Soil paving materials

Abstract

To provide a soil pavement material that excels in quick curability, resistance to frost damage, weeding capacity, and cracking resistance; becomes dense by natural carbonation; and has high strength and weeding effect.SOLUTION: A soil pavement material contains an admixture containing at least one non-hydraulic compound selected from the group consisting of γ-2CaO SiO2, 3CaO 2SiO2, α-CaO SiO2, and calcium magnesium silicate, calcium aluminate with a vitrification rate of 70% or more, a CaO / Al2O3 molar ratio of 1.0-2.7, and an impurity content of 15 mass% or less, a gypsum, and the soil. The non-hydraulic compound contains Li. In the non-hydraulic compound, the content of the Li is 0.001-1.0 mass% in terms of oxide.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to soil paving materials. [Background technology]

[0002] Soil pavement retains the elasticity and water retention of natural soil, and contributes to shock absorption, stabilization of road surface temperature, and weed prevention. Soil pavement is highly effective in preventing increases in road surface temperature, and has attracted attention as a measure against the heat island effect. In addition, because soil pavement blends easily with the surrounding natural environment, it is used in applications where the landscape is important, such as parks, promenades, river banks, rice field ridges, around railways and electrical facilities, roads, and around historical buildings, and also for applications where weed growth is suppressed.

[0003] Conventionally, known soil pavement materials include those in which quicklime-based, cement-based or magnesia-based solidifying agents are added to soil.

[0004] A paving composition has been proposed in which a certain amount of soil material is added to cement, mixed uniformly, and then water containing a specific inorganic hardening agent is added (see, for example, Patent Document 1). It has also been proposed to mix cement and a water-permeable soil hardening admixture containing calcium carbonate and silica powder as main components with sand and lay the mixture on a pavement base (see, for example, Patent Document 2). A natural soil paving composition has been proposed in which natural soil, cement, and a small amount of hardening agent are mixed with water, and the hardening agent contains magnesium chloride, aluminum chloride, calcium chloride, potassium chloride, or sodium chloride (see, for example, Patent Document 3).

[0005] Paving made with these cement-based or quicklime-based soil paving materials requires time for hardening, which means that early opening is not possible. In particular, paving does not harden at low temperatures, which means that it is susceptible to initial frost damage.

[0006] Also, there have been proposals to add magnesia-based solidifying agents to soil. These include soil improvement agents such as a soil pavement material containing magnesium oxide and different metal salts (see, for example, Patent Document 4), a pavement material in which magnesium oxide having an average periclase crystallite diameter of 330 to 430 Å is mixed with soil in advance (see, for example, Patent Document 5), and a water-permeable pavement composition mixture containing a magnesia-based solidifying agent, a polymer for admixture with cement, and water (see, for example, Patent Document 6). Paving using soil paving materials that use solidifying agents (hardening agents) containing magnesia has the problem that it takes a long time to harden and does not harden at low temperatures, making it susceptible to frost damage.

[0007] Also, an earth-based solidification material using calcium aluminate slag has been proposed (Patent Document 7). This calcium aluminate slag contains many impurities and has a low vitrification rate, so the CaO / Al2O3 molar ratio is increased to increase the reaction activity, but like cement-based, quicklime-based, and magnesia-containing solidification agents, it has problems such as a long hardening time, does not solidify at low temperatures, and is susceptible to frost damage. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 6-10305 [Patent Document 2] Japanese Patent Application Publication No. 6-306814 [Patent Document 3] Japanese Patent Application Publication No. 9-87621 [Patent Document 4] JP 2005-154735 A [Patent Document 5] JP 2014-51849 A [Patent Document 6] JP 2005-290679 A [Patent Document 7] Patent No. 5561921 [Patent Document 8] JP 2001-342461 A [Patent Document 9] JP 2018-96028 A Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, an object of the present invention is to provide a soil pavement material which has excellent rapid hardening properties, resistance to frost damage, weed prevention properties, and crack resistance, and which becomes dense through natural carbonation, has high strength, and has a weed prevention effect. [Means for solving the problem]

