JP6144603B2 - Freezing / salt scaling inhibiting method and freezing / salt scaling inhibiting agent - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a freeze / salt scaling suppression method and a freeze / salt scaling inhibitor, and in particular, a freeze / salt scaling suppression method and a freeze / salt scaling inhibitor for suppressing delamination deterioration of a cement hardened body surface by an antifreeze agent. About.

  There is a deterioration phenomenon called frost damage in concrete and mortar (hereinafter referred to as hardened cement) in cold regions. This freezing damage includes a tissue destruction due to expansion pressure caused by freezing of water inside the hardened cement body and a deterioration phenomenon called scaling that peels off the surface layer of the hardened cement body. There are various theories on the degradation mechanism due to scaling, and no countermeasure technology has been established.

  Falling temperatures and snowfall in winter can cause road roads to freeze and accumulate snow, impairing the safety of people and cars, and causing social congestion and economic impacts. In cold regions, anti-freezing agents (also called snow melting agents) are sprayed on roads to take measures against road freezing and snow accumulation.

  In general, water-soluble salts such as sodium chloride, calcium chloride, and magnesium chloride are used as antifreeze agents (see, for example, Patent Document 1). Since these lower the freezing point of water, they have the action of inhibiting freezing of water and melting of ice at low temperatures.

  However, it is known that this sprayed antifreeze aids the scaling of the cemented body, which is called salt scaling. The influence of salts on salt scaling is greatest for sodium chloride, followed by potassium chloride and magnesium chloride, and it is known that magnesium chloride has a small influence on salt scaling (for example, Non-Patent Document 1). , 2).

  Magnesium chloride is generally more expensive than sodium chloride, and its anti-freezing and snow melting effects are known to be less than half that of sodium chloride (see, for example, Non-Patent Document 3). This is because the antifreezing effect uses the freezing point depression phenomenon of water, and this phenomenon depends on the molar concentration of the dissolved salt.

In addition, magnesium chloride (MgCl ₂ ) has twice as many chlorine atoms in one molecule as sodium chloride (NaCl), so that the chloride ion concentration is 4 times or more in the application amount to obtain the same antifreezing effect. Therefore, there are concerns about secondary effects such as promoting corrosion of reinforcing bars and steel structures in the surrounding hardened cementitious structures. For this reason, it can be said that the use of only magnesium chloride as an antifreezing agent as a measure for salt scaling is problematic in terms of cost effectiveness and side effects.

JP 2004-59793 A (Claim 2, paragraphs 0047, 0048, etc.)

“Anti-freezing agent and snow melting agent“ magnesium chloride ”(flakes and sands)”, Yuki Chemical Co., Ltd. website (URL: http://www.yuki-chemical.com/yusetsu.html) “Anti-freezing agent”, Ako Kasei Corporation website (URL: http://web.ako-kasei.co.jp/business/kaseihin/touketsubousizai/) "About anti-freezing agents and anti-slip materials, Cold Region Road Research Group", Materials for Cold Region Civil Engineering Research Institute (URL: http://www2.ceri.go.jp/jpn/news/koutsu/panf/touketubousi.pdf)

  The use of anti-freezing agents is indispensable for ensuring road traffic safety, but at the same time, promoting the deterioration of hardened cementitious structures will incur social costs such as repairs. Therefore, there has been a demand for a freezing / salt scaling inhibiting method and a freezing / salt scaling inhibiting agent that are cost-effective and can suppress delamination deterioration of the cement hardened body surface due to salt scaling.

  The present invention has been made in view of the above problems, and is provided with a freezing / salt scaling inhibiting method and a freezing / salt scaling inhibiting agent that are cost-effective and capable of suppressing peeling degradation of the cement hardened body surface due to salt scaling. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have found that a water-soluble metal salt that reacts with an alkaline aqueous solution to form a metal hydroxide has a salt scaling suppressing effect, and the present invention. It came to.

  That is, the present invention is a freezing / salt scaling suppressing method for suppressing freezing of a cement hardened body surface and peeling deterioration due to salt, and is at least one selected from the group consisting of sodium salt, potassium salt and calcium salt An antifreeze containing no magnesium and a water-soluble metal salt containing at least one metal selected from the group consisting of magnesium, iron and aluminum and reacting with an alkaline aqueous solution to form a hydroxide of the metal Is applied to the surface of the hardened cement body, and a coating made of the metal hydroxide is formed between the surface of the hardened cement body and ice adhering to the surface of the hardened cement body. The present invention relates to a scaling suppression method.

