Cement structure protective agent

Abstract

To provide a cement-based structure protective agent which can be easily applied and can improve the durability of a cement-based structure.SOLUTION: The cement-based structure protective agent contains an alkali silicate 21, a near infrared ray absorbing material 22 and a fine filler 23. The alkali silicate 21 imparts alkalinity to the cement structure 10 and forms a protective layer 20. Since the near infrared ray absorbing material 22 contained in the cement structure protective agent absorbs the near infrared ray irradiated to the cement structure 10, the temperature rise of the cement structure 10 is suppressed. When the average primary-particle size of the fine filler 23 is 5 to 100nm, the fine filler 23 enters the pores 11 on the surfaces of the cement structure 10 and blocks the pores 11 together with the alkali silicate 21, thereby suppressing the occurrence of efflorescence from the cement structure 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a protective agent for cement-based structures that can improve the durability of cement-based structures. [Background technology]

[0002] Cement-based structure protective agents capable of improving the durability of cement-based structures such as concrete structures have been known for some time. Patent Document 1 describes an aqueous penetrating composition containing sodium silicate and potassium methyl silicate. The cement-based structure protective agent is applied to the surface of a cement-based structure, coating the surface of the cement-based structure and thereby improving the durability of the cement-based structure.

[0003] However, cement-based structures have numerous pores on their surfaces, and therefore the cement-based structure protective agent described in Patent Document 1 has the problem that it may not be able to completely cover the surface of the cement-based structure, and may not be able to sufficiently improve the durability of the cement-based structure.

[0004] In contrast to this, Patent Document 2 describes a cement-based structure protective agent in which a primer layer, an intermediate coat layer, and a top coat layer are sequentially disposed on the surface of the substrate of a cement-based structure. This cement-based structure protective agent coats the surface of the cement-based structure with three coating layers, improving the durability of the cement-based structure. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-256350 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-020891 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the cement-based structure protective agent described in Patent Document 2 requires the sequential application of three types of paint to form a primer layer, an intermediate coat layer, and a top coat layer, which makes it difficult to apply easily.

[0007] In view of the above, an object of the present invention is to provide a cement-based structure protective agent that can be applied easily and can improve the durability of cement-based structures. [Means for solving the problem]

[0008] The cement-based structure protective agent according to an embodiment of the present specification contains an alkali silicate, a near-infrared absorbing material, and a fine filler, The fine filler is characterized in that its average primary particle size is 5 to 100 nm.

[0009] According to the cement-based structure protective agent of the embodiment of the present specification, the alkali silicate imparts alkalinity to the cement-based structure and forms a protective layer. The near-infrared absorbing material contained in the cement-based structure protective agent absorbs near-infrared rays irradiated onto the cement-based structure, thereby suppressing temperature rise in the cement-based structure and suppressing thermal creep of the cement-based structure. By having an average primary particle size of 5 to 100 nm, the fine filler penetrates into pores on the surface of the cement-based structure and blocks the pores together with the alkali silicate, thereby suppressing the occurrence of efflorescence from the cement-based structure. The cement-based structure protective agent of the embodiment can protect the cement-based structure with a single type of protective agent, making it easy to apply and improving the durability of the cement-based structure.

[0010] The cement-based structure protective agent may contain a water repellent agent.

[0011] According to this, the protective layer formed from the cement-based structure protective agent can suppress water penetration into the cement-based structure by the water repellent agent, thereby improving the durability of the cement-based structure.

[0012] The cement-based structure protective agent may contain a fluoride.

[0013] According to this method, calcium fluoride formed from calcium ions and fluorine ions in the cement-based structure penetrates into the countless pores on the surface of the cement-based structure and blocks the pores together with the alkali silicate and fine filler, thereby improving the durability of the cement-based structure.

[0014] In the cement-based structure protective agent, the fine filler may be silica particles.

