Concrete surface coating method and surface impregnation material used therefor

Abstract

The present invention provides a concrete surface coating method and a surface impregnation material used therein, which can suppress water permeation from the concrete surface and inhibit the progression of carbonation. [Solution] A concrete surface coating method comprising applying a surface impregnating material to the concrete surface, wherein the surface impregnating material consists of an aqueous solution containing alkali metal silicate, phosphoric acid, and water, and the phosphoric acid content is 0.05 to 20 g per 1 kg of the surface impregnating material.

Description

[Technical Field]

[0001] This invention relates to a concrete surface coating method for applying a surface impregnating material to a concrete surface, and to a surface impregnating material used therein. [Background technology]

[0002] Cracks can develop in hardened concrete due to various factors. For example, shrinkage during hardening, repeated expansion and contraction due to temperature changes, and deformation due to load are the main causes of crack formation. These cracks can reduce the strength of the concrete itself and cause water leakage. In addition, moisture and air that penetrate through the cracks can corrode the reinforcing steel inside, or the concrete around the cracks can react with carbon dioxide and neutralize, reducing its strength. If cracks are left untreated, they may grow, potentially making the problem even more serious.

[0003] Patent Document 1 describes a concrete repair method characterized by first injecting a first aqueous solution containing an alkali metal silicate into cracks that have occurred on the surface of hardened concrete, and then injecting a second aqueous solution containing a salt of a metal belonging to Group 2 of the periodic table into the cracks. According to this method, it is possible to repair concrete with cracks of various sizes and to perform appropriate repairs according to the condition of the cracks.

[0004] Patent Document 2 describes a method for immobilizing substances onto cement and concrete, characterized by contacting the surface of a hardened cement and concrete body with an aqueous solution containing phosphate ions, and then contacting the surface of the hardened body with an aqueous solution containing various ions other than phosphate ions. According to this method, by reacting phosphate ions in an aqueous solution with the surface of the cement and concrete, the ions react with the calcium in the cement to generate calcium phosphate in the surface layer of the cement and concrete, and various substances (ions) having desired properties can be immobilized on the calcium phosphate by ion exchange or the like.

[0005] Furthermore, Patent Document 3 describes a method for constructing a hardened concrete body, which involves placing concrete, contacting the concrete with a neutralization solution containing a neutralizing agent before it hardens, and then curing the concrete in a moist environment, characterized in that the neutralizing agent is a composite agent containing water-soluble phosphoric acid. According to this method, hydroxyapatite can be formed on the surface of the hardened concrete body, and the hydroxyapatite acts as a protective layer for the hardened concrete body, making it possible to suppress the leaching of various components such as alkaline and calcium components generated from the hardened concrete body after construction over a long period of time. However, although Patent Documents 1 to 3 describe the use of alkali metal silicate impregnating materials or aqueous solutions containing phosphate ions, they did not necessarily suppress the penetration of moisture or carbonation.

[0006] On the other hand, Patent Document 4 describes a curing structure for concrete or mortar floors, characterized in that an inorganic impregnating agent layer (2) composed of silica, potassium silicate, potassium phosphate, and water is formed on a construction surface (1) such as a concrete or mortar floor, and the action of the inorganic impregnating agent layer (2) eliminates the need for curing work using curing sheets or the like on the construction surface (1) such as a concrete or mortar floor. According to this, the inorganic impregnating agent layer (2) composed of silica, potassium silicate, potassium phosphate, and water formed on the construction surface (1) such as a concrete or mortar floor chemically bonds with calcium hydroxide, the main component of concrete, to form a calcium silicate layer with excellent water resistance, durability, and chemical resistance. This surface calcium silicate layer prevents the penetration of carbon dioxide (CO2) and acid rain, which are causes of concrete deterioration and carbonation, as well as densifying the surface to increase its strength, suppressing the occurrence of cracks, and eliminating the need for curing work using curing sheets or the like on the construction surface of a concrete or mortar floor. However, although Patent Document 4 describes an inorganic impregnating agent containing silica, potassium silicate, potassium phosphate, and water, it does not necessarily suppress water penetration or neutralization. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2006-36563 [Patent Document 2] Japanese Patent Application Publication No. 6-128054 [Patent Document 3] Japanese Patent Publication No. 2020-172816 [Patent Document 4] Japanese Patent Publication No. 2010-95871 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention was made to solve the above problems, and aims to provide a concrete surface coating method and a surface impregnation material used therein that can suppress water permeation from the concrete surface and suppress the progression of carbonation. [Means for solving the problem]

[0009] The above problem is solved by providing a concrete surface coating method, which involves applying a surface impregnating material to the concrete surface, wherein the surface impregnating material consists of an aqueous solution containing alkali metal silicate, phosphoric acid, and water, and the phosphoric acid content is 0.05 to 20 g per 1 kg of the surface impregnating material.

