JP2008037891A - Method for preparing soil cement slurry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preparing soil cement slurry, without reducing the utilization rate of soil formed in construction on preparing the soil cement slurry, and capable of improving the reusing ratio of used stabilizing liquid. <P>SOLUTION: This method for preparing the soil cement slurry comprises a step of preparing the soil cement slurry by mixing excavation-stabilizing liquid with a cement-based setting agent, a plasticizer, an alkali metal carbonate salt and the soil, or comprises a step of preparing the soil cement slurry by mixing the excavation-stabilizing liquid added with the alkali metal carbonate salt and/or carbon dioxide with the cement-based setting agent, plasticizer and soil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for preparing soil cement slurry, and in particular, soil improvement using soil cement slurry, construction of retaining walls and water barriers, foundation pile work, backfill work, etc. (especially backfill represented by CRM method, etc.) The present invention relates to a method for preparing a soil cement slurry in (Construction method).

  In recent years, from the viewpoint of resource recycling, a fluidization treatment method has been developed that reuses soil material generated in connection with construction work (hereinafter referred to as construction generated soil). This fluidization treatment method is used for backfilling, construction of earth retaining walls and water blocking walls, foundation pile construction, backfilling work, etc. for construction sites where compaction is difficult. It is characterized by using cement slurry. This soil cement slurry is used as mud soil having a predetermined fluidity during construction, and then hardens so as to obtain the predetermined mechanical properties required for the construction site by the solidified material mixed therein. It is adjusted processing soil.

  This soil cement slurry generally contains construction-generated soil as a main material and a solidifying material, and further contains adjusted muddy water and other admixtures as necessary. As the main material, various construction-generated soils (simply referred to as generated soil) such as sandy soil, silt, and cohesive soil can be used. In particular, if the construction-generated soil, which is the main material, contains mainly sandy soil, mud containing adjusted fine gravity containing fine particles such as clay and silt is added to the construction-generated soil as necessary. Can also be used. Thereby, the construction generated soil as the main material can have appropriate fluidity, and material separation during backfilling and filling can be suitably prevented.

  Further, a solidifying material is used to solidify the soil cement slurry cast around the structure later. The strength of the soil cement slurry after solidification can be adjusted by the type and amount of the solidified material. Generally, conventional solidified materials for soft ground improvement such as cement, cement-based solidified material and lime-based solidified material are used. Has been. Furthermore, an admixture can be used for adjusting the fluidity and setting time of the soil cement slurry as required. In particular, when the construction-generated soil, which is the main material, mainly contains silt and viscous soil, a fluidizing agent or a retarder may be used.

JP-A-8-12403 Japanese Patent Laid-Open No. 2003-041243 JP 2000-169209 A

However, in the fluidization processing method using the existing soil cement slurry described above, the following problems may occur.
(1) When the generated soil used is silt or viscous soil, the amount of generated soil to be used should be limited to be small in order to meet the high self-leveling property (high fluidity) and strength required for the soil cement slurry. As a result, the reuse rate (recycling rate) of the generated soil is significantly reduced.
(2) Unlike the method of injecting cement milk directly into the ground, mixing the ground and cement milk to create a soil cement slurry, and creating a water barrier or earth retaining wall, the fluidization method is once It was generated by excavation after excavation using a fluid called a drilling stabilizer (also referred to as a stabilizer), which was prepared by dissolving and suspending bentonite, carboxymethylcellulose (CMC), a dispersant, etc. in water and adjusting to predetermined characteristics. This is a method of preparing soil cement slurry using the generated soil and returning it to the excavation hole. For this reason, in the fluidization treatment method, a used stable liquid is always generated, and the treatment becomes a problem.

  In order to solve the problem (1), an oxycarboxylate described in Patent Document 1 (Japanese Patent Laid-Open No. 8-12403) and a high-performance AE water reducing agent and a fluidizing agent typified by naphthalenesulfonic acid are used in combination. The method is used. However, this method does not exhibit sufficient effect on fine earth and sand mainly composed of silt and clay.

  Moreover, at present, there is almost no method for solving the problem (2). On the other hand, in order to reuse the used stabilizer, it has been attempted to use the used stabilizer for preparing the soil cement slurry. However, as mentioned above, since the stabilizer generally contains active clay such as bentonite and polymers, gelation occurs when the stabilizer comes into contact with a solidifying agent such as cement, which significantly impedes the fluidity of the soil cement slurry. There is a case. In particular, when the above problems (1) and (2) occur in combination, the fluidity of the soil cement slurry is further deteriorated by the viscous soil and the stabilizing liquid, and as a result, the utilization rate of the generated soil is significantly reduced. It may not be possible to reuse the used stabilizer.

