Alumina cement composition and method for producing concrete

Abstract

To provide an alumina cement composition capable of suppressing an increase in adiabatic temperature when formed into concrete.SOLUTION: An alumina cement composition includes alumina cement and blast furnace slag, wherein a strength ratio (X / Y) of a compressive strength (X) of a cured body at an age of 28 days of a mortar composition containing the alumina cement composition to a compressive strength (Y) of the cured body after accelerated conversion treatment is 0.8 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an alumina cement composition and a method for producing concrete. [Background technology]

[0002] Alumina cement has superior fire resistance, early hardening properties, and chemical resistance compared to ordinary Portland cement. Its particularly rapid hardening properties mean that it is sometimes used for emergency repairs such as airport pavements and road bridge thickening. However, because hydrate conversion over the long term causes a decrease in strength, it is not widely used for permanent applications.

[0003] On the other hand, there is a growing momentum to build a waste-recycling society that reuses waste, and the use of ground granulated blast furnace slag is being recommended as part of efforts to reduce environmental impact.Therefore, there has been a desire to develop a material that has excellent rapid setting and early strength development properties, even in blended cement that incorporates ground granulated blast furnace slag.

[0004] Patent Document 1 shows that the use of a blended cement that combines alumina cement and ground granulated blast furnace slag can contribute to an environmentally recycling-oriented society, and that the use of this blended cement in combination with an accelerator containing calcium aluminate or gypsum can provide good quick-setting properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4498714 Summary of the Invention [Problem to be solved by the invention]

[0006] However, Patent Document 1 does not disclose how to deal with conversions specific to alumina cement, nor does it disclose how to provide an alumina cement composition that can suppress an increase in adiabatic temperature when made into concrete.

[0007] In view of the above, an object of the present invention is to provide an alumina cement composition that can suppress an increase in adiabatic temperature when made into concrete. [Means for solving the problem]

[0008] In view of the above problems, the present inventors have conducted extensive research and have come up with the following invention, which has been found to solve the above problems.

[0009] [1] An alumina cement composition containing alumina cement and blast furnace slag, The alumina cement composition has a strength ratio (X / Y) of 0.8 or less between the compressive strength (X) of a hardened body of a mortar composition containing the alumina cement composition at an age of 28 days and the compressive strength (Y) of the hardened body after an accelerated conversion treatment. [2] The alumina cement composition according to [1], wherein the Blaine specific surface area ratio (A / B) of the Blaine specific surface area (A) of the alumina cement to the Blaine specific surface area (B) of the blast furnace slag is 0.5 to 1.4. [3] The alumina cement composition according to [1] or [2], wherein the mass ratio of the blast furnace slag to the total of the alumina cement and the blast furnace slag is 0.45 to 0.8. [4] A method for producing concrete, comprising mixing the alumina cement composition according to any one of [1] to [3] with aggregate and kneading the mixture with cold water at 15°C or below. [5] The method for producing concrete according to [4], wherein the cold water is added in multiple batches and the kneading is carried out. [6] The method for producing concrete according to [4] or [5], wherein the mass ratio (W / B) of the cold water to the binder component in the alumina cement composition is 20 to 60. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an alumina cement composition that can suppress an increase in adiabatic temperature when made into concrete. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, one embodiment (the present embodiment) of the alumina cement composition and the method for producing concrete of the present invention will be described in detail. Hereinafter, concrete may collectively refer to cement paste, mortar, and concrete.

[0012] [Alumina cement composition] The alumina cement composition according to this embodiment contains alumina cement and blast furnace slag, and has a strength ratio (X / Y) of 0.8 or less between the compressive strength (X) of a hardened body of a mortar composition containing the alumina cement composition at an age of 28 days and the compressive strength (Y) of the hardened body after an accelerated conversion treatment.

[0013] In concrete containing alumina cement, there is a concern that conversion may progress due to an increase in the adiabatic temperature during hardening. When this alumina cement composition is used to make concrete, the rise in the adiabatic temperature can be suppressed, which in turn suppresses self-conversion of the alumina cement and prevents cracking of the concrete due to thermal stress.

[0014] The compressive strength (X) is measured as follows: an alumina cement composition is mixed with fine aggregate, water is added, and the resulting mortar composition is kneaded. The mortar composition is poured into a 40 × 40 × 160 mm formwork, and a hardened body is obtained after 28 days. The compressive strength (X) of the hardened body is measured in accordance with JIS R 5201.

[0015] The compressive strength (Y) is measured as follows: the hardened body is subjected to an accelerated conversion treatment in which it is cured at 40°C for 14 days, and then the compressive strength (Y) is measured in accordance with JIS R 5201.

[0016] The intensity ratio (X / Y) according to this embodiment is determined by the reaction state between alumina cement and blast furnace slag, and therefore serves as an index of the reactivity between alumina cement and blast furnace slag. When this ratio is 0.8 or less, the increase in the adiabatic temperature described above can be suppressed. The intensity ratio (X / Y) is preferably 0.7 or less, and more preferably 0.6 or less. The lower limit of the intensity ratio (X / Y) is preferably as small as possible, but in practice it is about 0.2.

