Composition for one-part geopolymer, and cured body of same

Abstract

The present invention provides a technique by which a one-part geopolymer can be realized while effectively using an alkaline waste material powder containing CaO or Ca(OH)2, such as a regenerated dust having a particle size of 0.63 mm or less, which is produced when a regenerated aggregate is produced from waste concrete. In other words, the present invention provides a composition for a one-part geopolymer, which contains a first powder component that is at least one type of powder selected from among pozzolan materials such as blast furnace slag dust and fly ash and a second powder component that is a powder containing lime (CaO) or calcium hydroxide (Ca(OH)2), and also provides a one-part geopolymer cured body obtained by adding water or moisture that does not contain an alkali metal silicate or an alkali metal hydroxide to this composition for a one-part geopolymer.

Description

Composition for one-part geopolymer and hardened product thereof

[0001] The present invention relates to a composition for a one-part geopolymer and a hardened product thereof.

[0002] Geopolymers using ground granulated blast furnace slag, fly ash, and other active fillers are expected to be used as clinker-free, unburned, low-carbon cements. Conventional hardened geopolymers are obtained by curing geopolymer compositions containing alumina silicate active fillers with an alkaline solution. The alkaline solution is often a strongly alkaline aqueous solution of sodium hydroxide and sodium silicate, which induces a fly ash reaction (see, for example, Patent Document 1). The alkaline solutions used in conventional geopolymers are highly alkaline (pH > 13.0) due to the sodium hydroxide content. Furthermore, the sodium hydroxide and sodium silicate themselves have problems such as higher costs and higher viscosities than water. In other words, conventional geopolymers have problems not only with high cost but also with worker safety and ease of use, including mixing, transportation, and application. Therefore, a so-called one-part geopolymer that does not use a strongly alkaline alkaline solution is needed. Here, one-part geopolymer refers to a type of geopolymer in which the geopolymer composition, including the active filler, is all powder, can be mixed in advance, and when used (hardened), water, or water that does not contain alkali metal silicates and alkali metal hydroxides, as in conventional Portland cement, is added.

[0003] On the other hand, when producing recycled aggregate from waste concrete, large amounts of recycled fine powder with a particle size of 0.075 mm or less are generated. However, the JIS standard for recycled aggregate stipulates that the recycled fine powder content must be 1.0% and 7.0% by mass or less for recycled coarse and fine aggregate H, 2.0% and 8.0% by mass or less for recycled coarse and fine aggregate M, and 3.0% and 10.0% by mass or less for recycled coarse and fine aggregate L. The higher the grade of recycled aggregate, the more advanced processing is required and the greater the amount of recycled fine powder generated, but the upper limit of the JIS standard content is conversely lower. Because excessive recycled fine powder must be removed, the classification and removal process requires a great deal of effort and energy. Furthermore, fine particles of 0.63 mm or less in recycled fine aggregate with a particle size of 5 mm or less have a high cement content, resulting in low density and high water absorption, making it difficult to meet the JIS standard for recycled fine aggregate (see Non-Patent Document 1). In other words, it is difficult to produce recycled fine aggregate that satisfies the JIS standard, which is an obstacle to the expansion of the use of recycled fine aggregate. Hereinafter, these recycled fine powders and fine particles will be collectively referred to as recycled fine powders.

[0004] Japanese Patent Application Laid-Open No. 2016-135723

[0005] Matsumura, U. et al.: Production of high-quality recycled fine aggregate by wet sorting method, Proceedings of the Japan Concrete Institute, Vol. 25, No. 1, pp. 1475-1480, 2003

[0006] For these reasons, it is important to develop a technology that can effectively use recycled fine powder in concrete as it is without separating it from recycled aggregate. The problem that the present invention aims to solve is to develop a technology that can effectively use recycled fine powder, such as lime (CaO) or calcium hydroxide (Ca(OH)), which is a powder with a particle size of 0.63 mm or less that is generated when producing recycled aggregate from waste concrete. ２ The present invention provides a technology that can realize one-part geopolymers while effectively utilizing alkaline waste powder containing ammonium nitrate.

[0007] The inventors have found that the recycled fine powder is Ca(OH) ２ We focused on the fact that lime (CaO) or calcium hydroxide (Ca(OH) ２The present invention has been completed based on the finding that by utilizing alkaline waste powder containing ) as part of the alkaline stimulant and filler of the geopolymer, it is possible to realize a one-part geopolymer while making effective use of the alkaline waste powder.

[0008] That is, according to one aspect of the present invention, there is provided the following composition for a one-part geopolymer: A first powder component which is at least one powder selected from ground granulated blast furnace slag, fly ash, biomass combustion ash, silica fume, and volcanic ash; and a mixture of lime (CaO) or calcium hydroxide (Ca(OH)). ２ a second powder component, the second powder component being a powder containing

[0009] In addition, according to another aspect of the present invention, there is provided a one-part geopolymer hardened body obtained by adding water or water not containing alkali metal silicate and alkali metal hydroxide to the one-part geopolymer composition of the present invention, and a one-part geopolymer hardened body obtained by adding water or water not containing alkali metal silicate and alkali metal hydroxide, and aggregate or aggregate and fiber to the one-part geopolymer composition of the present invention.

[0010] According to the present invention, lime (CaO) or calcium hydroxide (Ca(OH) ２ It is possible to realize a one-part geopolymer while making effective use of alkaline waste powder containing .

[0011] Graph showing the particle size distribution of two types of recycled fine powder (WC2 and WC3) and sea sand. Graph showing the results of TG-DTA measurements of recycled fine powder (WC2). Graph showing the results of TG-DTA measurements of recycled fine powder (WC3). Graph showing the compressive strength and usable life of geopolymers using different alkaline activators (agents). Graph showing the effect of adding gypsum on geopolymer performance. Graph showing the effect of the proportion of ground granulated blast furnace slag on geopolymer performance. Graph showing the effect of material age on the compressive strength of geopolymers with added sodium carbonate. Internal structure (SEM image) of geopolymers of different ages. Results of X-ray diffraction analysis of geopolymers of different ages and raw materials.

[0012] Hereinafter, an embodiment of the present invention will be described based on the results of experiments conducted by the inventors. 1. Experimental Overview 1.1 Materials Used (1) Active Filler (First Powder Component) JIS 4000-grade ground granulated blast furnace slag (BFS) or JIS 4000-grade ground granulated blast furnace slag (gBFS) containing gypsum, and JIS Class II fly ash (FA) were used. The chemical compositions and physical properties of these active fillers are shown in Table 1.

[0013]

[0014] (2) Recycled Fine Powder (Second Powder Component) A portion of the FA was replaced with recycled fine powder (WC). The WC samples used in this experiment are designated WC2 and WC3, depending on the source. Both samples were collected from sieved, crushed waste concrete with a particle size of 0.63 mm or less. Their chemical compositions and bone-dry densities are shown in Table 1, and their particle size distributions are shown in Figure 1. WC2 and WC3 were mixed with a standard buffer solution (pH = 6.88) at a solid-liquid mass ratio of 10:1 and stirred with an electromagnetic stirrer for 24 hours, after which the pH values ​​of the solutions were measured. The former was 12.78, and the latter was 12.80, indicating that the alkalinity of the two types of WC was almost the same. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA) measurements were performed on WC2 and WC3, and the results are shown in Figures 2 and 3. Calcium hydroxide (Ca(OH) ２ The mass loss rates of the WC2 and WC3 samples in the decomposition temperature range of Ca(OH) (400°C to 450°C) were 0.62% and 0.31%, respectively. ２It was confirmed that WC2 contains more Ca(OH) than WC3. ２ Therefore, the recycled fine powder (second powder component) was used as an alkaline activator for geopolymer (GP). The recycled fine powder also became part of the filler component of GP.

[0015] (3) Alkaline stimulant (third powder component) One-part geopolymers composed only of the first and second powder components can set and harden. To improve their strength, the addition of a powdered alkaline stimulant (third powder component) other than the alkaline stimulant (second powder component) was also investigated. For this study, sodium carbonate and sodium metasilicate were used as the third powder component. Specifically, anhydrous sodium carbonate reagent was used as the sodium carbonate, and anhydrous sodium metasilicate and sodium metasilicate (nonahydrate) were used as the sodium metasilicate. These one-part geopolymers hardened by mixing with water. For comparison, commercially available JIS No. 1 water glass (WG) diluted with water at volume ratios of 0.6:1 and 0.8:1 was used as an alkaline solution (hardening solution) in some hardened geopolymer (GP) specimens. The density of the two diluted WG solutions was 1.12 g / cm. ３ and 1.14 g / cm ３ and SiO ２ / Na ２ The molar ratio of O was 2.1. That is, the hardening liquid in the comparative example was a diluted WG liquid, while the hardening liquid in the example was water.