  For this reason, the reuse of the used stabilizer for the preparation of the soil cement slurry is limited to the case where the generated soil is sand. That is, since sand does not act in the direction of increasing the viscosity of the soil cement slurry, sand may settle in the soil cement slurry, and the upper and lower parts of the wall may become uneven when solidified, resulting in strength variations. . By using a stabilizing liquid, viscosity can be increased by gelation, and variation in strength can be prevented.

  In view of the above, the present invention provides a method for preparing a soil cement slurry that can improve the reuse rate of a used stabilizing liquid without reducing the utilization rate of construction generated soil during the preparation of the soil cement slurry. For the purpose.

  According to one aspect of the present invention, there is provided a method for preparing a soil cement slurry, which includes a step of preparing a soil cement slurry by mixing a drilling stabilizer, a cement-based solidifying material, a fluidizing agent, an alkali metal carbonate, and soil. Provided. According to another aspect of the present invention, a step of preparing a soil cement slurry by mixing an excavation stabilizing liquid to which an alkali metal carbonate and / or carbon dioxide is added, a cement-based solidifying material, a fluidizing agent, and soil is mixed. A method for preparing a soil cement slurry is provided.

  As will be described in detail below, according to the present invention, the soil cement slurry can improve the reuse rate of the used stable liquid without reducing the utilization rate of the soil generated during the preparation of the soil cement slurry. A method of preparation is provided.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments described below.

  As a result of intensive studies to solve the above problems, the present inventors can use a used stabilizer as a solidifying agent solution by using an alkali metal carbonate or the like in the preparation of a soil cement slurry. In addition, even when the generated soil to be used is silt clay or clay soil, it has been found that the fluidity of the soil cement slurry can be improved without lowering the utilization rate, and the present invention is completed. It came.

  So far, fluidizing agents such as oxycarboxylate, naphthalene sulfonic acid, polycarboxylic acid compound, lignin sulfonate have been used as cement admixtures added to fluidize soil cement slurries. . (Concrete construction handbook listed.)

However, these additives effectively act as a fluidizing agent for soil cement slurries for sandy ground, but the effects are extremely poor when used for viscous soils. The present inventors thought that such a decrease in the effect of the fluidizing agent was due to the following causes.
(1) Unlike the sandy soil, the clay soil contained in the soil cement slurry is dispersed and hydrated in the slurry to make it finer to the colloidal particle size, and the various fluidizing agents added to the clay particle surface. To be absorbed and consumed.
(2) Polyvalent metal ions represented by calcium and magnesium ions in the liquid phase of cement milk used to prepare soil cement slurry react with various fluidizing agents to form insoluble or soluble salts. In order to reduce the effect of the additive.

  When the used stabilizer is used for the preparation of the soil cement slurry, gelation occurs due to the influence of active clay, polymers and the like in the stabilizer, which further complicates the problem.

  In the present invention, the inventors have studied the cause (2), and have been made based on the obtained knowledge.

As described in detail in the Examples section, the total concentration of calcium ions and magnesium ions in the cement milk liquid phase (also referred to as total hardness or polyvalent metal ion concentration) is almost the same regardless of the cement / water ratio. It is almost constant. This is considered to be due to the fact that the calcium ions in the cement milk liquid phase are in the equilibrium state shown in the following formula.
Ca (OH) ₂ ⇔ Ca ²⁺ + 2OH ⁻

  The total hardness can be reduced by adding alkali metal carbonate or the like to cement milk in such a state. In particular, the present inventors have found that the total hardness can be reduced to a level of 50 ppm by adding about 3.0 parts by weight of alkali metal carbonate per 100 parts by weight of water contained in the cement slurry. It was done. That is, the technical scope of the present invention should not be bound by theory, but by using an alkali metal carbonate or the like, it is possible to reduce polyvalent metal ions that are thought to reduce the effect of the fluidizing agent. Can do. Based on the above knowledge, the present invention reduces the polyvalent metal ion concentration in the liquid phase part by using alkali metal carbonate or the like, thereby dramatically improving the effect of the fluidizing agent. .

  In addition, the present inventors have found that the total hardness in the liquid phase can be maintained at a low value over a long period of time by using an alkali metal carbonate or the like. That is, the improvement of the effect of the fluidizing agent by using an alkali metal carbonate or the like is sustained for a long time.

  That is, according to one aspect of the present invention, the preparation of a soil cement slurry comprising a step of preparing a soil cement slurry by mixing a drilling stabilizer, a cement-based solidifying agent, a fluidizing agent, an alkali metal carbonate, and soil. A method is provided. According to another aspect of the present invention, a step of preparing a soil cement slurry by mixing an excavation stabilizing liquid to which an alkali metal carbonate and / or carbon dioxide is added, a cement-based solidifying material, a fluidizing agent, and soil is mixed. A method for preparing a soil cement slurry is provided.

