AU2015265201A1

AU2015265201A1 - Admixture for rapid setting

Info

Publication number: AU2015265201A1
Application number: AU2015265201A
Authority: AU
Inventors: Shinya AKAE; Yutaka Nakajima
Original assignee: Taiheiyo Materials Corp
Current assignee: Taiheiyo Materials Corp
Priority date: 2014-05-30
Filing date: 2015-02-06
Publication date: 2016-12-08
Anticipated expiration: 2035-02-06
Also published as: JPWO2015182170A1; AU2015265201B2; WO2015182170A1; JP6586417B2

Abstract

　The purpose is to provide an admixture for rapid setting with which it is possible to impart an adequate flash-setting property for practical use at low temperature without lowering the ability to actualize early strength and with far less lowering of the flash-setting property than in the past even when applied in a low-temperature environment such as below 10℃ in addition to imparting characteristics such as a rapid-setting property, improved medium- and long-term strength and long-term stability in a hardened state to a cement composition. The present invention relates to an admixture containing (A) 100 parts by mass of calcium aluminate, (B) 10-40 parts by mass of aluminum sulfate, and (C) 7.5-75 parts by mass of one or more selected from alkali metal sulfates and alkaline earth metal sulfates wherein the admixture for rapid setting is characterized by the (B) aluminum sulfate containing 0.03-3.5 mass% of alkali metal-containing substances in terms of alkali metal oxides.

Description

1 TMC0003

Description

[Title of Invention] ADMIXTURE FOR RAPID SETTING

[Technical Field] [0001]

This invention relates to an admixture for rapidly-setting a cement composition such as cement paste, mortar or concrete.

[Background Art] [0002]

In excavation and construction of tunnels, underground space, escarpments or the like, mortar, concrete or the like is sprayed onto natural ground or wall surfaces for reinforcement. In general, a set-accelerator is added to mortar or concrete to be sprayed for finishing the cement setting in a very short time to bond and fix the sprayed material. As the set-accelerator, for example, powdered calcium aluminate, liquid aluminum sulfate or the like is used, and it is known that the combined use of these contributes to an increase in the medium- and long-term strength and longterm stabilization of the hardened state (see, for example, Patent Literature 1). However, only the combined use of both hardly gives a high early strength, and in particular, when the construction is carried out 2 TMC0003 at a low temperature such as below 10°C, the ability to actualize early strength is greatly decreased. It is known that for improving this decrease in the ability to actualize early strength at a low temperature, it is effective to add an alkali metal sulfate to the set-accelerator containing both calcium aluminate and aluminum sulfate (see, for example, Patent Literatures 2, 3) .

[Citation List] [Patent Literature] [0003] [Patent Literature 1] JP-A-H8-4S553 [Patent Literature 2] JP-A-2000-302503 [Patent Literature 3] JP-A-2002-053357 [Summary of Invention] [Technical Problem] [0004]

However, it was found that in this improving method, the flash-setting property tends to be lost as the temperature decreases. In particular, when the spraying was carried out under a construction environment at a low temperature, there was a risk that the sprayed mortar or concrete would not be sufficiently fixed onto the sprayed surface, and would sag or peel off.

[0005] 3 TMC0003

An object of the present invention is to provide an admixture for rapid setting which can impart an adequate flash-setting property for practical use at low temperature while not decreasing the ability to actualize early strength and significantly suppressing the decrease in the flash-setting property than before even when carrying out a construction in a low-temperature environment such as below 10°C, in addition to imparting characteristics such as a rapid-setting property, improved medium- and long-term strength and long-term stability in a hardened state to a cement composition.

[Solution to Problem] [0006]

The present inventors studied to achieve the object, and as a result, found that the object can be generally achieved by an admixture for rapidly setting a cement composition, comprising a particular blending ratio of calcium aluminate, aluminum sulfate and a sulfate of an alkali metal and/or alkaline earth metal, in which aluminum sulfate comprising a specific different component is used as the aluminum sulfate, and thus completed this invention.

[0007]

Namely, the present invention provides the following [1] to [9] .

[0008] 4 TMC0003 [1] An admixture for rapid setting, comprising (A) 100 parts by mass of calcium aluminate, (B) from 10 to 40 parts by mass of aluminum sulfate, and (C) from 7.5 to 75 parts by mass of one or more selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, wherein the component (B) aluminum sulfate comprises from 0.03 to 3.5 mass% of alkali metal-containing substances in terms of alkali metal oxides.

[2] The admixture for rapid setting according to [1], wherein a content of the component (B) is from 15 to 35 parts by mass.

[3] The admixture for rapid setting according to [1] or [2], wherein a content of the component (C) is from 7.5 to 55 parts by mass.

[4] The admixture for rapid setting according to any of [1] to [3], wherein the component (A) is calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of 1.8 or more and a percentage of glass content of 80% or more.

[5] A cement composition comprising the admixture for rapid setting according to any of [1] to [4].

[6] The cement composition according to [5], wherein a content of the admixture for rapid setting is from 7 to 20 parts by mass based on 100 parts by mass of cement.

