JP2023028442A - Soil pavement material - Google Patents

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

The present invention relates to soil paving materials.

Soil pavement retains the elasticity and water retention properties of natural soil, and contributes to shock absorption, road surface temperature stabilization, and weed control. Soil pavement is highly effective in suppressing the rise in road surface temperature, and is attracting attention as a countermeasure against the heat island phenomenon. In addition, since soil pavement is easy to harmonize with the surrounding natural environment, emphasis is placed on landscapes such as parks, promenades, river banks, ridges of fields, railways, around electrical facilities, roads, and around historical buildings. It is also used for applications and for suppressing the growth of weeds.

Conventionally, soil pavement materials are known in which quicklime-based, cement-based or magnesia-based solidifying agents are added to the soil.

A pavement composition has been proposed in which a certain amount of soil material is added to cement, mixed uniformly, and then added water containing a specific inorganic hardening agent is blended (see, for example, Patent Document 1). Further, it has been proposed to knead a water-permeable soil-hardening admixture mainly composed of cement, calcium carbonate and silica powder with masago soil and lay it on a pavement foundation (see, for example, Patent Document 2). A natural soil pavement composition has been proposed which contains magnesium chloride, aluminum chloride, calcium chloride, potassium chloride and sodium chloride as a hardening agent in the pavement composition which is water kneaded with natural soil, cement and a small amount of hardening agent. (See Patent Document 3, for example).

Pavement using these cement-based or quicklime-based soil pavement materials takes time to harden, so there is a problem that early opening is not possible, especially at low temperatures, it does not harden and suffers initial frost damage.

Also, it has been proposed to add a magnesia-based solidification agent to the soil. Soil paving materials containing magnesium oxide and dissimilar metal salts (see, for example, Patent Document 4), and paving materials in which magnesium oxide having an average periclase crystallite diameter of 330 to 430 Å and soil are premixed (for example, Patent Documents 5), and soil conditioners such as water-permeable pavement composition mixtures containing magnesia-based solidifying agents, cement-mixing polymers, and water (see, for example, Patent Document 6).
Pavement using a soil pavement material using such a solidifying agent (hardening agent) containing magnesia has the problem that it takes a long time to harden, does not harden at low temperatures, and suffers from frost damage.

A soil solidification material using calcium aluminate slag has also been proposed (Patent Document 7). Since this calcium aluminate-based slag has many impurities and a low vitrification rate, the CaO/Al ₂ O ₃ molar ratio is increased to increase the reaction activity, but it contains cement, quicklime, and magnesia. Like solidifying agents, it takes a long time to harden, does not harden at low temperatures, and suffers from frost damage.

JP-A-6-10305 JP-A-6-306814 JP-A-9-87621 JP 2005-154735 A JP 2014-51849 A JP-A-2005-290679 Japanese Patent No. 5561921 JP-A-2001-342461 JP-A-2018-96028

Accordingly, an object of the present invention is to provide a soil paving material that is excellent in quick-hardening property, resistance to frost damage, weed control, and crack resistance, becomes dense by natural carbonation, and has high strength and weed control effect. and

As a result of intensive research, the present inventors have found that by containing an admixture containing a specific non-hydraulic material containing a specific amount of Li, rapid hardening, resistance to frost damage, weed control, and resistance The present inventors have found that the above problems can be solved by improving crack resistance, becoming dense due to natural carbonation, and further improving the strength and weed control effect. That is, the present invention is as follows.
[1] an admixture containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO ₂ , 3CaO·2SiO ₂ , α-CaO·SiO ₂ and calcium magnesium silicate; and glass A soil pavement material containing calcium aluminate having a conversion ratio of 70% or more, a CaO/Al ₂ O ₃ molar ratio of 1.0 to 2.7, and an impurity content of 15% by mass or less, gypsum, and soil. A soil paving material, wherein the non-hydraulic compound contains Li, and the content of Li in the non-hydraulic compound is 0.001 to 1.0% by mass in terms of oxide.
[2] The soil paving material according to [1], containing cement.
[3] The soil paving material according to [1] or [2], wherein the sulfur content in the non-hydraulic compound is 1.0% by mass or less in terms of oxide.
[4] As chemical components, 0.001 to 1.0 parts by mass of Li ₂ O, 45 to 70 parts by mass of CaO, 29 to 55 parts by mass of SiO ₂ and Al ₂ O ₃ in 100 parts by mass of the admixture. The soil paving material according to [1] to [3], containing 0 to 10 parts by mass.
[5] The soil paving 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 paving material according to any one of [1] to [5], wherein the non-hydraulic compound is γ-2CaO·SiO ₂ .

