Cement admixtures, cement compositions, hardened cement products

Abstract

The object of the present invention is to provide a cement admixture that is excellent in storage stability, usable life, and strength development. [Solution] A cement admixture containing alkali metal carbonate and / or alkaline earth metal carbonate, which has a mass increase rate of 75% or less after 3 days under conditions of a temperature of 40°C and a humidity of 90% RH.

Description

[Technical Field]

[0001] The present invention relates to a cement admixture, a cement composition, and a hardened cement product. [Background technology]

[0002] Hydraulic materials such as cement used in civil engineering and construction fields are usually mixed with water and allowed to harden by standing for a predetermined period of time. The hardening speed and other properties of hydraulic materials can be affected by the ratio of the material to water, the ambient temperature, the curing method, etc., but cement admixtures are often used to improve various properties.

[0003] The key to improving the workability of hydraulic materials on site, that is, to comprehensively streamline the workability by increasing the work speed, unifying the materials into one material, and improving the ease of handling, is, for example, to increase the hardening speed of hydraulic compositions and to premix hydraulic materials by mixing them with cement admixtures in advance, and in fact, various materials and compositions with a fast setting speed and high strength development have been proposed (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-12350 [Patent Document 2] Japanese Patent Application Publication No. 1-230455 [Patent Document 3] Japanese Patent Application Publication No. 11-139859 Summary of the Invention [Problem to be solved by the invention]

[0005] However, alkali carbonates and hydroxycarboxylic acids, which are commonly used as cement admixtures, are prone to hygroscopicity and are susceptible to deterioration depending on the storage conditions of the materials, so quality fluctuations when used as cement admixtures have been an issue.

[0006] In view of the above, an object of the present invention is to provide a cement admixture that is excellent in storage stability, usable life, and strength development. [Means for solving the problem]

[0007] As a result of intensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a cement admixture containing an alkali metal carbonate and an alkaline earth metal carbonate, and having a mass gain rate measured under specific conditions within a predetermined range, and have thus completed the present invention.

[0008] [1] A cement admixture containing alkali metal carbonate and / or alkaline earth metal carbonate, which exhibits a mass increase of 75% or less after 3 days under conditions of a temperature of 40°C and a humidity of 90% RH. [2] The cement admixture according to [1] above, containing the alkali metal carbonate as a double salt. [3] The cement admixture according to [2] above, wherein the double salt contains an alkali metal and an alkaline earth metal. [4] The cement admixture according to [1] above, containing the alkaline earth metal carbonate as a double salt. [5] The cement admixture according to [4] above, wherein the double salt contains an alkali metal and an alkaline earth metal. [6] The cement admixture according to any one of the above [1] to [5], wherein the alkali metal carbonate and the alkaline earth metal carbonate are contained as a double salt of the alkali metal carbonate and the alkaline earth metal carbonate. [7] The cement admixture according to any one of the above [1] to [6], wherein the alkali metal carbonate contains one or more alkali metals selected from the group consisting of lithium, sodium, and potassium. [8] The cement admixture according to any one of the above [1] to [7], wherein the alkaline earth metal carbonate contains magnesium and / or calcium. [9] The cement admixture according to any one of the above [1] to [8], wherein the total content of the alkali metal carbonate and the alkaline earth metal carbonate is 20 to 80 mass %.

[10] The cement admixture according to any one of the above [1] to [9], which contains hydroxycarboxylic acids.

[11] The cement admixture according to

[10] above, wherein the hydroxycarboxylic acids include one or more hydroxycarboxylic acids and / or hydroxycarboxylic acid salts selected from the group consisting of citric acid, gluconic acid, tartaric acid, and malic acid.

[12] The cement admixture according to the above

[10] or

[11] , wherein the content of the hydroxycarboxylic acids is 20 to 80 mass %.

[13] A cement composition containing the cement admixture according to any one of [1] to

[12] above.

[14] A hardened cement product containing the hardened cement composition according to

[13] above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a cement admixture that is excellent in storage stability, usable life, and strength development. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention (the present embodiment) will be described in detail, but the present invention is not limited to this embodiment. In this specification, "%" is based on mass unless otherwise specified.

[0011] [Cement admixtures] The cement admixture according to this embodiment contains an alkali metal carbonate and / or an alkaline earth metal carbonate, and exhibits a mass gain of 75% or less after 3 days at a temperature of 40°C and a humidity of 90% RH (hereinafter, sometimes simply referred to as "mass gain"). The mass gain can be calculated by measuring the mass gain after leaving the cement admixture for 3 days at a temperature of 40°C and a humidity of 90% RH and dividing the measured mass by the mass of the cement admixture before leaving it. However, the temperature and humidity allow for errors of ±5°C and ±5%, respectively. The mass gain can be adjusted by adjusting the blending ratio of the raw materials of the cement admixture. If the mass gain exceeds 75%, the cement admixture of the present invention may not have excellent storage stability, usable life, and strength development.