[0010] In this case, it is preferable to perform a curing process in which the surface impregnating material is allowed to air dry for 24 hours or more after application, and it is preferable that the pH of the surface impregnating material be 11.2 to 12.2.

[0011] Furthermore, the above problem can also be solved by providing a surface impregnating material for coating a concrete surface, which consists of an aqueous solution containing alkali metal silicate, phosphoric acid, and water, and is characterized in that the phosphoric acid content is 0.05 to 20 g per 1 kg of the surface impregnating material. [Effects of the Invention]

[0012] The present invention provides a concrete surface coating method and a surface impregnation material used therein that can suppress water permeation from the concrete surface and suppress the progression of carbonation. [Brief explanation of the drawing]

[0013] [Figure 1] This photograph shows the process of applying a surface impregnation agent to a concrete test specimen used for a surface water absorption test. [Figure 2] This is a photograph showing the surface water absorption test in progress. [Figure 3]This is a photograph showing the state of applying a surface impregnating material to a concrete test specimen used in a carbonation acceleration test. [Figure 4] This is a photograph (left: Comparative Example 1, right: Example 2) showing the state of spraying a phenolphthalein solution after the carbonation acceleration test to confirm the presence or absence of color development. [Figure 5] This is a graph showing the results of the surface water absorption test. [Figure 6] This is a graph showing the results of the carbonation acceleration test.

Embodiments for Carrying Out the Invention

[0014] The concrete surface coating method of the present invention is a concrete surface coating method for applying a surface impregnating material to the concrete surface, wherein the surface impregnating material is an aqueous solution containing an alkali metal silicate, phosphoric acid, and water, and the content of the phosphoric acid is 0.05 to 20 g with respect to 1 kg of the surface impregnating material.

[0015] As can be seen from the comparison between the examples and comparative examples described later, in Comparative Example 1, where no surface impregnating material was applied; Comparative Example 5, where a 1% phosphoric acid aqueous solution was used instead of the surface impregnating material; Comparative Example 6, where a silicate-based impregnating material was used instead of the surface impregnating material; and Comparative Example 8, where a 1% phosphoric acid aqueous solution was used for the first application and then a silicate-based impregnating material was used for the second application, the surface water absorption test results showed that water permeability from the concrete surface was not suppressed, and the carbonation depth was above a certain level, indicating that the progression of carbonation was not suppressed. Furthermore, in Comparative Example 2, where the phosphoric acid content exceeded 20g; Comparative Example 3, where trisodium phosphate (Na3PO4) was used instead of phosphoric acid; Comparative Example 4, where a 0.1% aqueous phosphoric acid solution was used instead of the surface impregnating material; Comparative Example 7, where a 0.1% aqueous phosphoric acid solution was used instead of the surface impregnating material for the first application, followed by a silicate-based impregnating material for the second application; Comparative Example 9, where a 0.1% aqueous phosphoric acid solution was used instead of the surface impregnating material for the first application, followed by a 5% aqueous calcium hydroxide solution for the second application; and Comparative Example 10, where a 1% aqueous phosphoric acid solution was used instead of the surface impregnating material for the first application, followed by a 5% aqueous calcium hydroxide solution for the second application, the surface water absorption test showed that water permeability from the concrete surface was not suppressed. In contrast, in the examples where the surface impregnating material contained alkali metal silicate, phosphoric acid, and water, and the phosphoric acid content was 0.05 to 20g per 1kg of the surface impregnating material, the surface water absorption test showed that water permeability from the concrete surface was effectively suppressed (Examples 1 to 4). Furthermore, the results of the carbonation acceleration test showed a carbonation depth of 0 mm, indicating that the progression of carbonation was effectively suppressed (Examples 1-2). Therefore, it is clear that there is great significance in adopting a surface impregnating material containing alkali metal silicate, phosphoric acid, and water, wherein the phosphoric acid content is 0.05 to 20 g per 1 kg of the surface impregnating material. In other words, the present invention also includes a surface impregnating material for coating a concrete surface, which consists of an aqueous solution containing alkali metal silicate, phosphoric acid, and water, and is characterized in that the phosphoric acid content is 0.05 to 20 g per 1 kg of the surface impregnating material.