[0010] As a result of intensive research, the inventors have found that the above problems can be solved by adding an admixture containing a specific non-hydraulic material containing a specific amount of Li, which provides excellent rapid hardening, resistance to frost damage, weed prevention, and crack resistance, and also becomes dense through natural carbonation, thereby further improving strength and weed prevention effects. That is, the present invention is as follows. [1] A soil pavement material comprising an admixture containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate, calcium aluminate having a vitrification rate of 70% or more, a CaO / Al2O3 molar ratio of 1.0 to 2.7, and an impurity content of 15 mass% or less, gypsum, and soil, wherein the non-hydraulic compound contains Li, and the Li content in the non-hydraulic compound is 0.001 to 1.0 mass% in terms of oxide. [2] A soil paving material according to [1], which contains cement. [3] The soil pavement material according to [1] or [2], wherein the sulfur content in the non-hydraulic compound is 1.0 mass% or less in terms of oxide. [4] The soil pavement material according to [1] to [3], containing, as chemical components, per 100 parts by mass of the admixture, 0.001 to 1.0 part by mass of Li2O, 45 to 70 parts by mass of CaO, 29 to 55 parts by mass of SiO2, and 0 to 10 parts by mass of Al2O3. [5] The soil pavement material according to any one of [1] to [4], wherein the content of the non-hydraulic compound in the admixture is 65% or more. [6] The soil pavement material according to any one of [1] to [5], wherein the non-hydraulic compound is γ-2CaO·SiO2. Effect of the Invention

[0011] According to the present invention, it is possible to provide a soil pavement material which is excellent in rapid hardening properties, resistance to frost damage, weed prevention properties and crack resistance, and which becomes dense through natural carbonation, has high strength and weed prevention properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below. In the present invention, parts and percentages are based on mass unless otherwise specified.

[0013] The soil paving material of the present invention includes an admixture containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate, calcium aluminate having a vitrification rate of 70% or more, a CaO / Al2O3 molar ratio of 1.0 to 2.7, and an impurity content of 15 mass% or less, gypsum, and soil. The soil paving material of the present invention contains Li in the non-hydraulic compound, and the Li content is 0.001 to 1.0 mass% in terms of oxide.

[0014] The admixture contains one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate. The admixture is added to soil pavement materials to mainly contribute to weed prevention and crack resistance.

[0015] The admixture further contains Li in the non-hydraulic compound, and the Li content in the non-hydraulic compound is 0.001 to 1.0 mass% in terms of oxide. If the Li content in the non-hydraulic compound is less than 0.001 mass% or more than 1.0 mass%, it becomes difficult to obtain a denser hardened state by carbonation (salt), and it becomes difficult to obtain high strength and weed control effect. The Li content in the non-hydraulic compound is preferably 0.005 to 1.0 mass% in terms of oxide, more preferably 0.010 to 0.90 mass%, and even more preferably 0.015 to 0.80 mass%. It is presumed that when the Li content in the non-hydraulic compound is within the above range, the production of vaterite, which is a type of calcium carbonate, is promoted during the carbonation of CSH (calcium silicate hydrate), which is likely to lead to further strength enhancement and improved weed control effect. Here, "Li is contained in the non-hydraulic compound" refers to a state in which the non-hydraulic compound contains Li2O as a chemical composition (its presence can be confirmed by ICP emission spectroscopy), but Li2O is not identified by X-ray diffraction measurement (no clear peak for Li2O is seen), and it does not simply mean that the non-hydraulic compound and the Li compound are physically mixed. This state can be obtained by mixing the respective raw materials and subjecting them to heat treatment at a high temperature of 1,000°C or higher. Each component will be explained below. The Li content calculated as oxide can be measured by the method described in the Examples.

[0016] The non-hydraulic compound may be one type or two or more types. When the non-hydraulic compound is two or more types, the Li content in the non-hydraulic compound refers to the Li oxide content relative to the total of the two or more types of non-hydraulic compounds.

