Method for suppressing road surface freezing

Abstract

Provided is a method for suppressing road surface freezing, the method comprising: a first step in which a freeze suppressing agent containing a metal salt compound of an organic acid is sprayed onto a road surface; and a second step in which a mortar containing a polymer emulsion, a solidifying material, and an aggregate is applied to the road surface to form a mortar layer.

Description

Road surface freezing suppression method

[0001] The present invention relates to a method for suppressing freezing of road surfaces such as road pavements.

[0002] In cold, snowy regions, the use of studded tires has been prohibited in a wider range of areas, and studless tires have become the mainstream winter tires. This has led to a decrease in skid resistance on snowy and icy roads, which has become a problem. For this reason, preventing road surfaces from freezing in winter has become an important issue from the perspective of traffic safety.

[0003] As a method for preventing road surface freezing, for example, Patent Document 1 discloses a method of spraying a freeze-inhibiting surface treatment mixture containing a metal salt compound of an organic acid, a polymer emulsion, a solidifying agent, and aggregate onto the road surface. However, the freeze-inhibiting surface treatment mixture has a short usable time, which makes it prone to clogging in the spraying machine. Furthermore, the freeze-inhibiting surface treatment mixture has a long hardening time, which may require heating the mixture using a burner or the like after spraying it onto the road surface. Furthermore, spraying requires a great deal of effort to protect the work area from contamination by scattered materials. Thus, the method using the freeze-inhibiting surface treatment mixture of Patent Document 1 has the problem of being difficult to apply due to the above factors. In addition, there is a need for further improvements in the freeze-inhibiting effect and the durability of the freeze-inhibiting effect.

[0004] Japanese Patent Application Laid-Open No. 2020-76210

[0005] The present invention has been proposed in consideration of the above, and aims to provide a method for preventing road surface freezing that can be easily implemented and can improve the anti-freezing effect and the sustainability of the anti-freezing effect.

[0006] As a result of intensive research into solving the above-mentioned problems, the inventors discovered that the above-mentioned problems can be solved by a road surface anti-freezing method comprising a first step of spraying an anti-freezing agent containing a metal salt compound of an organic acid onto a road surface, and a second step of applying mortar containing a polymer emulsion, a solidifying agent, and an aggregate onto the road surface, and thus completed the present invention.

[0007] [1] According to aspect 1 of the present invention, there is provided a method for suppressing road surface freezing, comprising a first step of spraying a road surface with an antifreeze agent containing a metal salt compound of an organic acid, and a second step of applying a mortar containing a polymer emulsion, a solidifying agent, and an aggregate to the road surface.

[0008] [2] According to a second aspect of the present invention, there is provided a method for suppressing road surface freezing according to the first aspect, in which the content of the metal salt compound of the organic acid in the antifreeze agent is 5 to 45% by weight.

[0009] [3] According to the third aspect of the present invention, in the first step, the amount of the antifreeze agent sprayed is 0.05 to 0.5 L / m ２ The method for suppressing road surface freezing according to aspect 1 or 2 is provided.

[0010] [4] According to the fourth aspect of the present invention, in the first step, the amount of the metal salt compound of the organic acid placed on the road surface by spraying the antifreeze agent is 2.5 to 225 g / m ２ The method for suppressing road surface freezing according to any one of Aspects 1 to 3 is provided.

[0011] [5] According to aspect 5 of the present invention, there is provided a method for suppressing road surface freezing according to any one of aspects 1 to 4, wherein in the second step, the thickness of the mortar layer is 0.2 to 4 mm.

[0012] [6] According to aspect 6 of the present invention, there is provided a method for suppressing road surface freezing according to any one of aspects 1 to 5, in which the second step is carried out 10 minutes to 2 hours after the first step.

[0013] [7] According to a seventh aspect of the present invention, there is provided the method for suppressing freezing of road surfaces according to any one of the first to sixth aspects, wherein the metal salt compound of an organic acid is a metal salt of a carboxylic acid.

[0014] [8] According to an eighth aspect of the present invention, there is provided the method for suppressing road surface freezing according to the seventh aspect, in which the metal salt compound of an organic acid is a metal salt of formic acid.