[0015] According to this, the durability of cement-based structures can be improved because the fine filler of silica particles is chemically stable.

[0016] In the cement-based structure protective agent, the near-infrared absorbing material may be a metal oxide-based near-infrared absorbing material.

[0017] According to this, since the metal oxide-based near-infrared absorbing material is chemically stable, it is possible to improve the durability of the cement-based structure. [Effects of the Invention]

[0018] The cement-based structure protective agent of the embodiment can be easily applied and can improve the durability of the cement-based structure. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional image with a partially enlarged view showing the configuration of a cement-based structure to which a cement-based structure protective agent according to an embodiment has been applied. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the cement-based structure protective agent will be described below. The cement-based structure protective agent of this embodiment contains an alkali silicate 21, a near-infrared absorbing material 22, and a fine filler 23. The alkali silicate 21 imparts alkalinity to the cement-based structure 10 and forms a protective layer 20. The near-infrared absorbing material 22 contained in the cement-based structure protective agent absorbs near-infrared rays irradiated onto the cement-based structure 10, thereby suppressing a rise in temperature of the cement-based structure 10. The fine filler 23 has an average primary particle size of 5 to 100 nm, which allows the fine filler 23 to enter the pores 11 and cracks on the surface of the cement-based structure 10 and, together with the alkali silicate 21, block the pores 11 and cracks, thereby suppressing the occurrence of efflorescence from the cement-based structure 10.

[0021] Alkali silicate 21 refers to silicic acid dissolved in an alkaline solution, and is primarily composed of a substance represented by the general formula MO·nSiO (where M represents an alkali metal such as Li, Na, or K, and n represents a number from 1 to 8). Alkali silicate 21 is a syrup-like liquid, but when the water in the alkaline solution evaporates, it loses its fluidity and solidifies, forming protective layer 20. The solidified alkali silicate 21 not only blocks pores 11 in cement-based structure 10, but also functions as a binder (binding agent) that holds near-infrared absorbing material 22, which will be described in detail later.

[0022] Known examples of alkali silicates 21 include lithium silicate (LiO·nSiO), sodium silicate (NaO·nSiO), potassium silicate (KO·nSiO), and cesium silicate (CsO·nSiO). Commercially available products can be used. Among these alkali silicates 21, lithium silicate and sodium silicate are preferred. This is because lithium and sodium have small ionic radii, which facilitate the evaporation of water from the alkali silicate 21 and have high mobility, thereby facilitating the formation of the protective layer 20. In another embodiment, the alkali silicate 21 can be lithium silicate.

[0023] Since the alkali silicate 21 is an alkaline solution in which silicic acid is dissolved, it is hydrophilic and can be compatible with the cement-based structure 10, which uses cement hydrate, which is also hydrophilic, as a binder. Therefore, the alkali silicate 21 can coat the surface of the cement-based structure 10 and penetrate into the pores 11 and cracks to block them.

[0024] As the water in the alkaline solution evaporates, the alkali silicate 21 forms a protective layer 20, which coats the surface of the cementitious structure 10. The protective layer 20 blocks carbon dioxide from the outside of the cementitious structure 10 and also inhibits calcium and other components from leaking out of the cementitious structure 10. Therefore, the protective layer 20 prevents calcium components from coming into contact with carbon dioxide at the interface of the cementitious structure 10, thereby inhibiting the occurrence of efflorescence.

[0025] In the cement-based structure protective agent, the alkali silicate 21 is diluted with water or the like to a concentration of M2O·nSiO2 of 3 to 20 mass%. This is because the pores 11 of the cement-based structure 10 can be effectively blocked. If the concentration of M2O·nSiO2 is less than 3 mass%, the cement-based structure protective agent may become thin during hardening, which may prevent the pores 11 from being blocked. Furthermore, multiple applications may be required to fully block the pores 11, which may hinder convenient application. On the other hand, if the concentration of M2O·nSiO2 exceeds 20 mass%, the fluidity of the cement-based structure protective agent may be reduced, resulting in poor penetration into the pores 11. In another embodiment, the concentration of M2O·nSiO2 of the alkali silicate 21 in the cement-based structure protective agent may be 3.5 to 15 mass%. In yet another embodiment, the concentration may be 4 to 10 mass%.

