JP2012140293A - Quick-hardening cement admixture for low temperature and quick-hardening cement composition for low temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quick-hardening cement admixture for low temperature, which is mixed and kneaded into a cement composition to impart excellent potlife, i.e. 60 min or longer, a compressive strength of 5 N/mmor higher at a material age of 3 hr and a compressive strength of 30 N/mmor higher at a material age of 24 hr, even when the material temperature of the mixed cement composition and the environmental temperature are 5°C, and to provide a quick-hardening cement composition for low temperature, which is excellent in potlife, i.e. 60 min or longer, has a compressive strength of 5 N/mmor higher at a material age of 3 hr and has a compressive strength of 30 N/mmor higher at a material age of 24 hr, even when the material temperature and the environmental temperature are 5°C.SOLUTION: The quick-hardening cement admixture for low temperature comprises calcium aluminates with a prescribed percentage of glass content, gypsum, alkali metal sulfate, alkali metal carbonate and a setting retarder. Preferably, the calcium aluminates comprise crystalline calcium aluminates and amorphous calcium aluminates.

Description

The present invention relates to a low temperature rapid hardening cement admixture. Specifically, even when the material temperature and environmental temperature of the mixed cement composition are 5 ° C., the compressive strength at the age of 3 hours exceeds 5 N / mm ² and the compressive strength at the age of 24 hours is 30 N / mm ² or more. In spite of this, the present invention relates to a rapid hardening cement admixture for low temperatures. The present invention also relates to a low temperature rapid hardening cement composition. Specifically, even when the material temperature and the environmental temperature are 5 ° C., the compressive strength at the age of 3 hours exceeds 5 N / mm ² and the compressive strength at the age of 24 hours is 30 N / mm ² or more. The present invention relates to a low temperature rapid hardening cement composition having a long pot life.

  In recent years, rapid-hardening cement compositions such as quick-hardening mortar and quick-hardening concrete are often used in construction sites such as repair work and emergency work. By the way, a rapid-hardening cement composition that can be used even in a low-temperature environment of 10 ° C. has been proposed (see, for example, Patent Document 1). However, in order to raise the material temperature to 10 ° C. in the winter, it was necessary to heat by burning a large amount of kerosene with a heater such as a jet heater. When a rapid hardening high-fluidity cement composition capable of obtaining good flowability and rapid hardening at a material temperature of 10 ° C. is kneaded at a lower material temperature of 5 ° C. and an environmental temperature, the flowability is not obtained. The rapid hardening was also insufficient.

By the way, a quick-hardening cement composition that can be used even in a low-temperature environment of 5 ° C. has been proposed (see, for example, Patent Document 2). However, the low temperature environment referred to in Patent Document 2 is a curing temperature or an environmental temperature at the time of each test, and is not considered to be a material temperature. In the example of Patent Document 2, there is a description that the flowability, pot life, initial expansion rate, compressive strength, and length change rate of the produced mortar were measured in a 5 ° C environment (paragraph [0045]). There is no description that the material temperature and the mortar were produced in a 5 ° C. environment. 3-19, since the compressive strength at the age of 1 hour has reached 20.1 N / mm ^{2 even} though the pot life is as long as 35 minutes, the material temperature and the mortar can be prepared under the environment of 5 ° C. I can't believe I did it.

By the way, when the pot life is about 30 minutes, the amount of the rapid hardening cement composition that can be placed at one time is limited, or equipment such as a mixer and a pump used for placing must be special. . Therefore, even though the pot life is longer, even when the material temperature and the environmental temperature are 5 ° C., the compressive strength at the age of 3 hours exceeds 5 N / mm ² and the compressive strength at the age of 24 hours is 30 N. A rapid-hardening cement composition for low temperature that is at least / mm ² and a quick-hardening cement admixture for low-temperature use therefor have been desired.