[0016] The surface impregnation material used in the present invention consists of an aqueous solution containing alkali metal silicate, phosphoric acid, and water, with a phosphoric acid content of 0.05 to 20 g per 1 kg of the surface impregnation material. Examples of the cation species of alkali metal silicate include lithium ions, sodium ions, and potassium ions, but sodium ions are preferred due to their availability and cost. Furthermore, the anionic species of alkali metal silicate is not particularly limited, and orthosilicate anion [SiO4] is also acceptable. 4- ] and metasilicate anion [SiO3 2- This may include not only anionic species such as ], but also anionic species formed by the linkage of multiple silicate [SiO2] units.

[0017] Specific examples of alkali metal silicates include sodium orthosilicate, potassium orthosilicate, lithium orthosilicate, sodium metasilicate, potassium metasilicate, lithium metasilicate, and water glass. Among these, at least one selected from the group consisting of sodium orthosilicate, potassium orthosilicate, sodium metasilicate, potassium metasilicate, and water glass is preferably used, at least one selected from the group consisting of sodium orthosilicate, sodium metasilicate, and water glass is more preferably used, and water glass is particularly preferably used. Water glass is an aqueous solution of alkali metal silicate in which multiple silicic acid [SiO2] units are linked together to form an anionic species. The alkali metal used here may be potassium, but sodium is preferred, and from this viewpoint, sodium silicate is a preferred embodiment. In the case of sodium silicate, the general formula for the solid content is Na2O·nSiO2. The molar ratio of the sodium silicate is preferably 1.2 to 3.6, and more preferably 2.5 to 3.3. Furthermore, the solid content of the alkali metal silicate is preferably 15-40%, and more preferably 20-35%.

[0018] The alkali metal silicate content is preferably 200 to 800 g per 1 kg of surface impregnation material, more preferably 300 to 700 g, even more preferably 400 to 600 g, and particularly preferably 450 to 550 g.

[0019] The phosphoric acid used in this invention refers to orthophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), etc., but it may also form salts as long as it does not hinder the effects of this invention. As shown in Comparative Example 3 described later, when trisodium phosphate aqueous solution (Na3PO4) was used, surface water absorption tests revealed that it was not able to suppress water permeation from the concrete surface. From this viewpoint, it is preferable that the phosphoric acid is substantially orthophosphoric acid (H3PO4), and more preferably consists solely of orthophosphoric acid (H3PO4).

[0020] The phosphoric acid content is 0.05 to 20 g per 1 kg of surface impregnation material. It has been shown that a phosphoric acid content within this range can suppress water permeation from the concrete surface and inhibit the progression of carbonation. The phosphoric acid content is preferably 0.08 g or more, more preferably 0.1 g or more, even more preferably 0.2 g or more, and particularly preferably 0.4 g or more. On the other hand, the phosphoric acid content is preferably 18 g or less, more preferably 16 g or less, even more preferably 12 g or less, particularly preferably 8 g or less, and most preferably 6 g or less.

[0021] In the surface impregnation material used in the present invention, the water content is preferably 200 to 800 g, more preferably 300 to 700 g, even more preferably 400 to 600 g, and particularly preferably 450 to 550 g.

[0022] The pH of the surface impregnation material used in the present invention is not particularly limited, but the inventors have found that if the pH falls below a certain level, gelation occurs when alkali metal silicate and phosphoric acid are mixed. From this viewpoint, the pH is preferably 11.20 or higher, more preferably 11.30 or higher, even more preferably 11.38 or higher, particularly preferably 11.48 or higher, and most preferably 11.66 or higher. On the other hand, the pH is usually 14 or lower, preferably 13 or lower, and more preferably 12 or lower.

[0023] In the surface impregnation material used in the present invention, other components may be included as long as they do not hinder the effects of the present invention. Preferably, the other components are present in amounts of 0.01 to 5 g per 1 kg of surface impregnation material, and more preferably, substantially no other components are included. In particular, a preferred embodiment is one in which the surface impregnation material consists of an aqueous solution containing only alkali metal silicate, phosphoric acid, and water.

