Rapidly hardening mixed material and rapidly hardening seminant composition

Abstract

To provide a quick-hardening admixture that can express strength in a short time and can prevent the penetration of a degradation factor, and a quick-hardening cement composition.SOLUTION: A quick-hardening admixture contains a cement admixture containing at least one non-hydraulic compound selected from the group consisting of γ-2CaO SiO2, 3CaO 2SiO2, α-CaO SiO2, and calcium magnesium silicate, where the non-hydraulic compound contains Li, the content of the Li being 0.001-1.0 mass% in terms of oxide, a calcium aluminate and a gypsum.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rapid-hardening admixture and a rapid-hardening cement composition for use in the fields of civil engineering, construction, etc. [Background technology]

[0002] In new road construction or repair work, early reopening is desirable from the perspective of traffic improvement, so cement concrete, mainly made of Portland cement or the like, needs to harden within a few minutes to a few tens of minutes after being poured into a formwork, and needs to have rapid hardening properties that allow it to develop a practical strength that allows it to be demolded within a few hours. Rapid hardening materials have been developed as materials that impart this rapid hardening property, and are widely used in emergency construction such as highway pavement concrete, as well as in emergency repair mortars and grout-based mortars (see Patent Documents 1 to 3).

[0003] For example, Patent Document 1 discloses a technique for developing in one hour the short-term strength that previously required 3 to 6 hours, using a rapid-hardening cement made from calcium aluminate and gypsum, and a composition made from sulfates, carbonates, and carboxylates, as well as a rapid-hardening cement composition in which the mineral composition of cement clinker is adjusted, as disclosed in Patent Document 2. Patent Document 3 also discloses a technique for controlling the rapid-hardening rate by coating the surface of gypsum particles with fatty acids and controlling the solubility of the gypsum.

[0004] The rapid hardening cement admixtures mentioned above have been developed and designed to meet practical strength requirements within a short time period, and there has been insufficient discussion of their long-term strength or durability.

[0005] However, in recent years, the environments in which concrete structures are used have become more diverse, and from the perspective of life cycle costs, there is a growing demand for highly durable concrete structures that can be adapted to various environments.

[0006] Carbonation is a typical example of deterioration in concrete structures. Carbonation is a deterioration phenomenon in which carbon dioxide in the atmosphere reduces the alkalinity of concrete and destroys the passive film around the rebar. When the passive film is destroyed, deterioration factors such as moisture and salt can penetrate into the concrete, accelerating the corrosion of the rebar.

[0007] Therefore, when considering the long-term use of structures, it is important for rapid hardening cement concrete not only to develop short-term strength, but also to suppress the penetration of deterioration factors into the carbonated hardened concrete.

[0008] Patent Document 4 describes a method for suppressing deterioration factors in carbonated hardened concrete. It involves forcibly carbonate-curing concrete containing a non-hydraulic compound such as γ-C2S (γ-2CaO·SiO2; also known as the γ phase of belite) as an admixture. This results in a highly durable concrete product with a denser surface layer due to CO2 absorption. γ-C2S does not undergo a hydration reaction, but reacts with CO2 to produce a gel rich in CaCO3 and SiO2. These products fill voids in the cement matrix, dramatically improving the durability of the surface layer of the concrete product.

[0009] However, in the case of high-durability concrete containing a non-hydraulic compound such as γ-C2S shown in Patent Document 4, it is assumed that the structure to be cured is placed in a shielded space where a predetermined carbon dioxide concentration can be maintained. Therefore, in order to cure huge concrete structures that cannot be contained in curing facilities, such as road pavement concrete and repair mortar, a cement admixture that can further promote the carbonation (salt) of the compounded non-hydraulic compound is required. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Special Publication No. 49-30683 [Patent Document 2] Japanese Patent Application Publication No. 03-12350 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-68795 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-182583 Summary of the Invention [Problem to be solved by the invention]

[0011] Under the circumstances described above, an object of the present invention is to provide a rapid-hardening mineral admixture and a rapid-hardening cement composition that can exhibit short-term strength and inhibit the penetration of deterioration factors. [Means for solving the problem]