[0016] (4) Aggregate: Surface-dried sea sand was used. Figure 1 shows the particle size distribution. The surface-dried density was 2.56, water absorption rate 1.81%, performance rate 65.0%, chloride content 0.002%, and coarse particle rate 2.87. The mass ratio of aggregate to powder in all GP hardened bodies was 2.5.

[0017] The GP composition of the present invention is characterized in that the first powder component (active filler) and the second powder component (recycled fine powder) are essential powder components, the third powder component (alkaline irritant) is an optional powder component, and does not contain a liquid component. According to the results of research conducted by the present inventors, the content of the first powder component among these essential powder components is preferably 60% by mass or more and 90% by mass or less, and more preferably 70% by mass or more and 85% by mass or less, based on the total amount of the first powder component and the second powder component (100% by mass). In other words, the content of the second powder component is preferably 10% by mass or more and 40% by mass or less, and more preferably 15% by mass or more and 30% by mass or less, based on the total amount of the first powder component and the second powder component (100% by mass). Furthermore, when a third powder component is used in combination with the second powder component, its addition rate is preferably 5% by mass to 30% by mass, and more preferably 8% by mass to 15% by mass, based on 100% by mass of the total of the first and second powder components. On the other hand, when preparing a hardened body containing aggregate, in addition to the above-mentioned sea sand, various aggregates commonly used as raw materials for mortar and concrete can be used as aggregate. Recycled aggregate, which is crushed waste concrete, can also be used. The recycled aggregate may contain recycled fine powder, which is the second powder component. In this case, recycled fine powder (particle size 0.63 mm or less) in the recycled aggregate is considered the second powder component, and particles with a particle size greater than 0.63 mm are considered fine and coarse aggregate. Recycled fine powder with a particle size of 0.63 mm or less can be used without separation from the recycled aggregate. If the recycled aggregate is used without separation, the proportion of recycled fine powder in the recycled aggregate can be measured by a sieving test, and the amount of recycled fine powder calculated from the total amount of recycled aggregate can be added to the content of the second powder component and subtracted from the amount of aggregate.

[0018] 1.2 GP Mixing and Test Specimen Preparation Method: FA, BFS or gBFS, WC, a third powder component (alkaline irritant), and a hardening liquid (water or WG dilution solution) were weighed out based on a pre-planned mix (Table 2). Next, FA, BFS or gBFS, WC, and an optional third powder component were mixed in a mortar mixer for 60 seconds. The hardening liquid was then added to the mixer and stirred at a low speed (139 rpm) for 60 seconds, followed by a high-speed mixing (591 rpm) for 90 seconds. Immediately after mixing, the pot life was measured, and the sample was filled into a 4 cm x 4 cm x 16 cm triple-prism mold. The mold was then sealed with plastic wrap and cured at 20±3°C for 24 hours without demolding. The mold was then demolded, the test specimen sealed with plastic wrap, and cured in air at 20±2°C and 60±5% RH until the specified age.

[0019]

[0020] 1.3 Performance Test Items and Methods (1) Usable Life: Immediately after mixing the GP sample, the sample surface was pierced with a 3 mm diameter iron rod with a hemispherical tip. The time until no liquid was observed in the indentation and a clear indentation remained was measured. The time elapsed from mixing the powder and hardening liquid to this point was defined as the usable life. (2) Mechanical Performance: After curing the rectangular column specimen, a bending test was performed using a universal testing machine with a three-point method. The compressive strength was measured using the broken pieces after the bending test. (3) Chemical Analysis: The internal structure of some GP hardened bodies was observed using a scanning electron microscope (SEM). A 24 mm diameter analytical sample was embedded in resin, and after hardening, the measurement surface was polished and ultrasonically cleaned. After drying, the sample was platinum-coated. (4) X-ray Diffraction (XRD): Fragments of the compression test specimen were crushed and the crystalline content of the hardened GP body was examined using an X-ray diffractometer (XRD). XRD analysis was performed using a CuK radiation source in the 2θ range of 10 to 70° under the conditions of a 40 kV-30 mA power supply, a 1°-1°-0.15 mm slit method, a scanning speed of 2° / min, and a 0.02° step scan.

[0021] 2. Experimental Results and Discussion 2.1 Effect of Alkaline Stimulant (Agent) GP was prepared using the formulation shown in Table 2, and the pot life and compressive strength at 28 days were measured. The results are shown in Figure 4. The non-one-part GP, which used diluted WG solution as the hardening liquid, had the highest compressive strength, but the pot life was short at 15 minutes or less. This is due to the Ca(OH) in the WC. ２ This is thought to be because BFS reacted quickly with WG. GP using an alkaline solution has the aforementioned drawbacks, and from the viewpoint of setting time, GP using diluted WG as the hardening liquid is difficult to apply to on-site concrete.

[0022] GP (Series A0) composed of BFS, FA and WC3 hardens when mixed with water and has a compressive strength of 8.9 N / mm at 28 days. ２The pot life for producing hardened concrete was also sufficiently long. This one-part geopolymer, with all components except for the fine aggregate, is waste, making it low-cost and easy to handle, such as mixing and pouring into formwork. This geopolymer can be used, at least, in the manufacture of building materials for non-load-bearing sections. Furthermore, by using recycled fine aggregate or slag fine aggregate, it is possible to use all of the components of the one-part geopolymer as waste materials. The compressive strengths of GPs using either anhydrous sodium metasilicate or sodium carbonate alone as the third powder component were comparable, but the pot life of GPs containing the former was shorter. GPs using sodium metasilicate (nonahydrate) alone as the third powder component and GPs using sodium metasilicate (nonahydrate) in combination with sodium carbonate had long pot lives, but their compressive strengths at 28 days were low. Conversely, the use of anhydrous sodium metasilicate and sodium carbonate together produced high compressive strength but a short pot life. The reason for the long pot life and low strength of sodium metasilicate (nonahydrate) is that the hydrate reaction releases water from the nonahydrate, increasing the softness of the GP sample and reducing its compaction after hardening. To achieve both strength and pot life, sodium carbonate is preferred when adding a third powder component. In the sodium carbonate formulations, the sodium carbonate addition rates were 8%, 10%, and 15% by mass. The compressive strength of the three series (AII 8%, AII 10%, and AII 15%) was ranked as follows: AII 8%, AII 15%, and AII 10%. While insufficient sodium carbonate results in a limited hardening reaction and low strength, excessive sodium carbonate can weaken the hardened material or inhibit the formation of calcium carbonate, reducing the strength of the hardened material. Within the range of sodium carbonate addition rates used in this study, the pot life tended to be shorter as the sodium carbonate addition rate increased, and it appears that the optimal sodium carbonate addition rate is 10 mass% from the viewpoint of the strength of the hardened body.

[0023] 2.2 Effect of the addition of gypsum in BFS Table 3 shows the formulation of GP using BFS or gBFS and FA as active fillers, and recycled fine powder and sodium carbonate or sodium metasilicate as alkaline stimulants (agents).

[0024]

[0025] The experimental results, which show the effect of the presence or absence of gypsum on the working life and compressive strength of GP, are shown in Figure 5. As shown in the figure, the use of gypsum-free BFS tended to result in higher compressive strength and slightly longer working life for the GP hardened body than the use of gBFS containing gypsum. When ground granulated blast furnace slag is added as an admixture to Portland cement (PC) concrete, the inclusion of gypsum is advantageous for exerting the latent hydraulic properties of the ground granulated blast furnace slag, so gBFS containing gypsum is commonly used. Therefore, it is speculated that when sodium carbonate is not added, the use of gBFS will result in better strength development than the use of BFS. However, in GP to which sodium carbonate or sodium metasilicate has been added, the CaSO , a component of gypsum, ４ SO ４ ２－ is a strongly acidic ion, so Na ２ CO ３ or hydroxide ions (OH － It is speculated that the use of gBFS may have had an adverse effect because it neutralizes the alkalinity of the concrete, weakening the alkaline stimulation received by the BFS. However, if sodium carbonate is not added or is added at a low rate, and there is a risk that the stimulation received by the BFS will be insufficient, or if the setting time is long and strength development is low in a low-temperature curing environment, the addition of gypsum is preferable.

[0026] 2.3 Effect of BFS Mixing Ratio Figure 6 shows the compressive strength and pot life of GP made with the formulation shown in Table 4. Regardless of the presence or absence of gypsum in the ground granulated blast furnace slag or the type of third powder component, the higher the proportion of ground granulated blast furnace slag, the higher the compressive strength and the shorter the pot life tended to be. To increase the strength of this type of one-part geopolymer hardened body, it is effective to increase the mixing ratio of ground granulated blast furnace slag within the allowable limit for shortening the pot life.

