Soil improvement additive composition and soil improvement method

Abstract

To provide an additive composition for improving the ground, capable of improving the fluidity of soil cement slurry while maintaining sufficient strength of hardened soil cement slurry, and a method of improving the ground using the additive composition for improving the ground.SOLUTION: The additive composition for improving the ground, comprises a component (A): a polycarboxylic acid dispersant comprising a polyether chain on its side chain, and a component (B): a polymer of either or both of ethylene oxide and propylene oxide, or a polyol of a weight average molecular weight of from 1,000 to 50,000, with a ratio of the mass of the component (B) relative to the total mass of the component (A) and the component (B):[(B) / (A+B)] being from 10 to 50 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a soil improvement additive composition and a soil improvement method. [Background technology]

[0002] BACKGROUND ART Conventionally, soil cement slurry has been used to increase the strength of ground when constructing a structure with high load capacity on soft ground or for the purpose of strengthening an earth retaining wall. Soil cement slurry is made by mixing a slurry called cement milk, which is a mixture of cement-based materials and water, with soil. Among these, the most common ground improvement method is a deep soil improvement process, in which columnar reinforcement bodies made of solidified soil cement slurry are constructed in the ground to support buildings.

[0003] There are two types of methods that use soil cement slurry: (1) methods such as mechanical mixing and high-pressure injection mixing, in which cement milk is injected directly into the original ground to create and develop soil cement slurry underground; and (2) methods such as CRM, in which soil, cement-based materials, and water are mixed in above-ground equipment and the resulting soil cement slurry is returned to the borehole. In any of the construction methods, the soil cement slurry is required to have high fluidity from the viewpoint of workability.

[0004] One way to ensure fluidity is to add more water, but adding water increases the amount of soil to be treated, which in turn increases the cost of disposing of the resulting soil and the cost of materials such as cement.In addition, the large amount of soil generated during excavation becomes industrial waste, so consideration of environmental issues such as extending the life of disposal sites and reducing disposal costs become major issues.

[0005] Therefore, many methods have been proposed to improve the fluidity of soil cement slurry by adding additives such as dispersants to excavated soil in addition to water and cement. Polycarboxylic acid dispersants with polyether chains on the side chains are known as dispersants (Patent Document 1). Furthermore, in addition to polycarboxylic acid dispersants with polyether chains on the side chains, it has been proposed to use polyalkylene oxide adducts in which alkylene oxides are added to aliphatic hydrocarbons (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-256585 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-36044 Summary of the Invention [Problem to be solved by the invention]

[0007] However, although the polycarboxylic acid-based dispersant having a polyether chain on the side chain described in Patent Document 1 has the effect of improving the fluidity of soil cement slurry, it has the problem of reducing the strength after solidification. Even when a polyalkylene oxide adduct was used in combination as in Patent Document 2, a decrease in strength after solidification was unavoidable. In view of the above circumstances, an object of the present invention is to provide a ground improvement additive composition that can improve the fluidity of a soil cement slurry while ensuring sufficient strength of the soil cement slurry after solidification, and a ground improvement method using this ground improvement additive composition. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention employs the following configuration. [1] Component (A): a polycarboxylic acid-based dispersant having a polyether chain in the side chain; (B) component: a polyol which is a polymer of one or both of ethylene oxide and propylene oxide and has a weight average molecular weight of 1,000 to 50,000; A ground improvement additive composition, wherein the ratio of the mass of the component (B) to the total mass of the components (A) and (B) [(B) / (A+B)] is 10 to 50 mass %. [2] The soil improvement additive composition according to [1], further comprising component (C): an alkanolamine. [3] The soil improvement additive composition according to [2], wherein the ratio of the mass of the (C) component to the total mass of the (A) component and the (B) component [(C) / (A+B)] is greater than 0 mass% and not more than 20 mass%. [4] A ground improvement method for mixing cement milk with soil constituting the target ground, characterized in that the cement milk contains the ground improvement additive composition described in any one of [1] to [3]. [5] When the fine particle content of the soil constituting the target ground is less than 50% by mass, the amount of the soil improvement additive composition added to the mass of the soil constituting the target ground is 0.1 to 30 kg / m 3 The cement milk is mixed so as to When the fine particle content of the soil constituting the target ground is 50% by mass or more, the amount of the soil improvement additive composition added relative to the mass of the soil constituting the target ground is 0.1 to 50 kg / m 3 The ground improvement method described in [4], wherein the cement milk is mixed so as to obtain a ground improvement mixture. [Effects of the Invention]

