preferred form of the solvent is a solvent in which an aluminate is dissolved in water such that the molar concentration of the aluminate is 0.005 mol / L or more and 0.015 mol / L or less.

[0052] A preferred form of the solvent is an alkaline solvent containing water, hydroxide ions, and tetrahydroxoaluminate ions derived from an aluminate. An example of an alkaline solvent contains hydroxide ions ionized by dissolving an alkali metal hydroxide in water.

[0053] In the concrete protective agent of one embodiment, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. are exemplified as preferred components for obtaining an alkaline solvent. However, from the viewpoint of solution stability, the alkaline solvent contained in the concrete modifier of one embodiment does not contain lithium ions, or even if it contains lithium ions, its molar concentration is preferably less than 0.32 mol / L. In other words, an alkaline solvent that does not use lithium hydroxide, or even if it uses lithium hydroxide, in a small amount is preferred. According to the concrete modifier containing such an alkaline solvent, it is possible to suppress the generation of aluminum hydroxide precipitate in the solution of the concrete modifier, and the solution stability is good. In addition, when using a concrete modifier that takes such solution stability into consideration, it is preferable to attach the concrete protective agent of the above-mentioned one embodiment to the concrete structure after the concrete structure is modified.

[0054] An example alkaline solvent contains at least one of sodium ions, potassium ions, and lithium ions, and hydroxide ions. An example alkaline solvent contains potassium ions and hydroxide ions. An example alkaline medium contains sodium and / or potassium ions and hydroxide ions. An example alkaline solvent contains sodium and / or potassium ions and hydroxide ions, but no lithium ions.

[0055] The pH of the alkaline solvent containing hydroxide ions is not limited, but is preferably at least 11. As an example, the pH of the concrete modifier in one embodiment is 11 or more.

[0056] The molar concentration of hydroxide ions is preferably 0.001 mol / L or more, more preferably 0.015 mol / L or more. There is no upper limit, but an example is 1 mol / L. By using such a molar concentration, the tetrahydroxoaluminate ions can be present in the alkaline solvent in a more stable state, and the effect of inhibiting corrosion of reinforcing bars in concrete structures can be further enhanced.

[0057] The molar concentration of hydroxide ions relative to the molar concentration of calcium ions (molar concentration of hydroxide ions / molar concentration of calcium ions) is preferably 0.0004 or more and 10 or less.

[0058] As with the concrete protectant in one embodiment, the alkaline solvent may be obtained by electrolysis of water.

[0059] <<How to manufacture concrete modifier>> A method for producing a concrete modifier according to an embodiment of the present disclosure (hereinafter, referred to as a method for producing a concrete modifier of an embodiment) is a method for producing a concrete modifier by mixing water, a calcium compound, and an aluminate. According to the method for producing a concrete modifier of an embodiment, a concrete modifier can be produced that can supply calcium ions to a concrete structure and can sufficiently suppress corrosion of reinforcing bars in the concrete structure.

[0060] According to the manufacturing method of the concrete modifier of the embodiment, the concrete modifier of the embodiment can be manufactured. Therefore, the components, mixing amounts (molar concentrations), etc. used in the manufacturing method of the concrete modifier of the embodiment can be appropriately selected and used from those described in the concrete modifier of the embodiment, and the description thereof will be omitted here.

[0061] A preferred method for producing the concrete modifier of one embodiment is a preferred method for producing the concrete modifier of one embodiment. A preferred method for producing the concrete modifier of one embodiment includes a step of mixing an alkali metal hydroxide. According to this method for producing the concrete modifier, the tetrahydroxoaluminate ion derived from the aluminate can be present in a stable state in the concrete protective agent. In other words, the solution stability of the concrete modifier can be improved.

[0062] In addition, the mixing order (addition order) of each component in the manufacturing method of the concrete modifier of one embodiment is not limited. For example, the calcium compound and the aluminate may be added to the water all at once, or the calcium compound and the aluminate may be added to the water stepwise in any order. A preferred embodiment of the concrete modifier is manufactured by preparing a solvent containing water and the aluminate, and then mixing the solvent with the calcium compound. According to this embodiment, the concrete modifier can be manufactured in which each component is uniformly mixed.

[0063] <<Rebar corrosion inhibitor>> A rebar corrosion inhibitor according to an embodiment of the present disclosure (hereinafter, referred to as a rebar corrosion inhibitor of an embodiment) contains water and tetrahydroxoaluminate ions derived from an aluminate. According to the rebar corrosion inhibitor of the embodiment, the tetrahydroxoaluminate ions can sufficiently inhibit corrosion of rebars in concrete structures.

