WO2022149613A1

WO2022149613A1 - Pavement mixture and pavement binder

Info

Publication number: WO2022149613A1
Application number: PCT/JP2022/000439
Authority: WO
Inventors: 貞治上野; 麻衣高木
Original assignee: ニチレキ株式会社
Priority date: 2021-01-08
Filing date: 2022-01-07
Publication date: 2022-07-14
Also published as: TW202241827A; JPWO2022149613A1

Abstract

The present invention addresses the problem of providing: a pavement mixture which can be easily handled at normal temperature or lower and which develops excellent strength in a relatively short time after being laid; and a pavement binder which can be used in this type of pavement mixture. This problem can be solved by providing: a pavement binder which is obtained by being mixed with an aggregate and which is characterized by containing a polysaccharide that forms a gel upon contact with a divalent or higher metal ion; and a pavement mixture which contains an aggregate and the pavement binder.

Description

Pavement mixtures and pavement binders

The present invention relates to a pavement mixture and a pavement binder.

Asphalt pavement is the most widely used pavement and is usually constructed by spreading and compacting a heated asphalt mixture obtained by heating and mixing aggregate and asphalt. When the temperature drops after the heated asphalt mixture is laid, the viscosity of the asphalt contained in the heated asphalt mixture increases and the aggregates are firmly adhered to each other to form a pavement having excellent strength. In this way, asphalt pavement is constructed by skillfully utilizing the temperature-dependent adhesive behavior of asphalt. However, since asphalt has a property that the viscosity increases significantly when the temperature decreases, the handleability of the heated asphalt mixture deteriorates remarkably when the temperature becomes 100 ° C. or lower. Therefore, when constructing using a heated asphalt mixture, the heated asphalt mixture produced in the asphalt plant must be transported to the construction site in a high temperature state or reheated at the construction site before use. It was very laborious and costly.

On the other hand, as an asphalt mixture that can be constructed even at a temperature of 100 ° C. or lower, a room temperature asphalt mixture using cutback asphalt has been proposed. Cutback asphalt is made by mixing asphalt with a cutback agent that is a volatile oil (for example, gasoline, kerosene, heavy oil, etc.) to make the asphalt liquid, and has the advantage of being easy to install even at room temperature. There is. However, pavement constructed using a room temperature asphalt mixture cannot exhibit sufficient strength unless the cutback agent, which is a diluting component of asphalt, volatilizes sufficiently, so the strength immediately after construction is higher than that of a heated asphalt mixture. There is a drawback of being inferior. However, it is not always easy to secure sufficient curing time after construction at an actual construction site where early traffic opening is required.

On the other hand, various room temperature asphalt mixtures have been developed to exhibit sufficient strength at an early stage. For example, in Patent Document 1, an aggregate, asphalt, and kerosene and 1- as a cutback agent are used. A room temperature asphalt mixture containing bromopropane is disclosed. According to Patent Document 1, since the volatility of the cutback agent is improved by mixing 1-bromopropane, it is said that the room temperature asphalt mixture can exhibit sufficient strength at an early stage. However, the room temperature asphalt mixture described in Patent Document 1 requires a relatively long period of time to develop its strength, and it cannot be said that its curing rate is sufficient.

Further, as described above, since the viscosity of asphalt increases as the temperature decreases, a normal temperature asphalt mixture using asphalt as the main component of the binder for adhering the aggregate is used in an environment lower than normal temperature, for example, in winter. In cold regions and the like, the increase in viscosity is remarkable, and there is a drawback that the workability is poor. Attempts have been made to increase the fluidity of the room temperature asphalt mixture by increasing the amount of the cutback agent added, but as the amount of the cutback agent increases, a longer volatilization time is required. As far as the present inventors know, there is no known pavement mixture that exhibits excellent workability even at a low temperature lower than normal temperature and exhibits sufficient strength in a short time after construction.

Japanese Patent Application Laid-Open No. 2008-74919

The present invention has been made to improve the above-mentioned inconveniences of the prior art, and is excellent in workability even at room temperature or lower temperature, and pavement exhibiting excellent strength in a relatively short time after construction. It is an object of the present invention to provide a mixture for pavement and a pavement binder used for such a mixture for pavement.

Various binders are known that have the property of binding objects, but they have the property of binding aggregates used for pavement and have extremely high strength to withstand the traffic load of cars and trucks. As far as the applicant knows, little is known other than asphalt. Under these circumstances, the present inventors have made diligent research efforts to solve the above-mentioned problems, and in the process of making diligent research efforts, an aqueous solution of a polysaccharide exhibiting the property of forming a gel by contacting with a metal ion having a valence of two or more is obtained. Divalent or higher, which can be easily mixed with aggregate even at room temperature or lower, and has an action of gelling the polysaccharide in a mixture obtained by mixing an aqueous solution of the polysaccharide and the aggregate. It was found that when an aqueous solution containing the metal ions of the above was sprayed, the aggregates were quickly bonded to each other and a high-strength molded product was obtained. Surprisingly, they have found that the molded product exhibits strength equal to or higher than that obtained from a normal temperature asphalt mixture using cutback asphalt widely used in the field, and completed the present invention. ..

That is, the present invention is a pavement mixture containing an aggregate and a binder in one aspect, wherein the binder contains a polysaccharide that comes into contact with a divalent or higher metal ion to form a gel. The above problem is solved by providing a mixture for use. In a preferred embodiment, the polysaccharide is preferably contained in the binder in the form of an aqueous solution.

The present invention also provides, in another aspect, a pavement binder used in a pavement mixture, which comprises a polysaccharide that comes into contact with a divalent or higher metal ion to form a gel. By doing so, the above problem is solved. In a preferred embodiment, the polysaccharide is preferably contained in the pavement binder in the form of an aqueous solution.

