Quick-setting admixture and quick-setting cement composition

Abstract

To provide an admixture material for repair material that has both rapid-hardening property and neutralization suppression effect, and furthermore moisture permeation resistance after neutralization.SOLUTION: Provided is a rapid-hardening admixture material which contains a cement admixture material, and alkali metal salt and / or alkaline earth metal salt, and in which the cement admixture material contains one kind of or two or more kinds of non-hydraulic compounds selected from a group consisting of γ-2CaO-SiO2, 3CaO-2SiO2, α-CaO-SiO2, and calcium magnesium silicate, and the non-hydraulic compound contains Li and a content ratio of the Li is 0.001 to 1.0 mass% in terms of oxide.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rapid hardening admixture and a rapid hardening cement composition used in the civil engineering field, the construction field, and the like.

Background Art

[0002] In recent years, the environments to which concrete structures are subjected have diversified, and there has been a demand for highly durable concrete that can respond to various environments from the perspective of the life cycle cost of the structures.

[0003] One of the important causes of reducing the durability of concrete is carbonation. Carbonation is a deterioration phenomenon caused by calcium hydroxide reacting with carbon dioxide in the atmosphere and being carbonated.

[0004] What becomes a problem due to the carbonation of concrete is, in particular, the rusting of the reinforcing bars used as a reinforcing material in reinforced concrete structures. Due to the expansion pressure when rusting occurs, the adhesion between the reinforcing bars and the concrete is impaired, cracks occur in the concrete, and this is one of the causes of impairing the durability of the concrete structure.

[0005] In addition, the concrete structures constructed during the period of high economic growth in Japan now require repair for deterioration such as carbonation, and it is expected that the number of places requiring repair will increase more and more in the future.

[0006] As a method for repairing deteriorated concrete, when it has progressed to cracks due to carbonation, a repair method such as chipping off the deteriorated part, removing the rust of the reinforcing bars, and then placing concrete again must be performed. The concrete used for the repair part is desired to be highly durable so that early deterioration does not occur.

[0007] In such repairs, a method has been proposed in which a cement composition composed of cement and a polymer is used to improve the adhesiveness to the repair surface and the crack resistance, and delay the progress of carbonation (see, for example, Patent Document 1).

[0008] However, in recent years, it has become clear that with regard to the corrosion of reinforcing bars in reinforced concrete structures, the penetration of moisture such as rainwater has a great influence on the corrosion of reinforcing bars. Thus, not only the neutralization suppression effect but also the water penetration resistance of neutralized concrete has become important.

[0009] In addition, in the repair of arterial roads and the like, in order to alleviate traffic congestion, early completion of construction is strongly desired, and materials with rapid hardening properties are required. For these reasons, the development of admixtures having both rapid hardening properties, a neutralization suppression effect, and further water penetration resistance after neutralization has been desired.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] Under the above circumstances, an object of the present invention is to provide a rapid hardening admixture having both rapid hardening properties, a neutralization suppression effect, and further water penetration resistance after neutralization, and a rapid hardening cement composition using the admixture.

Means for Solving the Problems

[0012] As a result of intensive studies to solve the above problems, by using a non-hydraulic compound containing Li in a predetermined ratio in combination with a rapid hardening component, the present inventors have developed a technique that exhibits a strength development property in a short time and a densification accompanying carbonation of the non-hydraulic composition, thereby exhibiting a neutralization suppression effect and further water penetration resistance after neutralization. The gist of the present invention is as follows. [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, wherein Li is contained in the non-hydraulic compound, and the content of Li is 0.001 to 1.0% by mass in terms of oxide, and a rapid-hardening admixture containing an alkali metal salt and / or an alkaline earth metal salt. [2]The rapid-hardening admixture according to [1] above, wherein the chemical composition in 100 parts by mass of the cement admixture contains 0.001 to 1.0 parts by mass of Li2O, 45 to 70 parts by mass of CaO, 29 to 54 parts by mass of SiO2, and 0 to 10 parts by mass of Al2O3. [3]The rapid-hardening admixture according to [1] or [2] above, wherein the alkali metal salt and the alkaline earth metal salt are nitrite and / or nitrate, respectively. [4]Furthermore, the rapid-hardening admixture according to any one of [1] to [3] above, which contains a hardening regulator, and the hardening regulator is one or more selected from the group consisting of inorganic carbonates, organic acids, and salts of the organic acids. [5]A rapid-hardening cement composition containing cement and the rapid-hardening admixture according to any one of [1] to [4] above. [Advantages of the Invention]

