JP2009102925A - Degradation reducing method and degradation reducing material for cement-based mixed improved body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for firmly solidifying an improved body and reducing the degradation of the solidified improved body while minimizing elution of heavy metal from the improved body. <P>SOLUTION: A mixing method for injecting and mixing a cement-based improving material into the ground to construct the cement-based mixed improved body, comprises adding and mixing, into the cement-based improving material, an improved body degradation reducing material formed of material mainly composed of metal salt containing at least sodium carbonate, sodium chloride, potassium carbonate, potassium chloride and ammonium chloride excluding heavy metal, and injecting the mixed cement-based improving material into the ground while agitating it with agitation blades to construct the improved body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mixed processing method in which a cement-based improvement material is constructed by injecting and mixing a cement-based improvement material into the ground, and an improved body deterioration reducing material is added to the cement-based improvement material, so that the deterioration of the periphery of the improvement body It is related with the deterioration reduction method and deterioration reduction material of the cement-type mixing treatment improvement body which reduce pollution, and prevent the contamination of the ground by the heavy metal to the object location and surrounding ground which caused deterioration.

When building structures such as road foundations, residential foundations, river dike foundations, breakwater foundations, revetment foundations, pier foundations, pier foundations, tank foundations, building foundations, retaining wall foundations, and underground structural walls on soft ground, Various mixes to solidify the ground with cement-based improvement materials and secure a solid foundation for the purpose of ensuring stability, preventing settlement, preventing lateral movement, preventing liquefaction, water blocking walls, underground structural walls, etc. Processing methods are being implemented.
Improved bodies obtained by the mixing treatment method have been applied to various uses by taking advantage of excellent quality characteristics such as ensuring the required strength at the current position. The mixed treatment method includes surface layer treatment method, deep layer treatment method, middle layer mixed treatment method, columnar column method, soil cement column wall method, underground continuous wall method, etc. In order to perform the function for a long period of time, the strength of each part inside the improved body should not be lower than the material strength set at the time of design even though it increases with the aging of the material.
However, even if a strong improved ground is created, the boundary of the cement-based improved ground is exposed to the surrounding ground and groundwater, so that the surface of the improved body, that is, the portion in contact with the surrounding ground is gradually chemically It has been confirmed that a reaction occurs and the periphery of the improved body is eroded, deteriorates, and the strength decreases. As these degradations progress, there is a risk of losing structural stability in the worst case.

  The mechanical properties of the cement-based mixed treatment improved body have been examined in detail for 30 years, but studies on long-term durability are limited. Regarding the long-term soundness of the improved body, the uniaxial compressive strength after 20 years in actual construction shows a tendency to increase in the long term, and 1.6 times to 2.6 from 93 days to 20 years after construction. While there is a report that it has been confirmed that the strength is doubled, there is also a report that the surface of the improved body is surely deteriorated, and the progress of deterioration is promoted for the construction of a safe and reliable structure. There is a demand for a technology that suppresses and suppresses the above.

Specifically describing the deterioration of the improved body, as shown in FIG. 5, regarding the long-term soundness of the solidified improved body 26, in the periphery of the improved body, as the material age elapses after the construction, A strength lowering phenomenon occurs, and the improved body is deteriorated in that portion. The peripheral part of the improved body improved in the mixed processing method is the result of measurement by actual construction, as a result of several months to one year after construction.
A degradation region of 30 mm to 50 mm has been measured after 10 years from construction to 20 mm.
Although it is desirable for the soundness that the diameter D of the improved body 26 does not deteriorate for a long time, the outflow of the Ca amount in the improved body 26 occurs in the soil of the ground 31 around the improved body 26, and the improved body peripheral deterioration portion 33. The thickness d of the improved body peripheral deterioration portion 33 gradually progresses, and accordingly, the strength of the improved body peripheral deterioration portion 33 becomes extremely low, and the improved body constructed as a part of the improved body 26 There is a risk that heavy metals such as hexavalent chromium that have been insolubilized in the peripheral deterioration portion 33 may be eluted.
Therefore, the present inventors have already proposed a method and apparatus for reducing elution of heavy metals such as hexavalent chromium eluted from a solidified improved body and heavy metals due to deterioration of the improved body (Patent Document 1). .
Japanese Patent No. 3698714

However, since it was found that there are still some problems, various studies were conducted to reduce elution of heavy metals such as hexavalent chromium eluted from the solidified improved body and heavy metals due to deterioration of the improved body. It has been found that the deterioration of the solidified improved body can be reduced by adding the improved body deterioration reducing material to the cement-based improving material and mixing it with the ground.
The first problem to be solved by the present invention is to provide a method for solidifying the improved body and reducing deterioration of the solidified improved body as much as possible.
The second problem to be solved by the present invention is to provide a simple and economical method for solving the first problem.