[0012] The mass increase rate of the cement admixture of the present invention is preferably 60% or less, more preferably 45% or less, and even more preferably 30% or less. When the mass increase rate of the cement admixture is within the above range, it is easy to obtain excellent storage stability and usable life.

[0013] The cement admixture according to this embodiment contains an alkali metal carbonate and / or an alkaline earth metal carbonate. The carbonate contains carbonate ions (CO 2- ) and bicarbonate ion (HCO3 - ) and may be contained as a simple salt or a double salt. Note that a simple salt is composed of a single salt, and in the present invention, it is composed of an alkali metal or alkaline earth metal and a carbonate ion or a bicarbonate ion. A double salt is a salt composed of two or more simple salts and containing at least two or more cations or two or more anions, and in the present invention, it contains at least an alkali metal or alkaline earth metal and a carbonate ion or a bicarbonate ion. If the cement admixture does not contain an alkali metal carbonate and an alkaline earth metal carbonate, it may not be possible to achieve excellent storage stability and usable life.

[0014] The cement admixture according to this embodiment preferably contains an alkali metal carbonate as the double salt. That is, it preferably contains a double salt containing a salt formed of an alkali metal and a carbonate ion or a bicarbonate ion. It is more preferable that the double salt contains an alkali metal and an alkaline earth metal. When the cement admixture contains an alkali metal carbonate as the double salt, it is easy to improve the storage stability and usable life, and when the double salt contains an alkali metal and an alkaline earth metal, it is possible to improve the storage stability, usable life, and early strength development.

[0015] The cement admixture according to the present embodiment preferably contains an alkaline earth metal carbonate as the double salt. That is, it preferably contains a double salt containing a salt formed of an alkaline earth metal and a carbonate ion or a bicarbonate ion. It is more preferable that the double salt contains an alkali metal and an alkaline earth metal.

[0016] The cement admixture according to this embodiment preferably contains the alkali metal carbonate and the alkaline earth metal carbonate as a double salt of the alkali metal carbonate and the alkaline earth metal carbonate. By containing the alkali metal carbonate and the alkaline earth metal carbonate as a double salt of the alkali metal carbonate and the alkaline earth metal carbonate, the cement admixture can have better storage stability, usable life, and early strength development.

[0017] From the viewpoint of pot life and early strength development, the alkali metal carbonate in the cement admixture according to the present embodiment preferably contains one or more alkali metals selected from the group consisting of lithium, sodium, and potassium, more preferably contains sodium and / or potassium, and even more preferably contains potassium.

[0018] From the viewpoint of cost, the alkaline earth metal carbonate in the cement admixture according to this embodiment preferably contains magnesium and / or calcium, and more preferably contains calcium.

[0019] In the cement admixture according to this embodiment, the total content of alkali metal carbonate and alkaline earth metal carbonate is preferably 1 to 100 mass%, more preferably 3 to 75 mass%, and even more preferably 5 to 60 mass%. When the cement admixture contains alkali metal carbonate and / or alkaline earth metal carbonate as a double salt, the content of each single salt in the double salt is calculated first. When the total content of alkali metal carbonate and alkaline earth metal carbonate is within the above range, it is easy to improve storage stability and usable life.

[0020] The cement admixture according to this embodiment preferably contains an oxycarboxylic acid. The oxycarboxylic acid in the present invention refers to a compound containing at least one carboxy group (-COOH) and one hydroxy group (-OH) in one molecule, and a salt thereof. The inclusion of an oxycarboxylic acid in the cement admixture of the present invention makes it easier to improve storage stability and usable life.

[0021] From the viewpoints of storage stability, usable life, and strength development, the hydroxycarboxylic acids preferably contain one or more hydroxycarboxylic acids and / or hydroxycarboxylic acid salts selected from the group consisting of citric acid, gluconic acid, tartaric acid, and malic acid, more preferably one or more selected from the group consisting of citric acid, gluconic acid, potassium citrate, sodium citrate, potassium gluconate, and sodium gluconate, and even more preferably citric acid and / or sodium gluconate. Furthermore, from the viewpoint of storage stability, it is even more preferable to contain sodium gluconate, and from the viewpoint of usable life, it is even more preferable to contain citric acid.

