Method for manufacturing geopolymer concrete

Abstract

To meet the design requirements and specified strength standards within a short period of time. [Solution] The method for producing geopolymer concrete is a method for producing geopolymer concrete using multiple materials including an activated filler, aggregate, and an alkaline solution as raw materials, and includes a mixing and stirring step in which the raw materials are mixed and stirred such that the W / P, which represents the volume ratio of water content to activated filler, is 1.1 or more, and the A / W, which represents the molar ratio of alkaline components to water content, is 0.075 or more.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing geopolymer concrete, and particularly to a method for manufacturing geopolymer concrete that meets the strength of concrete block type C.

Background Art

[0002] When manufacturing concrete blocks with geopolymer using active fillers, aggregates, and an alkaline solution as raw materials, it is common to mix them according to the mixing ratio indicated by the Japan Society of Civil Engineers. Also, regarding the method of curing concrete, it is common to use the method (high temperature and high humidity) indicated by the Japan Society of Civil Engineers.

[0003] Regarding cement concrete, methods for manufacturing concrete that exhibits early strength after placement have been proposed in the past (Japanese Patent Application Laid-Open No. 2001-62823 (Patent Document 1)). However, a manufacturing method for early satisfying the strength of building concrete block type C using geopolymer has not been clarified. The strength of type C is the compressive strength of 16 N / mm required for the outer block wall. 2 It is.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to improve productivity, manufacturing technology for geopolymer concrete (concrete blocks using geopolymer) is required in factories. Since geopolymer concrete used for outer structures etc. also requires good appearance, it must satisfy the designability and specified (type C) strength at an early stage.

[0006] The present invention was made to solve the above-mentioned problems, and its objective is to provide a method for manufacturing geopolymer concrete that can satisfy design requirements and specified strength in a short period of time. [Means for solving the problem]

[0007] A method for producing geopolymer concrete according to a certain aspect of this invention is a method for producing geopolymer concrete using multiple materials, including an activated filler, aggregate, and an alkaline solution, as raw materials, and includes a mixing and stirring step of mixing the raw materials such that the W / P, which represents the volume ratio of water content to activated filler, is 1.1 or more, and the A / W, which represents the molar ratio of alkaline components to water content, is 0.075 or more.

[0008] Preferably, W / P is 1.1 or greater and 1.5 or less.

[0009] Preferably, A / W is 0.075 or higher and 0.100 or lower.

[0010] The mixing and stirring process preferably includes the steps of: stirring fine aggregate, fly ash, and blast furnace slag to produce primary materials; adjusting the concentration of the alkaline solution so that the W / P ratio is 1.1 or higher and the A / W ratio is 0.075 or higher; mixing the concentration-adjusted alkaline solution with the primary materials to produce secondary materials; and mixing gravel with the secondary materials to produce a geopolymer paste.

[0011] Preferably, the process further includes the steps of: pouring the geopolymer paste generated in the mixing and stirring process into a mold and molding it; initially curing the geopolymer paste in the mold in a curing chamber adjusted to a temperature of 30°C or higher and 50°C or lower; and curing the demolded geopolymer concrete for a predetermined period of time. [Effects of the Invention]

[0012] According to the present invention, aesthetic appeal and specified strength can be achieved in a short period of time. [Brief explanation of the drawing]

[0013] [Figure 1] This flowchart shows a method for producing geopolymer concrete according to an embodiment of the present invention. [Figure 2] This flowchart shows the specific steps to be taken in the mixing and stirring process shown in Figure 1. [Figure 3] This figure shows comparative examples and photographs of the test specimens in the experiment. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0015] <Method for manufacturing geopolymer concrete> The method for producing geopolymer concrete will be explained with reference to Figure 1.

[0016] Geopolymer concrete is manufactured by sequentially going through the following steps: mixing and stirring process P1, molding and shaping process P2, initial curing process P3, demolding process P4, and curing process P5.

[0017] (Mixing and stirring process) In the compounding and stirring process P1, a geopolymer paste is produced by compounding and mixing multiple materials, including activated fillers, aggregates, and an alkaline solution.