[0024] The concrete surface coating method of the present invention involves applying the surface impregnating material to the concrete surface. This suppresses water permeation from the concrete surface and inhibits the progression of carbonation. The inventors hypothesize that the alkali metal silicate and phosphoric acid contained in the surface impregnating material both react with calcium hydroxide in the concrete, and that the reaction products fill the fine voids in the surface layer of the concrete, causing densification. As can be seen from the comparison between the examples and comparative examples described later, comparative examples 4 and 5, which used only an aqueous phosphoric acid solution, comparative example 6, which used only a silicate-based impregnating material, and comparative examples 7 and 8, which applied an aqueous phosphoric acid solution and a silicate-based impregnating material in sequence, all failed to suppress water permeation from the concrete surface in surface water absorption tests. Furthermore, comparative examples 5, 6, and 8, which underwent carbonation acceleration tests, also showed a carbonation depth above a certain level, indicating that the progression of carbonation was not suppressed. Therefore, it is clear that it is important for the surface impregnating material to contain both alkali metal silicate and phosphoric acid.

[0025] In the present invention, the method of applying the surface impregnating material is not particularly limited, and it may be applied by a brush, spray, brush, roller, spraying, etc., but it is important that it is applied uniformly. Among them, it is preferably applied by brush painting. Also, the number of times of applying the surface impregnating material is not particularly limited, and it may be applied once or may be applied two or more times. From the viewpoint of further suppressing the progress of water permeability and carbonation from the concrete surface, it is a preferred embodiment to perform a curing process of natural drying for 24 hours or more after applying the surface impregnating material. Among them, it is a more preferred embodiment to perform the curing process after applying the surface impregnating material and then apply the surface impregnating material again. That is, it is a more preferred embodiment to apply the surface impregnating material two or more times. The natural drying time is preferably 96 hours or less, more preferably 72 hours or less, and even more preferably 48 hours or less.

[0026] In the present invention, as the application amount of the surface impregnating material on the concrete surface, for each application operation, it is 0.01 to 1.0 kg / m 2 It is preferable to apply. When the application amount per time is less than 0.01 kg / m 2 , it may be difficult to uniformly apply the entire concrete surface, and it is more preferably 0.05 kg / m 2 or more, and even more preferably 0.08 kg / m 2 or more. On the other hand, when the application amount per time exceeds 1.0 kg / m 2 , a pool of the surface impregnating material may occur on the concrete surface, and when the surface impregnating material dries, it may peel off from the concrete surface. From such a viewpoint, the application amount per time is more preferably 0.8 kg / m 2 or less, even more preferably 0.6 kg / m 2 or less, particularly preferably 0.4 kg / m 2 or less, and most preferably 0.2 kg / m 2 or less. By controlling the application amount per time in this way, it is possible to prevent the surface impregnating material from peeling off from the concrete surface.

[0027] The surface condition of the concrete when applying the surface impregnating material is not particularly limited; the concrete surface may be wet, dry, or completely dry. However, from the viewpoint of good penetration, it is preferable to apply the surface impregnating material when the concrete surface is dry. Here, a dry surface condition means that the voids inside the concrete are filled with water, but the concrete surface is dry enough that it does not get wet when touched (sometimes called a dry, saturated surface condition). If the concrete surface is too dry when applying the surface impregnating material, it is preferable to spray water to dry the surface before applying the surface impregnating material.

[0028] The concrete surface coating method of the present invention can be applied to various concrete surfaces, but from the viewpoint of suppressing the progression of carbonation, it is preferable to apply it after concrete placement. [Examples]

[0029] The present invention will be described in more detail below using examples.