The method and apparatus for reducing the elution of heavy metals in the improved body described in Patent Document 1 includes a cement-based ground improvement material that forms a sparingly soluble compound by combining with heavy metals in the ground improved body. Mixing process of liquid curing agent to add and harden alkaline curing agent for strengthening the settling and fixing action, and injecting the cement-based improvement material mixed with this liquid curing agent into soft ground or loose sandy ground The curing agent is a liquid that exhibits alkalinity, and contains sodium carbonate and sodium chloride as main components in a solution of 70% by weight or more. Sodium salt, chloride ions and sodium ions whose contents are adjusted in the range of 1 to 10% by weight, cobalt whose content is 0.01 to 1.0% by weight, and whose content is 2% by weight or less. The amount of addition of this liquid curing agent is 0 with respect to the cementitious improvement material according to the property of the soil to be improved in the mixed treatment method. It is characterized in that it is set within the range of 3 to 15% by weight (C × wt%).
However, according to the above technology, although uniaxial compressive strength and elution amount of heavy metals have been seen for the time being, cobalt, which is a component, is a product subject to the chemical substance release and transfer notification system (PRTR system). In the present invention, various experiments were conducted by adjusting alkali components other than cobalt in the present invention. As a result, potassium chloride and other effective materials were handled in powder form and added in liquid form. The inventors have found a method for reducing the deterioration of the improved body and have completed the present invention.

The present invention relates to a mixed processing method in which a cement-based improvement material is constructed by injecting and mixing cement-based improvement material into the ground, and by adding an improved material deterioration reducing material to the cement-based improvement material, This is a method of reducing the deterioration of the part.
Specifically, the improved body deterioration reducing material is in the form of a powder exhibiting alkalinity, and is a material adjusted in the following range.
Sodium carbonate 20-50% by weight
Sodium chloride 20-50% by weight
Potassium carbonate 10-40% by weight
Potassium chloride 40 wt% or less Ammonium chloride 15 wt% or less Other 0-30 wt%

The improved body deterioration reducing material added and mixed with the cement-based improving material is 0.3 to 5% by weight, preferably 0.5 to 5% with respect to the cement-based improving material 1 depending on the properties of the soil to be improved in the mixing treatment method. It is set to be added within the range of 3% by weight. As a result, the method of the present invention can be realized simply and economically. It is effective for large-scale and wide-ranging construction such as deep-mixing treatment and small-scale construction such as columnar column method used for the foundation of residential ground, and the total cost can be reduced.
More specifically, the improved body deterioration reducing material includes a sodium salt mainly composed of sodium carbonate and sodium chloride. Sodium carbonate promotes the alkalinity of the solidified improved body and prevents a decrease in mechanical strength due to neutralization when the improved body deterioration reducing material is added to a cement-based improved material and solidified. Sodium chloride promotes cement hydration together with sodium carbonate when solidified by adding the improved material deterioration reducing material to the cement-based improved material, reducing the deterioration of the improved material and reducing heavy metals such as hexavalent chromium and hormones. It is possible to reliably prevent the inhibitory chemical substance from being eluted and diffused.
In the present invention, the content of sodium carbonate and sodium chloride was adjusted in the range of 20 to 50% by weight so that the pH of the improved body was higher than that of the surrounding soil. As a result, the action of heavy metals such as hexavalent chromium adsorbing to the soil does not proceed, and it is difficult to elute into the surrounding unmodified ground by adsorbing strongly with the improved body.
The content of potassium carbonate in the improved deterioration-reducing material is in the range of 10 to 40% by weight and the content of potassium chloride is 40% by weight or less because potassium carbonate is a crystal of inorganic ions and has high solubility in water. It shows a strong alkali of about pH 11, and potassium chloride is ionized in aqueous solution to become potassium ion (K ⁺ ) and chloride ion (CL ⁻ ). The pH of the improved body can be controlled by this strong alkaline electrolyzed water, and the improved body promotes the hydration reaction, the ionic charge is corrected according to the change of the ion concentration, and the respective adsorptive power is strengthened to accelerate the curing. That is, the mechanical strength of the improved body can be increased, heavy metals and harmful substances can be retained, and deterioration can be further reduced.
In addition, since the improved body deterioration reducing material contains 15% by weight or less of an ammonium salt, when the improved body deterioration reducing material is added to the cement-based improving material to obtain an improved body, the alkalinity of the improved body is similar to that of sodium carbonate. To prevent the mechanical strength from being lowered due to neutralization.