[0015] [9] According to a ninth aspect of the present invention, there is provided the method for suppressing road surface freezing according to any one of the first to eighth aspects, wherein the polymer emulsion is an emulsion of an acrylic ester polymer.

[0016] According to the present invention, a method for suppressing road surface freezing can be provided that can be easily carried out and can improve the anti-freezing effect and the durability of the anti-freezing effect.

[0017] Fig. 1 is a diagram for explaining the ice adhesion tensile test method, Fig. 2 is a graph showing the results of the ice adhesion tensile test, and Fig. 3 is a graph showing the results of the ice adhesion tensile test after the application of snow-melting agent.

[0018] The road surface anti-freezing method of this embodiment includes a first step of spraying an anti-freezing agent containing a metal salt compound of an organic acid onto a road surface, and a second step of applying mortar containing a polymer emulsion, a solidifying agent, and aggregate to the road surface. According to the road surface anti-freezing method of this embodiment, a mortar layer consisting of mortar containing a polymer emulsion, a solidifying agent, and aggregate is formed on the road surface onto which the anti-freezing agent has been sprayed. This makes it possible to impart an anti-freezing effect to road surfaces such as paved roads.

[0019] In the first step, an antifreeze agent containing a metal salt compound of an organic acid is sprayed onto the road surface. The antifreeze agent is an aqueous solution containing a metal salt compound of an organic acid. There is no particular limitation on the method for spraying the antifreeze agent onto the road surface, but an example is a method in which the antifreeze agent stored in a tank is pumped out and sprayed onto the construction area using a sprayer. Although there is no particular limitation, in order to fully exert the antifreeze effect of the present invention, it is preferable to clean the road surface with a blower or the like before the first step.

[0020] Metal salt compounds of organic acids are compounds that exhibit anti-freezing effects due to their freezing point depressing action. Such metal salt compounds of organic acids are not particularly limited as long as they are metal salts of organic acids, but examples include metal salts of carboxylic acids and metal salts of sulfonic acids. From the viewpoint of further enhancing the anti-freezing effect, metal salts of carboxylic acids are preferred. Furthermore, the carboxylic acid is not particularly limited, but examples include saturated aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, and caproic acid; saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, and maleic acid; hydroxycarboxylic acids such as lactic acid, malic acid, and citric acid; unsaturated aliphatic monocarboxylic acids such as acrylic acid, methacrylic acid, oleic acid, and linoleic acid; and aromatic carboxylic acids such as benzoic acid, phthalic acid, isophthalic acid, and terephthalic acid. Among these, saturated aliphatic monocarboxylic acids are preferred from the viewpoint of a high anti-freezing effect, with formic acid, acetic acid, and propionic acid being more preferred, and formic acid being particularly preferred.

[0021] Furthermore, the metal constituting the metal salt compound of an organic acid is not particularly limited, but examples include metals of Group 1 of the periodic table such as lithium, sodium, potassium, rubidium, and cesium, and metals of Group 2 of the periodic table such as beryllium, magnesium, calcium, strontium, and barium. Of these, from the viewpoint of being able to further enhance the anti-freezing effect, metals of Group 1 of the periodic table are preferred, with lithium, sodium, and potassium being more preferred, and sodium being particularly preferred.

[0022] The content of the metal salt compound of an organic acid in the antifreeze agent is preferably 5 to 45 wt %, more preferably 10 to 35 wt %, and even more preferably 15 to 25 wt %. By setting the content of the metal salt compound of an organic acid in the antifreeze agent within the above range, the antifreeze effect can be further enhanced.

[0023] The amount of antifreeze agent to be sprayed in the first step is preferably 0.05 to 0.5 L / m per unit area of ​​the road surface. ２ , more preferably 0.08 to 0.4 L / m ２ , and more preferably 0.1 to 0.3 L / m２ is.

[0024] The amount of the metal salt compound of an organic acid placed on the road surface in the first step is preferably 2.5 to 225 g / m2 in terms of the amount per unit area of ​​the road surface. ２ and more preferably 8 to 140 g / m ２ and more preferably 15 to 75 g / m ２ By setting the amount of the metal salt compound of an organic acid sprayed onto the road surface within the above range, the anti-freezing effect can be further enhanced. The amount of the metal salt compound of an organic acid placed on the road surface can be adjusted by adjusting the content of the metal salt compound of an organic acid in the anti-freezing agent and the amount of the anti-freezing agent sprayed.

