Incorporated resources of cement admixtures, mixed cement, and cement admixtures

Abstract

This invention provides a cement mixture that can replace fly ash, blast furnace slag powder, and the like. [Solution] The present invention is a cement mixture which is a rock powder that satisfies all of the following conditions (1) to (4). (1) BET specific surface area is 1.0 to 15.5 m 2 / g (2) Braine specific surface area of ​​3,000 to 7,000 cm² 2 / g (3) The amorphous phase is 16.0 to 60.0% by mass. (4) The cumulative heat generation of the simulated cement paste containing the above rock powder, measured in accordance with "Method A" as defined in "ASTM C 1897", up to 7 days of age is 20 to 200 J / g.

Description

[Technical Field]

[0001] The present invention relates to a cement mixture, a cement mixture containing the cement mixture, and a method for manufacturing the cement mixture. [Background technology]

[0002] Traditionally, the cement industry has reduced carbon dioxide emissions during cement production by replacing a portion of cement clinker, which emits carbon dioxide during manufacturing, with cement admixtures such as fly ash and blast furnace slag powder, from a carbon neutrality perspective, thereby reducing the amount of cement clinker produced. However, in recent years, carbon neutrality has also been demanded in coal-fired power plants and the steel industry, and it is expected that the amount of fly ash and blast furnace slag powder produced as by-products in these industries will decrease in the future. Therefore, there is a need for cement admixture materials that can replace fly ash and blast furnace slag powder.

[0003] Natural rocks such as calcined clay, volcanic ash, and zeolite are known as alternatives to cement admixtures such as fly ash and blast furnace slag powder. These materials can densify the concrete structure due to their high pozzolanic reactivity and improve concrete durability by suppressing alkali-silica reaction. However, they have the problem of reducing concrete fluidity because they adsorb the mixing water and admixtures. On the other hand, rock powders with low or no pozzolanic reactivity enhance the initial strength of concrete due to their fine powder effect, but do not improve long-term strength development or durability, and if the amount mixed is large, the long-term strength development of the concrete decreases.

[0004] Patent Document 1 describes a cement mixture that can be used as a substitute for fly ash or blast furnace slag powder, and includes one or more inorganic powders selected from the group consisting of shale powder, loess powder, perlite powder, obsidian powder, heated shale powder, heated loess powder, heated perlite powder, and heated obsidian powder, wherein the Blaine specific surface area of ​​the inorganic powder is 3000 cm². 2A cement additive characterized by having a concentration of 1 / g or more is described. Furthermore, Patent Document 2 describes a cement additive characterized by containing siliceous shale powder with an average particle size of 0.5 to 30 μm and an SiO2 content of 75% by mass or more. Furthermore, Patent Document 3 describes a cement additive characterized by consisting of rock powder whose expansion rate at 14 days exceeds 0.1% in the "Standard Test Method for Latent Alkali Reactivity of Aggregates (Mortal Bar Method)" specified in "ASTM C 1260". [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-30862 [Patent Document 2] Japanese Patent Publication No. 2010-163320 [Patent Document 3] Japanese Patent Publication No. 2023-58753 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a cement admixture that utilizes powders of a wide range of rock types instead of fly ash and blast furnace slag fine powder, and that can make concrete containing the above cement admixture have excellent fluidity and suppress alkali-silica reaction, regardless of whether or not they are pozzolanic. [Means for solving the problem]

[0007] The inventors of the present invention have conducted diligent studies to solve the above problems and have found that (1) the BET specific surface area is 1.0 to 15.5 m² 2 (2) The specific surface area is 3,000 to 7,000 cm². 2We have found that the above objective can be achieved by using a cement mixture of rock powder that (3) has an amorphous phase of 16.0 to 60.0% by mass, and (4) has a cumulative heat generation of 20 to 200 J / g up to 7 days of age of a simulated cement paste containing the above rock powder, measured in accordance with "Method A" as defined in "ASTM C 1897", and have completed the present invention. In other words, the present invention provides the following [1] to [5]. [1] A cement mixture characterized by being a rock powder that satisfies all of the following conditions (1) to (4). (1) BET specific surface area is 1.0 to 15.5 m 2 / g (2) Braine specific surface area of ​​3,000 to 7,000 cm² 2 / g (3) The amorphous phase is 16.0 to 60.0% by mass. (4) The cumulative calorific value of the simulated cement paste containing the above rock powder, measured in accordance with "Method A" as defined in "ASTM C 1897", up to 7 days of age is 20 to 200 J / g. [2] The cement mixture described in [1] above, which is a rock powder that also satisfies all of the following conditions (5) to (7). (5) The sum of the SiO2 content and Al2O3 content is 70% by mass or more. (6) The MgO content must be 5.0% by mass or less. (7) The total alkali content is 5.6% by mass or less. [3] A mixed cement containing the cement admixture described in [1] or [2] above in a proportion of 10 to 30% by mass.