[0027]

[0028] 2.4 Effect of Ageing Figure 7 shows the compressive strength of GPs containing sodium carbonate as a third powder component at 28 days and 3 months of age. All series used gypsum-free BFS at 30% of filler P (= BFS + FA + WC), FA at 50% of P, and WC2 at 20% of P. The liquid-powder ratio was 55%. Sodium carbonate was added in four patterns: 8, 10, 15, and 20% by mass of P. As shown in Figure 7, the strength at 3 months of age increased in all series compared to 28 days, but the trend in compressive strength between series was the same as at 28 days. Because the hardening reaction due to the latent hydraulic properties of BFS and the pozzolanic reaction of FA take time, the strength at 3 months of age was higher than at 28 days of age. Therefore, this type of one-part geopolymer exhibits increased strength over long periods of time, and strength evaluation is required at least 3 months of age.

[0029] 2.5 Internal structure of the hardened body (results of SEM analysis) Figure 8 shows SEM images of GP (Series AII 10% in Table 2) with added sodium carbonate at 28 days and 3 months of age. At 28 days of age, spherical FA particles were observed that did not react, but at 3 months of age, the reaction progressed and the surface appeared to be eroded by leaching. Ca(OH) produced by hydration of PC (Portland cement) contained in the recycled fine powder. ２ This is because the pozzolanic reaction of FA with 28-day-old specimens takes time. Many cracks are observed in the 28-day-old specimens due to the degree of reaction, but the 3-month-old specimens are denser and have fewer cracks. In addition, calcite (CaCO ３ ) was confirmed in the specimens aged for three months, but not in the specimens aged for three months. This is because the formation of C-(A)-S-H gel increased with age and fused with calcite. As described below, X-ray diffraction analysis (XRD analysis) confirmed the presence of calcite in the specimens aged for three months.

[0030] 2.6 Results of XRD analysis Figure 9 shows the XRD analysis results of GP (Series AII 10% in Table 2) with added sodium carbonate at 28 days and 3 months of age. In Figure 9, the top row shows the XRD analysis results for the 3-month age, and below that is the 28-day age. Below the 28-day age are the XRD analysis results for WC2, below that for WC3, and below that for raw material FA. Since raw material BFS does not contain crystalline matter, the XRD analysis results for BFS are omitted in the figure. At 28 days of age, Ca(OH) ２ and CaCO ３ At 3 months of age, the peak of Ca(OH) ２ No peak appears, CaCO ３ It was observed that the intensity of the peak increased. ２ The peak is derived from WC. Ca(OH) ２ is consumed by reacting with FA. ２ CO ３ ) and BFS Ca ２＋ reacts to form CaCO ３ It seems to generate

[0031] Ca(OH) produced by hydration of PC ２ It is generally known that the latent hydraulic properties of ground granulated blast furnace slag are brought out, and the ground granulated blast furnace slag causes a hardening reaction in PC concrete, improving the performance of PC concrete. In addition, the hydration product of PC, Ca(OH) ２ Based on these general findings, the results of SEM and XRD analysis, and the experimental results of geopolymer without the addition of a third powder component, the hardening mechanism of the one-part geopolymer invented in this study is that the recycled fine powder acts as an alkaline activator, and the Ca(OH) ２ The other powders in the geopolymer, especially the active filler (ground granulated blast furnace slag, fly ash, or a mixture thereof), harden through latent hydraulic or pozzolanic reaction, while the third powder component activates the latent hydraulic properties of the ground granulated blast furnace slag and the pozzolanic reactivity of the fly ash, promoting the setting and strength of the powder. ２In addition, recycled fine powder with a high content of Ca(OH) is preferable. ２ and other powders or fine particles containing quicklime, such as steel slag powder, municipal waste incineration ash, sewage sludge incineration ash, expansive additives for concrete, alite (C ３ S) and Belite (C ２ Various cements containing sulphur dioxide, dried powder of sludge from ready-mixed concrete, and crushed material from hardened residual concrete can also be used instead of the recycled fine powder.

[0032] Sodium carbonate (sodium carbonate) is a natural mineral, but it can also be artificially synthesized. ２ Raw material is required. Exhaust CO ２ When sodium carbonate produced by recycling CO ２ This will fix the

[0033] 3. Summary The findings obtained in the above experiments and the considerations based on those findings can be summarized as follows: (1) A one-part geopolymer can be realized by using recycled fine powder of the second powder component as an alkaline stimulant, or by using recycled fine powder in combination with a third powder component that is at least one powder selected from sodium carbonate and sodium metasilicate. In other words, since the geopolymer composition of the present invention is entirely powder and does not contain any liquid components, it can be mixed in advance, and a hardened geopolymer can be obtained at the construction site by adding water as a hardening liquid, or water containing an admixture (e.g., retarder) to improve the performance of the GP, even though it does not contain alkali metal silicate or alkali metal hydroxide. (2) Achieving both usable time and strength, and further reducing CO ２Considering the fixation of the third powder component, sodium carbonate powder is optimal. Specifically, the sodium carbonate content is preferably 50% by mass or more, and most preferably 100% by mass, of the third powder component (100% by mass). (3) Using gypsum-added BFS may reduce the strength of GP and shorten its usable life. However, gypsum-added BFS can be used depending on the target values ​​for the usable life before hardening and the strength after hardening. Regardless of whether gypsum is added, the higher the mixing ratio of ground granulated blast furnace slag, the higher the GP strength and the shorter the usable life. (4) The strength of GP using BFS, FA, and WC increases with age. One-part geopolymers that meet the JIS standard value for ordinary Portland cement (compressive strength at 28 days: 42.5 MPa) can be prepared. (5) In one-part GP hardened bodies using recycled fine powder and sodium carbonate as alkaline activators, Ca(OH) ２ decreases with age, but CaCO ３ increases.

[0034] The recycled fine powder is composed of sand particles and Ca(OH) ２ Because it contains cement hydration reaction products other than those listed above, it cannot completely react in the one-part GP hardened body. Therefore, recycled fine powder not only serves as an alkali stimulant for the geopolymer but also as an inert filler, i.e., an inert powder. As mentioned above, by measuring the proportion of recycled fine powder in the recycled aggregate, the recycled fine powder can be used as a powder in geopolymer mortar or concrete together with recycled fine and coarse aggregates with particle sizes exceeding 0.63 mm without classification. Therefore, the technology of the present invention simplifies the manufacturing process of recycled aggregate, making it easier for the quality of recycled aggregate to meet JIS standards.

[0035] The results of this experiment also lead to the following inventions. 1. A geopolymer composition comprising: a first powder component which is at least one type of powder selected from ground granulated blast furnace slag and fly ash; and a second powder component which is a powder of crushed waste concrete having a particle size of 0.63 mm or less; and no liquid component. 2. The geopolymer composition described in 1 above, wherein the content of the second powder component is 10% by mass or more and 40% by mass or less, based on 100% by mass of the combined amount of the first powder component and the second powder component. 3. The geopolymer composition described in 1 above, to which a third powder component which is at least one type of powder selected from sodium carbonate and sodium metasilicate is added. 4. The geopolymer composition described in 1 above, wherein the addition rate of the third powder component is 5% by mass or more and 30% by mass or less, based on 100% by mass of the combined amount of the first powder component and the second powder component. 5. A hardened geopolymer obtained by adding water to the geopolymer composition described in any one of items 1 to 4. 6. A hardened geopolymer obtained by adding water and aggregate to the geopolymer composition described in any one of items 1 to 4. Note that the "geopolymer compositions (not including liquid components)" in items 1 to 4 can be rephrased as "compositions for one-part geopolymers." In other words, the geopolymer compositions in items 1 to 4 are compositions for the aforementioned "one-part geopolymers" (geopolymer compositions containing active fillers are all powders that can be mixed in advance, and when used (hardened), water or water that does not contain alkali metal silicates and alkali metal hydroxides, like conventional Portland cement, is added). From the same perspective, the "hardened geopolymers" in items 5 and 6 can be rephrased as "one-part geopolymer hardened bodies."

[0036] Next, the first powder component, the second powder component, and the third powder component constituting the one-part geopolymer composition of the present invention (hereinafter referred to as "one-part geopolymer composition") will be described in detail, including the theoretical background.

[0037] The first powder component can be generally exemplified as a mixture of one or more of ground granulated blast furnace slag, which has latent hydraulic properties, and powder of industrial waste or by-products, which has pozzolanic activity (pozzolanic material). Applicable examples are described below.