[0025] In the second step, mortar containing a polymer emulsion, a solidifying agent, and aggregate (polymer cement mortar) is applied to the road surface onto which the antifreeze agent has been sprayed.

[0026] The polymer emulsion contained in the mortar is not particularly limited as long as it is a polymer dispersion in which a polymer is dispersed in water, and examples thereof include an acrylic polymer emulsion, a vinyl acetate polymer emulsion, a butadiene polymer emulsion, and a natural rubber emulsion.

[0027] Specific examples of the acrylic polymer emulsion include an emulsion of a (meth)acrylic acid ester polymer obtained by polymerizing a (meth)acrylic acid ester (meaning an acrylic acid ester and / or a methacrylic acid ester), and an emulsion of a (meth)acrylic acid ester-butadiene copolymer obtained by copolymerizing a (meth)acrylic acid ester and butadiene.

[0028] Specific examples of emulsions of vinyl acetate polymers include emulsions of ethylene-vinyl acetate copolymer (EVA) and emulsions of polyvinyl acetate (PVAC).

[0029] Specific examples of the butadiene polymer emulsion include an emulsion of a styrene-butadiene copolymer obtained by copolymerizing styrene and butadiene, and an emulsion of an acrylonitrile-butadiene copolymer obtained by copolymerizing acrylonitrile and butadiene.

[0030] Among the above-mentioned polymer emulsions, emulsions of acrylic polymers are preferred from the viewpoint of being able to further enhance the durability of the anti-freezing effect, and emulsions of acrylic ester polymers obtained by polymerizing acrylic esters are more preferred.

[0031] The glass transition temperature (Tg) of the polymer contained in the polymer emulsion is preferably less than 0°C, more preferably -10°C or lower, and particularly preferably -20°C or lower, from the viewpoint of further increasing the durability of the anti-freezing effect.

[0032] The proportion of the polymer in the polymer emulsion (proportion of solids) is not particularly limited, but is preferably 20 to 70% by mass, more preferably 30 to 50% by mass, and even more preferably 35 to 45% by mass.

[0033] The content of the polymer emulsion in the mortar is preferably 20 to 70 parts by weight, more preferably 30 to 50 parts by weight, and even more preferably 35 to 45 parts by weight, relative to 100 parts by weight of aggregate. By setting the content of the polymer emulsion within the above range, the durability of the anti-freezing effect can be further increased.

[0034] The solidifying agent contained in the mortar may be any material that can harden upon reaction with the water contained in the polymer emulsion, and for example, cement can be suitably used. The cement is not particularly limited, and examples include Portland cements such as ultra-rapid-hardening cement, extra-high-early-strength Portland cement, early-strength Portland cement, and ordinary Portland cement, mixed cements such as blast-furnace cement and fly ash cement, and ecocement. Among these, from the viewpoint of early traffic opening, ultra-rapid-hardening cement, extra-high-early-strength Portland cement, and early-strength Portland cement are preferred, and ultra-rapid-hardening cement is more preferred.

[0035] The content of the hardening agent in the mortar is preferably 20 to 60 parts by weight, more preferably 30 to 50 parts by weight, and even more preferably 35 to 45 parts by weight, per 100 parts by weight of aggregate.

[0036] The aggregate contained in the mortar is not particularly limited, and crushed stone, sand, stone powder, and other aggregates commonly used in ordinary road paving can be used as appropriate, but from the viewpoint of improving the applicability of the antifreeze surface treatment mixture for road surfaces of the present invention when applied to road surfaces such as paved roads, fine aggregates such as silica sand, river sand, mountain sand, land sand, sea sand, and crushed sand are preferred. Furthermore, the aggregate preferably contains 0 to 50% by mass of aggregate having a particle size of 0.6 mm or less, and more preferably 10 to 30% by mass of aggregate having a particle size of 0.6 mm or less.