  In this case, it is preferable that the application amount of the water-soluble metal salt with respect to the total amount of the antifreezing agent and the water-soluble metal salt is in the range of 10 to 90% by mass.

  The water-soluble metal salt is preferably at least one selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium acetate and magnesium nitrate.

  Furthermore, it is preferable that the water-soluble metal salt and the antifreezing agent are mixed in advance and dispersed in powder form.

  In addition, the present invention is a freezing / salt scaling inhibitor for suppressing freezing of a hardened cementite surface and deterioration due to salt, and at least one selected from the group consisting of sodium salt, potassium salt and calcium salt An antifreeze containing no magnesium and a water-soluble metal salt containing at least one metal selected from the group consisting of magnesium, iron and aluminum and reacting with an alkaline aqueous solution to form a hydroxide of the metal And a freezing / salt scaling inhibitor characterized by being in powder form.

  In this case, the content of the water-soluble metal salt with respect to the total amount of the antifreezing agent and the water-soluble metal salt is preferably in the range of 10 to 90% by mass.

  The water-soluble metal salt is preferably at least one selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium acetate and magnesium nitrate.

  ADVANTAGE OF THE INVENTION According to this invention, the freezing / salt scaling suppression method and freezing / salt scaling inhibitor which are excellent in freezing suppression effect and cost-effectiveness, and can suppress effectively the peeling deterioration of the cement hardening body surface by salt scaling efficiently Can be provided.

It is a graph which shows the relationship between the addition amount of a water-soluble metal salt, and a scaling durability index | exponent in an Example.

  The method for inhibiting freezing / salt scaling of the present invention is to spray a cryoprotectant and a water-soluble metal salt on the surface of a hardened cement body (hereinafter referred to as a spraying step), and to form a metal between the surface of the hardened cement body and ice adhering thereto. This is characterized in that a hydroxide film is formed (hereinafter referred to as a film forming process). Hereinafter, each component and process will be described in detail.

(1) Anti-freezing agent The anti-freezing agent of the present invention (hereinafter simply referred to as “anti-freezing agent”) contains at least one selected from the group consisting of sodium salt, potassium salt and calcium salt, and hardens cement. It has the role of making it easier to melt by lowering the freezing point of ice adhering to the body surface. Specific examples of the antifreezing agent include one selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, sodium acetate, sodium acetate, potassium acetate, and calcium acetate. Of these, sodium chloride and calcium chloride, which have a large freezing point depression (low freezing point) and are relatively inexpensive, are preferred. Moreover, as sodium chloride, a relatively inexpensive rock salt system is preferable.

(2) Water-soluble metal salt The water-soluble metal salt of the present invention (hereinafter simply referred to as “water-soluble metal salt”) contains at least one metal selected from the group consisting of magnesium, iron and aluminum, and contains an alkali. A salt that reacts with an aqueous solution to form a metal hydroxide. As will be described later, the water-soluble metal salt has a role of suppressing salt scaling by forming a film made of a metal oxide by reacting with an alkaline aqueous solution on the cement cured body surface. Specific examples of the water-soluble metal salt containing magnesium include one or more selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium acetate, and magnesium nitrate. Specific examples of the water-soluble metal salt containing iron include iron (II) chloride, iron (III) chloride, iron (II) sulfate, iron (III) sulfate, iron (II) acetate, iron nitrate ( II) and one or more selected from the group consisting of iron (III) nitrate. In addition, as the water-soluble metal salt containing aluminum, specifically, one kind selected from the group consisting of aluminum chloride / anhydride, aluminum chloride / hexahydrate, aluminum sulfate / hexahydrate, and aluminum acetate. The above can be mentioned. The water-soluble metal salt of the present invention includes not only anhydrides but also hydrates.

