Geopolymer composition and mortar hardened body

Abstract

To provide a geopolymer composition further reducing the environmental load.SOLUTION: The geopolymer composition according to one embodiment of the present invention, includes an active filler at least including fly ash and blast furnace fine powder, an alkali solution, and fine aggregate including sand and chaff charcoal, with the content of the chaff charcoal being more than 0% and 10% or less relative to the total weight of the fine aggregate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a geopolymer composition and a hardened mortar. [Background technology]

[0002] As part of efforts to combat global warming, geopolymer compositions have become known as solidified bodies that do not use cement, which emits large amounts of carbon dioxide during its production. For example, Patent Document 1 discloses a geopolymer hydraulic composition that uses rice husk incineration ash as an alumina-silica fine powder (i.e., an active filler). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-184241 Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Document 1 uses rice husk incineration ash as an activated filler, but since this is merely ash, its main component is thought to be silica, and since the amount blended is small, the amount of carbon dioxide fixed is small, so there is room for improvement as a method for fixing carbon dioxide as a measure against global warming.

[0005] In contrast, the present invention provides a geopolymer composition that stores a large amount of carbon within the solidified body, further reducing the environmental burden. [Means for solving the problem]

[0006] One aspect of the present disclosure provides a geopolymer composition comprising an active filler containing at least fly ash and ground granulated blast furnace slag, an alkaline solution, and fine aggregate containing sand and rice husk charcoal, wherein the content of the rice husk charcoal is greater than 0% and less than 10% by weight of the fine aggregate.

[0007] The content of the ground granulated blast furnace slag may be 10% or more based on the total volume of the active filler.

[0008] The content of the rice husk charcoal may be more than 0% and 5% or less based on the total weight of the fine aggregate.

[0009] The content of the ground granulated blast furnace slag may be 20% or more based on the total volume of the active filler.

[0010] The content of the rice husk charcoal may be more than 0% and 7% or less based on the total weight of the fine aggregate.

[0011] The content of the ground granulated blast furnace slag may be 30% or more based on the total volume of the active filler.

[0012] The geopolymer composition may include water glass.

[0013] The alkaline solution may be a NaOH solution.

[0014] Another aspect of the present disclosure provides a hardened geopolymer obtained by hardening any of the geopolymer compositions described above.

[0015] This hardened geopolymer has a compressive strength of 18N / mm 2 It may be more than that. [Effects of the Invention]

[0016] According to the present invention, a geopolymer composition that further reduces the environmental load is provided. [Brief explanation of the drawings]

[0017] [Figure 1] A graph showing the comparison of carbon dioxide fixation effects. [Figure 2] FIG. 1 shows the carbon dioxide emissions of compositions 2 to 4. [Figure 3] 10 is a diagram showing the results of a compressive strength test. [Figure 4] 10 is a diagram showing the results of a compressive strength test. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1. Overview One embodiment of a geopolymer composition includes an active filler, an alkaline solution, and fine aggregate. The geopolymer composition is a hydraulic composition that replaces cement. The geopolymer composition contains an active filler and an alkaline solution instead of cement (limestone). The geopolymer composition is expected to be a substitute for cement compositions. This is because cement production consumes large amounts of fossil fuels when burning limestone, and carbon dioxide is generated during the thermal decomposition of limestone, resulting in the generation of a large amount of carbon dioxide overall. Because the geopolymer composition does not use limestone, it is expected to be a material that can reduce carbon dioxide generation compared to cement compositions.

[0019] Generally, geopolymer compositions are hardened by an amorphous polymer formed by the reaction of an activated filler with an alkaline solution. The activated filler is an alumina-silica powder, and in this example, it contains at least fly ash and ground granulated blast furnace slag. Fly ash is a spherical, fine particle of ash produced during combustion in thermal power plants, blown up with the combustion gases. Fly ash is primarily composed of oxides such as alumina and silica. Ground granulated blast furnace slag is a powdered material obtained by pulverizing blast furnace slag generated during steel production. Ground granulated blast furnace slag is a by-product formed when impurities separate and solidify during the melting of iron ore at high temperatures, and is primarily composed of oxides such as alumina and silica contained in the ore.