According to the present invention, a pavement mixture that is excellent in workability even at room temperature or lower temperature and exhibits excellent strength in a relatively short time after construction, and further, a pavement binder used in such a pavement mixture. Is obtained.

It is a photograph of the specimen formed by using the pavement mixture which concerns on one aspect of this invention.

Hereinafter, the present invention will be described in more detail.

The pavement binder according to the present invention is a pavement binder used in a pavement mixture and is characterized by containing a polysaccharide that forms a gel in contact with a divalent or higher metal ion. It is a material.

The binder is a component for binding the aggregates constituting the pavement to solidify the pavement. A strong pavement can be obtained by adhering the aggregate by the action of the binder.

As described above, the paving binder according to the present invention contains a polysaccharide that forms a gel in contact with a divalent or higher metal ion, and in one preferred embodiment, the polysaccharide is in the form of an aqueous solution. Included in paving binders. Here, the aqueous solution of polysaccharide means a liquid in which the polysaccharide is dissolved in a solvent containing water as a main component, that is, a solution of the polysaccharide in which the main component of the solvent is water, and the binder is the polysaccharide. The inclusion in the form of an aqueous solution means that the binder contains an aqueous solution of polysaccharides. In the present specification, the main component of the solvent is water, which means that the solvent is more than 50vоl%, preferably 75vоl% or more, more preferably 90vоl% or more, still more preferably 95vоl% or more, still more preferably 100vоl%. Means that is water. The paving binder according to one aspect of the present invention, which uses an aqueous solution of a polysaccharide containing water as a main component of a solvent, has an advantage of being excellent in workability even at a low temperature because the increase in viscosity is small even when the temperature is lowered. ..

On the other hand, the polysaccharide is a substance having a structure in which a large number of monosaccharide molecules are polymerized, and the polysaccharide used for the pavement binder according to the present invention is a divalent or higher metal ion among such polysaccharides. It is a polysaccharide that forms a gel in contact with. A polysaccharide that forms a gel by contacting with a divalent or higher metal ion is a solution in which the aqueous solution containing the polysaccharide is in a liquid state (sol state) before contact with a divalent or higher metal ion. After contact with a divalent or higher metal ion, for example, a solution containing a divalent or higher metal ion is mixed with the aqueous solution, and the divalent or higher metal ion is brought into contact with a polysaccharide to form an insoluble gel. Means that. An aqueous solution of a polysaccharide having such properties is liquid before the addition of a divalent or higher metal ion that functions as a curing agent, so that it can be easily mixed with aggregates, while it has a divalent function that functions as a curing agent. By contacting with the above metal ions, they gel and bond the aggregates quickly and firmly. Therefore, if the pavement binder according to one aspect of the present invention containing such a polysaccharide, preferably in the form of an aqueous solution, is mixed with an aggregate to form a pavement mixture, it has a divalent or higher valence that functions as a hardening agent. By controlling the contact time with the metal ions, it is possible to control the curing start time of the pavement mixture, so that both excellent workability at low temperature and early strength development can be achieved at the same time.

The type of the polysaccharide that can be used in the paving binder according to the present invention is not particularly limited as long as it is a polysaccharide that forms a gel in contact with divalent or higher metal ions, but for example. Alginic acid, hypomethoxyated pectin (LM pectin), carboxymethyl cellulose (CMC), gellan gum, and derivatives thereof are preferably used, more preferably alginic acid and hypomethoxyated pectin (LM pectin), and more preferably. , Alginic acid can be used. These polysaccharides may be used alone or in combination of two or more. Needless to say, these polysaccharides may be used in the form of salts thereof, if necessary, and for example, monovalent cation salts of polysaccharides (sodium salt, potassium salt, ammonium salt, etc.) may be used. Since it is highly soluble in water, it can be suitably used for preparing an aqueous solution of a polysaccharide.

By the way, alginic acid is a natural polysaccharide that is abundantly contained in brown algae such as kelp and wakame seaweed and has a structure in which manulonic acid and gluronic acid are polymerized. An aqueous solution of alginic acid is a liquid at room temperature, but when it comes into contact with a divalent or higher metal ion, it forms an insoluble gel. That is, alginic acid is a polysaccharide that forms a gel when it comes into contact with a divalent or higher metal ion, and when alginic acid is used as the polysaccharide, a divalent or higher metal ion can be used as a curing agent. There are no particular restrictions on the types of divalent or higher metal ions that can be used as a curing agent for alginic acid, but for example, calcium ion (Ca ²⁺ ), magnesium ion (Mg ²⁺ ), barium ion (Ba ²⁺ ), aluminum ion. (Al ³⁺ ), strontium ion (Sr ³⁺ ), iron ion (Fe ³⁺ ) and the like are preferably used. These metal ions may be used alone or in combination of two or more.

Low-methoxyated pectin (LM pectin) is a polysaccharide mainly extracted from fruits such as lemon, orange, grapefruit, and apple, and has a structure in which galacturonic acid and its methyl ester, methylated galacturonic acid, are polymerized. It is a kind of pectin that has. The LM pectin is a pectin having a degree of esterification of 50% or less, in other words, a pectin in which methylated galacturonic acid accounts for less than 50% of the total galacturonic acid constituting the pectin. An aqueous solution of LM pectin is a liquid at room temperature, whereas when it comes into contact with a divalent or higher metal ion, it forms an insoluble gel. That is, LM pectin is a polysaccharide that forms a gel when it comes into contact with a divalent or higher metal ion, and when LM pectin is used as the polysaccharide, a divalent or higher metal ion can be used as a curing agent. .. There is no particular limitation on the types of divalent or higher metal ions that can be used as a curing agent for LM pectin, but for example, calcium ions (Ca ²⁺ ) and magnesium ions (Mg ²⁺ ) are preferably used. These metal ions may be used alone or in combination of two or more.