JP 2007-197267 A JP 2007-197268 A

The present invention solves the above problems, that is, the present invention is excellent in that the kneaded cement composition has a pot life of 60 minutes or more even when the material temperature and environmental temperature of the mixed cement composition are 5 ° C. An object of the present invention is to provide a low temperature rapid hardening cement admixture having a compressive strength at 3 hours of age of 5 N / mm ² or more and a compressive strength at 24 hours of age of 30 N / mm ² or more. Moreover, even if the material temperature and the environmental temperature are 5 ° C., the pot life is as excellent as 60 minutes or more, the compressive strength at the age of 3 hours is 5 N / mm ² or more, and the compressive strength at the age of 24 hours. It aims at providing the quick-hardening cement composition for low temperature whose is 30 N / mm < ² > or more.

As a result of diligent studies for solving the above-mentioned problems, the present inventors have included the above-mentioned problems by containing calcium aluminates, gypsum, alkali metal sulfates, alkali metal carbonates and setting retarders having a specific ratio of vitrification. The present invention has been completed. That is, this invention is the rapid hardening cement admixture for low temperature represented by the following (1) or (2), and the rapid hardening cement composition for low temperature represented by (3).
(1) Calcium aluminate, gypsum, alkali metal sulfate, alkali metal carbonate, and a setting retarder, and the vitrification rate of the calcium aluminate is 15 to 55% by mass. Wood.
(2) The rapid hardening cement admixture for low temperature according to (1) above, wherein the calcium aluminate is composed of crystalline calcium aluminate and amorphous calcium aluminate.
(3) A low temperature rapid hardening cement composition containing 10 to 100 parts by mass of the low temperature rapid hardening cement admixture of (1) or (2) above with respect to the cement.

According to the present invention, even when the material temperature and environmental temperature of the mixed cement composition are 5 ° C., the pot life of the kneaded cement composition is excellent as 60 minutes or more, and the compressive strength at the age of 3 hours is 5N. A rapid hardening cement admixture for low temperature having a compressive strength of 24 Nh / mm ² or more and a compressive strength of 30 N / mm ² or more is obtained. Further, according to the present invention, even when the material temperature and the environmental temperature are 5 ° C., the pot life is excellent as 60 minutes or more, the compressive strength at the age of 3 hours is 5 N / mm ² or more, and the age at 24 hours. A rapid hardening cement composition for low temperature having a compressive strength of 30 N / mm ² or more is obtained.

FIG. 1 is a graph of the setting test results. FIG. 2 is a graph of the compressive strength test results.

Calcium aluminates used in the low temperature rapid hardening cement admixture of the present invention are expressed as C ₃ A when CaO is represented as C, Al ₂ O ₃ as A, Na ₂ O as N, and Fe ₂ O ₃ as F. is displayed _{C 2 a, C 12 a 7} , C 5 a 3, CA, C 3 a 5, or calcium aluminate with a mineral composition that appears CA _{2, etc.,} and _C 2 AF and _C 4 AF, etc. Calcium aluminoferrite, calcium haloaluminate containing calcium fluoroaluminate, such as C ₃ A ₃ · CaF ₂ or C ₁₁ A ₇ · CaF _{2 in} which halogen is dissolved or substituted in calcium aluminate, C ₈ NA ₃ and C ₃ N ₂ a _5, etc. and calcium sodium aluminate to be displayed, calcium lithium aluminate, alumina cement, manufactured by Pacific Ocean cement Co. Jet cement "(trade name) and manufactured by Sumitomo Osaka Cement Co., Ltd." jet cement "ultra-fast hard cement (trade name), and the like, as well as _{SiO 2, K 2 O, Fe} 2 O 3, TiO 2 or the like is solid solution or a compound _in these It is a collective term for the above. As the calcium aluminate, any of crystalline, non-crystalline, and mixed amorphous and crystalline materials can be used, and one or more of the calcium aluminates are used. It is possible. In the present invention, crystalline calcium aluminate refers to calcium aluminate having a vitrification rate of 20% by mass or less, and amorphous calcium aluminate refers to calcium aluminate having a vitrification rate of 80% by mass or more. Say. As the crystalline calcium aluminate, those having a vitrification rate of 10% by mass or less are more preferable, and as the amorphous calcium aluminate, those having a vitrification rate of 90% by mass or more are more preferable. Crystalline calcium aluminate is a method in which a CaO raw material, an Al ₂ O ₃ raw material and other raw materials are melted and then gradually cooled to 100 ° C. or lower, a CaO raw material, an Al ₂ O ₃ raw material and other raw materials are turned into a rotary kiln or an electric furnace. It is obtained by a method such as high-temperature firing in a furnace such as Amorphous calcium aluminates can be obtained by melting a CaO raw material, an Al ₂ O ₃ raw material and other raw materials and quenching them with water, air, or the like. Examples of the CaO raw material to be used include limestone, shells, quicklime and slaked lime. Al ₂ O ₃ raw materials used include alumina waste such as waste alumina catalyst discharged from bauxite, petrochemical industry, etc., aluminum slag (aluminum dross), aluminum residual ash generated during the refining process, aluminum cutting waste Waste metal aluminum such as aluminum powder and the like.

