Manufacturing method of high thermal conductivity concrete

Abstract

The present invention provides a method for producing high thermal conductivity concrete that can be manufactured efficiently and inexpensively even in the vicinity of a ready-mix concrete plant that does not have silos for aggregates using aluminum oxide (hereinafter referred to as "alumina") (hereinafter referred to as "alumina aggregate"). [Solution] A method for producing high thermal conductivity concrete, comprising: preparing concrete without alumina aggregate (hereinafter referred to as "base concrete for high thermal conductivity concrete") at a ready-mix concrete plant; then, placing this base concrete for high thermal conductivity concrete into a drum of an agitator truck; moving the agitator truck to the pouring site; and finally, at the pouring site, adding alumina aggregate to the drum of the agitator truck and mixing the base concrete for high thermal conductivity concrete with the alumina aggregate to produce high thermal conductivity concrete that can be used for applications such as paving concrete for waterless snow melting facilities.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing high thermal conductivity concrete.

Background Art

[0002] High thermal conductivity concrete is a new technology registered in a database for sharing and providing information on new technologies operated by the Ministry of Land, Infrastructure, Transport and Tourism in October 2023 (registration number: HR-230007-A). It is a technology developed by the present inventor that improves the thermal conductivity of concrete by using an aggregate using aluminum oxide (hereinafter referred to as "alumina") (hereinafter referred to as "alumina aggregate"), and controls the thermal conductivity according to the amount of alumina aggregate.

[0003] The applicable uses of high thermal conductivity concrete are limited because the price of alumina aggregate is more than two digits higher than that of ordinary aggregate. For this reason, there is still no demand for high thermal conductivity concrete, and accordingly, since there is no dedicated silo for storing alumina aggregate, which is a material for high thermal conductivity concrete, in existing ready-mixed concrete plants, it cannot be manufactured.

[0004] As a method for manufacturing high thermal conductivity concrete using alumina aggregate, the present inventor has a record of manufacturing high thermal conductivity concrete by a preparation process in which cement milk, ordinary aggregate, alumina aggregate, and admixture are put into a portable tilting drum type concrete mixer (0.12 m , , , , , , , capacity) at the placement site, mixed, and high thermal conductivity concrete is obtained.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The manufacturing method used by the inventors described above in the adjustment process for obtaining high thermal conductivity concrete has low manufacturing capacity and high manufacturing costs, which are expected to hinder the widespread adoption of high thermal conductivity concrete. The objective of the present invention is to provide a method for producing high thermal conductivity concrete that can be manufactured efficiently and inexpensively even in the vicinity of a ready-mix concrete plant that does not have alumina aggregate silos. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors of the present invention have found that by preparing concrete without alumina aggregate (hereinafter referred to as "base concrete for high thermal conductivity concrete") at a ready-mix concrete plant, then placing this base concrete for high thermal conductivity concrete into the drum of an agitator truck, moving the agitator truck to the concrete placement site, and finally, adding alumina aggregate to the drum of the agitator truck at the concrete placement site and mixing the base concrete for high thermal conductivity concrete with the alumina aggregate, high thermal conductivity concrete that can be used at least for paving materials for waterless snow melting facilities can be obtained, and thus the present invention has been completed.

[0008] The present invention provides the following [1] to [6]. [1] A method for manufacturing high thermal conductivity concrete, comprising: a base concrete preparation step for preparing high thermal conductivity concrete at a ready-mix concrete plant; a base concrete transport step for transporting high thermal conductivity concrete, in which the base concrete for high thermal conductivity concrete is placed in the drum of an agitator truck and then the agitator truck is moved to a concrete placement site; and a concrete preparation step for mixing the base concrete for high thermal conductivity concrete and the alumina aggregate at the concrete placement site, wherein in the concrete preparation step, fine aggregate is used preferentially over coarse aggregate. [2] The method for manufacturing high thermal conductivity concrete according to [1] above, wherein the amount of high thermal conductivity concrete produced in the concrete preparation step is preferably within one-quarter of the capacity of the drum per agitator vehicle. [3] The method for producing high thermal conductivity concrete according to 1 or 2 above, wherein the time from the start of adding the alumina aggregate to the completion of preparing the high thermal conductivity concrete in the concrete preparation step is 9 minutes or more. [4] A method for producing high thermal conductivity concrete according to any of [1] to [3] above, wherein, in the concrete preparation step, a cement admixture is added to the drum before, during, or after the addition of the alumina aggregate. [5] A method for producing a hardened high-thermal-conductivity concrete, characterized in that, after obtaining the high-thermal-conductivity concrete by the method for producing high-thermal-conductivity concrete described in any of [1] to [4] above, the high-thermal-conductivity concrete is poured into the pouring site to form a hardened high-thermal-conductivity concrete body. [6] The method for manufacturing a hardened high-thermal-conductivity concrete according to [5], wherein the time from the completion of the loading of the high-thermal-conductivity base concrete into the drum in the high-thermal-conductivity base concrete transport process to the completion of the pouring of the high-thermal-conductivity concrete at the pouring site is within 90 minutes. [Effects of the Invention]

