Cement additive for spray concrete, cement admixture for spray concrete, spray concrete, and method for producing spray concrete

Abstract

To provide a cement additive for spray concrete which has excellent fluidity and fluidity retainability without impairing the strength of concrete and without delaying setting and can impart properties excellent in adhesion to the natural ground or the like to spray concrete (particularly base concrete).SOLUTION: A cement additive for shotcrete, comprising at least one hydroxyl group-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, wherein the hydroxyl group-containing organic compound has 4 to 10 hydroxyl groups in one molecule.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cement additive to be added to shotcrete, a cement admixture to be added to shotcrete and containing the cement additive, shotcrete containing the cement additive, and a method for producing shotcrete containing the cement additive. [Background technology]

[0002] Tunnel construction using shotcrete is often carried out in mountainous areas, and the ready-mixed concrete used for this (hereinafter sometimes referred to as "base concrete") is often transported over long distances from ready-mixed concrete plants in the city, or prepared in temporary on-site plants near the construction site. Even if the base concrete is prepared in an on-site plant, it must be transported into the tunnel and pumped out using a separately prepared concrete pump, so a considerable amount of time is required before the concrete can actually be applied to the tunnel construction.

[0003] Whether the base concrete is prepared at a city ready-mix concrete plant or at a temporary on-site plant near the construction site, the base concrete used in shotcrete needs to have the fluidity and ability to maintain its fluidity (hereinafter referred to as "fluidity retention"). Insufficient fluidity and fluidity retention can have adverse effects on the properties of the shotcrete, such as pulsation and blockages when pumping, or reduced mixability with accelerators.

[0004] It has been proposed to add additives to base concrete to impart fluidity and fluidity retention to the base concrete. Examples of conventional additives for imparting fluidity and fluidity retention to base concrete include AE ​​water-reducing agents, such as lignin-based dispersants, polycarboxylic acid-based dispersants, naphthalene sulfonic acid-based dispersants, and melamine-based dispersants. It has also been disclosed that optimizing the chemical structure of these additives can maintain fluidity for a long period of time, i.e., improve fluidity retention (Patent Document 1).

[0005] It has also been proposed to adjust the fluidity and fluidity retention of base concrete by combining conventional additives with components that have set retardation properties. For example, Patent Document 2 describes a technology in which an alkali metal sulfate and a retarder are added to base concrete to improve the fluidity retention of the base concrete and reduce rebound and dust of shotcrete.

[0006] However, depending on the type of alkali metal salt, problems such as a decrease in the fluidity retention of the base concrete may occur, a decrease in the mixing ratio of the alkali metal salt may result in a decrease in the fluidity retention and an increase in rebound and dust, and further, depending on the type of retarder, the fluidity retention may also decrease.

[0007] In particular, for shotcrete, adhesion when the concrete is sprayed onto the natural ground or the like is an important factor. Generally, adhesion refers to the property of good adhesion to an object such as the natural ground and little rebound. Therefore, as a means of improving the adhesion of shotcrete after spraying, various adjustments to the components of the quick-setting agent and the addition of a viscosity improver to the base concrete to reduce dust and rebound have been proposed (Patent Documents 3 and 4). However, with Patent Documents 3 and 4, it is sometimes difficult to control the quick-setting property, and there is also the risk that the addition of a viscosity improver will increase the viscosity of the base concrete, reducing its pumpability.

[0008] Furthermore, the adhesion of shotcrete does not simply mean good adhesion to the target object, such as the natural ground, but also the properties of the concrete when it adheres; in other words, it is sometimes desirable for the surface of the shotcrete to remain somewhat moist immediately after spraying, rather than for it to harden immediately. This is because shotcrete has the ability to harden so that the concrete sprayed in the first layer and the concrete sprayed in the second layer blend together (thick spraying), preventing delamination and resulting in a solid, solid, hardened shotcrete. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2018-154712 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-036028 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-219302 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-146716 Summary of the Invention [Problem to be solved by the invention]

[0010] In view of the above circumstances, an object of the present invention is to provide a cement additive for shotcrete that can impart to shotcrete (particularly base concrete) excellent fluidity and fluidity retention properties without delaying setting and excellent adhesion to the natural ground, etc., without impairing the strength of the concrete; a cement admixture containing the cement additive; shotcrete containing the cement additive; and a method for producing shotcrete containing the cement additive. [Means for solving the problem]