Note that the vitrification rate of calcium aluminate is measured by powder X-ray diffraction (internal standard) when the calcium aluminate crystals contained are of one type (for example, C ₃ A only or CA only). The amount (content) of the crystal phase of the calcium aluminate is determined by the method, and the vitrification rate is calculated by regarding the remainder as the glass phase. In addition, when two or more kinds of calcium aluminate crystals are contained (for example, when C ₃ A and CA coexist), after determining the crystal production amount (content) of each crystal by powder X-ray diffraction, This is heated in an electric furnace at 1000 ° C. for 3 hours, and gradually cooled in the furnace over 12 hours until the melting temperature reaches 100 ° C. or lower, so that all phases are substantially crystallized. The amount (content) of each crystal is determined. The difference between the crystal content after the slow cooling and the crystal content before remelting is calculated as the vitrification rate of each crystal. The sum of the vitrification rates of the crystals of the calcium aluminates contained is calculated as the vitrification rate of the calcium aluminates.

The vitrification rate of the calcium aluminates contained in the low-temperature rapid-hardening cement admixture of the present invention is 15 to 55% by mass. When the vitrification rate of the calcium aluminate is lower than 15% by mass, the compressive strength at the age of 3 hours from the addition of the mixed cement composition does not become 5 N / mm ² or more at the material temperature and the environmental temperature of 5 ° C. Insufficient rapid hardness. If the compressive strength does not become 5 N / mm ² or more, the column such as columns, walls, and side surfaces of the beam using the cement composition kneaded material cannot be removed, so that the construction time becomes long. In addition, when the vitrification rate of calcium aluminates exceeds 55% by mass, the compressive strength at 24 hours of age does not become 30 N / mm ² or more due to the addition of cement composition mixed at 5 ° C. material temperature and environmental temperature. , Lack of rapid hardness. Conventionally, it has been considered preferable to increase the vitrification rate of calcium aluminates in order to increase rapid hardening, but it has been found that this is not always correct. The vitrification rate of the calcium aluminates contained in the low-temperature rapid-hardening cement admixture of the present invention is 15 to 55 mass%, preferably 20 to 50 mass%, more preferably 23 to 45 in terms of strength development. Mass%. By setting this preferable range (20 to 50% by mass), the compressive strength at the age of 6 hours from the addition of the mixed cement composition may be 20 N / mm ² or more at the material temperature and the environmental temperature of 5 ° C. In addition, by setting it to a more preferable range (23 to 45% by mass), the compressive strength at a material age of 24 hours can be further set to 35 N / mm ² or more, and the strength development can be made more excellent and more rapid. .