  Moreover, an alkali metal compound selected from sodium silicate, sodium sulfate, potassium sulfate, calcium sulfate, calcium phosphate, magnesium sulfate, magnesium phosphate and the like can be added to the deterioration reducing material.

  In the present invention, a heavy metal fixing agent can be used in combination. In this case, the heavy metal fixing material that can be used in combination includes a chelate heavy metal fixing agent, a clay mineral heavy metal fixing agent, and a polymer compound heavy metal fixing. Agents, cementitious heavy metal fixing agents, and acidic aluminum compounds such as aluminum sulfate. These contents can be used in the range of 0 to 30% by weight together with (0009). However, since the heavy metal fixing agent is expensive, if it exceeds 30%, the running cost becomes high, which is not preferable. In any case, it may be added as long as the effects of the present invention are not impaired. In the present invention, a cement hydrate improvement material and an improved body deterioration reducing material are added with a heavy metal fixing material to form a chemically very stable cement hydrate crystal solidified body. Of heavy metals can be prevented.

The cement-based improving material used in the present invention includes ordinary portland cement, blast furnace cement type B, general soft soil, special soil, high organic soil, hexavalent chromium elution suppression, etc., cement cement, silica cement, What is called a so-called hydraulic substance such as fly ash cement and rapid hardening cement may be used, and these may be used alone or in combination of two or more. In general, the amount of cement used is 50 to 300 kg / m ³ per 1 m ^{3 of the} target ground, and the compressive strength is high with as little cement as possible, reducing deterioration of the improved body, It is desirable to obtain a solidified product that does not elute harmful substances.

On the other hand, the effects of cement-based mixed treatment improvements on the ground include elution of high alkali and heavy metals contained in the improvements solidified by hexavalent chromium or cement-based improvement materials contained in the cement-type improvement materials themselves. Two elutions of
Solidification of the heavy metals in the improved body by solidification is greatly suppressed by actions such as physical containment by densification of the matrix, formation of poorly water-soluble substances, adsorption by hydrated products, and immobilization. It has already been recognized that heavy metals such as hexavalent chromium and lead are included due to raw materials. For example, Portland cement, which is the main component of cement-based improvement materials, is made up of natural resources such as limestone, clay, and quartzite, so the main components (Ca, Si, Al, Fe) are also included. Contains trace components such as chromium (Cr). Chromium in the natural world exists in a trivalent state, and trivalent chromium in the cement raw material is partly oxidized to hexavalent chromium in the cement firing process and exists in the cement. There is a report that an average of about 10 mg / kg of hexavalent chromium is contained.
On the other hand, in the manufacturing process of cement, by utilizing its facilities and firing technology, it accepts a large amount of waste and by-products from other industries. Sludge, sludge, construction waste soil, etc. are used as raw material substitutes, wood chips, waste plastic, waste tires, etc. are used as thermal energy, and blast furnace slug, coal ash, etc. are used as mixed materials. Recently, 400 kg of waste and by-products are being used to produce 1 ton of cement.

The fixation mechanism of heavy metals such as hexavalent chromium by cement hydrate is fixed to hydrates such as ettringite (3Ca0 ・ Al ₂ O ₃・ 3CaSO ₄・ 32H ₂ 0) and monosulfate, and hydrated calcium silicate. This is due to a complex action such as surface adsorption to the substance (C—S—H) and densification of the structure by the formed hydrate filling the gap. In the case of improved cement-based mixed treatment, the formation of hydrates is hindered by the influence of clay minerals and organic components of the ground to be improved, resulting in the elution of hexavalent chromium that was not fixed by the hydrates. To do. If calcium ions that should be the main component of the hydration reaction are taken away by other reaction systems in the surrounding area, the chemical balance of the hydration reaction is lost. Therefore, by mixing the deterioration reducing material of the present invention, the improved body increases the lime content, becomes an alkaline composition, and further achieves solidification before reaching the hydration inhibitory effect by a rapid hydration reaction. By promoting the hydration reaction of lime aluminate hydrate and increasing the production of ettringite, these bases reduce the deterioration of the improved body, fix harmful substances including heavy metals, and do not elute To do.