[0017] (γ-2CaO SiO2) γ-2CaO SiO2 is known as a low-temperature phase of the compound represented by 2CaO SiO2, and is completely different from the high-temperature phases α-2CaO SiO2, α'-2CaO SiO2, and β-2CaO SiO2. Although all of these are represented by 2CaO SiO2, they have different crystal structures and densities.

[0018] (3CaO 2SiO2) 3CaO·2SiO2 is a mineral called rankinite, which is a pseudowollastonite containing CaO. It is a chemically stable mineral with no hydration activity, but has a large effect of promoting carbonation.

[0019] (α-CaO SiO2) α-CaO·SiO2 (α-type wollastonite) is known as a high-temperature phase among the compounds expressed as CaO·SiO2, and is completely different from the low-temperature phase β-CaO·SiO2. Although both are expressed as CaO·SiO2, they have different crystal structures and densities.

[0020] Naturally occurring wollastonite is a low-temperature phase of β-CaO·SiO2. β-CaO·SiO2 has needle-shaped crystals and is used as an inorganic fibrous material such as wollastonite fiber, but it does not have the carbonation (salt) promoting effect of α-CaO·SiO2 according to this embodiment.

[0021] (Calcium Magnesium Silicate) Calcium magnesium silicate is a general term for CaO-MgO-SiO2 based compounds, but in this embodiment, merwinite represented by 3CaO·MgO·2SiO2 (C3MS2) is preferred, as merwinite can achieve a large carbonation (salt) promotion effect.

[0022] Of the non-hydraulic compounds listed above, γ-2CaO·SiO2 is particularly preferable because it requires less energy to grind than other compounds due to the powdering phenomenon known as dusting that occurs during production, it has a large effect of promoting carbonation over the long term, and when combined with blast-furnace slag cement at a low water-binder ratio, it has an extremely large effect of inhibiting carbonation.

[0023] The non-hydraulic compound according to the present embodiment is obtained by blending a CaO raw material, a SiO2 raw material, a MgO raw material, and a Li raw material in a predetermined molar ratio and heat treating the mixture. Examples of the CaO raw material include calcium carbonate such as limestone, calcium hydroxide such as slaked lime, by-product slaked lime such as acetylene by-product slaked lime, and fine powder generated from waste concrete mass. Examples of the SiO2 raw material include silica stone, clay, and various siliceous dusts generated as industrial by-products such as silica fume and fly ash. Examples of the MgO raw material include magnesium hydroxide, basic calcium carbonate, and dolomite. Examples of the Li raw material include lithium carbonate. Note that if the CaO raw material, the SiO2 raw material, and the MgO raw material contain Li, it is not necessary to add a new Li raw material. In order to reduce non-energy-derived CO2 emissions during heat treatment, one or more types of industrial by-products containing CaO can be used, such as by-product slaked lime, fine powder generated from waste concrete blocks, municipal waste incineration ash, and sewage sludge incineration ash. Among these, the use of by-product slaked lime, which contains fewer impurities than other industrial by-products, is more preferable.

[0024] Examples of by-product slaked lime include acetylene by-product slaked lime such as by-product slaked lime (wet type and dry type depending on the acetylene gas production method) produced in the acetylene gas production process by the calcium carbide method, and by-product slaked lime contained in the dust captured in the wet dust collection process of a calcium carbide electric furnace. By-product slaked lime contains, for example, 65 to 95% (preferably 70 to 90%) calcium hydroxide, 1 to 10% calcium carbonate, and 0.1 to 6.0% (preferably 0.1 to 3.0%) iron oxide. These ratios can be confirmed by fluorescent X-ray measurement and mass loss (Ca(OH)2: around 405°C to 515°C, CaCO3: around 650°C to 765°C) determined by differential thermogravimetry (TG-DTA). The volume average particle diameter measured by laser diffraction / scattering method is about 50 to 100 μm. Furthermore, the moisture content measured by the loss on drying method in JIS K 0068 "Method for measuring moisture content of chemical products" is preferably 10% or less. In addition, sulfur compounds such as CaS, A12S3, and CaC2·CaS may be contained, but the content is preferably 2% or less.