In order to make the vitrification rate of the calcium aluminate contained in the rapid hardening cement admixture for low temperature of the present invention within the above range, it is better to use two or more kinds of calcium aluminate having different vitrification rates. Compared to the case of using only the kind of calcium aluminate, it is preferable because the target vitrification rate is easily obtained. Calcium aluminates used in the present invention are composed of crystalline calcium aluminates and amorphous calcium aluminates, that is, a combination of crystalline calcium aluminates and amorphous calcium aluminates. It is preferable because the vitrification rate is easily within the above range. When using two or more calcium aluminates with different vitrification rates, determine the product of the vitrification rate of each calcium aluminate and the blending ratio of the calcium aluminates in the total calcium aluminate, From these sums, the vitrification rate of calcium aluminates contained in the low temperature rapid hardening cement admixture is calculated. For example, the calcium aluminate contained in the low temperature rapid hardening cement admixture uses two types of calcium aluminates with vitrification rates of R ₁ and R ₂ , and the blending ratios of C ₁ and C ₂ are respectively. Sometimes (the sum of C ₁ and C ₂ at this time is 1), the vitrification rate R ₀ of calcium aluminates contained in the rapid hardening cement admixture for low temperature is obtained by the following formula (1).
R ₀ = R ₁ × C ₁ + R ₂ × C ₂ (1)

Calcium aluminates contained in the low-temperature rapid-hardening cement admixture of the present invention are preferred because the fineness is 3500 cm ² / g or more in terms of Blaine specific surface area because rapid hardening is easily obtained even when the addition amount is small. . A more preferable fineness is 4000 cm ² / g or more in terms of Blaine specific surface area. The calcium aluminate contained in the low temperature rapid hardening cement admixture of the present invention preferably has a loss on ignition as defined in JIS R5202 of 0.2 to 4.0%. When the loss on ignition is less than 0.2%, the time from the start time to the end time of the setting test becomes long, and when it exceeds 4.0%, the rapid hardening cement admixture for low temperature tends to aggregate, and the mixed cement When kneading the composition, if the kneading is not carried out more carefully, for example, by making the mixing time longer than usual, there is a possibility that the low temperature rapid hardening cement admixture is unevenly distributed in the kneaded product. More preferably, the ignition loss is 0.5 to 2.0%.

  In the low-temperature rapid-hardening cement admixture of the present invention, the content of calcium aluminate is preferably in the range of 40 to 70% by mass. If it is less than 40% by mass, the strength may decrease due to excessive expansion, and if it exceeds 70, the elongation of strength in the medium to long term becomes small. Since high intensity | strength including medium and long term is acquired and the elongation of intensity | strength in medium and long term can also be anticipated, the content rate of calcium aluminates is still more preferable 45-60 mass%.

The gypsum contained in the low-temperature rapid-hardening cement admixture of the present invention is not particularly limited as long as it is a powder mainly composed of anhydrous gypsum, dihydrate gypsum, or hemihydrate gypsum, but type II anhydrous gypsum from the viewpoint of strength enhancing action. The main component is preferred. Gypsum reacts with the aluminate phase in cement and calcium aluminates in low-temperature rapid-hardening cement admixtures to produce ettringite (3CaO · Al ₂ O ₃ · 3CaSO ₄ · 32H ₂ O), which is mixed The shrinkage of the hardened body of the cement composition can be suppressed and the initial strength is increased. The fineness of the gypsum used is preferably 3000 cm ² / g or more in terms of the specific surface area according to the Blaine method because reaction activity can be obtained. More preferably, gypsum having a fineness of 4000 cm ² / g or more is preferable. Although the upper limit of the fineness is not particularly limited, it is appropriate to increase the fineness to about 15000 cm ² / g or less because the effect of the increase in cost and labor increases.

  In the low-temperature rapid-hardening cement admixture of the present invention, the content of gypsum is preferably 20 to 145 parts by mass with respect to 100 parts by mass of calcium aluminates. If it is less than 20 parts by mass, the self-contraction is increased and the strength is insufficient. If it exceeds 145 parts by mass, it will be difficult to obtain consistency, and the strength will be insufficient if the amount of water is increased to ensure the required consistency. Since strength is high and consistency is obtained, the gypsum content is more preferably 60 to 120 parts by mass with respect to 100 parts by mass of calcium aluminates.