[0038] Blast furnace slag is a by-product discharged from steel mills and contains lime (CaO), silica oxide (SiO ２ ), alumina oxide (Al ２ O ３ ), and are broadly divided into granulated blast furnace slag and air-cooled blast furnace slag. Granulated blast furnace slag powder is produced by quenching molten slag discharged from a steelworks blast furnace with water or air and then pulverizing it into a glassy substance. The glassy network structure is easily destroyed in an alkaline aqueous solution with a pH of 11.5 or higher, initiating a hydration reaction and hardening. On the other hand, air-cooled blast furnace slag powder is produced by pulverizing crystalline rock-like material obtained by pouring molten slag discharged from a steelworks blast furnace into a cooling yard and gradually cooling it. It is classified as an inert powder with extremely low reactivity even in alkaline solutions. Granulated blast furnace slag powder is also commonly referred to as ground blast furnace slag.

[0039] Ground granulated blast furnace slag is specified as 3000, 4000, 6000, and 8000 classes according to the JIS standard (JIS A6206 Ground granulated blast furnace slag for concrete). Ground granulated blast furnace slag 3000 has a specific surface area of ​​2750 cm ２ / g or more 3500cm ２ / g or less, and the specific surface area of ​​4000 is 3500 cm ２ / g or more 5000cm ２ / g or less, and the specific surface area of ​​6000 is 5000 cm ２ / g or more 600cm ２ / g or less, and the specific surface area of ​​8000 is 7000 cm ２ / g or more 10000cm ２ Any of these may be used, but the finer the particle, the higher the strength development.

[0040] Using only ground granulated blast furnace slag, a by-product of pig iron production, as the first powder component of the one-part geopolymer composition of the present invention allows for the creation of a geopolymer. The resulting geopolymer has high strength after hardening, but is costly and uses little waste. Furthermore, the setting time, which is an indicator of workability, is short, and there is a risk of the geopolymer hardening before construction is complete. Therefore, adding a pozzolanic material with low reactivity, such as fly ash, or an inert powder, reduces strength but prolongs the setting time, reducing costs and expanding waste utilization. It is best to select the first powder component based on the geopolymer's strength and setting time goals.

[0041] On the other hand, although it has almost no hydraulic hardening properties by itself, in an environment where water is present, it chemically reacts with calcium hydroxide (pozzolanic reaction) to form calcium silicate hydrate (nCaO.SiO ２ ・H ２ O) and calcium aluminate hydrate (3CaO.Al ２ O ３ ・6H ２ Finely powdered siliceous and aluminous materials that can be solidified to produce siliceous and aluminous silica (O) are called pozzolanic materials. Representative artificial pozzolanic materials are fly ash, silica fume, and metakaolin. Natural pozzolanic materials include volcanic ash, tuff, diatomaceous earth, silica clay, and pumice (pumice). These natural pozzolanic materials are rich in volcanic glass, mainly siliceous or siliceous and aluminous. Below, we will introduce pozzolanic materials that can be used in the one-part geopolymer composition of the present invention.

[0042] Fly ash is a fine powder waste material consisting of silica and aluminum that is generated when coal is burned in coal-fired power plants. When pulverized coal is burned, it rises with the combustion gas and is collected by an electrostatic precipitator. The main chemical component of fly ash is silicon dioxide (SiO ２ ) 40-75%, aluminum oxide (Al ２ O ３ ) 15-35%, ferric oxide (Fe ２ O ３) 2-20%, calcium oxide (CaO) 1-10%, magnesium oxide (MgO) 1-3%. Fly ash is classified into types I to IV according to the JIS standard (JIS A6201 Fly ash for concrete). Type I fly ash has a 45 μm sieve residue (wire sieve method) of 10% or less and a specific surface area (Blaine method) of 5000 cm ２ / g or more and a flow value ratio of 105% or more, and fly ash type II has a sieve residue of 40% or less and a specific surface area of ​​2500 cm ２ / g or more, and the flow value ratio is 95% or more. Fly ash type III has a sieve residue of 40% or less and a specific surface area of ​​2500 cm ２ / g or more, and the flow value ratio is 85% or more. Fly ash type IV has a sieve residue of 70% or less and a specific surface area of ​​1500 cm ２ Any standard fly ash may be used, and among them, it is preferable to use type I or type II in consideration of reactivity.

[0043] Silica fume is a silicon dioxide (SiO ２ Silica fume is a by-product whose main component is silicon dioxide (SiO ), and is an ultra-fine glassy particle that is captured by a dust collector (such as a bag filter). The main component of silica fume is more than 80%, and in high-quality silica, more than 90% is silicon dioxide (SiO ２ ), it exhibits extremely high pozzolanic reactivity with calcium hydroxide. In addition, because it is an ultrafine particle (Nano-SiO2), silica fume fills the minute gaps between other powder particles, providing a filling effect (filler effect) that makes the structure of the hardened body extremely dense.

[0044] Metakaolin is an artificial pozzolanic material obtained by calcining (heating) kaolin at a specific temperature (usually around 550-900°C). During this calcination process, the crystalline structure of kaolin is broken, and the hydroxyl groups within the molecule are dehydrated and released, resulting in an amorphous structure. This amorphization and dehydration of the hydroxyl groups gives it extremely high pozzolanic activity (reactivity), allowing it to react efficiently with calcium hydroxide and harden. It is said to have high pozzolanic activity second only to silica fume. However, since calcining kaolin clay requires energy, the use of metakaolin is thought to increase the environmental impact of one-part geopolymers more than the use of waste materials. The main component of metakaolin is silicon dioxide (SiO ２ ) and aluminum oxide (Al ２ O ３ Although it varies somewhat depending on the purity of the original kaolin deposit and the firing conditions, the total of both components usually accounts for 95% or more (the former 50-55%, the latter 40-45%). Considering the reaction rate of metakaolin, the specific surface area (Blaine value) should be at least 1500 cm ２ / g or more is preferable, and 3000 cm ２ / g or more is more preferable.

[0045] Biomass boilers have been around for a long time, and biomass combustion ash has been emitted. In recent years, with the move away from fossil fuels and the diversification of power sources from the perspective of energy security, the construction of wood biomass power plants that generate electricity using plant resources such as waste wood, thinned wood, firewood, and wood pellets has been increasing. This contributes to the role of renewable energy, the prevention of global warming, and the creation of a recycling-oriented society. However, since the majority of biomass power generation is actually thermal power generation using wood pellets, there is a risk that producing the fuel pellets will accelerate deforestation. Therefore, biomass fuel is also sometimes co-combusted with fossil fuels such as coal. Effective reuse of biomass fuel ash or co-combustion ash is an important issue.

[0046] Most conventional biomass boilers have a combustion temperature of around 650°C. Biomass power generation is mainly at 800-900°C. Because this is lower than the pulverized coal combustion temperature (1400-1500°C) of coal-fired power plants, the vitrification rate of biomass combustion ash is about 10% lower than that of fly ash, which consists of spherical particles (https: / / www.nedo.go.jp / content / 100969853.pdf). Also, biomass combustion ash contains many angular, porous particles. However, the main component of biomass combustion ash (SO ２ , Al ２ O ３ , CaO, Fe ２ O ３ ) is the same as that of fly ash (Toru Obata: Use of woody biomass combustion ash and investigation of bamboo chip co-firing conditions, Kagoshima Prefectural Industrial Technology Center Research Report, No. 34, pp. 5-10, 2020, https: / / www.kagoshima-it.jp / pdf / kenkyu_report / k_report_2020_02.pdf). In addition, experimental results showed that the strength of the hardened geopolymer did not decrease even when 30% or less of fly ash was replaced with biomass combustion ash (Masashi Suto, Masaru Hata, Daigo Ito: Fundamental properties of geopolymer mortar mixed with biomass ash, Abstracts of the 2022 Annual Meeting of the Japanese Society of Irrigation, Drainage and Forestry Engineering, pp. 199-200, September 2022). This indicates that biomass combustion ash contains a glassy component (SiO ２ , Al ２ O ３ ) is less than that of fly ash, so its pozzolanic reaction activity is lower than that of fly ash, but it can still be classified as a pozzolanic material. Note that the concept of biomass fuel ash in this invention includes the aforementioned mixed combustion ash.