[0012] As a result of extensive research aimed at solving the above problems, we have developed a technology that combines a non-hydraulic compound containing a predetermined proportion of Li with a rapid hardening component, thereby achieving both rapid strength development and the effect of inhibiting the penetration of deterioration factors by densifying the hardened body through the promotion of carbonation of the non-hydraulic composition. [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 the non-hydraulic compound contains Li, and the Li content is 0.001 to 1.0 mass% in terms of oxide. A rapid-hardening admixture containing calcium aluminates and gypsums. [2] The rapid-hardening admixture according to [1] above, containing, as a chemical composition per 100 parts by mass of the cement admixture, 0.001 to 1.0 part 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, further comprising a hardening regulator, wherein the hardening regulator is one or more selected from the group consisting of inorganic carbonates, organic acids, and salts of the organic acids. [4] A rapid-hardening cement composition comprising cement and the rapid-hardening admixture according to any one of [1] to [3] above. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a rapid-hardening admixture and a rapid-hardening cement composition that are capable of developing short-term strength and suppressing the penetration of deterioration factors. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. In this specification, parts and percentages are by mass unless otherwise specified.

[0015] [Rapid hardening admixture] The rapid-hardening admixture of the present invention comprises a cement admixture, calcium aluminates, and gypsums.

[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·SiO 2 , 3CaO·2SiO 2 , α-CaO·SiO 2 , and calcium magnesium silicate. Furthermore, the cement admixture according to this embodiment is characterized in that the non-hydraulic compound further contains Li, with a content of 0.001 to 1.0% in terms of oxide. Carbonation of CSH (calcium silicate hydrate) progresses during the curing process, and it is presumed that this predetermined amount of Li promotes the production of vaterite, a type of calcium carbonate, during the carbonation of CSH (calcium silicate hydrate). It is believed that a denser hardened state can be more easily obtained by carbonation (salt) curing. The dense hardened state is believed to be the key to the development of short-term strength. From the viewpoint of easily achieving the above-mentioned effects, the Li content 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 Li content 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 becomes high. The Li content in terms of oxide can be measured by the method described in the Examples. Here, "Li contained in a non-hydraulic compound" refers to a state in which the non-hydraulic compound contains Li2O as a chemical composition (its presence can be confirmed by ICP atomic emission spectroscopy), but Li2O is not identified by X-ray diffraction measurement (no clear Li2O peak is observed), and does not simply refer to a state in which the non-hydraulic compound and the Li compound are physically mixed. This state can be achieved by mixing the respective raw materials and heat treating them at high temperatures of 1,000°C or higher. Each component will be explained below.

[0017] (γ-2CaO·SiO2) γ-2CaO SiO2 is known as a low-temperature phase of the compound 2CaO SiO2, and is completely different from the high-temperature phases α-2CaO SiO2, α'-2CaO SiO2, and β-2CaO SiO2. Although all of these are expressed as 2CaO SiO2, they have different crystal structures and densities.

[0018] (3CaO 2SiO2) 3CaO·2SiO2 is a mineral called rankinite, which is a pseudowollastonite containing CaO. It is a chemically stable mineral with no hydration activity, but has a strong effect in promoting carbonation.

[0019] (α-CaO SiO2) α-CaO·SiO2 (α-type wollastonite) is known as a high-temperature phase among the compounds expressed as CaO·SiO2, and is completely different from the low-temperature phase β-CaO·SiO2. Although both are expressed as CaO·SiO2, they have different crystal structures and densities. Naturally occurring wollastonite is a low-temperature phase of β-CaO SiO2. β-CaO SiO2 has needle-like crystals and is used as an inorganic fibrous material such as wollastonite fiber, but it does not have the carbonation-promoting effect of the α-CaO SiO2 of this embodiment.

[0020] (Calcium Magnesium Silicate) Calcium magnesium silicate is a general term for CaO-MgO-SiO2 compounds, but in this embodiment, merwinite represented by 3CaO·MgO·2SiO2 (C3MS2) is preferred, as merwinite achieves a significant carbonation (salt) promotion effect.

[0021] The non-hydraulic compound may be one type or two or more types, but the Li content in the non-hydraulic compound is as described above. When there are two or more types of non-hydraulic compounds, the Li content refers to the content of Li in terms of oxide relative to the total of the two or more types of non-hydraulic compounds.