ADVANTAGE OF THE INVENTION According to the present invention, it is possible to provide a soil paving material that is excellent in quick-hardening property, resistance to frost damage, weed control, and crack resistance, becomes dense by natural carbonation, and has high strength and weed control effect. .

The present invention will be described in detail below.
Parts and percentages used in the present invention are based on mass unless otherwise specified.

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

The admixture contains one or more non-hydraulic compounds selected from the group consisting of γ-2CaO.SiO ₂ , 3CaO.2SiO ₂ , α-CaO.SiO ₂ and calcium magnesium silicate. The admixture, when added to the soil paving material, mainly contributes to weed control and crack resistance.

The admixture further contains Li in the non-hydraulic compound, and the content of Li in the non-hydraulic compound is 0.001 to 1.0% by mass in terms of oxide. If the content of Li in the non-hydraulic compound is less than 0.001% by mass or more than 1.0% by mass, it becomes difficult to obtain a denser cured state by carbonation (salting), resulting in high strength and weed control. less effective.
The content of Li in the non-hydraulic compound is preferably 0.005 to 1.0% by mass in terms of oxide, more preferably 0.010 to 0.90% by mass, and 0.015 More preferably, it is up to 0.80% by mass. When the content of Li in the non-hydraulic compound is within the above range, the formation of vaterite, which is a type of calcium carbonate, is promoted in the carbonation of CSH (calcium silicate hydrate). It is estimated that it will be more likely to increase the strength and improve the weed control effect.
Here, "contains Li in the non-hydraulic compound" means that the non-hydraulic compound contains Li ₂ O as a chemical composition (existence can be confirmed by ICP emission spectrometry), but X-ray diffraction It refers to a state in which Li ₂ O is not identified by measurement (a clear peak of Li ₂ O is not observed), and simply refers to a state in which a non-hydraulic compound and a Li compound are not physically mixed. Such a state can be obtained by mixing each raw material and heat-treating it at a high temperature of 1,000° C. or more. Each component and the like will be described below.
The content of Li in terms of oxide can be measured by the method described in Examples.

1 type or 2 types or more may be sufficient as a non-hydraulic compound. When two or more non-hydraulic compounds are used, the content of Li in the non-hydraulic compound means the content of Li in terms of oxide with respect to the total of two or more non-hydraulic compounds.

(γ-2CaO-SiO ₂ )
γ-2CaO.SiO ₂ is a compound represented _by 2CaO.SiO ₂ and is known as a low temperature phase _. It is completely different from β-2CaO·SiO ₂ . All of these are represented by 2CaO.SiO ₂ , but have different crystal structures and densities.

( _3CaO.2SiO2 )
3CaO.2SiO ₂ is a mineral containing CaO in pseudowollastonite and is called rankinite. Although it is a chemically stable mineral with no hydration activity, it has a large effect of promoting carbonation (salting).

(α-CaO.SiO ₂ )
α-CaO·SiO ₂ (α-type wollastonite) is a compound represented by CaO·SiO ₂ and is known as a high-temperature phase. β-CaO·SiO ₂ is a low-temperature phase. They are completely different. All of these are represented by CaO.SiO ₂ , but have different crystal structures and densities.

Naturally occurring wollastonite is the low temperature phase β-CaO.SiO ₂ . β-CaO SiO ₂ has needle- _like crystals and is used as an inorganic fibrous material such as wollastonite fiber. There is no salinization promoting effect.

(calcium magnesium silicate)
Calcium magnesium silicate is a general term for CaO--MgO-- _SiO.sub.2 -based compounds, and in the present embodiment, it is Merwinite represented by _{3CaO.MgO.2SiO.sub.2} ( _{C.sub.3MS.sub.2} ) _. Mervinite achieves a large carbonation (salt) promoting effect.