[0020] The alkaline solution is an alkaline solution that reacts with the active filler, and in this example, it contains sodium hydroxide (NaOH) and water glass. Water glass is a concentrated aqueous solution of sodium silicate. The reaction mechanism is thought to vary depending on the specific combination of active filler and alkaline solution, but as an example, the following reaction occurs: When an alkaline solution is added to the active filler to create a highly alkaline state, aluminum ions and silicate ions are dissolved from the active filler. The dissolved silicon ions react with hydroxide ions separated from the alkaline solution to form a silicate complex, and the aluminum ions crosslink the silicate complex to form a polymer.

[0021] In this way, no carbon dioxide is emitted during the geopolymer synthesis process. Furthermore, the reaction temperature generally only needs to be around 80°C, which is much lower than the high temperatures of 900-1500°C required for cement to harden. For these reasons, it is said that geopolymer compositions can reduce carbon dioxide emissions by more than 70% compared to cement compositions.

[0022] The fine aggregate according to this embodiment includes sand and charcoal-smoked rice husks. In other words, the content of charcoal-smoked rice husks in the fine aggregate exceeds 0 wt%. Rice husk charcoal is produced by carbonizing rice husks by burning them at a controlled temperature of 400-500°C. It contains little tar and moisture and is primarily composed of silica and carbon. Rice is Japan's staple food, and the annual production of rice husks, a by-product, reaches approximately 2 million tons. Carbon from carbon dioxide absorbed from the atmosphere by photosynthesis during rice growth remains within the husks. By incorporating rice husks in charcoal form into construction materials, the atmospheric carbon dioxide absorbed during rice growth can be fixed within the building materials. It is known that rice husk charcoal fixes more carbon dioxide than is emitted during rice growth and charcoal production. For example, using charcoal-smoked rice husks emitted (or produced) from gasification power plants as building materials can reduce environmental impact.

[0023] 2. Estimation of carbon dioxide fixation amount (1) Amount of carbon dioxide fixed From this, we will estimate the amount of carbon dioxide fixed in a geopolymer composition containing rice husk charcoal.

[0024] Table 1 shows the composition of the geopolymer mortar composition used as the basis for the calculations. This composition will be referred to as Composition 0 hereafter. Composition 0 is the same as the common experimental mix (BS20) listed in Table 3 of Ichimiya et al., "Committee Report: Research Committee on the Application of Geopolymer Technology to the Construction Industry," Annual Proceedings of the Japan Concrete Institute, 39(1), 2017. Composition 0 contains fly ash (FA) and ground granulated blast furnace slag (BFS) as active fillers, water glass (WG) and sodium hydroxide (NaOH) as alkaline solutions, and sand as fine aggregate. JIS Type II fly ash was used. Ground granulated blast furnace slag 4000 (without gypsum) was used. A 1.5x diluted solution of water glass No. 1 (JIS) was used as water glass. A 35% aqueous solution of sodium hydroxide was used. JIS standard sand was used. [Table 1]

[0025] In comparison with the above composition 0, we will first consider composition 1. Composition 1 is based on composition 0, but 10 wt% of the sand has been replaced with rice husk charcoal. In other words, composition 1 is based on composition 0, but 10% of the total weight of the fine aggregate is rice husk charcoal. Hereinafter, the content of rice husk charcoal will be expressed as a percentage (wt%) of the total weight of the fine aggregate.