[0009] The soil improvement additive composition of the present invention can improve the fluidity of the soil cement slurry while ensuring sufficient strength after solidification of the soil cement slurry. Furthermore, the soil improvement method of the present invention can improve the strength of the ground with high workability. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following description of the components may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0011] <Soil improvement additive composition> The soil improvement additive composition of the present invention is an additive composition that is mixed with water together with a cement-based material to form cement milk for soil improvement. The soil improvement additive composition of the present invention contains the components (A) and (B) described below, and preferably further contains the component (C) described below.

[0012] [Component (A)] Component (A) is a polycarboxylic acid-based dispersant having a polyether chain on the side chain. The type of component (A) is not particularly limited, and may be, for example, a polycarboxylic acid dispersant having one or more carboxylate or carboxylic acid repeating units. The repeating units constituting component (A) are not particularly limited, but examples include vinyl groups, (meth)acrylic groups, and maleic acid.

[0013] The component (A) having the repeating unit may be a homopolymer or a copolymer. Examples of homopolymers include homopolymers of methoxypolyethylene glycol methacrylate. Copolymers may be polymers in which two or more types of repeating units are arranged in the length direction of the polymer chain. The order in which the two or more types of repeating units are arranged is not particularly limited.

[0014] The component (A) may be, for example, a polycarboxylic acid obtained by copolymerizing at least one monomer represented by the following general formula (a1) (hereinafter referred to as monomer (a1)) with at least one monomer represented by the following general formula (a2) (hereinafter referred to as monomer (a2)).

[0015] R 1 R 3 C=CR 2 -(CH2) m1 (CO) p O(A 1 O) n1 X 1 (a1) [In general formula (a1), R 1 and R 2 each independently represents a hydrogen atom or a methyl group and may be the same or different from each other; m1 is an integer of 0 to 2; R 3 is a hydrogen atom or -COO(A 2 O) n2 X 2 where p is an integer of 0 or 1, and A 1 O and A 2 O each independently represents an oxyalkylene group or an oxystyrene group having 2 to 4 carbon atoms, 1 O and A 2 O may be the same or different from each other, n1 represents an integer of 2 to 300, n2 represents an integer of 0 to 300, and n1 and n2 may be the same or different from each other, X 1 and X 2 represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and each X 1 and X 2 may be the same or different from each other.

[0016] A 1 O and A 2 O is preferably an oxyalkylene group having 2 to 4 carbon atoms, and more preferably an oxyethylene group. n1 and n2 are preferably 5 to 200, more preferably 8 to 150, and even more preferably 12 to 60.

[0017] The monomer (a1) is not particularly limited, and examples thereof include (half) esters of one-terminal alkyl-blocked polyalkylene glycols such as methoxypolyethylene glycol, methoxypolypropylene glycol, methoxypolybutylene glycol, methoxypolystyrene glycol, and ethoxypolyethylenepolypropylene glycol with (meth)acrylic acid or maleic acid; ethers of 3-methyl-3-butenyl alcohol or (meth)allyl alcohol; and adducts of ethylene oxide or propylene oxide with (meth)acrylic acid, maleic acid, 3-methyl-3-butenyl alcohol, or (meth)allyl alcohol. Two or more types of monomer (a1) may be used in combination.

