JP6634267B2 - Soil pavement material - Google Patents

Description

  The present invention relates to a soil pavement material.

   Soil pavement is a pavement that retains the elasticity and water retention of natural soil and contributes to absorbing impact and stabilizing the road surface temperature. In particular, the effect of suppressing the rise in road surface temperature is high, and it is receiving attention as a measure against the heat island phenomenon. In addition, because it is easy to harmonize with the surrounding natural environment, it is also used in applications where landscape is important, such as around parks, promenades, and historic buildings.

  Conventionally, as a soil pavement material, a material obtained by adding a quicklime-based, cement-based, or magnesia-based solidifying agent to soil is known.

  A pavement composition is described in which a certain amount of a soil material is added to cement, mixed uniformly, and then added with water containing a specific inorganic hardener (Patent Document 1). Moreover, it is described that cement and, if necessary, a water-permeable soil hardening admixture containing calcium carbonate and silica stone powder as main components are kneaded and laid on a pavement foundation (Patent Document 2). In a pavement composition in which natural soil, cement and a small amount of a hardener are water-mixed, a natural soil pavement composition using magnesium chloride, aluminum chloride, calcium chloride, potassium chloride, and sodium chloride as the hardener is described. (Patent Document 3).

  The pavement using the cement-based or quick-lime-based soil pavement material has a problem in that the pavement has high rigidity and high elasticity. In addition, there is a problem that it cannot be opened early because curing takes time. Further, the pH becomes a strong alkali of 12 or more, and there is a problem on the influence on surrounding vegetation and elution of hexavalent chromium.

  Further, there has been proposed one in which a magnesia-based solidifying agent is added to soil. A soil pavement material containing magnesium oxide and a different metal salt (Patent Document 4), a pavement material in which magnesium oxide having an average periclase crystallite diameter of 330 to 430 ° and soil are mixed in advance (Patent Document 5), There is a soil improving agent such as a water-permeable pavement composition mixture containing a magnesia-based solidifying agent, an emulsifying resin and water (Patent Document 6).

  In the case of pavement using a soil pavement material using a solidifying agent (hardening agent) containing magnesia, there has been a problem that the hardening time is long, the material does not solidify at low temperatures, and suffers from frost damage.

Further, an earth-based solidifying material using calcium aluminate-based slag has been proposed (Patent Document 7). When a calcium aluminate slag is used, the reaction activity is increased by increasing the CaO / Al ₂ O ₃ molar ratio because of a large amount of impurities and a low vitrification ratio. However, it contains cement, quick lime, and magnesia. As with the solidifying agent, there is a problem that the curing time is long, the solidification does not take place at low temperatures, and frost damage occurs.

JP-A-6-10305 Patent No. 2533452 JP-A-9-87621 JP 2005-154735 A JP 2014-51849 A Japanese Patent No. 4310782 Patent No. 5561921

In conventional soil pavement materials, when a cement-based solidifying agent (hardening agent) is used, there is a problem in pavement with high rigidity and high elasticity. When using a magnesia-based solidifying agent or calcium aluminate-based slag, Has a problem that the curing time is long, the material does not solidify at low temperature, and suffers from frost damage.
The present invention solves the above problems, and provides a soil pavement material that is fast-hardening, has excellent resistance to frost damage, and has good shock absorption.

That is, the present invention provides (1) the vitrification ratio of 70%, CaO / _Al 2 _{O 3} molar ratio of 1.0 to 2.7, impurities 15% or less, with a Blaine specific surface area of 3000 cm ² / g or more A soil pavement material containing a certain calcium aluminate and soil, (2) a soil pavement material of (1) further containing gypsum, (3) a calcium silicate, a polymer for cement admixture, and an asphalt emulsion The soil pavement material according to (1) or (2), comprising one or more selected ones.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to set it as the soil pavement material which is quick-hardening, is excellent in resistance to frost damage, and has good shock absorption.

Hereinafter, the present invention will be described in detail.
The parts and percentages used in the present invention are based on mass.

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 baking in a kiln or melting and cooling in an electric furnace. It is a general term for substances having hydration activity, and is a material that has a fast curing time and high initial strength.
Examples of the calcium aluminate of the present invention include, for example, an amorphous calcium aluminate which is hardened in a shorter time than alumina cement and then rapidly quenched after melting a mixture of a calcia raw material and an alumina raw material from the viewpoint of high initial strength development. The calcium aluminate of the present invention in which the molar ratio of CaO to Al ₂ O ₃ (CaO / Al ₂ O ₃ molar ratio) is preferably 1.0 to 2.7, and 2.0 to 2.5. More preferred. If it is less than 1.0, it takes time to cure, and if it exceeds 2.7, the curing may be too early.

