JP2017082092A - Soil pavement material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soil pavement material having rapid hardening property, excellent in resistance to freezing damage and good in impact absorption property.SOLUTION: There is provided (1) a soil pavement material containing calcium aluminate having vitrification rate of 70% or more, CaO/AlOmolar ratio of 1.0 to 2.7, impurities of 15% or less and Blaine specific surface area of 3000 cm/g or more and soil, (2) a soil pavement material further containing gypsum, (3) the soil pavement material of (1) or (2) containing one or more kind selected from calcium silicate, a polymer for cement admixture and an asphalt emulsion.SELECTED DRAWING: None

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 shock absorption and stabilization of road surface temperature. In particular, it is highly effective in suppressing the increase in road surface temperature, and is attracting attention as a countermeasure against the heat island phenomenon. Also, because it is easy to harmonize with the surrounding natural environment, it is also used for applications that place importance on the landscape, such as around parks, promenades, and historic buildings.

  Conventionally, as a soil pavement material, a lime-based, cement-based, or magnesia-based solidifying agent added to soil is known.

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

  The pavement by the soil pavement material using these cement type or quick lime type has a problem in the pavement having high rigidity and high elasticity. Moreover, since time is required for curing, there is a problem that early opening is impossible. Furthermore, it became a strong alkali having a pH of 12 or more, and there was a problem in the influence on surrounding vegetation and elution of hexavalent chromium.

  Moreover, what adds a magnesia type solidification agent with respect to soil is proposed. Soil pavement material (patent document 4) containing magnesium oxide and a different metal salt, pavement material (patent document 5) in which magnesium oxide having an average periclase crystallite diameter of 330 to 430 mm and soil are mixed in advance, There are soil improvers such as a water-permeable pavement composition mixture (Patent Document 6) containing a magnesia-based solidifying agent, an emulsifying resin, and water.

  In the pavement by the soil pavement material using the solidifying agent (hardening agent) containing these magnesias, there is a problem that the curing time is long, the solidification does not occur at a low temperature, and frost damage is caused.

Further, a soil-based solidified material using calcium aluminate-based slag has been proposed (Patent Document 7). When calcium aluminate-based slag is used, there are many impurities and the vitrification rate is low, so the reaction activity is increased by increasing the CaO / Al ₂ O ₃ molar ratio, but it contains cement, quicklime, and magnesia. As with the solidifying agent, the curing time is long, and there is a problem that it does not harden at low temperatures and suffers from frost damage.

JP-A-6-10305 Japanese Patent No. 2533452 Japanese Patent Laid-Open No. 9-87621 JP 2005-154735 A JP 2014-51849 A Japanese Patent No. 4310788 Japanese Patent No. 5561921

In conventional soil pavement materials, when cement-based solidifying agents (hardening agents) are used, there is a problem with highly rigid and elastic pavements. When magnesia-based solidifying agents and calcium aluminate slag are used Has a problem that it takes a long time to cure, does not harden at low temperatures, and suffers from frost damage.
The present invention solves the above-mentioned problems, and provides a soil pavement material that is fast-curing, excellent in resistance to frost damage, and excellent in shock absorption.

That is, the present invention has (1) a vitrification ratio of 70% or more, a CaO / Al ₂ O ₃ molar ratio of 1.0 to 2.7, impurities of 15% or less, and a brain 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 comprising (1) gypsum, (3) a calcium silicate, a cement admixture polymer, and an asphalt emulsion. The soil pavement material according to (1) or (2), which contains one or more selected ones.

According to the present invention, it is possible to provide a soil pavement material that is fast-curing, excellent in resistance to frost damage, and excellent in shock absorption.

Hereinafter, the present invention will be described in detail.
The parts and% 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 firing the kiln or melting and cooling in an electric furnace. It is a general term for substances having hydration activity, and is a material with a fast curing time and high initial strength development.
The calcium aluminate of the present invention is, for example, an amorphous calcium aluminate that is hardened in a shorter time than alumina cement and is rapidly cooled after melting a mixture of calcia raw material and alumina raw material from the viewpoint of high initial strength development thereafter. The molar ratio of CaO to Al ₂ O _{3 in} the calcium aluminate of the present invention that can be used (CaO / Al ₂ O ₃ molar ratio) is preferably 1.0 to 2.7, and preferably 2.0 to 2.5. More preferred. If it is less than 1.0, curing takes time, and if it exceeds 2.7, curing may be too early.