[0025] The heat treatment at a high temperature of 1,000° C. or higher is not particularly limited, but can be carried out, for example, by using a rotary kiln, an electric furnace, etc. The heat treatment temperature is not uniquely determined, but is usually carried out in the range of about 1,000 to 1,800° C., and often in the range of about 1,200 to 1,600° C.

[0026] In this embodiment, the above-mentioned industrial by-products containing non-hydraulic compounds can also be used. In this case, impurities coexist. Examples of such industrial by-products include steel slag.

[0027] The CaO raw material, SiO2 raw material, and MgO raw material may contain impurities, but this is not a problem as long as the effects of the present invention are not hindered. Specific examples of impurities include Al2O3, Fe2O3, TiO2, MnO, Na2O, K2O, S, P2O5, F, B2O3, and chlorine. Coexisting compounds include free calcium oxide, calcium hydroxide, calcium aluminate, calcium aluminosilicate, calcium ferrite, calcium aluminoferrite, calcium phosphate, calcium borate, magnesium silicate, leucite (K2O, Na2O)·Al2O3·SiO2, spinel MgO·Al2O3, magnetite Fe3O4, and sulfur compounds such as CaS, A12S3, and CaC2·CaS.

[0028] Of these impurities, the content of S (sulfur) in the non-hydraulic compound is preferably 1.0% or less, more preferably 0.7% or less, and even more preferably 0.5% or less, calculated as oxide (SO3). A content of 1.0% or less provides a sufficient carbonation (salt) promotion effect, and also allows the setting and hardening properties to be within an appropriate range. The content of S calculated as oxide (SO3) can be measured by fluorescent X-ray measurement. Note that S (sulfur) may be present in the non-hydraulic compound at about 2% calculated as oxide.

[0029] The content of non-hydraulic compounds in the admixture (the total content when multiple types are included) is preferably 65% ​​or more, more preferably 70% or more, and even more preferably 75% or more. Note that hydraulic 2CaO·SiO2 other than γ-2CaO·SiO2 can also be mixed in, up to a maximum of 35%.

[0030] The content of γ-2CaO·SiO2 in the admixture is preferably 35% or more, more preferably 45% or more. The upper limit of the content of γ-2CaO·SiO2 is not particularly limited. Among steelmaking slags, electric furnace reduction slag or stainless steel slag, which has a high content of γ-2CaO·SiO2, is preferable.

[0031] In addition, in order to make the admixture more effective, it is preferable that the admixture contains, as chemical components, 0.001 to 1.0 parts by mass of Li2O, 45 to 70 parts by mass of CaO, 29 to 55 parts by mass of SiO2, and 0 to 10 parts by mass of Al2O3 per 100 parts by mass of the admixture. The content of Li2O can be measured by the method described in the examples below. In addition, CaO, SiO2, and Al2O3 can be measured by fluorescent X-rays. As chemical components, it is more preferable that the admixture contains 0.002 to 0.5 parts by mass of Li2O, 60 to 70 parts by mass of CaO, 29 to 45 parts by mass of SiO2, and 0.5 to 5 parts by mass of Al2O3 per 100 parts by mass of the admixture. Furthermore, as chemical components, the total amount of Li2O, CaO, SiO2, and Al2O3 in 100 parts by mass of the admixture is preferably 90 parts by mass or more, and more preferably 95 to 100 parts by mass.

[0032] Methods for quantifying non-hydraulic compounds in admixtures include the Rietveld method using powder X-ray diffraction.

[0033] The Blaine specific surface area of ​​the admixture is not particularly limited, but is preferably 1,500 cm 2 / g or more is preferable, and the upper limit is 8,000 cm 2 / g or less. In particular, 2,000 to 6,000 cm 2 / g is more preferable, and 4,000 to 6,000 cm 2 / g is even more preferable. By having the Blaine specific surface area be equal to or greater than the lower limit, good material separation resistance is obtained, and the carbonation (salt) promotion effect is sufficient. Also, by having the Blaine specific surface area be equal to or less than the upper limit, the pulverization power required for pulverization is not large, which is economical, and weathering is suppressed, thereby preventing deterioration of quality over time.

