Anti-efflorescence agent, ant-efflorescence method, and hydraulic composition

Abstract

To provide a means for preventing efflorescence occurring after hardening of a hydraulic component in a hydraulic composition containing a hydraulic component selected from cement, blast furnace slag, and fly ash, without using an organic component or forming a waterproof film on the surface.SOLUTION: The anti-efflorescence agent according to the present invention contains a hydraulic component selected from cement, blast furnace slag, and fly ash, and is an anti-efflorescence agent against efflorescence occurring after the hardening of a hydraulic composition capable of releasing sodium or calcium, it contains calcium sulfate anhydrite in an amount of 1 mass part or more to 11 mass parts or less based on 100 mass parts of the hydraulic component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an efflorescence prevention agent for preventing efflorescence that occurs after hardening of a hydraulic composition, a method for preventing efflorescence, and a hydraulic composition. [Background technology]

[0002] Concrete and other building materials (hardened bodies) are primarily composed of hydraulic components such as cement, blast furnace slag, and fly ash, and contain metal elements such as calcium and sodium. These metal elements are soluble and dissolve in rainwater, etc., and this solution migrates to the surface of the hardened body and reacts with carbon dioxide in the air, causing efflorescence. While efflorescence does not reduce the strength of the hardened body, it can lead to poor appearance. For hardened bodies used indoors, efflorescence can be prevented by adjusting environmental conditions such as temperature and humidity using air conditioning equipment. However, when used outdoors or semi-outdoors, it is difficult to prevent it by adjusting environmental conditions.

[0003] Since efflorescence occurs when metal elements dissolve in water and migrate to the surface of the cured product, waterproofing is commonly used as a countermeasure against efflorescence. For example, methods such as adding higher fatty acid salts (Patent Documents 1 and 2), using polyoxyalkylene-modified silicone in combination with a water-soluble polyvinyl copolymer (Patent Document 3), and combining a cellulose derivative with a polymer (Patent Document 4) are known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2-160647 [Patent Document 2] Japanese Patent Application Publication No. 11-60301 [Patent Document 3] Japanese Patent Application Publication No. 7-267712 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-83710 Summary of the Invention [Problem to be solved by the invention]

[0005] However, these methods cannot be used for cured products that have a shape that does not allow a waterproof film to be formed on the surface. Also, organic components may not be usable due to their non-flammability. Therefore, an object of the present invention is to provide a means for preventing efflorescence that occurs after hardening of a hydraulic component in a hydraulic composition containing a hydraulic component selected from cement, blast furnace slag, and fly ash, without using an organic component or forming a waterproof film on the surface. [Means for solving the problem]

[0006] The present inventors analyzed and investigated the efflorescence that formed after the hardening of a hydraulic composition containing a hydraulic component selected from cement, blast furnace slag, and fly ash, and concluded that sodium and calcium dissolved in the hydraulic composition slurry react with carbon dioxide in the air to form sodium carbonate and calcium carbonate, which then precipitate as the hydraulic composition dries, forming the efflorescence. The present inventors then discovered that the efflorescence phenomenon can be suppressed by adding a specific amount of anhydrous gypsum to the hydraulic composition, and completed the present invention.