[0018] R 4 R 6 C=CR 5 -COOM 1 (a2) [In the general formula (a2), R 4 ~R 6 are each independently a hydrogen atom, a methyl group, or (CH2) m2 COOM 2 may be the same or different, (CH2) m2 COOM 2 COOM 1 or other (CH2) m2 COOM 2 and an anhydride may be formed, in which case the M 1 , M 2 does not exist. M 1 and M 2 each independently represents a hydrogen atom, an alkali metal, an alkaline earth metal, an ammonium group, an alkylammonium group or a substituted alkylammonium group, and m2 is a number of 0 to 2. M 1 and M 2 may be the same or different, and R 4 ~R 6 2 or more of (CH2) m2 COOM 2 In this case, each m2 may be the same or different, and each M 2may be the same or different.]

[0019] The monomer (a2) is not particularly limited, but examples thereof include monocarboxylic acid monomers such as (meth)acrylic acid and crotonic acid, dicarboxylic acid monomers such as maleic acid, itaconic acid and fumaric acid, anhydrides or salts thereof (for example, alkali metal salts, alkaline earth metal salts and ammonium salts), and mono-, di- and tri-alkyl (C2 to C8) ammonium salts in which the hydroxyl group may be substituted.

[0020] Among these, (meth)acrylic acid or a salt thereof, maleic acid, and maleic anhydride are preferred, and (meth)acrylic acid or an alkali metal salt thereof are more preferred. Two or more types of monomer (a2) may be used in combination. The monomer (a2) particularly preferably contains (meth)acrylic acid or an alkali metal salt thereof, and maleic acid.

[0021] Component (A) preferably has at least three repeating units: a repeating unit based on (meth)acrylic acid, a repeating unit based on maleic acid, and a long-chain polyether repeating unit based on monomer (a1).

[0022] In addition to repeating units based on monomer (a1) and repeating units based on monomer (a2), component (A) may also contain repeating units based on copolymerizable monomers such as acrylonitrile, (meth)acrylamide, styrene, alkyl (meth)acrylate (having 1 to 12 carbon atoms which may have a hydroxyl group), and styrenesulfonic acid. The amount of these copolymerizable monomers used is not particularly limited, but may be, for example, 0 mol% or more, 5 mol% or more, or 10 mol% or more of the total monomers, or may be, for example, 50 mol% or less, 40 mol% or less, or 30 mol% or less.

[0023] The weight average molecular weight of component (A) (gel permeation chromatography, polyethylene glycol equivalent) is not particularly limited, but from the viewpoint of dispersibility, it is preferably 1,000 to 100,000, more preferably 3,000 to 75,000, and even more preferably 5,000 to 50,000. When the weight average molecular weight of component (A) is within the preferred range, the dispersibility of the soil cement is exhibited.

[0024] There are no particular restrictions on the method for producing component (A), and it can be produced by a known method using the above-mentioned monomers. Commercially available products of component (A) include, for example, the AQUALOCK (registered trademark) series (Nippon Shokubai Co., Ltd.), the MARIALIMU (registered trademark) series (NOF Corporation), the MELFLUX (registered trademark) series (SKW East Asia Co., Ltd.), and the POLYTY (registered trademark) series (Lion Specialty Chemicals Co., Ltd.).

[0025] [(B) Component] Component (B) is a polyol which is a polymer of either or both of ethylene oxide and propylene oxide and has hydroxyl groups at both ends. The molar ratio of units (EO) based on ethylene oxide to units (PO) based on propylene oxide in the component (B) [(EO) / (PO)] is preferably 0-100 / 100-0, and more preferably 50-90 / 50-10. When component (B) is a copolymer of ethylene oxide and propylene oxide, there are no limitations on the arrangement of the units (EO) and units (PO), and they may be random or block.

[0026] The weight average molecular weight of component (B) (gel permeation chromatography method, polyethylene glycol equivalent) is 1,000 to 50,000, preferably 2,000 to 40,000, more preferably 3,000 to 20,000. By ensuring that the weight average molecular weight of component (B) is 1,000 to 50,000, a good dispersing effect can be obtained.