[7] A shotcrete composition comprising the admixture for rapid setting according to any of [1] to [4] . 5 TMC0003 [8] The shotcrete composition according to [7] , wherein a content of the admixture for rapid setting is from 7 to 20 parts by mass based on 100 parts by mass of cement.

[9] The shotcrete composition according to [7], wherein a content of the admixture for rapid setting is from 11 to 15 parts by mass based on 100 parts by mass of cement.

[Advantageous Effects of Invention] [0009]

According to the present invention, when a cement composition such as cement paste, mortar or concrete is sprayed for construction, the decline of flash-setting property is by far improved even under a low-temperature environment such as below 10°C, and thus the bonding and fixation to the sprayed surface can be securely conducted. Also, a high early strength can be actualized, and in addition, a satisfactory hardened state is kept maintained without decreasing the ability to actualize medium- and long-term strength, and thus a stable hardened state can be exhibited for a long time.

[Description of Embodiments] [0010]

The admixture for rapid setting of the present invention comprises (A) 100 parts by mass of calcium aluminate, (B) from 10 to 40 parts by mass of aluminum sulfate, and (C) from 7.5 to 75 parts by mass of one or 6 TMC0003 more selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and wherein the (B) aluminum sulfate comprises from 0.03 to 3.5 mass% of alkali metal-containing substances in terms of alkali metal oxides.

[0011] (A) Calcium aluminate (the component (A)) used in the admixture for rapid setting of the present invention may be any hydration active substance which has a crystalline or largely vitrified structure, and consists of CaO and Al203 as chemical components, or may be any of a compound, solid solution or vitreous substance containing other chemical components in addition to CaO and Al203 as the contained chemical components, or a mixture of these as long as it does not substantially impair the effects of the present invention. Examples of the former include 12Ca0-7Al203, Ca0-Al203, 3Ca0-Al203, and Ca0-2A1203. Examples of the latter include 4Ca0*3Al203-S03, HCa0*7Al203-CaF2, and Na20-8Ca0-3Al203. Both are not limited to the examples listed. Preferably, calcium aluminate having a content molar ratio of CaO to A1203 (Ca0/Al203) of 1.8 or more is favorable because it has a high hydration activity, and a higher rapid-setting property can be possibly obtained. More preferably, calcium aluminate having a content molar ratio of CaO to A1203 (Ca0/Al203) of 2.0 or more. Also, calcium aluminate having a content molar ratio of CaO to Al203 (CaO/Al203) 7 TMC0003 of 2.3 or less is preferred. More specifically, calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of from 1.8 to 2.3 is preferred, and one with the content molar ratio of from 2.0 to 2.3 is further preferred.

Calcium aluminate contributes as a rapid-setting property-imparting component which causes setting at an early stage after pouring water to a cement composition. The higher the percentage of glass content of calcium aluminate is, the higher the rapid-setting property is easily imparted, and thus calcium aluminate having a percentage of glass content of 80% or more is preferred, but the percentage of glass content is not limited to this. More preferably, amorphous calcium aluminate (where the percentage of glass content is substantially 100%) is used. As for the percentage of glass content, using a powder X-ray diffraction apparatus, the masses of each minerals contained in calcium aluminate having a mass Ml are quantified by an internal standard method or the like, the total mass (M2) of the quantified mineral phase contained is calculated, and considering the remainder as a pure glass phase, the percentage of glass content is obtained by the following expression.

Percentage of glass content (%) = (1 - M2/Ml) x 100

Preferred calcium aluminate has a content molar ratio of Ca0/Al203 (Ca0/Al203) of 1.8 or more, more preferably 2.0 or more, further preferably from 1.8 to δ TMC0003 2.3, further preferably from 2.0 to 2.3, and a percentage of glass content of 80% or more, more preferably from 80 to 100%.

[0012] A method of producing largely vitrified calcium aluminate is not particularly limited. By way of example, calcium aluminate having a desired percentage of glass content can be produced by heating a mixture containing CaO or a raw material to be a CaO source and AI2O3 or a raw material to be an A1203 source in a predetermined content molar ratio of CaO and Al203 until it melts, and then rapidly cooling the resultant in any manner desirably other than rapid cooling in water and rapid cooling by water sprinkling. The rapidly cooled calcium aluminate may be ground and classified to a Blaine specific surface area of about 4000 cmz/g or more, considering the grinding cost, of about from 4000 to 7000 cm2/g, in order to obtain a desired reactivity.