[0022] Of the non-hydraulic compounds mentioned above, γ-2CaO·SiO2 is particularly preferred because it requires less energy to grind than other compounds due to the powdering phenomenon known as dusting that occurs during production, it has a significant effect of promoting carbonation over the long term, and when combined with blast furnace cement at a low water-binder ratio, it has a very significant effect of inhibiting carbonation.

[0023] 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 a Li raw material in a predetermined molar ratio and heat treating the mixture at a high temperature of 1000°C or higher. Examples of CaO raw materials 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 lumps. To reduce 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 lumps, municipal waste incineration ash, and sewage sludge incineration ash, can be used. Among these, the use of by-product slaked lime, which contains fewer impurities than other industrial by-products, is even more preferable. Examples of SiO2 raw materials include silica stone, clay, and various siliceous dusts generated as industrial by-products, such as silica fume and fly ash. Examples of MgO raw materials include magnesium hydroxide, basic magnesium carbonate, and dolomite. In addition, examples of Li raw materials include lithium carbonate, etc. If Li is contained in the CaO raw material, SiO2 raw material, or MgO raw material, there is no need to add a new Li raw material.

[0024] Examples of by-product slaked lime include by-product slaked lime produced during the acetylene gas production process using the calcium carbide method (wet and dry types are available depending on the acetylene gas production method), and by-product slaked lime contained in the dust captured during the wet dust collection process of a calcium carbide electric furnace. By-product slaked lime contains, for example, 65 to 95% (preferably 70 to 90%) calcium hydroxide, 1 to 10% calcium carbonate, and 0.1 to 6.0% (preferably 0.1 to 3.0%) iron oxide. These proportions can be confirmed by X-ray fluorescence measurement and mass loss determined by differential thermogravimetric analysis (TG-DTA) (Ca(OH)2: approximately 405 to 515°C, CaCO3: approximately 650 to 765°C). The volume-average particle size measured by laser diffraction / scattering is approximately 50 to 100 μm. Furthermore, the moisture content measured by the loss on drying method in JIS K 0068 "Method for measuring moisture content in chemical products" is preferably 10% or less. Also, sulfur compounds such as CaS, A12S3, and CaC2·CaS may be contained, but the content is preferably 2% or less.

[0025] The heat treatment at a high temperature of 1,000°C or higher as described above is not particularly limited, but can be carried out, for example, in a rotary kiln, an electric furnace, etc. The heat treatment temperature is not uniquely determined, but is usually carried out in the range of about 1,000 to 1,800°C, and often in the range of about 1,200 to 1,600°C.

[0026] In this embodiment, industrial by-products containing the aforementioned non-hydraulic compounds can also be used. In this case, impurities coexist. Examples of such industrial by-products include steel slag.

[0027] The CaO raw material, SiO2 raw material, and MgO raw material may contain impurities, but these do not pose any particular problems as long as they do not impair the effects of the present invention. Specific examples of impurities include Al2O3, Fe2O3, TiO2, MnO, Na2O, KO, S, PO5, F, BO3, and chlorine. Coexisting compounds include free calcium oxide, calcium hydroxide, calcium aluminate, calcium aluminosilicate, calcium ferrite, calcium aluminoferrite, calcium phosphate, calcium borate, magnesium silicate, leucite (KO, Na2O)·Al2O3·SiO2, spinel MgO·Al2O3, magnetite Fe3O4, and sulfur compounds such as CaS, Al2S3, and CaC2·CaS.

[0028] Of 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 even more preferably 0.5% or less, calculated as oxide (SO3). A content of 1.0% or less provides a sufficient carbonation (salt) promotion effect and also allows the setting and hardening properties to be within an appropriate range. The S content calculated as oxide (SO3) can be measured by X-ray fluorescence measurement. Note that S (sulfur) may be present in the non-hydraulic compound at a concentration of about 2% calculated as oxide.