[0047] Volcanic ash, a representative natural pozzolanic material, is formed when magma erupts to the Earth's surface and cools rapidly in the air. It contains amorphous particles (called volcanic glass particles) that solidify shortly after the magma cools and crystallizes, crystalline fragments of minerals (quartz, feldspar, pyroxene, amphibole, etc.) that had already crystallized before the magma erupted, and fragments of older surrounding rocks that were crushed by the eruption. Volcanic glass particles can take on a wide variety of shapes (acicular, fibrous, foamed, plate-like, etc.) due to the process of magma vesication (gas release) and fragmentation. Volcanic ash varies greatly in composition, glass content, particle size distribution, etc. depending on the source, the composition of the erupted magma (basalt, andesite, rhyolite, etc.), and the type of eruption. The main component of volcanic ash is silicon dioxide (SiO ). ２ , 50% to 70% or more), aluminum oxide (Al ２ O ３ , about 10% to 20%, ferric oxide (Fe ２ O ３ Volcanic ash contains glassy components (especially siliceous glass), and is therefore used in PC concrete as a pozzolanic material exhibiting pozzolanic reactivity, and can be used as a composition for the one-part geopolymer of the present invention.

[0048] Geopolymers are inorganic polymers formed by the dissolution and polycondensation of aluminosilicate materials, primarily containing silicon (Si), aluminum (Al), and some calcium (Ca), in an alkaline solution. Metakaolin, other calcined clays, and volcanic ash are primarily composed of amorphous aluminosilicates. As mentioned above, metakaolin is formed by calcining kaolinite and is rich in highly pure and highly reactive amorphous Si and Al. Volcanic ash, which is largely composed of volcanic glass (amorphous), is also an excellent source of Si and Al. These materials can contribute to the formation of aluminosilicate gels (such as N-A-S-H gels), which are the core of geopolymer reactions.

[0049] Although no experiments have been conducted in which one-part geopolymer compositions are prepared using one or more of the above-mentioned pozzolanic materials as the first powder component and then water or moisture is added to produce a hardened product, based on the hardening principle of the pozzolanic reaction, it is possible to produce a one-part geopolymer composition and its hardened product using only the above-mentioned pozzolanic material as the first powder component.

[0050] Considering the reactivity of the geopolymer of the powder, one or more of ground granulated blast furnace slag and pozzolanic materials can be used as the first powder component. Furthermore, among pozzolanic materials containing metakaolin, fly ash is preferred in terms of geopolymer reactivity, waste utilization, quality stability, and cost. Among these, ground granulated blast furnace slag and fly ash, which have excellent strength development, are preferred. Furthermore, as mentioned above, geopolymers using only ground granulated blast furnace slag have a short setting time, large drying shrinkage, and are expensive, so it is more preferable to use a mixed powder of ground granulated blast furnace slag and fly ash as the first powder component.

[0051] By using a grinder to grind finer granulated blast furnace slag powder and the above-mentioned pozzolanic material, the surface area increases. Because chemical reactions occur on the surface of the particles, the larger the surface area, the more reaction sites there are, increasing the chances of contact with calcium hydroxide and alkaline stimulants, and improving activity. Powerful high-energy grinding also has the effect of modifying the particle surface, resulting in mechanochemical activation. Adjusting the rapid cooling method of granulated blast furnace slag can increase the glass content and basicity ((CaO + MgO + Al ２ 0 ３ ) / SiO ２ It is preferable to use ground granulated blast furnace slag, which has high latent hydraulic properties due to an improvement in the ratio of the granulated blast furnace slag to the granulated blast furnace slag.

[0052] In addition to the above industrial wastes and by-products, there are various other industrial wastes and by-products. ２ There are other natural materials besides metakaolin and volcanic ash that are reactive in the presence of . From the perspective of expanding waste utilization and improving the performance of hardened geopolymers, these materials can partially replace the first powder component. Below, we introduce alternatives to the first powder component.

[0053] Copper slag is a by-product produced during the copper smelting process when impurities (mainly iron and silicon) are removed from copper ore. After being melted at high temperatures, it is usually rapidly cooled by water, and is therefore characterized by its high content of glassy amorphous structures. The majority of copper slag's chemical composition is glassy phyllite (2FeO.SiO ２ ) Other iron crystal minerals include magnetite (Fe ３ O ４） and hematite (Fe ２ O ３ ) can provide amorphous Si for the formation of geopolymer gels and calcium silicate hydrate gels.

[0054] Red mud is a material made by extracting alumina (aluminum oxide: Al) from bauxite, the raw material for aluminium. ２ Red mud is a reddish-brown solid waste generated during the production of iron oxide (FeO3). After the aluminum component (aluminum hydroxide) in bauxite is dissolved and extracted with sodium hydroxide (caustic soda) solution, the remaining impurities become red mud. Red mud is a substance that contains iron oxide (Fe ２ O3): 40% to 60%, silicon dioxide (SiO ２ ): 10% to 15%, aluminum oxide (Al ２ O3): 10% to 15%, calcium oxide (CaO): 6% to 10%, and sodium oxide (Na ２ O): 5% to 6%. Red mud contains amorphous aluminosilicates, and the sodium hydroxide (caustic soda) used in the Bayer process also remains in the red mud. For this reason, red mud is very alkaline (pH 10 to 13), which not only provides amorphous Si and Al for the formation of geopolymer gel and calcium silicate hydrate gel, but also stimulates the reaction of ground granulated blast furnace slag and pozzolanic materials.

[0055] In sewage sludge incineration ash molten slag and municipal waste incineration ash molten slag, many components become amorphous during the high-temperature melting and rapid cooling process, and they supply elements necessary for geopolymers, such as Si, Al, and Ca. In particular, these slags have a high Ca supply capacity, which contributes to the formation of calcium-containing geopolymer gel (C-A-S-H gel) or calcium silicate hydrate (C-S-H gel), and is expected to have the effect of increasing the early strength development of the hardened body.

[0056] Perlite is an amorphous quartz (SiO ２ When the powder is mixed with an alkaline solution, this amorphous component can dissolve in the alkaline solution and provide the Si necessary for the geopolymer reaction.

[0057] Pozzolanic materials such as ground granulated blast furnace slag and fly ash are used as the primary raw materials for conventional geopolymers or the one-part geopolymers of the present invention because they contain abundant amorphous Si, Al, and Ca. The active fillers, or activated powders, described above, can also provide these elements in amorphous form, allowing them to partially replace the ground granulated blast furnace slag or pozzolanic materials to produce the one-part geopolymers of the present invention.

[0058] On the other hand, materials such as stone powder, slowly cooled blast furnace slag, and fluidized bed coal ash (especially low-calcium fluidized bed coal ash) are classified as inert powders that have low or almost no chemical reactivity in the alkaline solution of geopolymers.

[0059] The stone powder is a dried powder of crushed stone powder (in the case of a dry manufacturing method) or dehydrated cake (in the case of a wet manufacturing method) that is a by-product generated during the production of crushed stone and crushed sand in the stone crushing industry. It may also be a dried powder of recycled crushed stone powder or dehydrated cake, or it may be a stone powder made by crushing at least one type of rock selected from limestone and siliceous rocks such as sandstone and slate.

[0060] As mentioned above, slowly cooled blast furnace slag has a low reactivity because its crystallinity is high due to the slow cooling rate, whereas ground blast furnace slag contains a large amount of glass due to rapid cooling.

[0061] Fluidized bed coal ash is classified into high-calcium-content fluidized bed coal ash containing 5% or more of free lime (CaO) and low-calcium-content fluidized bed coal ash containing 5% or less of free lime (CaO) because fluidized bed boilers use limestone as a desulfurization material. However, the amorphousness of the aluminosilicate in fluidized bed coal ash is relatively low, which limits the supply of Si and Al necessary for the geopolymer reaction.

[0062] While high-calcium fluidized-bed coal ash can be used to prepare geopolymer hardened bodies, low-calcium fluidized-bed coal ash, stone powder, and blast furnace slag powder do not function as active precursors for geopolymers. These inert powders do not function as major components in the geopolymer reaction. However, by substituting part of the blast furnace slag powder or pozzolanic materials, they can function as aggregates or fillers in one-part geopolymer hardened bodies, improving the strength of the hardened bodies, ensuring volume stability, suppressing drying shrinkage, and reducing raw material costs.

[0063] Therefore, amorphous silicon dioxide (SiO ２ ), aluminum oxide (Al ２ O ３ One or more of the following powders can be used to replace a portion (e.g., 10 to 80% by mass) of the ground blast furnace slag or pozzolanic material: metakaolin containing at least one type of calcium oxide (CaO), copper slag powder, red mud, calcined clay other than metakaolin, volcanic ash, sewage sludge incineration ash fused slag powder, municipal waste incineration ash fused slag powder, high-calcium-containing fluidized-bed coal ash, and perlite powder; and inert powders such as stone powder having a mainly crystalline component, slowly cooled blast furnace slag powder, and low-calcium-containing fluidized-bed coal ash. Since these substitutions may result in a decrease in the strength of the hardened body, a substitution rate of 10 to 50% by mass is preferred, and a substitution rate of 10 to 30% by mass is more preferred. Furthermore, these powders should have a Blaine value of at least 1500 cm ２ / g and 3000 cm ２ / g or more is preferred.