(3) Spraying step In the spraying step, the antifreezing agent and the water-soluble metal salt are sprayed on the surface of the hardened cement body. The antifreezing agent and the water-soluble metal salt may be sprayed in the form of an aqueous solution, but it is preferably sprayed in a powder state because the antifreeze and the water-soluble metal salt remain on the surface of the hardened cement body and exhibit the antifreezing effect continuously. Moreover, although an antifreezing agent and a water-soluble metal salt may be separately sprayed, it is preferable to spray simultaneously because it is easy to exhibit a salt scaling inhibitory effect. Furthermore, as will be described later, since the handleability and long-term storage stability are good, it is preferable to mix both in advance and spray in powder form.

  It is preferable that the application amount of the water-soluble metal salt is within a range of 10 to 90% by mass with respect to the total amount of the antifreezing agent and the water-soluble metal salt. When the amount of the water-soluble metal salt sprayed is less than 10% by mass, the freezing point depression is small (the freezing point is high), and the cement hardened body surface described later tends to be insufficiently coated with hydroxide. Moreover, when the application amount of the water-soluble metal salt exceeds 90% by mass, the cost tends to increase. The application amount of the water-soluble metal salt is more preferably 20% by mass or more, and further preferably 30% by mass or more. As shown in the examples described later, the salt scaling suppression effect indicated by the salt scaling durability index (SDI) is not so high until the application amount of the water-soluble metal salt is around 8 to 9% by mass, but it exceeds this. Thus, the SDI rapidly rises to about 100 by about 23 to 27% by mass, and is almost 100 after that, and remains constant at about 100.

  The spraying method of the antifreezing agent and the water-soluble metal salt is not particularly limited, and a known spraying method can be used. Such a spraying method may be manual spraying by hand, or mechanical spraying by a sprayer or a spreader. In addition, the timing of spraying is not particularly limited, such as the stage before snowfall or immediately after snowfall, the stage when the cement hardened body surface has frozen after the snowfall, the stage where the snow that has been crushed remains after removing snow, etc. Any timing is acceptable. In addition to the entire surface of the hardened cementitious body surface, the spraying locations include some locations that are particularly prone to freezing.

The application amount of the antifreeze and the water-soluble metal salt is not particularly limited as long as the freezing and salt scale can be sufficiently suppressed. For example, the antifreeze and the water-soluble metal salt are applied to the surface of the hardened cement. It is preferable to spray so that the total amount may become 3-50 g / m < ² >. When the application amount is less than 3 g / m ² , freezing suppression and salt scale suppression tend to be insufficient. On the other hand, when the application amount exceeds 50 g / m ² , the construction cost tends to be high, and the salt concentration becomes too high and the surface of the hardened cement body and its internal reinforcing bars are easily deteriorated.

(4) Film-forming step When a water-soluble metal salt is sprayed on the surface of the hardened cement body, a film made of a metal hydroxide is formed between the surface of the hardened cement body and ice attached thereto. The water-soluble metal salt of the present invention reacts with an alkaline aqueous solution to form a metal hydroxide, but the surface of the cement hardened body is adhered with water melted from ice, and the cement hardened body itself has a lime component. Since it is contained and is alkaline, the aqueous alkaline solution is infiltrated into the surface layer of the hardened cement body. When the water-soluble metal salt sprayed on the surface of the hardened cement body reacts with the alkaline aqueous solution, a gel-like film made of a metal hydroxide is formed on the surface of the hardened cement body. This film functions as a buffer layer at the interface between the hardened cement surface and ice, and the surface layer delamination caused by the stress difference is achieved by relieving the stress caused by the difference in thermal expansion coefficient between the hardened cement and ice. That is, it is estimated that salt scaling is suppressed. The metal hydroxide is magnesium hydroxide when the metal is magnesium and iron hydroxide when the metal is iron.

  The thickness of the coating is not particularly limited as long as the salt scaling can be sufficiently suppressed, but is preferably 5 μm or more, for example. When the thickness of the coating is less than 5 μm, it is difficult to sufficiently reduce the stress difference, and it is difficult to sufficiently suppress salt scaling. The presence or thickness of the coating layer can be measured by a technique such as observation with a scanning electron microscope (SEM).