Components (impurities) other than CaO and Al ₂ O ₃ which are the components of the calcium aluminate of the present invention are preferably 15% or less from the viewpoint of initial strength development, and more preferably 10% or less. If it exceeds 15%, there is a problem that the curing time is long and it does not solidify at low temperatures.
Representative examples of the impurities contained in the calcium aluminate of the present invention include silicon oxide, and other metals such as alkali metal oxides, alkaline earth metal oxides, titanium oxide, iron oxide, alkali metal halides, and alkaline earth metal halides. , Alkali metal sulfates, alkaline earth metal sulfates, etc., which are obtained by partially replacing CaO or Al ₂ O ₃ , but are not particularly limited.
The vitrification rate of the calcium aluminate of the present invention is preferably 70% or more, more preferably 90% or more, in terms of reaction activity. If it is 70% or less, the initial strength expression may decrease.

The measurement of the vitrification rate of calcium aluminate is performed by previously measuring the main peak area S of the crystalline mineral by a powder X-ray diffraction method for the sample before heating, and then heating at 1000 ° C. for 2 hours and then 1 to 10 ° C./min. Slowly cooling at a cooling rate, the main peak area S ₀ of the heated crystalline mineral is determined by powder X-ray diffraction method, and the vitrification rate 算出 is calculated using the values of S ₀ and S by the following equation.
Vitrification rate χ (%) = 100 × (1-S / S ₀ )

The particle size of the calcium aluminate of the present invention, in terms of initial strength development is preferably more than Blaine specific surface area ^{3000cm 2 / g, 5000cm 2 /} g or more is more preferable. If it is less than 3000 cm ² / g, the initial strength development may be reduced.

Examples of the gypsum of the present invention include hemihydrate gypsum and anhydrous gypsum. In terms of strength, anhydrous gypsum is preferable, and anhydrous gypsum by-product hydrofluoric acid and natural anhydrous gypsum can be used. The pH when gypsum is immersed in water is preferably a weak alkali having a pH of 8 or less to an acidic one. When the pH is high, the solubility of the gypsum component becomes high, which may hinder the initial strength development. The pH referred to here is a value obtained by measuring the pH of a diluted slurry of gypsum / ion-exchanged water = 1 g / 100 g at 20 ° C. using an ion-exchange electrode or the like.

The particle size of the gypsum of the present invention is preferably 3000 cm ² / g or more in Blaine specific surface area value, from the viewpoint of the 5000 cm ² / g or higher initial strength development, the proper work time is obtained.
The amount of gypsum used in the present invention is preferably 50 to 150 parts based on 100 parts of calcium aluminate. If the amount is less than 50 parts, the working time cannot be obtained, and the strength developability may decrease. If it exceeds 150 parts, the working time can be sufficiently taken, but the initial strength may not be obtained.

In the present invention, calcium silicate can be used for the purpose of increasing the strength.
Calcium silicate includes 3CaO · SiO ₂ and 2CaO · SiO ₂ , and is not particularly limited. However, γ-2CaO · SiO ₂ absorbs carbon dioxide in the atmosphere to increase the strength, and is most preferable.
γ-2CaO · SiO ₂ is different among the compounds represented by 2CaO · SiO _2, is what is known as low-temperature phase, the α-2CaO · SiO ₂ and β-2CaO · SiO ₂ is a high temperature phase Things. Each of these compounds has the same chemical composition of 2CaO · SiO ₂ but different crystal structures. 2CaO.SiO ₂ present in the cement clinker is β-2CaO.SiO ₂ . It has been found that β-2CaO.SiO ₂ has hydraulic properties, whereas γ-2CaO.SiO ₂ in the present invention does not have hydraulic properties, but has a property of absorbing carbon dioxide in the atmosphere and hardening.
The particle size of the γ-2CaO · SiO ₂ is not particularly limited but is preferably 3000 cm ² / g or more in Blaine specific surface area value, 4,000~8,000cm ² / g is more preferable. If the Blaine specific surface area is less than 3,000 cm ² / g, sufficient strength may not be obtained due to absorption of carbon dioxide in the atmosphere. Even if it exceeds 8,000 cm ² / g, further enhancement of the effect cannot be expected.