[0017] To make the strength ratio (X / Y) 0.8 or less, for example, it is preferable to use cold water at 15° C. or less when kneading. The strength ratio can be easily adjusted by adjusting the temperature and amount of cold water.

[0018] The alumina cement according to this embodiment has a mineral composition containing monocalcium aluminate (CaO·Al2O3:CA) as the main component (50% by mass or more), and is produced by blending bauxite, high-alumina, or refined alumina as the alumina source, and limestone or quicklime as the calcia source, so that CA is the main component in the product, and pulverizing the clinker melted or fired in an electric furnace, radiant furnace, open hearth, rotary kiln, or the like, with a grinder such as a tube mill, vibratory mill, jet mill, or roller mill. Commercially available alumina cement can also be used. The CA content in alumina cement can be determined by powder X-ray diffraction / Rietveld analysis.

[0019] The particle size of the alumina cement is not particularly limited, but the Blaine specific surface area value (hereinafter sometimes referred to as the "Blaine value") based on JIS R 5201 (physical testing method for cement) is 2,500 cm 2 / g or more, and 3,000 to 6,000 cm 2 / g is more preferred.

[0020] The blast furnace slag according to this embodiment is a powder containing aluminosilicate as its main component, obtained by crushing or crushing and classifying molten slag, a by-product of producing pig iron from iron ore in a blast furnace. Its chemical components are a CaO content of 30 to 45 mass%, a SiO2 content of 20 to 35 mass%, an Al2O3 content of 5 to 15 mass%, and an MgO content of 10 mass% or less, and its density is 2.50 to 3.20 g / cm3. 3 As the blast furnace slag, for example, that specified in JIS A 6206 can be used.

[0021] In this embodiment, the particle size of the blast furnace slag is set to 2,750 cm in Blaine value from the viewpoint of strength development. 2 / g or more, and 2 From the viewpoint of strength development, the particle size of blast furnace slag is preferably 10,000 cm in Blaine value. 2 From the viewpoint of strength development, the particle size of blast furnace slag is preferably 4,000 to 9,000 cm in Blaine value. 2 / g is more preferred. The above JIS standard requires that blast furnace slag have a Blaine specific surface area of ​​2,750 cm 2 / g or more 3,500cm 2 / g or less, 3,500 cm 2 / g or more 5,000cm 2 / g or less, 5,000 cm 2 / g or more 7,000cm 2 / g or less, 7,000 cm 2 / g or more 10,000cm 2 Four grades of / g have been defined.

[0022] Here, the Blaine specific surface area ratio (A / B) of the Blaine specific surface area (A) of the alumina cement to the Blaine specific surface area (B) of the blast furnace slag is preferably 0.5 or more, more preferably 0.5 to 1.4, and most preferably 0.6 to 1.3, from the viewpoints of fluidity, reactivity, and suppression of an increase in adiabatic temperature.

[0023] Furthermore, the mass ratio of the blast furnace slag to the total of the alumina cement and the blast furnace slag is preferably 0.45 to 0.8, more preferably 0.5 to 0.7, and even more preferably 0.53 to 0.65, from the viewpoint of ensuring early-age strength.

[0024] The alumina cement composition according to this embodiment may contain, in addition to alumina cement and blast furnace slag, ordinary cement, a high-performance water-reducing agent, an air-entraining agent, a setting adjuster, and the like. The total content of alumina cement and blast furnace slag in the alumina cement composition according to this embodiment is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0025] [Concrete manufacturing method] In the method for producing concrete according to this embodiment, the alumina cement composition of the present invention and aggregate are mixed and kneaded with cold water at 15°C or below. In this embodiment, the composition obtained by mixing the alumina cement composition with aggregate includes a mortar composition containing the alumina cement composition and fine aggregate, and a concrete composition containing the alumina cement composition, fine aggregate, and coarse aggregate.

[0026] In the method for producing concrete of this embodiment, by using cold water of 15°C or less during mixing, the strength ratio (X / Y) can be set to 0.8 or less. The temperature of the cold water is preferably 5 to 15°C.

[0027] It is preferable to add cold water during mixing in multiple batches. Adding cold water in multiple batches softens the concrete during mixing, improving its fluidity and making it easier to suppress defects in the hardened body. When adding cold water in multiple batches, the amount of cold water may be the same, or may be larger at first and gradually reduced, or conversely, may be smaller at first and gradually increased. When adding cold water in multiple batches, the number of times is preferably about 2 to 5, taking into account processing efficiency.

[0028] The mass ratio of cold water to binder components in the alumina cement composition (W / B: unit: %) is preferably 20 to 60, and more preferably 30 to 50, from the viewpoint of ensuring fluidity and strength. Here, the binder component refers to the hydraulic component of the alumina cement composition, and refers to at least the total of the alumina cement composition and blast furnace slag.

[0029] The aforementioned aggregate is not particularly limited, and any of the fine aggregates and coarse aggregates used in the production of ordinary mortar and concrete can be used. Examples of fine aggregates and coarse aggregates include river sand, sea sand, mountain sand, crushed sand, limestone sand, artificial fine aggregate, slag fine aggregate, recycled fine aggregate, silica sand, river gravel, land gravel, crushed stone, limestone aggregate, artificial coarse aggregate, slag coarse aggregate, and recycled coarse aggregate.