[0064] One embodiment of the rebar corrosion inhibitor corresponds to one embodiment of the concrete protection agent minus the essential component alkali metal silicate, or one embodiment of the concrete modifier minus the essential component calcium ion.

[0065] <<Method for protecting and improving concrete structures, and method for inhibiting corrosion>> In one embodiment, a method for protecting a concrete structure comprises adhering the concrete protective agent of the above embodiment to a concrete structure. In one embodiment, a method for modifying a concrete structure comprises adhering the concrete modifying agent of the above embodiment to a concrete structure. In one embodiment of the method for protecting and modifying a concrete structure, the concrete modifier of the above embodiment is applied to a concrete structure, the concrete structure is modified, and then the concrete protective agent of the above embodiment is applied to the modified concrete structure. According to this method, the corrosion inhibition effect of the concrete structure can be enhanced by the synergistic effect of the concrete modifier and the concrete protective agent. In one embodiment of the method for inhibiting corrosion of a concrete structure, the reinforcing bar corrosion inhibitor of the above embodiment is adhered to a concrete structure. There is no limit to the amount of the concrete protection agent, concrete modifier, and rebar corrosion inhibitor applied, and the amount may be appropriately determined depending on the concrete structure. 2 That's all. Examples of concrete structures include bridges (ground coverings, decks), bridge piers, bridge abutments, dam embankments, tunnels (hole walls), box culverts, port facilities, port structures, river structures, revetment structures, irrigation channels, culverts, culverts, water tanks, underground pits, multi-storey car parks, secondary concrete products, etc. Other concrete structures may also be used. EXAMPLES

[0066] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0067] (Solvent preparation) The solvents shown in Tables 1 to 3 below were prepared. In each table, when two or more types of alkali metal hydroxides are listed, the mixing ratio is 1:1 (or 1:1:1) (except when the mixing ratio is listed in the table). In the tables, K aluminate means potassium aluminate, and Na aluminate means sodium aluminate.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] (Sodium chloride added) Sodium chloride was added to each of the solvents in Tables 1 to 3 (excluding the solvents in Group No. 11, D in the tables) so that the molar concentration of chloride ions / the molar concentration of hydroxide ions was 0.625. The amount of each solvent to which sodium chloride was added was 250 ml. For Group No. 11 in Table 2 and Group No. D in Table 3, sodium chloride was added so that the molar concentration of chloride ions / the molar concentration of hydroxide ions was 0.31. The amount of the solvent to which sodium chloride was added was 250 ml. In addition, a molar concentration of chloride ions / molar concentration of hydroxide ions = 0.625 is a harsh environment in which rebar is prone to corrosion.

[0072] (Reinforcement corrosion evaluation 1) A 10 cm long reinforcing bar with its surface coating scraped off was partially immersed in each of the above-mentioned solvents containing sodium chloride, and the condition of the reinforcing bar after immersion for 7 days was visually inspected and corrosion of the reinforcing bar was evaluated based on each evaluation criterion 1. The evaluation results are shown in Table 4.

[0073] "Evaluation Criteria 1" A(1): A white coating of aluminum hydroxide has formed on the surface of the rebar, and no corrosion can be seen on the entire rebar. A(2): A small amount of white aluminum hydroxide film has formed on the surface of the rebar, and no corrosion is observed on the entire rebar. A(3): The formation of a white coating of aluminum hydroxide on the surface of the reinforcing bar could not be confirmed with the naked eye, but no corrosion was observed on the entire reinforcing bar. B(1): A white coating of aluminum hydroxide has formed on the surface of the reinforcing bar, but slight corrosion that is not problematic is observed on the reinforcing bar at the liquid interface. B(2): A white coating of aluminum hydroxide has formed on the surface of the reinforcing bar, but slight corrosion that is not problematic is observed on the reinforcing bar in the liquid. B(3): A white coating of aluminum hydroxide has formed on the surface of the reinforcing bar, but slight corrosion that is not problematic is observed on the reinforcing bar at the liquid-liquid interface. B(4): A small amount of white aluminum hydroxide film has formed on the surface of the reinforcing bar, but slight corrosion that is not problematic is observed on the reinforcing bar at the liquid interface. B(5): A slight white coating of aluminum hydroxide has formed on the surface of the reinforcing bar, but slight corrosion that is not problematic is observed on the reinforcing bar in the liquid. B(6): A small amount of white aluminum hydroxide film has formed on the surface of the reinforcing bar, but slight corrosion that is not problematic is observed in the reinforcing bar at the liquid interface and in the liquid. B(7): A small amount of a white film of aluminum hydroxide has formed on the surface of the rebar, but there is more corrosion of the rebar in the liquid than in B(5), which is not problematic. C(1): The formation of a white aluminum hydroxide coating on the surface of the reinforcing bar cannot be confirmed with the naked eye, and slight, non-problematic corrosion is observed on the reinforcing bar at the liquid interface. C(2): The formation of a white aluminum hydroxide coating on the surface of the rebar cannot be visually confirmed, and slight, non-troublesome corrosion of the rebar in the liquid is observed. C(3): The formation of a white aluminum hydroxide coating on the surface of the reinforcing bar cannot be confirmed with the naked eye, and slight, non-problematic corrosion is observed on the reinforcing bar in the liquid and at the liquid interface. NG(1): The formation of a white aluminum hydroxide coating on the surface of the rebar cannot be visually confirmed, and problematic corrosion is observed throughout the rebar in the liquid. NG(2): The formation of a white aluminum hydroxide coating on the surface of the rebar cannot be confirmed with the naked eye, and problematic corrosion is observed locally on the rebar in the liquid. NG(3): The formation of a white aluminum hydroxide coating on the surface of the rebar cannot be confirmed with the naked eye, and problematic corrosion is observed on the rebar at the liquid interface.