[0034] The amount of the admixture used is preferably 1 to 300 parts by mass, more preferably 3 to 275 parts by mass, and even more preferably 5 to 250 parts by mass, per 100 parts by mass of the total of calcium aluminate and gypsum. By keeping the amount of the admixture used within the above range, the strength and weed control effect can be improved.

[0035] The calcium aluminate used in the present invention is a general term for a substance with hydration activity, mainly composed of CaO and Al2O3, which is obtained by mixing calcia raw materials and alumina raw materials, firing them in a kiln, or melting them in an electric furnace and cooling them, and either crystalline or amorphous can be used. It is a material with a fast hardening time and high initial strength development. In the calcium aluminate of the present invention, the molar ratio of CaO to Al2O3 (CaO / Al2O3 molar ratio) is preferably 1.0 to 2.7, more preferably 1.5 to 2.6, and even more preferably 2.0 to 2.5. By having the molar ratio within the above range, the curing time can be further shortened and the early strength development can be improved.

[0036] In the present invention, the content of impurities other than CaO and Al2O3 contained in calcium aluminate is preferably 15% by mass or less from the viewpoint of early strength development, and more preferably 10% by mass or less. If the impurity content exceeds 15% by mass, the curing time becomes long and the material may not harden at low temperatures. Representative impurities include silicon oxide, and other impurities include alkali metal oxides, alkaline earth metal oxides, titanium oxide, iron oxide, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, and alkaline earth metal sulfates.

[0037] From the viewpoint of reactivity, the vitrification rate of calcium aluminate is preferably 70% or more, and more preferably 90% or more. If the vitrification rate is less than 70%, the initial strength expression may decrease. The vitrification rate is measured by powder X-ray diffraction. For the sample before heating, the main peak area S of the crystalline mineral is measured, and then the sample is heated at 1,000°C for 2 hours and slowly cooled at a cooling rate of 1°C / min. For the sample after slow cooling, the main peak area S0 of the crystalline mineral is determined, and the vitrification rate χ is calculated by the following formula. Vitrification rate χ(%)=100×(1-S / S0)

[0038] The particle size of calcium aluminate is set to a Blaine specific surface area of ​​2,500 cm from the viewpoint of early strength development. 2 / g or more is preferable, and 5,000 cm 2 When the particle size of calcium aluminate is equal to or more than the above lower limit, the curing time is shortened and the early strength development is improved.

[0039] As the gypsum used in the present invention, hemihydrate gypsum and anhydrous gypsum can be used, and anhydrous gypsum is preferred in terms of strength development, and anhydrous gypsum produced as a by-product of hydrofluoric acid or natural anhydrous gypsum can be used. Gypsum is preferably weakly alkaline to acidic with a pH of 8 or less when immersed in water. If the pH is high, the solubility of the gypsum component increases, which may inhibit the initial strength development. The pH here is the pH at 20°C of a slurry with a mass ratio of gypsum to ion-exchanged water of 1 / 100, and is measured using an ion-exchange electrode or the like.

[0040] The particle size of the gypsum is set to 3,000 cm in terms of Blaine specific surface area from the viewpoint of early strength development and obtaining an appropriate working time. 2 / g or more is preferable, and 5,000 cm 2 / g or more is more preferable.

[0041] The amount of gypsum used is not particularly limited, but is preferably 50 to 250 parts by mass, more preferably 60 to 225 parts by mass, and even more preferably 70 to 200 parts by mass, relative to 100 parts by mass of calcium aluminate. When the amount of gypsum used is equal to or more than the lower limit, sufficient working time can be secured and strength development can be improved. When the amount of gypsum used is equal to or less than the upper limit, initial strength can be easily obtained.

[0042] The soil used in the present invention is not particularly limited and includes one or more of gravel, sand, gravel, and clay. Any of sandy soils such as mountain sand, river sand, and sea sand, silty soil, clay soil, surplus soil generated from construction work, lightweight aggregate, recycled aggregate, roadbed material, and soil from areas where weed control treatment is to be performed can be used as is. In general, natural soils such as Masago soil, Akadama soil, Kanuma soil, and dry sand are more preferable because they have stable quality.