Gellan gum is a polysaccharide produced by microorganisms of the genus Pseudomonas and Sphingomonas, and has a structure based on the repeating structure of tetrasaccharides of D-glucose, D-glucuronic acid, D-glucose, and L-ramnorth. .. Like alginic acid and LM pectin, the aqueous solution of gellan gum is liquid at room temperature, whereas it forms an insoluble gel when it comes into contact with divalent or higher metal ions. That is, gellan gum is a polysaccharide that forms a gel when it comes into contact with a divalent or higher metal ion, and when gellan gum is used as the polysaccharide, a divalent or higher metal ion can be used as a curing agent. There is no particular limitation on the types of divalent or higher metal ions that can be used as a curing agent for gellan gum, but for example, calcium ions (Ca ²⁺ ) and magnesium ions (Mg ²⁺ ) are preferably used. These metal ions may be used alone or in combination of two or more.

Carboxymethyl cellulose (CMC) is a polysaccharide produced from cellulose as a raw material, and has a structure in which a part of the hydroxy group of glucopyranose constituting the cellulose skeleton is carboxymethylated. While the aqueous solution of carboxymethyl cellulose is liquid at room temperature, it forms an insoluble gel when it comes into contact with divalent or higher metal ions. That is, carboxymethyl cellulose is a polysaccharide that forms a gel when it comes into contact with a divalent or higher metal ion, and when carboxymethyl cellulose is used as the polysaccharide, a divalent or higher metal ion can be used as a curing agent. .. There is no particular limitation on the types of divalent or higher metal ions that can be used as a curing agent for carboxymethyl cellulose, but for example, calcium ions (Ca ²⁺ ) and aluminum ions (Al ³⁺ ) are preferably used. These metal ions may be used alone or in combination of two or more.

As described above, alginic acid, LM pectin, gellan gum, and carboxymethyl cellulose are all polysaccharides that form a gel in contact with divalent or higher metal ions. According to the findings found by the present inventors, when an aqueous solution containing these polysaccharides and an aggregate are mixed and brought into contact with a solution containing divalent or higher metal ions, the aggregates become strong. A pavement showing excellent strength is obtained.

In one preferred embodiment, the concentration of the polysaccharide in the aqueous solution of the polysaccharide contained in the binder is not particularly limited, but from the viewpoint of sufficiently covering the periphery of the aggregate and obtaining the desired adhesive strength. The aqueous solution of the polysaccharide preferably contains 0.1 to 20% by mass of the polysaccharide, more preferably 0.5 to 15% by mass of the polysaccharide, and 1 to 10% by mass. It is more preferable that it contains a polysaccharide. If the content of the polysaccharide in the aqueous solution is less than 0.1% by mass, it may be difficult to sufficiently cover the surface of the aggregate and exert sufficient binding force. On the other hand, if the content of the polysaccharide in the aqueous solution exceeds 20% by mass, the viscosity of the aqueous solution itself containing the polysaccharide is too high, which causes a disadvantage that it becomes difficult to mix with the aggregate. Similarly, from the viewpoint of sufficiently covering the periphery of the aggregate and obtaining a desired adhesive strength, it is preferable that the aqueous solution of such a polysaccharide has a viscosity at 20 ° C. of 300 to 120,000 cp. It is more preferably 750 to 90,000 cp, further preferably 1500 to 60,000 cp, even more preferably 3000 to 30,000 cp, but not limited to these. If the viscosity of the aqueous solution of the polysaccharide is too small, the adhesion to the aggregate is not good, while if the viscosity of the aqueous solution of the polysaccharide is too high, it becomes difficult to mix with the aggregate.

The pavement binder according to the present invention is necessary from the viewpoint of improving the adhesiveness with the aggregate, the plastic deformation resistance, the wear resistance, the bending property, etc. of the obtained pavement in a preferred embodiment. Depending on the situation, one or more modified components such as asphalt emulsion, modified asphalt emulsion, thermoplastic resin or rubber may be contained.

The type of thermoplastic resin that can be blended in the paving binder according to the present invention is not particularly limited, but for example, styrene / butadiene block copolymer (SBS), styrene / isoprene block copolymer (SIS), and the like. Ethylene resins such as styrene resin, ethylene / acrylic acid copolymer (EAA), ethylene vinyl acetate copolymer (EVA), ethylene / ethyl acrylate copolymer (EEA), polyester resin, nylon resin, acrylic Examples include based resins. One of these thermoplastic resins may be used alone, or two or more thereof may be used in combination. In addition, these thermoplastic resins may be blended in the pavement binder of the present invention in whole or in part as an emulsion.

On the other hand, there is no particular limitation on the types of rubber that can be blended in the paving binder of the present invention, and for example, natural rubber, backlash, cyclized rubber, styrene butadiene rubber, styrene isoprene rubber, polyisoprene rubber, butadiene rubber, etc. Examples thereof include chloroprene rubber, butyl rubber, halogenated butyl rubber, chlorine-based polyethylene, chlorosulfonated polyethylene, ethylene propylene rubber, EPT rubber, alfin rubber, styrene butadiene block polymer rubber, and styrene isoprene block polymer rubber. One of these rubbers may be used alone, or two or more of them may be used in combination. In addition, these rubbers may be blended in the pavement binder of the present invention in whole or in part as an emulsion.

<Pavement mixture>
The pavement mixture according to the present invention can be produced by mixing the pavement binder and the aggregate according to the present invention as described above. The pavement mixture is a mixture of an aggregate and a binder in a predetermined mixing ratio, and is a mixture used for construction of a surface layer or a base layer of pavement.

