Hydraulic composition

Abstract

To provide a hydraulic composition excellent in initial and long-term strength development even when blast furnace cement including blast furnace slag fine powder is used, and to provide high-strength concrete, excellent in surface layer quality and durability.SOLUTION: There is provided a hydraulic composition including a cement composition containing Portland cement and blast furnace slag fine powder, and a cement admixture containing calcium aluminate and anhydrous gypsum, in which the content of the blast furnace slag fine powder is 5 mass% or more and less than 40 mass% in the cement composition, and the content of the cement admixture is 20 to 40 pts.mass relative to 100 pts.mass of the total of the cement composition and the cement admixture.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydraulic composition containing Portland cement and ground granulated blast furnace slag. [Background technology]

[0002] High-strength concrete, which uses a large amount of cement during production, has a significant environmental impact because it emits a large amount of carbon dioxide. In response to this, blended cements such as blast-furnace cement and fly ash cement have recently been attracting attention as alternatives to Portland cement, from the perspectives of effectively utilizing by-products and reducing carbon dioxide emissions, a major cause of global warming. Among these, blast-furnace cement is a blend of Portland cement and ground granulated blast-furnace slag, a by-product of steelworks. The addition of ground granulated blast-furnace slag reduces the amount of Portland cement used and also reduces carbon dioxide emissions. Cement using ground granulated blast-furnace slag is standardized as blast-furnace cement in JIS R 5201. According to this standard, the content of ground granulated blast-furnace slag must be greater than 5% by mass but not greater than 30% by mass for Type A blast-furnace cement, greater than 30% by mass but not greater than 60% by mass for Type B blast-furnace slag, and greater than 60% by mass but not greater than 70% by mass for Type C blast-furnace slag. However, the majority of cement currently in circulation and in use is Type B cement, which contains around 50% by mass of ground granulated blast furnace slag, with Type A and Type C being used only in very small quantities.

[0003] Concrete using ground granulated blast furnace slag tends to have a lower compressive strength as the content of ground granulated blast furnace slag increases. In particular, strength development is poor at the early age, and compared to concrete using only Portland cement, the curing period needs to be extended, which tends to lengthen the construction period. Also, although a long-term strength increase effect can be expected, 2 However, it is not suitable for high-strength concrete exceeding 1000 kJ / cm2. Various studies have been conducted to solve this problem (for example, Patent Document 1). However, the reality is that this method has not necessarily become widespread. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-321949 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a hydraulic composition that exhibits excellent early and long-term strength development even when using blast-furnace cement containing ground granulated blast-furnace slag, and also provides high-strength concrete with good surface quality and excellent durability. [Means for solving the problem]

[0006] As a result of extensive research into the above-mentioned problems, the present inventors have found that the problems can be solved and have completed the present invention. That is, the present invention relates to the following [1] to [6]. [1] A hydraulic composition comprising a cement composition containing Portland cement and ground granulated blast furnace slag, and a cement admixture containing calcium aluminate and anhydrous gypsum, wherein the content of the ground granulated blast furnace slag in the cement composition is 5% by mass or more and less than 40% by mass, and the amount of the cement admixture is 20 to 40 parts by mass per 100 parts by mass of the total of the cement composition and the cement admixture. [2] The hydraulic composition of [1], wherein the calcium aluminate has a molar ratio of CaO to Al2O3 of 0.9 to 1.5 and a vitrification rate of less than 50%. [3] Mortar or concrete containing the hydraulic composition of [1] or [2]. [4] Surface air permeability coefficient (kT) is 0.05 × 10 -16 m 2 Mortar or concrete as follows: (3) [5] Compressive strength at 91 days is 80N / mm 2 High-strength mortar or concrete as specified in [3] or [4] above. [6] A method for producing mortar or concrete according to [3], characterized in that a kneaded product containing the cement composition, aggregate, and water is produced, and then the cement admixture is mixed therein. [Effects of the Invention]

[0007] The cement composition containing ground granulated blast furnace slag, which can reduce carbon dioxide emissions, can be used to obtain a hydraulic composition that exhibits excellent early and long-term strength development. Furthermore, high-strength concrete with good surface quality and excellent durability can be produced. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described. The hydraulic composition of the present invention is a hydraulic composition comprising a cement composition containing Portland cement and ground granulated blast furnace slag, and a cement admixture containing calcium aluminate and anhydrous gypsum, wherein the content of ground granulated blast furnace slag in the cement composition is 5% by mass or more and less than 40% by mass, and the amount of the cement admixture is 20 to 40 parts by mass per 100 parts by mass of the total of the cement composition and the cement admixture.