[0027] [(C) component] Component (C) is an alkanolamine. Alkanolamines are compounds with a hydroxyl group and an amino group in the alkane skeleton. By adding component (C) to components (A) and (B), the strength of the soil-cement slurry after hardening can be further improved. The component (C) is not particularly limited, but for example, ethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, and triisopropanolamine are preferred, with triethanolamine and triisopropanolamine being particularly preferred.

[0028] [Composition] In the soil improvement additive composition of the present invention, the ratio of the mass of component (B) to the total mass of components (A) and (B) [(B) / (A+B)] is 10 to 50 mass %. [(B) / (A+B)] is preferably from 15 to 45% by mass, more preferably from 20 to 40% by mass. When [(B) / (A+B)] is in the above range, the soil cement slurry can have an improved fluidity while ensuring sufficient strength after solidification of the soil cement slurry.

[0029] When the ground improvement additive composition of the present invention contains the (C) component, the ratio of the mass of the (C) component to the total mass of the (A) component and the (B) component [(C) / (A+B)] exceeds 0 mass%. [(C) / (A+B)] is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5 to 15.0% by mass, and even more preferably 1.0 to 10.0% by mass. When [(C) / (A+B)] is 0.1% by mass or more, the strength improvement effect of component (C) after solidification of the soil cement slurry can be sufficiently obtained. When [(C) / (A+B)] is 20% by mass or less, the strength improvement effect of the soil cement slurry after solidification can be more sufficiently obtained.

[0030] <Soil improvement method> The ground improvement method of the present invention is a ground improvement method in which cement milk is mixed with soil that constitutes the target ground, and is characterized in that the cement milk contains the ground improvement additive composition of the present invention.

[0031] The cement milk used in the ground improvement method of the present invention contains a cement-based material, the ground improvement additive composition of the present invention, and water. The cement-based material may be any commercially available cement-based solidification material, such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat cement, low-heat Portland cement, sulfate-resistant Portland cement, various blast-furnace cements, various fly ash cements, various silica cements, grout cement, and ecocement, and is not particularly limited.

[0032] The ratio of cement to improved soil varies depending on the soil properties such as moisture content and particle size of the excavated soil, and the purpose of use of the soil cement solidified body, but generally it is 1 / 3 of the improved soil. 3 The load is preferably 50 to 800 kg, more preferably 80 to 600 kg, and even more preferably 100 to 500 kg.

[0033] Here, the fine particle fraction means clay fraction and silt fraction. Clay and silt are classified according to the International Soil Society method, with clay being soil with a particle size of 0.002 mm or less, and silt being soil with a particle size of 0.02 to 0.002 mm. Note that soil with a particle size of 0.02 to 2 mm is classified as sand.

[0034] The water-cement ratio of cement milk varies depending on the soil properties such as the moisture content and particle size of the excavated soil, the intended use of the soil-cement solidified body, etc., but is generally preferably 30 to 500%, more preferably 50 to 350%, and even more preferably 60 to 300% by mass. The water-cement ratio in this case is expressed by the following formula: Water-cement ratio (W / C) (%) = 100 x (weight of water (kg) / weight of cement (kg))

[0035] The proportion of the soil improvement additive composition of the present invention in the cement milk varies greatly depending on the soil properties such as the moisture content and particle size of the excavated soil, the intended use of the soil cement solid, and the injection rate of the cement milk into the ground, but is preferably 0.01 to 75 mass%, more preferably 0.05 to 40 mass%, and even more preferably 0.1 to 20 mass%.

[0036] When the target ground is a sandy ground in which the fine particle content of the soil constituting the target ground is less than 50% by mass, it is preferable to mix cement milk so that the ratio of the ground improvement additive composition of the present invention to the mass of the soil constituting the target ground is 0.01 to 2.5% by mass, and it is more preferable to mix it so that it is 0.05 to 1.5% by mass.

[0037] When the target ground is a clay ground in which the fine particle content of the soil constituting the target ground is 50% by mass or more, it is preferable to mix cement milk so that the ratio of the ground improvement additive composition of the present invention to the mass of the soil constituting the target ground is 0.01 to 4.5% by mass, and it is more preferable to mix it so that it is 0.05 to 2.5% by mass.