The aggregate contained in the pavement mixture according to the present invention mainly refers to sand, gravel, crushed sand, crushed stone and the like used for pavement, but the type of aggregate that can be used for the pavement mixture according to the present invention. There are no particular restrictions on the above, and an appropriate aggregate may be selected according to the pavement construction site and construction method. For example, regarding the grain size of the aggregate, if the thickness of the layer of the pavement to be constructed is relatively thin, an aggregate having a maximum grain size of No. 7 crushed stone (maximum grain size of 5 mm) may be used, while the other is When the thickness of the pavement to be constructed is relatively thick, an aggregate having a maximum particle size of No. 6 crushed stone (maximum particle size 13 mm) or No. 5 crushed stone (maximum particle size 20 mm) may be used. Further, the aggregate may contain a filler component in addition to sand, gravel, crushed sand, crushed stone and the like. Examples of such filler components include stone powder, clay, talc, fly ash, rubber powder, cork powder, wood powder, resin powder, inorganic fiber, pulp, synthetic fiber, carbon fiber and the like. ..

In the pavement mixture according to the present invention, the content of the polysaccharide that forms a gel in contact with divalent or higher metal ions is not particularly limited, but from the viewpoint of obtaining a pavement exhibiting excellent strength, the pavement is used. It is preferably 0.125 parts by mass or more, more preferably more than 0.125 parts by mass, and more preferably 0.20 parts by mass or more with respect to 100 parts by mass of the total mass of the aggregate contained in the mixture. It is even more preferably 0.25 parts by mass or more, and even more preferably 0.25 parts by mass or more. If the blending amount of the polysaccharide with respect to 100 parts by mass of the aggregate is less than 0.125 parts by mass, the aggregate may not be sufficiently covered with the polysaccharide and the adhesive strength of the aggregate may be lowered.

On the other hand, in a preferred embodiment, the content of the aqueous solution of the polysaccharide that forms a gel in contact with divalent or higher metal ions contained in the paving mixture according to the present invention is not particularly limited, but has excellent strength. From the viewpoint of obtaining the pavement showing the above, it is preferable that the total mass of the aggregate contained in the paving mixture is 2.5 parts by mass or more in terms of the amount of water contained in the aqueous solution. It is more preferably 5 parts by mass or more, and further preferably 4.5 parts by mass or more. In other words, when the pavement mixture according to the present invention contains the polysaccharide in the form of an aqueous solution, the content of water derived from the aqueous solution in the pavement mixture is 100 parts by mass of the total mass of the aggregate. On the other hand, it is preferably 2.5 parts by mass or more, more preferably 3.5 parts by mass or more, and further preferably 4.5 parts by mass or more. When the content of the aqueous solution is less than 2.5 parts by mass in terms of the amount of water contained in the aqueous solution, the aggregate is not sufficiently covered with the aqueous solution containing the polysaccharide, and the adhesive strength between the aggregates becomes low. There is a fear.

On the other hand, from the viewpoint of obtaining a pavement showing similarly excellent strength, the content of the aqueous solution is 20 parts by mass or less in terms of the amount of water contained in the aqueous solution with respect to 100 parts by mass of the aggregate contained in the pavement mixture. It is more preferably 15 parts by mass or less, further preferably 12 parts by mass or less, and further preferably 10 parts by mass or less. In other words, when the pavement mixture according to the present invention contains the polysaccharide in the form of an aqueous solution, the content of water derived from the aqueous solution in the pavement mixture is 100 parts by mass of the total mass of the aggregate. On the other hand, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, further preferably 12 parts by mass or less, and further preferably 10 parts by mass or less. Become. As shown in the experimental examples described later, according to the findings obtained by the present inventors, when the content of the aqueous solution in the pavement mixture becomes too large in terms of the amount of water contained in the aqueous solution, the obtained pavement is obtained. The strength tends to decrease. The reason is not completely clear, but if the content of the water derived from the aqueous solution contained in the pavement mixture is too large, the amount of water contained in the pavement mixture will increase accordingly, so that the pavement mixture will be used. Even if a curing agent containing divalent or higher metal ions is sprayed after the mixture is spread and leveled and compacted, the sprayed divalent or higher metal ions are difficult to penetrate into the pavement mixture, and the pavement is used. It is presumed that this is because the aggregate is not sufficiently adhered inside the mixture. That is, it is not preferable that the amount of water contained in the pavement mixture of the present invention is too large, and it is preferably 20 parts by mass or less and 15 parts by mass or less with respect to 100 parts by mass of the aggregate. It is more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less.

If necessary, an appropriate pigment may be added to the pavement mixture according to the present invention to color the mixture to a desired color tone. Examples of such pigments include titanium oxide, carbon black, zinc oxide, lead white, graphite, cadmium red, molybdenum orange, ferric hydroxide, iron oxide yellow, chrome yellow, chromium oxide, chrome green, and ultramarine. Examples include navy blue, cobalt blue, and manganese violet.

Further, a heat-shielding pigment or hollow particles can be added to the pavement mixture according to the present invention, if necessary. As the heat-shielding pigment, any heat-shielding pigment used for pavement can be used. For example, the solar reflectance is 10% or more, and the CIE1976L * a * b * color. Those having an L * value of 80 or less in space are preferably used. When the heat-shielding pigment is blended in the pavement mixture of the present invention, the constructed pavement body is effective in blocking radiant heat from the sun and the like, and particularly in suppressing the heat island phenomenon in summer. Further, as the hollow particles, for example, a ceramic balloon having a particle size of 10 to 125 μm, preferably a particle size of 25 to 80 μm, a glass balloon, a silas balloon, a balloon using a resin such as polystyrene can be used, and the present invention can be used. When these hollow particles are blended in the pavement mixture, there is an advantage that the heat-shielding effect of the formed pavement is improved due to its high heat insulating property, reflectivity, and irradiation property.

