Expansion composition and cement composition

Abstract

To provide an expansive composition and a cement composition that suppress crack due to drying shrinkage and hydration heat generation from early stage of material age and has excellent neutralization resistance.SOLUTION: Provided is an expansive composition which contains a cement admixture and an expansive admixture, in which the cement mixture containing one kind of, or two or more kinds of non-hydraulic compound selected from a group consisting of γ-2CaO-SiO2, 3CaO-2SiO2, α-CaO-SiO2, and calcium magnesium silicate.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention mainly relates to an expansive composition and a cement composition used in the civil engineering and construction industries.

Background Art

[0002] Recently, high-durability concrete with few cracks has been emphasized. It is known that concrete cracks are mainly caused by two factors. One is caused by drying shrinkage, and it has been proposed to use an expansive material in a concrete structure for the purpose of compensating for the drying shrinkage. The expansive material causes a hydration reaction together with water injection and contributes to reducing the cracks due to drying shrinkage from the early age of the material. As the expansive material, those containing a CaO-Al2O3-SO3-based compound as an active ingredient are known (see, for example, Patent Documents 1 to 3).

[0003] The second cause of cracking is cracking due to heat of hydration. Cracking due to heat of hydration occurs because the concrete expands unevenly due to the temperature difference between the inside and near the surface of the concrete, and the tensile stress generated near the surface exceeds the tensile strength of the concrete. Therefore, it is necessary to reduce the heat of hydration. In addition, an expansive material with a large amount of free lime has a large heat generation amount and promotes cracking due to heat of hydration.

[0004] Although a heat-of-hydration suppressing type expansive material added with a delaying component such as dextrin is used, there is no cement admixture that imparts an effect of enhancing the carbonation resistance (see, for example, Patent Documents 4 and 5).

[0005] On the other hand, although studies have been made on using a non-hydraulic compound such as γ-C2S (γ-2CaO·SiO2), which has little heat of hydration and excellent dimensional stability after carbonation reaction, as a cement admixture, since the carbonation reaction of the non-hydraulic compound takes time, it does not contribute to suppressing cracks at the early age of the material (see, for example, Patent Documents 6 and 7).

[0006] In addition, when γ-2CaO·SiO2 is produced on an industrial scale without using high-purity reagents, the formation of a small amount of highly reactive minerals such as β-2CaO·SiO2 is involved, making it difficult to sufficiently suppress the heat of hydration.

[0007] That is, there has been no cement admixture that can suppress cracks caused by drying shrinkage and heat of hydration from the early age of the material and has excellent carbonation resistance.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, an object of the present invention is to provide an expansion composition and a cement composition that can suppress cracks caused by drying shrinkage and heat of hydration from the early age of the material and have excellent carbonation resistance.

Means for Solving the Problems

[0010] As a result of intensive research to solve the above problems, the inventors of the present invention have found that the above problems can be solved by using an expansion composition containing γ-2CaO·SiO2 and an expansive agent, and have completed the present invention. That is, the present invention is as follows. [1] An expansion composition containing a cement admixture containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate, and an expansive agent. [2] The expansion composition according to [1], wherein Li is contained in the non-hydraulic compound, and the content rate of Li in the non-hydraulic compound is 0.001 to 1.0% by mass in terms of oxide conversion. [3] The expansion composition according to [1] or [2], characterized in that the chemical components of the cement admixture contain 0.005 to 1 part by mass of Li2O, 45 to 70 parts by mass of CaO, 29 to 55 parts by mass of SiO2, and 0 to 10 parts by mass of Al2O3 in 100 parts by mass. [4] The expansion composition according to any one of [1] to [3], wherein the expansive agent contains free lime, anhydrous gypsum, and a hydraulic compound. [5] The expansion composition according to any one of [1] to [4], wherein the content rate of the free lime in the expansive agent is 10 to 39% by mass. [6] A cement composition containing the expansion composition according to any one of [1] to [5] and cement.