[0038] When the fine particles of the soil constituting the target ground are less than 50% by mass, the mass of the soil improvement additive composition of the present invention per volume of the soil constituting the target ground is 0.1 to 30 kg / m 3 It is preferable to add and mix it into cement milk so that the 3 It is more preferable to add and mix so that

[0039] When the target ground is a clay ground in which the fine particles of the soil constituting the target ground are 50% by mass or more, the mass of the soil improvement additive composition of the present invention per volume of the soil constituting the target ground is 0.1 to 50 kg / m 3 It is preferable to add and mix it into cement milk so that the 3 It is more preferable to add and mix so that

[0040] Other components may be blended into the cement milk as long as they do not impair the effects of the present invention. Examples of other components include, in addition to the above copolymers, polycarboxylic acid dispersants having a polyoxyalkylene chain and a carboxyl group in the molecule, polycarboxylic acid dispersants having a carboxyl group, sulfonic acid or phosphate dispersants, as well as air-entraining agents, thickeners, flocculants, expanding agents, antifoaming agents, retarders, early strength additives / accelerators, strength enhancers, waterproofing agents, rust inhibitors, crack reduction agents, cement wetting agents, and separation reduction agents. [Example]

[0041] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description. It should be noted that Examples 1, 2, 15, and 16 are reference examples. The raw materials used in this example are as shown in the <Raw Materials Used> below. In the explanation of the raw materials used, EO represents an ethylene oxide or oxyethylene unit, and PO represents a propylene oxide or oxypropylene unit. Furthermore, " / " indicates the molar ratio of the components before and after it.

[0042] <Raw materials used> [Component (A)] a-1: Copolymer of maleic acid and EO adduct of allyl alcohol (EO addition amount: 34 moles) (maleic acid / allyl alcohol EO adduct = 90 / 10, weight average molecular weight: 23,000). a-2: Copolymer of methacrylic acid, methyl methacrylate, and methoxypolyethylene glycol methacrylate (EO addition amount: 25 moles) (methacrylic acid / methyl methacrylate / methoxypolyethylene glycol methacrylate=70 / 15 / 15, weight average molecular weight: 25,000).

[0043] [(B) Component] b-1: Polyoxyethylene polyoxypropylene glycol (EO / PO=75 / 25, weight average molecular weight: 5,500). b-2: Polyoxyethylene polyoxypropylene glycol (EO / PO=20 / 80, weight average molecular weight: 3,100). b-3: Polyethylene glycol (weight average molecular weight: 6,000).

[0044] [(BX) component] bx-1: Polyoxyethylene polyoxypropylene butyl ether (EO / PO=60 / 40, weight average molecular weight: 3,950).

[0045] [(C) component] ·c―1: Triethanolamine.

[0046] [Sample soil] ·d-1: Soil equivalent to clayey ground with the properties shown in Table 1. ·d-2: Soil equivalent to sandy ground with the properties shown in Table 1.

[0047] [Table 1]

[0048] [Cement-based materials] · e-1: Blast furnace type B cement (manufactured by Sumitomo Osaka Cement Co., Ltd.).

[0049] <Comparative Example 1> Cement milk was produced by uniformly mixing 450 g of water and 450 g of cement material (e-1) using a stirring motor. This was added to 1,790 g of sample soil (d-1) and stirred with a soil mixer to obtain soil-cement slurry.

[0050] <Comparative Examples 2 to 10, Examples 1 to 14> After mixing 10 g of the additive composition (60% by mass aqueous solution) with 440 g of water, 450 g of cement material (e-1) was added and the mixture was uniformly mixed using a stirring motor to produce cement milk. This was then added to 1,790 g of sample soil (d-1) and stirred with a soil mixer to obtain soil cement slurry.

[0051] [Table 2]

[0052] <Comparative Example 11> Cement milk was produced by uniformly mixing 200 g of water and 200 g of cement material (e-1) using a stirring motor. This was added to 1,806 g of sample soil (d-2) and stirred with a soil mixer to obtain soil-cement slurry.