  Usually, a soil cement slurry is prepared by mixing cement milk and soil prepared in advance. That is, the step of preparing the soil cement slurry is a step of mixing the spent stabilizer, the cement-based solidifying agent, the fluidizing agent, and the alkali metal carbonate to prepare cement milk, or the alkali metal A step of mixing a drilling stabilizing liquid to which carbonate and / or carbon dioxide is added, the cement-based solidifying material, and the fluidizing agent to prepare cement milk; and mixing the cement milk and the soil; Preferably preparing a cement slurry.

  In the present invention, the cement-based solidifying material may be any commercially available cement-based solidifying material such as ordinary Portland cement and blast furnace cement B type, and is not particularly limited. The amount of the cement-based solidifying material used is preferably 80 to 500% in terms of the weight ratio of the cement-based solidifying material to the moisture contained in the cement slurry (cement / water ratio, also referred to as W / C%). More preferably, it is 300%. In addition, the value of W / C of cement milk is different depending on the type of target soil, and it is common to adopt a small value for sand ground and a high value for clay ground. This is to maintain the fluidity of the finished soil cement slurry appropriately.

  Further, as described above, the fluidizing agent may be a commercially available fluidizing agent such as oxycarboxylate, naphthalene sulfonic acid, polycarboxylic acid compound, lignin sulfonate, humate, and the like. Is not to be done. Moreover, a water reducing agent can also be used as a fluidizing agent. The present invention can be suitably applied to a fluidizing agent other than a fluidizing agent other than a low molecular weight polymer having a carboxylic acid or a monovalent salt thereof as a main constituent monomer unit. Examples of such fluidizing agents include humates, lignin sulfonates, condensed phosphates and phosphates. More specifically, examples of such fluidizing agents include sodium humate, potassium humate, ammonium humate, sodium lignin sulfonate, potassium lignin sulfonate, ammonium lignin sulfonate, sodium phosphate, potassium phosphate, phosphoric acid. Examples include sodium hydrogen, potassium hydrogen phosphate, and sodium, potassium, or ammonium salts of pyrophosphoric acid, tripolyphosphoric acid, tetraphosphoric acid, polyphosphoric acid, and metaphosphoric acid.

  The fluidizing agent can be used in a powder state or in a solution state. The amount of the fluidizing agent used can be appropriately set according to the type of fluidizing agent and other components used, the purpose of using the soil cement slurry, and the like.

  In the present invention, the alkali metal carbonate is preferably at least one selected from the group consisting of sodium carbonate, sodium hydrogen carbonate, potassium carbonate and potassium hydrogen carbonate. That is, as the alkali metal carbonate, any of sodium carbonate, sodium hydrogen carbonate, potassium carbonate, and potassium hydrogen carbonate may be used, or two or more of these may be used. In particular, the alkali metal carbonate is preferably sodium carbonate and / or sodium hydrogen carbonate because it is inexpensive and economically effective. The alkali metal carbonate can be used in a powder state or in a solution state.

  Further, the addition amount of the alkali metal carbonate is preferably 0.1 parts by weight or more, more preferably 1.0 part by weight or more per 100 parts by weight of water contained in the cement slurry, and 2.5 weights. More preferably, it is at least part. As described in detail in the Examples section, this can dramatically reduce the polyvalent metal ion concentration in the liquid phase portion of the cement milk used to prepare the soil cement slurry. Furthermore, this effectively prevents the polyvalent metal ion from reacting with the fluidizing agent and forming an insoluble or soluble salt, thereby reducing the effect of the fluidizing agent, and the effect of the fluidizing agent is greatly improved. Can be improved. Moreover, it is preferable that the addition amount of an alkali metal carbonate is 5.0 weight part or less per 100 weight part of water | moisture content contained in a cement slurry, and it is more preferable that it is 3.5 weight part or less. This is because when the amount of alkali metal carbonate added is excessive, the strength of the cement solidified body may be reduced.

  The excavation stabilizing liquid can be used as part or all of the dissolved water used for the preparation of the soil cement slurry. As described above, the excavation stabilizing liquid is a liquid for stabilizing a wall surface such as a hole obtained by excavation and preventing collapse, and is widely used in this technical field. In the present invention, it is not particularly limited, and any excavation stabilizing liquid can be used. For example, examples of the excavation stabilizing liquid are disclosed in JP-A-60-133304, JP-A-8-157820, JP-A-2000-212551, JP-A-2000-212552, JP-A-2001-31959, JP-A-2001-55565, JP-A-2001-64636, JP-A-2001-64637, and JP-A-2003-41243 (Patent Document 2).