[0013] (B) Aluminum sulfate (the component (B)) used in the admixture for rapid setting of the present invention is characterized in that it comprises alkali metal-containing substances, and its content is from 0.03 to 3.5 mass% in terms of alkali metal oxides (excluding an alkali metal sulfate when contained). Aluminum sulfate contributes to acceleration of early setting of a hydraulic substance such as cement, and in particular, 9 TMC0003 aluminum sulfate comprising alkali metal-containing substances naturally gives a flash-setting property at around, normal temperature, and can impart an adequate flash-setting property even under a low-temperature environment such as below about 10°C, also enabling prevention of a significant decrease in early strength at such a low temperature. When the content of alkali metal-containing substances in aluminum sulfate is less than 0.03 mass% in terms of oxides, a flash-setting property is hardly actualized under a low-temperature environment, and the ability to actualize early strength may be largely decreased in some case, thus unfavorable. On the other hand, when the content of alkali metal-containing substances is more than 3.5 mass% in terms of oxides, the accelerating effect on early setting is reduced, and a flash-setting property may be hardly actualized in some cases independently of temperature environments, thus unfavorable. The above effect can be actualized by using aluminum sulfate comprising a predetermined amount of the alkali metal-containing substances, and thus the effect as described above cannot be sufficiently obtained even when aluminum sulfate not comprising the alkali metal-containing substances is added and mixed with, for example, an alkali metal oxide such as potassium oxide or lithium oxide as a commercially-available reagent later. 10 TMC0003 A preferred content of the alkali metal-containing substances in aluminum sulfate is, excluding an alkali metal sulfate when it is contained, from 0.1 to 1.2 mass%, and more preferably from 0.2 to 1.0 mass% in terms of oxides .

Here, the alkali metal-containing substance is not particularly limited as long as it is a substance comprising any one or more of Na, K, Li as a constituting component, and may be any of elemental alkali metals, alkali metal compounds, alkali metal-containing solid solutions, alkali metal-containing amorphous materials or the like, or may be a substance having a combination of any of these. Specifically, examples thereof include alkali metals, alkali metal oxides (such as Na20, K20,

Li02) , alkali metal hydroxides, alkali metal carbonates, solid solutions of alkali metal oxides in aluminum sulfate. Preferably, alkali metal sulfates are not included.

[0014]

Any of aluminum sulfate having crystallization water and anhydrous one may be used. Preferably, one having crystallization water is favorable, and when this is used for a cement composition for spraying, it becomes easier to prevent rebound when spraying.

Aluminum sulfate comprising alkali metal-containing substances suitable for this use originates from its raw material for production, and is obtained by, for example, 11 TMC0003 using, as a raw material, bauxite, aluminum sludge or gibbsite all comprising alkali metal compounds as impurities and treating it with sulfuric acid diluted in distilled water, but is not limited to the examples described.

[0015]

The content of (B) aluminum sulfate (the component (B)) in the admixture for rapid setting of the present invention is from 10 to 40 parts by mass, more preferably from 15 to 35 parts by mass, further preferably from 15 to 30 parts by mass of aluminum sulfate comprising a predetermined amount of the alkali metal-containing substances based on 100 parts by mass of calcium aluminate. When the content of (B) aluminum sulfate is less than 10 parts by mass, an adequate early setting property cannot be obtained, and when the content is more than 40 parts by mass, the amount of calcium aluminate is relatively insufficient, reducing the early setting property, thus unfavorable.

[0016]

The admixture for rapid setting of the present invention comprises (C) one or more selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates. At least one of alkali metal sulfates or alkaline earth metal sulfates may be contained, but any two or more of these may be contained. Preferably, an alkaline earth metal sulfate, or an 12 TMC0003 alkaline earth metal sulfate and an alkali metal sulfate are contained. Examples of alkali metals which form their sulfates include lithium, sodium, and potassium, and examples of alkaline earth metals include calcium, magnesium, strontium, and barium.

Suitably, using lithium sulfate, for example, as an alkali metal sulfate, and anhydrous gypsum, for example, as an alkaline earth metal sulfate, any one or both of these may be used. The blending mass ratio of both when combined is not limited. By inclusion of the component (G), the ability to actualize medium- and long-term strength can be improved, and a stable hardened state can be maintained for a long time.

[0017]

The content of the component (C) in the admixture for rapid setting of the present invention is, in total, from 7.5 to 75 parts by mass, more preferably from 7.5 to 55 parts by mass, further preferably from 30 to 50 parts by mass based on 100 parts by mass of the content of calcium aluminate.

When the component (C) comprises an alkali metal sulfate (Cl) and an alkaline earth metal sulfate (C2) at the same time, the content proportion of the both is not limited, but more preferably, the content proportion of the both is from 1/4 to 7/3 in mass ratio (C1/C2). When the content of the component (C) is less than 7.5 parts by mass, the ability to actualize medium- and long-term 13 TMC0003 strength is insufficient, on the other hand, when the content is more than 75 parts by mass, the amounts of calcium aluminate and aluminum sulfate are relatively insufficient, reducing the early setting property, thus unfavorable .

[0018]

The admixture for rapid setting of the present invention may comprise a component other than the components mentioned above as long as it does not impair the effects of the present invention. Examples of such component include, but not limited to, a carbonate of an alkali metal not contained in the aluminum sulfate, an aluminate of an alkali metal and various setting modifiers which can be used for cement. When the carbonate or aluminate of the alkali metal is contained, a preferred content thereof is from 5 to 100 parts by mass based on 100 parts by mass of the content of calcium aluminate. This content makes it easier to improve the rapid-setting property at very early stage immediately after contacting with water, or the bonding property at a very early stage when using this in a shotcrete composition.