[0009] According to the method for producing high thermal conductivity concrete of the present invention, since alumina aggregate is used at the concrete placement site rather than at the ready-mix concrete plant, high thermal conductivity concrete can be produced even in the vicinity of a ready-mix concrete plant that does not have alumina aggregate silos. [Modes for carrying out the invention]

[0010] The present invention provides a method for producing high thermal conductivity concrete, comprising: (A) a base concrete preparation step for high thermal conductivity concrete, in which base concrete for high thermal conductivity concrete is prepared at a ready-mix concrete plant; (B) a base concrete transport step for high thermal conductivity concrete, in which the base concrete for high thermal conductivity concrete is placed in the drum (sometimes referred to as a "mixing drum") of an agitator truck (sometimes referred to as an "agitator truck," "ready-mix concrete truck," etc.), and then the agitator truck is moved to the concrete placement site; and (C) a concrete preparation step for which alumina aggregate is placed in the drum of the agitator truck at the concrete placement site, and the base concrete for high thermal conductivity concrete and the alumina aggregate are mixed to obtain high thermal conductivity concrete. The following explains each step of the process.

[0011] [(A) Preparation process for base concrete for high thermal conductivity concrete] Process (A) is the process of preparing base concrete for high thermal conductivity concrete at a ready-mix concrete plant. Examples of materials for base concrete used in high-thermal-conductivity concrete include cement, water, aggregate, and admixtures. Examples of cement include various types of Portland cement, such as ordinary Portland cement and high-early-strength Portland cement.

[0012] For the water used, one that conforms to "JIS A 5308:2024 (Ready-Mixed Concrete)" can be used. The amount of water can be determined to obtain the desired compressive strength and fluidity of the concrete.

[0013] The aggregate does not contain alumina aggregate. By adjusting the amount of aggregate, material segregation can be effectively suppressed and the necessary fluidity can be obtained.

[0014] As for admixtures, those conforming to "JIS A 6204:2011 (Chemical admixtures for concrete)" can be used.

[0015] There are no particular limitations on the method for preparing base concrete for high thermal conductivity concrete, but examples include a method of mixing all the materials constituting the base concrete for high thermal conductivity concrete together, or a method of mixing cement and aggregates other than alumina aggregate to obtain a solid mixture, and then mixing the solid mixture with water and admixtures. The mixing equipment used when preparing base concrete for high thermal conductivity concrete is not particularly limited, but examples include conventional mixers such as omni mixers, pan mixers, twin-shaft mixers, and tilting drum mixers.

[0016] [(B) Base concrete transportation process for high thermal conductivity concrete] Step (B) involves placing the base concrete for high thermal conductivity concrete obtained in step (A) into the drum of the agitator truck, and then moving the agitator truck to the concrete pouring site. The method of housing the base concrete for high thermal conductivity concrete in the drum of an agitator truck is the same as the existing method of housing ready-mixed concrete (concrete that can be used directly at the pouring site) in the drum of an agitator truck. The travel time of the agitator truck to the concrete placement site (the time required from the completion of pouring the base concrete for high thermal conductivity concrete into the drum until the agitator truck arrives at the concrete placement site) is preferably within 70 minutes, more preferably within 60 minutes, considering the time required for pouring and mixing the alumina aggregate into the drum after arriving at the concrete placement site.

[0017] [(C) Concrete preparation process] Process (C) is a process of charging alumina aggregate into the drum of an agitator truck at the placement site, mixing the base concrete for high thermal conductivity concrete and the alumina aggregate, and obtaining high thermal conductivity concrete. In process (C), it is preferable to use the fine aggregate in preference to the coarse aggregate for the above-mentioned alumina aggregate to be used.