The method of reducing the deterioration of the cement-based mixed treatment improving body according to the present invention has the following configuration.
(1) The cement-based improving material generates calcium hydroxide (Ca (OH) ₂ ) in the course of its hydration reaction, and becomes alkaline. The hydroxyl group (OH ⁻ ) dissociated from (Ca (OH) ₂ ) generates a hardly soluble hydroxide precipitate with heavy metals, and precipitates and fixes in the improved body.
In the part where the improved body deteriorates, a decrease in calcium content, a decrease in pH, and a decrease in strength are observed. From this fact, the degradation mechanism of cementitious improved soil is the formation and elution of CaCl ₂ by the reaction of chlorides such as MgCl ₂ and Ca (OH) ₂ and the resulting hardening of the hardened structure of the improved soil, Ca It is conceivable that the cement hardened body becomes porous due to dissolution of (OH) ₂ . In the method and apparatus of the present invention, by adding a specific improved body deterioration reducing material, the precipitation and fixing action in the improved body is effectively performed.

(2) The cement-based improving material generates various hydrates by its hydration reaction. In the hydration reaction, cement and water react to form an insoluble cement hydrate and solidify. Cement hydration reactions are complex and change over time, and the cement clinker minerals alite, belite, aluminate and ferrite phases react with water to form hydrates and the hydration reaction proceeds. Hydrates such as ettringite and monosulfate are also formed. These hydrates have the ability to fix heavy metals by substitution solid solution or surface adsorption.
Calcium in the cement-mixed treated improvement body having a high pH is eluted from the improved body to the surrounding unmodified ground, and as a result, heavy metals such as hexavalent chromium are eluted from the cement-mixed treated improvement body to the surrounding unmodified ground. This is because the surrounding unimproved ground generally has a pH lower than that of the cement-mixed modified body, and thus is easily adsorbed on the ground.
The improved body deterioration reducing material used in the present invention does not advance this adsorption action. That is, the presence of the improved body deterioration reducing material reduces the deterioration of the periphery of the improved body, and consequently reduces the rate of adsorption of heavy metals such as hexavalent chromium on the surrounding ground.

  (3) In the improved body deterioration reducing material added to the cement-based improved material, the hydrate produced by the progress of the hydration action with the aging of the age fills the voids and densifies the hardened body structure. This densification of the structure reduces the deterioration of the periphery of the improved body and shows the effect of physically containing heavy metals.

The cement-based improvement material with the addition of the improved body deterioration reducing material reduces the deterioration of the improved body physically and chemically due to the synergistic effect of (1), (2) and (3), and against the harmful substances of heavy metals. And has a solidifying and insolubilizing effect. This improved material deterioration reducing material may be in the form of liquid or powder, but it is in the form of powder when shipped from the factory, and it is desirable from the viewpoint of transportation cost that it is transported and made liquid in the mixing tank on site. .
In the following examples, the improved body deterioration reducing material is used.

An example of the best blend of the improved body deterioration reducing material is as follows.
Sodium carbonate 20-50% by weight, specifically 27% on average
Sodium chloride 20-50% by weight, specifically 36% on average
-Potassium carbonate 10-40% by weight, specifically 27% on average
・ Potassium chloride 40 wt% or less ・ Ammonium chloride 15 wt% or less, specifically 6 wt% on average
・ Others 0-30% by weight, specifically 4% by weight on average
The reason for the above composition is as described above.

The effect by the said mixing | blending of the said improved body deterioration reducing material is demonstrated still in detail.
The main components of the sodium salt contained in the improved body deterioration reducing material are sodium carbonate and sodium chloride. The purpose of sodium carbonate is to prevent the deterioration of mechanical strength due to neutralization by promoting the alkalinity of the solidified improved body when the improved body deterioration reducing material is added to the cement-based improved material and solidified. It is a component added as. Sodium chloride is a component added for the purpose of promoting cement hydration together with sodium carbonate when the improved body deterioration reducing material is added to the cement-based improving material and solidified. Therefore, deterioration from the improved body can be reliably reduced.

  The content of sodium carbonate and sodium chloride in the improved body deterioration reducing material is in the range of 20 to 50% by weight. If the content is less than 20% by weight, the effect of adding chlorine ions and sodium ions supplied with sodium chloride and the like is improved. This is because when it exceeds 50% by weight, chlorine ions and sodium ions become excessive, and the effect of addition to the improved body reaches its peak. Therefore, the amount of sodium carbonate and sodium chloride added to the cement-based improving material is appropriately determined in consideration of the effect of addition.

  The content of potassium carbonate in the improved body deterioration reducing material is in the range of 10 to 40% by weight. If it is less than 10% by weight, the effect of adding potassium ions supplied by potassium carbonate is not exhibited in the improved body. This is because if it exceeds wt%, potassium ions become excessive and the effect of addition to the improved product reaches its peak. The reason why the content of potassium chloride is 40% by weight or less is that potassium ions are excessive when the content is 40% by weight or more, and the effect of addition to the improved product reaches its peak. Accordingly, the amount of potassium ion added to the cement-based improving material is appropriately determined in consideration of the effect of addition.