[0013] By using the rapid-hardening admixture and the rapid-hardening cement composition of the present invention, it is possible to provide an admixture having both rapid-hardening property and neutralization suppression effect, and further water penetration resistance after neutralization, and a cement composition using the admixture. [Embodiments for Carrying Out the Invention]

[0014] Hereinafter, the details of the present invention will be described. In addition, parts and % in this specification are based on mass unless otherwise specified.

[0015] [Rapid-Hardening Admixture] The rapid-hardening admixture of the present invention contains a cement admixture and an alkali metal salt and / or an alkaline earth metal salt.

[0016] <Cement admixture> The cement admixture according to this embodiment 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. Further, the cement admixture according to this embodiment further contains Li in the non-hydraulic compound, and the content rate thereof is 0.001 to 1.0% in terms of oxide. It is presumed that the production of vaterite, which is one kind of calcium carbonate, among the carbonation of C-S-H (calcium silicate hydrate) is promoted by this predetermined amount of Li, and it is considered that a denser hardened state is likely to be obtained by carbonation curing. From the viewpoint of being likely to exhibit the above effects, the content rate of Li is 0.001 to 1.0% in terms of oxide, preferably 0.005 to 1.0%, more preferably 0.010 to 0.90%, and even more preferably 0.015 to 0.80%. If the content rate of Li is less than 0.001% in terms of oxide, the carbonation promotion effect cannot be obtained. On the other hand, if it exceeds 1.0%, the cost will increase. The content rate of Li in terms of oxide can be measured by the method described in the examples. Here, "containing Li in the non-hydraulic compound" means a state in which Li2O is included as a chemical composition in the non-hydraulic compound (the presence can be confirmed by ICP emission spectrometry), but Li2O is not identified by X-ray diffraction measurement (no distinct peak of Li2O is seen), and it does not simply mean a state in which 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 and the like will be described.

[0017] (γ-2CaO·SiO2) γ-2CaO·SiO2 is a compound represented by 2CaO·SiO2 and is known as a low-temperature phase, which is completely different from the high-temperature phases such as α-2CaO·SiO2, α’-2CaO·SiO2, and β-2CaO·SiO2. Although all of them are represented by 2CaO·SiO2, their crystal structures and densities are different.

[0018] (3CaO·2SiO2) 3CaO·2SiO2 is a mineral containing CaO in pseudo-wollastonite and is called rankinite. It is a mineral that has no hydration activity and is chemically stable, but has a large carbonation promotion effect.

[0019] (α-CaO·SiO2) α-CaO·SiO2 (α-type 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 all of them are represented by CaO·SiO2, their crystal structures and densities are different.

[0020] Naturally occurring wollastonite is the low-temperature phase β-CaO·SiO2. β-CaO·SiO2 has acicular crystals and has been used as an inorganic fibrous substance such as wollastonite fiber, but it does not have the carbonation promotion effect like α-CaO·SiO2 according to this embodiment.

[0021] (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.

[0022] The non-hydraulic compound as described above may be one kind or two or more kinds. The content rate of Li in the non-hydraulic compound is as described above. When there are two or more non-hydraulic compounds, the content rate of Li refers to the content rate in terms of the oxide conversion of Li with respect to the total of two or more non-hydraulic compounds.

[0023] Among the above non-hydraulic compounds, in particular, γ-2CaO·SiO2 is preferable because it is accompanied by a pulverization phenomenon called dusting during production, so it requires less energy for pulverization than 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.

[0024] The non-hydraulic compound according to the present 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 at a high temperature of 1000 °C or higher. 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. From the reduction of 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 with a smaller amount of impurities compared to other industrial by-products. Examples of the SiO2 raw material include silica stone, clay, and various silica dusts generated as industrial by-products represented by silica fume and fly ash. Examples of the MgO raw material include magnesium hydroxide, basic magnesium carbonate, and dolomite. Examples of the Li raw material include lithium carbonate. When Li is contained in the CaO raw material, SiO2 raw material, and MgO raw material, it is not necessary to newly add an Li raw material.