  Examples of the alkali metal sulfate contained in the low-temperature rapid-hardening cement admixture of the present invention include sodium sulfate, potassium sulfate, lithium sulfate, sodium bisulfate, sodium sulfite, potassium alum, chromium alum, iron alum, and the like. One or more of these can be used. Alkali metal sulfates are preferred because they do not contain water of crystallization, that is, anhydrous products can be added in a small amount.

  In the low-temperature rapid-hardening cement admixture of the present invention, the content of alkali metal sulfate is preferably 2 to 10 parts by mass with respect to 100 parts by mass of calcium aluminates. If it is less than 2 parts by mass, the initial strength may be insufficient. If it exceeds 10 parts by mass, it will be difficult to obtain a consistency, and the strength will be insufficient if the amount of water is increased in order to ensure the required consistency. Since the initial strength is high and consistency is obtained, the content of the alkali metal sulfate is more preferably 3 to 7 parts by mass with respect to 100 parts by mass of the calcium aluminates.

  The alkali metal carbonate contained in the low-temperature rapid-hardening cement admixture of the present invention plays an important role in ensuring the consistency of the kneaded material and ensuring the pot life. In the present invention, examples of the alkali metal carbonate include sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, and lithium bicarbonate. One or more of these can be used. It is preferable to use a lithium salt as the alkali metal sulfate because the effect is high with a smaller amount.

  In the low-temperature rapid-hardening cement admixture of the present invention, the content of alkali metal carbonate is preferably 1 to 10 parts by mass with respect to 100 parts by mass of calcium aluminates. If the amount is less than 1 part by mass, a higher amount of the low-temperature rapid-hardening cement admixture is required to ensure consistency and pot life. If it exceeds 10 parts by mass, it will be difficult to obtain a consistency, and the strength will be insufficient if the amount of water is increased in order to ensure the required consistency. Since it is easy to ensure consistency and pot life, it is more preferable that the content of the alkali metal carbonate is 2 to 7 parts by mass with respect to 100 parts by mass of the calcium aluminate.

The setting retarder contained in the low-temperature rapid-hardening cement admixture of the present invention plays an important role in ensuring the consistency of the kneaded material and ensuring the pot life by delaying the hydration reaction of the cement. Any setting retarder used in the present invention can be used as long as it delays the hydration reaction of 3CaO.SiO ₂ (C ₃ S). It is preferable to use one or more selected from carboxylic acids or oxycarboxylates. Examples of these oxycarboxylic acids and oxycarboxylates include citric acid, citrate, gluconic acid, gluconate, tartaric acid, tartrate, heptonic acid, heptonic acid salt and the like.

  In the low-temperature rapid-hardening cement admixture of the present invention, the content of the setting retarder is preferably 0.2 to 10 parts by mass with respect to 100 parts by mass of the calcium aluminates. If the amount is less than 0.2 parts by mass, a higher amount of the low-temperature rapid-hardening cement admixture is required in order to ensure consistency and pot life. If it exceeds 10 parts by mass, the strength may be insufficient. Since it is easy to ensure consistency and strength, the content of the setting retarder is more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the calcium aluminates.

  In addition to the calcium aluminate, gypsum, alkali metal sulfate, alkali metal carbonate, and setting retarder, one or more of the other admixtures are included in the low temperature rapid hardening cement admixture of the present invention. It can use together in the range which does not impair the effect of invention substantially. Such admixtures include, for example, water reducing agents, AE water reducing agents, high performance water reducing agents, high performance AE water reducing agents, cement dispersing agents such as fluidizing agents, thickeners, expansion materials, shrinkage reducing agents, cement polymers. , Waterproof materials, rust preventives, antifreezing agents, water retention agents, pigments, fibers, water repellents, whitening prevention agents, quick setting agents (materials), other quick hardening admixtures (agents), foaming agents, extinguishing agents Examples thereof include foams, pozzolanic fine powders such as silica fume, blast furnace slag fine powders, stone powders such as limestone fine powders, water repellents, and surface hardeners.

