Cement composition

Abstract

To provide a cement admixture capable of causing cement to develop excellent strength in an early stage.SOLUTION: The cement admixture contains gypsum whose dissolving rate into a saturated calcium hydroxide solution at 20°C is 30 mg / (100 mL-min) or more and 100 mg / (100 mL-min) or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cement admixture. [Background technology]

[0002] Patent Document 1 (JP 54-157129 A) describes a technique related to a cement admixture containing gypsum. This document describes a method for producing a cement hardening agent in which a cement hardening agent made of calcium aluminate and gypsum is mixed with a small amount of water in the presence of sulfuric acid, and claims that this method makes it easy to adjust the working life of the cement and enables the production of a cement hardening agent that is excellent in strength development. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 54-157129 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of the inventors' investigation into the cement quick-hardening admixture described in Patent Document 1, it was found that there is still room for improvement in terms of quickly developing excellent strength. [Means for solving the problem]

[0005] According to the present invention, the following cement admixture is provided.

[0006] 1. A cement admixture containing gypsum, A cement admixture, wherein the dissolution rate of the gypsum, measured according to the following Method 1, is 30 mg / (100 mL·min) or more and 100 mg / (100 mL·min) or less. (Method 1) (1) Place 100 mL of saturated calcium hydroxide solution, adjusted to 20°C, into a 200 mL beaker. (2) A stirring bar is placed in the beaker and stirred on a magnetic stirrer, and 4 g of the gypsum sample is added, and the elapsed time from the addition is measured. (3) After a specified time has elapsed since the addition, the beaker is immediately removed from the stirrer and subjected to suction filtration using JIS P 3801 No. 5C filter paper. (4) 10 mL of the filtrate was placed in a 20 mL measuring flask, and 1 mL of 3.18% hydrochloric acid solution was added, followed by dilution with pure water. (5) 5 mL of the solution obtained in (4) is taken into a 200 mL volumetric flask and made up to the volume with pure water. (6) The solution obtained in (5) was injected into an ion chromatograph (Shimadzu Corporation, Ion Chromatograph, PIA-1000, Personal Ion Analyzer) and SO4 2- Quantify the ions. (7) In the case where the specified time in (3) is 5 minutes or 10 minutes, perform SO4 in the steps (4) to (6) respectively. 2- The ions are quantified and the dissolution rate is calculated based on the following formula. Dissolution rate (mg / (100 mL min)) = (SO4 after 10 min 2- Ion concentration - SO4 after 5 minutes 2- ion concentration) / 5 2. The gypsum is granular; 2. The cement admixture according to 1., wherein the proportion of particles having a size of 1.0 μm or more and 10 μm or less in the gypsum is 30% by volume or more and 80% by volume or less. 3. The gypsum is granular; The median diameter d of the gypsum 50 3. The cement admixture according to 1. or 2., wherein the particle size is 5 μm or more and 15 μm or less. 4. A cement admixture according to any one of 1. to 3., further containing SiO2. [Effects of the Invention]

[0007] According to the present invention, it is possible to obtain a cement admixture that quickly develops excellent strength. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described. Unless otherwise specified, the symbol "to" in a numerical range indicates a range from above to below, and both ends of the range are included. In addition, in this embodiment, the composition may contain each component alone or in combination of two or more types.

[0009] (Cement admixture) In this embodiment, the cement admixture contains gypsum, and the dissolution rate of the gypsum measured by the following method 1 is 30 mg / (100 mL·min) or more and 100 mg / (100 mL·min) or less.