[0018] The activated filler includes fly ash and blast furnace slag fine powder. In this embodiment, it includes only fly ash and blast furnace slag fine powder. The aggregate includes fine aggregate (river sand) and coarse aggregate (crushed stone). In this embodiment, it includes only fine aggregate and coarse aggregate. The alkaline solution includes water glass, caustic soda, and water (tap water). In this embodiment, it includes only water glass, caustic soda, and water.

[0019] In the mixing and stirring step P1, each material is prepared and mixed so that the W / P is 1.1 or more and the A / W is 0.075 or more. "W / P" is an index representing the volume ratio of the amount of moisture to the active filler. "A / W" is an index representing the molar ratio of the alkaline component to the amount of moisture. The amount of moisture is the mass obtained by adding water and the moisture contained in water glass and caustic soda.

[0020] The specific execution procedure of the mixing and stirring step P1 will be described using FIG. 2. FIG. 2 is a flowchart showing the production procedure of the geopolimer paste in the present embodiment.

[0021] First, fine aggregate, fly ash, and blast furnace slag are put into a mixer and stirred at a low speed for 2 minutes (step P11). In this way, a primary material (solid) composed of fine aggregate, fly ash, and blast furnace slag is produced.

[0022] Next, the concentration of the alkaline solution is adjusted (step P12), and the adjusted alkaline solution is put into the primary material and stirred (step P13). In this way, a paste-like secondary material is produced. At this time, for example, after stirring at a low speed for 30 seconds, it is stirred at a high speed for 2 minutes. The method of adjusting the concentration will be described later.

[0023] When it is confirmed that the secondary material is sufficiently mixed, gravel is put into the secondary material and kneaded by hand (step P14). In this way, the geopolimer paste (final material) is produced.

[0024] (Molding and shaping step) In the molding and shaping step P2, the geopolimer paste produced in the mixing step is poured into a mold. At this time, it is desirable to perform shaping while applying vibration to the geopolimer paste by vibration means such as a table vibrator.

[0025] (Initial curing step) The initial curing process P3 is performed immediately after the molding process P2. In this process P3, the geopolymer paste filled into the mold is cured for a predetermined time in a "curing room" at, for example, 40 degrees Celsius. At this time, it is desirable to cover the top surface of the geopolymer paste with plastic wrap to prevent drying shrinkage. In this embodiment, the initial curing is performed for 6 hours to dry the geopolymer paste. The initial curing environment in the curing room will be described later.

[0026] (Demolding process) The demolding process P4 is performed after the initial curing process P3 to demold the solidified geopolymer concrete.

[0027] (Curing process) In curing process P5, the geopolymer concrete is air-cured for a specified period under standard temperature and humidity conditions as defined by JIS, etc. Curing after demolding is carried out, for example, under a temperature and humidity environment of 23±2℃ and relative humidity of 50±5%.

[0028] The standard curing period under typical temperature and humidity conditions is usually 28 days. However, considering the factory production cycle, it is desirable to achieve the required strength in 7 days. Therefore, it is desirable to achieve both aesthetic appeal and the specified compressive strength (16 N / mm²) in 7 days of curing. 2 We explored the optimal material composition ratios that would allow for both of the following conditions to be met. The outline and results of the experiment are described below.

[0029] <About the experiment> Multiple test specimens were produced using a common manufacturing procedure for geopolymer concrete (manufactured according to the procedure described above), while varying the concentration of the alkaline solution. In the experiment, the aesthetic appearance and compressive strength of each test specimen were measured after 7 days of curing. The compressive strength test method used was the one specified in JIS standards (JIS A 1108 or JIS A 1132). The dimensions of the test specimens were cylinders with a diameter of 100 mm and a height of 200 mm.

[0030] (Comparative example) First, the amount (g) of each geopolymer material used was determined based on the "GP-C1" (or "GP-C2") formulation shown in "Concrete Technology Series No. 132, Report of the Research Subcommittee (Committee 361) for Promoting the Practical Application of Geopolymer Technology in the Civil Engineering Field" (published December 14, 2022) by the Japan Society of Civil Engineers. Tests were then conducted to evaluate the compressive strength and appearance of the hardened geopolymer after 7 days of curing.