[0029] To more easily exert its effects, the cement admixture preferably contains, as a chemical composition, 0.001 to 1.0 part Li2O, 45 to 70 parts CaO, 29 to 54 parts SiO2, and 0 to 10 parts Al2O3 per 100 parts of the cement admixture. The Li2O content can be measured by the method described in the Examples below. The CaO, SiO2, and Al2O3 contents can be measured by fluorescent X-rays. As for the chemical composition, it is more preferable that the cement admixture contains 0.002 to 0.5 parts of Li2O, 60 to 70 parts of CaO, 30 to 45 parts of SiO2, and 0.5 to 5 parts of Al2O3 per 100 parts of the cement admixture. Furthermore, as for the chemical composition, it is preferable that the total amount of Li2O, CaO, SiO2, and Al2O3 per 100 parts of the cement admixture is 90 parts or more, and more preferably 95 to 100 parts.

[0030] The Rietveld method using powder X-ray diffraction may be used as a method for quantifying the non-hydraulic compounds in the present admixture.

[0031] The Blaine specific surface area of ​​this cement admixture is not particularly limited, but is preferably 1,500 cm 2 / g or more is preferable, and the upper limit is 8,000 cm 2 / g or less is preferable. 2 / g is more preferable, and 4,000 to 6,000 cm 2 / g is most preferable. 2 / g or more, good resistance to material separation is obtained, and the carbonation (salt) promotion effect is sufficient. 2 / g or less, the grinding power required for grinding is not large, which is economical, and weathering can be suppressed, thereby preventing deterioration of quality over time.

[0032] <Calcium aluminates> Calcium aluminates are a general term for compounds primarily composed of CaO and Al2O3, and are not particularly limited. Specific examples include CaO·2Al2O3, CaO·Al2O3, 12CaO·7Al2O3, 11CaO·7Al2O3·CaF2, 3CaO·Al2O3, 3CaO·3Al2O3·CaSO4, and amorphous substances primarily composed of CaO and Al2O3.

[0033] The method for industrially producing these calcium aluminates is not particularly limited, but examples of the CaO raw material include calcium carbonate such as limestone or shells, calcium hydroxide such as slaked lime, and calcium oxide such as quicklime, and examples of the Al2O3 raw material include bauxite, aluminum dross, and aluminum ash residue, etc. One example is a method in which these CaO raw materials and Al2O3 raw materials are mixed and heat-treated at a high temperature of 1,000°C or higher.

[0034] When these calcium aluminates are obtained industrially, they may contain impurities, such as SiO2, Fe2O3, MgO, TiO2, MnO, Na2O, KO, Li2O, S, PO, and BO3.

[0035] Compounds may include calcium aluminoferrites such as 4CaO·Al2O3·Fe2O3, 6CaO·2Al2O3·Fe2O3, and 6CaO·Al2O3·2Fe2O3; calcium ferrites such as 2CaO·Fe2O3 and CaO·Fe2O3; calcium aluminosilicates such as gehlenite (2CaO·Al2O3·SiO2) and anorthite (CaO·Al2O3·2SiO2); calcium magnesium silicates such as merwinite (3CaO·MgO·2SiO2), akermanite (2CaO·MgO·2SiO2), and monticellite (CaO·MgO·SiO2); calcium silicates such as tricalcium silicate (3CaO·SiO2), dicalcium silicate (2CaO·SiO2), rankinite (3CaO·2SiO2), and wollastonite (CaO·SiO2); free lime; and leucite (K2O, Na2O)·Al2O3·SiO2. In the present invention, these crystalline and amorphous materials may be present together.

[0036] The particle size of calcium aluminates is not particularly limited, but is usually 3,000 to 8,000 cm 2 / g is preferred, and 4,000 to 7,000 cm 2 / g is more preferable. 2 / g or more, sufficient rapid hardening is exhibited, and 2 If the viscosity is less than 1 / g, sufficient working life can be ensured.

[0037] <Gypsum> The term "gypsums" used in the present invention collectively refers to anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum, and any of these can be used. These can also be used alone or in combination. Among these, anhydrous gypsum is preferred from the viewpoint of strength development.

[0038] The particle size of gypsum is not particularly limited, but is usually 3,000 to 8,000 cm 2 / g is preferred, and 4,000 to 7,000 cm 2 / g is more preferable. 2 / g or more, sufficient strength is obtained and abnormal expansion does not occur over the long term. 2 Even if the dose exceeds 100mg / g, no further improvement in effect can be expected.