  More specifically, the excavation stabilizing liquid preferably contains a clay mineral. The clay mineral is blended in order to impart basic viscosity characteristics and drainage to the excavation stabilizing liquid. Examples of the clay mineral include sepiolite, attapulgite, entry gite, bentonite, kaolin clay, montmorillonite, cristobalite, eclite, saponite, beidellite, zeolite, palygoscarite, mica, and combinations thereof. In particular, as the clay mineral, sepiolite, attapulgite, entry gite, bentonite, kaolin clay, montmorillonite, cristobalite and the like are preferable, and bentonite, kaolin clay, and montmorillonite are particularly preferable. This is because the drainage is high.

  Moreover, it is preferable that a drilling stabilization liquid contains a thickener. Examples of the thickener include carboxymethyl cellulose (CMC) and alkali thickening emulsion polymer (see Patent Document 2).

  Moreover, it is preferable that a drilling stabilization liquid contains a dispersing agent. Examples of the dispersant include poly (meth) acrylate, lignin sulfonate, hexametaphosphate, and tripolyphosphate. In particular, an acrylic acid-based dispersant is preferable as the dispersant.

  More specifically, it is preferable that the excavation stabilizer contains bentonite, carboxymethylcellulose (CMC), and an acrylic dispersant as used in general continuous wall construction work and pile work. Moreover, it is preferable that a drilling stabilization liquid contains a bentonite, an alkali thickening emulsion polymer, and an acrylic acid type dispersing agent. According to such excavation stabilizing liquid, it is possible to reduce the addition amount of various fluidizing agents necessary for improving the generated soil utilization rate and adjusting the fluidity. This is considered to be because the alkali-thickened emulsion polymer constituting the stabilizing solution is excellent in cement resistance and reduces the degree of gelation when a cement-based solidifying agent is added. Such a drilling stabilizer is available from Ternite Co., Ltd. as a pastel 8 stabilizer.

  In addition, used excavation stabilization liquid can be used as the excavation stabilization liquid. Used drilling stabilizers include those that have been treated with baking soda, soda ash and / or carbon dioxide when the drilling stabilizer is contaminated with cement or contaminated with excavated sediment, and new stable stabilizers. There are a stable liquid generated when adjusting the excavation stability liquid contaminated by adding the liquid and water, and an unadjusted stability liquid, and any of them can be used in the present invention. Moreover, the used excavation stabilizing liquid which is severely contaminated and cannot be adjusted and is directly discarded when the present invention is not applied can be reused by applying the present invention.

  In particular, an excavation stabilizing liquid to which alkali metal carbonate and / or carbon dioxide gas is added can be used as the stabilizing liquid. As described above, the excavation stabilizing liquid contaminated with cement can be adjusted and reused by adding alkali metal carbonates such as baking soda and soda ash or carbon dioxide. In the present invention, the excavation stabilization liquid to which alkali metal carbonate and / or carbon dioxide gas is added includes these adjusted stabilization liquids. By using such excavation stabilizing liquid, it may be possible to omit the addition of further alkali metal carbonate during the preparation of the soil cement slurry.

  Specifically, when using an excavation stabilizing liquid to which alkali metal carbonate and / or carbon dioxide gas has been added and further adding an alkali metal carbonate during the preparation of the soil cement slurry, the alkali metal carbonate during the preparation of the soil cement slurry The addition amount is preferably 0.0 to 3.0 parts by weight, more preferably 0.05 to 1.5 parts by weight, per 100 parts by weight of water contained in the cement slurry.

  Moreover, in order to maintain the properties of the soil cement slurry such as fluidity in an optimal state, it is preferable to adjust the amount of water, cement, and soil contained in the finished soil cement slurry. When using a used stabilizer, the amount of cement-based solidifying agent and the amount of soil to be added may be determined in consideration of the amount of water contained in the stabilizer, bentonite, etc., and the amount of soil mixed during drilling. it can. Furthermore, when the amount of the used stabilizing liquid used is insufficient, the desired amount of water, the amount of cementitious solidifying agent, and the amount of soil can be determined by adding the insufficient amount of water. As described above, the amount of the stabilizing liquid to be used can be appropriately set by those skilled in the art depending on the properties of the desired soil cement slurry and other conditions.

  The order of mixing the excavation stabilizing liquid, the cement-based solidifying material, the alkali metal carbonate, and the fluidizing agent is not particularly limited. In particular, it is preferable to add a drilling stabilizing liquid, an alkali metal carbonate, and a fluidizing agent in advance, and then mix the obtained solution and the cement-based solidifying material. In general, when determining the blending composition of the soil cement slurry, a blending test is performed in advance, and the amounts of the excavation stabilizer, cement-based solidifying material, alkali metal carbonate and fluidizing agent to be used are determined from the results. For this reason, in order to improve workability | operativity, the additive which mixed the alkali metal carbonate and the fluidizing agent previously in the state of the powder or the solution can be prepared, and this can be used in the construction work. More specifically, for example, in a compounding test, a predetermined amount of a used stabilizing solution was placed in a container of a soil mixer, an alkali metal carbonate and a fluidizing agent were added while stirring, and the solution was completely dissolved visually. After confirming, it is preferable to add cement. The cement milk can be completed by confirming that the cement is dispersed and suspended. Usually, preparation of cement milk requires about 5 minutes from the addition of cement.