[0019]

By using the admixture for rapid setting of the present invention, a cement composition, for example, a shotcrete composition can be prepared which has a favorable early setting property, ability to actualize 14 TMC0003 early strength and workability. To prepare a cement composition such as a shotcrete composition, it is recommended that the admixture for rapid setting of the present invention be blended and used in an amount of preferably from 7 to 20 parts by mass, more preferably from 9 to 15 parts by mass, further preferably from 11 to 15 parts by mass based on 100 parts by mass of cement in view of easily obtaining a cement composition having a favorable early setting property, ability to actualize early strength and workability. In particular, to prepare a shotcrete composition suitable for spraying under a low-temperature environment, it is recommended that the admixture for rapid setting of the present invention be blended and used in an amount of preferably from 9 to 15 parts by mass, more preferably from 11 to 15 parts by mass, based on 100 parts by mass of cement. As for a cement composition in which the admixture for rapid setting of the present invention is blended and used, other admixtures or aggregate which can be used in mortar and concrete can be concurrently used depending on the intended use. The admixtures used concurrently is not particularly limited, and examples thereof include thickening agents for preventing dust generation, water reducers, in particular high range water reducers for improving the fluidity of mortar and concrete to be sprayed.

[0020] 15 TMC0003

Examples of the cement used here include Portland cement such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, ultra-high-early-strength Portland cement, and various blended cements incorporating such component as fly ash or blast furnace slag into these Portland cements. Of these, ordinary Portland cement, high-early-strength Portland cement are more preferable.

[0021]

As the aggregate, any of fine aggregate, and coarse aggregate may be used. Examples of the fine aggregate include river sand, mountain sand, lime sand, and silica sand, and examples of the coarse aggregate include river gravel, mountain gravel, and lime gravel.

[0022]

Examples of a spraying method using a shotcrete composition include a method of separately pumping a powdered or slurry admixture for rapid setting and cement concrete, merging and mixing them to spray the resultant as rapid-setting concrete.

[0023]

Preferred aspects of the present invention will be mentioned below. <1> An admixture for rapid setting, comprising (A) 100 parts by mass of calcium aluminate, (B) from 10 to 40 parts by mass of aluminum sulfate, and (C) from 7.5 to 75 parts by mass of one or more selected from the group 16 TMC0003 consisting of alkali metal sulfates and alkaline earth metal sulfates, wherein the (B) aluminum sulfate comprises from 0.03 to 3.5 mass% of alkali metal-containing substances in terms of alkali metal oxides.

[0024] <2 > The admixture for rapid setting according to <1>, wherein the component (A) is a hydration active substance which has a crystalline or has a largely vitrified structure, and consists of CaO and Al203 as chemical components, preferably one or more selected from the group consisting of 12CaO7Al203, CaOAl203, 3Ca0-Al203, Ca0-2A1203, 4Ca0-3Al203-S03, HCa0-7Al203-CaF2, and Na20-8Ca0-3Al203 . <3> The admixture for rapid setting according to <1> or <2>, wherein the component (A) is preferably calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of 1.8 or more, more preferably calcium aluminate having a content molar ratio of CaO to A1203 (Ca0/Al203) of 2.0 or more, further preferably calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of 2.3 or less, and further preferably calcium aluminate having a content molar ratio of CaO to A1203 (Ca0/Al203) of from 1.8 to 2.3, further preferably calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of from 2.0 to 2.3. <4> The admixture for rapid setting according to any of <1> to <3>, wherein the component (A) preferably has a 17 TMC0003 percentage of glass content of 80% or more, and more preferably a glass content of from 80 to 100%. <5> The admixture for rapid setting according to any of <1> to <4>, wherein the component (A) is calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of 1.8 or more, preferably from 1.8 to 2.3, and a percentage of glass content of 80% or more, preferably from 80 to 100%. <6> The admixture for rapid setting according to any of <1> to <5>, wherein the component (A) is calcium aluminate having a Blaine specific surface area of 4000cm2/g or more, preferably from 4000 to 7000cm2/g.

[0025] <7> The admixture for rapid setting according to any of <1> to <6>, wherein a content of the component (B) is from 15 to 35 parts by mass, preferably from 15 to 30 parts by mass based on 100 parts by mass of the component (A) . <8> The admixture for rapid setting according to any of <1> to <7>, wherein the component (B) is aluminum sulfate comprising from 0.1 to 1.2 mass%, preferably from 0.2 to 1.0 mass% of alkali metal-containing substances in terms of alkali metal oxides. <9> The admixture for rapid setting according to any of <1> to <8>, wherein the alkali metal-containing substance contained in the (B) aluminum sulfate is a substance comprising one or more of Na, K, and Li as a constituting 18 TMC0003 component, preferably one or more selected from the group consisting of an elemental alkali metal, an alkali metal compound, an alkali metal-containing solid solution and an alkali metal-containing eutectic material, more preferably one or more selected from the group consisting of an alkali metal, alkali metal oxide (such as Na20, K20, Li02) , alkali metal hydroxide, alkali metal carbonate, and solid solution of alkali metal oxide in aluminum sulfate. <10> The admixture for rapid setting according to any of <1> to <9>, wherein a content of the component (C) is from 7.5 to 55 parts by mass, preferably from 30 to 50 parts by mass based on 100 parts by mass of the component (A) . <11> A cement composition comprising the admixture for rapid setting according to any of <1> to <10>. <12> The cement composition according to <11>, wherein a content of the admixture for rapid setting is from 7 to 20 parts by mass, preferably from 9 to 15 parts by mass, further preferably from 11 to 15 parts by mass based on 100 parts by mass of cement. <13> A shotcrete composition comprising the admixture for rapid setting according to any of <1> to <10>. <14> The shotcrete composition according to <13>, wherein a content of the admixture for rapid setting is from 7 to 20 parts by mass, preferably from 9 to 15 parts by mass, 19 TMC0003 further preferably from 11 to 15 parts by mass based on 100 parts by mass of cement.