[0008] [4] A method for producing a cement mixture, wherein the rock powder obtained by crushing the rock until the residue after 45 μm sieving is 20% by mass or less satisfies all of the following conditions (1) to (4), and the rock powder is selected as the cement mixture described in [1] above. (1) BET specific surface area is 1.0 to 15.5 m 2 / g (2) Braine specific surface area of ​​3,000 to 7,000 cm²2 being / g (3) The amorphous phase is 16.0 to 60.0% by mass (4) The cumulative heat of hydration of the simulated cement paste containing the rock powder measured in accordance with "Method A" specified in "ASTM C 1897" up to 7 days of age is 20 to 200 J / g [5] A method for producing a cement admixture, wherein the rock powder obtained by pulverizing a rock until the residue on a 45-μm sieve is 20% by mass or less is selected as the cement admixture described in [2] above only when all of the following conditions (1) to (7) are satisfied (1) The BET specific surface area is 1.0 to 15.5 m 2 / g (2) The Blaine specific surface area is 3,000 to 7,000 cm 2 / g (3) The amorphous phase is 16.0 to 60.0% by mass (4) The cumulative heat of hydration of the simulated cement paste containing the rock powder measured in accordance with "Method A" specified in "ASTM C 1897" up to 7 days of age is 20 to 200 J / g (5) The total of the content of SiO2 and the content of Al2O3 is 70% by mass or more (6) The content of MgO is 5.0% by mass or less (7) The total alkali content is 5.6% by mass or less [Advantages of the Invention]

[0009] According to the cement admixture of the present invention, powders of a wide range of rock varieties can be used as cement admixtures instead of fly ash, blast furnace slag fine powder, etc In addition, regardless of the presence or absence of pozzolanic reactivity, concrete etc. containing the cement admixture of the present invention is excellent in fluidity and is also suppressed in alkali-silica reaction [Embodiments for Carrying Out the Invention]

[0010] The cement admixture of the present invention is a rock powder that satisfies all of the following conditions (1) to (4) (1) BET specific surface area is 1.0 to 15.5 m 2 / g (2) Braine specific surface area of ​​3,000 to 7,000 cm² 2 / g (3) The amorphous phase is 16.0 to 60.0% by mass. (4) The cumulative heat generation of the simulated cement paste containing the above rock powder, measured in accordance with "Method A" as defined in "ASTM C 1897", up to 7 days of age is 20 to 200 J / g. The details are explained below.

[0011] [Condition (1)] The BET specific surface area of ​​rock powder is 1.0 to 15.5 m². 2 / g, preferably 1.5 to 12.0m 2 / g, more preferably 2.0~10.0m 2 / g, particularly preferably 2.5 to 7.5m 2 The value is / g. The above BET specific surface area is 1.0m². 2 If the BET specific surface area is less than 15.5 m², the strength development of the mixed cement containing cement admixture (hereinafter also simply referred to as "mixed cement") will decrease. 2 For weights exceeding [amount] / g, the cost of crushing the rock becomes excessive. Furthermore, the adsorption of moisture and cement admixtures onto the surface of the rock powder particles reduces the fluidity of concrete and other materials containing mixed cement before they harden. [Condition (2)] The specific surface area of ​​rock powder is 3,000 to 7,000 cm². 2 / g, preferably 3,200~6,500cm 2 / g, more preferably 3,500~5,500cm 2 / g, particularly preferably 3,700 to 5,000 cm 2 The value is / g. The above Braine specific surface area is 3,000 cm². 2 If the value is less than / g, the strength development of the mixed cement will decrease. The above Blaine specific surface area is 7,000 cm². 2For concentrations exceeding [number]g, the cost of crushing the rock becomes excessive. Furthermore, the fluidity of concrete and other materials containing blended cement before hardening decreases.