[0039] The blending ratio of each material in the rapid-hardening admixture of the present invention is not particularly limited, but typically, per 100 parts of a rapid-hardening admixture consisting of a non-hydraulic substance, calcium aluminates, and gypsums, the non-hydraulic substance is preferably 10 to 80 parts, more preferably 20 to 70 parts. The calcium aluminates are preferably 10 to 45 parts, more preferably 15 to 40 parts. The gypsums are preferably 5 to 45 parts, more preferably 15 to 40 parts.

[0040] In the above formulation, if the non-hydraulic substance is 10 parts or more, the hardened body becomes sufficiently dense, and if it is 80 parts or less, sufficient rapid hardening is obtained. Furthermore, if the calcium aluminates are 10 parts or more, sufficient rapid hardening is obtained, and if it is 45 parts or less, sufficient densification effect is obtained. Furthermore, if the gypsums are 5 parts or more, sufficient strength development is obtained, and if it is 45 parts or less, sufficient carbonation inhibition effect is obtained and abnormal expansion does not occur over the long term.

[0041] <Cure adjuster> The rapid hardening admixture of the present invention may contain a hardening adjuster. The hardening adjuster is not particularly limited, but is preferably one or more selected from the group consisting of inorganic carbonates, organic acids and salts of said organic acids. For example, inorganic carbonates include alkali metal carbonates and bicarbonates, and organic acids include oxycarboxylic acids such as citric acid, tartaric acid, gluconic acid, and malic acid, as well as alkali metal salts, alkaline earth metal salts, aluminum salts, and ammonium salts thereof.

[0042] The amount of set modifier to be added is not particularly limited, but it is usually used in the range of 2 parts or less per 100 parts of the rapid-hardening admixture, and is often used in the range of 0.1 to 1 part. If the amount of set modifier is insufficient, the usable time may be shortened, and if too much set modifier is added, the strength development may be insufficient.

[0043] [Rapid hardening cement composition] The rapid-hardening cement composition of the present invention comprises cement and the above-mentioned rapid-hardening admixture. <Cement> Examples of cement that can be used in the present invention include various types of Portland cement, such as ordinary, early-strength, extra-early-strength, low-heat, and medium-heat cements; various mixed cements in which blast furnace slag, fly ash, or silica is mixed with these Portland cements; waste-recycled cements (ecocements) produced using municipal waste incineration ash, sewage sludge incineration ash, and the like as raw materials; and various filler cements in which limestone powder, slowly cooled blast furnace slag powder, or the like is mixed; and one or more of these can be used.

[0044] The amount of the rapid-hardening admixture of the present invention used is not particularly limited, but is usually preferably 30 to 70 parts, more preferably 40 to 60 parts, per 100 parts of cement composition consisting of cement and the rapid-hardening admixture. If the amount of rapid-hardening admixture used is too small, sufficient rapid hardening and carbonation resistance may not be obtained, and if the amount of rapid-hardening admixture used is too excessive, sufficient rapid hardening and carbonation resistance tend not to be obtained, and in particular, carbonation resistance will be significantly reduced.

[0045] <Fine aggregate> The fine aggregate used in preparing a mortar from the cement composition of the present invention is not particularly limited, but typically includes natural aggregates such as silica or limestone, fine aggregates made from slowly cooled blast furnace slag, and recycled fine aggregates. Recently, steelmaking slag aggregates such as electric furnace oxidizing slag and converter slag have also been considered. One or more of these aggregates can be used in combination.

[0046] The amount of fine aggregate used is not particularly limited, but can usually be used in a mass ratio of cement composition to fine aggregate of 1:3 or less, and is often used in a mass ratio of 1:2 or less. If a large amount of fine aggregate is used, kneading properties and workability may be impaired. If necessary, coarse aggregate may be added to the mortar composition of the present invention to produce a rapid-hardening concrete.

[0047] <Other additives, etc.> In the present invention, additives such as expansion agents, water reducing agents, air-entraining water reducing agents, high-performance water reducing agents, high-performance air-entraining water reducing agents, antifoaming agents, thickeners, rust inhibitors, antifreeze agents, shrinkage reducing agents, polymers, fibrous materials such as steel fiber, vinylon fiber and carbon fiber, clay minerals such as bentonite, anion exchangers such as hydrotalcite, and admixtures such as ground granulated blast furnace slag, ground slowly cooled blast furnace slag, ground limestone, fly ash and silica fume can be used alone or in combination of two or more additives and admixtures that are commonly used in cement materials.