[0030] [Raw materials] Sodium silicate No. 3: Manufactured by Toso Sangyo Co., Ltd., SiO2 (wt%) 27.7-29.3%, Na2O (wt%) 8.8-9.8%, molar ratio 3.1-3.2, pH 11.80 • Phosphoric acid aqueous solution a: An 85% phosphoric acid aqueous solution (Merck, 85% phosphoric acid 100563) was diluted with water to obtain a 0.085% phosphoric acid aqueous solution. • Phosphoric acid aqueous solution b: An 85% phosphoric acid aqueous solution (Merck, 85% phosphoric acid 100563) was diluted with water to obtain a 0.85% phosphoric acid aqueous solution. • Phosphoric acid aqueous solution c: An 85% phosphoric acid aqueous solution (Merck, 85% phosphoric acid 100563) was diluted with water to obtain a 2.55% phosphoric acid aqueous solution. • Aqueous phosphoric acid solution d: An 85% aqueous phosphoric acid solution (Merck, 85% phosphoric acid 100563) was diluted with water to obtain a 5.1% aqueous phosphoric acid solution. • Phosphoric acid aqueous solution e: An 85% phosphoric acid aqueous solution (Merck, 85% phosphoric acid 100563) was diluted with water to obtain a 4.25% phosphoric acid aqueous solution. • Phosphoric acid aqueous solution f: An 85% phosphoric acid aqueous solution (Merck, 85% phosphoric acid 100563) was diluted with water to make a 0.1% phosphoric acid aqueous solution (pH 1.1). • Phosphoric acid aqueous solution g: An 85% phosphoric acid aqueous solution (Merck, 85% phosphoric acid 100563) was diluted with water to make a 1% phosphoric acid aqueous solution (pH 0.59). • Trisodium phosphate aqueous solution: Na3PO4 (manufactured by Hayashi Pure Chemical Industries, Ltd., CAS RN: 7601-54-9) was prepared with water to make a 20% trisodium phosphate aqueous solution. • Silicate-based impregnation material: CS-21 manufactured by Aston Co., Ltd. (Na2O·nSiO2, solid content 25-35% by weight) • Calcium hydroxide aqueous solution: 5% calcium hydroxide dispersion (manufactured by Aston Co., Ltd., CS-21 builder aid)

[0031] [Concrete test specimen] Concrete (W / C: 52.4%, unit water content: 194 kg / m³) in a 100 x 100 x 400 mm formwork. 3 Unit cement content: 370 kg / m 3 The concrete was poured, cured for four weeks, then demolded, cut into 100 x 100 x 40 mm sections using a diamond cutter, and those that were 90 days or older were used as concrete test specimens.

[0032] Example 1 [Surface impregnated material] While stirring 1 kg of sodium silicate No. 3, 1 kg of phosphoric acid aqueous solution a (0.085%) was gradually added using a sprayer and mixed to obtain surface impregnation material a of Example 1.

[0033] [Surface water absorption test] On the entire bottom surface of the surface-dried concrete test specimen, and on the side surface 20 mm wide from the boundary between the bottom surface and the side surface, 0.1 kg / m² of surface impregnation material a from Example 1 was applied. 2The surface impregnating material a was applied once using a brush. At this time, the surface was applied with the application surface facing downwards to avoid applying too much material (see Figure 1). After air drying for 24 hours, a second application of surface impregnating material a was performed in the same manner as the first application. After the application was completed, a curing process was carried out, allowing it to air dry for 10 days. An 80 mm inner diameter water absorption cup was pressed and fixed to the underside of the concrete test specimen, which was the measurement surface. Water was poured from the center of the water absorption surface up to 30 cm from the tip of the scale, and the amount of water absorbed (g) that had dropped below the tip of the scale after 10 minutes was measured (see Figure 2).

[0034] [Neutralization acceleration test] Apply 0.1 kg / m² of surface impregnation material a from Example 1 to the entire surface of a surface-dried concrete test specimen. 2 The material was applied once by brush (see Figure 3). After air drying for 24 hours, a second application of surface impregnating material a was performed in the same manner as the first application. After application, a curing process was carried out, allowing for 10 days of air drying. The cured concrete specimens were placed in a carbonation acceleration test apparatus ("MIT-639", temperature 20±2℃, relative humidity 60±5%, CO2 concentration 5.0±0.2%) and subjected to a carbonation acceleration test for 45 days. The concrete specimens were removed from the carbonation acceleration test apparatus, cut, washed, air dried, and then sprayed with phenolphthalein solution to check for color development.

[0035] Example 2 While stirring 1 kg of sodium silicate No. 3, 1 kg of phosphoric acid aqueous solution b (0.85%) was gradually added using a sprayer and mixed to obtain surface impregnation material b for Example 2. Surface water absorption tests and neutralization acceleration tests were performed in the same manner as in Example 1, except that surface impregnation material b for Example 2 was used instead of surface impregnation material a for Example 1.

[0036] Example 3 While stirring 1 kg of sodium silicate No. 3, 1 kg of phosphoric acid aqueous solution c (2.55%) was gradually added using a sprayer and mixed to obtain surface impregnation material c for Example 3. A surface water absorption test was performed in the same manner as in Example 1, except that surface impregnation material c for Example 3 was used instead of surface impregnation material a for Example 1.