Advantages of the Invention

[0011] It is possible to provide an expansion composition and a cement composition that suppress cracks due to drying shrinkage and heat of hydration from the initial age of the material and have excellent carbonation resistance.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail. In addition, parts and % in this specification are based on mass unless otherwise specified.

[0013] The expansive composition of the present invention contains a cement admixture containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate, and an expansive agent.

[0014] The cement admixture contains one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate. By adding the cement admixture to the expansive composition, a neutralization suppression effect can be obtained.

[0015] The cement admixture preferably has a Li content in the non-hydraulic compound of 0.001 to 1.0% by mass in terms of oxide, more preferably 0.005 to 1.0% by mass, still more preferably 0.010 to 0.90% by mass, and even more preferably 0.015 to 0.80% by mass. When the Li content in the non-hydraulic compound is within the above range in terms of oxide, it is presumed that the formation of vaterite, which is a type of calcium carbonate, among the carbonations of C-S-H (calcium silicate hydrate) is promoted, and it is considered that further improvement in strength enhancement is likely to occur. Here, "containing Li in the non-hydraulic compound" means that Li2O is included as a chemical composition in the non-hydraulic compound (its presence can be confirmed by ICP emission spectroscopic analysis), but Li2O is not identified by X-ray diffraction measurement (no distinct peak of Li2O is seen), and it does not simply refer to a state where the non-hydraulic compound and the Li compound are physically mixed. Such a state can be obtained by mixing the respective raw materials and performing heat treatment at a high temperature of 1,000°C or higher. Hereinafter, each component, etc. will be described. Note that the Li content in terms of oxide can be measured by the method described in the examples.

[0016] The non-hydraulic compound may be one kind or two or more kinds. When there are two or more non-hydraulic compounds, the Li content in the non-hydraulic compounds refers to the content in terms of oxide conversion of Li with respect to the total of two or more non-hydraulic compounds.

[0017] (γ-2CaO·SiO2) γ-2CaO·SiO2 is one of the compounds represented by 2CaO·SiO2 and is known as a low-temperature phase, which is completely different from the high-temperature phases α-2CaO·SiO2, α’-2CaO·SiO2, and β-2CaO·SiO2. Although all of these are represented by 2CaO·SiO2, their crystal structures and densities are different. Usually, the 2CaO·SiO2 present in cement clinker is β-2CaO·SiO2. β-2CaO·SiO2 has hydraulicity, but does not exhibit the neutralization suppression effect like γ-2CaO·SiO2 of the present invention.

[0018] The Blaine specific surface area of γ-2CaO·SiO2 is preferably 3,000 to 8,000 cm 2 / g, and more preferably 4,000 to 6,000 cm 2 / g. When the Blaine specific surface area is within the above range, the neutralization suppression effect can be sufficiently obtained.

[0019] Impurities may be contained when γ-2CaO·SiO2 is industrially produced. The presence of impurities does not pose a particular problem as long as it does not substantially inhibit the object of the present invention. Specific examples of impurities include Al2O3, MgO, TiO2, MnO, Na2O, S, Cr2O3, P2O5, and Fe2O3.

[0020] In addition, as coexisting compounds, there may be dicalcium silicates other than γ-2CaO·SiO2, calcium silicates other than 2CaO·SiO2 such as tricalcium silicate 3CaO·SiO2, rankinite 3CaO·2SiO2, wollastonite CaO·SiO2, melilite 3CaO·MgO·2SiO2, akermanite 2CaO·MgO·2SiO2, calcium magnesium silicates such as monticellite CaO·MgO·SiO2, calcium aluminosilicates such as gehlenite 2CaO·Al2O3·SiO2, anorthite CaO·Al2O3·2SiO2, and merlite which is a mixed crystal of akermanite 2CaO·MgO·2SiO2 and gehlenite 2CaO·Al2O3·SiO2, magnesium silicates such as MgO·SiO2 and 2MgO·SiO2, free lime, free magnesia, calcium ferrite 2CaO·Fe2O3, calcium aluminoferrite 4CaO·Al2O3·Fe2O3, leucite (K2O, Na2O)·Al2O3·SiO2, spinel MgO·Al2O3, magnetite Fe3O4, etc.