[0025] As by - product slaked lime, there are by - product slaked lime by - produced in the production process of acetylene gas by the calcium carbide method (depending on the difference in the acetylene gas production method, there are wet products and dry products), and by - product slaked lime contained in the dust captured in the wet dust collection process of the calcium carbide electric furnace, such as acetylene by - product slaked lime. The by - product 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℃ - 515℃, CaCO3: around 650℃ - 765℃). The volume - average particle diameter measured by the laser diffraction / scattering method is about 50 - 100μm. 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.

[0026] The heat treatment at a high temperature of 1,000℃ 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℃, and often in the range of about 1,200 - 1,600℃.

[0027] This embodiment can also use industrial by - products containing the non - hydraulic compounds described above. In this case, impurities coexist. Such industrial by - products include steelmaking slag and the like.

[0028] 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. Further, examples of the 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, sulfur compounds such as the aforementioned CaS, A12S3, and CaC2·CaS, and the like.

[0029] 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. By being 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. Incidentally, S (sulfur) in the non-hydraulic compound may be present if it is about 2% in terms of oxide conversion.

[0030] Further, in this cement admixture, from the viewpoint of more easily expressing its effects, as the chemical composition, it is preferable to contain 0.001 to 1.0 part of Li2O, 45 to 70 parts of CaO, 29 to 54 parts of SiO2, and 0 to 10 parts of Al2O3 per 100 parts 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 fluorescence X-ray. As for the chemical composition, it is more preferable that in 100 parts of the cement admixture, Li2O is 0.002 to 0.5 part, CaO is 60 to 70 parts, SiO2 is 30 to 45 parts, and Al2O3 is 0.5 to 5 parts. Further, as the chemical composition, it is preferable that the total of Li2O, CaO, SiO2, and Al2O3 is 90 parts or more, and more preferably 95 to 100 parts, in 100 parts of the cement admixture.

[0031] As a method for quantifying the non-hydraulic compound in this admixture, examples include the Rietveld method by powder X-ray diffraction method.

[0032] The Blaine specific surface area of this 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 most preferable. When the Blaine specific surface area is 1,500 cm 2 / g or more, good material separation resistance can be obtained, and the carbonation promotion effect becomes sufficient. Also, when it is 8,000 cm 2 / g or less, the grinding power during grinding does not increase, which is economical, and weathering is suppressed, and deterioration of quality over time can be suppressed.

[0033] <Alkali metal salt and / or alkaline earth metal salt> The alkali metal salts and alkaline earth metal salts that can be used in the present invention are not particularly limited, and examples include nitrites, nitrates, sulfates, carbonates, acetates, etc. Among these, it is preferable that they are nitrites or nitrates. The nitrites and / or nitrates (hereinafter referred to as "nitrate salts") used in the present invention are not particularly limited as long as they impart flash setting when mixed with cement. Specifically, examples include alkali metal salts or alkaline earth metal salts of nitrites and nitrates. Among them, the use of lithium salts, sodium salts, potassium salts, and calcium salts is economically preferable. In the present invention, one or more of these can be used, but lithium salts and calcium salts are more preferred in that they do not promote the alkali-aggregate reaction. In particular, when lithium nitrite is used, the rapid hardening property is most remarkable and it is most preferred.

[0034] The amount of the alkali metal salt and / or alkaline earth metal salt used is not particularly limited, but is preferably 5 to 70 parts, more preferably 20 to 50 parts, per 100 parts of the rapid hardening admixture. When it is 5 parts or more, sufficient rapid hardening property can be obtained, and when it is 70 parts or less, the fluidity of the concrete is not impaired, which is advantageous in terms of construction.

[0035] <Hardening regulator> The rapid hardening admixture of the present invention may contain a hardening regulator. The hardening regulator is not particularly limited, but is preferably one or more selected from the group consisting of inorganic carbonates, organic acids, and salts of the organic acids. For example, as the inorganic carbonate, carbonates and bicarbonates of alkali metals can be mentioned, and as the organic acid, oxycarboxylic acids such as citric acid, tartaric acid, gluconic acid, malic acid, and alkali metal salts, alkaline earth metal salts, aluminum salts, ammonium salts, etc. of these can be mentioned.