Among the above non-hydraulic compounds, especially γ-2CaO SiO ₂ is accompanied by a pulverization phenomenon called dusting during production, so it requires less energy for pulverization than other compounds, and carbonation (salification) occurs over a long period of time. It is preferable in that it has a large acceleration effect and, on the other hand, has a very large neutralization suppressing effect when combined with blast-furnace cement at a low water binder ratio.

The non-hydraulic compound according to the present embodiment is obtained by blending CaO raw material, SiO ₂ raw material, MgO raw material and Li raw material in a predetermined molar ratio and heat-treating the mixture. CaO raw materials include, for example, calcium carbonate such as limestone, calcium hydroxide such as slaked lime, by-product slaked lime such as acetylene by-product slaked lime, fine powder generated from waste concrete mass, and the like. Examples of SiO ₂ raw materials include silica stone, clay, and various siliceous dusts generated as industrial by-products such as silica fume and fly ash. Examples of MgO raw materials include magnesium hydroxide, basic calcium carbonate, and dolomite. Moreover, lithium carbonate etc. can be mentioned as a Li raw material. If the CaO raw material, SiO ₂ raw material, or MgO raw material contains Li, it is not necessary to newly add the Li raw material. From the reduction of non-energy-derived CO ₂ emissions during heat treatment, one selected from industrial by-products containing CaO, such as by-product slaked lime, fine powder generated from waste concrete mass, municipal garbage incineration ash and sewage sludge incineration ash, or Two or more types can be used. Among them, it is more preferable to use by-product slaked lime, which contains less impurities than other industrial by-products.

As by-product slaked lime, by-product slaked lime produced in the acetylene gas production process by the calcium carbide method (there are wet and dry products depending on the acetylene gas production method), and the wet dust collection process of the calcium carbide electric furnace. Examples include acetylene by-product slaked lime such as by-product slaked lime contained in the dust captured by. The 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% iron oxide (preferably contains 0.1 to 3.0%). These ratios are determined by fluorescent X-ray measurement and differential thermogravimetric analysis (TG-DTA) for weight loss (Ca(OH) ₂ : around 405°C to 515°C, CaCO ₃ : around 650°C to 765°C). can be confirmed. The volume average particle diameter measured by laser diffraction/scattering method is about 50 to 100 μm. Furthermore, in JIS K 0068 "Method for measuring water content of chemical products", the moisture content measured by the loss-on-drying method is preferably 10% or less. Further, sulfur compounds such as CaS, Al ₂ S ₃ and CaC ₂ ·CaS may be contained, but the content is preferably 2% or less.

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

This embodiment can also use industrial by-products containing the non-hydraulic compounds previously described. In this case, impurities coexist. Such industrial by-products include steelmaking slag and the like.

The CaO raw material, the SiO ₂ raw material, and the MgO raw material may contain impurities, but they pose no particular problem as long as they do not impair the effects of the present invention. Specific examples of impurities include Al ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , MnO, Na ₂ O, K ₂ O, S, P ₂ O ₅ , F, B ₂ O ₃ and chlorine. be done. Coexisting compounds include free calcium oxide, calcium hydroxide, calcium aluminate, calcium aluminosilicate, calcium ferrite, calcium aluminoferrite, calcium phosphate, calcium borate, magnesium silicate, leucite (K ₂ O, Na ₂ O).Al ₂ O ₃ .SiO ₂ , spinel MgO.Al ₂ O ₃ , magnetite Fe ₃ O ₄ , and sulfur compounds such as CaS, Al ₂ S ₃ and CaC ₂ .CaS mentioned above.

Among these impurities, the content of S (sulfur) in the non-hydraulic compound is preferably 1.0% or less, more preferably 0.7% or less in terms of oxide (SO ₃ ). , and more preferably 0.5% or less. When the content is 1.0% or less, a sufficient effect of promoting carbonation (salting) can be obtained, and the setting and curing properties can be kept within an appropriate range. The content of S in terms of oxide (SO ₃ ) can be measured by fluorescent X-ray measurement. Note that S (sulfur) in the non-hydraulic compound may be present as long as it is about 2% in terms of oxide.

The content of the non-hydraulic compound in the admixture (the content of the total amount when multiple types are included) is preferably 65% or more, more preferably 70% or more, and 75% or more. is more preferred. Hydraulic 2CaO.SiO ₂ other than γ-2CaO.SiO ₂ can be mixed, and can be mixed up to a maximum of 35%.