[0011] The gist of the configuration of the present invention is as follows. [1] A cement additive for sprayed concrete, comprising at least one hydroxyl-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, wherein the hydroxyl-containing organic compound has 4 to 10 hydroxyl groups per molecule. [2] The cement additive for sprayed concrete according to [1], wherein the hydroxyl group-containing organic compound does not contain reducing sugars. [3] The cement additive for shotcrete according to [1] or [2], wherein the hydroxyl group-containing organic compound has 6 to 8 hydroxyl groups in one molecule. [4] The cement additive for shotcrete according to [1] or [2], wherein the hydroxyl group-containing organic compound includes a sugar alcohol. [5] A cement admixture for sprayed concrete, comprising: a cement additive for sprayed concrete, the cement additive comprising at least one hydroxyl group-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, the hydroxyl group-containing organic compound having 4 to 10 hydroxyl groups per molecule; and a cement dispersant. [6] The cement dispersant is an ethylenically unsaturated monomer having a polyalkylene glycol ether chain represented by the following general formula (1): [ka] (In the formula, R 1 , R 2 , R 3 are each independently a hydrogen atom or a methyl group, R 4 represents hydrogen, a methyl group, or an aliphatic hydrocarbon group having 2 to 20 carbon atoms; AO represents an oxyalkylene group having 2 to 4 carbon atoms; a represents an integer of 2 to 350; n represents an integer of 0 to 2; and m represents 0 or 1. Ethylenically unsaturated monomer (2) represented by the following general formula (2): [ka] (In the formula, R 5 and R 7 are each independently a hydrogen atom or a methyl group; M is a hydrogen atom, a metal atom, an ammonium group or an organic ammonium group; R 6represents a hydrogen atom or a group represented by -COOM2, and M2 represents a hydrogen atom, a metal atom, an ammonium group, or an organic ammonium group. and a hydrolyzable ethylenically unsaturated monomer (3) represented by the following general formula (3): [ka] (In the formula, R 8 , R 9 , R 10 are each independently a hydrogen atom or a methyl group, R 11 represents an alkyl group or an alkoxy group having 2 to 10 carbon atoms, and n represents an integer of 0 to 2.), wherein the ratio (molar fraction) of the number of moles of the monomer (1): the number of moles of the monomer (2): the number of moles of the monomer (3) is 5 to 80%, 0 to 95%, or 0 to 95%, and either one of the molar fractions of the monomer (2) and the monomer (3) is not 0, and the sum of the molar fractions of the monomer (2) and the monomer (3) is 20 to 95%. [7] The cement admixture for sprayed concrete according to [5] or [6], wherein the content of the cement additive for sprayed concrete in the cement admixture for sprayed concrete is 2% by mass or more and 15% by mass or less. [8] A cement admixture for sprayed concrete according to [5] or [6], containing 0.8 parts by mass or more and 20.0 parts by mass or less of the cement dispersant per 100 parts by mass of the cement additive for sprayed concrete. [9] A sprayed concrete comprising: a cement additive for sprayed concrete, the cement additive comprising at least one hydroxyl group-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, the hydroxyl group-containing organic compound having 4 to 10 hydroxyl groups per molecule; a cement dispersant; cement; water; and an aggregate.

[10] A method for producing sprayed concrete, which comprises adding to base concrete a cement additive for sprayed concrete, the cement additive comprising at least one hydroxyl group-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, wherein the hydroxyl group-containing organic compound has 4 to 10 hydroxyl groups per molecule. [Effects of the Invention]

[0012] According to one aspect of the cement additive for shotcrete of the present invention, the additive contains at least one hydroxyl-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, and the hydroxyl-containing organic compound has 4 to 10 hydroxyl groups per molecule, so that the concrete strength is not impaired, setting is not delayed, and the shotcrete (particularly, base concrete) has excellent fluidity and fluidity retention, and excellent adhesion to the natural ground, etc. Furthermore, according to another aspect of the cement additive for shotcrete of the present invention, the additive can impart excellent fluidity and fluidity retention to the base concrete, thereby ensuring the usable life of the base concrete mixed in the plant, suppressing pressure loss and clogging in the piping, and improving pumpability.

[0013] Furthermore, according to the above-described embodiment of the cement additive for sprayed concrete of the present invention, even when it comes into contact with an accelerator component, the adhesion of the sprayed concrete to the natural ground, etc. is not impaired, and delay in setting of the sprayed concrete is prevented, thereby making it possible to prevent sagging and rebound of the sprayed concrete after spraying.

[0014] According to an embodiment of the cement additive for shotcrete of the present invention, the hydroxyl-containing organic compound does not contain reducing sugars, which improves the compatibility of the cement additive for shotcrete and provides solution stability, thereby preventing separation of components contained in the cement admixture containing the cement additive. Therefore, the cement admixture containing the cement additive without reducing sugars can be added to base concrete in a one-component form, improving workability.

[0015] According to an embodiment of the cement additive for sprayed concrete of the present invention, the hydroxyl group-containing organic compound contains a sugar alcohol, which can reliably impart excellent fluidity, fluidity retention, and adhesion to the ground, etc. to the sprayed concrete.

[0016] According to an aspect of the cement additive for shotcrete of the present invention, the hydroxyl group-containing organic compound contains a sugar alcohol, thereby making it possible to reliably improve the strength of concrete.

[0017] According to an embodiment of the cement additive for shotcrete of the present invention, the hydroxyl group-containing organic compound has 6 to 8 hydroxyl groups in one molecule, thereby reliably imparting to the shotcrete excellent fluidity, fluidity retention, and adhesion to the natural ground, etc. DETAILED DESCRIPTION OF THE INVENTION

[0018] The cement additive for shotcrete of the present invention contains at least one hydroxyl-containing organic compound selected from the group consisting of sugar alcohols and sugars excluding sugar alcohols, and the hydroxyl-containing organic compound has 4 to 10 hydroxyl groups per molecule. The cement additive for shotcrete of the present invention is a cement additive that is added to shotcrete before the shotcrete is applied to an object such as natural ground. Furthermore, the cement additive for shotcrete of the present invention may use, as the hydroxyl-containing organic compound, either a sugar alcohol or a sugar excluding sugar alcohols, either alone or in combination of two or more thereof.