[0048] In the present invention, the method of mixing the materials and water is not particularly limited, and the materials may be mixed at the time of application, or some or all of the materials may be mixed in advance. Also, some of the materials may be mixed with water and then the remaining materials may be mixed. [Example]

[0049] Experimental Example 1 (1) Preparation of cement admixture Cement admixtures 1 to 15 were prepared as follows. (1-1) Cement admixture 1~3 (Li-containing γ-2CaO SiO2) First-grade reagent calcium carbonate and first-grade reagent silicon dioxide were mixed in a molar ratio of 2:1, and then first-grade reagent lithium carbonate was added to the mixture so that the Li content in the mixture, converted to oxide (LiO), was as shown in Table 1 (internal substitution). The mixture was then heat-treated at 1,400°C for 2 hours and allowed to cool to room temperature to produce a mixture with a Blaine specific surface area of ​​4,000 cm. 2 / g cement admixtures 1 to 3 were prepared.

[0050] (1-2) Cement admixture 4-6 (Li-containing 3CaO·2SiO2) First-grade reagent calcium carbonate and first-grade reagent silicon dioxide were mixed in a molar ratio of 3:2, and then first-grade reagent lithium carbonate was added to the mixture so that the Li content in the mixture, converted to oxide (LiO), was as shown in Table 1 (internal substitution). The mixture was then heat-treated at 1,400°C for 2 hours and allowed to cool to room temperature to produce a mixture with a Blaine specific surface area of ​​4,000 cm. 2 / g cement admixtures 4 to 6 were prepared.

[0051] (1-3) Cement admixture 7~9 (α-CaO SiO2 containing Li) First-grade reagent calcium carbonate and first-grade reagent silicon dioxide were mixed in a 1:1 molar ratio, and then first-grade reagent lithium carbonate was added to the mixture so that the Li content in the mixture, converted to oxide (LiO), was as shown in Table 1 (internal substitution). The mixture was then heat-treated at 1,500°C for 2 hours and allowed to cool to room temperature to produce a mixture with a Blaine specific surface area of ​​4,000 cm. 2 / g cement admixtures 7 to 9 were prepared.

[0052] (1-4) Cement admixture 10-12 (Li-containing 3CaO·MgO·2SiO2) First-grade reagent calcium carbonate, first-grade reagent magnesium oxide, and first-grade reagent silicon dioxide were mixed in a molar ratio of 3:1:2, and then first-grade reagent lithium carbonate was added to the mixture so that the Li content in the mixture, converted to oxide (LiO), was as shown in Table 1 (internal substitution). The mixture was then heat-treated at 1,400°C for 2 hours and allowed to cool to room temperature to produce a mixture with a Blaine specific surface area of ​​4,000 cm. 2 / g cement admixtures 10 to 12 were prepared.

[0053] (1-5) Cement admixture 13 (β-2CaO·SiO2) First-grade reagent calcium carbonate and first-grade reagent silicon dioxide were mixed in a 2:1 molar ratio, heat-treated at 1,400°C for 2 hours, allowed to cool to room temperature, crushed, and then repeatedly heat-treated until the peaks of γ-2CaO SiO2 were no longer detected by XRD. After the peaks of only β-2CaO SiO2 were detected, the Blaine specific surface area was found to be 4,000 cm 2 / g cement admixture 13 was prepared.

[0054] (1-6) Cement admixture 14 (γ-2CaO·SiO2) First-grade reagent calcium carbonate and first-grade reagent silicon dioxide were mixed in a molar ratio of 2:1, heat-treated at 1,400°C for 2 hours, and allowed to cool to room temperature to produce a mixture with a Blaine specific surface area of ​​4,000 cm. 2 / g of γ-2CaO·SiO2 was prepared.