The content of γ-2CaO·SiO ₂ in the admixture is preferably 35% or more, more preferably 45% or more. Also, the upper limit of the content of γ-2CaO·SiO ₂ is not particularly limited. Among steelmaking slags, electric furnace reduction slag or stainless steel slag having a high γ-2CaO·SiO ₂ content is preferred.

In addition, from the viewpoint of making the effect more likely to be expressed in the admixture, the chemical components are 0.001 to 1.0 parts by mass of Li ₂ O, 45 to 70 parts by mass of CaO, in 100 parts by mass of the admixture. It preferably contains 29 to 55 parts by weight of SiO ₂ and 0 to 10 parts by weight of Al ₂ O ₃ . The Li ₂ O content can be measured by the method described in Examples below. Also, CaO, SiO ₂ and Al ₂ O ₃ can be measured by fluorescent X-rays.
As chemical components, 0.002 to 0.5 parts by mass of Li ₂ O, 60 to 70 parts by mass of CaO, 29 to 45 parts by mass of SiO ₂ and 0.0 parts by mass of Al ₂ O ₃ are added to 100 parts by mass of the admixture. It is more preferable to contain 5 to 5 parts by mass.
Furthermore, as chemical components, the total of Li ₂ O, CaO, SiO ₂ and Al ₂ O ₃ in 100 parts by mass of the admixture is preferably 90 parts by mass or more, and is preferably 95 to 100 parts by mass. more preferred.

As a method for quantifying the non-hydraulic compound in the admixture, there is a Rietveld method using powder X-ray diffractometry.

Although the Blaine specific surface area of the admixture is not particularly limited, it is preferably 1,500 cm ² /g or more, and the upper limit is preferably 8,000 cm ² /g or less. Among them, 2,000 to 6,000 cm ² /g is more preferable, and 4,000 to 6,000 cm ² /g is even more preferable. When the Blaine specific surface area is at least the above lower limit, good material separation resistance is obtained, and the effect of promoting carbonation (salting) is sufficient. In addition, when the Blaine specific surface area is equal to or less than the above upper limit, the power required for pulverization is not increased, which is economical, and weathering is suppressed, so that deterioration of quality over time can be suppressed.

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 with respect to 100 parts by mass of calcium aluminate and gypsum in total. When the amount of the admixture used is within the above range, the strength and the weed control effect can be improved.

The calcium aluminate used in the present invention is mainly composed of CaO and Al ₂ O ₃ obtained by mixing a calcia raw material and an alumina raw material and firing it in a kiln, or melting it in an electric furnace and cooling it. It is a general term for substances having hydration activity, and both crystalline and amorphous can be used. It is a material that cures quickly and exhibits high initial strength.
In the calcium aluminate of the present invention, the molar ratio between CaO and Al ₂ O ₃ (CaO/Al ₂ O ₃ molar ratio) is preferably 1.0 to 2.7, more preferably 1.5 to 2.6. , 2.0 to 2.5 are more preferred. When the molar ratio is within the above range, the curing time can be further shortened and the initial strength development can be enhanced.

In the present invention, the content of impurities other than CaO and Al ₂ O ₃ contained in calcium aluminate is preferably 15% by mass or less, more preferably 10% by mass or less, from the viewpoint of early strength development. . If the content of impurities exceeds 15% by mass, the curing time becomes long, and the composition may not be cured at low temperatures. Typical impurities include silicon oxide, and also 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.

The vitrification rate of calcium aluminate is preferably 70% or more, more preferably 90% or more, in terms of reactivity. If the vitrification rate is less than 70%, the initial strength development property may deteriorate. A vitrification rate is measured by a powder X-ray diffraction method. The sample before heating is measured for the main peak area S of the crystalline mineral, then heated at 1,000° C. for 2 hours and then slowly cooled at a cooling rate of 1° C./min. For the sample after slow cooling, the main peak area _S0 of the crystal mineral is determined, and the vitrification rate χ is calculated by the following formula.
Vitrification rate χ (%) = 100 × (1-S/S ₀ )

The particle size of calcium aluminate is preferably 2,500 cm ² /g or more, more preferably 5,000 cm ² /g or more, from the viewpoint of early strength development. When the particle size of the calcium aluminate is at least the above lower limit, the hardening time is shortened and the initial strength development is improved.