[Examples] [0026]

The present invention will be specifically described by Examples below, but the present invention is not limited to Examples described.

[0027]

Admixtures for rapid setting were prepared by charging materials represented by abbreviations below into a Henschel-type mixer in blending proportions in Table 1, and dry blending the resultants for about 10 minutes. The admixtures for rapid setting prepared were stored in dry containers until used. Note that each of alkali metal-containing substances (in terms of oxides) and other components (including impurities) contained in the aluminum sulfate are considered as substantially not contained for those having the contents of less than 0.01 mass% by chemical analysis of aluminum sulfate in terms of anhydride, and only components contained in an amount of 0.01 mass% or more are explicitly indicated. The presence of a crystal phase of alkali metal oxides in the aluminum sulfate was confirmed by powder X-ray diffraction.

[0028] 20 TMC0003 CA1,- amorphous calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of 2.2 {Blaine specific surface area: 5100 cm2/g) CA2; amorphous calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of 1.8 (Blaine specific surface area: 5900 cm2/g) CA3; calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of 2.2 and a percentage of glass content of 80% (Blaine specific surface area: 5100 cm2/g) CA4; amorphous calcium aluminate having a content molar ratio of CaO to Al203 (Ca0/Al203) of 1.7 (Blaine specific surface area: 5900 cm2/g) AS1; aluminum sulfate comprising 0.98 mass! of K20 (hexadecahydrate) *1 AS2; aluminum sulfate comprising 3.02 mass% of K20 (hexadecahydrate) *1 AS3; aluminum sulfate comprising 0.05 mass% of K20 (hexadecahydrate) *1 AS4; aluminum sulfate comprising 1.02 mass% of Na20 (hexadecahydrate) *2 AS5; anhydrous aluminum sulfate comprising 0.50 mass% of Na20 *2 AS6; aluminum sulfate having a total content of components other than aluminum sulfate hydrate of less than 0.01 mass! (hexadecahydrate) AS7; anhydrous aluminum sulfate comprising 6.41 mass% of K20 * 1 21 TMC0003 AS8; anhydrous aluminum sulfate comprising 0.03 mass% of K20 *1 CS; anhydrous gypsum NS; anhydrous sodium sulfate , KO; potassium oxide powder (maximum particle size: about 55 μπι, mean particle size: about 20 μπι)

Notes : *1 ... The total content of alkali metal-containing substances other than K20 is less than 0.01 mass% *2 ... The total content of alkali metal-containing substances other than Na20 is less than 0.01 mass% [0029] 22 TMC0003 [Table 1]

Admixture for rapid setting No. Amount blended (parts by mass) Remarks Calcium aluminate Aluminum sulfate Anhydrou s gypsum CS Anhydrous sodium sulfate NS Potassium oxide powder KO Type Amount Type Amount QM1 CA1 100 AS1 20 35 15 0 Inventive product QM2 CA2 100 AS1 20 35 15 0 Inventive product QM3 CA1 100 AS1 10 35 15 0 Inventive product QM4 CA1 100 AS1 15 35 15 0 Inventive product QM5 CA1 100 AS1 30 35 15 0 Inventive product QM6 CA1 100 AS1 40 35 15 0 Inventive product QM7 CA1 100 AS1 20 15 35 0 Inventive product QM8 CA1 100 AS1 20 55 0 0 Inventive product QM9 CA1 100 AS1 20 7.5 0 0 Inventive product QM10 CA1 100 AS2 20 35 15 0 Inventive product QM11 CA1 100 AS3 20 35 15 0 Inventive product QM12 CA1 100 AS4 20 35 15 0 Inventive product QM13 CA1 100 AS5 20 35 15 0 Inventive product QM14 CA1 100 (None) 0 35 15 0 Reference product QM15 CAi 100 AS1 20 0 0 0 Reference product QM16 CA1 100 AS6 20 35 15 0 Reference product QM17 CAI 100 AS7 20 35 15 0 Reference product QM18 CAI 100 AS6 20 35 15 0.98 Reference product QM19 CAI 100 AS1 15 60 15 0 Inventive product QM20 CAI 100 AS8 20 35 15 0 Inventive product QM21 CA3 100 AS1 20 35 15 0 Inventive product QM22 CA4 100 AS1 20 35 15 0 Inventive product [0030]