[0007] That is, the present invention provides the following inventions [1] to [9]. [1] An efflorescence inhibitor for preventing efflorescence that occurs after hardening of a hydraulic composition that contains a hydraulic component selected from cement, blast furnace slag, and fly ash and can liberate sodium or calcium, the efflorescence inhibitor containing 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component. [2] The efflorescence prevention agent according to [1], which contains 1 part by mass or more and 7 parts by mass or less of anhydrous gypsum per 100 parts by mass of the hydraulic component. [3] The efflorescence prevention agent according to [1], which contains 3.4 to 6 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component. [4] A method for preventing efflorescence that occurs after hardening of a hydraulic composition that contains a hydraulic component selected from cement, blast furnace slag, and fly ash and that can liberate sodium or calcium, characterized by adding 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component. [5] A method for preventing efflorescence according to [4], in which 1 part by mass or more and 7 parts by mass or less of anhydrous gypsum is added per 100 parts by mass of the hydraulic component. [6] A method for preventing efflorescence according to [4], in which 3.4 to 6 parts by mass of anhydrous gypsum is added per 100 parts by mass of the hydraulic component. [7] A hydraulic composition containing a hydraulic component selected from cement, blast furnace slag, and fly ash, capable of liberating sodium or calcium, the hydraulic composition containing 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component. [8] The hydraulic composition according to [7], which contains 1 part by mass or more and 7 parts by mass or less of anhydrous gypsum per 100 parts by mass of the hydraulic component. [9] The hydraulic composition according to [7], which contains 3.4 parts by mass or more and 6 parts by mass or less of anhydrous gypsum per 100 parts by mass of the hydraulic component. [Effects of the Invention]

[0008] By using the anti-efflorescence agent of the present invention, it is possible to easily prevent the formation of efflorescence after curing without forming an organic film on the surface of the cured product, which is a problem with non-combustible materials. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a photograph showing the appearance of a test specimen. [Figure 2] The results of the correlation between the amount of anhydrous gypsum added and the area of ​​efflorescence under a humidity condition of 70% RH are shown. [Figure 3] The results of component analysis by X-ray diffraction of the efflorescence are shown below. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention relates to an efflorescence prevention agent for preventing efflorescence that occurs after hardening of a hydraulic composition containing a hydraulic component selected from cement, blast furnace slag, and fly ash, a method for preventing efflorescence, and the hydraulic composition. According to the present invention, if the hydraulic composition contains 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component, the efflorescence can be effectively suppressed. One aspect of the present invention is an efflorescence prevention agent for preventing efflorescence that occurs after hardening of a hydraulic composition that contains a hydraulic component selected from cement, blast furnace slag, and fly ash and can liberate sodium or calcium, and that contains 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component. Another aspect of the present invention is a method for preventing efflorescence that occurs after hardening of a hydraulic composition that contains a hydraulic component selected from cement, blast furnace slag, and fly ash and can liberate sodium or calcium, characterized by adding 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component. Another aspect of the present invention is a hydraulic composition that contains a hydraulic component selected from cement, blast furnace slag, and fly ash and is capable of liberating sodium or calcium, and that contains 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component.

[0011] In the present invention, the hydraulic composition to be prevented from efflorescence contains a hydraulic component selected from cement, blast furnace slag, and fly ash. Examples of cement include various types of portland cement, including ordinary, high-early-strength, ultra-high-early-strength, low-heat, and moderate-heat; cements whose main component is calcium silicate minerals, such as ecocement and belite cement, which are not included in portland cement (cements containing 50% or more by mass of calcium silicate minerals); various mixed cements in which cements whose main component is calcium silicate minerals are mixed with fly ash, blast furnace slag powder, silica fume, or limestone powder; ultra-fast-hardening cements such as "Super Jet Cement" (trade name) manufactured by Taiheiyo Cement Corporation and "Jet Cement" (trade name) manufactured by Sumitomo Osaka Cement Co., Ltd.; and alumina cement. One or more of these may be used. Blast furnace slag is a component of the upper layer that is produced when pig iron is produced from iron ore in a blast furnace, and includes air-cooled blast furnace slag and granulated blast furnace slag. Of these, mainly ground granulated blast furnace slag, which has high hydraulic hardness, is used. Fly ash is ash produced when coal is burned, and is used as a hydraulic component due to its high hydraulic properties.

[0012] These hydraulic compositions contain sodium ions and calcium ions in the water in the composition when they are in a slurry state before hardening or when they are exposed to rainwater or the like after hardening. When carbon dioxide in the air dissolves in the composition, sodium carbonate or calcium carbonate is produced, and as the composition dries, the sodium carbonate or calcium carbonate precipitates, causing efflorescence on the surface of the hardened body. Therefore, hydraulic compositions that cause efflorescence are those that can liberate sodium or calcium. Examples of building materials that are prone to efflorescence include concrete, mortar, brick, and geopolymers.