[0019] The cement additive for shotcrete of the present invention contains at least one hydroxyl-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, and the hydroxyl-containing organic compound has 4 to 10 hydroxyl groups per molecule, so that the concrete strength is not impaired, setting is not delayed, and excellent fluidity and flow retention are achieved, and the shotcrete (particularly the base concrete) can be imparted with properties such as excellent adhesion to the natural ground. Furthermore, because the cement additive for shotcrete of the present invention can impart excellent fluidity and flow retention to the base concrete, the usable life of the base concrete mixed at the plant is ensured, pressure loss and clogging in the piping are suppressed, and pumpability is improved.

[0020] Furthermore, the cement additive for sprayed concrete of the present invention does not impair the adhesion of the sprayed concrete to the natural ground, etc., even when it comes into contact with an accelerator component, and it is possible to prevent delay in the setting of the sprayed concrete, thereby preventing sagging and rebound of the sprayed concrete after spraying.

[0021] The blending components of the cement additive for shotcrete of the present invention will be described in detail below.

[0022] <Cement additive for shotcrete> A sugar alcohol with 4 to 10 hydroxyl groups per molecule The sugar alcohol is not particularly limited as long as it has 4 to 10 hydroxyl groups per molecule, and examples thereof include tetritols, pentitols, hexitols, heptitols, and octitols, which are produced by reducing the carbonyl group of aldoses or ketoses. Specific examples include erythritol, xylitol, mannitol, sorbitol, maltitol, lactitol, and isomalt. These sugar alcohols may be used alone or in combination of two or more.

[0023] Of the sugar alcohols having 4 to 10 hydroxyl groups per molecule, sugar alcohols having 6 to 8 hydroxyl groups per molecule are preferred because they can reliably impart excellent fluidity, fluidity retention, and adhesion to the ground, etc. to the sprayed concrete. Mannitol and sorbitol are preferred because they have excellent water solubility and solution stability, making it easy to add them uniformly to the base concrete, with sorbitol being particularly preferred.

[0024] Sugars with 4 to 10 hydroxyl groups per molecule, excluding sugar alcohols Sugars excluding sugar alcohols (hereinafter sometimes simply referred to as "sugars") are not particularly limited as long as they have 4 to 10 hydroxyl groups per molecule. Examples of sugars having 4 to 10 hydroxyl groups per molecule include pentose monosaccharides such as ribose, lyxose, xylose, arabinose, xylulose, and ribulose; hexose monosaccharides such as glucose, altrose, mannose, galactose, idose, fructose, sorbose, and tagatose; and disaccharides such as sucrose (saccharose), lactulose, lactose (milk sugar), maltose (malt sugar), and trehalose. These sugars may be used alone or in combination of two or more.

[0025] Of the sugars having 4 to 10 hydroxyl groups per molecule, those not containing reducing sugars are preferred because they improve compatibility with cement additives for shotcrete, providing solution stability and preventing separation of components contained in cement admixtures containing the cement additives. Therefore, cement admixtures containing the cement additives that do not contain reducing sugars can be added to base concrete in a one-component form, improving workability. Among sugars that do not contain reducing sugars, sucrose and trehalose are preferred because they improve compatibility with cement additives for shotcrete and provide solution stability. Furthermore, sucrose is particularly preferred because it provides sufficient pot life to base concrete mixed in a plant, reliably preventing pressure loss and clogging in piping and improving pumpability.

[0026] Reducing sugars may react with oxidizing substances, potentially changing their own performance. Reducing sugars may also affect the effectiveness of oxidizing substances, such as calcium nitrate, which accelerates concrete hardening, and peroxides, which are used as additives for colored coatings. Some accelerators used in sprayed concrete contain aluminum. When trivalent aluminum is reduced by reducing sugars to produce metallic aluminum, the metallic aluminum reacts with calcium to generate hydrogen, potentially causing hydrogen embrittlement in steel. For these reasons, sugars with 4 to 10 hydroxyl groups per molecule are preferably not reducing sugars.

[0027] Furthermore, among sugar alcohols and sugars other than sugar alcohols, it is preferable to include sugar alcohols as the hydroxyl group-containing organic compound, as this can reliably impart excellent fluidity, flow retention, and adhesion to the ground, etc. to the sprayed concrete, and sugars other than sugar alcohols are preferred from the standpoint of ease of acquisition while imparting excellent fluidity, flow retention, and adhesion to the ground, etc. to the sprayed concrete.

[0028] The cement additive for shotcrete of the present invention may be added to shotcrete in the form of an admixture premixed with a cement dispersant described below, or may be added to shotcrete separately from the cement dispersant. The cement additive for shotcrete of the present invention may also be added to base concrete or to an accelerator. The cement additive for shotcrete of the present invention may also be added separately to the tip of the spraying nozzle.

[0029] Next, the cement admixture for shotcrete containing the cement additive for shotcrete of the present invention will be described in detail.

[0030] <Cement admixture for shotcrete, including cement additives for shotcrete> A cement admixture for sprayed concrete containing the cement additive for sprayed concrete of the present invention (hereinafter, sometimes simply referred to as a "cement admixture for sprayed concrete") contains the above-mentioned cement additive for sprayed concrete of the present invention and a cement dispersant.