[0037] In addition to the above, the mortar may contain additives commonly used in paved road surfaces, such as hardening accelerators, fluidizing agents, antifoaming agents, retarders, fillers, vegetable fibers, pigments, etc., as long as the effects of the present invention are not impaired. Mortar can be produced by mixing the above components.

[0038] The method for applying mortar to the road surface is not particularly limited, but examples include a method in which mortar mixed with a hand mixer or the like is placed within the construction area and then spread evenly using a rubber rake or the like, or a method in which mortar is spread evenly while being applied using a vehicle equipped with a mixing device and / or a spreader box.

[0039] The thickness of the mortar layer formed in the second step is preferably 0.2 to 4 mm, more preferably 0.5 to 3 mm, and even more preferably 1 to 2 mm. The thickness of the mortar layer can be adjusted by adjusting the blending ratio of the components contained in the mortar or by spreading the mortar evenly to a desired thickness when applying the mortar.

[0040] The thickness of the mortar layer formed in the second step is not particularly limited, but is preferably 0.0008 to 1.6 mm / (g / m) in terms of the thickness relative to the amount of the metal salt compound of an organic acid placed on the road surface per unit area in the first step. ２ ), and preferably 0.003 to 0.38 mm / (g / m ２ ), and more preferably 0.01 to 0.14 mm / (g / m ２ By setting the ratio of the thickness of the mortar layer relative to the amount of the metal salt compound of an organic acid within the above range, the anti-freezing effect of the anti-freezing agent and the durability of the anti-freezing effect can be further improved.

[0041] Although not particularly limited, the second step is preferably carried out 10 minutes to 2 hours, more preferably 30 minutes to 1 hour, after the first step. By carrying out the second step a predetermined time after the first step, the mortar can be properly hardened, and the anti-freezing effect of the anti-freezing agent and the durability of the anti-freezing effect can be further enhanced.

[0042] In the second step, after the mortar has been applied, it is preferable to cure the mortar as necessary to harden it.

[0043] In the road surface anti-freezing method of this embodiment, a first step involves spraying an anti-freezing agent containing a metal salt compound of an organic acid onto the road surface, and a second step involves applying mortar containing a polymer emulsion, a solidifying agent, and an aggregate. This allows the balance between the usable life and hardening time of the mortar to be appropriately adjusted using a mortar with a desired composition, making the mortar easier to handle and enabling simple construction.

[0044] In addition, in this embodiment, by forming a mortar layer on the antifreeze agent sprayed on the road surface, the durability of the antifreeze effect of the antifreeze agent can be improved. Although the reason for this is not clear, it is thought that the mortar layer acts as a sealing layer, improving the sustained release of the metal salt compound of an organic acid contained in the antifreeze agent.

[0045] Furthermore, the mortar layer formed using the above mortar has fine voids on the surface and inside. Therefore, the antifreeze agent sprayed in the first step can seep out from the voids in the mortar layer formed in the second step to the surface of the mortar layer. Therefore, according to the road surface antifreeze method of this embodiment, the antifreeze effect of the antifreeze agent can be effectively exerted.

[0046] Furthermore, when a deicing agent such as calcium chloride is spread on a road surface to which the road surface anti-freezing method of this embodiment has been applied, the mortar layer has minute voids, which make it easy for the deicing agent to be retained on the road surface. Therefore, the road surface anti-freezing method of this embodiment can improve the durability of the deicing agent's effectiveness.

[0047] Due to the above features, the road surface freezing suppression method of this embodiment can be suitably used on road surfaces in cold regions and other areas where road surfaces are prone to freezing in winter.

[0048] The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

[0049] <Comparative Example 1> The dense-graded asphalt mixture (13) was used and placed in a mold (formwork) heated to the compaction temperature, and then compacted (50 times on both sides) to obtain a specimen of the dense-graded asphalt mixture (13). This was used as the specimen for Comparative Example 1.