[0074] [Table 4]

[0075] (Reinforcement corrosion evaluation 2) Sodium silicate and potassium silicate were added to the solvents 1-4 and 1-9 in Table 1, respectively, to obtain concrete protective agents 1-4 and 1-9. The amounts of sodium silicate and potassium silicate added were 4.5 mol / L, respectively. A 10 cm long reinforcing bar with its surface coating scraped off was partially immersed in the concrete protective agent, and the condition of the reinforcing bar after immersion for 7 days was visually confirmed, and the corrosion of the reinforcing bar was evaluated based on each evaluation criterion. No corrosion was observed in the reinforcing bars for either concrete protective agent 1-4 or 1-9.

[0076] (Preparation of concrete modifier) Concrete modifiers 1 and 2 were prepared by mixing water, potassium hydroxide, potassium aluminate, and calcium. In the concrete modifying agent 1, the molar concentration of hydroxide ions is 0.002 mol / L, the molar concentration of potassium aluminate is 0.012 mol / L, and the molar concentration of calcium is 0.44 mol / L. In the concrete modifying agent 2, the molar concentration of hydroxide ions is 0.032 mol / L, the molar concentration of potassium aluminate is 0.012 mol / L, and the molar concentration of calcium is 0.44 mol / L.

[0077] (Sodium chloride added) Sodium chloride was added to each of the concrete modifiers 1 and 2 prepared above so that the molar concentration of chloride ions was 0.02 mol / L, to obtain sodium chloride-added concrete modifiers 1 and 2. Sodium chloride-added concrete modifiers 1 and 2 were each prepared to 250 ml.

[0078] (Reinforcement corrosion evaluation 3) A 10 cm long rebar with its surface coating scraped off was partially immersed in the above-mentioned concrete modifiers 1 and 2 containing added sodium chloride, and the condition of the rebar after immersion for 7 days was visually inspected and the rebar corrosion was evaluated based on the above-mentioned evaluation criterion 1. Concrete modifier 1 was rated B(7), and concrete modifier 2 was rated A(2).

Claims

1. A concrete protective agent comprising: comprising an alkali metal silicate and a solvent; The solvent comprises water and tetrahydroxoaluminate ions derived from an aluminate salt. Concrete protection agent.

2. The solvent is an alkaline solvent containing hydroxide ions. The concrete protective agent according to claim 1.

3. The hydroxide ion is a hydroxide ion ionized by dissolving an alkali metal hydroxide in water. The concrete protective agent according to claim 2.

4. The aluminate is any one of potassium aluminate, sodium aluminate, and calcium aluminate. The concrete protective agent according to any one of claims 1 to 3.

5. A method for producing a concrete protective agent, comprising: mixing water, an alkali metal silicate, and an aluminate; A method for manufacturing a concrete protective agent.

6. Further, an alkali metal hydroxide is mixed. A method for producing the concrete protective agent according to claim 5.

7. A concrete modifier comprising: Contains calcium ions and a solvent, The solvent comprises water and tetrahydroxoaluminate ions derived from an aluminate salt. Concrete modifier.

8. The solvent is an alkaline solvent containing hydroxide ions. The concrete modifier according to claim 7.

9. A method for producing a concrete modifier, comprising: mixing water, a calcium compound, and an aluminate; A method for manufacturing a concrete modifier.

10. Further, an alkali metal hydroxide is mixed. A method for producing the concrete modifier according to claim 9.

11. A rebar corrosion inhibitor comprising: water, and a mixture of tetrahydroxoaluminate ions derived from aluminates; Steel bar corrosion inhibitor.

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