[0031] Examples of the cement dispersant include an ethylenically unsaturated monomer (1) having a polyalkylene glycol ether chain represented by the following general formula (1): [ka] (In the formula, R 1 , R 2 , R 3 are each independently a hydrogen atom or a methyl group, R 4 represents hydrogen, a methyl group, or an aliphatic hydrocarbon group having 2 to 20 carbon atoms; AO represents an oxyalkylene group having 2 to 4 carbon atoms; a represents an integer of 2 to 350; n represents an integer of 0 to 2; and m represents 0 or 1. Ethylenically unsaturated monomer (2) represented by the following general formula (2): [ka] (In the formula, R 5 and R 7 are each independently a hydrogen atom or a methyl group; M is a hydrogen atom, a metal atom, an ammonium group or an organic ammonium group; R 6 represents a hydrogen atom or a group represented by -COOM2, and M2 represents a hydrogen atom, a metal atom, an ammonium group, or an organic ammonium group. and a hydrolyzable ethylenically unsaturated monomer (3) represented by the following general formula (3): [ka] (In the formula, R 8 , R 9 , R 10 are each independently a hydrogen atom or a methyl group, R 11represents an alkyl group or an alkoxy group having 2 to 10 carbon atoms, and n represents an integer of 0 to 2.) and the ratio (molar fraction) of the number of moles of the monomer (1): the number of moles of the monomer (2): the number of moles of the monomer (3) is 5 to 80%, 0 to 95%, or 0 to 95%, and either one of the molar fractions of the monomer (2) and the monomer (3) is not 0%, and the total molar fraction of the monomer (2) and the monomer (3) is 20 to 95%.

[0032] When the cement dispersant is the above-mentioned copolymer, dispersibility of the cement paste can be obtained even in the formulation of various concrete compositions, contributing to imparting high fluidity and fluidity retention to the base concrete, and making it possible to produce a concrete composition that does not impair setting or strength even when used as sprayed concrete.

[0033] In the monomer (1), R 2 is preferably a methyl group, and when m is 1 and n is 0, R 2 is particularly preferably a methyl group. 4 is preferably hydrogen, a methyl group, or an aliphatic hydrocarbon group having 2 to 5 carbon atoms, and particularly preferably hydrogen or a methyl group. Furthermore, in order to impart appropriate dispersibility and viscosity to the base concrete, the lower limit of a is preferably 3, more preferably 4, even more preferably 5, and particularly preferably 10. On the other hand, the upper limit of a is preferably 200, and particularly preferably 100.

[0034] In the monomer (1), the larger the average number of added moles of oxyalkylene groups (a), the stronger the steric repulsion force generated by the cement dispersant, resulting in higher dispersibility. However, as the side chain length of the oxyalkylene group increases, the viscosity of the cement admixture for shotcrete increases as the cement dispersant's molecular weight increases, and the viscosity of the shotcrete composition to which it is added also tends to increase. Furthermore, as the molecular chain of the cement dispersant elongates, the time required to achieve the desired dispersibility in the shotcrete increases, thereby lengthening the time required to achieve the desired dispersibility, i.e., the time required to mix the cement admixture for shotcrete. On the other hand, when the side chain length of the oxyalkylene group is short, the dispersibility of the cement dispersant in the shotcrete is low, but the viscosity of the cement admixture for shotcrete and the shotcrete to which it is added can be kept low. Furthermore, the time required for the cement dispersant to achieve the desired dispersibility in the shotcrete tends to be shorter. In this way, the performance of a cement dispersant varies depending on the length of its side chain, and the average number of moles of oxyalkylene groups added tends to have a large effect on the performance of the cement dispersant.

[0035] Monomer (1) may contain multiple types of oxyalkylene groups. From the viewpoint of an appropriate balance between hydrophilicity and hydrophobicity, oxyethylene groups and oxypropylene groups are preferred, and it is particularly preferred that oxyethylene groups account for 90% or more.

[0036] The monomer (1) may contain a plurality of types of monomer (1) having different types and / or different repeating numbers of oxyalkylene groups.

[0037] Monomer (2) is one or more monomers selected from the group consisting of unsaturated monocarboxylic acids (salts) and unsaturated dicarboxylic acids (salts). Examples of monomer (2) include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and dicarboxylic acids such as maleic acid and fumaric acid.

[0038] Monomer (3), a hydrolyzable ethylenically unsaturated monomer, is a monomer that forms active bonds with cement and the like upon hydrolysis in shotcrete. The structural units derived from monomer (3), in combination with the structural units derived from monomer (1), impart excellent fluidity and handleability to concrete used in spraying while improving air stability. Furthermore, the structural units derived from monomer (3) form active bonds with cement and the like upon hydrolysis, enabling the cement and the like to disperse over time in the shotcrete. Examples of monomer (3) include (meth)acrylic acid esters. Among these, acrylic acid esters are preferred from the viewpoint of hydrolysis. Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate.

[0039] In the monomer (3), in the general formula (3), R 10 is preferably hydrogen, and R 11 is preferably an alkyl group, and R 11 The number of carbon atoms is preferably 2 to 4.

[0040] Furthermore, if necessary, other ethylenically unsaturated monomers (hereinafter sometimes referred to as "monomer (4)") other than the above-described monomers (1), (2), and (3) may be contained. Examples of other ethylenically unsaturated monomers include methyl (meth)acrylate, phosphate ester monomers having a phosphate ester at the terminal, monomers having a sulfate ester at the terminal, and (meth)acrylamide monomers. The presence of these other ethylenically unsaturated monomers is expected to stabilize dispersibility and suppress performance changes due to material variations.