[0009] The Portland cement used in the present invention includes various types of Portland cement, such as normal, high-early-strength, and moderate-heat. Any one type of Portland cement can be used, but two or more types of cement may also be used in combination. Normal Portland cement is preferred for its versatility.

[0010] The ground granulated blast furnace slag used in the present invention is a fine powder obtained by pulverizing granulated blast furnace slag produced in the pig iron manufacturing process, and it is preferable to use ground granulated blast furnace slag for concrete specified by the Japanese Industrial Standards. The fineness of the ground granulated blast furnace slag is 3000 to 8000 cm in terms of Blaine specific surface area. 2 / g is preferred, and 3500 to 6000 cm 2 / g is more preferred.

[0011] The content of ground granulated blast furnace slag in the cement composition of the present invention is 5% by mass or more and less than 40% by mass from the viewpoints of reducing carbon dioxide emissions, the surface layer air permeability coefficient, and strength development. If it is less than 5% by mass, the effect of reducing carbon dioxide emissions is not sufficiently obtained, and the long-term strength elongation is also reduced, making it difficult to obtain high-strength concrete. On the other hand, if the content of ground granulated blast furnace slag is 40% by mass or more, the surface layer air permeability coefficient is reduced, and the long-term strength development is also reduced, making it difficult to obtain high-strength concrete. The content of ground granulated blast furnace slag is more preferably 10% by mass or more and less than 30% by mass.

[0012] The cement admixture of the present invention contains calcium aluminate and anhydrous gypsum. From the viewpoint of early strength development, the content of calcium aluminate in the cement admixture is preferably 40 to 70 mass%. Furthermore, from the viewpoint of early strength development, the content of anhydrous gypsum is preferably 50 to 200 mass parts, more preferably 70 to 150 mass parts, per 100 mass parts of calcium aluminate.

[0013] The calcium aluminate used in the present invention is a compound composed of CaO and Al2O3, and the molar ratio of CaO to Al2O3 (CaO / Al2O3 molar ratio) is preferably 0.9 to 1.5. If the CaO / Al2O3 molar ratio is less than 0.9, there is a risk that the development of early strength will decrease. On the other hand, if the CaO / Al2O3 molar ratio exceeds 1.5, there is a risk that it will be difficult to ensure workability when made into mortar or concrete. The CaO / Al2O3 molar ratio is more preferably 0.95 to 1.45, and even more preferably 1.0 to 1.4.

[0014] Furthermore, the calcium aluminate in the present invention is primarily composed of crystalline calcium aluminate, and specifically, the vitrification rate of calcium aluminate is preferably less than 50%. If it exceeds 50%, it may be difficult to ensure workability when made into mortar or concrete. The vitrification rate is more preferably 5 to 45%, and even more preferably 10 to 40%. The vitrification rate can be measured by the calibration curve method or the Rietveld method using an X-ray diffractometer.

[0015] Calcium aluminate can be produced using CaO raw materials such as limestone (calcium carbonate), quicklime, and slaked lime, and Al2O3 raw materials such as aluminum oxide, aluminum hydroxide, bauxite, and alum shale. Calcium aluminate slag, a by-product, can also be used as a raw material. These raw materials are blended to achieve a predetermined CaO / Al2O3 molar ratio, and then melted and fired at 1400°C or higher in a melting furnace or industrial kiln to produce calcium aluminate. Small amounts of impurities derived from natural raw materials may be present within limits that do not affect the performance of the present invention. Examples of such impurities include SiO2, Al2O3, Fe2O3, MgO, MnO, TiO2, SO3, and P2O5. The molten and fired product is then pulverized to produce a powder. The powder size should be a Blaine specific surface area of ​​2000 to 7000 cm2. 2 / g is preferred, and 3000 to 6000 cm 2 / g is more preferred.