[0022] The cement admixture according to this embodiment preferably contains 80% by mass or less of hydroxycarboxylic acids, more preferably 30 to 70% by mass, and even more preferably 35 to 65% by mass. When the hydroxycarboxylic acids contain two or more types of hydroxycarboxylic acids and / or hydroxycarboxylic acid salts, the total amount is taken as the content of hydroxycarboxylic acids. When the content of hydroxycarboxylic acids in the cement admixture is within the above range, it is easy to achieve better storage stability, usable life, and strength development.

[0023] The cement admixture of the present invention preferably has an alkali metal content, calculated as oxide, of 20 to 70 mass %, more preferably 25 to 65 mass %, and even more preferably 30 to 60 mass %.

[0024] In the cement admixture of the present invention, the mass ratio of the content of hydroxycarboxylic acids to the total content of alkali metal carbonate and alkaline earth metal carbonate is preferably 0.1 to 1.0, more preferably 0.2 to 1.0, and even more preferably 0.3 to 0.8.

[0025] [Cement composition] The cement composition according to this embodiment contains the cement admixture of the present invention. The cement composition containing the cement admixture of the present invention has excellent storage stability and usable life.

[0026] The cement composition of the present invention essentially contains a cement material. The cement material may include conventional cement. Examples of cement include various types of Portland cement, such as normal, high-early-strength, ultra-high-early-strength, low-heat, and moderate-heat cements; various blended cements obtained by mixing these Portland cements with blast furnace slag, fly ash, silica, silica fume, metakaolin, allophane, and the like; environmentally friendly cements (ecocements) produced using municipal waste incineration ash and sewage sludge incineration ash as raw materials; commercially available fine cements; white cements; and filler cements containing limestone fine powder. These cements can also be used in their finely powdered form. Other examples include geopolymer cements, sulfoaluminate cements, limestone-calcined clay cements (LC3), and carbonated cements that harden by immobilizing CO2, which emit less CO2 than conventional cements. Furthermore, cements containing components (e.g., gypsum) typically used in conventional cements can also be used. Furthermore, combinations of two or more of these cements can also be used.

[0027] From the viewpoint of manufacturing cost and strength development, cement is required to have a Blaine specific surface area (Blaine value) of 2,000 to 6,000 cm 2 / g, and 3,000 to 5,000 cm 2 / g is more preferable. By having the Blaine value within the above range, strength development and handleability can be excellent. In the present invention, the Blaine specific surface area can be measured based on the specific surface area test specified in JIS R 5201:2015 "Physical Testing Methods for Cement."

[0028] The cement material preferably contains calcium aluminate. Calcium aluminate is a general term for compounds that contain CaO and Al2O3 as main components and have hydration activity, such as compounds in which part of the CaO and / or Al2O3 is replaced with an alkali metal oxide, alkaline earth metal oxide, silicon oxide, titanium oxide, iron oxide, alkali metal halide, alkaline earth metal halide, alkali metal sulfate, or alkaline earth metal sulfate, or a substance in which a small amount of these elements are dissolved in a substance primarily containing CaO and Al2O3. Calcium aluminate may be either crystalline or amorphous.

[0029] Specific examples of crystalline materials include C3A and C, where CaO is C, Al2O3 is A, and R2O (Na2O, K2O, Li2O) is R. 14 RA5, CA, C 12 A7 and C 11 Examples include A7·CaF2, C4A·Fe2O3, and C3A3·CaSO4, but amorphous calcium aluminate is preferred due to its rapid setting properties. In addition, in the case of amorphous calcium aluminate, it is preferable that the vitrification rate is 80% or more.

[0030] From the viewpoints of strength development and rapid setting, the CaO / Al2O3 molar ratio of calcium aluminate is preferably 1.7 to 2.9, more preferably 1.8 to 2.8, and even more preferably 1.9 to 2.7. In the present invention, the CaO / Al2O3 molar ratio of calcium aluminate can be determined, for example, by fluorescent X-ray analysis.

[0031] Calcium aluminate can be obtained by heat treating a CaO raw material such as calcium carbonate or calcium hydroxide with an Al2O3 raw material such as bauxite in a rotary kiln, electric furnace, or the like. Specifically, the raw materials are mixed in a predetermined ratio, heated and melted in an electric furnace, and then quenched by contact with compressed air or water. The CaO / Al2O3 molar ratio can be adjusted by adjusting the ratio of the raw materials, and the vitrification rate can be adjusted by changing the temperature during heating and melting and the cooling method.

[0032] When calcium aluminate is obtained industrially, it may contain impurities. Specific examples include SiO2, Fe2O3, MgO, TiO2, MnO, Na2O, KO, Li2O, S, PO5, and F. However, the presence of these impurities is not particularly problematic as long as they do not substantially impair the objectives of the present invention. Specifically, there is no particular problem when the total amount of these impurities is 10% or less.