[0021] The blending ratio of γ-2CaO·SiO2 varies depending on the use and is not particularly limited, but it is preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass, and even more preferably 40 to 60 parts by mass per 100 parts by mass of the cement admixture. When the blending ratio of γ-2CaO·SiO2 is within the above range, sufficient dimensional stability can be obtained, and the neutralization suppression effect can be sufficiently obtained.

[0022] (3CaO·2SiO2) 3CaO·2SiO2 is a mineral containing CaO in pseudo-wollastonite and is called rankinite. It is a mineral that is chemically stable without hydration activity but has a large effect of promoting carbonation (salt).

[0023] (α-CaO·SiO2) α-CaO·SiO2 (α-wollastonite) is a compound represented by CaO·SiO2 and is known as a high-temperature phase, which is completely different from the low-temperature phase β-CaO·SiO2. Although both of them are represented by CaO·SiO2, their crystal structures and densities are different.

[0024] Naturally occurring wollastonite is the low-temperature phase β-CaO·SiO2. β-CaO·SiO2 has acicular crystals and is used as an inorganic fibrous material such as wollastonite fibers, but it does not have the carbonation promotion effect like α-CaO·SiO2 according to this embodiment.

[0025] (Calcium magnesium silicate) Calcium magnesium silicate is a general term for CaO-MgO-SiO2 based compounds. In this embodiment, it is preferably Merwinite represented by 3CaO·MgO·2SiO2 (C3MS2). According to Merwinite, a large carbonation promotion effect can be achieved.

[0026] Among the above non-hydraulic compounds, especially γ-2CaO·SiO2 is preferred because it is accompanied by a pulverization phenomenon called dusting during production, so it requires less energy for pulverization compared to other compounds, has a large carbonation promotion effect over a long period of time, and on the other hand, has a very large neutralization suppression effect when combined with blast furnace cement at a low water binder ratio.

[0027] The non-hydraulic compound according to this embodiment is obtained by blending a CaO raw material, an SiO2 raw material, an MgO raw material, and an Li raw material in a predetermined molar ratio and performing heat treatment. Examples of the CaO raw material include calcium carbonate such as limestone, calcium hydroxide such as slaked lime, by-product slaked lime such as acetylene by-product slaked lime, and fine powder generated from waste concrete blocks. Examples of the SiO2 raw material include quartz, clay, and various siliceous dusts generated as industrial by-products typified by silica fume and fly ash. Examples of the MgO raw material include magnesium hydroxide, basic calcium carbonate, and dolomite. Examples of the Li raw material include lithium carbonate. When Li is contained in the CaO raw material, the SiO2 raw material, or the MgO raw material, it is not necessary to newly add an Li raw material. From the viewpoint of reducing the non-energy-derived CO2 emissions during heat treatment, one or more selected from industrial by-products containing CaO, such as by-product slaked lime, fine powder generated from waste concrete blocks, municipal waste incineration ash, and sewage sludge incineration ash, can be used. Among them, it is more preferable to use by-product slaked lime, which has a smaller amount of impurities compared to other industrial by-products.