[0026] Table 2 shows the composition of composition 1 and the estimated amount of fixed carbon dioxide. Table 2 also shows the environmental load unit [kg / t], 3 Carbon dioxide emissions by material in mortar production [kg / m 3 ], and 1 m of said composition 3 Actual carbon dioxide emissions in mortar production (kg / m 3) In these parameters, a positive sign indicates that carbon dioxide is emitted, and a negative sign indicates that carbon dioxide is fixed. In Table 2, the environmental load unit values ​​for materials other than rice husk charcoal were calculated as follows, with reference to the literature (Japan Society of Civil Engineers, Concrete Committee, "Concrete Technology Series 132, Report of the Research Subcommittee for Promoting the Practical Application of Geopolymer Technology in the Civil Engineering Field (361 Committee)", Japan Society of Civil Engineers, December 14, 2022). 1) Fly ash (JIS II type): 44 kg / t 2) Ground granulated blast furnace slag (JIS 4000 grade): 60 kg / t 3) Water glass No. 1 aqueous solution (1:1) 759 kg / t 4) Sodium hydroxide solution (48.5%): 227 kg / t 5) Tap water: 0.993 kg / t 6) Mountain sand: 2.06 kg / t

[0027] Regarding rice husk charcoal, we referred to "Methodology for the application of biochar to agricultural land" (https: / / www.maff.go.jp / kyusyu / oita / attach / pdf / 220721_6-6.pdf) and estimated the amount of carbon dioxide fixed when using 1 ton of rice husk charcoal using the following formula (1).

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[0028] According to this calculation, Composition 1 is 1 m 3It can fix 71 kg of carbon dioxide per 1000g of rice husk charcoal. To evaluate the carbon dioxide fixation effect of the rice husk charcoal-blended geopolymer mortar composition, it was compared with two previously known types of environmentally friendly concrete: Conventional Product 1 (CO2-SUICOM (registered trademark) (Chugoku Electric Power Co., Inc., Kajima Corporation, Denki Kagaku Kogyo Co., Ltd.)) and Conventional Product 2 (Carbon-Recycled Concrete).

[0029] 1 is a graph showing a comparison of carbon dioxide fixation effects. Compared with Conventional Product 1 and Conventional Product 2, Composition 1 achieves 1.6 to 3.7 times more carbon dioxide fixation (carbon negative).

[0030] (2) Relationship between the amount of carbon dioxide fixed and the amount of rice husk charcoal blended Next, we will estimate the change in the amount of fixed carbon dioxide when the amount of rice husk charcoal is changed. First, we will consider Composition 2, Composition 3, and Composition 4. Tables 3 to 5 show the composition and carbon dioxide emissions for Composition 2, Composition 3, and Composition 4. Composition 2, Composition 3, and Composition 4 are based on Composition 0, but with 5 wt%, 10 wt%, and 15 wt% of the sand replaced with rice husk charcoal, respectively. [Table 3] [Table 4] [Table 5]

[0031] The carbon dioxide emissions for Compositions 2, 3, and 4 were estimated using the same method as for Composition 1. As a result, the net carbon dioxide emissions for Composition 2 were calculated to be positive, and it was estimated that the amount of carbon dioxide emitted by the composition during the production and use of this composition exceeds the amount fixed. On the other hand, the net carbon dioxide emissions for Compositions 3 and 4 were calculated to be negative, and it was estimated that the amount of carbon dioxide fixed during the production and use of these compositions exceeds the amount emitted. The above calculation results showed that these compositions can be used as carbon-negative materials.

[0032] Figure 2 is a graph showing the actual carbon dioxide emissions (by composition) for compositions 2 to 4. In Figure 2, the horizontal axis of the graph shows the rice husk charcoal content, and the vertical axis shows the carbon dioxide emissions. Linear interpolation between composition 2 and composition 3 revealed that a composition with zero actual carbon dioxide emissions, i.e., a carbon-neutral material, has a rice husk charcoal content of 7% of the total fine aggregate weight. In other words, if the rice husk charcoal content is 7% or more of the total fine aggregate weight, the composition can be used as a carbon-neutral material or a carbon-negative material.