  In the present invention, any soil such as sandy soil and viscous soil can be used. In particular, the present invention can be suitably applied to viscous soils such as silt, clay, and silt clay. Regarding the relationship between the cement milk and the soil to be used, it is preferable to use the soil so that the slump flow value is 160 mm to 300 mm. In general, the soil utilization rate (the volume ratio of the soil used for the cement milk slurry to the excavated soil) can be 30 to 70%, but the higher the better.

  In addition, it is preferable to perform the step which mixes cement milk and soil and prepares a soil cement slurry immediately after preparing cement milk. More specifically, for example, in a blending test, a predetermined amount of soil is added to cement milk, and when the mixture is sufficiently mixed with cement milk, the soil cement slurry can be completed. Usually, mixing of cement milk and soil takes about 5 minutes from the addition of soil to cement milk.

  In the step of preparing the cement milk, the polyvalent metal ion concentration in the liquid phase portion of the cement milk is preferably as close to 0 ppm as possible, particularly preferably 200 ppm or less, and 100 ppm or less. More preferably. Thereby, it is possible to suitably prevent the polyvalent metal ion from reacting with various fluidizing agents to form an insoluble or soluble salt, thereby reducing the effect of the fluidizing agent.

In this specification, the polyvalent metal ion concentration (total hardness) is the total amount of calcium ions and magnesium ions in the liquid phase part of the soil cement slurry converted to the equivalent amount of calcium carbonate (CaCO ₃ ). The concentration is intended to be expressed in ppm. The polyvalent metal ion concentration (total hardness) can be determined using a simple analytical instrument such as a commercially available pack test kit. The liquid phase portion of cement milk can be obtained by setting cement milk in a pressure dehydrator and dehydrating it.

  In addition, in the technology for building soil cement, a technology that uses a low molecular weight polycarboxylic acid and an alkali metal carbonate to reduce the injection rate and improve the utilization rate of the generated soil is disclosed (patent) Document 3, JP 2000-169209 A). However, the document does not describe or suggest the use of a drilling stabilizer when preparing a soil cement slurry. On the other hand, the present invention makes it possible to prepare a soil cement slurry using a drilling stabilizing liquid by adding an alkali metal carbonate or carbon dioxide gas, thereby reusing the drilling stabilizing liquid. be able to.

  Furthermore, the technique described in Patent Document 3 has a low molecular weight polycarboxylic acid having a defect that gives fluidity to a soil cement slurry for a long time but causes a decrease in strength, and a defect that has a strength maintaining effect but cannot maintain fluidity. A fluidizing agent and a fluidizing method in combination with an alkali metal carbonate. That is, in this technique, an alkali metal carbonate is used for the purpose of complementing the drawback of lowering the soil cement strength of the low molecular weight polycarboxylic acid. On the other hand, in the present invention, as described above, alkali metal carbonate is used to adjust the total hardness in the liquid phase for the purpose of improving the effect of the fluidizing agent added to the soil cement slurry. Thus, the alkali metal carbonate in the art is completely different from the present invention in the method of use. Moreover, in the said technique, it is effective only about a specific fluidizing agent (low molecular weight polycarboxylic acid). On the other hand, the present invention is not only effective for limited fluidizing agents, but is effective for any fluidizing agent.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the examples described below.

[Experimental Example 1]
The relationship between the total hardness (polyvalent metal ion concentration) in the cement milk liquid phase and the cement / water ratio was examined as follows.
(1) Take a predetermined amount of tap water in a container, add cement to a desired cement water ratio while stirring at 300 rpm with a laboratory stirrer, stir for 2 minutes, and then use filter paper: TOYO-No2 and funnel Filtered.
(2) 1 ml of filtered water was collected with a whole pipette, about 25 ml of distilled water was added, and 2 drops of BT indicator were added while stirring with a magnetic stirrer.
(3) Total hardness was measured with 0.01 mol of EDTA.

Table 1 shows the relationship between the total hardness in the cement milk liquid phase and the cement water / ratio. As shown in Table 1, the total hardness in the cement milk liquid phase was almost constant regardless of the cement water ratio. As described above, this is considered to be due to the fact that the calcium ions in the cement milk liquid phase are in the equilibrium state shown in the following formula.
Ca (OH) ₂ ⇔ Ca ²⁺ + 2OH ^- formula

[Experiment 2]
The relationship between the amount of alkali metal carbonate added to cement milk and the total hardness in the cement milk liquid phase was examined as follows.
(1) A 300 ml portion of tap water was taken, a predetermined amount (0 to 27 g) of carbonate was added while stirring at 300 rpm with a laboratory stirrer, and stirring was continued for 2 minutes.
(2) 300 g of cement was added, stirred for 2 minutes with a laboratory mixer, and then naturally filtered using filter paper: TOYO-No2 and a funnel.
(3) 1 ml of filtered water was collected with a whole pipette, about 25 ml of distilled water was added, and 2 drops of BT indicator were added while stirring with a magnetic stirrer.
(4) Total hardness was measured with 0.01 mol of EDTA.