[0064] On the other hand, the ground granulated blast furnace slag and the pozzolanic material are soluble in calcium hydroxide (CaOH) in an environment where water is present. ２When calcium oxide (CaO) or calcium hydroxide (Ca(OH)) is mixed, it hardens by latent hydraulic or pozzolanic reaction. ２ A powder containing lime or hydrated lime (Ca(OH)), i.e., the second powder component, can be mixed with ground granulated blast furnace slag or any of the above pozzolanic materials to produce a one-part geopolymer composition. ２ ), calcium oxide (CaO) or calcium hydroxide (Ca(OH) ２ ) directly contained, and Ca(OH) ２ Examples of materials that can produce the second powder component include cement clinker or various cements containing cement clinker, crushed concrete, ready-mixed concrete sludge, steel slag, and lime-based concrete expansive additives. The following introduces materials that can be used as the second powder component.

[0065] Lime or slaked lime can be produced by the thermal decomposition of limestone, but CO ２ Because of the large amount of emissions, it is preferable to use by-product (slaked) lime. For example, calcium carbide (CaC ２ ) reacts with water to produce acetylene gas (C ２ H ２ When slag is produced, a muddy by-product consisting primarily of calcium hydroxide is generated.

[0066] One of the products of the hydration reaction of cement clinker is calcium hydroxide (CaOH). ２ Therefore, by mixing cement clinker or various cements containing cement clinker with the above ground granulated blast furnace slag or the above pozzolanic material, the one-part geopolymer composition of the present invention can be prepared. ２ The use of cement clinker as the second powder component effectively promotes the solidification reaction between ground granulated blast furnace slag and pozzolanic material compared to the use of a waste second powder component, but CO2 is emitted during the production of the one-part geopolymer of the present invention. ２ Increase.

[0067] Hardened materials (hardened cement paste, mortar, concrete, etc.) made using cement containing cement clinker contain calcium hydroxide (CaOH) as one of the products of the clinker hydration reaction. ２ ) are also present, so by mixing the ground concrete with the above-mentioned granulated blast furnace slag powder and the above-mentioned pozzolan material, the one-part geopolymer composition of the present invention can be prepared. Calcium hydroxide is a sparingly soluble compound, or has low solubility in water. Furthermore, the coarser the ground concrete, the higher the aggregate content and the lower the calcium hydroxide content. Therefore, from the viewpoint of the setting time and strength development after adding water to the one-part geopolymer composition of the present invention, it is preferable to use powdered ground concrete.

[0068] However, hardened materials made using cement containing cement clinker are CO ２ To achieve the low carbon characteristics of the one-part geopolymer of the present invention, it is preferable to use pulverized material (recycled fine powder) with a particle size of 0.63 mm or less obtained by pulverizing waste concrete discharged from dismantled concrete structures. The use of recycled fine powder with a particle size of 0.075 mm or less is more preferable because it contains a large amount of hardened cement components. The use of recycled fine powder or recycled fine powder in this way can contribute to the effective recycling of waste concrete.

[0069] The fine powder (called dry powder of ready-mixed concrete sludge) obtained by drying and grinding returned concrete (residual concrete) generated at ready-mixed concrete (ready-mixed concrete) plants and sludge (mud-like solids) recovered from mixer trucks and plant cleaning wastewater contains unhydrated Portland cement particles, calcium hydroxide, and residues of admixtures (fly ash, ground granulated blast furnace slag, silica fume, etc.) that were originally mixed into the concrete. Therefore, the dry powder of ready-mixed concrete sludge has latent hydraulic and pozzolanic properties and can be used as one of the components of the one-part geopolymer composition of the present invention. The Blaine value of the dry powder of ready-mixed concrete sludge is at least 1500 cm ２ / g and 3000 cm ２ / g or more is preferred.

[0070] Steelmaking slag is a by-product of the steelmaking process (particularly in converter furnaces) during the refining of steel from molten pig iron. Because quicklime (CaO) is added as a flux to remove impurities from iron ore, the slag is characterized by the presence of free lime (free-CaO) along with various oxide components. Free lime is generated due to the addition of more quicklime than the theoretical amount for efficient desulfurization and dephosphorization; the relatively short time required for steelmaking in converter furnaces means that the added quicklime does not completely melt and react, leaving some unreacted free lime; and the cooling process of the slag, where some calcium remains uncombined with other components. The free lime content in steelmaking slag varies significantly depending on refining conditions, but is generally around a few percent. The presence of free lime makes steelmaking slag highly alkaline (the pH of the water immersion solution is 12.0 or higher), which brings out the latent hydraulic properties of the ground blast furnace slag and allows the pozzolanic reaction of the pozzolanic material to occur.

[0071] Concrete expansive additives are materials added to concrete to prevent cracking due to drying shrinkage and to introduce chemical prestress. Depending on their main components and expansion mechanism, they are classified into two types: lime-based expansive additives and ettringite-based expansive additives. The former is mainly composed of calcium oxide (CaO), which reacts with water in the concrete to produce calcium hydroxide (Ca(OH) ２ The latter is mainly composed of calcium sulfoaluminate (CSA) clinker, and contains lime (CaO), gypsum (CaSO ４ ), bauxite (Al ２ It is a special compound that is fired using raw materials such as limestone and pozzolanic acid. Therefore, adding a lime-based expanding agent can solidify ground granulated blast furnace slag and pozzolanic materials.

[0072] In the powders and fine powders containing lime or calcium hydroxide that can be used as the second powder component, cement clinker, various cements, and lime-based expansive materials are manufactured using limestone as a raw material, so CO ２ The amount of waste generated is large. Crushed waste concrete (grain size: 0.63 mm or less), dried powder of ready-mixed concrete sludge, and powdered steelmaking slag are derived from industrial by-products and waste. Powdered steelmaking slag contains free lime, which is easily soluble in water, and is therefore advantageous for the early strength development of geopolymers. However, the free lime content is difficult to adjust, and the content may decrease with aging. Furthermore, collecting, drying, and crushing ready-mixed concrete sludge is time-consuming. Therefore, it is more preferable to use crushed waste concrete (grain size: 0.63 mm or less) as the second powder component.

[0073] A one-part geopolymer composition can be prepared by mixing one or more of the ground waste concrete (particle size: 0.63 mm or less) containing lime or calcium hydroxide, dry powder of fresh concrete sludge, or ground steel slag as a second powder component with a mixed powder (first powder component) of one or more of the ground granulated blast furnace slag and the pozzolanic material. A hardened product can then be produced by further adding water or moisture. To improve the performance of the one-part geopolymer or to reduce carbon dioxide through carbon fixation, the following powders can also be further mixed as a third powder component to prepare a high-performance one-part geopolymer composition. The following powders can be used as the third powder component:

[0074] Gypsum is extracted from mines as a natural mineral, and is also produced as a by-product in the flue gas desulfurization process at thermal power plants and in the phosphate fertilizer manufacturing process. Amorphous calcium oxide (CaO) and aluminum oxide (AlO) contained in ground granulated blast furnace slag are ２ O3) is supplied by gypsum sulfate ions (SO ４ ２－ ) to form ettringite crystals (3CaO.Al ２ O ３ 3CaSO ４ ・32H ２O), which has the effect of filling voids inside the hardened body and densifying the structure, contributing to improved strength. In addition, gypsum serves as a calcium supply source, and the sulfate ions supplied from the gypsum promote the dissolution of amorphous calcium components in the ground granulated blast furnace slag, allowing the latent hydraulic properties of the ground granulated blast furnace slag to appear more efficiently.

[0075] Gypsum can also enhance the pozzolanic activity of pozzolanic materials such as fly ash. The sulfate ions provided by gypsum act as catalysts for calcium hydroxide and amorphous aluminum (Al) in pozzolanic materials. ２ O3) to form ettringite crystals. The formation of ettringite contributes to improving the strength of the hardened body. It also works to reduce the aluminum concentration in the liquid phase, thereby promoting further aluminum leaching from the pozzolanic material. This continuous aluminum leaching accelerates the early stage of the pozzolanic reaction. The consumption of aluminum due to ettringite formation promotes the destruction of the silicate structure on the surface of fly ash particles, indirectly aiding in the leaching of silicon and increasing the activity of the pozzolanic reaction. Therefore, gypsum increases the reactivity of ground granulated blast furnace slag with pozzolanic material, and its use in the one-part geopolymer composition of the present invention is expected to improve the strength of the geopolymer, especially its early strength.