[0031] Table 1 shows the amount of each material used. In addition to the materials shown in Table 1, a small amount of admixture (retardant) is also included. In this case, the geopolymer consists of fly ash, blast furnace slag powder, fine aggregate, coarse aggregate, water glass, caustic soda, water, and admixture.

[0032] [Table 1]

[0033] Table 2 shows the characteristic values ​​and test results based on the basic formulation. The characteristic values ​​include moisture content, W / P, A / W, and Si / A. "Si / A" is an index representing the molar ratio of silicon to alkali components.

[0034] [Table 2]

[0035] As can be seen from Table 2, the comparative specimen, even with a curing period of 7 days, exceeded the compressive strength of Class C and passed the test. However, it failed the test due to the appearance, as many air bubbles remained on the surface (see Figure 3).

[0036] To suppress air bubble marks, increasing the water content to improve fluidity is considered effective. In other words, lowering the alkali concentration compared to the comparative example is considered effective. Therefore, while keeping the amounts of fly ash, blast furnace slag, fine aggregate, water glass, and caustic soda fixed, multiple experiments were conducted while varying the amounts of coarse aggregate and water so that the overall weight remained approximately constant.

[0037] Table 3 shows the formulations for each of the five test specimens, and Table 4 shows the characteristic values ​​and test results for each specimen. In Table 3, items with varying quantities (amounts of coarse aggregate and water) are enclosed in a thick border for easier understanding, and in Table 4, columns where the test result was satisfactory are enclosed in a thick border.

[0038] [Table 3]

[0039] [Table 4]

[0040] The moisture content of test specimen (1) is higher than that of the comparative example, but it is the lowest among the five. The moisture content of test specimens (1) to (5) is in ascending order, with test specimen (5) having the highest moisture content among the five. Therefore, the W / P ratio is highest for test specimen (5), and the A / W ratio is highest for test specimen (1). The Si / A ratio is constant for all test specimens.

[0041] In test specimen (1), although the moisture content was increased compared to the comparative example, separation occurred, resulting in a failure in both appearance and compressive strength. In test specimens (2) and (3), as shown in Figure 3, the appearance was good, and the compressive strength was above the specified value. In test specimens (4) and (5), as shown in Figure 3, the appearance was also good, but the compressive strength fell below the specified value. In particular, in test specimen (5), the moisture content was too high, and it did not fully harden even after 7 days of curing. Note that the numerical values ​​shown in some of the photographs in Figure 3 are values ​​for coarse aggregate recorded for the purpose of identifying the test specimens and are unrelated to the test results.

[0042] Only specimens (2) and (3) passed both the appearance and compressive strength tests. From the W / P and A / W of these passing specimens (2) and (3), it was found that if the mixture is formulated so that W / P is 1.139 or higher and A / W is 0.077 or higher, the aesthetic appearance and specified strength can be met after 7 days of curing.

[0043] From the above experimental results, the following can be inferred: Considering the W / P ratio of the successful test specimen (2) and the previous unsuccessful test specimen (1), aiming for a W / P ratio of 1.1 or higher will result in a better appearance. Furthermore, considering the value of the unsuccessful test specimen (5), the upper limit of the target W / P ratio may be set at 1.5.

[0044] Furthermore, considering the A / W ratio of the passing test specimen (3) and the subsequent failing test specimen (4), the specified compressive strength can be obtained by targeting an A / W ratio of 0.075 or higher. It is also possible to set the target upper limit of A / W to 0.100, taking into account the value of the failing test specimen (1).

[0045] As described above in the explanation of the mixing and stirring process P1, by mixing the raw materials so that the W / P ratio is 1.1 or higher and the A / W ratio is 0.075 or higher, it is possible to satisfy the aesthetic requirements and specified strength after 7 days of curing. In other words, by adjusting the concentration of the alkaline solution in the concentration adjustment process P12 so that the W / P and A / W ratios fall within the above ranges, it is possible to efficiently produce geopolymer concrete for exterior use in a factory.