<How to build a pavement>
In order to construct a pavement body using the pavement mixture according to the present invention as described above, first, the road surface to be the construction site is thoroughly cleaned, and then the pavement mixture according to the present invention is manually or mechanically used. After spreading on the road surface and rolling, a predetermined amount of a curing agent, that is, a solution containing divalent or higher metal ions may be sprayed at an appropriate timing. By spraying a solution containing divalent or higher metal ions, the binder is cured and the pavement mixture layer is cured. Here, the layer thickness of the pavement mixture is not particularly limited, but when a fine aggregate is used as the aggregate, it is generally preferable to finish the layer thickness to 1 to 20 mm. It goes without saying that the layer thickness may be further increased, and in that case, a coarse aggregate having a large particle size can be used. The amount of the solution containing the curing agent is not particularly limited. For example, when using alginic acid as the polysaccharide and 10% by mass of the calcium chloride aqueous solution as the aqueous solution containing divalent or higher metal ions, it is used for paving. The amount is preferably 10 to 1000 g, more preferably 20 to 500 g, and even more preferably 50 to 200 g per 1 kg of the aggregate of the mixture.

The pavement mixture according to the present invention exhibits excellent strength immediately after spraying an aqueous solution containing divalent or higher metal ions as a curing agent, and is therefore particularly preferably used for repairing road surfaces that require early traffic opening. However, it can be widely used for road construction regardless of whether it is new or repaired. It should be noted that the pavement mixture according to the present invention is of course applicable to general roads, but is not limited to general roads, and is not limited to general roads, but is not limited to general roads. Of course, it can also be applied to pavements such as airfields, port facilities, open spaces attached to public halls, and sidewalks.

Hereinafter, the pavement binder and the pavement mixture according to the present invention will be described in more detail using experimental examples, but it goes without saying that the present invention is not limited to the following experimental examples.

<Experiment 1. Preparation of pavement mixture>
Sodium alginate (viscosity 200 cp or less, sold by Maikon Kohara Co., Ltd.) was dissolved in water at room temperature to prepare an alginic acid aqueous solution having an alginic acid concentration of 5% by mass. The obtained aqueous alginic acid solution showed an appropriate stickiness, was easily mixed with the aggregate, and had good adhesion to the aggregate. The viscosity of the alginic acid aqueous solution was measured using a B-type viscometer (product name "Digital Viscometer DV-3T", manufactured by AMETEK Brookfield) according to a conventional method, and the viscosity was 15,000 cp at 20 ° C. there were. Next, according to the blending amount shown in Table 1 below, No. 7 crushed stone (produced in Kasama City, Ibaraki Prefecture), fine sand (produced in Kasama City, Ibaraki Prefecture), and stone powder (calcium carbonate, sold by Ryoko Lime Industry Co., Ltd.) Mixed. To 100 parts by mass of the obtained mixture, 2.5 parts by mass, 5 parts by mass, 7.5 parts by mass, 10 parts by mass, and 12 parts of the previously prepared 5% by mass alginic acid aqueous solution were added according to the blending amounts shown in Table 1. Add 5 parts by mass, 15 parts by mass, or 20 parts by mass and mix well until the aggregate is sufficiently covered with the aqueous alginic acid solution to obtain a paving mixture (test samples 1 to 7) having different amounts of the aqueous alginic acid mixture. rice field. All of the above work was performed at room temperature (about 20 ° C.). In the following experiments, as a comparison target, a room temperature asphalt mixture using a conventionally widely used cutback asphalt as a binder (product name "Rescue Patch (registered trademark)", sold by Nichireki Co., Ltd.) (hereinafter, "Control sample 1") was used.

<Experiment 2. Marshall Stability Test-Part 1->
Specimens were prepared using the pavement mixture (test samples 1 to 7) obtained in Experiment 1, and the martial stability was measured. For the measurement of Marshall stability, the following is a partial modification of the Marshall stability test method described in "Pavement Survey / Test Method Handbook", 2019 edition, pp. 5-16 (Japan Road Association). I went like this.

According to a conventional method, a predetermined amount of test samples 1 to 7 were put into a mold and compacted a predetermined number of times by a martial hammer. Next, a 10% by mass calcium chloride aqueous solution was sprayed onto the molded products of the test samples 1 to 7 in the mold so as to have a spraying amount of 100 g per 1 kg of the aggregate. Test samples 1 to 7 were taken out from the mold, cured for 3 days, and then used as a specimen for martial stability measurement. An example of the specimen thus obtained is shown in FIG. All the above work was performed at room temperature (about 20 ° C.). Incidentally, the specimen of the control sample 1 was prepared in the same manner as the above procedure except that the procedure of spraying the calcium chloride aqueous solution after compaction was not performed.

The specimen obtained as described above was placed on the lower loading head of the pair of cylindrical loading heads with the side surface of the cylinder horizontal, and the specimen was placed on the loading device by covering it with the upper loading head. .. The specimen was sandwiched between the upper and lower loading heads, a load was applied in the radial direction of the specimen, and the maximum load (kN) measured until the load began to decrease was taken as the martial stability. The results obtained are shown in Table 2.

