JP2007246770A - Hydrogel composition and ground improvement method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a hydrogel composition that not only improves ground in the vicinity of underground structure but also shows an alkali region of pH to control bacterial growth of underground and acidification of ground. <P>SOLUTION: The hydrogel composition comprises a polyvinyl alcohol-based polymer, water, an organotitanium compound and a calcium alumino-ferrite compound. The hydrogel composition has a viscosity of ≤10,000 mPa s for ≥10 minutes after mixing the components. The hydrogel composition shows pH<8 before gelation and pH≥9 after gelation. The ground improvement method comprises using the hydrogel composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrogel composition mainly used in the field of civil engineering and construction, and a ground improvement method using the same.

In recent years, methods have been proposed for improving the surrounding ground of underground structures such as subways, tunnels, and sewage pipes to a ground having deformation followability. The main purpose is to minimize the destruction of the structure even if the ground is deformed due to the structure's own weight or external stress such as an earthquake, and to suppress traffic vibrations of trains and cars. As the composition, a gel composition mainly composed of polyvinyl alcohol having a small environmental load has been proposed (Patent Documents 1, 2, 3, and 4).
JP 2002-294014 A JP 2002-371278 A JP 2005-162984 A JP 2005-220738 A

There are general bacteria and Escherichia coli in the ground, and their contents are regulated by water quality standards. Carbon components such as polyvinyl alcohol can be a nutrient source for these bacteria. Further, it is known that general bacteria and Escherichia coli are easy to reproduce in a neutral region having a pH of 5 to 9, and difficult to reproduce in an alkaline region. Many conventional hydrogel compositions have an acidic to neutral pH after gelation.
Therefore, the present invention provides a hydrogel composition that not only improves the ground around the underground structure, but also exhibits an alkaline region with a pH that suppresses bacterial growth in the underground and acidification of the ground.

  That is, (1) a hydrogel composition containing a polyvinyl alcohol polymer, water, an organic titanium compound, and a calcium aluminoferrite compound, (2) a viscosity after mixing each component is 10 minutes or more and 10,000 mPa · s or less (1) hydrogel composition of (1), (3) the hydrogel composition of (1) or (2), wherein the pH before gelation is less than 8 and the pH after gelation is 9 or more, (4) (1) A ground improvement method using the hydrogel composition of any one of (3).

  By improving the ground around the underground structure using the hydrogel composition of the present invention, it is possible to minimize the destruction of the structure even if the ground is deformed, and to suppress traffic vibrations such as trains and automobiles. . Moreover, it is possible to suppress underground bacterial growth and ground acidification.

The polyvinyl alcohol polymer (hereinafter abbreviated as PVA) used in the present invention has a hydroxyl group and substantially water solubility, including fully saponified PVA and partially saponified PVA. If so, various modified PVAs to which acrylic acid, crotonic acid, maleic acid, acrylamide, etc. are added can be used.
500-3000 are preferable and, as for the average degree of polymerization of PVA used for this invention, 1000-2000 are more preferable. The degree of saponification of PVA is preferably 80 mol% or more, more preferably 90 mol% or more. When the degree of polymerization or saponification of PVA is outside the above range, fluidity before curing, strength after curing, elasticity, and water shielding properties may be impaired.

  The PVA used in the present invention is preferably prepared in advance as an aqueous solution. The solid content concentration is appropriately determined depending on the application and is not particularly limited, but it is usually preferably about 3 to 25% by mass. If it is less than 3% by mass, the cured body may have insufficient elasticity, and if it exceeds 25% by mass, the viscosity of the aqueous solution may become too high.

  The organic titanium compound used in the present invention is water-soluble, can be used as long as it is stable in an acidic to neutral region and reacts with a hydroxyl group or a carboxyl group in an alkaline region. In particular, titanium lactate obtained by reacting titanium alkoxide with lactic acid, a hydroxycarboxylic acid, titanium acetylacetonate obtained by reacting titanium alkoxide with acetylacetone, a β-diketone, and titanium alkoxide reacted with triethanolamine, an alkanolamine. It is preferable to include titanium triethanolaluminate, titanium oxalate obtained by reacting oxalic acid, which is a dicarboxylic acid, with titanium alkoxide. In addition, titanium peroxy compounds disclosed in JP-A Nos. 2000-159786 and 2004-43353 can also be used. Various types of titanium ligands, such as citric acid, malic acid, and glycolic acid, are known and have been shown to be stably soluble in water. In addition, powders such as ammonium salts and sodium salts are also known.