[0033] The Blaine value of calcium aluminate is 4,000 to 7,000 cm 2 / g, and 4,500 to 6,800 cm 2 When the Blaine value is within the above range, the handling property can be improved.

[0034] The content of calcium aluminate in the cement material is preferably 5 to 50 mass %, more preferably 10 to 45 mass %. When the content of calcium aluminate is within the above range, it is easy to achieve better strength development and quick setting properties.

[0035] The cement material preferably contains gypsum. From the viewpoints of pot life and strength development, the gypsum preferably contains one or more types selected from the group consisting of gypsum anhydride, gypsum hemihydrate, and gypsum dihydrate.

[0036] The Blaine value of gypsum is 4,000 to 7,000 cm 2 / g, and 4,500 to 6,800 cm 2 When the Blaine value is within the above range, the strength development can be improved.

[0037] The content of gypsum in the cement material is preferably 10 to 50 mass %, more preferably 20 to 40 mass %. When the content of gypsum is within the above range, it is easy to achieve better strength development.

[0038] The cement composition of the present invention preferably contains 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, of the cement admixture relative to 100 parts by mass of the cement material. When the content of the cement admixture is within the above range, the storage stability and usable life can be improved.

[0039] The cement composition of the present invention can contain aggregate. The type of aggregate is not particularly limited, and examples of fine aggregate that can be used include river sand, mountain sand, sea sand, lime sand, and silica sand, and examples of coarse aggregate that can be used include river gravel, mountain gravel, and lime gravel, as well as crushed sand and crushed stone.

[0040] The content of the aggregate in the cement composition is preferably 80 to 300 parts by mass, and more preferably 100 to 250 parts by mass, per 100 parts by mass of the cement material in the cement composition.

[0041] The cement composition of the present invention may contain a water-reducing agent. The type of water-reducing agent is not particularly limited, and common water-reducing agents such as naphthalene-based water-reducing agents, polycarboxylic acid-based water-reducing agents, aminosulfonic acid-based water-reducing agents, melamine-based water-reducing agents, and lignin-based water-reducing agents can be used.

[0042] The content of the water reducing agent is preferably 0.05 to 2.0 parts by mass, more preferably 0.1 to 1.8 parts by mass, and even more preferably 0.15 to 1.0 parts by mass, in terms of solid content, per 100 parts by mass of the cement material in the cement composition.

[0043] The total content of the cement admixture, cement material, aggregate, and water-reducing agent in the cement composition of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

[0044] In addition to the materials mentioned above, the cement composition of the present invention can contain one or more admixtures such as ground granulated blast furnace slag, ground slowly cooled blast furnace slag, ground limestone, fly ash, and silica fume, as well as hardening accelerators, antifoaming agents, thickeners, rust inhibitors, antifreeze agents, shrinkage reducing agents, polymers, setting modifiers, clay minerals such as bentonite, and anion exchangers such as hydrotalcite, within a range that does not substantially impair the objects of the present invention.

[0045] [Hardened cement] The hardened cement product according to this embodiment contains a hardened product of the cement composition of the present invention. The hardened cement product can be obtained by kneading the cement composition with water and then hardening the mixture.

[0046] The content of the cement composition in the hardened cement product is preferably 80% by mass or more, more preferably 90% by mass or more, or may be 100% by mass. When the content of the cement composition is within the above range, the product can have excellent strength development and rapid hardening properties.

[0047] A hardened cement composition can be obtained by kneading the cement composition with water and then hardening the mixture. The amount of water is preferably 20 to 50 parts by mass, more preferably 25 to 45 parts by mass, and even more preferably 30 to 40 parts by mass, per 100 parts by mass of the cement material in the cement composition.

[0048] The method for mixing the cement composition and water is not particularly limited, and they may be mixed at the time of application, or some or all of the materials in the cement composition may be mixed in advance. Any existing mixer, such as a tilting mixer, omni mixer, Henschel mixer, V-type mixer, Plosser mixer, or Nauta mixer, can be used as the mixer. [Example]

[0049] The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention.

[0050] [Experimental Example 1] <Preparation of cement admixture> The materials listed below were mixed in the proportions shown in Table 1 to prepare cement admixtures. The mass of each cement admixture was measured, and then it was left to stand at a temperature of 40°C and a humidity of 90%RH. The mass increase after 3 days was divided by the mass of each material before standing to calculate the mass increase rate. The results are shown in Table 1.

