Concrete manufacturing method and manufacturing apparatus

Abstract

By using blast furnace cement types A, B, and C according to the part of the structure, the high durability and low CO2 emissions of blast furnace cement can be realized. However, concrete manufacturing plants typically stock type B cement in their cement silos, and using types A or C requires replacing or expanding silos, which is inefficient. [Solution] By stocking blast furnace cement type C in a cement silo and adjusting the mixing ratio with commonly used Portland cement, blast furnace cement of any amount of blast furnace slag (types A, B, and C) can be produced in a concrete manufacturing plant. This makes it possible to produce concrete using blast furnace cement without replacing or expanding silos, thus improving the efficiency of concrete production using blast furnace cement.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for producing concrete using blast-furnace cement Class A, Class B and Class C. Background Art )

[0002] Blast-furnace cement is a cement obtained by mixing Portland cement with ground granulated blast-furnace slag (hereinafter abbreviated as blast-furnace slag), which is obtained by quenching molten blast-furnace slag generated during the steel manufacturing process via the blast-furnace process. JIS R 5211 specifies that for blast-furnace cement, the blast-furnace slag content is more than 5% and 30% or less for Class A, more than 30% and 60% or less for Class B, and more than 60% and 70% or less for Class C.

[0003] Compared to Portland cement, blast-furnace cement exhibits a lower strength development rate, but is excellent in low heat generation and durability. Furthermore, while Portland cement generates 750 kg of CO₂ per ton during production, the CO₂ emission amount of blast-furnace cement decreases substantially in proportion to the content of blast-furnace slag. For this advantage, blast-furnace cement has been actively researched as an environmentally friendly cement (for example, see Non-Patent Document 1), and opportunities for the use of concrete produced with blast-furnace cement are increasing. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 2019-1694 Patent Document 2 Japanese Unexamined Patent Publication No. 2014-148059 Non-Patent Documents

[0005] Non-Patent Document 1 Toshio Yonezawa, Etsuro Sakai, Kiyoshi Koibuchi, Mitsuo Kinoshita, Hiroomi Kamano; Energy-CO₂ Minimum (ECM) Cement-Concrete System, Concrete Engineering Vol.48, No.9, 2010 [Non-Patent Document 2] Masahiro Wachi, Toshio Yonezawa, Takeo Mitsui, and Kazumasa Inoue; Properties of concrete using high-blast furnace slag content cement, Annual Proceedings of the Concrete Engineering Society, Vol. 32, No. 1, 2010. [Overview of the project] [Problems that the invention aims to solve]

[0006] To construct structures utilizing the properties of blast furnace cement, it is expected that the characteristics of blast furnace cement will be fully realized by using different types of cement: Type C blast furnace cement, which has low heat generation and low CO2 emissions, for piles and foundations; Type A blast furnace cement, which has low carbonation and drying shrinkage, for above-ground structures; and Type B blast furnace cement for intermediate underground structures. However, concrete manufacturing plants typically only stock Type B blast furnace cement, which has a blast furnace slag content adjusted to 40-45%, making it difficult to use Types A and C. Using Type C would require replacing the Type B blast furnace cement silos with Type C silos, incurring additional time and cost. Constructing separate silos for Types A and C would require even greater cost and land.

[0007] Patent Document 1 discloses a technology for producing blast furnace cement type A by mixing blast furnace cement type B and Portland cement stocked in a concrete manufacturing plant, but this technology cannot be used to produce concrete using blast furnace cement type C.

[0008] Patent Document 2, like Patent Document 1, discloses a technology that uses Portland cement and blast furnace cement type B as the base materials, mixing the two to produce blast furnace cement with a lower blast furnace slag content than blast furnace cement type B, and producing blast furnace cement type C, which has a higher blast furnace slag content than blast furnace cement type B, by adding blast furnace slag separately. In other words, blast furnace cement type C cannot be produced without installing equipment to add blast furnace slag separately.

[0009] The weaknesses of blast furnace cement, namely its slow strength development and high degree of carbonation, tend to worsen as the amount of blast furnace slag increases, as disclosed in Non-Patent Document 2. However, these problems can be mitigated by increasing the amount of gypsum in proportion to the amount of slag. However, commercially available blast furnace cement has a constant amount of gypsum regardless of type, making it difficult to meet this requirement. In other words, neither the technology in Patent Document 1 nor the technology in Patent Document 2 can produce blast furnace cement with an optimized amount of gypsum. Therefore, a concrete manufacturing method and apparatus that can address this problem is needed.