[0041] When the monomer (4) is contained as a structural unit, the molar fraction of the monomer (4) is not particularly limited and can be selected within a range that does not impair the effects of the present invention. For example, it is preferably 10% or less, and particularly preferably 5% or less.

[0042] The content of the cement additive for shotcrete in 100% by mass of the cement admixture for shotcrete is not particularly limited, but the lower limit is preferably 2% by mass, more preferably 3% by mass, and particularly preferably 4% by mass, from the viewpoint of reliably imparting to the shotcrete excellent fluidity, fluidity retention, and adhesion to the natural ground, etc. On the other hand, the upper limit of the content of the cement additive for shotcrete in the cement admixture for shotcrete is preferably 15% by mass, more preferably 13% by mass, and particularly preferably 8% by mass, from the viewpoint of contributing to imparting high fluidity and fluidity retention to the base concrete.

[0043] In addition, in the cement admixture for shotcrete, the blending ratio of the cement dispersant to the cement additive for shotcrete is not particularly limited, but the lower limit of the mass ratio of each active ingredient of the cement dispersant to the cement additive for shotcrete is preferably 0.5, more preferably 0.8, and particularly preferably 1.2, in order to prevent a decrease in dispersibility and a decrease in dispersibility retention. On the other hand, in order to prevent excessive dispersibility and separation, the upper limit of the mass ratio of each active ingredient of the cement dispersant to the cement additive for shotcrete is preferably 10.0, more preferably 5.0, and particularly preferably 3.0.

[0044] The solid content of the cement admixture for shotcrete of the present invention is not particularly limited, but is preferably 10.0 mass% or more and 40.0 mass% or less, and particularly preferably 15.0 mass% or more and 35.0 mass% or less. Furthermore, water is preferred as a dispersion medium for the solid content of the cement admixture for shotcrete of the present invention.

[0045] In the cement admixture for shotcrete of the present invention, a mixed solution of the cement additive for shotcrete of the present invention and a cement dispersant is stable for a long period of time. The cement additive for shotcrete of the present invention has excellent compatibility for a long period of time, which imparts solution stability to the cement admixture for shotcrete of the present invention.

[0046] The cement admixture for sprayed concrete of the present invention may further contain, as necessary, a viscosity-increasing component, a shrinkage-reducing component, a rust-preventing component, a pH-adjusting component, a preservative, etc., in addition to the cement additive for sprayed concrete and the cement dispersant of the present invention.

[0047] Next, the shotcrete containing the cement additive for shotcrete of the present invention will be described in detail.

[0048] <Sprayed concrete containing cement additives for sprayed concrete> Shotcrete containing the cement additive for shotcrete of the present invention (hereinafter sometimes simply referred to as "shotcrete containing a cement additive") contains the above-mentioned cement additive for shotcrete of the present invention, a cement dispersant, cement, water, and aggregate. That is, shotcrete containing the cement additive of the present invention contains the above-mentioned cement admixture for shotcrete of the present invention, cement, water, and aggregate. Furthermore, shotcrete containing the cement additive of the present invention may further contain an accelerator.

[0049] The cement is cement or a powder containing cement components. Examples of cement include hydraulic cements such as Portland cement, calcium aluminate cement, magnesium phosphate cement, magnesium potassium phosphate cement, sulfoaluminate cement, pozzolan cement, slag cement, fly ash cement, and silica fume cement. Among these cements, cements with high early strength are preferred in terms of ensuring setting and early strength, and specifically, high-early-strength Portland cement, alumina cement, etc. are preferred.

[0050] Aggregates can include fine aggregates and coarse aggregates. That is, the shotcrete containing the cement additive of the present invention is a shotcrete containing both fine aggregates and coarse aggregates, or either one of them. When the shotcrete containing the cement additive of the present invention contains coarse aggregates, the maximum dimension of the coarse aggregate is preferably 10 mm or less. Examples of aggregates include fine aggregates such as sand, and coarse aggregates such as gravel and crushed stone. Examples of aggregates include silica, quartz, sand, crushed marble, glass spheres, granite, limestone, calcite, feldspar, alluvial sand, any other durable aggregate, and mixtures thereof. Since aggregates containing a large amount of clay (e.g., containing 20% ​​by mass or more of a viscosity component) may make it difficult to achieve the effects of the present invention, the clay content of the aggregate is preferably 10% by mass or less, and clay-free aggregates are particularly preferred.

[0051] The amount of aggregate mixed in the shotcrete containing the cement additive of the present invention is, for example, preferably 40% by mass or more and 85% by mass or less, and particularly preferably 55% by mass or more and 75% by mass or less.

[0052] The quick-setting admixture can be in any of powder, liquid, and slurry forms. Examples of quick-setting admixtures include those containing calcium aluminate, calcium sulfoaluminate, and aluminum sulfate as their main components. Commercially available quick-setting admixtures include "Sigma Shot V" manufactured by Denka Co., Ltd., "Shot Master A" manufactured by Pacific Materials Corporation, and "Master Rock SA161" manufactured by Pozzolith Solutions Co., Ltd. Among these quick-setting admixtures, liquid quick-setting admixtures are preferred, and "Master Rock SA161" manufactured by Pozzolith Solutions Co., Ltd. is preferred because it is liquid and therefore easy to mix with concrete and can suppress dust generation.