[0051] <Raw materials used> Potassium carbonate: technical product, anhydrous. Potassium calcium carbonate: 100 g of potassium carbonate and 100 g of calcium carbonate were placed in a mortar and mixed for 5 minutes, and the mixture was placed in an alumina crucible and fired in an electric furnace at 750°C for 30 minutes, and then allowed to cool naturally. Citric acid: Reagent, anhydrous. Sodium gluconate: Industrial product.

[0052] [Table 1]

[0053] <Preparation of cement composition> Mortar was prepared by mixing 630 g of the cement shown below with 135 g of calcium aluminate, 135 g of gypsum, 1,350 g of aggregate, and 306 g of water. The cement admixtures were then stored for three days at a temperature of 40°C and a humidity of 90% RH. The cement compositions were prepared by mixing the cement admixtures before and after storage at the ratios shown in Table 2 relative to the cement materials (cement, calcium aluminate, and gypsum) in the mortar. The following tests were carried out on each of the prepared cement compositions in a 20°C environment. The results are shown in Table 2.

[0054] (Materials used) Cement: High-early-strength cement (Pacific Cement Co., Ltd.). Calcium aluminate: Amorphous calcium aluminate prepared by melting calcium carbonate and aluminum oxide in an electric furnace and rapidly cooling them to a CaO / Al2O3 molar ratio of 2.3. The vitrification rate is 97% (measured by powder X-ray diffraction) and the Blaine value is 5,500 cm 2 / g, amorphous. Gypsum: anhydrous gypsum, Blaine value 5,500 cm 2 / g. Aggregate: Standard sand (Japan Cement Association). Water: Tap water.

[0055] <Flow test> The flow value of the prepared mortar was measured in accordance with the method specified in JIS R 5201:2015 "Physical Testing Methods for Cement." Note that the flow value when using the cement admixture after storage is preferably 200 to 230 mm.

[0056] <Pot life> The usable time of the prepared mortar was measured as the time it took for the temperature to rise by 1.0°C from the as-mixed temperature. The time at which the mortar began to set (when the Proctor penetration resistance reached 3.5 N / mm) was also measured. 2 It was confirmed that the usable time of the cement admixture after storage was longer than the time required for the cement admixture to reach a temperature of 5 to 25 minutes.

[0057] <Compression strength test> The compressive strength of the prepared mortar at 3 hours was measured in accordance with the method specified in JIS R 5201:2015 "Physical Testing Methods for Cement." The compressive strength at 3 hours after storage was 24 N / mm 2 It is preferable that this is the case.

[0058] [Table 2] [Industrial Applicability]

[0059] The cement admixture of the present invention is excellent in storage stability, usable life and strength development, and can be suitably used for premix materials and the like.

Claims

1. A cement admixture containing an alkali metal carbonate and / or an alkaline earth metal carbonate, A cement admixture that exhibits a mass increase rate of 75% or less after 3 days under conditions of a temperature of 40°C and a humidity of 90% RH.

2. 2. The cement admixture of claim 1, containing said alkali metal carbonate as a double salt.

3. 3. The cement admixture of claim 2, wherein the double salt comprises an alkali metal and an alkaline earth metal.

4. 2. The cement admixture of claim 1, containing said alkaline earth metal carbonate as a double salt.

5. 5. The cement admixture of claim 4, wherein the double salt comprises an alkali metal and an alkaline earth metal.

6. The cement admixture according to any one of claims 1 to 5, wherein the alkali metal carbonate and the alkaline earth metal carbonate are contained as a double salt of an alkali metal carbonate and an alkaline earth metal carbonate.

7. The cement admixture according to any one of claims 1 to 5, wherein the alkali metal carbonate comprises one or more alkali metals selected from the group consisting of lithium, sodium, and potassium.

8. 6. The cement admixture according to claim 1, wherein the alkaline earth metal carbonate comprises magnesium and / or calcium.

9. The cement admixture according to any one of claims 1 to 5, wherein the total content of the alkali metal carbonate and the alkaline earth metal carbonate is 20 to 80 mass%.

10. The cement admixture according to any one of claims 1 to 5, which contains hydroxycarboxylic acids.

11. The cement admixture according to claim 10, wherein the hydroxycarboxylic acids include one or more hydroxycarboxylic acids and / or hydroxycarboxylic acid salts selected from the group consisting of citric acid, gluconic acid, tartaric acid, and malic acid.

12. The cement admixture according to claim 10, wherein the content of the oxycarboxylic acids is 20 to 80% by mass.

13. A cement composition comprising the cement admixture according to any one of claims 1 to 5.

14. A hardened cement product comprising the hardened cement composition according to claim 13.

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