The calcium aluminoferrite compound used in the present invention is obtained by heat-treating a calcium source such as limestone, lime and slaked lime, an aluminum source such as bauxite and alumina, and a ferrite source such as iron oxide by a predetermined method. The heat treatment temperature is preferably 1200 to 2000 ° C, and more preferably 1400 to 1600 ° C. If it is less than 1200 degreeC, a predetermined compound may not be obtained, and if it exceeds 2000 degreeC, it may become uneconomical. The atmosphere during firing may be an oxidizing atmosphere or a reducing atmosphere. Moreover, a rotary kiln, an electric furnace, etc. can be used for baking facilities. In the raw material, in addition to CaO, Al ₂ O ₃ and Fe ₂ O ₃ as main components, SiO ₂ , MgO, TiO ₂ , P ₂ O ₅ , Na ₂ O, K ₂ O, fluorine, chlorine, Although impurities such as heavy metals may be included, there is no particular problem as long as the object of the present invention is not substantially impaired.

Fineness of calcium alumino ferrite compound is not particularly limited, but is preferably 1500~8000cm ² / g in Blaine specific surface area, 3000~6000cm ² / g is more preferable. If the coarse particles are less than 1500 cm ² / g, sufficient strength may not be obtained, and if the fine powder exceeds 8000 cm ² / g, the reactivity may be high and sufficient pot life may not be ensured.

The vitrification rate of the calcium aluminoferrite compound is not particularly limited, and it can be used in the present invention whether crystalline or amorphous. Calcium aluminosilicate ferrite compound of crystalline compounds, such as _{4CaO · Al 2 O 3 · Fe} 2 O 3 and _{6CaO · 2Al 2 O 3 · Fe} 2 O 3 are well known. Two or more of these can be used in combination.
In the present invention, the vitrification rate was measured by the following X-ray diffraction Rietveld method. A predetermined amount of an internal standard substance such as aluminum oxide or magnesium oxide is added to the pulverized sample, and after sufficient mixing in an agate mortar, powder X-ray diffraction measurement is performed. Analyze the measurement results with quantitative software to determine the vitrification rate. “SIROQUANT” manufactured by Sitronics was used as the quantitative software.

  The blending ratio of PVA, water, organic titanium compound, and calcium aluminoferrite compound, which are each component in the present invention, is not particularly limited because it varies depending on the application, but PVA, water, organic titanium compound, and calcium alumino compound are not limited. In the total 100 parts by mass of the ferrite compound, PVA is preferably 3 to 12 parts by mass, and more preferably 5 to 10 parts by mass. The amount of water is preferably 45 to 75 parts by mass, and more preferably 50 to 70 parts by mass. The organic titanium compound is preferably 1 to 18 parts by mass, and more preferably 5 to 10 parts by mass. Similarly, 5-45 mass parts is preferable and, as for a calcium alumino ferrite compound, 10-40 mass parts is more preferable. Outside these ranges, when the viscosity of the hydrogel composition before gelation becomes high, the pH after gelation becomes an acidic region, the time required for gelation becomes long, or the elasticity of the hydrogel composition becomes low There is. The gelation as used in the present invention means that the liquid level does not change even if the container into which the mixed composition is poured is tilted.

The method of mixing the hydrogel composition of the present invention is not particularly limited, but the method of adding the organic titanium compound to the PVA aqueous solution and stirring, and finally adding the calcium aluminoferrite compound to obtain the composition of the present invention, PVA There is a method in which calcium aluminoferrite is added to an aqueous solution and stirred, and finally an organic titanium compound is added to obtain the composition of the present invention.
The hydrogel composition before gelation of the present invention changes from an acidic region to an alkaline region with the hydration reaction of the calcium aluminoferrite compound. The organotitanium compound acts as a hydration retarder for the calcium aluminoferrite compound and can be kept below pH 8 for a while after mixing. The hydrogel composition is preferably in the acidic to neutral region, specifically, about 3 to 8 in terms of pH and work safety. When the pH is 8 or more, alkaline chemical damage may occur when it adheres to the skin. If ordinary cement is used instead of the calcium aluminoferrite compound, the pH will exceed 9 immediately after mixing.

The viscosity of the hydrogel composition before gelation of the present invention is 10000 mPa · s or less, preferably 5000 mPa · s or less. If the viscosity of the hydrogel composition before gelation exceeds 10,000 mPa · s, it may be difficult to inject into the ground or mix with earth and sand.
There are various methods for measuring the viscosity of the hydrogel composition. In the present invention, a TV-10 viscometer manufactured by Toki Sangyo Co., Ltd. was used. The rotor used was H6, and the rotor rotation speed was evaluated at 20 rpm. 500 ml of the mixed composition was put into a beaker having a capacity of 500 ml, and the height was adjusted so that the rotor was immersed up to the immersion mark (portion where the rotor shaft was narrowed). The environmental temperature was 20 ° C., and the unit of measured viscosity was expressed in mPa · s. Moreover, it is preferable that the time for the viscosity of the hydrogel composition to change from 10,000 mPa · s to 50000 mPa · s is short. If it is too long, the hydrogel composition may be diffused by the groundwater and the ground may not be improved.