To a bottomed cylindrical container with an internal volume of 500 cc, 400 g of ordinary Portland cement and 200 g of water were charged, and mixed for about 1 minute with a hand mixer, and then allowed to stand still indoors as kept at a temperature of 8°C (+0.5°C, hereinafter the error range with respect to the 23 TMC0003 temperature is the same unless otherwise specified) for about 30 minutes. After standing, the mixture was kneaded with the hand mixer for about 1 minute, and 48g of the admixture for rapid setting (QM1-22) was added to this kneaded product, and stirred for 5 seconds to prepare a cement composition paste (P1-P22); alternatively 44g of the admixture for rapid setting (QM1) was added and stirred for 5 seconds to prepare a cement composition paste (P23); or 60g of the admixture for rapid setting (QM1) was added and stirred for 5 seconds to prepare a cement composition paste (P24).

Then, the flash-setting property of the admixture for rapid setting was evaluated by measuring the Proctor penetration resistance value at 8°C of the cement composition paste at 30 seconds after adding the admixture for rapid setting. The Proctor penetration resistance values at 8°C were also measured for cement composition pastes obtained in the same manner at 60 seconds and 5 minutes after adding the admixture for rapid setting. At the same time, a cement composition paste (P25) not containing the admixture for rapid setting was prepared in the same manner, and its Proctor penetration resistance values at 8°C at 30 seconds, 60 seconds and 5 minutes after finishing the kneading were measured. The method of measuring the Proctor penetration resistance value conforms to Japan Society of Civil Engineers, Standard Specifications for Concrete 24 TMC0003

Structures "Quality Standards for Set Accelerators for Shotcrete" Annex "Method of Measuring Time of Flash-Setting of Mortar by Penetration Resistance," and used Proctor needles having a cross-sectional area of 0.125 cm2. The above measurement results are shown in Table 2.

[0031] [Table 2]

Cement composition paste No. Admixture for rapid setting added Proctor penetration resistance value (N/mm2) Bonding property Curing stability Remarks After 30 seconds After 60 seconds After 5 minutes PI QM1 2.0 6.5 12.5 Good Good Inventive product P2 QM2 1.2 5.1 11.5 Good Good Inventive product P3 QM3 1.2 5.0 12.0 Good Good Inventive product P4 QM4 1.3 5.9 12.2 Good Good Inventive product P5 QM5 1.6 6.0 12.5 Good Good Inventive product P6 QM6 1.2 6.0 11.8 Good Good Inventive product P7 QM7 1.8 6.0 11.6 Good Good Inventive product P8 QM8 1.2 5.0 11.5 Good Good Inventive product P9 QM9 1.6 5.5 12.0 Good Good Inventive product P10 QM10 1.4 5.0 11.5 Good Good Inventive product Pll QM11 1.2 5.1 12.6 Good Good Inventive product P12 QM12 1.4 5.6 12.2 Good Good Inventive product P13 QM13 1.5 5.5 12.0 Good Good Inventive product P14 QM14 1.2 4.6 8.5 Poor - Reference product P15 QM15 0.8 2.9 6.4 Poor - Reference product P16 QM16 0.5 3.0 11.3 Poor - Reference product P17 QM17 1.5 3.9 11.5 Good Good Reference product P18 QM18 0.6 3.2 11.0 Poor - Reference product P19 QM19 1.0 4.9 11.2 Good Good Inventive product P20 QM20 1.1 5.0 12.4 Good Good Inventive product P21 QM21 1.3 5.4 11.9 Good Good Inventive product P22 QM22 1.0 4.8 11.5 Good Good Inventive product P23 QM1 1.6 5.2 11.7 Good Good Inventive product P24 QM1 2.0 5.8 12.4 Good Good Inventive product P25 (None) 0 0 0 Poor - Reference product 25 TMC0003 [0032]

For comparisons between temperature conditions, 400 g of ordinary Portland cement and 200 g of water were charged into a bottomed cylindrical container with an internal volume of 500 cc, mixed with a hand mixer for about 1 minute, and then allowed to stand still indoors at a temperature of 20°C for about 30 minutes. After standing, the mixture was kneaded with the hand mixer for about 1 minute, and 28 g of the admixture for rapid setting (QM1, QM16 or QM18) was added to this kneaded product, stirred for 5 seconds to prepare a cement composition paste (P30-P32); alternatively 48 g of the admixture for rapid setting (QM1, QM5, or QM7) was added and stirred for 5 seconds to prepare a cement composition paste (P33-P35) ,- or 80 g of the admixture for rapid setting (QM1) was added and stirred for 5 seconds to prepare a cement composition paste (P36). The fabricated cement composition paste was measured for its Proctor penetration resistance value at 20°C at 30 seconds, 60 seconds and 5 minutes after adding the rapid-setting admixture by the same method as described above except that the temperature was 20°C. These results are shown in Table 3.