As the gypsum used in the present invention, hemihydrate gypsum and anhydrite can be used. Anhydrous gypsum is preferable in terms of strength development, and hydrofluoric acid by-product anhydrite and natural anhydrite can be used. The gypsum is preferably weakly alkaline or acidic with a pH of 8 or less when immersed in water. When the pH is high, the solubility of the gypsum component increases, which may impede initial strength development. The pH referred to here is the pH at 20° C. of a slurry having a mass ratio of gypsum to ion-exchanged water of 1/100, and is measured using an ion-exchange electrode or the like.

The particle size of the gypsum is preferably 3,000 cm ² /g or more, more preferably 5,000 cm ² /g or more in terms of Blaine specific surface area, from the viewpoints of early strength development and proper working time.

The amount of gypsum used is not particularly limited, but it is preferably 50 to 250 parts by mass, more preferably 60 to 225 parts by mass, more preferably 70 to 250 parts by mass, based on 100 parts by mass of calcium aluminate. It is more preferably 200 parts by mass. When the amount of gypsum used is equal to or greater than the above lower limit, it is possible to take a sufficient working time and improve the strength development. Further, when the amount of gypsum used is equal to or less than the above upper limit, it becomes easier to obtain initial strength.

The soil used in the present invention contains one or more of gravel, sand, gravel and clay, and is not particularly limited. Sandy soil such as mountain sand, river sand, sea sand, silty soil, clay soil, surplus soil generated from construction, lightweight aggregate, recycled aggregate, roadbed material, and soil where weed control is applied as it is etc. can be used. In general, Masago soil, Akadama soil, Kanuma soil, and dry sand, which are natural soils, are stable in quality and are more preferable.

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, preferably 100 to 2,000 parts by mass with respect to 100 parts by mass of calcium aluminate and gypsum combined. 000 parts by mass is more preferable. When the amount of soil used is greater than the above lower limit, the strength development is enhanced. On the other hand, when the amount of soil used is less than the above upper limit, the freeze damage and thaw resistance is excellent, and it is economically preferable.

The soil paving material of the present invention can contain cement. Containing cement increases the strength development.
The cement used in the present invention is not particularly limited. or various mixed cements mixed with silica, filler cements mixed with limestone powder, gypsum, ground granulated blast furnace slow-cooled slag, etc.; Portland cement such as cement), commercially available cement-based solidifying materials, commercially available fine particle cement, and the like. Various cements and various mixed cements can be pulverized and used. Moreover, it is also possible to increase or decrease the amount of components (for example, gypsum, etc.) normally used in cement.
These cements can be used alone or in combination of two or more. Among them, ordinary cement is preferable in terms of distribution.

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, more preferably 100 to 500 parts by mass is more preferable. When the amount of cement used is within the above range, strength development is enhanced while having rapid hardening properties.

The amount of water used is preferably 5 to 100 parts by mass, more preferably 10 to 95 parts by mass, even more preferably 15 to 90 parts by mass, per 100 parts by mass of the soil paving material of the present invention. Mixing becomes favorable because the usage-amount of water is more than the said lower limit. Moreover, sufficient strength can be obtained because the amount of water used is equal to or less than the above upper limit.

In the present invention, it is possible to use a setting modifier within a range that does not affect the effects of the present invention. The setting modifier is not particularly limited as long as it accelerates or delays the setting of calcium aluminate. Specifically, alkali hydroxide, alkali metal chloride salt, alkali metal carbonate, oxycarboxylic acid or its salt, phosphoric acid or its salt, dextrin, sucrose, polyacrylic acid or its salt, water reducing agent, high performance One or more water reducing agents can be used as long as the object of the present invention is not substantially impaired.

In the present invention, a low pH solidifying material such as magnesium oxide, a bulking material such as wood chips and rice husks, an admixture such as calcium hydroxide, calcium chloride, and fine limestone powder, a foaming agent, an antifoaming agent, and a bulking agent. One or more of a viscosity agent, an antirust agent, an antifreeze agent, a water reducing agent, a fluidizing agent, a polymer, hollow fine particles, an anion exchanger such as hydrotalcite, a coloring agent, rubber chips, etc. It can be used as long as it does not interfere substantially.