[0016] The anhydrous gypsum used in the present invention may be natural anhydrous gypsum or various anhydrous gypsums that are industrially produced or produced as by-products. Examples of industrially produced anhydrous gypsum include hydrofluoric gypsum and phosphate gypsum. The fineness of the anhydrous gypsum is 5000 to 9000 cm in terms of Blaine specific surface area. 2 / g is preferred, and 6000 to 8000 cm 2 / g is more preferred.

[0017] The cement admixture may further contain metal salts such as aluminum sulfate, alkali metal sulfate, and alkali metal carbonate. Aluminum sulfate and its hydrate can be used as the aluminum sulfate. Examples of alkali metal sulfates include lithium sulfate, potassium sulfate, and sodium sulfate. Examples of alkali metal carbonates include lithium carbonate, potassium carbonate, and sodium carbonate. One or more of these can be used. In particular, from the viewpoint of early strength development in low-temperature environments, it is preferable to use an alkali metal sulfate and an alkali metal carbonate in combination. The content of each metal salt is preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass, of aluminum sulfate per 100 parts by mass of calcium aluminate. Furthermore, the content of the alkali metal sulfate is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass. Furthermore, the content of the alkali metal carbonate is preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass.

[0018] The hydraulic composition of the present invention contains 20 to 40 parts by mass of the cement admixture relative to 100 parts by mass of the total of the cement composition and the cement admixture. If the amount is less than 20 parts by mass, sufficient early strength development and drying shrinkage reduction effect cannot be obtained, while if the amount is more than 40 parts by mass, the concrete may not have sufficient workability, resulting in a risk of deterioration in workability. 23 to 38 parts by mass is preferred, and 25 to 35 parts by mass is more preferred. Hereinafter, the cement composition and cement admixture may be collectively referred to as a binder. The term "binder" is commonly used in concrete, and specifically refers to a generic term for anything that reacts with water to produce a substance that contributes to the development of strength in concrete. Examples include pozzolanic substances, expansive additives, etc.

[0019] The hydraulic composition of the present invention can be used as mortar or concrete by adding aggregate and water. The aggregate can be fine aggregate and coarse aggregate commonly used in the production of mortar and concrete. Examples of such fine aggregate and coarse aggregate include river sand, sea sand, mountain sand, crushed sand, artificial fine aggregate, slag fine aggregate, recycled fine aggregate, silica sand, river gravel, land gravel, crushed stone, artificial coarse aggregate, slag coarse aggregate, and recycled coarse aggregate. The amount of aggregate mixed is preferably 200 to 700 parts by mass, more preferably 200 to 600 parts by mass, per 100 parts by mass of binder. When fine aggregate and coarse aggregate are used in combination, the fine aggregate ratio is preferably 10 to 60%. The unit amount of aggregate in concrete is 500 to 1400 kg / m for both fine and coarse aggregate. 3 is preferable, and more preferably 600 to 1000 kg / m 3 is preferred.

[0020] The water used in the mortar or concrete is not particularly limited, and tap water, etc., can be used. From the viewpoint of early strength development and workability, the amount of water to be added is preferably 25 to 50 parts by mass, more preferably 30 to 40 parts by mass, per 100 parts by mass of binder. The unit amount of water in concrete is 100 to 300 kg / m 3 is preferable, and 120 to 200 kg / m 3 is more preferred.

[0021] The mortar or concrete of the present invention preferably further contains a retarder. By adding a predetermined amount of retarder, the working time (work life) of the mortar or concrete can be ensured. Examples of retarders include organic acids such as citric acid, gluconic acid, malic acid, and tartaric acid, or their salts, boric acid, borates such as sodium borate, phosphates, and sugars. The amount of retarder added is appropriately adjusted within the range of 0.1 to 5.0 parts by mass per 100 parts by mass of binder.