[0076] Regarding the method of mixing gypsum, gypsum-containing ground granulated blast furnace slag may be used. Furthermore, gypsum may be added externally. When gypsum-free ground granulated blast furnace slag is used or when only a pozzolanic material is used as the first powder component, gypsum may be added externally.

[0077] When producing geopolymers, alkaline stimulants such as sodium hydroxide and potassium hydroxide are often used to activate blast furnace slag and fly ash. However, because they are strongly alkaline, safety is an issue during the preparation, storage, transportation, and hardening of geopolymer compositions. When sodium carbonate or potassium carbonate dissolves in water, it exhibits weak basicity and produces hydroxide ions (OH － ) to generate (Na ２ CO ３　 +H ２ O⇔NaHCO ３+ NaOH). This OH － The ions break the bonds of the glassy components (amorphous silica and alumina) in the blast furnace slag, promoting their dissolution. The dissolved slag components form hydration products such as C-S-H gel (calcium silicate hydrate gel) in the presence of hydroxide ions, which contribute to the development of strength in the hardened body.

[0078] As in the case of ground granulated blast furnace slag, sodium carbonate or potassium carbonate generates hydroxide ions (OH － ) promotes the dissolution of amorphous silica and aluminosilicates in pozzolanic materials such as fly ash, thereby activating the pozzolanic reaction of the pozzolanic material and making the reaction with calcium hydroxide more efficient.

[0079] Sodium carbonate is provided by other components of the one-part geopolymer composition. ２＋ By bonding with ions, carbon can be fixed in the hardened geopolymer. ２ If sodium carbonate produced in the one-part geopolymer composition is used, the one-part geopolymer composition of the present invention will have even lower carbon content due to carbon fixation.

[0080] As the addition rate of sodium carbonate increases, the amount of carbon fixed in the hardened body increases, but if the addition rate is too high, the strength of the hardened body may decrease, as shown in Figure 7. ３ This is thought to be because the formation of consumes calcium and suppresses the production of geopolymer gel (C-A-S-H gel) or calcium silicate hydrate (C-S-H gel). The sodium carbonate addition rate is preferably 5 to 30% by mass, more preferably 8 to 15%.

[0081] When alkali metal silicates such as sodium metasilicate are dissolved in water, they exhibit strong alkalinity and produce hydroxide ions (OH － ) and silicate ions (SiO ３ ２－ ) is released. －The ions effectively break the network bonds (Si-O-Si bonds and Al-O-Al bonds) of the amorphous glass phase (mainly oxides of calcium, aluminum, and silicon) in blast furnace slag or pozzolanic materials (e.g., fly ash), and the component ions (Ca ２＋ , Al ３＋ , Si(OH) ４ This dissolution is the first step in the hydration reaction and contributes greatly to the solidification of these powders and the rapid development of strength. It also dramatically accelerates the dissolution of silicic acid and alkali ions (Na metasilicate, etc.). ＋ By supplying NASH gel, the production of geopolymer gel (NASH gel) can be accelerated and a denser hardened body can be formed.

[0082] Alkali metal orthosilicates, such as sodium orthosilicate, react in water with hydroxide ions (OH － ) is produced in abundance, which makes it very alkaline (Na ４ SiO ４ +H ２ O → 4Na ＋ +H ３ SiO ４ － +OH － ). This high concentration of OH － The ions are mixed with the aluminosilicate glass phase (amorphous SiO ２ and Al ２ O ３ ) surface and efficiently cut the skeletal structure (Si-O-Si bond and Al-O-Si bond). ２＋ ), aluminum (Al ３＋ ), silicon (Si ４＋ ) into the solution, accelerating the early geopolymer reaction or hydration reaction significantly. Sodium orthosilicate is not just an alkaline stimulant, but also acts as a silicic acid (SiO ２ ) also serves as a source of

[0083] Sodium bicarbonate (baking soda, NaHCO ３When dissolved in water, bicarbonates of alkali metals such as sodium bicarbonate exhibit weak alkalinity, making it difficult to significantly promote the hardening of blast furnace slag by themselves, and virtually impossible to induce the geopolymer reaction of fly ash. Therefore, sodium bicarbonate has not been used as an alkaline activator (alkaline stimulant) for geopolymers. However, by using other stronger alkaline stimulants (calcium hydroxide, sodium carbonate, sodium silicate, sodium hydroxide, etc.) in sufficient combination, the amorphous structure of the first powder component, such as ground blast furnace slag or fly ash, is destroyed, and once the hardening reaction of the geopolymer begins, sodium bicarbonate acts as a catalyst to dissolve the Ca provided by the first and second powder components of the one-part geopolymer composition. ２＋ It can bind with ions and fix carbon in the hardened geopolymer. ３ The formation of crystals may contribute to improving certain physical properties of the hardened geopolymer. ２ If the baking soda produced in the above step is used in one-part geopolymers, the one-part geopolymers of the present invention can be further reduced in carbon dioxide by fixing carbon.

[0084] The one-part geopolymer composition of the present invention can be made from a powder mixture of one or more of gypsum, alkali metal carbonates, bicarbonates, metasilicates, and orthosilicates, which improves the cured performance and provides carbon fixation. The alkali metal carbonates, bicarbonates, metasilicates, and orthosilicates are not limited to anhydrous forms, and may also be hydrates of these salts, such as sodium metasilicate nonahydrate and sodium carbonate monohydrate, heptahydrate, and decahydrate.

[0085] Adding alkali metal metasilicates or orthosilicates tends to shorten the setting time but results in high strength of the hardened geopolymer. Using alkali metal carbonates or bicarbonates may result in slightly lower strength of the hardened geopolymer, but the setting time is longer. Furthermore, captured CO2 can be used to produce alkali metal carbonates and bicarbonates. To lengthen the setting time and achieve a lower carbon dioxide content, it is preferable to use alkali metal carbonates and bicarbonates, or a mixture of both, as the third powder component. On the other hand, when strength of the hardened geopolymer is important or in low-temperature environments, using alkali metal metasilicates or orthosilicates as the third powder component is preferred, but adding alkali metal carbonates and bicarbonates, or both, can help achieve both the desired strength and setting time.

[0086] In addition, either or both of metallic silicon powder and metallic aluminum powder may be added to the one-part geopolymer composition of the present invention as a foaming agent. By adding these foaming agents, a porous geopolymer hardened body can be produced.

[0087] When water is added to the one-part geopolymer composition of the present invention, a hardening reaction occurs. Therefore, the one-part geopolymer composition of the present invention is a dry powder mixture that does not contain water before use. The components must be dried before mixing. The drying process can be carried out before or after the grinding process to produce the powder. However, the water-containing powder obtained by grinding may form lumps when dried. In addition, the powder has a lower CO2 content in the air than the powder before grinding. ２ Since there are more sites of contact with the calcium hydroxide, much of the calcium oxide or hydroxide in the raw material may become calcium carbonate. Therefore, a drying treatment before the milling operation is preferred.

[0088] In addition, the drying treatment of compositions containing calcium oxide or calcium hydroxide, such as steelmaking slag, fine powder of waste concrete, solidified raw concrete sludge, lime-based concrete expansive additives, etc., can be carried out using CO ２To avoid contact with CO, the drying method is reduced pressure (vacuum), drying in an inert gas atmosphere, closed dryer, or dehumidifier and CO ２ This may be accomplished by one or more dry room methods with removal filters, and the storage of the raw material prior to milling and blending with the other components of the one-part geopolymer composition may be accomplished in a sealed environment.

[0089] Below, as additional examples, the type of first powder component, the fineness and mixing ratio of each, and the types of the second and third powder components are changed. Strength test results of one-part geopolymer compositions are shown.