  Table 2 and FIGS. 1 and 2 show the relationship between the amount of alkali metal carbonate added to cement milk and the total hardness in the cement milk liquid phase. Surprisingly, as shown in Table 2 and FIGS. 1 and 2, the total hardness was reduced to the 50 ppm level by adding about 3.0 parts by weight of alkali metal carbonate per 100 parts by weight of dissolved water.

[Experiment 3]
The relationship between the time after addition of the alkali metal carbonate and the total hardness was examined as follows.
(1) Taking 300 ml of tap water and stirring at 300 rpm with a laboratory stirrer, 15 g of carbonate was added and stirring was continued for 2 minutes.
(2) 300 g of cement was added and stirred for 2, 10, 20, 30, 60, 120 minutes with a lab mixer.
(3) The cement milk sample at each stirring time was naturally filtered using filter paper: TOYO-No2 and a funnel.
(4) Total hardness was measured with 0.01 mol of EDTA.

  Table 3 shows the relationship between the time after addition of the alkali metal carbonate and the total hardness. As shown in Table 3, when the alkali metal carbonate is added, the total hardness can be kept low at about 1/5 to 1/14 in the case of no addition over a long period of time.

[Experimental Example 4]
The relationship between the amount of alkali metal carbonate added and the consistency and uniaxial compressive strength was examined as follows.
(1) 700 ml of tap water was taken, a predetermined amount (0, 7, 21, 70, 125, 175 g) of carbonate was added while stirring at 300 rpm with a laboratory stirrer, and stirring was continued for 5 minutes.
(2) 930 g of cement was taken in a Hobart mixer container, and seawater was added as in (1) above.
(3) The mixture was stirred for 2 minutes with a Hobart mixer.
(4) The TF value was measured.
(5) Three EP mold specimens were prepared and wet-cured for 7 days.
(6) Uniaxial compression strength (q7) after 7 days was measured with a uniaxial compression measuring instrument.

  Tables 4 and 5 show the relationship between the addition amount of alkali metal carbonate, consistency, and uniaxial compressive strength. As shown in Tables 4 and 5, the table flow (slump flow) value decreased as the amount of alkali metal carbonate added increased, and 5.0 parts by weight of carbonate added per 100 parts by weight of dissolved water It can be seen that the strength of the solidified body is reduced.

[Examples 1 to 10]
The influence of the alkali metal carbonate on the fluidity, slump flow value and uniaxial compressive strength of the soil cement slurry was tested under the following test conditions.

[Alkali metal carbonate]
・ Sodium bicarbonate Kanto Chemical Co., Ltd. Reagent ・ Sodium carbonate Kanto Chemical Co., Ltd. Reagent [Fluidizer]
・ Polycarboxylic acid Na salt Ternite product (Product name: Terfro Soil)
-Humic acid sodium salt Ternite product (Product name: Renalk)
[Cement-based solidification material]
・ Blast furnace type B cement Taiheiyo Cement Co., Ltd. Saitama factory product [simulated soil]
・ Cohesive soil: 3.0 parts by weight of mountain clay (product name “Sumi clay” manufactured by Sumitomo Osaka Cement) and 1.0 part by weight of bentonite (product name “Haruna” manufactured by Hojun Co., Ltd.) Adjusted to a water content ratio of 25.0% [Excavation Stabilizer]
・ CMC Stabilizer ・ Pastel 8 Stabilizer ・ Used CMC Stabilizer 1 generated during continuous wall construction on site
・ Used CMC stabilizer 2 generated during continuous wall construction on site
・ Used pastel 8 stabilization liquid generated during continuous wall construction

Table 6 shows the properties of the simulated soil.

Table 7 shows the composition of CMC stabilizer and pastel 8 stabilizer.

  Further, as the used CMC stabilizer 1, CMC stabilizer 2 and pastel 8 stabilizer generated in the field continuous wall construction, the stabilizer obtained as follows was used. The used CMC stabilizing liquids 1 and 2 are surplus stabilizing liquids generated when the used stabilizing liquids at the time of excavation of Ueno ground were prepared, and the stabilizing liquids that were left in the collection tank for several weeks were used. The used stabilizer was adjusted as follows. The used pastel 8 stabilizing liquid is an excess stabilizing liquid generated when adjusting the used stabilizing liquid during excavation of the Namba ground. The used pastel 8 stabilizing solution is obtained by blowing a large amount of carbon dioxide into the stabilizing solution as a measure against cement contamination. Specifically, the used stabilizer was adjusted as follows.