[0036] The blending amount of the hardening regulator is not particularly limited, but it is usually preferably used within 5 parts, more preferably within 2 parts, and particularly preferably in the range of 0.1 part to 1 part, per 100 parts of the rapid hardening admixture. If the hardening regulator is insufficient, the workable time may be shortened, and if the hardening regulator is blended in excess, the strength development property may not be sufficient.

[0037] <Retarder> The rapid hardening admixture of the present invention may contain a retarder. The retarder used in the present invention is not particularly limited, but is for adjusting the setting of cement and not impairing the fluidity of the concrete during construction, and can also be called a setting regulator. As the retarder, either organic substances or inorganic substances can be used.

[0038] As specific examples of the organic substances, it is possible to use organic acids such as carboxylic acids, oxymonocarboxylic acids, oxy polycarboxylic acids, and polycarboxylic acids or their salts. The carboxylic acids are saturated or unsaturated carboxylic acids, and examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, and heptanoic acid. Examples of the oxymonocarboxylic acids include hepton acid, gluconic acid, and glycolic acid.

[0039] Examples of the oxy polycarboxylic acids include malic acid, tartaric acid, and citric acid. Examples of the polycarboxylic acids include co-condensates such as acrylic acid and maleic anhydride.

[0040] Furthermore, salts of the above-mentioned organic acids can also be used. For example, alkali metal salts such as lithium, sodium, and potassium, alkaline earth metal salts such as magnesium and calcium, and salts such as zinc, copper, aluminum, and ammonium salts can be mentioned.

[0041] As specific examples of the inorganic substances, inorganic acids such as phosphoric acid, hydrofluoric acid, and boric acid, phosphates, zinc oxide, lead oxide, silicofluorides such as magnesium silicofluoride and sodium silicofluoride, and fluorine-containing minerals such as cryolite and calcium fluoroaluminate can be used.

[0042] In the present invention, one or more of these can be used, but in particular, it is preferable to use citric acid or its salt, gluconic acid or its salt, tartaric acid or its salt, and the like.

[0043] The amount of the retarder used is not particularly limited, but it is preferably 0.1 to 10 parts, more preferably 0.3 to 5 parts, per 100 parts of the rapid hardening admixture.

[0044] [Rapid hardening cement composition] The rapid hardening cement composition in the present invention contains cement and the above-mentioned rapid hardening admixture. Although the amount of the rapid hardening admixture used in the rapid hardening cement composition of the present invention is not particularly limited, usually, 3 to 20 parts, preferably 7 to 15 parts, are preferred with respect to 100 parts of the cement composition composed of cement and the rapid hardening admixture. When it is 3 parts or more, the effects of the present invention can be sufficiently obtained, and when it is 20 parts or less, the long-term strength developability is not impaired.

[0045] <Cement> The cement used in the present invention is not particularly limited, but it is preferable to use a cement containing Portland cement. For example, various Portland cements such as ordinary, early strength, super early strength, low heat, or medium heat Portland cements, various blended cements obtained by mixing blast furnace slag, fly ash, or silica with these Portland cements, or limestone filler cements obtained by mixing limestone powder or the like with Portland cement can be mentioned.

[0046] In addition, in the present invention, it is also possible to mix fine aggregate into the rapid hardening cement composition composed of cement and the rapid hardening admixture of the present invention. The type of the fine aggregate is not particularly limited. For example, lime sand, silica sand, river sand, sea sand, mountain sand, crushed sand, etc. can be used, and the maximum particle size is preferably 5 mm or less, more preferably 2.5 mm or less.

[0047] In the present invention, in addition to aggregates such as sand and gravel, one or more of a water reducing agent, an AE water reducing agent, a high-performance water reducing agent, a high-performance AE water reducing agent, an antifoaming agent, a thickening agent, a rust preventive agent, an antifreezing agent, an expansion agent, a shrinkage reducing agent, a polymer emulsion, clay minerals such as bentonite and zeolite, and ion exchangers such as hydrotalcite can be used within a range that does not substantially inhibit the object of the present invention in the rapid hardening admixture and the rapid hardening cement composition of the present invention.

[0048] The amount of water used in the present invention is preferably 20 to 60 parts of water with respect to 100 parts of the rapid hardening cement composition. When the water is 20 parts or more, sufficient fluidity can be obtained, and when it is 60 parts or less, sufficient strength is ensured.