    The low-temperature rapid-hardening cement admixture of the present invention is a method in which a predetermined amount of each of the above materials is mixed in advance using a V-type mixer, a gravitational mixer such as a tiltable concrete mixer, a Henschel mixer, or a ribbon mixer. However, it is preferable because uneven distribution of the material is suppressed in the cement composition after the addition. The mixer used at this time may be a continuous mixer or a batch mixer. The order in which each material is charged into the mixer is not particularly limited. One by one may be added, or part or all may be added simultaneously. Moreover, the rapid hardening cement admixture for low temperature of this invention can also be manufactured by the method of measuring and throwing each material into containers, such as a bag and a container made from polyethylene.

  The low-temperature rapid-hardening cement admixture of the present invention may be put into a mixer during the kneading of the cement composition in a concrete manufacturing plant or the like, or the concrete, mortar, or cement paste that is the kneaded mixture of the cement composition may be used. It may be added to the cement grout by being put into a stirrer such as a truck agitator at the construction site or a field-installed agitator, or a mixer installed at the site. The above-mentioned low-temperature rapid-hardening cement admixture may be added in two or more portions at the time of producing the cement grout composition, at the time of kneading the cement composition and / or at the time of placing the kneaded material.

  The rapid hardening cement composition for low temperature of this invention contains said rapid hardening cement admixture for low temperature and cement.

  As the cement used in the present invention, various portland cements such as normal strength, super early strength, low heat and moderate heat, ecocement, and portland cement or ecocement include fly ash, blast furnace slag, silica fume or limestone fines. Examples include various mixed cements in which powders and the like are mixed, and these can be used alone or in combination of two or more. The cement here refers to cements mainly composed of rapid hardening components such as calcium aluminates, such as alumina cement, “Jet Cement” (trade name) manufactured by Taiheiyo Cement Co., Ltd., and “Jet Cement” (trade name) manufactured by Sumitomo Osaka Cement Co., Ltd. ) And the like are not included, and these are included in the calcium aluminates. Since the amount of the low-temperature rapid-hardening cement admixture for obtaining the initial strength of the kneaded material can be relatively small, ordinary Portland cement, early-strength Portland cement, eco-cement, or two of them can be used as the cement used in the present invention. What mixed the above is preferable.

  The amount of the low-temperature rapid-hardening cement admixture contained in the low-temperature rapid-hardening cement composition of the present invention is preferably 10 to 100 parts by weight with respect to 100 parts by weight of cement. If it is less than 10 parts by mass, it is difficult to obtain the initial strength, and in order to obtain a predetermined initial strength if it is less than 10 parts by mass, the water-cement ratio must be lowered, so that the consistency of the kneaded product is lowered. In addition, when it exceeds 100 parts by mass, it is difficult to obtain the pot life, and in order to obtain a predetermined pot life exceeding 100 parts by mass, the water-cement ratio must be increased, so the long-term strength of the kneaded product is reduced. To do. From the balance of the initial strength of the kneaded product and the pot life, the amount of the above-mentioned low-temperature rapid-hardening cement admixture contained in the low-temperature rapid-hardening cement composition of the present invention is 20 to 80 parts by weight with respect to 100 parts by weight of cement. More preferably, the content is 40 to 70 parts by mass.