[0028] As the by - produced slaked lime, there are by - produced slaked lime (depending on the acetylene gas production method, there are wet products and dry products) by - produced in the production process of acetylene gas by the calcium carbide method, and by - produced slaked lime contained in the dust captured in the wet dust collection process of the calcium carbide electric furnace, such as acetylene by - produced slaked lime. The by - produced slaked lime contains, for example, 65 - 95% (preferably 70 - 90%) calcium hydroxide, and in addition, 1 - 10% calcium carbonate and 0.1 - 6.0% (preferably 0.1 - 3.0%) iron oxide. These ratios can be confirmed by the mass loss obtained by fluorescent X - ray measurement and differential thermal gravimetric analysis (TG - DTA) (Ca(OH)2: around 405°C - 515°C, CaCO3: around 650°C - 765°C). The volume - average particle diameter measured by the laser diffraction / scattering method is about 50 - 100 μm. Further, in JIS K 0068 "Method for Measuring Moisture in Chemical Products", the moisture content measured by the drying loss method is preferably 10% or less. Also, it may contain sulfur compounds such as CaS, A12S3, and CaC2·CaS, but preferably 2% or less.

[0029] The heat treatment at a high temperature of 1,000°C or higher described above is not particularly limited, but can be carried out, for example, by a rotary kiln or an electric furnace. The heat treatment temperature is not uniquely determined, but is usually carried out in the range of about 1,000 - 1,800°C, and often in the range of about 1,200 - 1,600°C.

[0030] This embodiment can also use industrial by - products containing the non - hydraulic compound described above. In this case, impurities coexist. Examples of such industrial by - products include steelmaking slag.

[0031] The CaO raw material, SiO2 raw material, and MgO raw material may contain impurities, but there is no particular problem as long as the effects of the present invention are not inhibited. Specific examples of the impurities include, for example, Al2O3, Fe2O3, TiO2, MnO, Na2O, K2O, S, P2O5, F, B2O3, chlorine, and the like. In addition, coexisting compounds include free calcium oxide, calcium hydroxide, calcium aluminate, calcium aluminosilicate, calcium ferrite, calcium aluminoferrite, calcium phosphate, calcium borate, magnesium silicate, leucite (K2O, Na2O)·Al2O3·SiO2, spinel MgO·Al2O3, magnetite Fe3O4, the aforementioned CaS, A12S3, and sulfur compounds such as CaC2·CaS.

[0032] Among these impurities, the content of S (sulfur) in the non-hydraulic compound is preferably 1.0% or less, more preferably 0.7% or less, and still more preferably 0.5% or less in terms of oxide (SO3) conversion. When it is 1.0% or less, a sufficient carbonation promotion effect can be obtained, and the setting and hardening properties can be made within an appropriate range. The content of S in terms of oxide (SO3) conversion can be measured by fluorescence X-ray measurement. In addition, S (sulfur) in the non-hydraulic compound may be present if it is about 2% in terms of oxide conversion.

[0033] The content of the non-hydraulic compound in the cement admixture (the content in the total amount when multiple types are included) is preferably 65% or more, more preferably 70% or more, and still more preferably 75% or more. In addition, it is possible that hydraulic 2CaO·SiO2 other than γ-2CaO·SiO2 is mixed, and the maximum mixing amount can be up to 35%.

[0034] The content of γ-2CaO·SiO2 in the cement admixture is preferably 35% or more, more preferably 45% or more. In addition, the upper limit value of the content of γ-2CaO·SiO2 is not particularly limited. Among steelmaking slags, an electric furnace reduction period slag or a stainless steel slag with a high γ-2CaO·SiO2 content is preferable.

[0035] Also, from the viewpoint of more easily expressing its effects in the cement admixture, in terms of chemical components, it is preferable to contain 0.001 to 1.0 part by mass of Li2O, 45 to 70 parts by mass of CaO, 29 to 55 parts by mass of SiO2, and 0 to 10 parts by mass of Al2O3 in 100 parts by mass of the cement admixture. The content of Li2O can be measured by the method described in the examples below. Also, CaO, SiO2, and Al2O3 can be measured by fluorescent X-ray. In terms of chemical components, it is more preferable to contain 0.002 to 0.5 part by mass of Li2O, 60 to 70 parts by mass of CaO, 29 to 45 parts by mass of SiO2, and 0.5 to 5 parts by mass of Al2O3 in 100 parts by mass of the cement admixture. Furthermore, in terms of chemical components, it is preferable that the total of Li2O, CaO, SiO2, and Al2O3 in 100 parts by mass of the cement admixture is 90 parts by mass or more, and more preferably 95 to 100 parts by mass.