  In the hydrogel composition of this invention, what is conventionally used as a crosslinking agent of a hydroxyl group or a carboxyl group can be used together in the range which does not impair the effect of this invention. Conventional cross-linking agents include aliphatic aldehydes, aromatic aldehydes, compounds having a methylol group such as trimethylol melamine, boron compounds such as borax and boric acid, metal alkoxides in which Zr, Al, etc. are bonded to an organic substance. And compounds having an isocyanate group.

  In the present invention, organic acids such as citric acid, acetic acid, gluconic acid, oxalic acid, formic acid and lactic acid can also be used for the purpose of controlling the gelation rate of the hydrogel composition.

  In the hydrogel composition of the present invention, a filler can be used for the purpose of controlling the strength, elastic modulus and density of the cured product. The filler is not particularly limited, and an inorganic or organic filler can be used. Examples of inorganic materials include aggregates such as silica and limestone, clay minerals such as bentonite, ion exchangers such as zeolite, calcium aluminate compounds, and organic materials such as vinylon fiber, acrylic fiber, and carbon fiber. Fibrous materials, ion exchange resins, water-absorbing polymers, and the like. These can be used as long as the object of the present invention is not impaired.

  As the mixing device for the hydrogel composition in the present invention, any existing device can be used, and examples thereof include a tilting cylinder mixer, an omni mixer, a Henschel mixer, a V-type mixer, and a nauter mixer.

  The method for improving the ground using the hydrogel composition of the present invention is not particularly limited. For example, in the case of injection into cavities around underground structures such as tunnels and sewer pipes, After drilling a hole in a concrete wall where water leakage is observed and setting an injection plug, the hydrogel composition of the present invention is injected using various pumps to fill the cavity and form a water shielding layer on the back of the concrete. Moreover, it is also possible to inject using various injection pumps by inserting an injection tube from the ground around the cavity or around the structure.

  Examples will be described in detail below.

"Example 1"
Using PVA having a polymerization degree of 1700 and a saponification degree of 98.7 mol% and tap water, the solid content concentration was blended to be about 10% by mass and heated to 80 ° C. to prepare an aqueous PVA solution. Using this PVA aqueous solution, the organic titanium compound (a) is mixed so as to have the ratio shown in Table 1, and the calcium aluminoferrite compounds (a), (b), (c) are further mixed and mixed. The viscosity and pH of the hydrogel composition at the end, the time when the viscosity of the hydrogel composition is 10000 mPa · s or less, the time when the viscosity of the hydrogel composition changes from 10000 mPa · s to 50000 mPa · s, and after 1 day The pH and elasticity of the hydrogel composition was evaluated. The results are shown in Table 1.

"Materials used"
PVA: manufactured by Denki Kagaku Kogyo Co., Ltd., K17, polymerization degree 1700, saponification degree 98.7 mol%
Organic titanium compound (A): Titanium lactate 40 mass% aqueous solution, manufactured by Matsumoto Pharmaceutical Co., Ltd., trade name “TC-315”, titanium concentration 8.2 mass%, pH 1.5
Organic titanium compound (I): Matsumoto Pharmaceutical Co., Ltd., trade name “TC-400”, diisopropoxytitanium bis (triethanolamate), titanium concentration 8.3% by mass, pH 9.5, 3-fold diluted product calcium alumino ferrite compound _{(a): 4CaO · Al 2} O 3 · Fe 2 O 3, CaO46.1 _{wt%, Al} 2 O 3 21.0 _{wt%, Fe} 2 O 3 32.9 mass%, vitrification ratio of 0%, A brane specific surface area of 6000 cm ² / g, a density of 3.50 g / cm ³ , reagent primary calcium carbonate, aluminum oxide, and iron oxide were mixed and pulverized in a predetermined ratio, and baked at 1350 ° C. for 3 hours, and pulverized with a disk mill.
Calcium aluminoferrite compound (b): 6CaO · 2Al ₂ O ₃ · Fe ₂ O ₃ , CaO 48.1 mass%, Al ₂ O ₃ 29.1 mass%, Fe ₂ O ₃ 22.8 mass%, vitrification rate 0 %, Blaine specific surface area of 6000 cm ² / g, density of 3.49 g / cm ³ , and synthesis conditions are the same as (a).
Calcium aluminosilicate ferrite compound _{(c): 6CaO · 2Al 2} O 3 · Fe 2 O 3, CaO48.1 _{wt%, Al} 2 O 3 29.1 _{wt%, Fe} 2 O 3 22.8 mass%, vitrification ratio 0 %, Blaine specific surface area of 3000 cm ² / g, density of 3.49 g / cm ³ , and synthesis conditions are the same as (a).
Water: Tap water Ordinary cement: Commercial ordinary Portland cement