[0033] Tables 6 and 7 show the compositions and actual carbon dioxide emissions of Composition 5 and Composition 6. Compositions 1 to 4 contained 20 vol% of the active filler as ground granulated blast furnace slag (BFS), while Composition 5 contained 10 vol% of the active filler as ground granulated blast furnace slag, and Composition 6 contained 30 vol% of the active filler as ground granulated blast furnace slag. In both Compositions 5 and 6, the content of rice husk charcoal was 5 wt% of the fine aggregate. [Table 6] [Table 7]

[0034] The actual carbon dioxide emissions for Compositions 5 and 6 were +39 kg / t and +42 kg / t, respectively, and were similar to the actual carbon dioxide emissions for Composition 2, which had a different composition of ground blast furnace slag but almost the same composition of rice husk charcoal. However, the environmental load unit of ground blast furnace slag was 60 kg / t, which was larger than the environmental load unit of fly ash, 44 kg / t, and the carbon dioxide emissions of ground blast furnace slag were about 1.8 times that of fly ash when compared at the same volume, so it is thought that the actual carbon dioxide emissions of the composition as a whole tended to increase as the content of ground blast furnace slag was increased.

[0035] Even if the actual carbon dioxide emissions calculated here are positive, all of Compositions 1 to 6 can be said to be useful because rice husk charcoal, which is an industrial waste, can be used as a mixing material and carbon dioxide can be fixed.

[0036] 3. Compression strength test (1) Relationship with the content of rice husk charcoal The inventors of the present invention conducted compressive strength tests to examine the relationship between the content of rice husk charcoal and compressive strength, considering the use of the geopolymer mortar composition as a substitute for a cured mortar (e.g., a covering block or a wave-dissipating block).

[0037] Table 8 shows the compositions of Compositions 7 to 10 used to prepare the samples used in this test. Compositions 7 to 10 are based on Composition 0, and contain rice husk charcoal at 0 wt%, 5 wt%, 10 wt%, and 15 wt% of the fine aggregate. [Table 8]

[0038] For each composition, the active filler and fine aggregate were dry mixed for 1 minute using a low-speed mortar mixer. The alkaline solution was then added and mixed for an additional 5 minutes. After mixing, the temperature, air content, and mortar flow were measured. The alkaline solution was prepared in advance and allowed to stand for approximately 1 day in an environment of 20°C.

[0039] The test pieces (mortar specimens) were cylindrical, 50 mm in diameter and 100 mm in height. The mixed sample was divided into two layers and packed into a formwork, and each layer was poked approximately 15 times with a ram. The compressive strength of the specimens was measured when they reached an age of 28 days. Compression tests were conducted using three specimens of the same composition, and the average of the measured strengths was taken as the compressive strength of the hardened material. The compression tests were conducted in accordance with JISA 1108, the compression test method for concrete.

[0040] 3 shows the results of the compressive strength test, in which the horizontal axis represents the content of rice husk charcoal and the vertical axis represents the compressive strength.

[0041] If this mortar hardened body is to be used as a covering block or wave-dissipating block, the required compressive strength is 18 N / mm 2 The compressive strength of Compositions 7 and 8 is 18 N / mm 2 The compressive strength of Compositions 9 and 10 is over 18 N / mm 2 When the data points of Compositions 7 to 11 are fitted with a second-order polynomial, the compressive strength is 18 N / mm 2 This occurs when the rice husk charcoal content is 7 wt% or less.

[0042] (2) Content of ground granulated blast furnace slag Next, the relationship between the content of ground granulated blast furnace slag and compressive strength was investigated. The content of ground granulated blast furnace slag is expected to have a significant effect on compressive strength. Table 9 shows the compositions of Compositions 11 to 15 used to prepare the samples used in this test. Compositions 11 and 12 are based on Composition 0, with the content of ground granulated blast furnace slag being 10 vol% of the activated filler. Furthermore, Compositions 11 and 12 contain 0 wt% and 5 wt% rice husk charcoal, respectively, based on Composition 0. Compositions 13 to 15 are based on Composition 0, with the content of ground granulated blast furnace slag being 30 vol% of the activated filler. Furthermore, Compositions 13, 14, and 15 contain 0 wt%, 5 wt%, and 10 wt% rice husk charcoal, respectively, based on Composition 0. [Table 9]