[0012] [Condition (3)] The amorphous phase of the rock powder is 16.0 to 60.0% by mass, preferably 18.0 to 55.0% by mass, more preferably 20.0 to 50.0% by mass, and particularly preferably 20.0 to 45.0% by mass. If the amorphous phase is less than 16.0% by mass, the strength development of the mixed cement and the inhibitory effect on alkali-silica reaction are reduced. If the amorphous phase is 60.0% by mass or less, the fluidity of concrete and the like before hardening, including the mixed cement, is improved. [Condition (4)] The cumulative heat generation of the simulated cement paste containing the above-mentioned rock powder, measured in accordance with "Method A" as defined in "ASTM C 1897," up to 7 days of curing is 20 to 200 J / g, preferably 25 to 150 J / g, more preferably 35 to 100 J / g, and particularly preferably 50 to 80 J / g. If the cumulative heat generation is less than 20 J / g, the strength development of the mixed cement and the inhibitory effect on alkali-silica reaction are reduced. If the cumulative heat generation is 200 J / g or less, the fluidity of concrete and the like before hardening, including the mixed cement, becomes good.

[0013] The cement mixture of the present invention is preferably a rock powder that satisfies all of the above conditions (1) to (4), and further satisfies all of the following conditions (5) to (7). [Condition (5)] The combined content of SiO2 and Al2O3 in the rock powder is 70% by mass or more, preferably 73-90% by mass, and particularly preferably 74-80% by mass. If the combined content is 70% by mass or more, the strength development of the mixed cement can be further improved. [Condition (6)] The MgO content of the rock powder is preferably 5.0% by mass or less, more preferably 0.5 to 4.0% by mass, and particularly preferably 1.0 to 3.5% by mass. If the above content is 5.0% by mass or less, the strength development of the mixed cement can be improved, and abnormal expansion of concrete and the like containing the mixed cement can be suppressed.

[0014] [Condition (7)] The total alkali content of the rock powder is preferably 5.6% by mass or less, more preferably 1.0 to 5.5% by mass, and particularly preferably 2.0 to 5.2% by mass. If the total alkali content is 5.6% by mass or less, the inhibitory effect on alkali-silica reaction can be further improved. If the rock powder satisfies all of the above conditions (1) to (4), or the above conditions (1) to (4) plus all of the above conditions (5) to (7), then a cement mixture containing such rock powder can be made to have excellent fluidity before hardening and to suppress alkali-silica reaction. [Condition (8)] The rock powder is preferably one that satisfies the conditions (1) to (4) above, or, in addition to the conditions (1) to (7) above, also satisfies the following condition (8). (8) The moisture content is 3.0 or less. The moisture content of the rock powder is preferably 3.0% or less, more preferably 0.1 to 2.0%, and particularly preferably 0.3 to 1.5%. If the moisture content is 3.0% or less, pretreatment such as drying is unnecessary, which reduces costs and makes it easier to control the quality of the cement.

[0015] The mixed cement of the present invention contains the above-mentioned cement admixture in a proportion of 10 to 30% by mass (preferably 15 to 28% by mass). If the above proportion is less than 10% by mass, the effect of reducing the total amount of carbon dioxide emitted during cement clinker production by replacing a portion of the cement clinker with the cement admixture is reduced. If the above proportion exceeds 30% by mass, the strength development of the mixed cement decreases. Blended cement contains cement in addition to cement admixtures. The cement included in the blended cement is not particularly limited and includes various types of Portland cement such as ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement, as well as blast furnace cement, fly ash cement, silica cement, eco-cement, and fast-setting cement. These may be used individually or in combination of two or more types. Furthermore, the mixed cement may contain, in addition to the cement mixture consisting of rock powder of the present invention, powder materials such as fly ash, blast furnace slag fine powder, and silica fume, which are commonly used as cement mixtures. The proportion of powder materials other than cement and the above-mentioned cement mixture is preferably 10% by mass or less, more preferably 5% by mass or less.