[0055] (1-7) Cement admixture 15 (Li2O + γ-2CaO·SiO2) First-grade reagent calcium carbonate and first-grade reagent silicon dioxide were mixed in a molar ratio of 2:1, heat-treated at 1,400°C for 2 hours, and allowed to cool to room temperature to produce a mixture with a Blaine specific surface area of ​​4,000 cm. 2 / g of γ-2CaO·SiO2 was prepared. In addition, first-grade reagent lithium carbonate was heat-treated at 1,400°C for 2 hours and then allowed to cool to room temperature to produce Li2O powder. A cement admixture was prepared by mixing Li2O powder (reagent-grade lithium carbonate heat-treated at 1,400°C for 2 hours) with the above γ-2CaO·SiO2 so that the Li2O content was 0.1% (internal substitution).

[0056] The oxide-equivalent Li content of each cement admixture was measured using an ICP optical emission spectrometer (VISTA-PRO, manufactured by Hitachi High-Tech Science Corporation). The absolute calibration curve method using a diluted SPEX XSTC-22 ICP mixture was used to confirm that the Li content was the same as the amount charged. The measurement conditions were as follows: ·Li measurement wavelength: 670.783nm BG correction: Fitting curve method Calibration standard solution: Dilute SPEX XSTC-22 ICP mixture. Calibration range: 0-5 mg / L (5 calibration points: 0 mg / L, 0.1 mg / L, 0.5 mg / L, 1 mg / L, 5 mg / L). Quantitative analysis using absolute calibration curve method

[0057] (2) Evaluation of carbonation reaction rate of admixture Five grams of each admixture was weighed into an evaporating dish and carbonation-cured for seven days according to JIS A 1153 (room temperature 20°C, relative humidity 60%, 5% CO2 concentration). After seven days of carbonation curing, thermogravimetric analysis (TG) was performed using a differential thermogravimetric analyzer (NETZSCH, Model 2020SA) with a sample weight of 50 ± 2 mg, heating from room temperature to 1,000°C at a rate of 10°C / min under a nitrogen flow. The amount of CaCO3 produced (carbonation reaction rate) was calculated using the following equation, taking the weight loss in the TG curve between 650°C and 765°C as the weight loss due to 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 decarbonated calcium carbonate (mg), m0: amount of sample used for measurement (mg), m 1,000 : Mass loss up to 1,000°C (mg)

[0058] (3) Measurement of vaterite content by XRD measurement The vaterite content of the admixture after the seven-day carbonation curing was measured using powder X-ray diffraction (Rigaku Corporation, SmartLab). A predetermined amount of an internal standard substance such as aluminum oxide or magnesium oxide was added to the cement admixture, and after thorough mixing in an agate mortar, powder X-ray diffraction measurements were performed. The measurement results were analyzed using quantitative software to determine the vaterite content. The quantitative software used was Rigaku Corporation's "SmartlabStudio II." The results are shown in Table 1.

[0059] [Table 1]

[0060] Experimental Example 2 Rapid-hardening admixtures (rapid-hardening admixtures 1 to 31) were prepared by blending non-hydraulic compounds, calcium aluminate, and gypsum as shown in Table 2. Mortars were prepared using these rapid-hardening admixtures in accordance with JIS R 5201, using 50 parts of the rapid-hardening admixture in 100 parts of a cement composition consisting of normal cement and the rapid-hardening admixture. The compressive strength, carbonation depth, and compressive strength after carbonation were evaluated. The results are also shown in Table 2.

[0061] <Materials used> Ordinary cement: Ordinary Portland cement, manufactured by Denka Co., Ltd., specific gravity 3.15 Water: Tap water Fine aggregate: Silica aggregate, standard sand used in JIS R 5201, specific gravity 2.62 Gypsum: Natural anhydrous gypsum pulverized product, Blaine specific surface area 5,000 cm 2 / g Calcium aluminate: Amorphous calcium aluminate. 12 moles of calcium carbonate and 7 moles of aluminum oxide were mixed and fired at 1,350°C for 3 hours. This process was repeated twice to synthesize 12CaO 7Al2O3. 3% silica was added to the resulting mixture, which was then melted at 1,650°C and rapidly cooled. The Blaine specific surface area was 5,000 cm 2 / g.