[0037] Example 4 While stirring 1 kg of sodium silicate No. 3, 500 g of phosphoric acid aqueous solution d (5.1%) was gradually added using a sprayer and mixed to obtain surface impregnation material d for Example 4. A surface water absorption test was performed in the same manner as in Example 1, except that surface impregnation material d for Example 4 was used instead of surface impregnation material a for Example 1.

[0038] Comparative Example 1 In Example 1, a surface water absorption test and a carbonation acceleration test were performed in the same manner as in Example 1, except that a curing process was carried out in which the surface impregnating material a was left untreated and allowed to air dry for 10 days.

[0039] Comparative Example 2 While stirring 1 kg of sodium silicate No. 3, 1 kg of phosphoric acid aqueous solution e (4.25%) was gradually added using a sprayer and mixed to obtain surface impregnation material e for Comparative Example 1. A surface water absorption test was performed in the same manner as in Example 1, except that surface impregnation material e for Comparative Example 1 was used instead of surface impregnation material a for Example 1.

[0040] Comparative Example 3 While stirring 1 kg of sodium silicate No. 3, 1 kg of trisodium phosphate aqueous solution (20%) was gradually added using a sprayer and mixed to obtain surface impregnation material f for Comparative Example 2. A surface water absorption test was performed in the same manner as in Example 1, except that surface impregnation material f for Comparative Example 2 was used instead of surface impregnation material a for Example 1.

[0041] Comparative Example 4 A surface water absorption test was conducted in the same manner as in Example 1, except that a phosphoric acid aqueous solution f (0.1%) was used instead of surface impregnation material a as in Example 1.

[0042] Comparative Example 5 A surface water absorption test and a neutralization acceleration test were performed in the same manner as in Example 1, except that a 1% aqueous phosphoric acid solution g was used instead of surface impregnation material a as in Example 1.

[0043] Comparative Example 6 A surface water absorption test and a neutralization acceleration test were performed in the same manner as in Example 1, except that a silicate-based impregnating material (CS-21, manufactured by Aston Co., Ltd.) was used instead of surface impregnating material a in Example 1.

[0044] Comparative Example 7 A surface water absorption test was conducted in the same manner as in Example 1, except that the first coating was performed using an aqueous phosphoric acid solution f (0.1%) instead of surface impregnating material a in Example 1, and the second coating was performed using a silicate-based impregnating material (CS-21, manufactured by Aston Co., Ltd.) instead of surface impregnating material a in Example 1.

[0045] Comparative Example 8 A surface water absorption test and a neutralization acceleration test were performed in the same manner as in Example 1, except that the first coating was performed using an aqueous phosphoric acid solution g (1%) instead of surface impregnating material a in Example 1, and the second coating was performed using a silicate-based impregnating material (CS-21, manufactured by Aston Co., Ltd.) instead of surface impregnating material a in Example 1.

[0046] Comparative Example 9 A surface water absorption test was conducted in the same manner as in Example 1, except that the first application was performed using an aqueous phosphoric acid solution f (0.1%) instead of surface impregnating material a from Example 1, and the second application was performed using surface impregnating material a from Example 1, with three applications using a 5% calcium hydroxide dispersion (Aston Co., Ltd., CS-21 builder aid).

[0047] Comparative Example 10 A surface water absorption test was conducted in the same manner as in Example 1, except that the first application was performed using an aqueous phosphoric acid solution g (1%) instead of surface impregnating material a from Example 1, and the second application was performed using surface impregnating material a from Example 1, with three applications using a 5% calcium hydroxide dispersion (Aston Co., Ltd., CS-21 builder aid).

[0048] [Table 1]

Claims

1. A concrete surface coating method in which a surface impregnating material is applied to the concrete surface, A concrete surface coating method characterized in that the surface impregnating material consists of an aqueous solution containing alkali metal silicate, phosphoric acid, and water, and the phosphoric acid content is 0.05 to 20 g per 1 kg of the surface impregnating material.

2. The concrete surface coating method according to claim 1, wherein a curing step of allowing the surface impregnating material to air dry for 24 hours or more is performed after application of the surface impregnating material.

3. The concrete surface coating method according to claim 1 or 2, wherein the pH of the surface impregnating material is 11.2 to 12.

2.

4. A surface impregnating material for coating a concrete surface by applying it to the concrete surface, A surface impregnating material comprising an aqueous solution containing alkali metal silicate, phosphoric acid, and water, characterized in that the phosphoric acid content is 0.05 to 20 g per 1 kg of the surface impregnating material.

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