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

Examples

[0050] Experimental Example 1 (1) Preparation of cement admixtures Cement admixtures 1 to 15 were prepared as follows.

[0051] (1-1) Cement admixtures 1 to 3 (Li-containing γ-2CaO·SiO2) 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 as described in Table 1 (internal substitution) in terms of oxide (Li2O). The mixture was heat-treated at 1,400°C for 2 hours and left to cool to room temperature to obtain cement admixtures 1 to 3 with a Blaine specific surface area of 4,000 cm 2 / g.

[0052] (1-2) Cement admixtures 4 to 6 (Li-containing 3CaO·2SiO2) Reagent-grade calcium carbonate and reagent-grade silicon dioxide were mixed at a molar ratio of 3:2, and further, reagent-grade lithium carbonate was mixed so that the Li content in the mixture was as described in Table 1 (internal substitution) in terms of oxide (Li2O). The mixture was heat-treated at 1,400°C for 2 hours and left to cool to room temperature to obtain cement admixtures 4 to 6 with a Blaine specific surface area of 4,000 cm 2 / g.

[0053] (1-3) Cement admixtures 7 to 9 (Li-containing α-CaO·SiO2) Mix reagent grade calcium carbonate and reagent grade silicon dioxide in a molar ratio of 1:1, and further mix reagent grade lithium carbonate with the mixture so that the Li content is as described in Table 1 in terms of oxide (Li2O) (internal substitution). Heat-treat at 1,500 °C for 2 hours, leave to stand at room temperature, and a cement admixture 7-9 with a Blaine specific surface area of 4,000 cm 2 / g was prepared.

[0054] (1-4) Cement admixture 10-12 (Li-containing 3CaO·MgO·2SiO2) Mix reagent grade calcium carbonate, reagent grade magnesium oxide, and reagent grade silicon dioxide in a molar ratio of 3:1:2, and further mix reagent grade lithium carbonate with the mixture so that the Li content is as described in Table 1 in terms of oxide (Li2O) (internal substitution). Heat-treat at 1,400 °C for 2 hours, leave to stand at room temperature, and a cement admixture 10-12 with a Blaine specific surface area of 4,000 cm 2 / g was prepared.

[0055] (1-5) Cement admixture 13 (β-2CaO·SiO2) Mix reagent grade calcium carbonate and reagent grade silicon dioxide in a molar ratio of 2:1, heat-treat at 1,400 °C for 2 hours, leave to stand at room temperature, and repeat the same heat treatment until the peak of γ-2CaO·SiO2 is no longer confirmed by XRD after pulverization. After only the peak of β-2CaO·SiO2 is confirmed, a cement admixture 13 with a Blaine specific surface area of 4,000 cm 2 / g was prepared.

[0056] (1-6) Cement admixture 14 (γ-2CaO·SiO2) Mix reagent grade calcium carbonate and reagent grade silicon dioxide in a molar ratio of 2:1, heat-treat at 1,400 °C for 2 hours, leave to stand at room temperature, and a γ-2CaO·SiO2 with a Blaine specific surface area of 4,000 cm 2 / g was prepared.

[0057] (1-7) Cement admixture 15 (Li2O + γ-2CaO·SiO2) Mix reagent-grade calcium carbonate and reagent-grade silicon dioxide in a molar ratio of 2:1, heat-treat at 1,400 °C for 2 hours, leave to stand until room temperature, and obtain γ-2CaO·SiO2 with a Blaine specific surface area of 4,000 cm 2 / g. Also, heat-treat reagent-grade lithium carbonate at 1,400 °C for 2 hours, leave to stand until room temperature, and obtain Li2O powder. Mix the Li2O powder (obtained by heat-treating reagent-grade lithium carbonate at 1,400 °C for 2 hours) into the above γ-2CaO·SiO2 in an internal ratio so that the Li2O content is 0.1% (internal ratio replacement) to prepare a cement admixture.