[0030] Furthermore, the concrete according to this embodiment may contain various admixtures (agents) as needed, provided that the effects of the present invention are not impaired. Examples of admixtures (agents) include water-reducing agents, air-entraining agents, antifoaming agents, foaming agents, waterproofing agents, rust inhibitors, expanding agents, shrinkage-reducing agents, thickeners, water-retaining agents, pigments, water-repellents, anti-efflorescence agents, fibers, and inorganic fine powders.

[0031] The kneading method is not particularly limited, and for example, a general-purpose mixer such as a tilting mixer, a pan mixer, a twin-shaft mixer, a grout mixer, a Hobart mixer, or an omni mixer can be used. [Example]

[0032] [Experimental Example 1] <Materials used> Alumina cement (AC): Commercially available, density 3.00 g / cm 3 , Blaine specific surface area 5,000 cm 2 / g, containing 50% or more by mass of monocalcium aluminate Blast furnace slag (BFS): Granulated blast furnace slag, commercially available, density 2.90 g / cm 3 , Blaine specific surface area 4,000 cm 2 / g, CaO content 42% by mass, SiO2 content 34% by mass, Al2O3 content 13% by mass, MgO content 10% by mass or less Fine aggregate: River sand from the Himekawa River system, 5mm below Water: Tap water

[0033] An alumina cement composition was prepared by mixing alumina cement and blast furnace slag to obtain the formulation shown in Table 1. The alumina cement composition was mixed with fine aggregate, and tap water at the temperature shown in Table 1 was added in the W / B ratio shown in Table 1 and kneaded to prepare a mortar composition. The fine aggregate was mixed in an amount of 300 parts by mass per 100 parts by mass of the alumina cement composition.

[0034] The prepared mortar composition was poured into a 40 x 40 x 160 mm formwork, and the compressive strength (X) of the hardened body after 28 days was measured in accordance with JIS R 5201. Furthermore, this hardened body was subjected to an accelerated conversion treatment under conditions of 40°C for 14 days in a wet state, and the compressive strength (Y) of the hardened body after the treatment was measured. The strength ratio (X / Y) between the compressive strength (X) and the compressive strength (Y) is shown in Table 1.

[0035] The prepared mortar composition was placed in a 100 mL resin container insulated with polystyrene foam, and a thermocouple was inserted. The core temperature of the mortar was measured with the container covered with a lid to examine the mortar's heat generation behavior. The mortar's heat generation behavior is the difference between the maximum temperature within one day of measurement and the temperature at the start of measurement, and is related to the adiabatic temperature when the concrete is formed. From the viewpoint of ensuring uniform and good reactivity, the mortar's heat generation behavior is preferably 22 or less, and more preferably 10 to 20. The results are shown in Table 1.

[0036] [Table 1]

[0037] [Experimental Example 2] Mortar compositions were prepared in the same manner as in Experimental Example 1, with the exception that blast furnace slag with the same composition but different Blaine values ​​was used and the Blaine specific surface area ratio was changed as shown in Table 2. The strength ratio (X / Y) was calculated and the heat generation behavior of the mortar was investigated. The results are shown in Table 2. Experiment No. 8 was the same as Experiment No. 4.

[0038] [Table 2]

[0039] [Experimental Example 3] Mortar compositions were prepared, strength ratios (X / Y) were calculated, and the heat generation behavior of the mortars was investigated in the same manner as in Experimental Example 1, except that the mass ratio of blast furnace slag to the total of alumina cement and blast furnace slag was changed as shown in Table 3. The results are shown in Table 3. Experiment No. 12 was the same as Experiment No. 5.

[0040] [Table 3] [Industrial Applicability]

[0041] The present invention can be widely used in the fields of civil engineering and construction for various concretes and secondary concrete products.

Claims

1. An alumina cement composition comprising alumina cement and blast furnace slag, The alumina cement composition, wherein the strength ratio (X / Y) of the compressive strength (X) of a hardened body of a mortar composition containing the alumina cement composition at an age of 28 days to the compressive strength (Y) of the hardened body after an accelerated conversion treatment is 0.8 or less.

2. 2. The alumina cement composition according to claim 1, wherein the Blaine specific surface area ratio (A / B) of the Blaine specific surface area (A) of the alumina cement to the Blaine specific surface area (B) of the blast furnace slag is 0.5 to 1.

4.

3. 2. The alumina cement composition according to claim 1, wherein the mass ratio of the blast furnace slag to the total of the alumina cement and the blast furnace slag is 0.45 to 0.

8.

4. A method for producing concrete, comprising mixing the alumina cement composition according to any one of claims 1 to 3 with aggregate and kneading the mixture with cold water at 15°C or below.

5. The method for producing concrete according to claim 4, wherein the cold water is added in a plurality of batches and the kneading is carried out.

6. 5. The method for producing concrete according to claim 4, wherein the mass ratio (W / B) of the cold water to the binder component in the alumina cement composition is 20 to 60.

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