[0010] Therefore, the object of the present invention is to provide a concrete manufacturing method and apparatus that enables the production of concrete using blast furnace cement type A, concrete using blast furnace cement type B, and concrete using blast furnace cement type C without increasing the number of cement silos in a concrete manufacturing plant, and that also optimizes the amount of gypsum. [Means for solving the problem]

[0011] To achieve the above objective, according to the present invention, by stocking Portland cement and blast furnace cement type C in a cement silo of a concrete manufacturing plant and adjusting the mixing ratio of these two types of cement, it is possible to set the blast furnace slag content to 6.0% or more (the lower limit for type A) and less than or equal to the slag content of blast furnace cement type C, and a method for producing concrete using blast furnace cement types A, B, and C is provided. In other words, a method for producing concrete using blast furnace cement types A, B, and C is provided by stocking blast furnace cement type C, which has the highest blast furnace slag content, in the silo. As the Portland cement, ordinary Portland cement or high-early-strength Portland cement can be used. Using high-early-strength Portland cement improves the slow strength development of blast furnace cement.

[0012] Traditionally, blast furnace cement has been manufactured in cement plants. However, a method is provided to manufacture it by mixing Portland cement and blast furnace cement type C, which are stored in cement silos at concrete plants. In other words, a method is provided to manufacture blast furnace cement at a concrete plant and simultaneously manufacture concrete using this cement. Furthermore, a manufacturing apparatus suitable for this manufacturing method is also provided.

[0013] The amount of gypsum contained in blast furnace cement can be increased as the amount of blast furnace slag increases, thereby suppressing the weaknesses of blast furnace cement. Therefore, in this invention, blast furnace cement type C, which has a high gypsum content, is stocked in a silo, and blast furnace cement type B and blast furnace cement type A are produced by mixing this with Portland cement. As a result, the amount of gypsum in these cements is reduced according to the amount of blast furnace slag, providing a concrete manufacturing method with an optimized gypsum content. The gypsum content of blast furnace cement type C should be equal to or greater than the gypsum content of Portland cement, and 6.0% or less. If it exceeds 6.0%, side effects such as freeze-thaw resistance may occur. Anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, etc., can be used.

[0014] Furthermore, according to the present invention, a manufacturing apparatus is provided for producing concrete using blast furnace cement by the above manufacturing method. [Effects of the Invention]

[0015] According to the present invention described above, concrete can be produced using blast furnace cement type A, blast furnace cement type B, and blast furnace cement type C by adjusting the mixing ratio of Portland cement and blast furnace cement type C in a concrete manufacturing plant. As a result, the cement plant only needs to produce blast furnace cement type C, and the concrete plant only needs silos for blast furnace cement type C, thus improving the efficiency of cement production and concrete production. [Brief explanation of the drawing]

[0016] [Figure 1]A method for producing concrete according to an embodiment of the present invention is shown. [Figure 2] An apparatus for producing concrete according to an embodiment of the present invention is shown. DETAILED DESCRIPTION OF THE INVENTION )

[0017] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, to clarify the explanation, the following description and drawings are appropriately simplified.

[0018] (Production Method) Fig. 1 shows a method for producing concrete according to an embodiment of the present invention. That is, the method for producing concrete of the present invention comprises three steps: a blast furnace cement production step (A1) for producing a target blast furnace cement by storing Portland cement and blast furnace cement type C in a cement silo of a concrete production plant and adjusting the mixing ratio of the two cements; an aggregate and water metering step (A2) for metering fine and coarse aggregates, water and an admixture; and a concrete mixing step (A3) for obtaining concrete by charging the metered cement, fine and coarse aggregates, water and the admixture into a concrete mixing apparatus and mixing them to obtain concrete.

[0019] Among the above concrete production steps, the blast furnace cement production step comprises: steps (A11, A12) of storing Portland cement and blast furnace cement type C; a step (A13) of setting a mixing ratio of the two cements to determine metered values for producing the target blast furnace cement; and steps (A14, A15) of metering Portland cement and blast furnace cement type C.

[0020] Among the above cement manufacturing steps, a specific method for the step (A13) of setting the measured values of the two cements will be described with practical examples. Table 1 shows the compositional characteristics of the two cements. The Portland cement in the table is ordinary Portland cement, which contains 93.6% of clinker, 3.0% of minor additional components, and 3.4% of anhydrous gypsum (CaSO₄) (2.0% in terms of SO₃). The minor additional components are additives other than clinker permitted by JIS R 5210, and fine limestone powder is used as the minor additional component in this cement. Blast furnace cement type C contains 64.0% of blast furnace slag, 30.0% of clinker, and 6.0% of anhydrous gypsum, with no minor additional component used.