[0010] (Method 1) (1) Place 100 mL of saturated calcium hydroxide solution, adjusted to 20°C, into a 200 mL beaker. (2) Place a stirring bar in the beaker and stir on a magnetic stirrer. Add 4 g of gypsum sample and measure the elapsed time from the time of addition. (3) After the specified time has elapsed since the addition, immediately remove the beaker from the stirrer and filter by suction using JIS P 3801 No. 5C filter paper. (4) Transfer 10 mL of the filtrate to a 20 mL volumetric flask, add 1 mL of 3.18% hydrochloric acid solution, and make up to the volume with pure water. Here, 3.18% hydrochloric acid can be obtained, for example, by diluting commercially available 35% hydrochloric acid 1 / 11 times. (5) 5 mL of the solution obtained in (4) is taken into a 200 mL volumetric flask and made up to the volume with pure water. (6) The solution obtained in (5) was injected into an ion chromatograph (Shimadzu Corporation, Ion Chromatograph, PIA-1000, Personal Ion Analyzer) and SO4 2- Quantify the ions. (7) In the case where the specified time in (3) is 5 minutes or 10 minutes, perform SO4 in the steps (4) to (6) respectively. 2- The ions are quantified and the dissolution rate is calculated based on the following formula. Dissolution rate (mg / (100 mL min)) = (SO4 after 10 min 2- Ion concentration - SO4 after 5 minutes 2-ion concentration) / 5

[0011] The present inventors have found that excellent strength can be developed early by setting the dissolution rate of gypsum contained in a cement admixture in a saturated calcium hydroxide solution at 20° C. within a specific range. The reason for this is not entirely clear, but it is thought to be because the admixture has adequate handleability and reaction activity suitable for early strength development.

[0012] From the viewpoint of improving the strength of the cement composition, the dissolution rate of gypsum is 30 mg / (100 mL min) or more, preferably 50 mg / (100 mL min) or more, more preferably 60 mg / (100 mL min) or more, and even more preferably 70 mg / (100 mL min) or more. From the viewpoint of improving the reactivity and handling time of the cement composition, the dissolution rate of gypsum is 100 mg / (100 mL min) or less, preferably 95 mg / (100 mL min) or less, more preferably 90 mg / (100 mL min) or less, even more preferably 85 mg / (100 mL min) or less, and still more preferably 80 mg / (100 mL min) or less.

[0013] The type of gypsum is not limited, and may be, for example, one or more selected from anhydrous gypsum (CaSO4) and gypsum hemihydrate. From the viewpoint of improving the strength of the cement composition, the gypsum preferably contains anhydrous gypsum, and more preferably is anhydrous gypsum. Examples of anhydrous gypsum include anhydrous gypsum produced by hydrofluoric acid and natural anhydrous gypsum. From the viewpoint of improving the strength of the cement composition, anhydrous gypsum produced by hydrofluoric acid is preferred.

[0014] The shape of the gypsum is not limited, but is preferably granular from the viewpoint of stably improving the strength of the cement composition. In this case, from the viewpoint of improving the strength of the cement composition, the proportion of particles in the gypsum having a particle size in the range of 1.0 μm or more and 10 μm or more is preferably 30 vol% or more, more preferably 40 vol% or more, and even more preferably 50 vol% or more, of the total gypsum, and is preferably 80 vol% or less, and more preferably 70 vol% or less.

[0015] Also, the median diameter of gypsum, d 50 From the viewpoint of improving the strength of the cement composition, the particle size is preferably 5 μm or more, more preferably 6 μm or more, and is preferably 15 μm or less, more preferably 12 μm or less, even more preferably 10 μm or less, and even more preferably 8 μm or less.

[0016] Here, the particle size distribution of the gypsum can be obtained by measuring the particle size distribution of the particles on a volume basis using a commercially available laser diffraction particle size distribution measuring device (for example, LA-960 manufactured by HORIBA Corporation).

[0017] From the viewpoint of improving the strength of the cement composition, the content of gypsum in the cement admixture is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and still more preferably 98% by mass or more, based on the total mass of the cement admixture. There is no upper limit to the amount of gypsum contained in the cement admixture, and it is 100% by mass or less, but it may be, for example, 99% by mass or less, or may be, for example, 98% by mass or less.

[0018] The cement admixture may be composed of gypsum or may contain components other than gypsum. For example, the cement admixture may further contain SiO2 (silica) from the viewpoint of improving the handling properties of the cement composition. When the cement admixture contains SiO2, the shape of the silica is, for example, granular. Also, the median diameter d 50 is, for example, the median diameter d of the gypsum mentioned above. 50 It can be made to the same extent as Moreover, from the viewpoint of improving the strength of the cement composition, it is preferable that the cement admixture does not contain fluorite (CaF2).