[0058] The Li content in terms of oxides in each cement admixture was measured by an ICP emission spectrometer (VISTA-PRO, manufactured by Hitachi High-Technologies Corporation). And from the absolute calibration curve method using the diluted SPEX XSTC-22 ICP mixture solution, it was confirmed that the Li content was the same as the charged amount. The measurement conditions are as follows. · Li measurement wavelength: 670.783 nm · BG correction: Fitting curve method · Standard solution for calibration curve: Dilute the SPEX XSTC-22 ICP mixture solution and use it. Calibration curve range: 0 - 5 mg / L (five-point calibration curve of 0 mg / L, 0.1 mg / L, 0.5 mg / L, 1 mg / L, 5 mg / L) · Quantitative analysis by the absolute calibration curve method

[0059] (2) Evaluation of the carbonation reaction rate of the admixture Weigh 5 g of each admixture into an evaporating dish, and perform carbonation curing (room temperature 20 °C, relative humidity 60%, 5% - CO2 concentration) for 7 days according to JIS A 1153. After 7 days of carbonation curing, use differential thermal gravimetric analysis (NETZSCH, model 2020SA) to perform thermogravimetric analysis (TG) on a sample weight of 50 ± 2 mg, with a heating rate of 10 °C / min from room temperature to 1,000 °C under a nitrogen flow environment. The amount of CaCO3 generated (carbonation reaction rate) was calculated from the following formula for the carbonation reaction rate of each sample using the weight loss near 650 °C - 765 °C in the TG curve as the weight loss due to the decarbonation of CaCO3. The results are shown in Table 1. Carbonation reaction rate (%) = [Δm CaCO3 / (m0 - m 1,000 )] × 100.09 / 44.01 × 100 (Δm CaCO3 : Amount of decarbonation of calcium carbonate (mg), m0: Amount of sample used for measurement (mg), m 1,000 : Mass loss amount up to 1,000 °C (mg))

[0060] (3) Measurement of the amount of betalite by XRD measurement For the admixture after carbonation curing for 7 days, the amount of betalite was measured by powder X-ray diffraction (manufactured by Rigaku, SmartLab). A predetermined amount of an internal standard substance such as aluminum oxide or magnesium oxide was added to the cement admixture, and after thoroughly mixing in an agate mortar, powder X-ray diffraction measurement was carried out. The measurement results were analyzed with quantitative software to obtain the betalite content. "SmartlabStudio II" manufactured by Rigaku was used as the quantitative software. The results are shown in Table 1.

[0061]

Table 1

[0062] Experimental Example 2 (Experiment Nos. 2-1 to 2-31) 70 parts of the cement admixture shown in Table 1 and 30 parts of lithium nitrite were mixed to form a quick-setting admixture. Furthermore, using the quick-setting admixture with the composition shown in Table 2 and the remaining part as cement to make 100 parts, a mortar with a water / cement composition ratio = 50% and a cement composition / sand ratio = 1 / 3 was prepared, and the compressive strength and carbonation depth at ages of 1 day and 28 days were measured. The results are also shown in Table 2.

[0063] <Materials Used> Cement: Commercial product, ordinary Portland cement Nitrates: Commercial product, lithium nitrite Retarder: Commercial product, citric acid Water: Tap water Fine aggregate: Conforming to ISO679, standard sand

[0064] <Measurement Method> ·Compressive strength: Specimens of 4×4×16 cm were prepared, and the strengths at 1-day and 28-day ages were measured in accordance with JIS A 1108. The placing temperature was 20°C. ·Carbonation depth: Specimens of 4×4×16 cm were prepared, cured in water at 20°C until 28-day age, and then subjected to accelerated carbonation in an environment of 30°C, 60% relative humidity, and 10% carbon dioxide concentration. After 6 months, the specimens were cut into slices, a phenolphthalein solution was applied to the cross section, and the carbonation depth from the surface to the colored part was measured to evaluate the carbonation inhibition effect.