[0021] The blast furnace cements manufactured in this example include four cases: blast furnace cement type A with a blast furnace slag content of 15% and 25%, and blast furnace cement type B with a blast furnace slag content of 43% and 55%. Based on the compositions of Portland cement and blast furnace cement type C shown in Table 1, Table 2 shows the calculated results of the mixing ratios (wt.%) of Portland cement and blast furnace cement type C, the content of minor additional components and the gypsum content for manufacturing these four types of blast furnace cement. As the target blast furnace slag content increases, the mixing ratio of blast furnace cement type C increases, and the gypsum content also increases.

[0022] [Table 1]

[0023] [Table 2]

[0024] The procedure for obtaining the composition of the blast furnace cement in Table 2 based on Table 1 is as follows: First, determine the mixing ratio of the stocked blast furnace cement type C so as to achieve the slag content of the blast furnace cement to be manufactured; second, determine the mixing ratio of Portland cement based on the mixing ratio of blast furnace cement type C; third, determine the content of minor additional components and the gypsum content based on the mixing ratios of Portland cement and blast furnace cement type C.

[0025] Tables 1 and 2 show examples of four types of blast furnace cement obtained by mixing Portland cement and blast furnace cement type C, demonstrating that four more types of blast furnace cement can be produced from blast furnace cement type C stocked in a cement silo. As long as the amount of slag is less than or equal to the amount of blast furnace cement type C stocked in the silo, it is possible to produce blast furnace cement of type A, type B, type C, or any amount of slag, not limited to these four examples. This is an advantage of the present invention compared to producing blast furnace cement in a cement plant. Furthermore, the ability to optimize the amount of gypsum according to the amount of slag is also an advantage of the present invention.

[0026] The aggregate and water weighing process (A2) consists of the process of stocking fine and coarse aggregates (A21), setting the weighing values ​​for fine and coarse aggregates (A23), weighing the fine and coarse aggregates (A25), and the process of stocking water and admixtures (A22), setting the weighing values ​​for water and admixtures (A24), and weighing the water and admixtures (A26).

[0027] The concrete mixing process (A3) involves putting the measured Portland cement, blast furnace cement type C, fine and coarse aggregates, water, and admixtures into a concrete mixing device and mixing them to form concrete.

[0028] (manufacturing equipment) Figure 2 shows an example of a manufacturing apparatus for producing concrete using the manufacturing method described in the above embodiment. This apparatus consists of a cement silo (reference numerals 1 and 2) for producing blast furnace cement, cement storage tanks (reference numerals 3 and 5) and cement measuring devices (reference numerals 4 and 6) that operate in pairs for measuring cement, aggregate storage tanks (reference numerals 7 and 9) and aggregate measuring devices (reference numerals 8 and 10) for measuring fine aggregate and coarse aggregate, a water measuring device (reference numeral 11) for measuring water and an admixture measuring device (reference numeral 12) for measuring admixtures, a concrete mixing apparatus (reference numeral 13) for inputting and mixing cement, fine aggregate, coarse aggregate, water, and admixtures to produce concrete, and a control device (reference numeral 14).

[0029] The cement silo of the above manufacturing apparatus discharges cement from the bottom and puts it into the top of the cement storage tank for temporary storage. The bottom of the storage tank has a function that controls the amount of cement put into the weighing device based on a weighing signal from the control device, and works in conjunction with the cement weighing device to weigh the amount indicated by the control device. The cement weighing device has the cement weighing accuracy (±1%) specified in JIS A5308 "Ready-Mixed Concrete". When one weighing device is installed and Portland cement and blast furnace cement type C are weighed in sequence, the weighing device maintains the weighing accuracy of JIS A5308 even when a small amount of cement is put in. In the weighing process, the cement with the smallest amount is put in first, weighed, and recorded. Next, the other type of cement is put in, and the total amount of cement is weighed and recorded.

[0030] Fine aggregate and coarse aggregate are loaded from the stock silo into the storage tank and weighed in conjunction with a weighing device, according to the value indicated by the control device. The aggregate weighing device has the aggregate weighing accuracy (±3%) specified in JIS A5308 "Ready Mixed Concrete". Water and admixtures are weighed by directly loading them into the weighing device, with a weighing accuracy of ±1% for water and ±3% for admixture solutions. The concrete mixing device (reference numeral 13) is not particularly limited, and can be a forced twin-shaft mixer, pan mixer, tilting drum mixer, etc., as long as it satisfies the performance requirements of JIS A5308.