[0036] Examples of the method for quantifying non-hydraulic compounds in the cement admixture include the Rietveld method by powder X-ray diffraction.

[0037] The Blaine specific surface area of the cement admixture is not particularly limited, but it is preferably 1,500 cm 2 / g or more, and the upper limit is preferably 8,000 cm 2 / g or less. Among them, 2,000 to 6,000 cm 2 / g is more preferable, and 4,000 to 6,000 cm 2 / g is even more preferable. When the Blaine specific surface area is equal to or greater than the above lower limit value, good material separation resistance can be obtained, and the carbonation promotion effect becomes sufficient. Also, when the Blaine specific surface area is equal to or less than the above upper limit value, the grinding power during grinding does not increase, which is economical, and weathering is suppressed, and deterioration of quality over time can be suppressed.

[0038] The amount of the cement admixture used in the present invention varies depending on the application and is not particularly limited. The amount of the cement admixture in the expansive composition is preferably 5 to 50 parts by mass, more preferably 7 to 40 parts by mass, and even more preferably 10 to 30 parts by mass per 100 parts by mass of the expansive composition. When the amount of the cement admixture is within the above range, the effect of suppressing neutralization and dimensional stability can be sufficiently imparted, and the strength can be improved.

[0039] The expansive material used in the present invention is not particularly limited as long as it is a substance capable of imparting expansibility. Examples of the expansive material include gas foaming substance systems and cement mineral systems. Examples of the gas foaming substance system include aluminum powder, iron powder, peroxide substances, carbon substances, and the like. Examples of the cement mineral system include ettringite systems, lime systems, and lime-ettringite composite systems. In the present invention, from the viewpoint of being able to impart effective expansibility, it is preferable to use a cement mineral system.

[0040] The cement mineral-based expansive material will be described in more detail. Examples of the cement mineral-based expansive material include those containing free lime and free magnesia, but from the viewpoint of long-term stability, those containing free lime are preferable. Examples of those containing free lime include free lime-anhydrous gypsum systems, free lime-hydraulic compound systems, and free lime-hydraulic compound-anhydrous gypsum systems. The content rate of free lime in the expansive material is preferably 10 to 39% by mass, more preferably 12 to 37% by mass, and even more preferably 15 to 35% by mass. As the expansive material used in the present invention, those containing free lime, anhydrous gypsum, and hydraulic compounds are preferably used because of their good expansion performance. Here, examples of the hydraulic compound include one or more of awin, calcium ferrite, calcium aluminoferrite, calcium silicate, calcium aluminate, and the like. As such an expansive material, commercially available expansive materials and static crushing materials can be used.

[0041] Expansion materials are commercially available from various companies. Representative examples include "Denka CSA" and "Denka Power CSA" manufactured by Denka Co., Ltd., "Asano Jipkal" manufactured by Asano Co., Ltd., "Sacks" manufactured by Sumitomo Osaka Cement Co., Ltd., "Expan", "N-EX", and "Bristar" manufactured by Pacific Materials Co., Ltd., etc.

[0042] The usage amount of the expansion material of the present invention varies depending on the application and is not particularly limited. The usage amount of the expansion material in the expansion composition is preferably 50 to 95 parts by mass, more preferably 60 to 93 parts by mass, and even more preferably 70 to 90 parts by mass in 100 parts by mass of the expansion composition. When the blending ratio of the expansion material is within the above range, sufficient dimensional stability can be obtained, and the effect of suppressing carbonation can be sufficiently obtained.

[0043] The cement composition of the present invention contains the above expansion composition and cement.

[0044] Examples of the cement used in the present invention include various Portland cements such as ordinary, early strength, ultra-early strength, low heat, and medium heat Portland cements, various blended cements obtained by mixing blast furnace slag, fly ash, or silica with these Portland cements, and filler cements mixed with limestone powder, etc. One or more of these can be used.