[0062] <Measurement method> Compressive strength: A hardened specimen measuring 10cm diameter x 20cm was prepared, and the compressive strength after 6 hours was measured in accordance with JIS R 5201. Carbonation depth (accelerated carbonation test): 10cm diameter x 20cm hardened specimens were cured underwater at 20°C until they reached the age of 28 days, and then accelerated carbonation was carried out for 4 weeks in an environment of 30°C, 60% relative humidity, and 5% carbon dioxide. After accelerated carbonation, a 1% alcohol solution of phenolphthalein was applied to the concrete cross section to check the carbonation depth. Compressive strength after carbonation: The compressive strength of specimens that were completely carbonized by accelerated carbonation was measured.

[0063] [Table 2]

[0064] Experimental Example 3 Mortar was prepared in the same manner as in Experimental Example 2, except that the amount of hardening agent 2 used was changed as shown in Table 3, and the compressive strength, carbonation depth, and compressive strength after carbonation were evaluated. The results are shown in Table 3.

[0065] [Table 3]

[0066] Experimental Example 4 The resistance to material (moisture) movement was evaluated depending on whether or not the concrete containing the rapid hardening admixture was neutralized. Note that the test specimens used were completely neutralized.

[0067] Using the rapid-hardening admixtures shown in Table 4, 50 parts of the rapid-hardening admixture were used in 100 parts of a cement composition consisting of normal cement and the rapid-hardening admixture, and cylindrical mortar specimens measuring Φ100 x 50 mm were prepared in accordance with JIS R 5201. The sides of the specimens were sealed with aluminum tape, and the top and bottom were left open. The specimens were immersed in a water bath up to 1 cm below the bottom, and split after 1, 2, and 3 hours of immersion. The depth of water penetration was measured using a vernier caliper. The results are shown in Table 4.

[0068] [Table 4]

[0069] The results in Table 1 show that the rapid hardening mineral admixture of the present invention has a high carbonation reaction rate and a high production amount of vaterite. Furthermore, from the results in Table 2, it can be seen that the mortar prepared using these rapid-hardening admixtures of the present invention has high compressive strength and a small depth of carbonation. In other words, it can be seen that the use of the rapid-hardening admixture of the present invention exhibits strength development in a short period of time and good carbonation resistance. Furthermore, it can be seen that the compressive strength after carbonation is also good. In contrast, the cement admixtures (rapid hardening materials 13 to 15) presented as comparative examples have low compressive strength and deep carbonation depth. Furthermore, the results in Table 4 show that the use of the cement admixture and cement composition of the present invention provides the effects of excellent early strength development and mass transfer resistance of concrete. [Industrial Applicability]

[0070] The rapid-hardening admixture and cement composition of the present invention can achieve short-term strength development and inhibit the penetration of deterioration factors such as carbon dioxide, thereby providing good carbonation resistance. The rapid-hardening admixture and cement composition of the present invention, which have such properties, are suitable for use as concrete materials in civil engineering or construction.

Claims

1. γ-2CaO.SiO ２ , 3CaO・2SiO ２ , α-CaO.SiO ２ and calcium magnesium silicate, wherein the non-hydraulic compound contains Li, and the Li content is 0.001 to 1.0 mass% in terms of oxide. The rapid-hardening admixture contains calcium aluminates and gypsums, and the non-hydraulic compound is 10 to 80 parts by mass, the calcium aluminates are 10 to 45 parts by mass, and the gypsums are 5 to 45 parts by mass relative to 100 parts by mass of the total amount of the non-hydraulic compound, the calcium aluminates, and the gypsums.

2. The chemical composition of the cement admixture in 100 parts by mass is Li ２ O 0.001 to 1.0 part by mass, CaO 45 to 70 parts by mass, SiO ２ 29 to 54 parts by mass of Al ２ O ３ The rapid hardening admixture according to claim 1, comprising 0 to 10 parts by mass of ２ The presence of O can be confirmed by ICP emission spectroscopy, but Li ２ Li 2 O does not include Li compounds that are physically mixed with non-hydraulic compounds.

3. 3. The rapid hardening admixture according to claim 1 or 2, further comprising a hardening regulator, the hardening regulator being one or more selected from the group consisting of inorganic carbonates, organic acids and salts of said organic acids.

4. A rapid-hardening cement composition comprising cement and the rapid-hardening admixture according to any one of claims 1 to 3.

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