[0053] The content of the cement additive for shotcrete per 100 parts by mass of cement is not particularly limited, but the lower limit is preferably 0.01 parts by mass, more preferably 0.015 parts by mass, and particularly preferably 0.02 parts by mass, from the viewpoint of reliably imparting to the shotcrete excellent fluidity, fluidity retention, and adhesion to the natural ground, etc. On the other hand, the upper limit of the content of the cement additive for shotcrete per 100 parts by mass of cement is preferably 0.25 parts by mass, more preferably 0.15 parts by mass, and particularly preferably 0.1 parts by mass, from the viewpoint of contributing to imparting to the base concrete high fluidity, fluidity retention, and adhesion to the natural ground, etc., while preventing a decrease in strength due to setting delay.

[0054] The content of the cement dispersant relative to 100 parts by mass of cement is not particularly limited, but is preferably 0.05 parts by mass or more and 1.00 parts by mass or less in terms of the amount of active ingredient.

[0055] Base concrete 1m 3 The content of the cement additive for shotcrete relative to the amount of the sprayed concrete is not particularly limited, but the lower limit is 30 g / m from the viewpoint of reliably imparting excellent fluidity, fluidity retention, and adhesion to the natural ground, etc. to the shotcrete. 3 is preferred, and 45 g / m 3 More preferably, 60 g / m 3 is particularly preferable. On the other hand, 3The upper limit of the content of cement additives for shotcrete is 1300 g / m, as it contributes to imparting high fluidity and fluidity retention to the base concrete. 3 is preferred, and 750 g / m 3 More preferably, 600 g / m 3 is particularly preferred.

[0056] Next, the method for producing shotcrete of the present invention will be described in detail.

[0057] <Method for producing shotcrete of the present invention> A method for producing shotcrete of the present invention includes adding to base concrete a cement additive for shotcrete, the cement additive comprising at least one hydroxyl-containing organic compound selected from the group consisting of sugar alcohols and sugars excluding sugar alcohols, the hydroxyl-containing organic compound having 4 to 10 hydroxyl groups per molecule. The method for adding the cement additive for shotcrete to base concrete may involve, for example, adding the cement additive for shotcrete to base concrete in the form of an admixture in which the cement additive for shotcrete is premixed with a cement dispersant, or adding the cement additive for shotcrete alone to the base concrete separately from the cement dispersant.

[0058] The sprayed concrete of the present invention can be applied by either dry or wet spraying. From the viewpoint of stable sprayability (pumpability, adhesion, setting characteristics, strength characteristics, and minimal spraying unevenness), it is preferably applied to wet spraying. The wet spraying method involves, for example, preliminarily adding the cement additive for sprayed concrete or the cement admixture for sprayed concrete of the present invention to cement, water, and aggregate, mixing the resulting base concrete, pumping it to the nozzle outlet, and simultaneously mixing it with an accelerator supplied to the vicinity of the nozzle outlet via a separate piping system, and spraying the resulting mixture. Furthermore, conventional spraying nozzles and spraying systems can be used to apply the sprayed concrete of the present invention. [Example]

[0059] The cement additive for shotcrete and the cement admixture for shotcrete of the present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below.

[0060] The cement additives for shotcrete, cement dispersants, and materials used in the shotcrete used in the examples and comparative examples are shown in Table 1. Note that hereinafter, the cement additive for shotcrete may be simply referred to as the "additive," and the cement dispersant may be simply referred to as the "dispersant."

[0061] [Table 1]

[0062] In Table 1, the numbers of hydroxyl groups per molecule of Ad1 to Ad6 are 8, 8, 6, 1, 5, and 3, respectively. The polymer PCE1 is a copolymer obtained by copolymerizing a methacrylic acid EO ester monomer (EO repeat number: 25 moles) corresponding to monomer (1) with a methacrylic acid monomer corresponding to monomer (2) at a molar fraction of 70% and a molar fraction of 30%, respectively.

[0063] (Compatibility test) The dispersant was mixed with each additive and water in the ratios shown in Table 2 below to obtain a total of 100 ml of aqueous admixture solutions, which were then filled into 100 ml vials and stored at 5°C, 20°C, and 40°C. The solution stability was visually observed one month and three months after storage, and the compatibility was evaluated according to the following criteria. The evaluation results are shown in Table 2 below. ◎: No separation of ingredients observed even after 3 months 〇: No separation of ingredients was observed after 1 month, but separation of ingredients was observed after 3 months. ×: Separation of ingredients observed after 1 month

[0064] [Table 2]

[0065] Tests on the base concrete for shotcrete were conducted using the concrete mix shown in Table 3 below, and measuring the slump value immediately after mixing (0 minutes), and after 20 minutes, 40 minutes, and 60 minutes. The test results are shown in Table 5 below. In addition, using the mortar mix shown in Table 4 below, shotcrete was prepared using the tools and machines described below, and a shotcrete test was conducted to evaluate adhesion, setting (penetration resistance value), and compressive strength. The test results are shown in Tables 6 and 7 below.

[0066] The mix proportions for the base concrete for shotcrete are shown in Table 3 below. In Table 3, W / C means the water-cement ratio, and s / a means the fine aggregate volume ratio. The cement dispersants and cement additives are shown in Tables 5, 6, and 7, with the mass % of the active ingredients relative to the cement. Cx% solids indicates the mass % of the cement dispersant and cement additive relative to 100% by mass of cement. The amount of accelerator added was Cx 9.0%, which is the mass % of Ac as it is relative to the cement.