[0045] From the viewpoints of manufacturing cost and strength development property, the Blaine specific surface area value of the cement used in the present invention is preferably 2,500 cm 2 / g or more and 7,000 cm 2 / g or less, more preferably 2,750 cm 2 / g or more and 6,000 cm 2 / g or less, and even more preferably 3,000 cm 2 / g or more and 4,500 cm 2 / g or less. The Blaine specific surface area value is determined in accordance with JIS R 5201 (Physical test methods for cement).

[0046] The blending ratio of the expansion composition in the cement composition of the present invention is preferably 5 to 50 parts by mass, more preferably 7 to 40 parts by mass, and even more preferably 10 to 30 parts by mass per 100 parts by mass of the cement composition.

[0047] The cement composition of the present invention may mix each material during construction, or may mix part or all of them in advance without any problem.

[0048] The cement composition of the present invention may contain one or more of gas foaming substances, water reducing agents, AE agents, rust preventives, water repellents, antibacterial agents, colorants, antifreezing agents, fine limestone powder, fine powder of slowly cooled blast furnace slag, incineration ash of sewage sludge and its molten slag, incineration ash of municipal waste and its molten slag, and incineration ash of pulp sludge, etc., in a range that does not adversely affect the performance, defoaming agents, thickeners, shrinkage reducing agents, fiber substances such as steel fibers, vinylon fibers, carbon fibers, and wollastonite fibers, polymers, clay minerals such as bentonite and sepiolite, and anion exchangers such as hydrotalcite.

[0049] In the cement composition of the present invention, the mixing method of each material is not particularly limited, and each material may be mixed during construction, or part or all of them may be mixed in advance without any problem. As the mixing device, any existing device, for example, a tilting drum mixer, an omnimixer, a Henschel mixer, a V-type mixer, and a Nauta mixer can be used.

Examples

[0050] Hereinafter, the present invention will be further described based on experimental examples.

[0051] [Experimental Example 1] Mortar with a water / cement ratio of 50% and a ratio of cement to sand of 1 to 3 was prepared. An expansion composition material was trial-produced and used while replacing sand at the ratios shown in Table 1 with respect to 100 parts by mass of cement, and the compressive strength, length change rate, maximum temperature at the center of the mortar, and carbonation depth of the prepared mortar were measured.

[0052] <Materials Used> · Cement: Commercially available ordinary Portland cement, Blaine specific surface area 3200 cm 2 / g, specific gravity 3.15 g / cm 3 · Li+γ-C2S a: Prototype. γ-2CaO·SiO2 containing Li. Reagent grade calcium carbonate and reagent grade silicon dioxide were mixed at a molar ratio of 2:1, and further reagent grade lithium carbonate was mixed so that the Li content in the mixture was 0.1 part by mass (internal substitution) in terms of oxide (Li2O). Heat treatment was carried out at 1400 °C for 2 hours and left to room temperature, then pulverized to a Blaine specific surface area of 4000 cm 2 / g. Li2O content 0.1%. · Expansive agent I: "Denka CSA#20" manufactured by Denka Co., Ltd., free lime - hydraulic compound - anhydrous gypsum type, Blaine specific surface area 3000 cm 2 / g. Free lime content 30%. · Expansion composition A: Prepared by mixing 50 parts by mass of Li+γ-C2S a and 50 parts by mass of expansive agent I. · Sand: "Standard sand for cement strength test" manufactured by the Cement Association · Water: Tap water