[0026] The cement-based structure protective agent of the embodiment is obtained by adding a near-infrared absorbing material 22 and a fine filler 23 to an alkali silicate 21 .

[0027] The near-infrared absorbing material 22 is an additive that absorbs near-infrared rays (800 to 2500 nm) and suppresses the thermal creep phenomenon caused by sunlight on the cement-based structure 10. The cement-based structure 10 is heated by the far-infrared effect of near-infrared rays, causing thermal expansion and significant deformation, and the cement-based structure 10 is also damaged by the thermal expansion of water in the pores 11. Therefore, by including the near-infrared absorbing material 22 in the cement-based structure protective agent, the near-infrared rays of sunlight are absorbed by the near-infrared absorbing material 22 in the cement-based structure 10 to which the cement-based structure protective agent has been applied, and the thermal creep phenomenon caused by sunlight is suppressed.

[0028] A chemically stable inorganic near-infrared absorbing material 22 can be used as the near-infrared absorbing material 22. Examples of inorganic near-infrared absorbing materials 22 that can be used include carbon black, ITO (tin-doped indium oxide), ATO (antimony-doped tin oxide), and oxides, carbides, or borides of metals belonging to Group 4A, 5A, or 6A of the periodic table. These are commercially available products. In another embodiment, the near-infrared absorbing material 22 can be ITO or ATO, which have excellent near-infrared absorption efficiency, and in yet another embodiment, ATO.

[0029] The average primary particle diameter of the near-infrared absorbing material 22 can be 5 to 100 nm. By having an average primary particle diameter of the near-infrared absorbing material 22 of 5 to 100 nm, the protective layer 20 containing the near-infrared absorbing material 22 can be transparent without inhibiting the transmission of visible light, and the protective layer 20 can be made clear. If the average primary particle diameter of the near-infrared absorbing material 22 is less than 5 nm, the viscosity of the cement-based structure protective agent may increase, which may deteriorate the ease of application. On the other hand, if the average primary particle diameter of the near-infrared absorbing material 22 exceeds 100 nm, the protective layer 20 containing the near-infrared absorbing material 22 may inhibit the transmission of visible light and lack transparency. In another embodiment, the average primary particle diameter of the near-infrared absorbing material 22 can be 6 to 50 nm, and in yet another embodiment, it can be 7 to 20 nm.

[0030] Furthermore, the near-infrared absorbing material 22 may be a dye-based near-infrared absorbing material 22. Examples of the dye-based near-infrared absorbing material 22 that may be used include polymethine dyes (cyanine dyes), indolinocyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, naphthol metal complex dyes, squarylium dyes, triazo dyes, dithiol metal complex dyes, pyrylium dyes, thiapyrylium dyes, indoaniline dyes, azoanthraquinone dyes, naphthoquinone dyes, anthroquinone dyes, bis(dithiolene) dyes, triphenylmethane dyes, aminium (aluminum) dyes, and diimonium dyes.

[0031] The near-infrared absorbing material 22 can be contained in an amount of 0.5 to 5 mass% relative to the cement-based structure protective agent. This is because near-infrared rays can be absorbed favorably. If the content of the near-infrared absorbing material 22 relative to the cement-based structure protective agent is less than 0.5 mass%, near-infrared rays may not be absorbed favorably. On the other hand, if the content of the near-infrared absorbing material 22 exceeds 5 mass%, the effect may plateau, which may be uneconomical. In another embodiment, the content of the near-infrared absorbing material 22 relative to the cement-based structure protective agent may be 0.7 to 3 mass%, and in yet another embodiment, it may be 0.9 to 2 mass%.