[0043] In the soil paving material of the present invention, the amount of soil used is not particularly limited, but is preferably 100 to 3,000 parts by mass, more preferably 100 to 2,000 parts by mass, per 100 parts by mass of calcium aluminate and gypsum in total. When the amount of soil used is more than the above lower limit, the strength expression is high. On the other hand, when the amount of soil used is less than the above upper limit, the resistance to frost damage and thawing is excellent and it is economically preferable.

[0044] The soil paving material of the present invention can contain cement. By containing cement, strength development is increased. The cement used in the present invention is not particularly limited, and examples thereof include various Portland cements such as normal, early strength, super early strength, low heat, and moderate heat, various mixed cements obtained by mixing blast furnace slag, fly ash, or silica with these Portland cements, filler cements obtained by mixing limestone powder, gypsum, blast furnace slag powder, etc., and Portland cements such as environmentally friendly cements (ecocement) manufactured using municipal waste incineration ash and sewage sludge incineration ash as raw materials, as well as commercially available cement-based solidification materials and commercially available fine particle cements. It is also possible to use various cements and various mixed cements by pulverizing them into fine powder. It is also possible to increase or decrease the amount of components (e.g., gypsum) normally used in cements. These cements can be used alone or in combination of two or more kinds. Among them, ordinary cement is preferred in terms of distribution.

[0045] The amount of cement used is not particularly limited, but is preferably 50 to 1,000 parts by mass, more preferably 75 to 750 parts by mass, and even more preferably 100 to 500 parts by mass, relative to 100 parts by mass of the total of calcium aluminate and gypsum. By using an amount of cement within the above range, the composition has rapid hardening properties and high strength development.

[0046] The amount of water used is preferably 5 to 100 parts by mass, more preferably 10 to 95 parts by mass, and even more preferably 15 to 90 parts by mass, based on 100 parts by mass of the soil paving material of the present invention. When the amount of water used is equal to or more than the lower limit, mixing is good. Furthermore, when the amount of water used is equal to or less than the upper limit, sufficient strength is obtained.

[0047] In the present invention, a setting regulator can be used within a range that does not affect the effects of the present invention. The setting regulator is not particularly limited as long as it accelerates or retards the setting of calcium aluminate. Specifically, one or more of alkali hydroxides, alkali metal chloride salts, alkali metal carbonates, oxycarboxylic acids or their salts, phosphoric acids or their salts, dextrin, sucrose, polyacrylic acid or its salts, water reducing agents, and high performance water reducing agents can be used within a range that does not substantially impair the object of the present invention.

[0048] In the present invention, one or more of low pH solidifying agents such as magnesium oxide, bulking agents such as wood chips and rice husks, admixtures such as calcium hydroxide, calcium chloride and limestone fine powder, foaming agents, defoamers, thickeners, rust inhibitors, antifreeze agents, water reducing agents, fluidizing agents, polymers, hollow fine particles, anion exchangers such as hydrotalcite, colorants, and rubber chips can be used within a range that does not substantially impair the object of the present invention.

[0049] The construction method of the soil paving material of the present invention is not particularly limited as long as each soil paving material is mixed uniformly. There are a method of laying the soil paving material and covering it by sprinkling water with a watering can or a sprinkler, or a method of covering it with soil paving material that has been mixed with water in advance, and it is more preferable to cover it after mowing the grass and then spraying a herbicide. Furthermore, it is also possible to lay the soil paving material of the present invention excluding the soil on the ground and mix and mix it with the soil on the ground to cover it. For soil paving, it is preferable to pour the soil paving material onto the foundation ground at the construction site and spread it evenly using a rake, etc. In this case, it is preferable to surround the construction site with boundary blocks or wooden frames in advance to ensure effective rolling compaction and prevent the soil paving material from flowing out and spreading to the outside.

[0050] After laying the soil pavement material evenly as described above, it is advisable to firmly compact the edges of the construction area with a hand vibrator or similar device, and then thoroughly compact the entire surface with a plate roller or similar device.