[0019] Next, a method for producing the cement admixture will be described. The method for producing a cement admixture may include, for example, preparing gypsum having a solubility within a specific range. When the cement admixture contains a component other than gypsum, the method may also include mixing the gypsum with the component other than gypsum. In this embodiment, the dissolution rate of gypsum can be controlled by, for example, appropriately selecting a gypsum preparation method, etc. Among these, appropriately adjusting the particle size, particle size distribution, etc. of gypsum can be cited as a factor for achieving a desired dissolution rate of gypsum. The particle size and particle size distribution of the cement admixture can be adjusted by performing a pulverization and classification process. There are no limitations on the pulverization and classification methods, and known pulverization and classification methods can be used. For example, a ball mill or roller mill can be used as the pulverization method, and an air classifier can be used as the classification method.

[0020] (Cement composition) In this embodiment, the cement composition includes the cement admixture in this embodiment and cement. In this embodiment, since the cement composition contains the above-mentioned cement admixture, excellent strength can be developed early. Furthermore, according to this embodiment, for example, it is possible to stably control the usable life of the cement composition, for example, to stably extend it.

[0021] The term "cement" in this embodiment is not limited to, but includes, for example, various types of Portland cement defined by the Japanese Industrial Standards (JIS), including normal, early-strength, moderate-heat, and low-heat cements; various types of blended cements containing blast furnace slag, fly ash, and silica; filler cements containing limestone powder and slowly cooled blast furnace slag powder; and environmentally friendly cements (ecocements) manufactured using municipal waste incineration ash and sewage sludge incineration ash as raw materials. Also included are cements defined by the overseas EN197-2000 standard and all types of cement defined by the Chinese GB standard, and one or more of these can be used.

[0022] The cement composition more specifically contains water. The amount of water used is not limited, but the water / cement composition ratio may usually be, for example, about 8 to 80%, or may be, for example, 25 to 70%, or may be, for example, 30 to 60%, relative to the cement composition.

[0023] The cement composition is specifically a rapid hardening cement, and in this case, for example, the cement admixture in this embodiment may be a rapid hardening agent. Here, the rapid hardening agent refers to a component that quickly generates a rapid hardening hydrate such as ettringite and imparts rapid hardening to cement concrete. When the cement admixture is a hardening agent, the hardening agent preferably contains at least the above-mentioned gypsum and calcium aluminate. Regarding the content of these components in the hardening agent, when the hardening agent contained in the hardening cement is taken as 100 parts by mass, the total amount of calcium aluminate and gypsum is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, and can be 100 parts by mass. In other words, the hardening agent according to this embodiment can be composed only of calcium aluminate and gypsum.

[0024] (Calcium Aluminate) Calcium aluminate is a mineral that can be obtained by synthesizing, for example, CaO raw material, Al2O3 raw material, and optionally SiO2 raw material in an electric furnace or kiln at 1,200 to 1,900°C, followed by rapid cooling. The calcium aluminate may have a composition of, for example, 35 to 60 mass % CaO, 35 to 55 mass % Al2O3, and 1 to 15 mass % SiO2. Exemplary chemicals include 3CaO·Al2O3, 12CaO·7Al2O3, 11CaO·7Al2O3·CaF2, CaO·Al2O3, 2CaO·Al2O3·SiO2, CaO·Al2O3·2SiO2, 3CaO·3Al2O3·CaF2, 3CaO·2Na2O·5Al2O3, etc., and may contain one or more of the above. Of these, 12CaO·7Al2O3 is preferred. The amount of calcium aluminate in the rapid hardening cement is, for example, 2 parts by mass or more and preferably 30 parts by mass or less, and for example, 5 parts by mass or more and 20 parts by mass or less, based on 100 parts by mass of the rapid hardening cement. By setting the amount of calcium aluminate within the above range, a rapid hardening cement with an excellent balance between short-term strength and expansion rate after curing can be obtained. Calcium aluminate can be used in either crystalline or vitreous form, but vitreous form obtained by quenching the melt in an electric furnace or the like is preferred, and when the vitreous content is 60 mass% or more, it is excellent in short-term strength development. The fineness of calcium aluminate is 3,000 cm in Blaine value. 2 / g or more 9,000cm 2 / g or less, and 2 / g or more 7,000cm 2 It is more preferable that the saturation coefficient is 1 / g or less.