  In the improved body deterioration reducing material, when this improved body deterioration reducing material is added to a cement-based improvement material to make an improved body, the mechanical strength due to neutralization is promoted by promoting the alkalinity of the improved body in the same manner as sodium carbonate. An ammonium salt added mainly for the purpose of preventing a decrease in the pH is included. The content of this ammonium salt is preferably 15% by weight or less. The ammonium salt is preferably ammonium chloride.

The improved body deterioration reducing material is one of the best modes, and its properties are as follows.
The color tone of the improved material deterioration-reducing material exhibits a transparent color, and when dissolved, the pH is 9 to 12, an ammonia odor is exhibited, and the specific gravity is 1.20 to 1.24.
By adding the improved body deterioration reducing material to the cement-based mixed processing improved body, the uniaxial compressive strength of the improved body is increased, and the elution and diffusion of harmful substances contained in the raw material and the cement-based improved material are surely prevented, Since the deterioration of the improved body can be reduced, the environmental impact can be minimized.

  A mixing tank in which an improved body deterioration reducing material is added to the cement-based improving material to form a cement slurry liquid, a pressure feeding pipe for injecting and feeding the cement slurry liquid to the ground, and a cement slurry liquid supplied from the pressure feeding pipe It is connected to a mixing processor that stirs while injecting into the ground, and a pressure feeding pipe that injects and feeds the cement slurry liquid to the ground, and a cement slurry liquid as a cement-based improvement material in which an improved body deterioration reducing material is added and mixed is obtained. The cement slurry liquid is injected into the ground. At this time, a cement slurry liquid is poured and stirred while excavating the ground with excavating blades, and an improved body is constructed.

The mixed processing method that constructs the improved body by stirring the ground with stirring blades is the surface processing method when the surface layer of the ground is 1m to 2m, and the deep mixing method when the target is 3m to 65m. In some cases, the intermediate layer between the surface layer and the deep layer may be referred to as a shallow / middle mixed processing method. The method of improving the columnar shape is called the soil cement column method or the columnar column method. On the other hand, the soil cement column wall method, the underground continuous wall method, etc. is there.
In any of the methods, there are horizontal stirring method, vertical stirring method, and oblique stirring method, and there are a plurality of stirring shafts from a single shaft to a plurality of shafts, and in many cases, there are 8 shafts. And a high-pressure injection type, or a combination of both types. The mechanical stirring type includes a slurry system in which a slurry-like cementitious improving material is injected and stirred into the ground to form an improved body, and a powder system in which a powdery cementitious improving material is pumped to the ground and stirred and mixed. The improved body deterioration reducing material can be used in any method, reducing the deterioration of the peripheral part of the improved body constructed by these methods, and thus preventing soil contamination due to heavy metals caused by the improved body deterioration Therefore, the improved body deterioration reducing material can be used, and the elution of heavy metals in the improved body can be reduced.

  Various mechanical equipment is used for the mixing treatment method, and a general mixing treatment method, that is, a mixing treatment method in which an improved body is constructed by stirring with a stirring blade while injecting a cement-based improvement material into the ground is illustrated. 1 will be described. 4 is a mixing tank. The mixing tank 4 is supplied with cement-based improving material from the cement-based improving material hopper 1 and with water for the hydration reaction from the water supply unit hopper 2. Additives such as a slow-acting hardener are supplied from the additive hopper 3 and stirred in the mixing tank 4 by the rotary stirring blade 5 until a homogeneous cement slurry is obtained.

A cement slurry liquid mainly composed of a cement-based improving material in a homogeneous cement slurry form in the mixing tank 4 is stored in an agitator 6, and this cement slurry liquid is pumped from a grout pump 7 through a pressure feed pipe 8. The The amount of cement slurry liquid in the pressure feed pipe 8 is measured with a flow meter, and the injection pressure to the ground 14 is measured with a pressure meter.
At the time of injecting the cement slurry liquid, the cement slurry liquid is pumped to the stirring shaft 10 of the mixing processor 9 and injected into the ground 14 from the discharge hole 13 at the tip of the stirring shaft 10. At this time, the excavation blade 12 and the stirring blade 11 are provided at the tip of the stirring shaft 10 rotated by the drive unit of the mixing processor 9, and the ground 14 is excavated downward by the excavation blade 12 so that the cement slurry liquid is mixed. The ground 14 is stirred with the stirring blade 11. After the cement slurry liquid is injected, as the material ages, the hydration action proceeds in the ground 14 and the improved body 26 is formed.
The cement slurry liquid from the discharge hole 13 may be injected when the ground 14 is excavated downward, or may be injected when the stirring shaft 10 is raised. You may make it inject | pour both at the time of the fall and the rise. The stirring shaft 10 may be a single shaft or two or more shafts.