In order to construct the soil pavement material according to the present invention, the construction method is not particularly limited as long as each soil pavement material is uniformly mixed. There is a method of spreading the soil pavement material and sprinkling it with a watering can or sprinkler, or a method of covering the soil pavement material that has been mixed with water in advance. is more preferable. Furthermore, it is also possible to coat the soil pavement material of the present invention by removing the soil, laying it on the ground, and mixing and stirring it with the soil on the ground.
In addition, in order to pave the soil, it is preferable to put the soil pavement material on the foundation ground of the construction site and spread it uniformly using a rake or the like. At this time, it is desirable to surround the construction site with boundary blocks, wooden frames, etc. in advance so that the rolling compaction can be effectively exerted to prevent the soil paving material from flowing out and spreading to the outside.

After uniformly laying the soil paving material as described above, firmly compact the perimeter of the construction site with a hand vibrator or the like, then use a plate roller or the like to fully compact the entire surface. is desirable.

Such a soil paving material according to the present invention is suitable for places where scenery is important, such as parks, promenades, river banks, ridges of fields, railways, around electrical facilities, roads, and around historical buildings. Applies to

Experimental examples of the present invention will be described below.

[Experimental example 1]
For 100 parts by mass of calcium aluminate shown in Table 1, 100 parts by mass of gypsum, 1 part by mass of setting modifier, 1,000 parts by mass of soil, and an admixture per 100 parts by mass of calcium aluminate A soil pavement material was obtained by preparing to contain the parts by mass shown in 1. In addition, for those containing cement, a soil pavement material was prepared by mixing cement at a ratio shown in Table 1 with a total of 100 parts by mass of calcium aluminate and gypsum. After laying the obtained soil pavement material in a formwork, 20 parts by mass of water is sprinkled with respect to 100 parts by mass of the soil pavement material to construct the soil pavement material, and the hardening time, initial frost damage resistance, and compressive strength are measured. In addition, a weed control test and a crack test were conducted. Table 1 shows the results.
The Blaine specific surface area of calcium aluminate was adjusted to 5,000 cm ² /g. Also, the vitrification ratio of calcium aluminate, the molar ratio of CaO to Al ₂ O ₃ and the content of impurities were adjusted as shown in Table 1. Impurities are mainly silicon oxide.

<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 ・Caking regulator: Anhydrous citric acid, manufactured by Iwata Chemical Industry Co., Ltd.
・Water: Tap water ・Sand: Standard sand manufactured by Japan Cement Association ・Admixture A: Li-containing γ-2CaO·SiO ₂ . First grade calcium carbonate and first grade silicon dioxide are mixed at a molar ratio of 2:1, and the content of Li in the mixture is 0.0005 to 1.1 in terms of oxide (Li ₂ O). % (internal substitution), heat-treated at 1,400° C. for 2 hours, allowed to stand to room temperature, and prepared an admixture A having a Blaine specific surface area of 4,000 cm ² /g. was made.
The oxide-equivalent Li content in each admixture was measured by an ICP emission spectrometer (VISTA-PRO, manufactured by Hitachi High-Tech Science). Then, from the absolute calibration curve method using a diluted SPEX company XSTC-22 ICP mixed solution, it was confirmed that the Li content was the same as the charged amount. In addition, the measurement conditions are as follows.
・ Li measurement wavelength: 670.783 nm
・ BG correction: fitting curve method ・ Standard solution for calibration curve: SPEX XSTC-22 ICP mixed solution diluted and used Calibration curve range: 0-5 mg / L (0 mg / L, 0.1 mg / L, 0. 5 mg/L, 1 mg/
L, 5 mg / L 5-point calibration curve)
· Quantitatively determined by the absolute calibration curve method · Admixture B: Li-containing α-CaO·SiO ₂ . Reagent grade 1 calcium carbonate and reagent grade 1 silicon dioxide are mixed at a molar ratio of 1:1, and the content of Li in the mixture is 0.1% in terms of oxide (Li ₂ O) (of which First-grade reagent lithium carbonate was mixed so as to have a split substitution), heat-treated at 1,500° C. for 2 hours, and left to stand at room temperature to prepare an admixture B having a Blaine specific surface area of 4,000 cm ² /g. .
Admixture C: β-2CaO.SiO ₂ . Reagent grade 1 calcium carbonate and reagent grade 1 silicon dioxide are mixed at a molar ratio of 2:1, heat-treated at 1,400° C. for 2 hours, allowed to stand at room temperature, pulverized and analyzed by XRD to obtain γ-2CaO SiO. The same heat treatment was repeated until the peak of ₂ was no longer confirmed. After confirming the peak of only β-2CaO·SiO ₂ , an admixture C having a Blaine specific surface area of 4,000 cm ² /g was prepared.