[0025] The cement composition may contain components other than those described above. Specific examples of such components include one or more materials selected from the group consisting of set retarders, water-reducing agents, high-performance water-reducing agents, air entraining (AE) agents, air-entraining water-reducing agents, high-performance air-entraining water-reducing agents, thickeners, rust inhibitors, antifreeze agents, hydration heat inhibitors, polymer emulsions, clay minerals such as bentonite and montmorillonite, ion exchangers such as zeolites, hydrotalcites, and hydrocalumite, sulfates such as aluminum sulfate and sodium sulfate, phosphates, and boric acid.

[0026] In the cement composition, the materials may be mixed at the time of application, or some or all of them may be mixed in advance.

[0027] The method for mixing the cement composition is not limited and may be a commonly used method. Any existing mixing device can be used as the mixing device, such as a tilting mixer, an omni mixer, a V-type mixer, a Henschel mixer, or a Nauta mixer.

[0028] Furthermore, the method of curing the cement composition is not limited, and any of the commonly used curing methods such as room temperature and pressure curing, steam curing, high temperature and pressure steam curing, and pressurized curing can be applied.

[0029] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0030] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples. Unless otherwise specified, all operations were carried out at room temperature and pressure.

[0031] (Raw materials used) plaster Used in each example plaster is as follows: plaster 1: Type II anhydrite, pH 3.3, main component CaSO4 plaster 2: Type II anhydrite, pH 6.0, main component CaSO4 plaster 3: Type II natural anhydrite, pH 8.5, main component CaSO4

[0032] Example 1 plaster 1 was crushed in a ball mill. The properties of gypsum 1 after pulverization are shown in Table 1.

[0033] (Example 2, Comparative Example 1) Each is listed in Table 1 plaster The same as in Example 1 except that did. The obtained results of each example and comparative example plaster The following evaluation was carried out.

[0034] Here, each plaster The analysis was carried out using the following method. The analysis results are shown in Table 1. (component analysis) The chemical composition was analyzed in accordance with JIS R 5202 "Methods for chemical analysis of Portland cement." (pH) Each product conforms to JIS R 9101 (method of chemical analysis of gypsum) plaster The pH was measured.

[0035] (dissolution rate) (1) 100 mL of saturated calcium hydroxide solution adjusted to 20°C was placed in a 200 mL beaker. (2) Place a stirring bar in the beaker and stir on a magnetic stirrer. plaster 4g of the sample was added and the time elapsed from the time of addition was measured. (3) After the specified time had elapsed since the addition, the beaker was immediately removed from the stirrer and subjected to suction filtration using JIS P 3801 No. 5C filter paper. (4) 10 mL of the filtrate was placed in a 20 mL volumetric flask, and 1 mL of 3.18% hydrochloric acid solution was added, followed by dilution with pure water. (5) 5 mL of the solution obtained in (4) was placed in a 200 mL volumetric flask and made up to the desired volume with pure water. (6) The solution obtained in (5) was injected into an ion chromatograph (Shimadzu Corporation, Ion Chromatograph, PIA-1000, Personal Ion Analyzer) and SO4 2- The ions were quantified. (7) In the case where the specified time in (3) is 5 minutes or 10 minutes, perform SO4 in the steps (4) to (6) respectively. 2- The ions were quantified and the dissolution rate was calculated based on the following formula. Dissolution rate (mg / (100 mL min)) = (SO4 after 10 min 2- Ion concentration - SO4 after 5 minutes 2- ion concentration) / 5

[0036] (particle size distribution) The particle size distribution of the particles was measured on a volume basis using a laser diffraction particle size distribution analyzer (HORIBA, LA-960).