  The rapid hardening cement composition for low temperature of the present invention includes, in addition to cement and the above described rapid hardening cement admixture for low temperature, other admixtures and one or more kinds of aggregates within a range not impairing the effects of the present invention. Can be used together. Examples of such admixture materials include cement polymers, foaming agents, foaming agents, waterproofing materials, rust preventives, shrinkage reducing agents, water retention agents, pigments, fibers, water repellents, whitening prevention agents, and expansion materials ( Agents), quick setting agents (materials), quick-hardening admixtures (agents) other than those mentioned above, antifoaming agents, gypsum, blast furnace slag fine powder, fly ash, stone powder, silica fume, surface hardeners and the like. Examples of aggregates include river sand, sea sand, mountain sand, crushed sand, artificial fine aggregate, slag fine aggregate, recycled fine aggregate, quartz sand, river gravel, land gravel, crushed stone, artificial coarse aggregate, slag coarse Aggregates, recycled coarse aggregates and the like can be mentioned.

  The method for producing the rapid hardening cement composition for low temperature according to the present invention is not particularly limited. For example, a gravity mixer such as a V-type mixer or a tiltable concrete mixer, a Henschel mixer, a mixer such as a ribbon mixer, It can manufacture by mixing the predetermined amount of each material of the rapid-hardening cement composition for low temperature of this invention. The mixer used at this time may be a continuous mixer or a batch mixer. Moreover, the order in which each material is charged into the mixer is not particularly limited, and one material may be added at a time, or some or all may be added simultaneously. Moreover, the rapid hardening cement composition for low temperature of this invention can also be manufactured by the method of measuring and throwing each material into containers, such as a bag and a container made from polyethylene.

The rapid hardening cement composition for low temperature of the present invention is used by kneading with water. The amount of water at this time is not particularly limited, but is preferably 25 to 45 parts by mass, more preferably 30 to 40 parts by mass with respect to 100 parts by mass in total of the cement and the rapid hardening cement admixture for low temperature.
The method of kneading with water is not particularly limited, for example, a method of adding the entire amount of the rapid hardening cement composition for low temperature of the present invention to water and kneading, and further kneading the water while mixing the rapid hardening cement composition for low temperature of the present invention. A method of kneading by adding all the water to the low temperature rapid hardening cement composition of the present invention, a method of adding and kneading water to the low temperature rapid hardening cement composition of the present invention while further kneading, water and the low temperature of the present invention For example, there is a method in which a part of each of the quick-hardening cement compositions is kneaded into two or more parts, and the kneaded ones are further kneaded. Moreover, although the apparatus and kneading apparatus used for kneading are not particularly limited, it is preferable to use a mixer because a large amount can be kneaded. The mixer that can be used may be a continuous mixer or a batch mixer, such as a pan concrete mixer, a pug mill concrete mixer, a gravity concrete mixer, a grout mixer, a hand mixer, and a plaster mixer.

[Example 1]
Amorphous calcium aluminates (calcium aluminates A) and crystalline calcium aluminates (calcium aluminates B) shown below are mixed at the blending ratio shown in Table 1 to obtain six types of calcium aluminates. (CA1 to CA6) were produced. The measurement results of ignition loss as defined in JIS R5202 for each calcium aluminate are shown in Table 1. Each calcium aluminate produced was 48.5% by mass, gypsum 45.0% by mass, alkali metal sulfate 3.2% by mass, alkali metal carbonate 3.2% by mass and setting retarder 0.1% by mass. Six types (AD1 to AD6) of rapid hardening cement admixtures for low temperature were produced. The low temperature rapid hardening cement admixture using CA1 is AD1, and the low temperature rapid hardening cement admixture using CA2 to CA6 is AD2 to AD6, respectively. The materials used, including cement, aggregate and water reducing agent, are shown below.
<Materials used>
・ Calcium aluminate A
Vitrification rate: 95% by mass,
Blaine specific surface area 5250 cm ² ,
C / A molar ratio: 1.39 (CaO is C, Al ₂ O ₃ is A)
Crystals identified by powder X-ray diffraction; CA

・ Calcium aluminate B
Vitrification rate: 5%,
Blaine specific surface area: 4000 cm ²
C / A molar ratio: 1.25 (CaO is C, Al ₂ O ₃ is A, and SiO ₂ is S)
Crystals identified by powder X-ray diffraction; CA, C ₁₂ A ₇ and C ₂ AS

・ Gypsum Type II anhydrous gypsum with a specific surface area of 7500 cm ²

・ Alkali metal sulfate sodium sulfate (reagent, manufactured by Kanto Chemical Co., Inc.)