[0065]

Table 2

[0066] Experimental Example 3 (Experiment Nos. 3-1 to 3-9) 70 parts of the admixture types shown in Table 3 and 30 parts of lithium nitrite were blended, and retarders of the types and amounts shown in Table 3 were further blended to prepare a rapid-hardening admixture. Subsequently, the flow retention rate was evaluated using a composition consisting of 10 parts of the rapid-hardening admixture and 90 parts of cement. The results are shown in Table 3. Note that the other evaluation items are the same as those in the above Examples. ·Flow retention rate: Evaluated by the change over time of the flow value at an ambient temperature of 20°C. Calculated from the flow values immediately after mixing and after 30 minutes in accordance with the flow test of JIS R 5201. Flow retention rate = (Flow value after 30 minutes / Flow value immediately after remixing) × 100

[0067] <Materials used> Retarder A: Commercially available product, citric acid Retarder B: Commercially available product, gluconic acid Retarder C: Commercially available product, sodium gluconate Retarder D: Commercially available product, tartaric acid Retarder E: A 1:1 (mass ratio) mixture of retarder A and retarder D

[0068]

Table 3

[0069] Experimental Example 4 (Experiment Nos. 4-1 to 4-10) An evaluation was carried out on the resistance to substance (moisture) migration depending on the presence or absence of carbonation in the concrete to which the above rapid hardening admixture was added. Note that the specimens that had been carbonated were completely carbonated ones.

[0070] Using the rapid hardening admixtures shown in Table 4, in 100 parts of a cement composition consisting of ordinary cement and a rapid hardening admixture, the rapid hardening cement admixture was blended so as to have the usage amounts shown in Table 4, and cylindrical specimens of mortar Φ100×200 mm were produced according to JIS R 5201. The side surfaces of the specimens were sealed with aluminum tape, and the upper and lower surfaces were left open. The water absorption method was to immerse the lower 1 cm of the specimens in a water bath, split them 24 hours after immersion, and measure the penetration depth of moisture using calipers. The results are shown in Table 4.

[0071] [Table 4]

[0072] From the results in Table 1, it can be seen that the rapid hardening admixture of the present invention has a high carbonation reaction rate and a high amount of ettringite formation. Also, from the results in Table 2, it can be seen that the mortar prepared using these rapid hardening admixtures of the present invention has a high compressive strength and a small carbonation depth. That is, it can be seen that by using the rapid hardening admixture of the present invention, strength development in a short time and good carbonation resistance are exhibited. On the other hand, it can be seen that in Cement Admixtures 13 to 15 presented as comparative examples, the compressive strength is small and the carbonation depth is deep. Also, from the results in Table 3, it can be seen that by adding a retarder, the flow retention rate becomes good. Furthermore, from the results in Table 4, it can be seen that the rapid hardening cement composition using the rapid hardening admixture of the present invention has a shallow moisture penetration depth and excellent moisture penetration resistance.

Industrial Applicability

[0073] According to the rapid hardening admixture and rapid hardening cement composition of the present invention, it is possible to achieve the development of short-term strength and exhibit an excellent carbonation inhibition effect. Furthermore, since it also has excellent water penetration resistance after carbonation, it is particularly suitable as a repair material for concrete materials in civil engineering or construction.

Claims

Claim 1 γ-2CaO·SiO ２ , 3CaO·2SiO ２ , α-CaO·SiO ２ , and a cement admixture containing one or more non-hydraulic compounds selected from the group consisting of calcium magnesium silicate, wherein the non-hydraulic compound contains Li, and the content of Li is 0.001 to 1.0% by mass in terms of oxide, and the cement admixture contains an alkali metal salt and / or an alkaline earth metal salt, and Li contained as a chemical composition in the non-hydraulic compound ２ O can be confirmed to be present by ICP emission spectroscopic analysis, but Li ２ O cannot be identified by X-ray diffraction measurement, a rapid hardening admixture. Claim 2 As the chemical composition in 100 parts by mass of the cement admixture (however, excluding the cement admixture in which the non-hydraulic compound and the Li compound are physically mixed), Li ２ O is 0.001 to 1.0 part by mass, CaO is 45 to 70 parts by mass, SiO ２ is 29 to 54 parts by mass, and Al ２ O ３ is 0 to 10 parts by mass, The rapid-hardening admixture according to claim 1. Claim 3 The accelerating admixture according to claim 1 or 2, wherein the alkali metal salt and the alkaline earth metal salt are nitrite and / or nitrate, respectively. Claim 4 The accelerating admixture according to any one of claims 1 to 3, further comprising a setting regulator, wherein the setting regulator is one or more selected from the group consisting of inorganic carbonates, organic acids, and salts of the organic acids. Claim 5 An accelerating cement composition comprising cement and the accelerating admixture according to any one of claims 1 to 4.

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