[0016] An example of a method for producing the cement mixture of the present invention is to select the rock powder obtained by crushing rock until the residue on a 45 μm sieve is 20% by mass or less as the rock powder, only if the rock powder satisfies all of the above conditions (1) to (4). Furthermore, from the viewpoint of obtaining a cement mixture of superior quality, the rock powder obtained by crushing the rock until the residue on a 45 μm sieve is 20% by mass or less may be selected as the cement mixture only if it satisfies all of the conditions (1) to (7) or all of the conditions (1) to (8) described above. According to the above method, it is possible to obtain a cement mixture that reduces the cost of crushing while making concrete and other materials highly fluid and suppressing alkali-silica reaction. The strength development of the mixed cement can be further improved by crushing the rock until the residue on a 45 μm sieve is 20% by mass or less, preferably 18% by mass or less. The lower limit of the residue on a 45 μm sieve is not particularly limited, but from the viewpoint of reducing the cost of crushing, it is preferably 10% by mass, more preferably 15% by mass. The grinding method is not particularly limited, but general grinders such as ball mills and rod mills can be used. After crushing the rock, the obtained rock powder is examined to see if it satisfies all of the conditions (1) to (4) described above, or any other specific conditions. If the rock powder does not satisfy all of the specific conditions, it is determined that the rock powder is unsuitable as a cement admixture and is not selected for use as a cement admixture. Such rock powder is not used as a cement admixture and is instead used, for example, as earthwork material or discarded. [Examples]

[0017] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. [Examples 1-5, Comparative Examples 1-9] 5 kg of rock was crushed using a jaw crusher (Retsch, model: BB200 Mangan 2012) until the particle size was 5 mm or less. Then, it was further crushed using a roll crusher (Yoshida Seisakusho, model: 1022-BF) until the particle size was 1 mm or less. Next, it was crushed using a batch-type ball mill (Yoshida Seisakusho, dimensions: φ50 × 50 cm) until the residue on a 45 μm sieve was 20% by mass or less, yielding rock powders A to N shown in Tables 1 to 3. Note that rock powders A to N are all made from different types or origins of rock. The total time required for crushing is shown in Table 1. The physical and chemical properties of the obtained rock powder were measured according to the following method. [45μm sieve residue] The residue of the rock powder after sieving with a 45 μm sieve was measured in accordance with "ASTM C430-17". [Particle size distribution] The particle size distribution of the rock powder was measured using the Microtrac-Bell MT3000II particle size distribution analyzer, and D10, D50, and D90 values ​​were determined.

[0018] [Moisture] The moisture content of the rock powder was measured in accordance with "JIS R 6201:2015 (Fly ash for concrete)". [Amount of methylene blue adsorbed] The amount of methylene blue adsorbed by rock powder (indicated as "MB adsorption amount" in Table 2) was measured in accordance with "JCAS I-61:2008". [Amorphous phase] The proportion of amorphous phase in rock powder was measured using X-ray fluorescence diffraction (XRD) in a scanning range of 5–65°. The major minerals contained in the rock were identified from the resulting diffraction patterns using DIFFRAC.EVA (Bruker AXS), and quantified using the external standard method of TOPAS ver.6.0 (Bruker AXS). Calcium carbonate with a purity of 99% was used as the standard sample for the external standard method. [Cumulative heat generation up to 7 days of age] The cumulative heat generation of a simulated cement paste containing rock powder up to 7 days of age was measured in accordance with Method A of "ASTM C 1897". [Chemical composition] The chemical composition of the rock powder was quantified using X-ray fluorescence analysis (XRF) and a calibration curve method using glass beads. The calibration curves used were those for clays and limestones, prepared in accordance with "JIS R 5204:2019 (X-ray fluorescence analysis method for cement)". The results are shown in Tables 1-3.

[0019] [Table 1]

[0020] [Table 2]

[0021] [Table 3]

[0022] A mixed cement was prepared by setting the total of ordinary Portland cement and the types of rock powders shown in Table 4 to 100% by mass, and then adding 25% by mass of the above-mentioned rock powders. The compressive strength of the resulting mortar containing the mixed cement was measured in accordance with "JIS R 5201:2015 (Physical Testing Methods for Cement)". Furthermore, the activity index and flow value ratio of the above-mentioned mortar were measured in accordance with Annex C of "JIS R 6201:2015 (Fly Ash for Concrete)". A higher flow rate ratio (for example, 70% or more, preferably 80% or more, more preferably 90% or more) indicates superior fluidity. In accordance with the accelerated mortar bar method of "ASTM C 1567," the expansion rate (ASR expansion rate) at 14 days of age was measured for mortar bars using the above-mentioned mixed cement and andesite as fine aggregate. The ratio of the expansion rate of the mixed cement-containing mortar bar to the expansion rate of the ordinary Portland cement-containing mortar bar (0.49%) was calculated as the ASR ratio. The smaller the ASR ratio (for example, less than 1.0, preferably 0.9 or less, more preferably 0.6 or less), the greater the effect of suppressing the alkali-silica reaction. The results for each are shown in Table 4.