Table 8 shows the properties of each stabilizing solution. The properties of the stable liquid were measured in accordance with the methods described in the Continuous Wall Construction Method Design and Construction Handbook (edited by Japan Construction Mechanization Association) and API RP13B-1 Recommended Practice Standard Procedure for Field Testing Water-Based Drilling Fluids.

[Test procedure]
1. A predetermined amount of the stabilizer was weighed into a soil mixer.
2. While stirring, a predetermined amount of alkali metal carbonate and fluidizing agent were added and stirred for about 3 minutes to confirm dissolution of the alkali metal carbonate and fluidizing agent.
3. When the dissolution of the alkali metal carbonate and the fluidizing agent was confirmed, cement was added and stirred for 5 minutes.
4). A predetermined amount of viscous soil was added to the finished cement milk and stirred for about 5 minutes.
5. After the clay soil was dispersed in the cement milk and became uniform, the slump flow value was measured.
6). Samples were packed in molds and stored wet and uniaxial compressive strength was measured after 28 days.

[Evaluation methods]
-Slump flow value: Conforms to JHS A 313-1992-Uniaxial compressive strength evaluation method: Conforms to JGS T 511 method

[Evaluation criteria]
-Slump flow value: 160 mm to 300 mm
(Generally, in this range, the soil cement slurry can be smoothly replaced with the excavation stabilizing liquid in the hole during the casting, and the soil cement slurry can be uniformly filled in the entire excavation hole.)
・ Uniaxial compressive strength (strength): 500 (kN / m ² ) or more (The required mechanical strength differs depending on the purpose, but in this range, the mechanical strength that can generally be required for earth retaining walls and water blocking walls. Satisfies strength.)

In Table 9, the composition of the soil cement slurry in Examples 1-5 and Comparative Examples 1-8 is shown. (Stabilizer: CMC stabilizer, alkali metal carbonate: sodium carbonate, fluidizer: polycarboxylic acid Na salt)

Table 10 shows the presence or absence of use of alkali metal carbonate and fluidizing agent and the fluidity of the soil cement slurry in various blending compositions when the CMC stabilizer is used as dissolved water.

  From the results of Examples and Comparative Examples, according to the present invention, the sludge flow value and the uniaxial compressive strength satisfy the evaluation criteria, and the stabilizer can be suitably used as dissolved water, and the soil utilization rate is hardly reduced. It can be seen that the soil cement slurry can be suitably prepared.

Table 11 shows the composition of the soil cement slurry in Examples 6 to 21 and Comparative Examples 1 and 2. (Stabilizer: CMC stabilizer, alkali metal carbonate: sodium carbonate, fluidizer: polycarboxylic acid Na salt)

Table 12 shows the amount of alkali metal carbonate and fluidizing agent added and the fluidity of the soil cement slur when the CMC stabilizer is used as dissolved water.

  From the results of Comparative Examples and Examples, the addition amount of alkali metal carbonate (sodium carbonate) is in the range of 0.4 to 1.1 parts by weight and the addition amount of fluidizing agent (polycarboxylic acid Na salt) is 0.5. To 1.1 parts by weight, the stabilizer can be used as dissolved water, and the slump flow value and uniaxial compressive strength are evaluated without substantially reducing the soil utilization. It can be seen that a soil cement slurry satisfying the above can be suitably prepared.

Table 13 shows the composition of the soil cement slurry in Examples 22 to 24 and Comparative Examples 1 and 9. (Stabilizer: CMC stabilizer, alkali metal carbonate: sodium carbonate, fluidizer: humic acid sodium salt)

Table 14 shows the amount of alkali metal carbonate and fluidizing agent (humic acid salt) added and the fluidity of the soil cement slurry when the CMC stabilizer is used as dissolved water.

  From the results of the examples, by adding an alkali metal carbonate and using humate as a fluidizing agent, the stabilizer can be suitably used as dissolved water, and without substantially reducing the soil utilization rate. It can be seen that a soil cement slurry that satisfies the evaluation criteria in terms of slump flow value and uniaxial compressive strength can be suitably prepared.

Table 15 shows the composition of the soil cement slurry in Examples 25 to 43 and Comparative Example 1. (Stabilizer: Pastel 8 stabilizer, alkali metal carbonate: sodium carbonate, fluidizer: humate)

Table 16 shows the amount of alkali metal carbonate and fluidizing agent added and the fluidity of the soil cement slurry when the pastel 8 stabilizer is used as dissolved water.