[0013] The content of the hydraulic components selected from cement, blast furnace slag and fly ash in the hydraulic composition varies depending on the type of hydraulic composition, but is preferably 5 to 100 mass %, more preferably 10 to 95 mass %, and even more preferably 20 to 90 mass % in total of the hydraulic composition.

[0014] Specific examples of hydraulic compositions include concrete, mortar, cement boards, building materials having a geopolymer reaction, etc. More specific examples include cement concrete, cement mortar, slate, slag gypsum boards, pulp cement boards, wood cement boards, ceramic siding, terrazzo, etc.

[0015] Other components contained in these hydraulic compositions include fine aggregate, coarse aggregate, calcareous raw materials, gypsum, calcium carbonate, sulfur, pulp, inorganic fibers, siliceous raw materials, admixtures, and the like.

[0016] In the present invention, from the viewpoint of preventing efflorescence that occurs after the hydraulic composition hardens, the hydraulic composition preferably contains 1 to 11 parts by mass of anhydrous gypsum relative to 100 parts by mass of the hydraulic component, more preferably 1 to 7 parts by mass of anhydrous gypsum, and even more preferably 3.4 to 6 parts by mass of anhydrous gypsum. If the content of anhydrous gypsum is less than 1 part by mass, the efflorescence prevention effect cannot be obtained, and if it exceeds 11 parts by mass, the amount of efflorescence will increase. As will be described in the Examples below, in a ground granulated blast furnace slag-water glass based insulation material, efflorescence caused by sodium carbonate, which occurs when sodium ions in the slurry react with carbon dioxide dissolved from the air, was suppressed by blending anhydrous gypsum. When the surface of the hardened material was subjected to component analysis by X-ray diffraction, it was found that the generation of sodium carbonate was suppressed, and the generation of sodium sulfate and burkeite (Na6CO3(SO4)2) was observed on the surface of the hardened material. It is believed that the generation of these compounds suppresses the generation of efflorescence. [Example]

[0017] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0018] (Preparation of test specimen) (1) Add ground granulated blast furnace slag and water glass to water to prepare a slurry. (2) The rock wool granules are defibrated in a defibrillator and then transported by air. They are mixed with the slurry prepared in (1) using a gun tip and sprayed into a box-shaped container (plastic container: 200 mm x 200 mm x depth 50 mm). (3) After adjusting the density of the material prepared in (2) to the specified value, apply only the slurry to the surface at a rate of 750 g / m 2 The test specimen was sprayed. The raw materials of the test specimens are shown in Table 1, and the standard test specimen conditions are shown in Table 2. Also, a photograph showing the appearance of the test specimens is shown in Figure 1.

[0019] [Table 1]

[0020] [Table 2]

[0021] (Test specimen conditions) Table 3 shows the test specimen conditions used to confirm the efflorescence reduction effect. The test specimens were prepared by adding 0, 3.4, 6.8, and 10.2 mass% of anhydrous gypsum to the ground granulated blast furnace slag, and the humidity was set at 70% RH.

[0022] [Table 3]

[0023] (Efflorescence occurrence confirmation test) The box-type specimens thus prepared were placed in a constant temperature and humidity chamber or a low-temperature constant temperature and humidity chamber to check the state of efflorescence on the surface of the specimen, the area of ​​efflorescence, and the weight of the specimen under each curing condition.The surface of the box-type specimen (200mm x 200mm) was divided into 100 squares, and the area of ​​efflorescence was calculated by defining a square in which efflorescence was observed in approximately 50% or more as 1%, and the state of efflorescence occurrence was evaluated (Table 4). The evaluation criteria for the occurrence of efflorescence were as follows: (Evaluation criteria) Efflorescence area is 9% or less (efflorescence is not noticeable) Efflorescence area: 10% to 29% (at a level where efflorescence is somewhat noticeable) Efflorescence area is 30% or more (the level at which efflorescence is clearly noticeable) (Test Method)