[0032] In this embodiment, the fine filler 23 is a nano-sized filler (filling material). Examples of commercially available nano-sized fillers include silica particles, calcium carbonate particles, metal particles, and ceramic particles. The fine filler 23 penetrates into the pores 11 on the surface of the cement-based structure 10 and blocks the pores 11 together with the alkali silicate 21, preventing contact between the calcium content in the cement-based structure 10 and carbon dioxide in the outside air and suppressing the occurrence of efflorescence from the cement-based structure 10. Furthermore, the penetration of the fine filler 23 and the alkali silicate 21 into the pores 11 expels moisture from the pores 11. In another embodiment, the fine filler 23 can be silica particles, and fumed silica or aerosil can be used as the silica particles. These particles have a spherical or nearly spherical shape, which can improve the ease of application of the cement-based structure protective agent. Furthermore, the silica particles have the effect of suppressing the speed of settling and separation of the near-infrared absorbing material 22, which has a large specific gravity, in the state of a fluid cement-based structure protective agent.

[0033] The average primary particle diameter of the fine filler 23 can be 5 to 100 nm. By having the average primary particle diameter of the fine filler 23 be 5 to 100 nm, the cement-based structure protective agent containing the fine filler 23 can have excellent workability. Furthermore, the protective layer 20 containing the fine filler 23 having an average primary particle diameter of 5 to 100 nm can have transparency without inhibiting the transmission of visible light, and the protective layer 20 can be made clear. If the average primary particle diameter of the fine filler 23 is less than 5 nm, the viscosity of the cement-based structure protective agent may increase, making it difficult to improve application workability. On the other hand, if the average primary particle diameter of the fine filler 23 is more than 100 nm, the protective layer 20 containing the fine filler 23 may inhibit the transmission of visible light and lack transparency. In another embodiment, the average primary particle diameter of the fine filler 23 can be 6 to 50 nm, and in yet another embodiment, it can be 7 to 20 nm. The average primary particle diameter (nm) is expressed as the specific surface area (BET method) (m 2 / g), approximately 5nm≒400m 2 / g, 6nm ≒ 330m 2 / g, 7nm ≒ 290m 2 / g, 20nm≒100m 2 / g, 50nm ≒ 40m 2 / g, 100nm≒20m 2 / g, for example.

[0034] The fine filler 23 can be contained in an amount of 0.5 to 5 mass% relative to the cement-based structure protective agent. This is because the pores 11 can be blocked while ensuring the ease of application of the cement-based structure protective agent. If the content of the fine filler 23 relative to the cement-based structure protective agent is less than 0.5 mass%, there is a risk that the amount of fine filler 23 is too small and many of the pores 11 cannot be blocked. On the other hand, if the content of the fine filler 23 exceeds 5 mass%, the viscosity of the cement-based structure protective agent increases due to the fine filler 23, which may result in poor application workability of the cement-based structure protective agent. In another embodiment, the content of the fine filler 23 relative to the cement-based structure protective agent can be 0.7 to 3 mass%, and in yet another embodiment, it can be 0.9 to 2 mass%.

[0035] Furthermore, the cement-based structure protective agent of the embodiment may contain a water repellent 24 and / or a fluoride 25.

[0036] The water repellent agent 24 repels water and thereby inhibits water penetration into the cement-based structure 10. When the cement-based structure 10 is covered with the protective layer 20 formed from the cement-based structure protective agent, the contact angle of water is increased, and water penetration into the cement-based structure 10 is inhibited. Any known water repellent agent can be used, and examples of the water repellent agent 24 include those containing structures such as silane, siloxane, silazane, and siliconate, and commercially available products of these can be used.