  The improved body deterioration reducing material 17 used in the method of the present invention is supplied from the improved body deterioration reducing material mixing tank 21 into which the improved body deterioration reducing material 17 is mixed in a liquid state to the mixing tank 4 by the supply pump 23. And stirred.

  The improved body deterioration reducing material 17 is made of a material mainly composed of a metal salt other than heavy metals. As described above, the improved body deterioration reducing material 17 is made into a cement slurry in the mixing tank 4 and injected into the ground 14. There is also a method of charging the mixing tank 4 after transportation. However, the mixing condition in which the raw material does not precipitate at the time of production, transportation, and use is that the improved body deterioration reducing material is 0.25% by weight or less with respect to water 1, so that the improved body deterioration reducing material is handled in a liquid state. However, it is possible to significantly reduce the transportation cost by manufacturing and transporting in powder form, making the improved material deterioration reducing material liquid in the field, and adding it to the cement-based improved material. The approximate transportation cost when the improved body deterioration reducing material is a powder can be reduced to a quarter of that in the liquid state.

Next, a method for producing and transporting the improved body deterioration reducing material in powder form, making the improved body deterioration reducing material in a liquid state on site, and adding and mixing it with the cement-based improving material will be described.
In FIG. 1, the improved body deterioration reducing material that has been transported in the form of powder is stored in the hopper 16 from the inlet 15, and the stored improved body deterioration reducing material 17 is put into the mixing tank 21 from the drop inlet 18. . The improved material deterioration reducing material takes a few minutes to dissolve completely in water and becomes a complete slurry, and tends to be dumpling when trying to dissolve in water all at once. It is extremely difficult to further dissolve the improved material deterioration reducing material.
Therefore, in the present invention, the improved body deterioration reducing material must be gradually fed into the mixed layer by a specified amount from the drop inlet 18. As the method, the introduced improved body deterioration reducing material 17 is uniformly sprayed to the mixing tank 21 by the feeder 19 and mixed by the stirring mechanism 20 by the rotation of the motor 22 together with the water 25 supplied from the pump 24. .
In order for the raw materials of the improved body deterioration reducing material 17 to be sufficiently mixed by mixing, for example, the following properties are used.
Material name Particle diameter μm Specific gravity (density) Solubility in water%
Sodium carbonate 20-200 1.0-1.3 21.0 (20 ° C)
Sodium chloride 150-600 2.16 26.4 (20 ° C)
Potassium carbonate 500-1000 2.43 52.6 (20 ° C)
Potassium chloride 5-100 1.98 34.2 (20 ° C)
Ammonium chloride 30-600 1.53 28.3 (20 ° C)
When the particle size of the improved body deterioration reducing material is larger than 1000 μm, it takes time to dissolve, and when the particle size is smaller than 5 μm, it is likely to be scattered and difficult to handle. The improved body deterioration reducing material is made of a material containing at least sodium carbonate, sodium chloride, potassium carbonate, potassium chloride, and ammonium chloride. These raw material components are all powders, and the particle size of the powder is 5 μm to 1000 μm. It is characterized by being. Depending on the case, when searching for an inexpensive material in the future, a flaky material having a particle diameter of about 1 to 10 mm may be targeted.
Further, the improved body deterioration reducing material 17 sufficiently mixed by the mixing tank 21 is pumped to the mixing tank 4 by the supply pump 23, and the cement slurry liquid thus obtained is stirred and mixed while being poured into the ground. This is a method for reducing the deterioration of the improved cement-based mixed treatment.