[0031] The control unit of the manufacturing apparatus shown in Figure 2 has functions for measuring cement, aggregate, water, and admixtures to produce concrete, as well as a control function for adjusting the mixing ratio of Portland cement and blast furnace cement type C to produce concrete using blast furnace cement types A, B, and C.

[0032] Table 3 shows the functions of each block of the control device. The information input to the information input unit includes information on the composition of Portland cement and blast furnace cement type C (Table 1) and the amount of blast furnace slag in the blast furnace cement to be manufactured. The control information instruction unit calculates the mixing ratio of Portland cement and blast furnace cement type C based on the input information, and based on that, calculates the metering values ​​of Portland cement and blast furnace cement type C to obtain the composition of the blast furnace cement to be manufactured (Table 2), sends instruction signals to the cement storage tank and metering device, and measures them. The information recording unit records the instructed information and receives the signal of the metering result, records this information and outputs it to a predetermined location and medium.

[0033] [Table 3] [Explanation of symbols]

[0034] 1 Portland cement silo 2. Blast furnace cement silo (Type C) 3. Portland cement storage tank 4. Portland cement weighing device 5. Blast furnace cement type C storage tank 6. Blast furnace cement type C weighing device 7. Fine aggregate storage tank 8 Fine aggregate measuring device 9. Coarse aggregate storage tank 10 Coarse aggregate measuring device 11 Water metering device 12. Admixture measuring device 13 Concrete mixing equipment 14 Control device A1 Process for manufacturing blast furnace cement A11 Portland cement stocking process A12 Process for stocking blast furnace cement type C A13. Process for setting the mixing ratio and measurement values ​​of Portland cement and blast furnace cement type C. A14 Process for weighing Portland cement A15 Process for weighing blast furnace cement type C A2 Process of weighing aggregate and water A21 Process for stocking fine aggregate and coarse aggregate A22 Process for storing water and admixture A23 Process for setting the weighing values ​​of fine aggregate and coarse aggregate. A24 Steps to set the measurement values ​​for water and admixture. A25 Process for weighing fine aggregate and coarse aggregate A26 Process of measuring water and admixture A3. Process of mixing concrete

Claims

1. A method for producing concrete using blast furnace cement, comprising the steps of: stocking Portland cement in one cement silo and blast furnace cement type C in another silo; adjusting the mixing ratio of Portland cement and blast furnace cement type C so that the blast furnace slag content is less than or equal to the blast furnace slag content of blast furnace cement type C and 6.0% by mass or more of blast furnace cement is obtained; weighing fine aggregate, coarse aggregate, water and admixtures; and putting all the weighed materials into a concrete mixing device and mixing them to produce concrete.

2. In the method for producing concrete using the aforementioned blast furnace cement, the amount of gypsum contained in blast furnace cement type C is SO ３ A method for producing concrete using blast furnace cement, characterized in that, expressed in terms of quantity, the amount of gypsum is equal to or greater than that of Portland cement and 6.0% by mass or less.

3. A method for producing concrete using blast furnace cement, characterized in that the Portland cement in claims 1 and 2 is ordinary Portland cement or high-early-strength Portland cement.

4. A manufacturing apparatus for producing concrete using blast furnace cement by the method described in claims 1 to 3, comprising: two or more cement silos for stocking Portland cement and blast furnace cement type C; two cement metering systems consisting of a storage tank and a metering device for metering these two types of cement; four metering systems for metering fine aggregate, coarse aggregate, water and and admixtures; a concrete mixing apparatus for producing concrete by inputting the six types of materials metered by these metering systems; and a control device for controlling the metering systems and the concrete mixing apparatus.

5. A concrete manufacturing apparatus using blast furnace cement as described in claim 4, characterized in that the cement weighing system comprises a storage tank for Portland cement, a storage tank for blast furnace cement type C, and a single weighing device for weighing these two types of cement in combination.

6. A concrete manufacturing apparatus using blast furnace cement as described in claims 4 and 5, wherein the control device has a function for inputting the compositional composition of Portland cement and blast furnace cement type C and the blast furnace slag content of the blast furnace cement to be manufactured, a function for setting the measurement values ​​of Portland cement and blast furnace cement type C and instructing the measuring device, and a function for recording the measurement results.

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