[0067] [Table 3]

[0068] [Table 4]

[0069] <Base concrete manufacturing and testing methods> Testing of the base concrete for shotcrete was carried out according to the following procedure.

[0070] (Mixing method) The materials shown in Table 3 were weighed out to a final volume of 30 liters, and then charged into a forced twin-axis mixer with a nominal capacity of 55 liters and mixed using the following procedure: G+1 / 2S+C+1 / 2S was added and the mixture was dry mixed for 10 seconds, then water, dispersant, and any appropriate additives were added and the mixture was mixed for a further 120 seconds. This was used as base concrete for shotcrete and tested.

[0071] Slump test Complies with JIS A 1101.

[0072] Air content test This was in accordance with JIS A 1128. Although the test results for air content are not shown in the table, the target air content was 3.0±0.5% by volume.

[0073] Regarding fluidity retention, if the difference between the slump value after 40 minutes and the slump value immediately after mixing (0 minutes) was less than 6 cm, it was evaluated as excellent fluidity retention and marked with a ◯, if it was 6 cm or more but less than 10 cm, it was evaluated as good fluidity retention and marked with a △, and if it was 10 cm or more, it was evaluated as poor fluidity retention and marked with a ×. Regarding water reduction, if the amount of cement dispersant blended to obtain a slump value of 21±1 cm immediately after mixing (0 minutes) was less than 0.160 mass%, it was evaluated as ◯, and if it was 0.160 mass% or more, it was evaluated as ×.

[0074] <Manufacturing of sprayed mortar, spraying equipment and test method>

[0075] The materials shown in Table 4 were weighed out to a final volume of 40 liters, and then added to a 100-liter NGM-3.5 mixer manufactured by Nagoya Tokai Co., Ltd. according to the following procedure and mixed to prepare a base mortar for spraying. 1 / 2S+C+1 / 2S was added and dry mixed for 10 seconds, then water, dispersant and appropriate additives were added and mixed for a further 120 seconds.The fine aggregate S used in the sprayed mortar was previously passed through a 5mm sieve to remove fine aggregate S of 5mm or larger, and the fluidity immediately after mixing was adjusted so that the 15-pile flow in accordance with JIS R 5201 was 240±10mm.

[0076] (Spraying method) Next, this sprayed mortar was pumped using a mortar pump (Okasan Machinery Co., Ltd., "OKG-10ME" 28S / 100V) at a discharge rate of 0.6-0.7 m³ / hr, and Ac was added using a ring gun (Tomosada Construction Machinery Co., Ltd., "TPG-40R2") and sprayed. Ac was pumped to the ring gun using a quick-setting pump (Heishin Soubi Co., Ltd., "3NY08") at a discharge rate of 9.0% of the cement mass of the mortar. Compressed air (discharge pressure 0.69 MPa) was introduced into the ring gun, and the Ac-added sprayed mortar was sprayed perpendicular to the concrete panel surface at a distance of 0.5 m for 30 seconds onto a concrete panel placed at an angle of approximately 75° from the ground. Adhesion was evaluated visually. A formwork measuring 150 mm in diameter and 75 mm in height was similarly set, and the sprayed mortar was sprayed in the same manner. It was then leveled immediately afterwards and subjected to a setting test. Also, a 40x40x160mm triple formwork was set up in the same manner, sprayed with spray mortar in the same manner, leveled immediately afterwards, sealed and cured for 3 hours or 24 hours, and then subjected to a compressive strength test.

[0077] The test items for the sprayed mortar are as follows. In addition, in all of the following tests, the material temperature was adjusted appropriately so that the temperature after mixing was 18°C.

[0078] Adhesion Test The amount of material that fell off without adhering to the concrete panel surface (rebound amount) was visually observed and rated in descending order as rank 1 (large), rank 2 (slightly large), rank 3 (average), rank 4 (slightly small), and rank 5 (small). Ranks 4 (slightly small) and 5 (small) were rated as passing (◯ rating), while ranks 1 (large), rank 2 (slightly large), and rank 3 (average) were rated as failing (× rating).

[0079] Coagulation test In accordance with JSCE D 102, the penetration resistance of sprayed mortar packed into a formwork measuring φ150 mm x height 75 mm was measured at the intervals shown in Table 7 from 1.5 minutes to 20 minutes after spraying.

[0080] Compression Strength Test In accordance with JIS R 5201, the compressive strength was measured at 3 hours and 24 hours.

[0081] The results of the slump test of the base concrete are shown in Table 5 below, the results of the adhesion test of the sprayed mortar are shown in Table 6 below, the results of the setting test and compressive strength test of the sprayed mortar are shown in Table 7 below, and the overall evaluation results are shown in Table 8 below.

[0082] [Table 5]

[0083] [Table 6]

[0084] [Table 7]

[0085] [Table 8]

[0086] As can be seen from Table 5 above, fluidity retention was achieved in Examples 1 to 3, which contained a cement additive for shotcrete that was a sugar alcohol having 4 to 10 hydroxyl groups or a sugar other than sugar alcohol. On the other hand, fluidity retention was not achieved in Comparative Example 1, which did not contain any cement additive for shotcrete, and Comparative Example 4, which contained glycerol as a cement additive for shotcrete.