[0024] [Table 4]

[0025] (result) Figure 2 shows the correlation between the amount of anhydrous gypsum added and the area of ​​efflorescence under a humidity condition of 70% RH. Under all conditions, compared to 0% by mass of anhydrous gypsum added, the efflorescence area decreased when the amount added was 3.4% by mass, and when 6.8% by mass was added, it was the same as when no anhydrous gypsum was added at 10°C, but it decreased when 23% by mass was added.When 10.2% by mass was added, the increase in the amount of top coat of 2250g, which is the amount at which efflorescence is likely to occur, was the same as when no anhydrous gypsum was added, but it decreased when 750g was added. From the above results, it is considered that the amount of anhydrous gypsum to be added is preferably 1 to 11 mass %, more preferably 2 to 6 mass %, based on the total mass of the ground granulated blast furnace slag.

[0026] (Results of component analysis by X-ray diffraction) Since a large amount of efflorescence was observed when the anhydrous gypsum was added in amounts of 0 mass% and 10.2 mass%, and efflorescence was suppressed when the anhydrous gypsum was added in amounts of 3.4 mass% and 6.8 mass%, the efflorescence that occurred under each condition was collected and analyzed for its components by X-ray diffraction under the conditions shown in Table 5. Figure 3 shows the results of component analysis by X-ray diffraction of the efflorescence. When anhydrous gypsum was added at 0 mass%, only sodium carbonate was identified, whereas when 3.4 mass% was added, sodium carbonate and burkeite were identified, when 6.8 mass% anhydrous gypsum was added, sodium carbonate, burkeite, and sodium sulfate were identified, and when 10.2 mass% anhydrous gypsum was added, burkeite and sodium sulfate were identified.

[0027] [Table 5]

Claims

1. An efflorescence inhibitor for preventing efflorescence that occurs after hardening of a hydraulic composition that contains a hydraulic component selected from cement, blast furnace slag, and fly ash and can liberate sodium or calcium, the efflorescence inhibitor containing 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component.

2. The efflorescence inhibitor according to claim 1, comprising 1 part by mass or more and 7 parts by mass or less of anhydrous gypsum per 100 parts by mass of the hydraulic component.

3. The efflorescence inhibitor according to claim 1, comprising 3.4 parts by mass or more and 6 parts by mass or less of anhydrous gypsum per 100 parts by mass of the hydraulic component.

4. A method for preventing efflorescence that occurs after hardening of a hydraulic composition that contains a hydraulic component selected from cement, blast furnace slag, and fly ash and can liberate sodium or calcium, characterized by adding 1 part by mass or more and 11 parts by mass or less of anhydrous gypsum per 100 parts by mass of the hydraulic component.

5. The method for preventing efflorescence according to claim 4, wherein 1 part by mass or more and 7 parts by mass or less of anhydrous gypsum is added per 100 parts by mass of the hydraulic component.

6. The method for preventing efflorescence according to claim 4, wherein 3.4 parts by mass or more and 6 parts by mass or less of anhydrous gypsum is added per 100 parts by mass of the hydraulic component.

7. A hydraulic composition containing a hydraulic component selected from cement, blast furnace slag, and fly ash, capable of liberating sodium or calcium, the hydraulic composition containing 1 to 11 parts by mass of anhydrous gypsum per 100 parts by mass of the hydraulic component.

8. The hydraulic composition according to claim 7, comprising 1 part by mass or more and 7 parts by mass or less of anhydrous gypsum per 100 parts by mass of the hydraulic component.

9. The hydraulic composition according to claim 7, comprising 3.4 parts by mass or more and 6 parts by mass or less of anhydrous gypsum per 100 parts by mass of the hydraulic component.

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