[0023] [Table 4]

[0024] From the results in Table 4, the activity index of Examples 1 to 5 was 73-76% at 28 days of age and 72-82% at 91 days of age, with a flow value ratio of 83-97%. These values ​​meet the standards for fly ash type IV (activity index of 60% or higher at 28 days of age, activity index of 70% or higher at 91 days of age, flow value ratio of 75% or higher) specified in "JIS A 6201:2015 (Fly Ash for Concrete)". Therefore, it can be seen that the cement mixtures of Examples 1 to 5 can be used as a substitute for fly ash. Furthermore, the compressive strength of Examples 1-5 at 28 days of age was 48.2-54.9 N / mm². 2This value is the standard for fly ash cement type A as specified in "JIS A 5213:2009 (Fly Ash Cement)" (compressive strength at 28 days of age: 42.5 N / mm²). 2 Since the above conditions are met, it can be seen that the cement mixtures of Examples 1 to 5 can be used as a substitute for fly ash. Furthermore, the ASR ratios of Examples 1 to 5 were 0.2 to 0.8, indicating that the mixed cements containing the cement admixtures of Examples 1 to 5 exhibited suppressed alkali-silica reaction.

Claims

1. A cement mixture characterized by being a rock powder that satisfies all of the following conditions (1) to (4). (1) BET specific surface area is 1.0 to 15.5 m ２ / g (2) Brain specific surface area of ​​3,000 to 7,000 cm² ２ / g (3) The amorphous phase is 16.0 to 60.0% by mass. (4) The cumulative heat generation of the simulated cement paste containing the above rock powder, measured in accordance with "Method A" as defined in "ASTM C 1897", up to 7 days of age is 20 to 200 J / g.

2. Furthermore, the cement mixture according to claim 1 is a rock powder that satisfies all of the following conditions (5) to (7). (5) SiO ２ The content and Al ２ O ３ The total content of the ingredients must be 70% by mass or more. (6) The MgO content is 5.0% by mass or less. (7) The total alkali content is 5.6% by mass or less.

3. A mixed cement comprising the cement admixture described in claim 1 or 2 in a proportion of 10 to 30% by mass.

4. A method for producing a cement mixture, comprising selecting the rock powder obtained by crushing rock until the residue after sieving at 45 μm is 20% by mass or less, as the cement mixture according to claim 1, only if the rock powder satisfies all of the following conditions (1) to (4). (1) BET specific surface area is 1.0 to 15.5 m ２ / g (2) Brain specific surface area of ​​3,000 to 7,000 cm² ２ / g (3) The amorphous phase is 16.0 to 60.0% by mass. (4) The cumulative heat generation of the simulated cement paste containing the above rock powder, measured in accordance with "Method A" as defined in "ASTM C 1897", up to 7 days of age is 20 to 200 J / g.

5. A method for producing a cement mixture, wherein the rock powder obtained by crushing rock until the residue after sieving at 45 μm is 20% by mass or less satisfies all of the following conditions (1) to (7), is selected as the cement mixture according to claim 2. (1) BET specific surface area is 1.0 to 15.5 m ２ / g (2) The brain specific surface area is 3,000 to 7,000 cm ２ / g (3) The amorphous phase is 16.0 to 60.0% by mass. (4) The cumulative heat generation of the simulated cement paste containing the above rock powder, measured in accordance with "Method A" as defined in "ASTM C 1897", up to 7 days of age is 20 to 200 J / g. (5) SiO ２ The content and Al ２ O ３ The total content of the ingredients must be 70% by mass or more. (6) The MgO content is 5.0% by mass or less. (7) The total alkali content is 5.6% by mass or less.

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