[0018] In process (C), the timing of adding the cement admixture is before, during, or after the addition of the alumina aggregate. The fact that this timing is before the addition of the alumina aggregate is preferable in that the action and effect of the cement admixture appear early.

[0019] Examples of the cement admixture include AE water reducing agent, AE agent, high performance AE water reducing agent, air content regulator, etc. These cement admixtures may be used alone or in combination of two or more. When using an AE water reducing agent, the amount of the AE water reducing agent is preferably 0.5 to 3 parts by mass with respect to 100 parts by mass of cement from the viewpoint of obtaining appropriate air entrainment and appropriate water reducing effect.

[0020] In process (C), from the viewpoint of more uniformly distributing the alumina aggregate in the base concrete for high thermal conductivity concrete, the rotation speed of the drum is maximally increased, and after charging an amount equivalent to half of the alumina aggregate, it is stirred for 3 minutes or more for mixing, then the remaining alumina aggregate is charged, and after similarly stirring for 3 minutes or more, it is preferable to gently rotate the drum for 3 minutes or more to discharge the entrapped air.

[0021] [Manufacture of high thermal conductivity concrete hardened body] In the present invention, the high thermal conductivity concrete prepared in the drum of the agitator truck becomes a high thermal conductivity concrete hardened body by being placed at the placement site. In this specification, the term "placement site" encompasses both the location where alumina aggregate is loaded into the drum of the agitator truck (for example, a parking-friendly road near the concrete pavement placement site) and the location where the high-thermal-conductivity concrete is actually placed (for example, the concrete pavement placement site for a waterless snow melting facility in civil engineering works). In other words, the term "placement site" encompasses both the parking location of the agitator truck parked for the placement of high-thermal-conductivity concrete and the location where the high-thermal-conductivity concrete is supplied from the agitator truck and a hardened high-thermal-conductivity concrete body is formed.

[0022] The time from the completion of loading the base concrete for high thermal conductivity concrete into the drum of the agitator truck in process (B) (base concrete transport process for high thermal conductivity concrete) to the completion of pouring the high thermal conductivity concrete at the pouring site is preferably within 90 minutes.

[0023] In this invention, the physical properties of high thermal conductivity concrete are as follows: The slump of high thermal conductivity concrete is preferably 5.5 cm or more and 20.5 cm or less, as the value obtained immediately after preparation of the high thermal conductivity concrete (immediately after the completion of adding alumina aggregate), using the slump measurement method described in "JIS A 1101:2020 (Slump Test Method for Concrete)".

[0024] The thermal conductivity of high-thermal-conductivity concrete can be reduced to 6 W / m·k or less, depending on the amount of alumina aggregate added, as measured 28 days or more after the completion of the concrete's preparation (when the alumina aggregate is added). The thermal conductivity of typical concrete is generally considered to be 1.6 W / m·k.

[0025] The compressive strength of high thermal conductivity concrete shall be equal to or greater than the design standard strength, as measured 28 days after the completion of preparation of the high thermal conductivity concrete (the completion of the addition of alumina aggregate) (28 days of age), according to the method described in "JIS A 1108:2018 (Test Method for Compressive Strength of Concrete)".

[0026] The high thermal conductivity concrete of the present invention can be used for applications such as paving concrete for waterless snow melting facilities in civil engineering works. [Examples]

[0027] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. [Materials used] (a) Cement (ordinary Portland cement; density: 3.16 g / cm³; manufactured by Taiheiyo Cement Corporation) (b) Coarse aggregate (gravel; sandstone; surface dry density: 2.61 g / cm3; product name: from the Agano River system, Niigata Prefecture) (c) Alumina aggregate (alumina; surface-dry density: 3.98 g / cm³; product name: Nikkei Random G1 1F; manufactured by Nippon Light Metal Co., Ltd.) (e) AE water-reducing agent (product name: Master Leosure 090; manufactured by Pozzolith Solutions Co., Ltd.) (f) Air volume regulator (product name: DF753; manufactured by Frolic Co., Ltd.) (g) Water (supernatant water) [Examples]