As shown in Table 2, 5 parts by mass, 7.5 parts by mass, 10 parts by mass, 12.5 parts by mass, 15 parts by mass, or 20 parts by mass of a 5 mass% asphalt aqueous solution is blended with respect to 100 parts by mass of aggregate. The Marshall stability of the specimens obtained from the pavement mixture (test samples 2 to 7) was 10.2 kN, 15.1 kN, 16.8 kN, 15.1 kN, 14.2 kN, or 11.9 kN, respectively. The marshall stability of control sample 1, which is a conventional normal temperature asphalt mixture using cutback asphalt, was significantly higher than that of 2.8 kN. On the other hand, the Marshall stability of the specimen obtained from the pavement mixture (test sample 1) containing 2.5 parts by mass of a 5% by mass arginic acid aqueous solution with respect to 100 parts by mass of the aggregate remained at 0.6 kN, which was a control. The Marshall stability of the specimen obtained from Sample 1 was significantly smaller than that of 2.8 kN. The above results show that the pavement contains 5 parts by mass or more of a 5 mass% asphalt aqueous solution with respect to 100 parts by mass of aggregate, in other words, 0.25 parts by mass (= 5 parts by mass x 0.05) or more of asphalt. It has been shown that the specimens obtained from the mixture for use exhibit superior strength over the specimens obtained from the conventionally used normal temperature asphalt mixture.

On the other hand, when the Marshall stability of the specimens obtained from the test samples 2 to 7 is compared, the test sample in which the blending amount of the 5% by mass alginic acid aqueous solution with respect to 100 parts by mass of the aggregate is 7.5 parts by mass or more and 15 parts by mass or less. The specimens obtained from 3 to 6 have a large martial stability of 14 kN or more, and among them, the blending amount of the 5% by mass alginic acid aqueous solution with respect to 100 parts by mass of the aggregate is 7.5 parts by mass or more and 12.5 parts by mass or less. The specimens obtained from the test samples 3 to 5 have an even higher martial stability of 15 kN or more, and in particular, the specimens obtained from the test sample 4 in which the blending amount of the 5% by mass alginic acid aqueous solution with respect to 100 parts by mass of the aggregate is 10 parts by mass. The specimen had the highest martial stability of 16.8 kN. That is, when the blending amount of the 5% by mass alginic acid aqueous solution with respect to 100 parts by mass of the aggregate is preferably 7.5 parts by mass or more and 15 parts by mass or less, more preferably 7.5 parts by mass or more and 12.5 parts by mass or less. , Shows that excellent Marshall stability can be obtained. When the blending amount of the 5% by mass alginic acid aqueous solution with respect to 100 parts by mass of the aggregate is 7.5 parts by mass or more and 15 parts by mass or less, the amount of alginic acid is 0.375 parts by mass (= 7.5 parts by mass × 0.05). The above is equivalent to 0.75 parts by mass (= 15 parts by mass × 0.05) or less, and 7.5 parts by mass or more and 12.5 parts by mass or less is 0.375 parts by mass (= 7.) in terms of the amount of alginic acid. It corresponds to 5 parts by mass × 0.05) or more and 0.625 parts by mass (= 12.5 parts by mass × 0.05) or less. Therefore, in other words, the above result shows that the amount of alginic acid blended with respect to 100 parts by mass of aggregate is preferably 0.375 parts by mass or more and 0.75 parts by mass or less, and more preferably 0.375 parts by mass or more and 0.625 parts by mass. It is shown that excellent Marshall stability can be obtained when the mass is less than or equal to a part.

The above results were surprising findings for the present inventors. Considering that alginic acid simply functions as a binder, as the amount of the aqueous alginic acid solution in the paving mixture increases, the amount of alginic acid that functions as a binder increases by that amount, so that the aggregate is adhered more firmly. Because it was thought. However, the results shown in Table 2 show that when the amount of alginic acid exceeds a certain amount, the strength of the pavement mixture after curing decreases conversely. Therefore, in order to investigate the cause of the above results, when observing the inside of the specimen obtained by using the test sample 7 after conducting the Marshall stability test, surprisingly, the blending amount of the arginic acid aqueous solution was observed. In the specimen obtained by using the test sample 7 having a large amount of water, it is clear that the aggregate is firmly adhered near the surface of the specimen, but the adhesion of the aggregate is relatively weak inside the specimen. became. The cause of the difference in adhesive strength depending on the location is that alginic acid contained in the binder rapidly comes into contact with the sprayed divalent or higher metal ions in the vicinity of the surface of the specimen and gels quickly. On the other hand, it is considered that the sprayed metal ions having a divalent value or more were difficult to penetrate into the inside of the specimen, and the gelation of alginic acid did not completely proceed. However, in the test piece obtained by using the test samples 3 to 5 in which the amount of the alginic acid aqueous solution is smaller, the sprayed divalent or higher metal ions permeate into the test piece, and the inside of the test piece is sufficient. Considering that the sample is hardened, it is considered that what prevents the metal ions having a divalent value or higher from sufficiently permeating into the inside of the test piece is the amount of water contained in the test piece in the first place. That is, when the amount of the alginic acid aqueous solution to be mixed with the aggregate contained in the pavement mixture is large, and as a result, the amount of water contained in the pavement mixture is too large, the sprayed divalent or higher metal ions are used as the specimen. It is presumed that the alginic acid did not sufficiently penetrate into the inside of the pavement, the gelation of alginic acid did not proceed sufficiently, and sufficient curing could not be obtained. Considering this sufficiently rational estimation and the fact that the specimen obtained by using the test sample 7 is larger than the control sample 1 and has a martial stability of more than 10 kN, it is used for paving. The amount of water contained in the mixture is preferably 19 parts by mass or less, which is the water content of the paving mixture of the test sample 7 with respect to 100 parts by mass of the aggregate, and is the water content of the paving mixture of the test sample 6. It is judged that 15 parts by mass or less including 14.25 parts by mass is more preferable.