[0037] The silane-based water repellent agent 24 is an organosilicon compound water repellent agent 24 represented by the following general formula (1). (chemical 1) R 1 n -Si-(OR 2 ) 4-n (1) (In the formula, R 1 is an alkyl group having 1 to 10 carbon atoms, R 2 represents an alkyl group having 1 to 2 carbon atoms or hydrogen, and n is 1 or 2. The siloxane-based water repellent agent 24 is a water repellent agent 24 having a Si—O—Si bond with a skeleton of silicon and oxygen. The degree of polymerization of silicon and oxygen can be 1-20.

[0038] The silazane-based water repellent agent 24 is a water repellent agent 24 having a Si—NH—Si bond in a skeleton of silicon and nitrogen.

[0039] The siliconate-based water repellent agent 24 is an organic silicate compound represented by the following general formula (2). (Case 2) R 1 n -Si-(OM) 4-n (2) (In the formula, R 1 is an alkyl group having 1 to 10 carbon atoms, and M is an alkali metal such as lithium, sodium, or potassium. The fluoride 25, together with the alkali silicate 21 and the fine filler 23, blocks the pores 11, improving the durability of the cement-based structure 10. Fluoride ions 25a of the fluoride 25 react with calcium ions 10a in the cement-based structure 10 to form calcium fluoride 26 (CaF2). The calcium fluoride 26 enters the pores 11 on the surface of the cement-based structure 10 and blocks the pores 11 together with the alkali silicate 21 and the fine filler 23, improving the durability of the cement-based structure 10. Any fluoride 25 that is soluble in the alkali silicate 21 can be used, and examples of such fluoride include potassium fluoride (KF) and sodium fluoride (NaF).

[0040] Next, a method for producing the cement-based structure protective agent of the embodiment will be described. The cement-based structure protective agent of the embodiment can be produced by diluting alkali silicate 21 with water, adding additives (near-infrared absorbing material 22, fine filler 23, water repellent 24, fluoride 25), and stirring until homogeneous.

[0041] The alkali silicate 21 in the cement-based structure protective agent is diluted with water or other raw materials so that the concentration of MO·nSiO is 3 to 20 mass %. This is because the pores 11 in the cement-based structure 10 can be effectively blocked, thereby improving the durability of the cement-based structure 10.

[0042] Next, a method for applying the cement-based structure protective agent of the embodiment to the cement-based structure 10 will be described. The cement-based structure protective agent is applied to the cement-based structure 10 using a spray, a brush, a wool roller, or the like. In another embodiment, a spray can be used, which is less likely to cause uneven application.

[0043] When the cement-based structure protective agent is applied to the cement-based structure 10, the alkali silicate 21 of the cement-based structure protective agent imparts alkalinity to the cement-based structure 10, suppresses neutralization of the cement-based structure protective agent, and improves the durability of the cement-based structure 10. Because the cement-based structure protective agent is hydrophilic, it blends in with the surface of the cement-based structure 10, which is also hydrophilic, and coats the surface of the cement-based structure protective agent, and the fine filler 23 penetrates into the pores 11 and cracks on the surface of the cement-based structure 10 and blocks the pores 11 and cracks together with the alkali silicate 21.

[0044] By closing the pores 11 and cracks, the cement-based structure 10 is shielded from carbon dioxide from the outside, the outflow of calcium from the cement-based structure 10 is inhibited, and the occurrence of efflorescence is inhibited. In addition, the penetration of the cement-based structure protective agent into the pores 11 and cracks expels moisture from within the pores 11 and cracks.

[0045] The near-infrared absorbing material 22 contained in the cement-based structure protective agent absorbs the near-infrared rays of sunlight, suppressing thermal expansion of the cement-based structure 10 due to the far-infrared effect, and also suppressing thermal expansion of moisture by expelling moisture from the pores 11 and cracks. As a result, the cement-based structure 10 is prevented from thermal creep caused by sunlight.