  The salt contained in the antifreezing agent promotes the peeling deterioration of the cement hardened body surface due to frost damage (Salt Scaling). In the present invention, the water-soluble metal salt forms a hydroxide between the cement hardened body surface and ice. Since a film is formed, salt scaling can be suppressed. Moreover, since salt scaling is suppressed in this way, the generation | occurrence | production of the space | gap by salt scaling in a cement hardening body surface part can be suppressed. Therefore, it is also possible to suppress an increase in the porosity in the surface portion of the hardened cement body. Furthermore, freezing can be suppressed at low cost by using not only an expensive water-soluble metal salt but also a relatively inexpensive antifreezing agent.

  The hardened cement body of the present invention means a hardened cement as an adhesive component. The type of cement may be any of Portland cement, blast furnace cement, fly ash cement, silica cement and the like. Specific examples of the hardened cement body include the above-described concrete (cement + sand + gravel) and mortar (cement + sand), and AE agent, waterproofing agent, water reducing agent, water retention material, shrinkage reducing agent as necessary. , Foaming agents, quick setting agents, separation reducing agents, waterproofing agents, coloring agents, and the like are also added. In addition, examples of structures to which hardened cement is applied include almost all outdoor cement structures such as general roads, highways, bridges, railways, railway stations, harbors, airport runways, aprons, taxiways, etc. Can do.

(5) Freezing / Salt Scaling Inhibitor In the spraying step described above, a freezing / salt scaling inhibitor in which an antifreezing agent and a water-soluble metal salt are mixed in advance can also be used. Hereinafter, the freeze / salt scaling inhibitor (simply referred to as “freeze / salt scaling inhibitor”) of the present invention will be described.

  The freezing / salt scaling inhibitor contains the above-mentioned antifreezing agent and a water-soluble metal salt, and is characterized by being in a powder form. Water-soluble metal salts are deliquescent and tend to be moistened by absorbing moisture in the air. In such a state, the water-soluble metal salt powder is sticky and difficult to handle during storage or spraying. Therefore, in the present invention, the water-soluble metal salt having deliquescence and the antifreeze agent having no deliquescence or relatively low antifreezing agent are mixed in advance to be dispersed in the water-soluble metal salt antifreeze agent. It is in a state. As a result, even if the water-soluble metal salt is deliquescent due to moisture contained in the air, the water-soluble metal salt is not concentrated and dispersed, so that the powder is not sticky and remains relatively dry. Is done. For this reason, at the time of dispersion | spreading, it is excellent in handleability and long-term storage property also becomes favorable. In addition, mixing with an antifreezing agent and water-soluble metal salt can be performed by a well-known method using general purpose machines, such as a ribbon mixer and a mortar mixer.

  The content of the water-soluble metal salt is preferably in the range of 10 to 90% by mass with respect to the total amount of the antifreezing agent and the water-soluble metal salt. When the content of the water-soluble metal salt is less than 10% by mass, the freezing point depression is reduced (the freezing point is high), and the surface of the hardened cement body is likely to be insufficiently covered with hydroxide. In addition, when the content of the water-soluble metal salt exceeds 90% by mass, the cost tends to be high, and the handleability tends to be poor due to stickiness due to moisture in the air. The content of the water-soluble metal salt is more preferably 20% by mass or more, and further preferably 30% by mass or more. Generally, as the content of the water-soluble metal salt increases, the salt scaling suppression effect tends to increase.

The freezing / salt scaling inhibitor can be sprayed on the surface of the hardened cement body by the known spraying method described above. Similarly, it is preferable that the amount of the freezing / salt scaling inhibitor be 3 to 50 g / m ² with respect to the hardened cementitious surface.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, these do not limit the objective of this invention.

(1) Example 1 (calcium chloride + magnesium chloride)
An example using calcium chloride as the antifreeze and magnesium chloride as the water-soluble metal salt will be described.

(A) Preparation of freezing / salt scaling inhibitor Calcium chloride (Kanto Chemical Co., Ltd. calcium chloride) as an antifreezing agent and magnesium chloride (Wako Pure Chemical Industries, Ltd. magnesium chloride hexahydrate) as a water-soluble metal salt used. To 100 ml of the solution, 0.316 g of calcium chloride and 5.940 g of magnesium chloride as a water-soluble metal salt were mixed for 1 minute to prepare a freezing / salt scaling inhibitor (Example 1-1). Moreover, the freezing / salt scaling inhibitor of Examples 1-2 to 1-5 shown in Table 1 was prepared by changing the addition amount of magnesium chloride. Further, a sample containing only calcium chloride without adding magnesium chloride was also prepared (Comparative Example 1).
(B) Preparation of test specimen (mortar) Cement (ordinary Portland cement, density: 3.15 g / cm ³ ) and fine aggregate (crushed sand from Kurokawa, Morioka City, coarse grain ratio: 2.89, surface dry density: 2.80 g / cm ³ ) and water were mixed so that the water cement ratio was 0.5 and the sand cement ratio was 2.5. The fine aggregate used was a surface dry state under a 2.5 mm sieve. A JIS mortar specimen of 4x4x16cm was prepared without using AE agent, and after water curing until the age of 28 days, it was cut with a diamond cutter so that one side was 8mm. Was used as a test piece.