<Experiment 3. Marshall Stability Test-Part 2->
Next, in order to obtain knowledge about the strength of the pavement constructed using the pavement mixture according to one aspect of the present invention immediately after construction, the same as in Experiment 2 except that the curing time was changed from 3 days to 30 minutes. A Marshall stability test was performed according to the procedure. The results are shown in Table 3.

As shown in Table 3, 5 parts by mass, 7.5 parts by mass, 10 parts by mass, 12.5 parts by mass, 15 parts by mass, or 20 parts by mass of a 5 mass% asphalt aqueous solution is blended with respect to 100 parts by mass of the aggregate. The Marshall stability of the specimens obtained from the pavement mixture (test samples 2 to 7) was already 9.0 kN, 13.0 kN, 7.4 kN, 4.6 kN, and 4. It has increased to 4 kN or 3.3 kN, which is clearly larger than the Marshall stability of 0.9 kN of the specimen obtained from the control sample 1 which is a conventional normal temperature asphalt mixture using cutback asphalt, and is a control sample. The Marshall stability of the specimen obtained from No. 1 after 3 days of curing was 2.8 kN (Table 2), which was also large. This result is the same as the case of curing for 3 days, 5 parts by mass or more of a 5 mass% asphalt aqueous solution with respect to 100 parts by mass of the aggregate, in other words, 0.25 parts by mass (= 5 parts by mass × 0.05). ) According to the specimen obtained from the pavement mixture containing the above alginic acid, it is shown that the desired strength is exhibited at a speed far higher than that of the specimen obtained from the conventional normal temperature asphalt mixture.

Further, the blending amount of the arginic acid aqueous solution increases with the martial stability of 13.0 of the specimen obtained from the test sample 3 in which 7.5 parts by mass of the 5 mass% arginic acid aqueous solution is blended with respect to 100 parts by mass of the aggregate. Considering that the Marshall stability gradually decreases, the amount of water contained in the paving mixture is contained in the paving mixture even when the curing period is relatively short, 30 minutes, for the same reason as described in the discussion in Experiment 2. It can be seen that there is a suitable value for. From the results in Table 3, the upper limit of the amount of water contained in the paving mixture is preferably 19 parts by mass or less, which is the water content of the paving mixture of the test sample 7, with respect to 100 parts by mass of the aggregate. More preferably, 15 parts by mass or less including 14.25 parts by mass of the water content of the pavement mixture of sample 6, and 12 parts by mass including 11.875 parts by mass of the water content of the pavement mixture of test sample 5. The following is more preferable, and it is judged that 10 parts by mass or less including 9.5 parts by mass of the water content of the paving mixture of the test sample 4 is further preferable. On the other hand, also from the results in Table 3, the lower limit of the water content in the paving mixture exceeds 2.375 parts by mass, which is the water content of the paving mixture of the test sample 1, with respect to 100 parts by mass of the aggregate2. It is preferably .5 parts by mass or more, more preferably 3.5 parts by mass or more, and further preferably 4.5 parts by mass including 4.75 parts by mass, which is the water content of the pavement mixture of the test sample 2. It is judged that it is preferable to have more than one part.

<Experiment 4. Examination of polysaccharides other than alginic acid>
LM pectin (product name "UNIPECTIN"), which is a polysaccharide generally used as a gelling agent instead of alginic acid as a binder and has the property of forming a gel by contacting with a metal ion having a divalent value or higher like alginic acid. ^TM OF 100C ”, sold by Unitech Foods Co., Ltd.), or a polysaccharide that is also commonly used as a gelling agent, but exhibits the property of forming a gel in a temperature-dependent manner in contrast to alginic acid and LM pectin. Test sample 8 and comparative sample 1 were prepared in the same manner as test sample 3 in Experiment 1 except that carrageenan (kappa type) (product name " ^SATIAGE LTM ME22", sold by Unitech Foods Co., Ltd.) was used. Using the obtained test sample 8 and comparative sample 1, 100 g per 1 kg of aggregate is used for the molded product of the test sample 8 to the comparative sample 1 in the mold in the same manner as in the procedure described in the experiment 2. A 10 mass% calcium chloride aqueous solution was sprayed using a mist to prepare a specimen, and the Marshall stability was evaluated. The results obtained are shown in Table 4. For comparison, Table 4 shows the martial stability of the specimen obtained by using the test sample 8 and the comparative sample 1, as well as the martial stability of the specimen obtained by using the control sample 1 from Table 2. Posted and shown.

As shown in Table 4, the Marshall stability of the specimen obtained from the test sample 8 using the aqueous solution of LM pectin as a binder was 3.8 kN after 3 days of curing, and cutback asphalt was used as a binder. It was clearly higher than the Marshall stability of 2.8 kN of the specimen obtained from the conventional normal temperature asphalt mixture. This result is as good as or better than the conventional room temperature asphalt mixture even when LM pectin, which is a polysaccharide having the property of contacting with a divalent or higher metal ion and gelling, is used as in alginic acid. It shows that the Marshall stability can be obtained.

On the other hand, the Marshall stability of the specimen obtained by using the comparative sample 1 using the aqueous solution of carrageenan as a binder was 0.0 kN, and its strength was extremely small. This result shows that when caraginan, which has the property of gelling due to temperature dependence, that is, when the temperature drops, is used as a binder, the mixture is prepared and the specimen is prepared at room temperature so as to be reproduced in this experiment. It is presumed that this is because the binder caraginan gelled before the aggregate and the binder were sufficiently mixed, and the aggregate was not sufficiently adhered.