[0050] Example 1: A freeze inhibitor with a sodium formate concentration of 20% by weight was prepared by adding sodium formate as a metal salt compound of an organic acid to water and mixing. Next, 23.0 parts by weight of an acrylic acid ester polymer emulsion (aqueous dispersion of a polymer obtained by polymerizing an acrylic acid ester, polymer solids content: 38% by weight, polymer glass transition temperature (Tg): -52°C) was mixed in a mixer with 22 parts by weight of cement (ultra-rapid hardening cement) as a solidifying agent, and 55.0 parts by weight of fine aggregate (grain size 1.7 mm or less, proportion of fine aggregate with a grain size of 0.6 mm or less in the total amount of fine aggregate: 22% by weight) to prepare mortar.

[0051] Next, the above antifreeze agent was sprayed onto the surface of a test piece of dense-graded asphalt mixture (13) obtained in the same manner as in Comparative Example 1 at a rate of 0.2 L / m using a sprayer. ２ That is, 40 g / m was sprayed on the surface of the test specimen. ２ After one hour had passed since the antifreeze agent was sprayed, the above mortar was applied to a thickness of approximately 1 mm on the surface of the test specimen where the antifreeze agent had been sprayed, forming a mortar layer. The test specimen was then cured at room temperature for two hours to harden the mortar. This was used as the test specimen for Example 1.

[0052] <Comparative Example 2> A mixture containing sodium formate was obtained in the same manner as the mortar in Example 1, except that sodium formate was further added as a metal salt compound of an organic acid. The obtained mixture was sprayed at 0.7 MPa using a lysine gun onto the surface of a specimen of dense-graded asphalt mixture (13) obtained in the same manner as in Comparative Example 1, and left to stand at room temperature for 2 hours to form a film with a thickness of about 1 mm, which was used as the specimen of Comparative Example 2. The amount of sodium formate added during the preparation of the mixture was 40 g / m², so that the amount of sodium formate sprayed on the surface of the specimen when the mixture was made into a film with a thickness of about 1 mm. ２The amount was set to be:

[0053] <Icing Tensile Test> In accordance with the "Measurement Method Using a Tensile Tester to Determine Icing Tensile Strength" described in the "Pavement Performance Evaluation Method Supplement" (Japan Road Association, March 2008), the anti-freezing effect was evaluated indoors for the test specimens of Example 1, Comparative Example 1, and Comparative Example 2. Note that Figure 1 shows the method of the icing tensile test.

[0054] Specifically, the test temperature was first set to -5°C, and a thin ice film was formed on the surface of the test specimen 10. Next, a measuring jig 20 with a nonwoven fabric 30 attached was prepared. The nonwoven fabric 30 attached to the measuring jig 20 was saturated with water and placed on the surface of the test specimen 10. Next, the test specimen 10 was cured for 4 hours in an environment of -5°C with a load of 4 kPa applied to the surface of the test specimen 10, and then the load was removed. A rubber plate 40 was placed on top of the measuring jig 20, and a 420 g steel ball was dropped onto it from a height of 25 cm 10 times. The measuring jig 20 was then removed from the test specimen 10, and the maximum load when the measuring jig 20 was removed was measured, which was taken as the ice adhesion tensile strength. The smaller the ice adhesion tensile strength, the higher the anti-freeze effect. Furthermore, to evaluate the durability of the anti-freeze effect, the same test specimen was repeatedly subjected to ice adhesion tensile tests. If the ice adhesion tensile strength does not increase significantly even after repeated tests, it can be determined that the anti-freeze effect is highly durable. Alternatively, even if the tensile strength of ice adhesion increases significantly as a result of repeated testing, the greater the number of tests at which the tensile strength increases significantly, the more durable the anti-freezing effect can be determined. The measurement results are shown in Figure 2.

[0055] As shown in Figure 2, the test specimen of Example 1, which used sodium formate as the metal salt compound of an organic acid, showed a significantly reduced freezing tensile strength compared to the test specimen of the dense-graded asphalt mixture (13), demonstrating an excellent anti-freezing effect.