[0037] (Preparation of mortar) 270 g of cement admixture (rapid hardening material) (containing 135 g of gypsum and 135 g of calcium aluminate for each example and comparative example) 630g of cement, 1350g of fine aggregate, and 306g of water were mixed at room temperature (20℃) to prepare mortar, and the compressive strength was measured.

[0038] (Materials used) calcium aluminate : CaO-Al2O3-SiO2 amorphous material CaO 47%, Al2O3 47%, SiO2 3%, others 3%. Density 2.85g / cm 3 , Blaine specific surface area 5000cm 2 / g, amorphousness 90% Cement: Denka high-early-strength Portland cement (Blaine specific surface area 4500 cm 2 / g, density 3.12g / cm 3 ) Fine aggregate: River sand from Himekawa, Itoigawa City, Niigata Prefecture, surface-dried, density 2.62 g / cm 3, Maximum aggregate size 5mm Water: Tap water

[0039] ( calcium aluminate , cement density and Blaine specific surface area) Each of the above calcium aluminate The density and Blaine specific surface area of ​​the cement were measured based on JIS R5201 (physical testing method for cement).

[0040] <Compression strength> Based on JIS R 5201, 4x4x16cm test specimens were prepared and the compressive strength was measured after 3 hours.

[0041] [Table 1]

[0042] As can be seen from Table 1, in each example, the cement composition had excellent strength and was able to develop high strength as early as 3 hours.

Claims

1. A cement composition comprising a cement admixture and cement, The cement composition is a rapid hardening cement, The cement admixture is a hardening agent, and the hardening agent is composed only of calcium aluminate and gypsum. The content of the gypsum in the rapid hardening material is 50% by mass or more and 98% by mass or less, The amount of calcium aluminate in the rapid hardening cement is 2 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass of the rapid hardening cement, The dissolution rate of the gypsum, measured according to the following method 1, is 30 mg / (100 mL min) or more and 100 mg / (100 mL min) or less, The calcium aluminate has a composition of 35% by mass or more and 60% by mass or less of CaO, Al ２ O ３ is 35% by mass or more and 55% by mass or less, SiO ２ The cement composition, wherein the content is 1% by mass or more and 15% by mass or less. (Method 1) (1) Place 100 mL of saturated aqueous calcium hydroxide solution adjusted to 20°C into a 200 mL beaker. (2) A stirring bar is placed in the beaker and stirred on a magnetic stirrer, and 4 g of the gypsum sample is added, and the elapsed time from the addition is measured. (3) Immediately after a specified time has elapsed since the addition, the beaker is removed from the stirrer and the mixture is subjected to suction filtration using JIS P 3801 No. 5C filter paper. (4) 10 mL of the filtrate is placed in a 20 mL volumetric flask, and 1 mL of 3.18% hydrochloric acid aqueous solution is added, followed by diluting the solution with purified water. (5) 5 mL of the solution obtained in (4) is placed in a 200 mL volumetric flask and made up to the volume with pure water. (6) The solution obtained in (5) was injected into an ion chromatograph (Shimadzu Corporation, ion chromatograph, PIA-1000, personal ion analyzer), and SO 4 2- Quantify the ions. (7) In the case where the specified time in (3) is 5 minutes or 10 minutes, the SO is performed in the steps (4) to (6) respectively. 4 2- The ions are quantified and the dissolution rate is calculated based on the following formula. Dissolution rate (mg / (100 mL min)) = (SO after 10 minutes) 4 2- Ion concentration - SO after 5 minutes 4 2- ion concentration) / 5

2. the gypsum is granular, 2. The cement composition according to claim 1, wherein the proportion of particles having a size of 1.0 μm or more and 10 μm or less in the gypsum is 30% by volume or more and 80% by volume or less.

3. the gypsum is granular, The median diameter d of the gypsum 50 The cement composition according to claim 1 or 2, wherein the particle size is 5 μm or more and 15 μm or less.

4. The cement admixture is SiO ２ The cement composition of claim 1 , further comprising:

Images