  From the results of Comparative Examples and Examples, the addition amount of alkali metal carbonate (sodium carbonate) is in the range of 0.4 to 1.1 parts by weight, and the addition amount of fluidizing agent (polycarboxylic acid Na salt) is 0. By adjusting in the range of 0.5 to 1.1 parts by weight, the stabilizer can be suitably used as dissolved water, and the slump flow value and uniaxial compressive strength can be reduced without substantially reducing the soil utilization. It turns out that the soil cement slurry which satisfies evaluation criteria can be created suitably.

Table 17 shows the composition of the soil cement slurry in Examples 44 to 53 and Comparative Examples 10 and 11. (Stabilizer: Used CMC stabilizers 1 and 2 generated in the field continuous wall construction, alkali metal carbonate: sodium carbonate or sodium bicarbonate, fluidizer: polycarboxylic acid Na salt)

Table 18 shows the addition amount of alkali metal carbonate and fluidizing agent and the fluidity of the soil cement slur when the used CMC stabilizers 1 and 2 generated in the field continuous wall construction are used as dissolved water.

  From the results of Comparative Examples and Examples, by using an alkali metal carbonate (sodium carbonate) and a fluidizing agent (polycarboxylic acid Na salt) in combination, the field-used CMC stabilizer can be suitably used as dissolved water, and It can be seen that a soil cement slurry in which the slump flow value and the uniaxial compressive strength satisfy the evaluation criteria can be suitably prepared without substantially reducing the soil utilization rate.

Table 19 shows the composition of the soil cement slurry in Examples 54 to 59 and Comparative Example 12. (Stabilizer: used pastel 8 stabilizer generated in the field continuous wall construction, alkali metal carbonate: sodium carbonate or sodium bicarbonate, fluidizer: polycarboxylate)

Table 20 shows the amount of alkali metal carbonate and fluidizing agent added and the fluidity of the soil cement slur when the used pastel 8 stabilizing solution generated in the field continuous wall construction is used as dissolved water.

  From the results of Comparative Examples and Examples, it is possible to suitably use the used pastel 8 stabilizer as dissolved water by using an alkali metal carbonate (sodium carbonate or sodium bicarbonate) and a fluidizing agent (sodium acrylate) in combination. It can be seen that a soil cement slurry having a slump flow value and a uniaxial compressive strength satisfying the evaluation criteria can be suitably prepared without substantially reducing the soil utilization rate. Further, from the results of Comparative Examples and Examples, when the used pastel 8 stabilizer was used, even when the dispersant was added alone without using the alkali metal carbonate, the soil utilization rate was hardly reduced. Thus, a soil cement slurry in which the slump flow value and the uniaxial compressive strength satisfy the evaluation criteria could be suitably prepared. This is because the pastel 8 stabilizer contains a large amount of carbonate ions by addition of alkali metal carbonate and carbon dioxide gas, and is excellent in cement resistance, so that the agglomeration during cement addition is small and the flow value can be easily controlled. It is thought that it shows.

FIG. 1 shows the relationship between the amount of alkali metal carbonate (bicarbonate) added to cement milk and the total hardness in the cement milk liquid phase. FIG. 2 shows the relationship between the amount of alkali metal carbonate (soda ash) added to cement milk and the total hardness in the cement milk liquid phase.

Claims (8)

  A method for preparing a soil cement slurry, comprising a step of preparing a soil cement slurry by mixing a drilling stabilizing liquid, a cement-based solidifying material, a fluidizing agent, an alkali metal carbonate, and soil.   A method for preparing a soil cement slurry, comprising a step of preparing a soil cement slurry by mixing an excavation stabilizing liquid to which an alkali metal carbonate and / or carbon dioxide is added, a cement-based solidifying material, a fluidizing agent, and soil.   The method according to claim 1 or 2, wherein the drilling stabilizer is a used drilling stabilizer. Preparing the soil cement slurry comprises:
Mixing the excavation stabilizing liquid, the cement-based solidifying material, the fluidizing agent and the alkali metal carbonate to prepare cement milk, or excavation stability to which the alkali metal carbonate and / or carbon dioxide gas is added Mixing a liquid, the cement-based solidifying material and the fluidizing agent to prepare cement milk;
The method according to claim 1, further comprising: mixing the cement milk and the soil to prepare a soil cement slurry.   The method according to claim 4, wherein in the step of preparing the cement milk, a concentration of polyvalent metal ions in a liquid phase portion of the cement milk is 200 ppm or less.   The method according to any one of claims 1 to 5, wherein the addition amount of the alkali metal carbonate is 0.1 to 5.0 parts by weight with respect to 100 parts by weight of water contained in the cement slurry.   The method according to claim 1, wherein the alkali metal carbonate is at least one selected from the group consisting of sodium carbonate, sodium hydrogen carbonate, potassium carbonate, and potassium hydrogen carbonate. The fluidizing agent is at least one selected from the group consisting of oxycarboxylate, naphthalenesulfonic acid, polycarboxylate, lignin sulfonate, and humate. the method of.

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