Components (impurities) other than CaO and Al ₂ O ₃ which are components of the calcium aluminate of the present invention are preferably 15% or less, more preferably 10% or less, from the viewpoint of initial strength development. If it exceeds 15%, the curing time is long, and there is a problem that it does not harden at low temperatures.
Typical examples of impurities contained in the calcium aluminate of the present invention include silicon oxide. In addition, alkali metal oxides, alkaline earth metal oxides, titanium oxide, iron oxide, alkali metal halides, alkaline earth metal halides. There are alkali metal sulfates, alkaline earth metal sulfates, and the like, which are substituted for a part of CaO and 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 development may be lowered.

The measurement of the vitrification rate of calcium aluminate is performed by measuring the main peak area S of the crystal mineral in advance by a powder X-ray diffraction method on the sample before heating, and then heating at 1000 ° C. for 2 hours, and then 1-10 ° C./min. Slow cooling is performed at the cooling rate, the main peak area S ₀ of the crystal mineral after heating is determined by powder X-ray diffraction, and the vitrification rate χ is calculated using the following equation using the values of S ₀ and S.
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 lowered.

Examples of the gypsum of the present invention include hemihydrate gypsum and anhydrous gypsum. In terms of strength development, anhydrous gypsum is preferable, and hydrofluoric acid byproduct anhydrous gypsum and natural anhydrous gypsum can be used. The pH when the gypsum is immersed in water is preferably from a weak alkali having a pH of 8 or less to acidic. When the pH is high, the solubility of the gypsum component becomes high, which may inhibit the initial strength development. The pH here is a value obtained by measuring the pH of the diluted slurry at 20 ° C. of gypsum / ion exchange water = 1 g / 100 g 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 with respect to 100 parts of calcium aluminate. If it is less than 50 parts, work time cannot be taken and strength development may fall. If it exceeds 150 parts, sufficient working time can be taken, but initial strength may not be obtained.

In the present invention, calcium silicate can be used for the purpose of increasing strength.
Calcium silicates include 3CaO · SiO ₂ and 2CaO · SiO ₂ , and are not particularly limited. However, γ-2CaO · SiO ₂ absorbs carbon dioxide in the atmosphere and increases strength, and thus 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 Is. All of these compounds are 2CaO · SiO ₂ and have the same chemical composition, but their crystal structures are different. 2CaO · SiO ₂ present in the cement clinker is β-2CaO · SiO ₂ . Although β-2CaO · SiO ₂ has hydraulic properties, γ-2CaO · SiO ₂ in the present invention does not have hydraulic properties, but has been found to have a property of absorbing and curing carbon dioxide in the atmosphere.
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 value is less than 3,000 cm ² / g, the carbon dioxide in the atmosphere may be absorbed and sufficient strength may not be obtained. Even if it exceeds 8,000 cm ² / g, further enhancement of the effect cannot be expected.

In the present invention, a cement-mixing polymer can be used for the purpose of imparting viscoelasticity and causing an impact such as vibration.
The cement-mixing polymer of the present invention is, for example, a cement-mixing polymer specified in JIS A 6203, and is used in polymer dilversion in which fine particles of polymer are dispersed in water, rubber latex and resin emulsion. This refers to a re-emulsified powder resin obtained by drying a material to which a stabilizer or the like is added.
For example, rubber latex such as acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, and natural rubber, ethylene-vinyl acetate copolymer, polyacrylic acid ester, vinyl acetate vinyl versatate copolymer, and styrene-acrylic Examples include acid ester copolymers, acrylic acid ester copolymers represented by acrylonitrile / acrylic acid esters, epoxy resins, liquid polymers represented by unsaturated polyester resins, and the like. Mixtures can be used. These can be used in liquid or powder form and are not particularly limited.

Furthermore, in the present invention, an asphalt emulsion can be used for the purpose of imparting viscoelasticity and causing an impact such as vibration.
The asphalt emulsion of the present invention is a colloidal liquid obtained by dispersing asphalt fine particles mainly composed of a bituminous product obtained in nature or as a petroleum distillation residue, in water. Mainly straight asphalt with a penetration of about 40/60 to 200/500, a surfactant and a polyvalent metal salt are added thereto, and further, an emulsification aid, a dispersing agent, a protective colloid, etc., if necessary Is emulsified in water using as appropriate.
It is also possible to use a bituminous material obtained by emulsifying a modified bituminous material by adding and mixing rubber, a synthetic polymer or the like.
The bitumen content in the asphalt emulsion is preferably 40 to 70%, more preferably 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 either in liquid form or in bulk, 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, cement admixture polymer and asphalt emulsion for the purpose of enhancing strength and improving viscoelasticity. it can.
The blending ratio of calcium silicate, cement admixture polymer and 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. If the amount of calcium silicate, cement admixture polymer or asphalt emulsion is small, the long-term strength tends to be low, and if it exceeds 70 parts, the initial strength development tends to decrease, but the blending ratio of these is particularly limited is not.
The mixing method of cement admixture polymer or asphalt emulsion can be pre-mixed when kneading calcium aluminate before water and water, and it is also possible to spray liquid after curing. There is no particular limitation.