[0046] The protective layer 20 formed from the cement-based structure protective agent has transparency without impeding the transmission of visible light, because the alkali silicate 21 serves as a transparent binder, and the fine filler 23 has an average primary particle diameter of 5 to 100 nm, and the near-infrared absorbing material 22 has an average primary particle diameter of 5 to 100 nm.

[0047] Furthermore, when the cement-based structure protective agent contains a water repellent agent 24, the protective layer 20 formed on the cement-based structure 10 has water repellency, and water penetration into the cement-based structure 10 is inhibited. When the cement-based structure protective agent contains a fluoride 25, fluoride ions 25a of the fluoride 25 react with calcium ions 10a in the cement-based structure 10 to form calcium fluoride 26 (CaF2), which enters the pores 11 and cracks on the surface of the cement-based structure 10 and blocks the pores 11 and cracks together with the alkali silicate 21 and the fine filler 23, thereby improving the durability of the cement-based structure 10. [Example]

[0048] The formulations of the cement-based structure protective agents of the test examples and the test results are shown in Table 1. Test Examples 3, 4, 7 and 8 are working examples, Test Examples 1, 2, 5 and 6 are reference examples, and Test Example 9 is a comparative example.

[0049] [Table 1]

[0050] The raw materials used in the cement-based structure protective agent are listed below.

[0051] Alkali Silicate 21 Sodium silicate (sodium silicate No. 3 (manufactured by Nippon Chemical Industry Co., Ltd.)) (SiO2: 28-30%, Na2O: 9-10%) Lithium silicate (Lithium silicate 35 (manufactured by Nippon Chemical Industry Co., Ltd.)) (SiO2: 20-22%, Li2O: 2.8-3.1%) Near-infrared absorbing material 22 ATO powder (conductive powder T-1 (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.)) (Average primary particle size: 20nm) Micro Filler 23 Fumed silica (Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.)) (Average primary particle size: 12nm) Water repellent 24 Silicone water repellent (XIAMETER OFS-0772 (manufactured by Dow Toray Industries, Inc.)) (Non-volatile content: 30%) Fluoride 25 Sodium fluoride (Morita Chemical Industry Co., Ltd.) These are commercially available products.

[0052] <Test specimen> The cement-based structure 10 to be coated with the cement-based structure protective agent was a 120 x 120 x 25 mm cement mortar board prepared in accordance with JIS K 5600-1-4:2004 (General test methods for paints - Part 1: General rules - Section 4: Standard test boards for testing) 5.10 cement mortar board. In the examples, the cement-based structure protective agent shown in Table 1 was applied to the above cement mortar board at a rate of 100 g / m 2 The test specimens were then subjected to the following evaluation tests.

[0053] <Outdoor exposure test> The back and four sides of the test specimens were coated with epoxy resin (Quick Mender (Konishi Co., Ltd.)) and exposed outdoors for four years to check for the occurrence of efflorescence. The specimens were then rated as follows: ◯: no efflorescence was observed either visually or under a stereoscopic microscope; △: no efflorescence was observed visually but under a stereoscopic microscope; ×: no efflorescence was observed visually.

[0054] <Wear resistance test> After exposing the test specimens outdoors for four years, they were subjected to an abrasion resistance test according to JIS K 5600-5-9:1999 (General test methods for paints - Part 5: Mechanical properties of coatings - Section 9: Abrasion resistance (abrasion wheel method)) (abrasion wheel: CS-10 x 2, load: 1 kg x 2, rotation speed: 2000 rpm, n = 4). The abrasion loss was evaluated as follows: less than 1.0 mg = ◎, 1.0 mg to 1.5 mg = ○, 1.5 mg to 2.0 mg = △, and 2.0 mg or more = ×.

[0055] <Water absorption test> The test specimens, the back and four sides of which were coated with epoxy resin (Quick Mender (Konishi Co., Ltd.)), were immersed in water for 30 minutes, and the water absorption rates were measured before and after. Water absorption rates of less than 10% were evaluated as ◎, 10% to less than 15%, ○, 15% to less than 20%, and ×, respectively.