<Experiment 5. Evaluation of workability-Part 1->
Next, in order to obtain knowledge on workability when the pavement mixture according to one aspect of the present invention was used, the following tests were conducted. First, as a mixture for paving, 1000 g of any of the test samples 2 to 4 prepared in Experiment 1 is placed in a cylindrical container having a diameter of 8.5 cm and a depth of 10.8 cm (product name "Tenkiri Can Small", respectively). It was placed in a Kondo Can Manufacturing Co., Ltd.) and cured at 20 ° C. Then, using a push-pull gauge (product name "RX-50", manufactured by Aiko Engineering Co., Ltd.), the needle was pierced by 2 to 3 cm at a speed of about 1 cm / 5 s perpendicularly to the pavement mixture in the container. The penetration resistance value (N) measured at that time was taken as the penetration degree. Here, a large degree of penetration means that a large force is required when piercing the needle into the pavement mixture, and a large force is required when handling the pavement mixture, that is, workability. Means bad. On the other hand, a small degree of penetration means that the force required to pierce the pavement mixture is small, and the force required to handle the pavement mixture is small, that is, the workability is good. Means. The values of the obtained penetration degree are shown in Table 5.

As shown in Table 5, in a temperature environment of 20 ° C., a pavement mixture containing 5 parts by mass, 7.5 parts by mass, or 10 parts by mass of a 5% by mass asphalt aqueous solution with respect to 100 parts by mass of aggregate (test sample). The penetration degree of 2 to 4) is 11.8N, 11.8N, or 10.8N, respectively, and the penetration degree of the control sample 1 which is a conventional normal temperature asphalt mixture using cutback asphalt as a binder is 29.4N. It was clearly smaller than that. The results show that the paving mixture using a polysaccharide that has the property of gelling in contact with divalent or higher metal ions such as alginic acid as a binder is extremely excellent in workability in a room temperature environment of about 20 ° C. It shows that it is.

<Experiment 6. Evaluation of workability-Part 2->
Next, in order to evaluate the workability of the paving mixture according to one aspect of the present invention at a lower temperature, the test samples 2 to 4 are the same as in Experiment 5 except that the curing temperature is changed from 20 ° C to 0 ° C. And the penetration degree of the control sample 1 was measured. The results are shown in Table 6.

As shown in Table 6, 0 ° C. of a pavement mixture (test samples 2 to 4) containing 5 parts by mass, 7.5 parts by mass, or 10 parts by mass of a 5% by mass alginic acid aqueous solution with respect to 100 parts by mass of aggregate. The degree of penetration in was 9.8N, 7.8N, or 9.8N, respectively, which was almost the same as the degree of penetration at 20 ° C. The results show that the paving mixture using a polysaccharide having the property of gelling in contact with divalent or higher metal ions such as alginic acid as a binder has excellent workability even in a low temperature environment of about 0 ° C. It shows that there is. On the other hand, the penetration degree of the conventional room temperature asphalt mixture using cutback asphalt as a binder was 83.3 N at 0 ° C., which was about three times higher than the penetration degree at 20 ° C. This result indicates that the conventional normal temperature asphalt mixture using cutback asphalt as a binder has a remarkable deterioration in workability in a low temperature environment of about 0 ° C.

As described above, if a pavement mixture using a polysaccharide having a property of contacting with a divalent or higher metal ion such as alginic acid and gelling as a binder can be easily applied at a temperature of about 20 ° C. However, it has excellent workability even in a low temperature environment as expected in winter or cold regions, for example.

According to the pavement binder or the pavement mixture according to the present invention, since the construction can be performed even in a low temperature environment of normal temperature or lower, there is an advantage that the construction is extremely easy in winter or cold regions. Further, according to the pavement binder or the pavement mixture according to the present invention, a pavement exhibiting excellent strength can be obtained in a relatively short time from the construction, so that the time from the construction to the opening of traffic can be shortened. Therefore, it can be said that the industrial applicability of the present invention is extremely high. Further, the pavement binder or pavement according to the present invention, which can construct a pavement exhibiting excellent strength by using a natural material, polysaccharide, as the main component of the binder, without requiring the use of petroleum resources. Mixtures are considered to contribute significantly to the construction of a sustainable society.

Claims

A paving mixture containing aggregates and binders
The binder is a pavement mixture comprising a polysaccharide that forms a gel in contact with a divalent or higher metal ion.
The pavement mixture according to claim 1, wherein the polysaccharide comprises one or more selected from alginic acid, hypomethoxyated pectin, gellan gum, carboxymethyl cellulose and derivatives thereof.
The pavement mixture according to claim 1 or 2, wherein the content of the polysaccharide with respect to 100 parts by mass of the aggregate is 0.125 parts by mass or more.
The pavement mixture according to any one of claims 1 to 3, wherein the polysaccharide is contained in the form of an aqueous solution.
The pavement mixture according to claim 4, wherein the content of the aqueous solution with respect to 100 parts by mass of the aggregate is 20 parts by mass or less in terms of the water content of the aqueous solution.
A pavement binder used in a pavement mixture, which is characterized by containing a polysaccharide that forms a gel in contact with a divalent or higher metal ion.
The pavement binder according to claim 6, wherein the polysaccharide comprises one or more selected from alginic acid, hypomethoxyated pectin, gellan gum, carboxymethyl cellulose, and derivatives thereof.
The pavement binder according to claim 6 or 7, wherein the polysaccharide is used so that the blending amount of the polysaccharide is 0.125 parts by mass or more with respect to 100 parts by mass of the aggregate.
The pavement binder according to any one of claims 6 to 8, wherein the polysaccharide is contained in the form of an aqueous solution.
The pavement bond according to any one of claims 6 to 9, wherein the aqueous solution is used so that the blending amount of the aqueous solution with respect to 100 parts by mass of the aggregate is 20 parts by mass or less in terms of the water content of the aqueous solution. Material.