In the mixing treatment method as described above, the improved body deterioration reducing material 17 is introduced into the mixing tank 4 from the mixing tank 21, the cement-based improving material from the cement-based improving material hopper 1, and the water from the water supply unit hopper 2. Are stirred and mixed together.
The addition amount of the improved body deterioration reducing material 17 is in the range of 0.3 to 5% by weight, preferably 0.5 to 3% by weight, based on the properties of the soil to be improved in the mixed treatment method. Set in.
The amount of the improved body deterioration reducing material 17 added to the cement-based improving material is appropriately determined in consideration of the effect of addition. For example, if the soil to be improved shows a property with a high content of heavy metals, increase the proportion of the improved material deterioration reducing material to the cement-based improvement material, and if it shows a property with a low content, the cement-based improvement material Reduce the addition ratio of the improved body deterioration reducing material.
In addition, as described above, the strength of the improved body is extremely important for reducing the deterioration of the improved body. In order to obtain this strength, generally, according to the property of the ground per 1 m ^{3 of the} soil to be improved, Depending on the target strength, the addition amount of the cement-based improving material is 50 to 300 kg / m ³ . Generally, the addition amount in the case of cohesive soil is averagely 80~180kg / ^{m 3} relatively small, in the case of sandy soils 150~250kg / ^{m 3,} in the case of organic soil 200 It is about ~ 300 kg / m ³ . In the case of a columnar column method used for residential ground, it is common to add 250 to 300 kg / m ³ as viewed from the safety side.
Therefore, depending on the amount of cementitious improvement material added to the soil to be improved, the addition rate of the improved body deterioration reducing material 17 is increased when the addition amount of the cementitious improvement material is small, and is decreased when the addition amount is large. It is necessary to adjust so that the optimal improvement body deterioration reducing material is added, and this makes it possible to reduce deterioration of the improvement body as much as possible.

An example of the blend of the improved body deterioration reducing material is as follows.
Sodium carbonate 20-50% by weight, specifically 27% on average
Sodium chloride 20-50% by weight, specifically 36% on average
-Potassium carbonate 10-40% by weight, specifically 27% on average
・ Potassium chloride 40% or less ・ Ammonium chloride 15% or less, specifically 6% on average
・ Others 0-30% by weight, specifically 4% by weight on average
The reason for the above composition is as described above.

Next, an indoor confirmation experiment regarding the performance of the improved body deterioration reducing material 17 was performed. The improved body deterioration reducing material 17 was used as a 4-fold dilution, and the addition rate here indicates the addition rate of the dilution.
2 (a) and 2 (b) are diagrams showing the relationship between the uniaxial compressive strength of the improved body using the improved body deterioration reducing material and the material age.
As is clear from FIG. 2 (a), the results of ordinary Portland cement are as follows. The uniaxial compressive strength of the additive rate of 2% and 4% is 1.36 at the age of 28 days as compared with the case where the deterioration reducing material is not added. Double, 1.66 times. However, it is about 1.5 times at 6% or more. In addition, the uniaxial compressive strength of the addition rate of 2% at the material age of 180 days and 1 year does not change compared to the case of no addition. Thus, the uniaxial compressive strength is increased, and is about 1.7 times that of the additive-free.
As is clear from FIG. 2 (b), the results of the blast furnace cement type B show that the uniaxial compressive strength is 2%, 4%, and 6% at the age of 28 days compared to the case where the improved body deterioration reducing material is not added. Are 1.05 times, 1.20 times, and 1.35 times, respectively. However, there was no significant difference between 6% and 12%. Moreover, the strength increase by addition of the improved body deterioration reducing material is seen up to 6% even at a material age of 180 days and 1 year, and the strength is 1.5 to 1.7 times that of no addition. However, when the addition rate is 12%, the result is less than 6%.
From the test results, it was found that when normal Portland cement and blast furnace cement type B were used as the improvement material, the uniaxial compressive strength was increased by adding the improved body deterioration reducing material as compared with the case of no addition. Moreover, although the intensity | strength increased corresponding to an addition rate, the tendency which reached the peak was seen when the addition rate was 6% or more. This suggests that there is an applicable range in the addition rate of the improved body deterioration reducing material, and the optimum addition rate is about 4% to 6%, 1 to 1.5 in terms of powder. % By weight was estimated.

FIG. 3 shows the relationship between the added amount at the age of 7 days and the total chromium (T-Cr) and hexavalent chromium elution amount when the mixed treatment method is applied using the improved material deterioration reducing material of the present invention. FIG.
As can be seen from FIG. 3, the changes in the total chromium and hexavalent chromium elution amounts due to the addition of the improved body deterioration reducing material are the same for the cement added amount of 100 kg / m ³ and 200 kg / m ³ . A decrease in the amount of elution was observed in response to an increase in the addition rate. The improved body deterioration reducing material can be said to be effective even at an addition rate of 2%, but 4% resulted in a smaller amount of elution.

FIG. 4 shows the relationship between the amount of addition and the amount of deterioration at the age of 180 days when the mixed treatment method is applied using the improved body deterioration reducing material of the present invention. In the experiment, Kawasaki Port and Tokyo Port cohesive soil were used as samples, ordinary Portland cement and Blast Furnace Cement B were used as cement, the amount of cement added was 70 kg / m ³ , and the amount of improved body deterioration reducing material was 0. Experiments were performed at 3, 6%. As is clear from the results of FIG. 4, the effects of the 3% and 6% deterioration reducing materials are clearly seen compared to the case of no addition.