(C) Small piece freezing and thawing test A set of 3 pieces (about 4 g) of test pieces is placed in a 100 ml polypropylene container, and the mass ratio of the solution to the sample is 10: 1. The sample was dipped in and covered with a lid to conduct a freeze-thaw test. The specimen placed in the container was freeze-thawed 10 times in a freezer at -20 ° C for 12 hours and in a room at 15 ° C for 10 hours. After repeated cycles, the container was taken out, the sample was separated with filter paper (5B), and washed with pure water. The separated sample was dried at 40 ° C., and the sample was classified with a 2.5 mm sieve. Scaling resistance was quantitatively evaluated based on the remaining amount of the sample remaining on the sieve. Three sets of the above samples were used for one measurement, and the median value of the residual mass ratio among the three sets was used from the mass before the test. Also, the scaling durability test (SDI) is described in “Tetsuya Oyamada et al.,“ Examination of New Freezing and Thawing Test Method Considering Scaling Degradation ”, Concrete Engineering Annual Papers, 2011, vol. 33, pp. 935-940 ". Each sample and its measurement results are shown in Table 1. The addition amount is a value when the total amount of the cryoprotectant and the water-soluble metal salt is 100% by mass. It is.

  As described above, in Example 1-1 in which the amount of the water-soluble metal salt added was 8.7% by mass, the scaling durability index was 60.0, indicating that the durability against scaling was increased. Moreover, in Examples 1-2 to 1-5 in which the addition amount of the water-soluble metal salt is 26.9% by mass or more, the scaling durability index exceeds 99.0. It was found that the durability against scaling at the surface can be greatly increased.

(2) Example 2 (calcium acetate + magnesium acetate)
An example using calcium acetate as an antifreeze and magnesium acetate as a water-soluble metal salt will be described.

  In Example 1 (a), instead of calcium chloride, calcium acetate (calcium acetate monohydrate manufactured by Wako Pure Chemical Industries, Ltd.), magnesium acetate instead of magnesium chloride (magnesium acetate four manufactured by Wako Pure Chemical Industries, Ltd.) A freeze / salt scaling inhibitor was prepared in the same manner except that the amount of magnesium chloride added was variously changed. SDI was measured by the same specimen and test method as in Examples 1 (b) and (c). The results are shown in Table 2.

  As described above, in Examples 2-2 to 2-5 in which the addition amount of the water-soluble metal salt is 27.8% by mass or more, the scaling durability index is almost 100. It was found that the durability against scaling on the concrete surface can be greatly increased.

(3) Example 3 (sodium chloride + iron chloride)
In (a) of Example 1, instead of calcium chloride, sodium chloride (salt manufactured by the Salt Business Center), iron chloride (Kanto Chemical Co., Ltd.) iron chloride (iron (II) chloride tetrahydrate) instead of magnesium chloride The freezing / salt scaling inhibitor was prepared in the same manner except that the addition amount of sodium chloride and iron chloride was changed to 1: 1 (addition amount of iron chloride: 50% by mass). SDI was measured by the same specimen and test method as in Examples 1 (b) and (c), and as a result, the SDI value was 86.

(4) Example 4 (sodium chloride + aluminum chloride)
In Example 1 (a), sodium chloride of Example 3 was used instead of calcium chloride, and aluminum chloride (Kanto Chemical Co., Ltd. aluminum chloride (III) hexahydrate) was used instead of magnesium chloride. A freeze / salt scaling inhibitor was prepared in the same manner except that the addition amount of aluminum chloride was 1: 1 (amount of addition of aluminum chloride: 50% by mass). SDI was measured by the same specimen and test method as in Examples 1 (b) and (c). As a result, the SDI value was 78.