  Although the ratio of the soil with respect to 100 parts of soil pavement materials of this invention is not specifically limited, Usually, 100-1000 parts are preferable and 200-600 parts are more preferable. If the soil is lower than 100 parts, the strength development is high, but it is not economically preferable. If it is higher than 1000 parts, the strength is low and there is a possibility that it will be recessed.

The soil used in the present invention includes 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, clayey soil, residual soil generated from construction, lightweight aggregate and recycled aggregate can be used. In general, natural sand and dry sand, which are natural soils, are more preferable because of their stable quality.

  In the present invention, the blending 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 accelerates or delays the setting of the cement. Specifically, alkali hydroxide, alkali metal chloride salt, alkali metal carbonate, oxycarboxylic acid or salt thereof, phosphoric acid or salt thereof, dextrin, sucrose, polyacrylic acid or salt thereof, naphthalene, melamine One, two or more water reducing agents typified by a system, an aminosulfonic acid system, a polycarboxylic acid system, and a polyether system can be used as long as the object of the present invention is not substantially inhibited.

  In the present invention, low pH solidified material such as magnesium oxide, wood chip, bulking agent such as rice husk, various portland cement, calcium hydroxide, calcium chloride, fine limestone powder, fly ash, kaolin, shirasu, diatomaceous earth And silica fume admixtures, antifoaming agents, thickeners, rust inhibitors, antifreeze agents, polymers, clay minerals such as bentonite, anion exchangers such as hydrotalcite, vinylon fibers, polypropylene fibers, glass fibers, etc. One or two or more short fibers having a length of 10 mm or less, a colorant, and the like can be used within a range that does not substantially impair the object of the present invention.

Next, the pavement method in the present invention will be described.
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. Such a pavement by the soil pavement method according to the present invention is suitably applied to, for example, a roadside, a median strip, a tree planting zone, a garden, a park, and around various facilities.

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

"Experiment 1"
100 parts of calcium aluminate shown in Table 1 was prepared with respect to 100 parts of gypsum, and the setting time, compressive strength, and initial frost damage were measured.
The total amount of calcium aluminate and gypsum shown in Table 1 is 100 parts, and the soil is 600 parts. The total amount of calcium aluminate, gypsum, and aggregate is 100 parts. A soil pavement material was prepared by adding 20 parts of water. The results are also shown in Table 1.

<Materials used>
Gypsum: natural anhydrous gypsum, Blaine specific surface area value 5000 cm ² / g
Soil: dried river sand from Niigata prefecture, 1.2 mm Sieve water: tap water Alumina cement: Alumina cement No. 1, Denka, CaO / Al ₂ O ₃ molar ratio 1.0, crystalline coagulation modifier: anhydrous citric acid Sodium, manufactured by Iwata Chemical Industry

<Measurement method>
Hardening time: The time when the soiled solidified material was not depressed even when pressed with a finger was measured.
Compressive strength: Uniaxial compressive strength conforms to the uniaxial compression test method of the stable treatment mixture in an environment of 20 ° C. and 60% relative humidity (Japanese Road Association), and the specimen size is 100 mm in diameter. The height was 1 27 mm, and the specimen was prepared in 3 layers 2 5 times. The strength of the material was measured for 6 hours and 28 days, and the curing method was air drying in an environment of 20 ° C. and a relative humidity of 60%.
Initial freezing damage resistance: Kneaded in the same manner as the compressive strength in an environment of 20 ° C. and 60% relative humidity, and immediately after the specimen was prepared, it was cured in a −10 ° C. environment until the age of 7 days. Then, the strength was measured after air-drying in an environment of 20 ° C. and a relative humidity of 60% until the age of 28 days. The strength reduction ratio was calculated by comparing the value with the 28-day strength that was constantly mixed and cured in a 20 ° C. environment.

From Table 1, it can be seen that the soil pavement material of the present invention exhibits excellent hardening characteristics, strength development, and frost damage resistance. Moreover, it turns out that hardening requires time with the kind of calcium aluminate, and it is inferior to initial stage frost damage resistance.

"Experimental example 2"
The same procedure as in Experimental Example 1 was performed except that the calcium aluminate of Experiment No. 1-4 of Experimental Example 1 was used and the ratio of calcium aluminate and gypsum was changed in the ratio shown in Table 2. The results are shown in Table 2.
For comparison, mortar and magnesia solidified material using ordinary cement was prepared. A mortar described in JIS R 5201 was prepared by blending mortar with a water cement ratio of 50% and a ratio (mass ratio) of standard sand made by Cement Association and ordinary Portland cement to 3/1. A magnesia-based solidified 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.
The compressive strength and initial frost damage resistance were measured by the same measurement method as in Experimental Example 1, and the bending strain and GB restitution coefficient were also measured.