  INDUSTRIAL APPLICABILITY The present invention can be used in a mixed processing method for constructing a cement-based mixed treatment improved body by injecting and mixing a cement-based improving material into the ground, and reducing the deterioration of the improved body to contaminate the ground with heavy metals on the surrounding ground. As an environmentally friendly construction method, it has excellent effects.

It is explanatory drawing which shows the equipment which inject | pours the improvement body deterioration reducing material in a liquid state to a cement slurry mixing tank in the mixing treatment method which constructs an improvement body by stirring with a stirring blade, injecting a cement-type improvement material into the ground. It is a characteristic view showing the relation between the uniaxial compressive strength and the age of the improved body using the improved body deterioration reducing material, (a) shows an example of ordinary Portland cement, (b) is an example of blast furnace cement B type Indicates. It is a characteristic view which shows the relationship between the addition amount in the age of 7 days, and the elution amount of total chromium and hexavalent chromium at the time of constructing a mixed processing method using the improved body deterioration reducing material of this invention. It is a characteristic view which shows the relationship between the addition amount and deterioration amount in the age of 180 days at the time of constructing a mixed-treatment method using the improved body deterioration reducing material of this invention. It is a conceptual diagram of the method of reducing the elution of heavy metals in an improved body.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cement system improvement material hopper, 2 ... Water supply part hopper, 3 ... Additive hopper, 4 ... Mixing tank, 5 ... Rotary stirring blade, 6 ... Agitator, 7 ... Grout pump, 8 ... Pressure feed pipe, 9 ... Mixing Processing unit, 10 ... stirring shaft, 11 ... stirring blade, 12 ... excavation blade, 13 ... discharge hole, 14 ... ground, 15 ... inlet, 16 ... hopper, 17 ... improved material deterioration reducing material, 18 ... drop inlet, DESCRIPTION OF SYMBOLS 19 ... Feeder, 20 ... Agitation mechanism, 21 ... Mixing tank, 22 ... Motor, 23 ... Supply pump, 24 ... Water pump, 25 ... Water, 26 ... Improvement body, 31 ... Ground, 33 ... Improvement body periphery deterioration part.

Claims (5)

  In the mixed processing method of injecting and mixing cement-based improving material into the ground to construct a cement-based mixed processing improved body, an improved body deterioration reducing material composed mainly of a metal salt other than heavy metal is added to the cement-based improving material. A method for reducing deterioration of a cement-based mixing treatment improved body, characterized in that an improved body is constructed by additional mixing and stirring with a stirring blade while pouring into the ground.   The improved material deterioration reducing material has a sodium carbonate content of 20 to 50% by weight, a sodium chloride content of 20 to 50% by weight, a potassium carbonate content of 10 to 40% by weight, a potassium chloride content of 40% by weight or less, It is made of a powdery mixture containing at least 15% by weight or less of ammonium chloride, and an improved body deterioration reducing material blended within the above set range according to the soil properties to be improved is used. The method for reducing deterioration of a cement-based mixed treatment improved body according to claim 1.   The improved body deterioration reducing material consisting mainly of metal salts other than heavy metals is put into the mixing tank in specified amounts, and the introduced improved body deterioration reducing material is sprayed into the mixing tank by the feeder, and agitated by the rotation of the motor. The improved material deterioration reducing material mixed by the mixing tank is injected into the cement slurry mixing tank by the supply pump, and stirred together with the cement-based improving material and water, and the resulting mixed material is grounded. The method for reducing deterioration of a cement-based mixing treatment improved body according to claim 1 or 2, wherein stirring and mixing are performed while pouring.   The improved body deterioration reducing material added and mixed with the cement-based improving material is 0.3 to 5% by weight, preferably 0.5 to 5% with respect to the cement-based improving material 1 depending on the properties of the soil to be improved in the mixing treatment method. 4. The method for reducing deterioration of a cement-based mixed treatment improvement body according to claim 1, wherein the cement-type mixing treatment improvement body is set to be added within a range of 3% by weight.   Sodium carbonate content 20-50% by weight, sodium chloride content 20-50% by weight, potassium carbonate content 10-40% by weight, potassium chloride content 40% by weight or less, ammonium chloride content 15% by weight %, And all of these raw material components are powders, and the powdery particle diameter is in the range of 5 μm to 1000 μm. Within the above set range according to the soil properties to be improved A material for reducing deterioration of a cement-based mixed treatment improved body, characterized by being formulated with

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