[0022] In addition to the above-mentioned components, various admixtures (materials) may be added to the mortar or concrete using the hydraulic composition of the present invention, if necessary, to the extent that the features of the present invention are not impaired. Examples include water-reducing agents, high-performance water-reducing agents, air-entraining agents, air-entraining water-reducing agents, high-performance air-entraining water-reducing agents, thickeners, expansive agents, shrinkage-reducing agents, cement polymers, waterproofing agents, rust inhibitors, antifreeze agents, water-retaining agents, pigments, efflorescence inhibitors, foaming agents, antifoaming agents, water-repellents, fibers, etc.

[0023] By using the hydraulic composition of the present invention, it is possible to obtain mortar or concrete that is excellent in both early strength development and long-term strength development. Specifically, the compressive strength at 1 day of age is 24 N / mm 2 or more, and the compressive strength at 91 days is 80N / mm 2 or more, or 90N / mm 2 or more, even 100N / mm 2 High strength concrete can be obtained. In addition, concrete with a small surface layer air permeability coefficient (kT) of 0.05 × 10 -16 m 2 The following concrete can be obtained. A small surface layer air permeability coefficient can suppress deterioration factors from penetrating through the concrete surface, resulting in concrete with excellent long-term durability. The surface layer air permeability coefficient can be measured using a surface layer air permeability test using the Torrent method.

[0024] (Method of manufacturing mortar or concrete) The method for producing mortar or concrete of the present invention is not particularly limited, but preferably involves producing a kneaded mixture containing the cement composition, aggregate, and water, and then mixing the cement admixture with the kneaded mixture. The cement admixture is mixed in an amount of 20 to 40 parts by mass per 100 parts by mass of the cement composition and the cement admixture. When mixing the cement admixture, it is preferable to add a retarder as well. The amount of retarder added is appropriately adjusted within the range of 0.1 to 5.0 parts by mass per 100 parts by mass of binder so that the usable time is 30 minutes or more. The retarder is preferably added as an aqueous solution in which it has been dissolved in water in advance. The unit water content of the base concrete is adjusted taking into consideration the amount of water added together with the retarder. The amount of water per 100 parts by mass of binder (water-to-binder ratio) is preferably 25 to 50 parts by mass. In particular, when the compressive strength at 91 days is 100 N / mm 2 In order to produce high strength concrete exceeding this, the amount is preferably 25 to 40 parts by mass. [Example]

[0025] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0026] Example 1 (1) Preparation of calcium aluminate The raw materials used were limestone (CaO content 56% by mass, Al2O3, MgO, and SiO2 contents each less than 0.5% by mass) and aluminium shale (Al2O3 content 87% by mass, Fe2O3 content 1% by mass, SiO2 content 5% by mass, CaO and MgO contents each less than 0.5% by mass), and were mixed so that the CaO / Al2O3 molar ratio was 1.3. The mixed mixture was fired in an electric furnace at 1500°C for 3 hours. After firing, the mixture was removed from the furnace and immediately immersed in water. After about 5 minutes, it was removed from the water and dried in a dryer at 200°C to obtain the calcium aluminate of the present invention. This calcium aluminate was pulverized in a mill to obtain a powder having a Blaine specific surface area of ​​4000 cm 2The calcium aluminate powder was analyzed using an X-ray diffractometer and found to be composed mainly of CaO·Al2O3 with a vitrification rate of 15%.

[0027] (2) Preparation of cement admixture Anhydrous gypsum and various inorganic salts were added to the calcium aluminate and mixed for 10 minutes to prepare a cement admixture (symbol: Ad). Anhydrous gypsum (commercial product; Blaine specific surface area 7100 cm) 2 / g) was used in the experiment, and was blended with 100 parts by mass of calcium aluminate, 6 parts by mass of sodium sulfate (a commercially available reagent product), and 6 parts by mass of lithium carbonate (a commercially available reagent product).

[0028] (3) Concrete manufacturing The materials used are shown in Table 1. The cement compositions were prepared by mixing ordinary Portland cement with 0, 10, 25, or 50% by mass of ground granulated blast furnace slag. Table 2 shows the concrete mix when the binder (total of cement composition and cement admixture) is 100 parts by mass. The amount of water was set to 35 parts by mass per 100 parts by mass of binder, and 0.50 to 0.55% by mass of admixture was added to the cement composition. The specified amounts of materials, excluding the cement admixture and retarder, were added to a concrete mixer and mixed for two minutes to prepare base concrete. For the level where cement admixture was added, water containing the cement admixture and retarder was added to this base concrete and mixed for another minute. The amount of cement admixture was 30 parts by mass per 100 parts by mass of binder. 0.6 parts by mass of retarder was added per 100 parts by mass of binder to ensure a usable time of 30 minutes or more. The prepared concrete was filled into a specified formwork, cured for the specified period, and then demolded for evaluation testing.