As comparative examples, soil paving materials were prepared using mortar containing no calcium aluminate (Experiment No. 1-20) and magnesia-based solidifying material (Experiment No. 1-21).
As the magnesia-based solidifying material, commercially available magnesium oxide obtained by sintering magnesium produced in China was used.
A mortar according to JIS R 5201 was prepared with a water-cement ratio of 50% and a sand/cement ratio of 3/1.
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.

<Measurement method>
- Hardening time: The time was measured before the kneaded soil pavement material was dented even when pressed with a finger.
・ Initial frost damage resistance: In an environment of 20 ° C and 60% relative humidity, the specimen size is 100 mm in diameter and 127 mm in height in accordance with the uniaxial compression test method for the stabilized mixture (Pavement Test Method Handbook, Japan Road Association). The specimen was packed in three layers, and each layer was punched 25 times with a ram. Immediately after the preparation of the specimen, it was cured in an environment of -10°C until the age of 7 days. Then, the compressive strength was measured after air-drying and curing in an environment of 20° C. and 60% relative humidity until the material age was 28 days. The initial frost damage resistance was defined as the ratio of remaining strength to the 28-day compressive strength of a specimen air-dried under an environment of 20°C and 60% relative humidity.
- Compressive strength: A test piece of 4 cm x 4 cm x 16 cm was prepared and naturally carbonized by air-drying. The compressive strength at the material age of 1 year was measured.
Weed control test, cracking test: Spread 15 cm of soil from a field on a 30 cm x 40 cm tray, sprinkle 40 g / m ² of a mixture of tall fescue, Kentucky bluegrass, and perennial ryegrass, which are seeds of lawn, and soil on top. After laying the pavement material uniformly on the base surface to a thickness of 3 cm, 15 parts by mass of water was sprinkled with respect to 100 parts by mass of the soil pavement material. After 1 day of material age, place in a constant temperature room at -10 ° C for 1 day, then place in a constant temperature room at 20 ° C for 1 day, repeat this 10 cycles, place outdoors, and grow from the surface of the weed control material after 100 days. The number of turf and the number of cracks were measured.

From Table 1, it can be seen that the soil paving materials of Examples have excellent hardening properties, initial frost damage resistance, high compressive strength due to natural carbonation, high crack resistance, and high weed control.

The soil paving material of the present invention is quick-hardening, so it can be opened early after construction, stable pavement can be made even in cold regions and low-temperature environments, and it becomes dense due to natural carbonation, and the weed control effect and crack resistance are improved. Therefore, it is widely used in the construction and civil engineering fields.

Claims (6)

An admixture containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO ₂ , 3CaO·2SiO ₂ , α-CaO·SiO ₂ , and calcium magnesium silicate; A soil paving material containing calcium aluminate having a CaO/Al ₂ O ₃ molar ratio of 70% or more, a CaO/Al 2 O 3 molar ratio of 1.0 to 2.7, and an impurity content of 15% by mass or less, gypsum, and soil, ,
A soil paving material containing Li in the non-hydraulic compound, wherein the content of Li in the non-hydraulic compound is 0.001 to 1.0% by mass in terms of oxide. 2. A soil paving material according to claim 1, containing cement. The soil paving material according to claim 1 or 2, wherein the sulfur content in said non-hydraulic compound is 1.0% by mass or less in terms of oxide. As chemical components, in 100 parts by mass of the admixture, 0.001 to 1.0 parts by mass of Li ₂ O, 45 to 70 parts by mass of CaO, 29 to 55 parts by mass of SiO ₂ , and 0 to 0 parts by mass of Al ₂ O ₃ The soil paving material according to any one of claims 1 to 3, containing 10 parts by mass. The soil paving material according to any one of claims 1 to 4, wherein the content of said non-hydraulic compound in said admixture is 65% or more. The soil paving material according to any one of claims 1 to 5, wherein the non-hydraulic compound is γ-2CaO·SiO ₂ .