In the present invention, a polymer for cement admixture can be used for the purpose of imparting viscoelasticity and producing a shock such as vibration.
The polymer for cement admixture of the present invention is, for example, a polymer for cement admixture specified in JIS A 6203, and is used for polymer dip dispersion in which polymer fine particles are dispersed in water, rubber latex and resin emulsion. It refers to a re-emulsifiable powder resin obtained by drying a material to which a stabilizer or the like has been added.
For example, acrylonitrile butadiene rubber, styrene butadiene rubber, chloroprene rubber, rubber latex such as natural rubber, ethylene vinyl acetate copolymer, polyacrylate, vinyl acetate vinyl versatate copolymer, and styrene acrylic Acid ester copolymers and acrylate-based copolymers represented by acrylonitrile / acrylate, epoxy resins, liquid polymers represented by unsaturated polyester resins, and the like, and one or more of these may be used. Mixtures can be used. These can be used in liquid or powder form, and are not particularly limited.

Further, in the present invention, an asphalt emulsion can be used for the purpose of imparting viscoelasticity and causing a shock such as vibration.
The asphalt emulsion of the present invention is a colloid liquid obtained by dispersing asphalt fine particles mainly composed of bitumen obtained naturally or obtained as a distillation residue of petroleum in water, bitumen, for example, The main material is a straight asphalt having a penetration of about 40/60 to 200/500, to which a surfactant and a polyvalent metal salt are added, and further, if necessary, an emulsifier, a dispersant, and a protective colloid. Is appropriately emulsified in water.
Further, it is also possible to use a modified bituminous substance obtained by adding and mixing a rubber, a synthetic high molecular polymer or the like to the bituminous substance and emulsifying the modified bituminous substance.
The bitumen content in the asphalt emulsion is preferably from 40 to 70%, more preferably from 55 to 65%. If it is less than 40%, the effect of imparting viscoelasticity to the soil pavement material may not be obtained, and if it exceeds 70%, the expression of strength may be reduced. These can be used in liquid form or in bulk form, and are not particularly limited.

The calcium aluminate used in the present invention, or calcium aluminate and gypsum, may contain one or more of calcium silicate, a polymer for cement admixture, and asphalt emulsion for the purpose of enhancing strength and improving viscoelasticity. it can.
The mixing ratio of the calcium silicate, the polymer for cement admixture, and the asphalt emulsion is preferably 10 to 70 parts, more preferably 20 to 50 parts, per 100 parts of calcium aluminate or calcium aluminate and gypsum. Calcium silicate, cement admixture polymer and asphalt emulsion tend to have low long-term strength when the content is small, and when the content exceeds 70 parts, the initial strength developability tends to decrease, but the mixing ratio of these is particularly limited. is not.
The method of mixing the cement admixture polymer or the asphalt emulsion can be pre-mixed when kneading the calcium aluminate and water before curing, and it is also possible to spray a liquid one on the cured one. There is no particular limitation.

  Although the ratio of the soil to 100 parts of the soil pavement material of the present invention is not particularly limited, it is usually preferably 100 to 1000 parts, more preferably 200 to 600 parts. If the soil content is lower than 100 parts, the strength development is high, but it is economically undesirable. If it is higher than 1000 parts, the strength is low, and there is a possibility of being dented.

The soil used in the present invention includes any one or more of gravel, sand, gravel, and clay, and is not particularly limited. Sandy soil such as mountain sand, river sand and sea sand, silty soil, clay soil, residual soil generated from construction, lightweight aggregate and recycled aggregate can be used. Generally, natural sands such as masago and dry sands are more preferable because of their stable quality.

  In the present invention, the mixing amount of water is preferably 15 to 100 parts with respect to 100 parts of the soil pavement material. If it is less than 15 parts, mixing may be difficult, and if it exceeds 100 parts, strength may not be obtained.

  In the present invention, it is possible to use a setting regulator. The setting modifier is not particularly limited as long as it promotes or delays setting of the cement. Specifically, alkali hydroxide, alkali metal chloride, alkali metal carbonate, oxycarboxylic acid or its salt, phosphoric acid or its salt, dextrin, sucrose, polyacrylic acid or its salt, further naphthalene, melamine It is possible to use one or more water reducing agents, such as water-based, aminosulfonic acid-based, polycarboxylic acid-based, and polyether-based water reducing agents, as long as the object of the present invention is not substantially inhibited.