[0028] At the ready-mix concrete plant, the cement, coarse aggregate, water, and AE water-reducing agent shown in Table 1 were added together to a twin-shaft mixer and mixed for 1 minute to prepare a base concrete for high thermal conductivity concrete. After supplying the obtained high-thermal-conductivity base concrete into the drum of the agitator truck, the drum was rotated slowly for 45 minutes while the agitator truck was driven to the concrete pouring site. Next, the rotation speed of the agitator drum was increased to the maximum, an appropriate amount of air volume regulator was added, and half of the alumina aggregate shown in Table 1 was added, followed by stirring for 3 minutes to mix. Next, the remaining alumina aggregate was added and stirred for 3 minutes to mix it similarly, and then the drum was slowly rotated for 3 minutes to expel any trapped air to obtain high thermal conductivity concrete.

[0029] [Table 1]

[0030] To verify the mixing performance, the following tests were conducted using "JIS A 8603-2:2010 (Method for testing mixing performance)," which is applicable to mixers in ready-mix concrete plants, and the results were compared with the requirements of the same standard. The tests involved collecting specimens from the concrete discharged from the agitator truck at three points: the beginning, middle, and end. The uniformity of the specimens and the compressive strength of the high-thermal-conductivity concrete 28 days after its manufacture were assessed. Concrete uniformity was tested by measuring the amount of mortar and coarse aggregate in the concrete. Compressive strength was measured in accordance with JIS A 1108:2018 (Test method for compressive strength of concrete). Furthermore, to confirm the uniformity of the alumina aggregate, an additional test was conducted to measure the thermal conductivity of high-thermal-conductivity concrete. Table 2 shows the results of compressive strength and thermal conductivity measurements, and Table 3 shows the relationship with the standard values ​​of "JIS A 8603-2:2010 (Method for testing mixing performance)".

[0031] [Table 2]

[0032] [Table 3]

[0033] Tables 2 and 3 show that the high thermal conductivity concrete produced by the present invention satisfies the requirements for strength (compressive strength), thermal conductivity (thermal conductivity), and uniformity (deviation ratio between the amount of mortar and coarse aggregate in the concrete), even though the method involves adding and mixing alumina aggregate at the placement site. Therefore, this manufacturing method yields excellent results as a method for producing high thermal conductivity concrete.

Claims

1. A method for manufacturing high thermal conductivity concrete, comprising: a high thermal conductivity base concrete preparation step of preparing concrete that does not contain aggregate using aluminum oxide (hereinafter referred to as "alumina aggregate") (hereinafter referred to as "base concrete for high thermal conductivity concrete") at a ready-mix concrete plant; a high thermal conductivity base concrete transport step of transporting the agitator truck after placing the base concrete for high thermal conductivity concrete in the drum of the agitator truck and then moving the agitator truck to the pouring site; and a concrete preparation step of putting alumina aggregate into the drum of the agitator truck at the pouring site and mixing the base concrete for high thermal conductivity concrete and the alumina aggregate to obtain high thermal conductivity concrete, wherein in the concrete preparation step, fine aggregate is used preferentially over coarse aggregate.

2. The method for manufacturing high thermal conductivity concrete according to claim 1, wherein, in the concrete preparation step described above, the amount of high thermal conductivity concrete produced per agitator vehicle is preferably within one-quarter of the capacity of the drum.

3. A method for producing high thermal conductivity concrete according to claim 1 or 2, wherein the time from the start of adding the alumina aggregate to the completion of preparing the high thermal conductivity concrete in the concrete preparation step is 9 minutes or more.

4. A method for producing high thermal conductivity concrete according to claim 1, 2, or 3, wherein, in the concrete preparation step described above, a cement admixture is added to the drum before, during, or after the addition of the alumina aggregate.

5. A method for producing a hardened high-thermal-conductivity concrete, characterized in that, after obtaining the high-thermal-conductivity concrete by the method for producing high-thermal-conductivity concrete described in any one of claims 1 to 4, the high-thermal-conductivity concrete is poured into the pouring site to form a hardened high-thermal-conductivity concrete body.

6. The method for manufacturing a hardened high-thermal-conductivity concrete according to claim 5, wherein the time from the completion of loading the base concrete for high-thermal-conductivity concrete into the drum in the above-mentioned transport process for the base concrete for high-thermal-conductivity concrete to the completion of pouring the high-thermal-conductivity concrete at the pouring site is within 90 minutes.

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