[0051] The soil paving material according to the present invention is suitable for use in areas where the scenery is important, such as parks, promenades, river banks, field ridges, railways, areas around electrical facilities, roads, and around historical buildings. EXAMPLES

[0052] The present invention will now be described based on experimental examples.

[0053] [Experimental Example 1] A soil pavement material was obtained by preparing a mixture containing 100 parts by mass of gypsum, 1 part by mass of a setting regulator, and 1,000 parts by mass of soil per 100 parts by mass of calcium aluminate shown in Table 1, and the admixture was prepared in the amount shown in Table 1 per 100 parts by mass of calcium aluminate. In addition, for those containing cement, cement was mixed in the ratio shown in Table 1 with a total of 100 parts by mass of calcium aluminate and gypsum to prepare a soil pavement material. After laying the obtained soil pavement material in a formwork, 20 parts by mass of water was sprinkled per 100 parts by mass of the soil pavement material to construct the soil pavement material, and measurements of hardening time, initial frost damage resistance, and compressive strength were performed, as well as weed prevention and cracking tests. The results are shown in Table 1. The Blaine specific surface area of ​​calcium aluminate is 5,000 cm 2 / g. The vitrification rate of calcium aluminate, the molar ratio of CaO to Al2O3, and the impurity content were adjusted as shown in Table 1. The impurities were mainly silicon oxide.

[0054] <Materials used> Cement: Ordinary Portland cement, Blaine specific surface area 3,350 cm 2 / g Gypsum: Natural anhydrous gypsum, Blaine specific surface area 5,000 cm 2 / g Soil: Dried river sand from Niigata Prefecture, 1.2 mm sieve size -Setting agent: Anhydrous citric acid, manufactured by Iwata Chemical Industry Co., Ltd. Water: Tap water Sand: Standard sand made by the Cement Association Admixture A: Li-containing γ-2CaO SiO2. First-grade reagent calcium carbonate and first-grade reagent silicon dioxide were mixed in a molar ratio of 2:1, and then first-grade reagent lithium carbonate was added so that the Li content of the mixture was 0.0005-1.1% (internal substitution) calculated as oxide (Li2O). The mixture was then heat-treated at 1,400°C for 2 hours and allowed to stand at room temperature until the Blaine specific surface area reached 4,000 cm. 2 / g admixture A was prepared. The oxide-equivalent Li content of each admixture was measured using an ICP emission spectrometer (VISTA-PRO, Hitachi High-Tech Science Corporation). The Li content was confirmed to be the same as the amount of the additive, using an absolute calibration curve method in which SPEX XSTC-22 ICP mixture was diluted. The measurement conditions were as follows: ·Li measurement wavelength: 670.783nm BG correction: Fitting curve method Standard solution for calibration curve: Dilute SPEX XSTC-22 ICP mixture and use Calibration range: 0-5mg / L (0mg / L, 0.1mg / L, 0.5mg / L, 1mg / (5-point calibration curve of 5 mg / L, 5 mg / L) Quantitative analysis using absolute calibration curve method Admixture B: Li-containing α-CaO SiO2. First-grade reagent calcium carbonate and first-grade reagent silicon dioxide were mixed in a 1:1 molar ratio, and then first-grade reagent lithium carbonate was added so that the Li content of the mixture was 0.1% (internal substitution) in terms of oxide (Li2O). The mixture was then heat-treated at 1,500°C for 2 hours and allowed to stand at room temperature until the Blaine specific surface area reached 4,000 cm. 2 / g admixture B was prepared. Admixture C: β-2CaO SiO2. Reagent grade calcium carbonate and reagent grade silicon dioxide were mixed in a molar ratio of 2:1, heat-treated at 1,400°C for 2 hours, allowed to cool to room temperature, crushed, and the same heat treatment was repeated until the peak of γ-2CaO SiO2 was no longer observed by XRD. After the peak of only β-2CaO SiO2 was observed, the Blaine specific surface area was 4,000 cm 2 / g of admixture C was prepared.