"Measuring method"
Viscosity of hydrogel composition: As a viscometer, a TV-10 viscometer manufactured by Toki Sangyo Co., Ltd. was used. 500 ml of the mixed hydrogel composition was transferred to a beaker having an inner diameter of 85 mm and a capacity of 500 ml, and the measurement was performed in a 20 ° C. environment. The rotor was H6, and the rotation speed of the rotor was 20 rpm. Under this condition, the viscosity in the range of 0 to 50000 mPa · s is measured.
Composition pH: A pH electrode was inserted into 100 ml of the hydrogel composition, and measurement was performed at the end of mixing and after 1 day. When the hydrogel composition was gelled, holes were made in the hydrogel composition and electrodes were inserted.
Elasticity: The mixed composition was poured into a 5 × 5 × 5 cm mold, demolded at a material age of 1 day, loaded with 1 cm from the top using a commercially available pressure tester, and then unloaded. The restoration rate was measured by measuring the height (xcm) of the specimen after unloading. The restoration rate was calculated by [1- (5-x)] × 100 (%) and used as an elasticity index.
Mold propagation state: 100 ml of the hydrogel composition was placed in a plastic bag and left in a sealed state in a room at 20 ° C. and 80% humidity. One month later, the occurrence of mold around the hydrogel was visually evaluated.

  As shown in Table 1, the hydrogel composition of the present invention has a low viscosity for a certain period from immediately after mixing, and can ensure time for pouring and mixing with earth and sand. The pH before gelation is a weakly acidic region and is safe. It is considered that the time from when viscosity begins to increase after a certain period of time to gelation is relatively short, and it is difficult to be washed away into groundwater. Moreover, it turns out that it changes into alkalinity after gelation, and elasticity is expressed, and it is understood that mold | fungi are also hard to reproduce.

"Example 2"
The blending ratio of PVA, water, organic titanium compound, and calcium aluminoferrite compound was fixed at 7.2 parts by mass, 64.3 parts by mass, 9.5 parts by mass, and 19.0 parts by mass, respectively, and the polymerization degree of PVA The procedure was the same as in Example 1 except that the degree of saponification was changed. The results are shown in Table 2.

  As shown in Table 2, the hydrogel composition of the present invention has a low viscosity for a certain period from immediately after mixing by using a specific PVA, and can secure time for pouring and mixing with earth and sand. Moreover, the pH before gelation is also a weakly acidic region and is safe. Moreover, it turns out that it changes into alkalinity after gelation, and elasticity is expressed, and it is understood that mold | fungi are also hard to reproduce.

"Example 3"
PVA, water, an organic titanium compound, and a calcium aluminoferrite compound were blended as shown in Table 3, and the same procedure as in Example 1 was performed except that only the concentration of the PVA aqueous solution was changed. The results are shown in Table 3.

  As shown in Table 3, the hydrogel composition of the present invention can lower the viscosity for a certain period from immediately after mixing by adjusting the PVA concentration, and can secure the time for pouring and mixing with earth and sand. The pH before gelation is also a weakly acidic region and is safe. Moreover, it turns out that it changes into alkalinity after gelation, and elasticity is expressed, and it is understood that mold | fungi are also hard to reproduce.

  By improving the ground around the underground structure using the hydrogel composition of the present invention, it is possible to minimize the destruction of the structure even if the ground is deformed, and to suppress traffic vibrations such as trains and automobiles. . Moreover, it is possible to suppress underground bacterial growth and ground acidification. Therefore, it can be widely applied in the fields of civil engineering and architecture.

Claims (4)

A hydrogel composition comprising a polyvinyl alcohol polymer, water, an organic titanium compound, and a calcium aluminoferrite compound. The hydrogel composition according to claim 1, wherein the viscosity after mixing each component is 10 minutes or more and 10,000 mPa · s or less. The hydrogel composition according to claim 1 or 2, wherein the pH before gelation is less than 8 and the pH after gelation is 9 or more. The ground improvement method using the hydrogel composition of any one of Claims 1-3.