<Materials 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
Coagulation modifier: anhydrous sodium citrate, Soda Chemical Industries Co., Ltd. soil: dried river sand from Niigata Prefecture, 1.2 mm sieve water: tap water ordinary cement: ordinary Portland cement, commercial sand: standard sand made by Cement Association Magnesia-based solidification material: Magnesium oxide fired from Chinese magnesium, commercial product

<Measurement method>
Bending strain: Based on JIS A 1106, the strain at the time of the bending test was measured and used as a measure of flexibility.
GB coefficient of restitution: After each soil solidifying agent is evenly laid on the foundation surface in the environment of 20 ° C and 60% relative humidity, the measurement road surface formed by compacting with a hand vibrator after 6 hours and 28 days, The golf ball was naturally dropped from a height of 1 m, the bounce height was measured, and it was used as a measure of elasticity.

Table 2 shows that the soil pavement material of this invention shows the outstanding physical property. Although the comparative mortar has low strength for a short time and high strength at the age of 28 days, it can be seen that the bending strain is low because the GB restitution coefficient indicating elasticity is high and the rigidity is high. Moreover, since the intensity | strength is low for a short time, it turns out that it suffers from initial frost damage. It can be seen that the magnesia-based solidified material has low strength, low bending strain, and is subject to initial frost damage.

"Experiment 3"
For a total of 100 parts in which calcium silicate was mixed in the proportions shown in Table 3 in an equivalent mixture of calcium aluminate and gypsum of Experiment No. 1-4 of Experimental Example 1, 20 parts of water and 20 parts of water In addition, a soil pavement material was prepared.
In order to measure the long-term strength, the measurement was carried out in the same manner as in Experimental Example 2 except that the measurement was performed at a material age of 6 hours and 180 days and the type of soil was changed.

<Materials used>
Calcium silicate i: 3 mol of calcium carbonate as a 3CaO · SiO ₂ reagent and 1 mol of silicon dioxide were mixed and pulverized, and then baked in an electric furnace and synthesized. Blaine specific surface area value 1800 cm ² / g.
Calcium silicate: After mixing and grinding 2 mol of calcium carbonate and 1 mol of silicon dioxide of β-2CaO · SiO ₂ reagent, they were synthesized by firing in an electric furnace. Blaine specific surface area value 1800 cm ² / g.
Calcium silicate C: After mixing and grinding 2 mol of calcium carbonate and 1 mol of silicon dioxide of γ-2CaO · SiO ₂ reagent, they were synthesized by firing in an electric furnace. Blaine specific surface area value 1800 cm ² / g.
Soil: Aichi Prefectural sand sand, 5mm sieve

From Table 3, it can be seen that the soil pavement material of the present invention exhibits excellent physical properties. It can be seen that the strength of 180 days is increased by mixing calcium silicate, and the impact absorbability (GB restitution coefficient and bending strain) is not greatly affected.

"Experimental example 4"
600 parts of soil to 100 parts in total of the mixture of calcium aluminate and gypsum of Experiment No. 1-4 in Experiment Example 1 mixed with the cement admixture polymer and asphalt emulsion in the proportions shown in Table 4 The same procedure as in Experimental Example 3 was conducted except that 20 parts of water was added to prepare a soil pavement material.

<Materials used>
Polymer admixture for cement: EVA emulsion, solid content 20%
Cement admixture polymer: chloroprene latex, solid content 20%
Cement admixture polymer c: acrylic emulsion, solid content 20%
Asphalt emulsion: main component asphalt, bitumen content 60%, soil made by Toa Road Industry Co., Ltd.

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

  Since the soil pavement material of the present invention is fast-hardening, it can be opened early, stable pavement can be achieved even in cold regions and low-temperature environments, and it is possible to provide a soil pavement material excellent in shock absorption. Mainly used in civil engineering and construction fields.

Claims (3)

Contains calcium aluminate and soil with a vitrification rate of 70% or more, CaO / Al ₂ O ₃ molar ratio of 1.0 to 2.7, impurities of 15% or less, and Blaine specific surface area of 3000 cm ² / g or more. Soil pavement material. The soil pavement material according to claim 1, further comprising gypsum. Furthermore, the soil pavement material of Claim 1 or 2 formed by containing the 1 type (s) or 2 or more types chosen from the calcium silicate, the polymer for cement mixing, and an asphalt emulsion.