  In the present invention, low-pH solidifying materials such as magnesium oxide, wood chips, bulking fillers such as rice hulls, various portland cements, calcium hydroxide, calcium chloride, limestone fine powder, fly ash, kaolin, shirasu, diatomaceous earth And admixture materials such as silica fume, defoamers, thickeners, rust inhibitors, antifreeze agents, polymers, clay minerals such as bentonite, anion exchangers such as hydrotalcite, and vinylon fibers, polypropylene fibers, glass fibers, etc. One or more short fibers having a length of 10 mm or less, a colorant, and the like can be used in a range that does not substantially inhibit the object of the present invention.

Next, the pavement method according to the present invention will be described.
In constructing the soil pavement material according to the present invention, the construction method is not particularly limited as long as the soil pavement materials are uniformly mixed. Such pavement by the soil pavement method according to the present invention is suitably applied to, for example, the road side of a road, a median strip, a tree planting zone, a garden, a park, around various facilities, and the like.

Hereinafter, description will be made based on experimental examples of the present invention.

"Experimental example 1"
100 parts of calcium aluminate shown in Table 1 were prepared with respect to 100 parts of gypsum, and the curing time, compressive strength, and initial frost damage were measured.
To the total of 100 parts of calcium aluminate and gypsum shown in Table 1, the soil was 600 parts, and the total of 100 parts of calcium aluminate, gypsum and aggregate was 0.5 part of sodium citrate as a setting modifier. And 20 parts of water were added to prepare a soil pavement material. The results are shown in Table 1.

<Material used>
Gypsum: natural anhydrous gypsum, Blaine specific surface area value 5000 cm ² / g
Soil: dried sand from Niigata Prefecture, 1.2 mm sieve Sewage: tap water Alumina cement: Alumina cement No. 1, manufactured by Denka, CaO / Al ₂ O ₃ molar ratio 1.0, crystalline coagulation regulator: citric anhydride Sodium, manufactured by Iwata Chemical Industry Co., Ltd.

<Measurement method>
Hardening time: The time during which the kneaded soil hardening material was not dented even when pressed with a finger was measured.
Compressive strength: The uniaxial compressive strength is based on the uniaxial compressive test method of the stabilized mixture in an environment of 20 ° C. and a relative humidity of 60% (Pavement Test Method Handbook, Japan Road Association), and the specimen size is 100 mm in diameter. The sample was a column with a height of 127 mm, and the specimen was prepared 25 times in three layers. The aging was measured for 6 hours and 28 days, and the curing method was air-dry curing under an environment of 20 ° C. and a relative humidity of 60%.
Initial frost damage resistance: Kneaded in the same manner as the compressive strength in an environment of 20 ° C. and a relative humidity of 60%, and immediately after being prepared, the specimen was cured in an environment of −10 ° C. until the age of 7 days. Thereafter, the sample was air-dried under an environment of 20 ° C. and a relative humidity of 60% until the age of 28 days, and the strength was measured. The strength reduction ratio was calculated by comparing the strength with the 28-day strength which was constantly kneaded and cured in a 20 ° C. environment.

Table 1 shows that the soil pavement material of the present invention exhibits excellent hardening characteristics, strength development, and frost damage resistance. Further, it can be seen that curing takes time depending on the type of calcium aluminate, and is inferior in initial freeze damage resistance.

"Experimental example 2"
Experiment 1 was carried out in the same manner as in Experiment 1, except that the calcium aluminate of Experiment Nos. 1-4 was used and the proportions of calcium aluminate and gypsum were changed in the proportions shown in Table 2. The results are shown in Table 2.
For comparison, a mortar and a magnesia-based solidified material using ordinary cement were prepared. The mortar was prepared as described in JISR 5201 with a water cement ratio of 50% and a ratio (mass ratio) of standard sand and ordinary Portland cement manufactured by Japan Cement Association of 3/1. As the magnesia-based solidification material, soil pavement material was prepared by adding 600 parts of soil and 20 parts of water to 100 parts of commercially available magnesium oxide obtained by firing Chinese magnesium.
Compressive strength and initial frost damage resistance were measured in the same manner as in Experimental Example 1, and bending strain and GB restitution coefficient were also measured.