[0056] <Solar radiation penetration ratio> The solar radiation penetration ratio of the cement-based structure protective agent was calculated according to JIS K 5603:2017 (Thermal performance of coating film - Determination of solar radiation absorption rate by heat flow measurement method).The solar radiation penetration ratio of 0.8 or less was evaluated as ○, and the solar radiation penetration ratio of more than 0.8 was evaluated as ×.

[0057] <Water repellency> The water contact angle of the test specimens exposed outdoors for one year was measured and evaluated as follows: A contact angle of 90° or more was marked ○, a contact angle of 75° or more but less than 90° was marked △, and a contact angle of less than 75° was marked ×.

[0058] (Test Example 9) Test Example 9 is a test example in which the cement mortar board was not coated (applied) with a cement-based structure protective agent. Because the cement mortar board was not coated with a cement-based structure protective agent, the occurrence of efflorescence was visually confirmed in Test Example 9, and the abrasion loss in the abrasion resistance test was 2.0 mg or more, the water absorption rate in the water absorption test was 20% or more, the solar radiation penetration ratio was more than 0.8, and the water contact angle (as a measure of water repellency) was less than 75°.

[0059] (Test Example 1) Test Examples 1 to 4 are test examples in which lithium silicate was used as the alkali silicate 21. Test Example 1, which was a cement-based structure protective agent made of lithium silicate and did not contain the near-infrared absorbing material 22 and the fine filler 23, showed no visible efflorescence but was visible under a stereomicroscope, and the abrasion loss in the abrasion resistance test was 1.5 mg or more and less than 2.0 mg, the water absorption rate in the water absorption test was 10% or more and less than 15%, the solar radiation penetration ratio exceeded 0.8, and the water contact angle as a measure of water repellency was 75° or more and less than 90°. It is believed that the absence of the fine filler 23 prevented the pores 11 on the surface of the cement-based structure 10 from being blocked, resulting in somewhat poor results in the outdoor exposure test and the water absorption test.

[0060] (Test Example 2) Test Example 2 is a cement-based structure protective agent obtained by adding fine filler 23 to Test Example 1. Compared to Test Example 1, Test Example 2 had a water absorption rate of less than 10% in the water absorption test, and it is presumed that the fine filler 23 was able to block the pores 11 on the surface of the cement-based structure 10, resulting in an improvement in the water absorption test.

[0061] (Test Example 3) Test Example 3 is a cement-based structure protective agent obtained by adding near-infrared absorbing material 22 to Test Example 2. In Test Example 3, compared to Test Example 2, no efflorescence was observed visually or under a stereomicroscope, and the solar radiation penetration ratio was 0.8 or less due to the effect of the near-infrared absorbing material 22. In addition, although the reason is unclear, the abrasion weight loss in the abrasion resistance test was 1.0 mg or more and less than 1.5 mg, confirming an improvement.

[0062] (Test Example 4) Test Example 4 is a cement-based structure protective agent obtained by adding water repellent agent 24 to Test Example 3. Compared to Test Example 3, Test Example 4 showed improved water repellency, with a water contact angle of 90° or more due to the effect of water repellent agent 24. Furthermore, although the reason for this is unclear, the abrasion weight loss in the abrasion resistance test was less than 1.0 mg, confirming an improvement.

[0063] (Test Example 5) Test Examples 5 to 8 were test examples in which sodium silicate was used as the alkali silicate 21 and sodium fluoride was further contained as the fluoride 25. Test Example 5, a cement-based structure protective agent consisting of sodium silicate and sodium fluoride without containing the near-infrared absorbing material 22 and the fine filler 23, showed no visible efflorescence but was visible under a stereomicroscope. In the abrasion resistance test, the abrasion loss was 1.5 mg or more but less than 2.0 mg, the water absorption rate in the water absorption test was 10% or more but less than 15%, the solar radiation penetration ratio exceeded 0.8, and the water contact angle, as a measure of water repellency, was 75° or more but less than 90°. It is believed that the absence of the fine filler 23 prevented the pores 11 on the surface of the cement-based structure 10 from being blocked, resulting in somewhat poor results in the outdoor exposure test and water absorption test.