[0053] <Measurement Method> · Blaine specific surface area: Measured according to JIS R 5201. · Compressive strength: A 4×4×16 cm specimen was prepared, and the strength at 28 days of age was measured according to JISR 5201. · Length change rate: Measured at 28 days of age according to JIS A 6202. Demolded at 1 day of age and cured in water until 7 days of age. · Maximum temperature at the center of the mortar: About 3.5 liters of mortar was put into a cylindrical container made of foamed polystyrene with a depth of 30 cm, an inner diameter of 13 cm, and a thickness of 10 cm, and the maximum temperature at the center of the mortar when cured in a 20 °C constant temperature room was automatically measured with a thermocouple. · Neutralization depth: A specimen of 4×4×16 cm was prepared and cured in water at 20°C until the age of 28 days, then accelerated neutralization was carried out in an environment of 30°C, relative humidity of 60%, and carbon dioxide concentration of 5%. After 8 weeks, the specimen was cut into slices, and a phenolphthalein alcohol solution was sprayed on the cross-section to confirm the neutralization depth.

[0054]

Table 1

[0055] From Table 1, it can be seen that the expansive composition of the present invention imparts excellent expansive performance, has excellent neutralization resistance, and reduces the temperature at the center of the mortar. On the other hand, as in the comparative example, the Li-containing γ-2CaO·SiO2 alone does not show expansive performance, and the expansive agent alone does not show excellent neutralization resistance.

[0056] [Experimental Example 2] Similar experiments were also conducted when adjusting the Li2O content of Li-containing γ-2CaO·SiO2 in the expansive composition. The usage amount of the expansive composition was the same as that in Experimental Example 1. The results are also shown in Table 2.

[0057] <Materials Used> The Li-containing γ-2CaO·SiO2 was prepared in the same manner as in Experimental Example 1 except for changing the usage amount of reagent-grade lithium carbonate. · Li+γ-C2S b: Prototype, Li-containing γ-2CaO·SiO2, Blaine specific surface area is 4,000 cm 2 / g, Li2O amount 0.0005%. · Li+γ-C2S c: Prototype, Li-containing γ-2CaO·SiO2, Blaine specific surface area is 4,000 cm 2 / g, Li2O amount 0.001%. · Li+γ-C2S d: Prototype, Li-containing γ-2CaO·SiO2, Blaine specific surface area is 4,000 cm 2 / g, Li2O amount 0.5%. · Li+γ-C2S e: Prototype, Li-containing γ-2CaO·SiO2, Blaine specific surface area is 4,000 cm 2 / g, Li2O amount 1.0%. · Li+γ-C2S f: Prototype product, Li-containing γ-2CaO·SiO2, Blaine specific surface area 4,000 cm 2 / g, Li2O content 3.0%. · Expansion composition B: Prepared by mixing 50 parts by mass of Li+γ-C2S b and 50 parts by mass of expansion material I. · Expansion composition C: Prepared by mixing 50 parts by mass of Li+γ-C2S c and 50 parts by mass of expansion material I. · Expansion composition D: Prepared by mixing 50 parts by mass of Li+γ-C2S d and 50 parts by mass of expansion material I. · Expansion composition E: Prepared by mixing 50 parts by mass of Li+γ-C2S e and 50 parts by mass of expansion material I. · Expansion composition F: Prepared by mixing 50 parts by mass of Li+γ-C2S f and 50 parts by mass of expansion material I.

[0058]

Table 2

[0059] From Table 2, it can be seen that the expansion composition of the present invention can adjust the temperature at the center of the mortar by adjusting the Li2O content. Also, when the Li2O content is low, the neutralization resistance decreases due to the decrease in the purity of γ-2CaO·SiO2, and when the Li2O content is high, the temperature at the center of the mortar increases due to the promotion of cement hydration.

[0060] [Experimental Example 3] Similar experiments were also conducted when adjusting the free lime content of the expansion material in the expansion composition. The usage amount of the expansion composition was the same as in Experimental Example 1. The results are also shown in Table 3.