[0055] As comparative examples, soil pavement materials were prepared using mortar containing no calcium aluminate (Test No. 1-20) and magnesia-based solidifying material (Test No. 1-21). The magnesia-based solidifying material used was commercially available magnesium oxide made by calcining magnesium produced in China. The mortar was prepared according to JIS R 5201 with a water-cement ratio of 50% and a sand-cement ratio of 3 / 1. Also, a soil paving material was prepared by adding 600 parts by mass of soil and 20 parts by mass of water to 100 parts by mass of magnesia-based solidifying material or mortar.

[0056] <Measurement method> Hardening time: The time it took for the mixed soil paving material to not become indented when pressed with a finger was measured. - Initial frost damage resistance: In accordance with the uniaxial compression test method for stabilized mixtures (Pavement Test Method Handbook, Japan Road Association) at 20°C and 60% relative humidity, the test specimens were cylindrical with a diameter of 100 mm and a height of 127 mm, packed in three layers, and each layer was pounded 25 times with a ram. After the test specimens were prepared, they were immediately cured in an environment of -10°C until they reached an age of 7 days. They were then cured in an environment of 20°C and 60% relative humidity until they reached an age of 28 days, after which their compressive strength was measured. The initial frost damage resistance was calculated as the percentage of remaining strength compared to the 28-day compressive strength of the test specimens that had been air-cured in an environment of 20°C and 60% relative humidity. Compressive strength: 4cm x 4cm x 16cm test specimens were prepared and naturally carbonated by air-dry curing. The compressive strength was measured after one year. Weed control test, crack test: 15cm of field soil was spread on a 30cm x 40cm tray, and a mixture of grass seeds (tall fescue, Kentucky bluegrass, and perennial ryegrass) was applied at 40g / m 2Then soil paving material was laid evenly on top of it to a thickness of 3 cm on the base surface, and 15 parts by mass of water was sprinkled for every 100 parts by mass of soil paving material. After one day of age, the material was placed in a constant temperature room at -10°C for one day, and then in a constant temperature room at 20°C for one day, repeating this cycle for 10 times, and then placed outdoors, and after 100 days, the number of grasses that had grown from the surface of the weed-control material and the number of cracks were measured.

[0057] [Table 1]

[0058] From Table 1, it can be seen that the soil paving material of the embodiment has excellent hardening characteristics, resistance to initial frost damage, high compressive strength due to natural carbonation, high crack resistance, and high weed prevention effect. [Industrial Applicability]

[0059] The soil paving material of the present invention is quick-hardening, allowing it to be opened early after construction, and allows for stable paving even in cold regions or low-temperature environments.Furthermore, it becomes dense through natural carbonation, and has improved weed-prevention effects and crack resistance, so it can be used widely in the fields of architecture and civil engineering.

Claims

1. γ-2CaO.SiO ２ , 3CaO・2SiO ２ , α-CaO.SiO ２ and calcium magnesium silicate, and an admixture containing one or more non-hydraulic compounds selected from the group consisting of a vitrification rate of 70% or more and a CaO / Al ２ O ３ A soil pavement material comprising calcium aluminate having a molar ratio of 1.0 to 2.7 and an impurity content of 15 mass% or less, gypsum, and soil, The non-hydraulic compound contains Li, and the Li content in the non-hydraulic compound is 0.001 to 1.0 mass % in terms of oxide.

2. 10. The soil paving material of claim 1, which contains cement.

3. 3. The soil paving material according to claim 1, wherein the content of sulfur in the non-hydraulic compound is 1.0 mass% or less in terms of oxide.

4. As a chemical component, Li in 100 parts by mass of the admixture ２ O 0.001 to 1.0 parts by mass, CaO 45 to 70 parts by mass, SiO ２ 29 to 55 parts by mass of Al ２ O ３ The soil paving material according to any one of claims 1 to 3, comprising 0 to 10 parts by mass.

5. The soil paving material according to any one of claims 1 to 4, wherein the content of the non-hydraulic compound in the admixture is 65% or more.

6. The non-hydraulic compound is γ-2CaO・SiO ２ The soil paving material according to any one of claims 1 to 5,

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