[0029] [Table 1]

[0030] [Table 2]

[0031] (4) Evaluation test 1) Surface air permeability test The surface layer air permeability coefficient was measured using a surface layer air permeability test (Torrent method). After filling a 10 x 10 x 40 cm formwork with concrete, it was cured in air and removed after 24 hours. It was then cured in water until it was 7 days old, and then left to stand at 20°C and 60% RH for 26 weeks. The measurement was carried out by creating a vacuum on the concrete surface using suction from a double chamber, then stopping the suction and measuring the one-dimensional surface layer air permeability coefficient kT (×10 -16 m 2 ) was calculated. 2) Compression strength test Compressive strength was measured according to JIS A 1108 "Testing Method for Compressive Strength of Concrete." After filling a φ10 x 20 cm formwork with concrete, it was cured in air and demolded after 24 hours, and the compressive strength was measured at 1 day of age. After demolding, the concrete was cured in water, and the compressive strength was measured at 7, 28, and 91 days of age.

[0032] (5) Test results The test results are shown in Table 3. It was found that the surface layer air permeability coefficient of concrete without added cement admixture decreases as the blast furnace slag content increases, but the surface layer air permeability coefficient of concrete with added cement admixture of the present invention decreases as the blast furnace slag content decreases. When the blast furnace slag content reaches 50 mass%, the surface layer air permeability coefficient actually increases with the addition of cement admixture, and it was found that the effect of reducing the surface layer air permeability coefficient is significant within the range of blast furnace slag content of the present invention. Furthermore, concrete using the cement admixture of the present invention not only exhibits excellent strength development in the early stages, but also exhibits good strength development over the long term. In particular, in Examples 1-4 and 1-6 in which the blast furnace slag content was 10% by mass and 25% by mass, the concrete exhibited a strength of 100 N / mm at 91 days. 2 High compressive strength was obtained. From the above, it was found that by using the hydraulic composition of the present invention, high-strength concrete having a small surface layer air permeability coefficient and excellent early and long-term strength development can be obtained.

[0033] [Table 3]

[0034] Example 2 Tests were conducted using a cement composition with a slag content of 25% by mass and varying the amount of cement admixture added. The concrete mix for each level is shown in Table 4. The test results are shown in Table 5. It was found that when the amount of cement admixture was 23 to 38 parts by mass per 100 parts by mass of binder, good strength development was achieved from the early stages to the long term, and the effect of reducing the surface layer air permeability coefficient was significant.

[0035] [Table 4]

[0036] [Table 5]

Claims

1. A hydraulic composition comprising a cement composition containing Portland cement and ground granulated blast furnace slag, and a cement admixture containing calcium aluminate and anhydrous gypsum, wherein the content of the ground granulated blast furnace slag in the cement composition is 5 mass% or more and less than 40 mass%, and the cement admixture is 20 to 40 mass parts per 100 mass parts of the total of the cement composition and the cement admixture.

2. The calcium aluminate contains CaO and Al ２ O ３ 2. The hydraulic composition according to claim 1, wherein the molar ratio of the above is 0.9 to 1.5 and the vitrification rate is less than 50%.

3. Mortar or concrete comprising the hydraulic composition according to claim 1 or 2.

4. Surface air permeability coefficient (kT) is 0.05 x 10 －１６ m ２ 4. The mortar or concrete according to claim 3, wherein:

5. Compressive strength at 91 days is 80N / mm ２ The high-strength mortar or concrete according to claim 3, wherein the high-strength mortar or concrete is as described above.

6. 4. The method for producing mortar or concrete according to claim 3, wherein a kneaded product containing the cement composition, aggregate, and water is produced, and then the cement admixture is mixed therewith.

Images