(5) Example 5 (sodium chloride + magnesium chloride)
In the same manner as in Example 1 (a), except that sodium chloride of Example 3 was used instead of calcium chloride, and the ratio (mass ratio) of sodium chloride and magnesium chloride was variously changed, and freeze / salt scaling was performed in the same manner. An inhibitor was created. SDI was measured by the same specimen and test method as in Examples 1 (b) and (c). The results are shown in Table 3.

  As described above, when the mass ratio of sodium chloride and magnesium chloride is 90:10 (Example 5-1) compared to the case of sodium chloride alone (Comparative Example 5), durability against scaling is improved. I found out. Therefore, it was found that the ratio of magnesium chloride to the total amount of sodium chloride and magnesium chloride is preferably 10% by mass or more. Further, the scaling durability index is improved as the ratio of magnesium chloride is increased. However, when the ratio of magnesium chloride is 50% by mass or more (Example 5-6 and Example 5-7), the scaling durability test index is almost 100. %. Therefore, it was found that the magnesium chloride ratio is particularly preferably 50% by mass or more.

(6) Example 6 (potassium chloride + magnesium chloride)
A freeze / salt scaling inhibitor was prepared in the same manner as in Example 1 (a) except that potassium chloride was used instead of calcium chloride and the ratio (mass ratio) of potassium chloride and magnesium chloride was variously changed. did. SDI was measured by the same specimen and test method as in Examples 1 (b) and (c). The results are shown in Table 4.

  As described above, compared to the case of potassium chloride alone (Comparative Example 6), when the mass ratio of potassium chloride to magnesium chloride is 90:10 (Example 6-1), durability against scaling is improved. I found out. Therefore, it was found that the ratio of magnesium chloride to the total amount of potassium chloride and magnesium chloride is preferably 10% by mass or more. Further, the scaling durability index is improved as the ratio of magnesium chloride is increased. However, when the ratio of magnesium chloride is 50% by mass or more (Example 6-6 and Example 6-7), the scaling durability test index is almost 100%. %. Therefore, it was found that the magnesium chloride ratio is particularly preferably 50% by mass or more.

Claims (7)

A freezing / salt scaling suppression method for suppressing freezing of a hardened cement surface and delamination deterioration due to salt,
An antifreeze containing at least one selected from the group consisting of sodium salt, potassium salt and calcium salt and containing no magnesium, and an alkali containing at least one metal selected from the group consisting of magnesium, iron and aluminum A water-soluble metal salt that reacts with an aqueous solution to become a hydroxide of the metal, and is spread on the surface of the cement cured body,
A method for inhibiting freezing / salt scaling, comprising forming a film made of the metal hydroxide between the surface of the hardened cement body and ice adhering to the surface of the hardened cement body.   The method for inhibiting freezing / salt scaling according to claim 1, wherein the amount of the water-soluble metal salt sprayed with respect to the total amount of the anti-freezing agent and the water-soluble metal salt is in the range of 10 to 90% by mass. .   The method for suppressing freezing / salt scaling according to claim 1 or 2, wherein the water-soluble metal salt is at least one selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium acetate and magnesium nitrate.   The method for suppressing freezing / salt scaling according to any one of claims 1 to 3, wherein the water-soluble metal salt and the antifreezing agent are mixed in advance and sprayed in powder form. A freezing / salt scaling inhibitor for suppressing freezing of the hardened cement surface and delamination deterioration due to salt,
A cryoprotectant containing at least one selected from the group consisting of sodium salts, potassium salts and calcium salts, and not containing magnesium;
A water-soluble metal salt containing at least one metal selected from the group consisting of magnesium, iron and aluminum and reacting with an alkaline aqueous solution to form a hydroxide of the metal, and is in powder form Freezing / salt scaling inhibitor.   The freezing / salt scaling inhibitor according to claim 5, wherein a content of the water-soluble metal salt with respect to a total amount of the anti-freezing agent and the water-soluble metal salt is in a range of 10 to 90% by mass. .   The freezing / salt scaling inhibitor according to claim 5 or 6, wherein the water-soluble metal salt is at least one selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium acetate and magnesium nitrate.

Images