<Material used>
Calcium aluminate: CaO / Al ₂ O ₃ molar ratio 2.2, impurity content 2%, vitrification rate 97%, Blaine specific surface area value 5000 cm ² / g
Gypsum: natural anhydrous gypsum, Blaine specific surface area value 5000 cm ² / g
Setting regulator: anhydrous sodium citrate, soil manufactured by Iwata Chemical Industry Co., Ltd. Soil: dried river sand from Niigata prefecture, 1.2 mm sieve sewage: tap water ordinary cement: ordinary portland cement, commercial sand: standard sand manufactured by Japan Cement Association Magnesia solidifying material: Magnesium oxide obtained by firing Chinese magnesium, commercially available

<Measurement method>
Flexural strain: Based on JIS A 1106, the strain at the time of breaking when a bending test was performed was measured and used as a measure of flexibility.
GB coefficient of restitution: After laying each soil solidifying agent uniformly on the soil in an environment of 20 ° C. and a relative humidity of 60%, on a measurement road surface formed by compacting with a hand vibrator after 6 hours and 28 days, The golf ball was allowed to fall naturally from a height of 1 m, and the rebound height was measured and used as a measure of elasticity.

Table 2 shows that the soil pavement material of the present invention exhibits excellent physical properties. The comparative mortar has a low short-term strength and a high strength at a material age of 28 days, but has a high GB resilience coefficient indicating elasticity and high rigidity, and thus has a low bending strain. In addition, since the short-time strength is low, it can be seen that it has been subjected to initial frost damage. It can be seen that the magnesia-based solidified material has low strength, low bending strain, and suffered initial frost damage.

"Experimental example 3"
600 parts of soil and 20 parts of water were added to a total of 100 parts in which calcium aluminate and gypsum of Experiment Nos. 1-4 of Experiment Example 1 were mixed in equivalent amounts, and calcium silicate was mixed at a ratio shown in Table 3. In addition, a soil pavement material was prepared.
In order to measure the long-term strength, it was measured at the age of 6 hours and 180 days, and was carried out in the same manner as in Experimental Example 2 except that the type of soil was changed.

<Material used>
Calcium silicate i: 3 mol of 3CaO.SiO ₂ reagent calcium carbonate and 1 mol of silicon dioxide were mixed and pulverized, followed by firing in an electric furnace to synthesize. Blaine specific surface area value of 1800 cm ² / g.
Calcium silicate: After mixing and pulverizing 2 mol of calcium carbonate and 1 mol of silicon dioxide as a β-2CaO · SiO ₂ reagent, the mixture was baked in an electric furnace to synthesize. Blaine specific surface area value of 1800 cm ² / g.
Calcium silicate C: 2 mol of calcium carbonate and 1 mol of silicon dioxide as a γ-2CaO · SiO ₂ reagent were mixed and pulverized, followed by firing in an electric furnace to synthesize. Blaine specific surface area value of 1800 cm ² / g.
Soil: Masato soil from Aichi prefecture, 5mm sieve

Table 3 shows that the soil pavement material of the present invention shows excellent physical properties. It can be seen that the mixing of calcium silicate increases the strength of 180 days and does not significantly affect the shock absorption (GB restitution coefficient or bending strain).

"Experimental example 4"
600 parts of soil were added to a total of 100 parts of a mixture of calcium aluminate and gypsum of Experiment Nos. 1-4 of Experimental Example 1 mixed with equivalent amounts of a cement admixture and an asphalt emulsion at the ratios shown in Table 4. , And 20 parts of water were added to prepare a soil pavement material.

<Material used>
Polymer for cement admixture: EVA emulsion, solid concentration 20%
Polymer for cement admixture: chloroprene latex, solid content concentration 20%
Polymer for cement admixture: acrylic emulsion, solid content concentration 20%
Asphalt emulsion: Main component asphalt, bitumen content 60%, Toa Road Industry Co., Ltd. Soil: Masato soil from Aichi Prefecture, 5mm sieve

From Table 4, it can be seen that the soil pavement material of the present invention has a low GB resilience coefficient indicating elasticity, a large bending strain, and excellent shock absorption by mixing a polymer for cement admixture and an asphalt emulsion.

  Since the soil pavement material of the present invention can be quickly opened because of its quick-hardening property, stable pavement can be performed even in a cold region or a low-temperature environment, and it is possible to provide a soil pavement material excellent in shock absorption. It is mainly used in civil engineering and construction fields.

Claims (2)

Calcium aluminate having a vitrification ratio of 70% or more, a CaO / Al ₂ O ₃ molar ratio of 2.0 to 2.7, an impurity of 15% or less, and a Blaine specific surface area of 3000 cm ² / g or more , γ-2CaO. A soil pavement material containing SiO ₂ , gypsum and soil , wherein γ-2CaO · SiO ₂ is 10 to 70 parts by mass in a total of 100 parts by mass of calcium aluminate, gypsum and γ-2CaO · SiO ₂ . Furthermore, soil paving material according to claim 1 which comprises one or more selected cement admixture for the polymer, the bitumen emulsion.