・ Alkali metal carbonate Lithium carbonate (reagent, manufactured by Kanto Chemical Co., Inc.)

-Setting retarder sodium citrate (reagent, manufactured by Kanto Chemical Co., Inc.)

・ Cement Normal Portland cement (manufactured by Taiheiyo Cement)

-Aggregate JIS R 5201 standard sand for cement strength test

・ Water reducing agent Polycanlubonate-based high-performance water reducing agent (trade name “NF-200”, manufactured by Taiheiyo Materials Co., Ltd.)

  230 parts by mass of cement and 0.264 parts by mass of water reducing agent for 100 parts by mass of each of the low temperature rapid hardening cement admixtures, that is, 43.5 parts by mass of the low temperature rapid hardening cement admixture for 100 parts by mass of cement and Six types of rapid-hardening cement were prepared by mixing 0.115 parts by mass of a water reducing agent. Six hundred mortars were prepared by adding 900 g of the prepared quick-hardening cement, 1350 g of aggregate, and 330 g of tap water to a 5 liter Hobart mixer (manufactured by Hobart) and kneading for 3 minutes. Each material temperature before kneading was adjusted to 5 ° C., and kneading was performed in a temperature-controlled room at 5 ° C. and humidity of 80% or more.

As a quality test of the produced mortar, as shown below, the setting time and the compressive strength at the age of 3 hours, 6 hours, and 24 hours were measured. These results are shown in Table 2, FIG. 1 and FIG. The evaluation of workability is as follows. In addition, the curing and setting tests of the specimens in the compressive strength test were all performed in a constant temperature room at 5 ° C. and a humidity of 80% or more.
<Quality test method>
-Compressive strength test Compressive strength of each material age was measured according to JSCE-G 505-1999 "Method for testing compressive strength of mortar or cement paste using cylindrical specimen". At this time, the specimen was cured in a thermostatic chamber at 5 ° C. with the form until just before the test, removed from the mold just before the test, the maximum load was measured, and the compressive strength was obtained. For the preparation of the specimen, a mold having an inner diameter of 50 mm and a height of 100 mm was used.
-Setting test JIS R 5201: 1997 "Physical test method of cement" The start time and end time were measured according to the setting time, and the start time was used as an index of pot life.

The mortars according to the examples of the present invention have excellent pot life (starting time) of 60 minutes or more even when the material temperature and the environmental temperature are 5 ° C., and the compressive strength at a material age of 3 hours is 5 N / mm ^2. From the above, it can be seen that the compressive strength at a material age of 24 hours is 35 N / mm ² or more, and the initial strength development is also excellent.

According to the present invention, even at a material temperature of 5 ° C. and an environmental temperature, the pot life is excellent as 60 minutes or more, the compressive strength at a material age of 3 hours is 5 N / mm ² or more, and the compressive strength at a material age of 24 hours. There since low-temperature rapid hardening cement composition is 30 N / mm ² or more can be obtained, can be used for repair work or emergency highly construction work in a low temperature environment.

Claims (3)

A low-temperature rapid-hardening cement admixture containing calcium aluminate, gypsum, alkali metal sulfate, alkali metal carbonate and a setting retarder, wherein the calcium aluminate has a vitrification ratio of 15 to 55 mass%. The rapid hardening cement admixture for low temperature according to claim 1, wherein the calcium aluminate comprises crystalline calcium aluminate and amorphous calcium aluminate. A rapid hardening cement composition for low temperature containing cement and 10 to 100 parts by mass of the rapid hardening cement admixture according to claim 1 or 2 with respect to the cement.

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