[0061] <Materials used> The prototype product of the expansion material was prepared by mixing and pulverizing limestone as the CaO raw material, bauxite as the Al2O3 raw material, silica as the SiO2 raw material, and anhydrous gypsum as the CaSO4 raw material to have a predetermined free lime content, and then firing at 1,200 °C to synthesize clinker, and using a ball mill to make the Blaine specific surface area 3,000 cm 2It was pulverized into / g to trial-produce a free lime - hydraulic compound - anhydrous gypsum - based expansion material. · Expansion material A: Trial product, free lime - hydraulic compound - anhydrous gypsum - based, Blaine specific surface area 3000 cm 2 / g. Free lime content 5%. · Expansion material B: Trial product, free lime - hydraulic compound - anhydrous gypsum - based, Blaine specific surface area 3000 cm 2 / g. Free lime content 10%. · Expansion material C: Trial product, free lime - hydraulic compound - anhydrous gypsum - based, Blaine specific surface area 3000 cm 2 / g. Free lime content 21%. · Expansion material D: Trial product, free lime - hydraulic compound - anhydrous gypsum - based, Blaine specific surface area 3000 cm 2 / g. Free lime content 39%. · Expansion material E: Trial product, free lime - hydraulic compound - anhydrous gypsum - based, Blaine specific surface area 3000 cm 2 / g. Free lime content 52%. · Expansion composition A: Prepared by mixing 50 parts by mass of Li + γ - C2S a and 50 parts by mass of expansion material A. · Expansion composition B: Prepared by mixing 50 parts by mass of Li + γ - C2S a and 50 parts by mass of expansion material B. · Expansion composition C: Prepared by mixing 50 parts by mass of Li + γ - C2S a and 50 parts by mass of expansion material C. · Expansion composition D: Prepared by mixing 50 parts by mass of Li + γ - C2S a and 50 parts by mass of expansion material D. · Expansion composition E: Prepared by mixing 50 parts by mass of Li + γ - C2S a and 50 parts by mass of expansion material E. · Expansion composition F: Prepared by mixing 50 parts by mass of Li + γ - C2S a and 50 parts by mass of expansion material F.

[0062]

Table 3

[0063] It can be seen from Table 3 that the expansion composition of the present invention can adjust the temperature at the center of the mortar by adjusting the amount of free lime. In addition, when the amount of free lime is small, the expansion performance decreases, and when the amount of free lime is large, the temperature at the center of the mortar increases.

Industrial Applicability

[0064] The expansion composition and cement composition of the present invention have temperature crack suppression due to heat of hydration, excellent dimensional stability, and carbonation resistance, and thus can be widely used for civil and architectural applications, contributing to extending the service life of concrete structures.

Claims

1. A cement admixture containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO₂, 3CaO·2SiO₂, α-CaO·SiO₂, and calcium magnesium silicate, and an expansive material, wherein Li is contained in the non-hydraulic compound, and the content rate of Li in the non-hydraulic compound is 0.001 to 1.0% by mass in terms of oxide conversion, and the Li is in a state where its presence can be confirmed by ICP emission spectrometry but Li₂O cannot be identified by X-ray diffraction measurement, an expansive composition.

2. A cement admixture containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO₂, 3CaO·2SiO₂, α-CaO·SiO₂, and calcium magnesium silicate, and an expansive material, As chemical components, in 100 parts by mass of the cement admixture, Li ２ O is 0.001 to 1 part by mass, CaO is 45 to 70 parts by mass, SiO ２ is 29 to 55 parts by mass, and Al ２ O ３ is contained in an amount of 0 to 10 parts by mass, and Li₂O contained as a chemical composition in the non-hydraulic compound is in a state where its presence can be confirmed by ICP emission spectrometry but Li₂O cannot be identified by X-ray diffraction measurement, an expansive composition.

3. The expansive composition according to claim 1 or 2, wherein the expansive material contains free lime, anhydrous gypsum, and a hydraulic compound.

4. The expansive composition according to claim 3, wherein the content rate of the free lime in the expansive material is 10 to 39% by mass.

5. A cement composition containing the expansive composition according to any one of claims 1 to 4 and cement.

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