[0033] 26 TMC0003 [Table 3]

Cement composition paste No. Admixture ibr rapid setting added Proctor penetration resistance value (N/mm2) Bonding property Curing stability Remarks After 30 seconds After 60 seconds After 5 minutes P30 QM1 1.9 6.8 17.8 Good Good Inventive product P31 QM16 0.8 4.1 16.5 Poor - Reference product P32 QM18 0.9 4.3 14.8 Poor - Reference product P33 QM1 3.9 13.5 28.0 Good Good Inventive product P34 QM5 3.5 13.4 27.2 Good Good Inventive product P35 QM7 3.6 13.7 27.0 Good Good Inventive product P36 QM1 >30 >30 >30 Good Good Inventive product [0034]

Furthermore, 400 g of ordinary Portland cement and 200 g of water were charged into a bottomed cylindrical container with an internal volume of 500 cc, mixed with a hand mixer for about 1 minute, and then allowed to stand still in the indoors kept at a temperature of 30°C for about 30 minutes. After this standing, the mixture was kneaded with the hand mixer for about 1 minute, and 48 g of the admixture for rapid setting QM1 was added as an admixture for rapid setting thereto, and stirred for 5 seconds to prepare a cement composition paste (P40).

This cement composition paste (P40) was measured for its Proctor penetration resistance value at 30°C at 30 seconds, 60 seconds and 5 minutes after adding the rapidsetting admixture by the same method as described above. The measurement results were: 6.3 N/mm2 at 30 seconds, 15.2 N/mm2 at 60 seconds, and 29.3 N/mm2 at 5 minutes after the addition of the rapid-setting admixture. 27 TMC0003 [0035]

The above cement composition paste (P1-P25) was transferred to a sprayer (commercially available mortar gun) immediately after preparation, and under a temperature environment of 8°C, it was sprayed against a smooth concrete wall surface with sides of 2 m installed vertically on the ground at a location 150 cm distant from the sprayer. At about 3 minutes after finishing the spraying, the bonding property was evaluated by visual observation. That is, the bonding property was judged to be "Good" when the cement composition paste sprayed onto the wall surface remained bonded without sagging, peeling off or abrasion. The bonding property was judged to be "Poor" for all having other conditions. Furthermore, the smooth wall surface which had been sprayed with the cement composition paste having the bonding property judged as "Good" was left to stand indoors while connecting to outside air at an average temperature of 20°C during the period for 60 days, and the sprayed wall surface was again visually observed. The curing stability was judged to be "Good" for the cement composition paste sprayed onto the wall surface which cured without peeling off or abrasion, and had no crack on the surface. The curing stability was judged to be "Poor" for those having other states. These results are also shown in Table 2.

[0036] 28 TMC0003

Part of the cement composition paste (P30-P36) was transferred to the same sprayer as above immediately after preparation, and -under a temperature environment of 20°C, it was sprayed against a smooth concrete wall surface with sides of 2 m installed in the same manner as above. The bonding property and curing stability of the cement composition paste sprayed onto the wall surface were evaluated by the same method as above. These results are also shown in Table 3.

[0037]

Furthermore, the cement composition paste P40 was transferred to the same sprayer as described above after preparation, and sprayed against a smooth concrete wall surface with sides of 2 m installed in the same manner as above under ‘a temperature environment of 3 0°C. The bonding property and curing stability of the cement composition paste sprayed onto the wall surface was evaluated by the same method as above, and both were "Good." [0038]

Into a Hobart mixer with an internal volume of about 4.7 liters, were charged 450 g of ordinary Portland cement, 1350 g of JIS standard sand (silica sand having a maximum particle size of 2 mm and a content for particle size of less than 0.08 mm being less than 2%) and 225 g of water at a time. The mixture was mixed for 1 minute, and then allowed to stand still indoors at a temperature 29 TMC0003 adjusted to 20°C for 30 minutes. After the standing time, the mixture was mixed again in the Hobart mixer for about 1 minute, and 40 g of the admixture for rapid setting (QM1-QM22) was added to this, and mixed for additional 10 seconds to prepare a cement mortar. The cement mortar was filled into a cuboid mold having inside dimensions of 40 x 40 x 160 mm immediately after preparation, and allowed to stand indoors at a temperature adjusted to 20°C as it was. The filled material was removed from the mold when a predetermined age was reached to make a sample. The unconfined compressive strengths at 20°C of the sample at Age Day 1, Day 7 and Day 28 were measured with an Amsler-type compressive strength testing machine to evaluate the ability to actualize strength at normal temperature. For comparison purposes, the unconfined compressive strengths at 20°C were measured by the same method as above for a cement mortar (M25) prepared by the same method as above except that no admixture for rapid setting was added. These measurement results are shown in Table 4.