[0053] <Examples 15 to 28> After mixing 3.3 g of the additive composition (60% by mass aqueous solution) with 196.7 g of water shown in Table 3, 200 g of cement material (e-1) was added and the mixture was uniformly mixed using a stirring motor to produce cement milk. This was then added to 1,806 g of sample soil (d-2) and stirred with a soil mixer to obtain soil cement slurry.

[0054] [Table 3]

[0055] <Evaluation> [Fluidity test] The flow value of the soil cement slurry obtained in each example was determined by a mortar flow test in accordance with JIS R 5201 to evaluate the fluidity. The flow values ​​of the examples listed in Table 4 were compared with the flow values ​​of Comparative Example 1, and the flow values ​​of the examples listed in Table 5 were compared with the flow values ​​of Comparative Example 11. Those that showed an improvement of 21 mm or more in the flow value were evaluated as passing (◯). The results are shown in Tables 4 and 5.

[0056] [Uniaxial compressive strength test] The soil cement slurry obtained in each example was cast in a formwork with a diameter of 5 cm and a height of 10 cm, and the unconfined compressive strength at 28 days was measured in accordance with JIS A 1108. The unconfined compressive strength of the examples listed in Table 4 was compared with that of Comparative Example 1, and the unconfined compressive strength of the examples listed in Table 5 was compared with that of Comparative Example 11. Those with an unconfined compressive strength of 91% or more were evaluated as passing (◯). The results are shown in Tables 4 and 5.

[0057] [Table 4]

[0058] [Table 5]

[0059] As shown in Comparative Examples 2 and 3 in Table 4, when an additive composition containing only component (A) was used, the fluidity was improved but the unconfined compressive strength at 28 days decreased. As shown in Comparative Examples 4 to 6 in Table 4, although the use of component (C) could improve the unconfined compressive strength at 28 days, it was difficult to achieve both fluidity and unconfined compressive strength at 28 days using only components (A) and (C).

[0060] Furthermore, as shown in Comparative Example 7 in Table 4, even when part of component (A) was replaced with the monool bx-1, fluidity was maintained, but a decrease in the unconfined compressive strength at 28 days of age could not be avoided. Furthermore, as shown in Comparative Examples 8 to 10 in Table 4, even when most or all of the (A) component was replaced with the (B) component of the present invention, not only did the unconfined compressive strength at an age of 28 days decrease, but the fluidity was not sufficiently improved.

[0061] In contrast, each of the examples shown in Tables 4 and 5 had good fluidity and sufficient unconfined compressive strength at an age of 28 days. From the above results, it was found that by replacing a part of component (A) with component (B) in an appropriate ratio, it is possible to achieve both good fluidity and strength after solidification.

Claims

1. Component (A): a polycarboxylic acid-based dispersant having a polyether chain on the side chain; (B) component: a polyol which is a polymer of one or both of ethylene oxide and propylene oxide and has a weight average molecular weight of 1,000 to 50,000; and (C) component: an alkanolamine, The ratio of the mass of the (B) component to the total mass of the (A) component and the (B) component [(B) / (A + B)] is 10 to 50 mass%.

2. The ratio of the mass of the (C) component to the total mass of the (A) component and the (B) component [(C) / (A + B)] is more than 0 mass% and 20 mass% or less. The soil improvement additive composition according to claim 1.

3. A ground improvement method comprising mixing cement milk with soil constituting a target ground, wherein the cement milk contains the ground improvement additive composition according to claim 1 or 2.

4. When the fine particle content of the soil constituting the target ground is less than 50 mass%, the amount of the soil improvement additive composition added relative to the mass of the soil constituting the target ground is 0.1 to 30 kg / m ３ The cement milk is mixed so as to When the fine particle content of the soil constituting the target ground is 50% by mass or more, the amount of the soil improvement additive composition added relative to the mass of the soil constituting the target ground is 0.1 to 50 kg / m ３ The ground improvement method according to claim 3, wherein the cement milk is mixed so as to obtain a soil solubility of 100%.

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