[0087] Furthermore, as can be seen from Table 5 above, in Comparative Example 2, in which citric acid was blended as a cement additive for shotcrete, a higher amount of PCE1 was added to obtain the same slump, compared to Comparative Example 1, in which no cement additive for shotcrete was added, indicating that the addition of citric acid inhibits the water-reducing properties of the base concrete.Furthermore, compared to Comparative Example 1, in which no cement additive for shotcrete was added, Examples 1 to 3 showed that a lower amount of PCE1 could be added to obtain the same slump.

[0088] As can be seen from Table 8, Examples 1 to 3, which used a cement admixture for shotcrete containing a cement additive for shotcrete containing a sugar alcohol or a sugar other than sugar alcohol having 4 to 10 hydroxyl groups per molecule and a cement dispersant, produced shotcrete with excellent fluidity, fluid retention, and adhesion without compromising the strength and penetration resistance of the shotcrete. Furthermore, Examples 1 to 3 also had excellent water-reducing properties and compatibility.

[0089] In particular, Example 2, in which sucrose, which is not a reducing sugar, was used as the cement additive for sprayed concrete, showed further improved compatibility compared to Example 1, in which maltose, which is a reducing sugar, was used as the cement additive for sprayed concrete.

[0090] On the other hand, in Comparative Example 1, in which no cement additive for shotcrete was added, neither fluidity retention nor adhesion was obtained, nor was water reduction achieved. Furthermore, in Comparative Example 2, in which citric acid, which has three hydroxyl groups per molecule, was used as the cement additive for shotcrete, neither adhesion nor water reduction was achieved. Furthermore, in Comparative Example 3, in which sodium gluconate was used as the cement additive for shotcrete, adhesion was not achieved. Furthermore, in Comparative Example 4, in which glycerol, a trihydric alcohol, was used as the cement additive for shotcrete, neither fluidity retention nor adhesion was achieved.

Claims

1. A cement additive for shotcrete, comprising at least one hydroxyl group-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, wherein the hydroxyl group-containing organic compound has 4 to 10 hydroxyl groups per molecule.

2. 2. The cement additive for shotcrete according to claim 1, wherein the hydroxyl group-containing organic compound does not contain reducing sugars.

3. 3. The cement additive for shotcrete according to claim 1, wherein the hydroxyl-containing organic compound has 6 to 8 hydroxyl groups in one molecule.

4. 3. The cement additive for shotcrete according to claim 1, wherein the hydroxyl group-containing organic compound comprises a sugar alcohol.

5. A cement admixture for sprayed concrete, comprising: a cement additive for sprayed concrete, the hydroxyl group-containing organic compound containing at least one kind of hydroxyl group selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, the hydroxyl group-containing organic compound having 4 to 10 hydroxyl groups in one molecule; and a cement dispersant.

6. The cement dispersant is an ethylenically unsaturated monomer (1) having a polyalkylene glycol ether chain represented by the following general formula (1): 【Chemistry 1】 (In the formula, R １ , R ２ , R ３ are each independently a hydrogen atom or a methyl group, R ４ represents hydrogen, a methyl group, or an aliphatic hydrocarbon group having 2 to 20 carbon atoms; AO represents an oxyalkylene group having 2 to 4 carbon atoms; a represents an integer of 2 to 350; n represents an integer of 0 to 2; and m represents 0 or 1. Ethylenically unsaturated monomer (2) represented by the following general formula (2): 【Chemistry 2】 (In the formula, R ５ and R ７ are each independently a hydrogen atom or a methyl group; M is a hydrogen atom, a metal atom, an ammonium group or an organic ammonium group; R ６ represents a hydrogen atom or a group represented by -COOM2, and M2 represents a hydrogen atom, a metal atom, an ammonium group, or an organic ammonium group. and a hydrolyzable ethylenically unsaturated monomer (3) represented by the following general formula (3): 【Transformation 3】 (In the formula, R ８ , R ９ , R １０ are each independently a hydrogen atom or a methyl group, R １１ represents an alkyl group or alkoxy group having 2 to 10 carbon atoms, and n represents an integer of 0 to 2.), wherein the ratio (molar fraction) of the number of moles of the monomer (1): the number of moles of the monomer (2): the number of moles of the monomer (3) is 5 to 80%, 0 to 95%, or 0 to 95%, and either one of the molar fractions of the monomer (2) and the monomer (3) is not 0, and the sum of the molar fractions of the monomer (2) and the monomer (3) is 20 to 95%.

7. 7. The cement admixture for sprayed concrete according to claim 5, wherein the content of the cement additive for sprayed concrete in the cement admixture for sprayed concrete is 2% by mass or more and 15% by mass or less.

8. The cement admixture for sprayed concrete according to claim 5 or 6, comprising 0.8 parts by mass or more and 20.0 parts by mass or less of the cement dispersant per 100 parts by mass of the cement additive for sprayed concrete.

9. A sprayed concrete comprising: a cement additive for sprayed concrete, the cement additive comprising at least one hydroxyl group-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, the hydroxyl group-containing organic compound having 4 to 10 hydroxyl groups per molecule; a cement dispersant; cement; water; and an aggregate.

10. A method for producing shotcrete includes adding to base concrete a cement additive for shotcrete, the cement additive comprising at least one hydroxyl group-containing organic compound selected from the group consisting of sugar alcohols and sugars other than sugar alcohols, the hydroxyl group-containing organic compound having 4 to 10 hydroxyl groups per molecule.

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