[0039] [Table 4] 30 TMC0003

Cement mortar No. Admixture for rapid setting added Unconfined compressive strengths at 8eC (N/mm2) Unconfined compressive strengths at 20°C (N/mm2) Remarks Age Day 1 Age Day 7 Age Day 28 Age Day 1 Age Day 7 Age Day 28 Ml QM1 18.0 30.0 35.0 22.5 40.0 44.0 Inventive product M2 QM2 16.5 29.5 38.0 20.5 42.0 44.0 Inventive product M3 QM3 16.5 23.5 30.0 18.5 32.5 38.0 Inventive product M4 QM4 15.5 27.0 31.0 17.5 35.0 40.0 Inventive product M5 QM5 16.0 28.0 31.0 20.0 35.5 40.0 Inventive product M6 QM6 18.0 25.5 29.0 20.5 32.0 39.0 Inventive product M7 QM7 20.0 27.5 31.0 25.0 36.0 39.5 Inventive product M8 QM8 15.5 26.0 32.0 19.0 36.0 42.0 Inventive product M9 QM9 15.0 24.5 30.0 17.5 36.0 42.0 Inventive product M10 QM10 17.0 28.0 33.5 21.0 38.0 42.0 Inventive product Mil QM11 16.0 26.5 33.0 19.5 36.5 41.0 Inventive product M12 QM12 17.5 27.5 32.0 22.5 35.5 39.5 Inventive product M13 QM13 15.5 25.5 33.5 20.5 37.5 41.5 Inventive product M14 QM14 11.5 21.5 27.0 15.5 30.0 33.0 Reference product M15 QM15 12.5 21.5 25.0 14.0 28.0 31.0 Reference product M16 QM16 14.0 27.5 33.0 17.5 37.5 42.0 Reference product M17 QM17 12.0 21.0 23.0 14.0 25.0 30.0 Reference product M18 QM18 13.5 27.0 32.0 16.5 35.5 40.5 Reference product M19 QM19 15.5 26.0 31.5 19.0 35.5 42.5 Inventive product M20 QM20 17.0 30.0 34.0 21.5 40.5 43.5 Inventive product M21 QM21 16.5 29.0 37.0 21.0 42.5 44.0 Inventive product M22 QM22 16.0 29.0 36.5 20.0 41.5 43.5 Inventive product M25 (None) 10.0 24.0 42.0 15.0 43.5 53.5 Reference product [0040] A cement mortar prepared in the same formulation and procedure as above was filled in a cuboid mold having inside dimensions of 40 x 40 x 160 mm immediately after preparation, and allowed to stand indoors at a temperature adjusted to 8°C as it was. The filled material was removed from the mold when a predetermined age period was reached to make a sample. The unconfined 31 TMC0003 compressive strengths at 8°C of the sample at Day 1, Day 7 and Day 28 were measured with the Amsler-type compressive strength testing machine to evaluate the ability to actualize strength at low temperature. For comparison, the unconfined compressive strengths at 8°C were measured by the same method as above for a cement mortar prepared by the same method as above except that no admixture for rapid setting was added. These measurement results are also shown in Table 4.

[0041]

It is seen from Table 2 that the conventional set-accelerator (QM16) has a significantly reduced Proctor penetration resistance value and hardly imparts a flashsetting property at low temperature, but the admixtures for rapid setting of the present invention have Proctor penetration resistance values substantially larger than that of the conventional product even at a low temperature (8°C), and the decrease in the flash-setting property at low temperature is significantly improved. This applies to the bonding property under low temperature, and it is seen from Table 2 and Table 3 that the cement composition pastes using the admixtures for rapid setting of the present invention all have good bonding properties not inferior to the bonding properties at normal temperature (20°C) . In addition, it is seen from Table 4 that the cement mortars containing the admixtures for rapid setting of the present invention 32 TMC0003 suppress significantly the decrease in the compressive strengths at low temperature, in particular, the compressive strengths at early age than the cement mortars containing the admixtures for rapid setting outside the present invention.

Claims

Claims [Claim 1] An admixture for rapid setting, comprising (A) 100 parts by mass of calcium aluminate, (B) from 10 to 40 parts by mass of aluminum sulfate, and (C) from 7.5 to 75 parts by mass of one or more selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, wherein the component (B) comprises from 0.03 to 3.5 mass% of alkali metal-containing substances in terms of alkali metal oxides. [Claim
2] The admixture for rapid setting according to claim 1, wherein a content of the component (B) is from 15 to 35 parts by mass. [Claim
3] The admixture for rapid setting according to claim 1 or 2, wherein a content of the component (C) is from 7.5 to 55 parts by mass. [Claim
4] The admixture for rapid setting according to any one of claims 1 to 3, wherein the component (A) is calcium aluminate having a content molar ratio of CaO to A1203 (Ca0/Al203) of 1.8 or more and a percentage of glass content of 80% or more. [Claim
5] A cement composition comprising the admixture for rapid setting according to any one of claims 1 to 4. [Claim
6] The cement composition according to claim 5, wherein a content of the admixture for rapid setting is from 7 to 20 parts by mass based on 100 parts by mass of cement. [Claim
7] A shotcrete composition comprising the admixture for rapid setting according to any one of claims 1 to 4. [Claim
8] The shotcrete composition according to claim 7, wherein a content of the admixture for rapid setting is from 7 to 20 parts by mass based on 100 parts by mass of cement. [Claim
9] The shotcrete composition according to claim 7, wherein a content of the admixture for rapid setting is from 11 to 15 parts by mass based on 100 parts by mass of cement.