[0046] <Regarding the initial curing environment> For the initial curing environment, the environment (curing room) described in the patent application specification (Japanese Patent Application No. 2024-039758) filed by the present applicant can be adopted.

[0047] In the initial curing process P3, the curing chamber for initial curing of the geopolymer paste is equipped with a temperature control means to adjust the room temperature to 30 degrees Celsius or higher and 50 degrees Celsius or lower. The curing chamber does not need to be equipped with a humidity control means. It is assumed that the relative humidity of a curing chamber without a humidity control means will be around 20% to 85%. In another embodiment, the curing chamber may be equipped with a humidity control means to adjust the relative humidity of the curing chamber to 20% to 85%.

[0048] By implementing the initial curing process P3 using such a curing room, it is not necessary to require special equipment to create a high-temperature, high-humidity initial curing environment, thus enabling the low-cost and simple production of geopolymer concrete. Furthermore, since the geopolymer paste is initially cured (dried) in a curing room with controlled room temperature, it is possible to obtain consistent strength and hardness regardless of the outside temperature.

[0049] Furthermore, while it is recommended that the curing time be 12 hours or more when the curing environment is high temperature and high humidity, using a curing room can shorten the initial curing time to 6 hours. The initial curing time may be set within the range of 6 hours to 8 hours.

[0050] Furthermore, since the temperature range of the curing room can be set to a medium temperature range, it is possible to use a space that is simply partitioned off with walls within a factory as a curing room. Such a curing room can be realized, for example, by a room (or chamber) that has an entrance that workers can enter and exit, and is surrounded by walls. Alternatively, the curing room may be realized by a dryer that can accommodate multiple formwork.

[0051] <Variation> In this embodiment, the curing period in curing process P5 is set to 7 days (1 week), but it is not limited to this, and may be, for example, 14 days (2 weeks). Considering productivity, the curing period should be 3 weeks or less, and preferably 2 weeks or less.

[0052] Furthermore, while we have described an example of using a curing room with a temperature adjusted to 30°C or higher and 50°C or lower during initial curing, this is not limited to that; for example, initial curing may be performed in a temperature environment below 30°C.

[0053] In the experiments described above, the Si / A ratio was 0.365 in all cases. However, it is likely that similar results would have been obtained if the Si / A ratio was in the range of 0.300 to 0.400.

[0054] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

Claims

1. A method for producing geopolymer concrete using multiple materials, including activated filler, aggregate, and an alkaline solution, as raw materials, A method for producing geopolymer concrete, comprising a mixing and stirring step of mixing and stirring raw materials such that the W / P, which represents the volume ratio of water content to active filler, is 1.1 or higher, and the A / W, which represents the molar ratio of alkaline components to water content, is 0.075 or higher.

2. The method for producing geopolymer concrete according to claim 1, wherein the W / P ratio is 1.1 or greater and 1.5 or less.

3. The method for producing geopolymer concrete according to claim 1, wherein the A / W ratio is 0.075 or more and 0.100 or less.

4. The aforementioned blending and stirring process is as follows: A method for producing geopolymer concrete according to claim 1, comprising the steps of: stirring fine aggregate, fly ash, and blast furnace slag to produce a primary material; adjusting the concentration of an alkaline solution so that the W / P ratio is 1.1 or higher and the A / W ratio is 0.075 or higher; mixing the concentration-adjusted alkaline solution with the primary material to produce a secondary material; and mixing gravel with the secondary material to produce a geopolymer paste.

5. The process involves pouring the geopolymer paste generated in the aforementioned mixing and stirring process into a mold and molding it, The process involves initially curing the geopolymer paste in the mold in a curing chamber where the temperature is adjusted to 30°C or higher and 50°C or lower. A method for producing geopolymer concrete according to claim 1, further comprising the step of curing the demolded geopolymer concrete for a predetermined period of time.

6. Geopolymer concrete produced by the method for producing geopolymer concrete described in any one of claims 1 to 5.

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