[0056] <Evaluation of durability of the effect of snow-melting agent> The surface of the test specimen of Example 1 was exposed to running water for two days to wash out the sodium formate from the surface of the test specimen. The test specimen was subjected to the ice adhesion tensile test in the same manner as above. Next, an aqueous calcium chloride solution containing calcium chloride as a snow-melting agent was applied to the test specimen so that the amount of calcium chloride on the surface of the test specimen was 20 g / m. ２ The de-icing agent was sprayed onto the surface of the test specimen after the de-icing tensile test so that the de-icing tensile strength was equal to or greater than 100%. The de-icing tensile test was repeatedly performed on the test specimens after the spraying of the calcium chloride aqueous solution. In the de-icing tensile test after the spraying of the calcium chloride aqueous solution, the greater the number of tests at which the de-icing tensile strength increased significantly, the more durable the de-icing agent's effect can be judged to be. The de-icing agent's durability was also evaluated for the test specimen of Comparative Example 1. The measurement results are shown in Figure 3. In Figure 3, the result for number 1 represents the result after the test specimen surface was exposed to running water for two days. In Figure 3, the results for number 2 to 6 represent the results after the calcium chloride aqueous solution was sprayed onto the test specimen surface.

[0057] As shown in Figure 2, the specimen of Example 1, obtained by spraying a freeze-inhibiting agent containing a metal salt compound of an organic acid and then applying a mortar containing a polymer emulsion, a solidifying agent, and an aggregate to form a mortar layer, had a low freeze-inhibiting tensile strength and an excellent freeze-inhibiting effect (particularly the results of the first test). Furthermore, even when the specimen of Example 1 was subjected to repeated freeze-inhibiting tensile tests, the freeze-inhibiting tensile strength did not increase significantly, and the freeze-inhibiting effect was also excellent in durability.

[0058] On the other hand, the specimens of Comparative Example 1, which were not sprayed with antifreeze agent, and Comparative Example 2, which was obtained by spraying a mixture containing a metal salt compound of an organic acid, a polymer emulsion, a solidifying agent, and an aggregate, had high icing tensile strength and poor antifreeze effect. Furthermore, the specimens of Comparative Example 1 and Comparative Example 2 showed a large increase in icing tensile strength after repeated icing tensile tests, and the durability of the antifreeze effect was poor.

[0059] Furthermore, as shown in Figure 3, the test specimen of Example 1 was subjected to repeated ice adhesion tensile tests after the sodium formate (metal salt compound of an organic acid) was drained out and an aqueous calcium chloride solution (snow-melting agent) was sprayed on it. This showed that the ice adhesion tensile strength did not increase significantly, demonstrating that the snow-melting agent had excellent durability of effect.

Claims

1. A method for preventing freezing on road surfaces, comprising: a first step of spraying an anti-freezing agent containing a metal salt compound of an organic acid onto a road surface; and a second step of applying mortar containing a polymer emulsion, a solidifying agent, and an aggregate onto the road surface to form a mortar layer.

2. A method for suppressing freezing of road surfaces as described in claim 1, wherein the content of the metal salt compound of the organic acid in the antifreeze agent is 5 to 45% by weight.

3. In the first step, the amount of the antifreeze agent sprayed is 0.05 to 0.5 L / m ２ 3. The method for suppressing freezing of road surfaces according to claim 1 or 2.

4. In the first step, the amount of the metal salt compound of the organic acid placed on the road surface by spraying the antifreeze agent is 2.5 to 225 g / m ２ The method for suppressing road surface freezing according to any one of claims 1 to 3.

5. A method for suppressing road surface freezing as described in any one of claims 1 to 4, wherein in the second step, the thickness of the mortar layer is 0.2 to 4 mm.

6. A method for suppressing freezing of road surfaces as described in any one of claims 1 to 5, wherein the second step is carried out 10 minutes to 2 hours after the first step.

7. A method for preventing freezing of road surfaces according to any one of claims 1 to 6, wherein the metal salt compound of an organic acid is a metal salt of a carboxylic acid.

8. A method for suppressing freezing of road surfaces according to claim 7, wherein the metal salt compound of an organic acid is a metal salt of formic acid.

9. A method for suppressing freezing of road surfaces according to any one of claims 1 to 8, wherein the polymer emulsion is an emulsion of an acrylic ester polymer.

10. A method for suppressing freezing of road surfaces according to any one of claims 1 to 9, wherein the antifreeze agent is an aqueous solution containing a metal salt compound of the organic acid.

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