[0043] Fig. 4 shows the results of a compressive strength test. In this figure, the horizontal axis represents the content of ground granulated blast furnace slag, and the vertical axis represents the compressive strength. Compositions with a rice husk charcoal content of 10 wt% and ground granulated blast furnace slag contents of 10 vol% and 30 vol% were not subjected to compressive strength tests. The values ​​shown in the figure are predicted values ​​based on the slope of the curve of ground granulated blast furnace slag content versus compressive strength in the experimental results for rice husk charcoal contents of 0 wt% and 5 wt%. According to these predicted values, even if the rice husk charcoal content is 10 wt%, by increasing the ground granulated blast furnace slag content to 28 vol% or more, the required compressive strength of 18 N / mm is achieved when the composition is used as a covering block or wave-dissipating block. 2 (Dotted line in the figure) It is possible to obtain the above.

[0044] Table 10 shows the estimated carbon dioxide emissions for Composition 15. According to this example, the carbon dioxide emissions for Composition 15 are -59.9 kg / m 3 It was found that this material can be used as a carbon negative material. [Table 10]

[0045] The results of the compressive strength test revealed the following: 1) When the content of ground granulated blast furnace slag is 20 vol%, if the content of rice husk charcoal is within 7 wt%, the compressive strength is 18 N / mm 2 You can get more than that. 2) When the content of ground granulated blast furnace slag is 10 vol%, if the content of rice husk charcoal is within 5 wt%, the compressive strength is 18 N / mm 2 You can get more than that. 3) When the rice husk charcoal content is 10 wt%, if the blast furnace slag powder content is 28 vol% or more, the compressive strength is 18 N / mm 2 Furthermore, this material can be used as a carbon negative material.

[0046] 4. Variations The present invention is not limited to the above-described embodiment, and various modifications are possible. Some modifications will be described below. Two or more of the following features may be applied in combination.

[0047] The term "geopolymer composition" in this embodiment is to be interpreted broadly and may specifically include any material containing an active filler, an alkaline solution, and fine aggregate. In addition to or instead of the active filler exemplified in the embodiment, metakaolin, rice husk ash, sewage sludge, or certain volcanic ash may be used. In addition to or instead of the alkaline solution exemplified in the embodiment, potassium hydroxide (KOH) or potassium carbonate (K2CO3) may be used.

[0048] The hardened body obtained by hardening the geopolymer composition is not limited to so-called geopolymer mortar, but may also be geopolymer concrete. In addition, the standard value of the compressive strength of the hardened geopolymer (18 N / mm 2 ) is just an example.

Claims

1. an active filler containing at least fly ash and ground granulated blast furnace slag; An alkaline solution, Fine aggregate containing sand and rice husk charcoal Including, The content of the rice husk charcoal is more than 0% and 10% or less of the total weight of the fine aggregate. Geopolymer composition.

2. The geopolymer composition according to claim 1, wherein the content of the ground granulated blast furnace slag is 10% or more based on the total volume of the active filler.

3. The geopolymer composition according to claim 2, wherein the content of the rice husk charcoal is more than 0% and 5% or less of the total weight of the fine aggregate.

4. The geopolymer composition according to claim 2, wherein the content of the ground granulated blast furnace slag is 20% or more based on the total volume of the active filler.

5. The geopolymer composition according to claim 4, wherein the content of the rice husk charcoal is more than 0% and 7% or less based on the total weight of the fine aggregate.

6. The geopolymer composition according to claim 4, wherein the content of the ground granulated blast furnace slag is 30% or more based on the total volume of the active filler.

7. 10. The geopolymer composition of claim 1, comprising water glass.

8. 2. The geopolymer composition of claim 1, wherein the alkaline solution is a NaOH solution.

9. A hardened mortar obtained by hardening the geopolymer composition according to any one of claims 1 to 8.

10. Compression strength is 18N / mm ２ The hardened mortar according to claim 9 .

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