[0064] (Test Example 6) Test Example 6 is a cement-based structure protective agent obtained by adding fine filler 23 to Test Example 5. Compared to Test Example 5, Test Example 6 had a water absorption rate of less than 10% in the water absorption test, and it is presumed that the fine filler 23 was able to block the pores 11 on the surface of the cement-based structure 10, thereby improving the water absorption test. However, no difference in the effect of sodium fluoride (fluoride 25) could be confirmed in this test (water absorption test).

[0065] (Test Example 7) Test Example 7 is a cement-based structure protective agent obtained by adding near-infrared absorbing material 22 to Test Example 6. In Test Example 7, compared to Test Example 6, no efflorescence was observed visually or under a stereomicroscope, and the solar radiation penetration ratio was 0.8 or less due to the effect of the near-infrared absorbing material 22. In addition, although the reason is unclear, the abrasion weight loss in the abrasion resistance test was 1.0 mg or more and less than 1.5 mg, confirming an improvement.

[0066] (Test Example 8) Test Example 8 is a cement-based structure protective agent obtained by adding water repellent agent 24 to Test Example 7. It was confirmed that Test Example 8 had improved water repellency, with a water contact angle of 90° or more, due to the effect of water repellent agent 24, compared to Test Example 7.

[0067] (Other embodiments) The cement-based structure protective agent of the embodiment can also be implemented in the following forms.

[0068] In the cement-based structure protective agent of the embodiment, fumed silica is used as the fine filler 23, but titanium oxide (anatase type) can also be used as the fine filler 23. In this case, the photocatalytic action of anatase type titanium oxide can provide the surface of the cement-based structure 10 with antifouling properties, antibacterial properties, and the like.

[0069] In the embodiment of the cement-based structure protective agent, a cement-based structure 10 is used as an example of the object to be coated, but the cement-based structure protective agent can also be applied (applied) to gypsum moldings, stone materials, plaster walls, etc., to improve the durability of these objects.

[0070] (Other technical ideas) Other technical concepts that can be understood from the cement-based structure protective agent of the embodiment configured as described above will be described below.

[0071] The protective layer formed from the cement-based structure protective agent can be transparent and does not inhibit the transmission of visible light.

[0072] This makes it possible to improve the durability of the cement-based structure without impairing the appearance or design of the cement-based structure to which the cement-based structure protective agent is applied.

[0073] The near-infrared absorbing material contained in the cement-based structure protective agent may be ATO (antimony-doped tin oxide).

[0074] According to this, since ATO is chemically stable, the protective layer formed from the cement-based structure protective agent can exhibit the near-infrared absorbing effect for a long period of time. [Explanation of symbols]

[0075] 10 Cement-based structures 10a Calcium ion 11 pores 20 protective layer 21 Alkali silicate 22 Near-infrared absorbing material 23 Micro Filler 24 Water repellent 25 Fluoride 25a Fluoride ion 26 Calcium Fluoride

Claims

1. Contains alkali silicate, near-infrared absorbing material and fine filler, The cement-based structure protecting agent is characterized in that the average primary particle diameter of the fine filler is 5 to 100 nm.

2. 2. The cement-based structure protective agent according to claim 1, further comprising a water repellent.

3. 2. The cement-based structure protective agent according to claim 1, further comprising a fluoride.

4. 2. The cement-based structure protecting agent according to claim 1, wherein the fine filler is silica particles.

5. 2. The cement-based structure protective agent according to claim 1, wherein the near-infrared absorbing material is a metal oxide-based near-infrared absorbing material.

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