[0090] (1) Materials Used In addition to gypsum-free JIS 4000-grade ground granulated blast furnace slag (BFS) and gypsum-containing JIS 4000-grade ground granulated blast furnace slag (gBFS) shown in Table 1, gypsum-free JIS 6000-grade ground granulated blast furnace slag and JIS 8000-grade ground granulated blast furnace slag were used. The three types of BFS were obtained from the same steelworks. The 6000-grade and 8000-grade BFS have the same density and chemical composition as the 6000-grade BFS, as shown in Table 1. The basicity of all three types is 1.81. However, the specific surface area (Blaine value) of the 6000-grade and 8000-grade BFS is 6105 cm², respectively. ２ / g and 8500 cm ２ / g. In addition to the JIS II type fly ash (FA) shown in Table 1, JIS I type fly ash was also used. The JIS I type fly ash has a specific surface area (Blaine value) of 6370 cm ２ / g, and silicon dioxide (SiO ２ ) 61.6%, aluminum oxide (Al ２ O ３ ) 24.6%, calcium oxide (CaO) 1.3%, iron oxide (Fe ２ O ３ The second powder component was obtained by classifying the previously mentioned recycled fine powder WC3 to obtain recycled fine powder (WCp) of 0.075 mm or less. TG-DTA analysis revealed that the Ca(OH) ２ The steelmaking slag used had a density of 3.34 g / cm ３The alkalinity (pH) of the filtrate immersed in neutral water at a mass ratio of 1:10 was 12.8. The Blaine value of the fine powder obtained by pulverizing in a mill was 4000 m ２ The results were about / g. ２ The content was 6.54% (by TG-DTA analysis). The chemical composition of the ground steel slag is shown in Table 5. As a third powder component, in addition to sodium carbonate, sodium bicarbonate (NaHCO ３ The powdered sodium bicarbonate reagent used in this experiment had a purity of 95-98% and a density of 2.2 g / cm ３ The fine aggregate used to prepare the mortar was sea sand in a surface-dried state, and was mixed at 200% of the total powder mass. Tap water was added at 50% or 55% of the total powder mass.

[0091]

[0092] (2) Mixing of one-part geopolymer composition and compressive strength of mortar The mixing of the one-part geopolymer composition is shown in Table 6. Mortar was mixed using the above-mentioned mixing method to prepare compressive strength specimens, which were then sealed and cured for 28 or 91 days in air at 20±3°C. The compressive strength was then measured. The compressive strength was calculated by averaging the test results of six pieces of the bending strength test of three rectangular columns. In Table 6 and the following description, the first powder component, second powder component, and third powder component are referred to as the first powder, second powder, and third powder.

[0093]

[0094] The results of Examples 1 to 3 show that the first powder, which is ground granulated blast furnace slag alone or a mixed powder of ground granulated blast furnace slag and fly ash, can be used to prepare a hardened body by adding water to the second powder. The strength of the hardened body is 20 N / mm ２ Below, the normal strength of concrete is 21 N / mm ２ Although it does not satisfy the above requirements, it can be used in non-load-bearing areas.

[0095] The results of Examples 4 and 5 show that the greater the proportion of ground granulated blast furnace slag in the first powder, the stronger the hardened body. The results of Examples 6, 7, and 8 show that when sodium carbonate powder is added as the third powder and the alkaline irritation is high, the lower the proportion of recycled fine powder added as the second powder, the higher the strength of the mortar. ２ This is because components other than the above (i.e., residues after the reaction) become weak points in the hardened body. The higher the content of recycled fine powder, the more such weak points there are. Comparing the results of Examples 7 and 10, the sodium carbonate content of 8% is better than that of 10%. CaCO ３ The large amount of β-glucan is generated to suppress the formation of geopolymer gel. The results of Example 9 indicate that a mixed powder of WCp and SS can also be used as the second powder. Furthermore, the results of Example 11 indicate that a hardened body can be produced using WCp as the second powder and sodium bicarbonate as the third powder, and carbon can be fixed in the hardened body. Comparing the results of Examples 4 and 14, increasing the fineness of the ground granulated blast furnace slag increases the strength of the mortar, even when the sodium carbonate content is high. The results of Examples 12 and 13 also show a tendency for the strength of the hardened body to increase with increasing fineness of the ground granulated blast furnace slag. The results of Examples 15 to 23 also indicate that ground granulated blast furnace slag can be used alone as the first powder, that sodium bicarbonate can be used alone as the third powder when steelmaking slag powder is used as the second powder, that adding sodium carbonate powder to sodium bicarbonate to form the third powder increases the strength of the hardened body, and that the strength of the hardened body is further increased when gypsum is used in combination with either or both sodium bicarbonate and sodium carbonate. Furthermore, based on the results of using gypsum in combination with either sodium bicarbonate or sodium carbonate, or both, it can be inferred that gypsum can accelerate the reaction and can be used alone as a third powder. These mortars have the strength required for practical use in construction work, and by further mixing with coarse aggregate, they can be used to produce practical concrete.

[0096] In the above examples, water was added to the one-part geopolymer composition of the present invention, and the composition was kneaded and cured at room temperature to produce a hardened product. To improve the performance of the geopolymer before and after hardening, an aqueous solution (water) containing additives can be used in the mixing water, as in PC concrete. Aqueous solutions (water) containing one or more of the following substances can be prepared in advance: a set retarder to extend the setting time, a set accelerator to shorten the setting time and accelerate hardening, a surfactant to increase fluidity before hardening, a thickener to increase viscosity before hardening or reduce bleeding, an air-entraining agent (AE agent) to ensure the frost resistance of the hardened product, a shrinkage-reducing agent to suppress drying shrinkage of the hardened product, an antifreeze agent to prevent initial frost damage of the hardened product, hydrogen peroxide water used as a foaming agent, and an additive (e.g., triethanolamine) to increase the reactivity of ground blast furnace slag or pozzolanic materials can be dissolved in water.

[0097] Examples of setting retarders include: (1) oxycarboxylic acid compounds such as gluconic acid, citric acid, tartaric acid, and malic acid; (2) lignin sulfonates and derivatives thereof; (3) monosaccharides, disaccharides, and trisaccharides such as sucrose (cane sugar), glucose, fructose, maltose, and raffinose; and (4) phosphates, copper hydroxide, zinc compounds, and lead compounds.

[0098] Examples of setting accelerators include calcium formate, aluminum sulfate, calcium thiocyanate, calcium nitrite, calcium nitrate, sodium sulfate, and potassium sulfate.

[0099] The surfactants include calcium lignosulfonate, sodium lignosulfonate, organic compounds having a hydroxyl group and a carboxyl group such as gluconates and citrates, naphthalenesulfonic acid-formalin condensates, melaminesulfonic acid-formalin condensates, and polymeric compounds having a polycarboxylic acid main chain and an ether group such as polyethylene glycol on the side chain.

[0100] Examples of thickeners include cellulose-based thickeners containing methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), carboxymethylcellulose (CMC), etc.; biopolymer-based thickeners containing welan gum, gellan gum, xanthan gum, etc.; glycol-based thickeners; and polyacrylamide-based thickeners.

[0101] Air entraining agents include resin acid salts such as rosin acid and abietic acid, alkylarylsulfonate salts such as sodium alkylbenzenesulfonate, and alkyl sulfate salts such as sulfated salts of long-chain alcohols.

[0102] Examples of shrinkage reducing agents include polyethers such as polypropylene glycol (PPG) and derivatives thereof, and products in which alkylene oxides such as ethylene oxide and propylene oxide are added to lower alcohols (methanol, ethanol, etc.).

[0103] As the antifreeze agent, calcium nitrate, sodium nitrate, calcium nitrite, calcium chloride, and alcohols such as ethylene glycol, propylene glycol, and methanol can be used.

[0104] In the above examples, mortar using the one-part geopolymer composition of the present invention was sealed and cured in air at room temperature (20±3°C). The higher the curing temperature, the higher the reactivity of pozzolanic materials such as ground granulated blast furnace slag and fly ash. In particular, increasing the curing temperature allows the latent hydraulic properties of ground granulated blast furnace slag and the pozzolanic reactivity of pozzolanic materials to be developed earlier and more efficiently. For this reason, although normal pressure curing at 5 to 40°C is acceptable, from the perspective of strength development of the hardened body, normal pressure curing at 40°C or higher is preferred, and high-temperature, high-pressure steam curing in an autoclave is more preferred.

[0105] The hardened body can be produced by air curing, water curing, or steam curing. However, when cured in water, alkali metal carbonates, bicarbonates, metasilicates, orthosilicates, and hydrates of these salts, as well as free lime in steelmaking slag, may dissolve into the water, potentially impairing the strength development of the one-part geopolymer of the present invention. Therefore, atmospheric air curing and high-temperature, high-pressure steam curing are preferred.

[0106] When air curing at normal pressure, water evaporates from the geopolymer, causing the hardened body to dry and shrink, and if it dries too much due to heating, the powder reaction may stop. Therefore, when air curing at normal pressure and room temperature or air curing at normal pressure and temperature, sealing the hardened body is recommended. In order to obtain high strength in a short period of time, autoclave curing is preferable.

[0107] Adding water or the aqueous solution (moisture) to the one-part geopolymer composition of the present invention can produce a hardened paste. Adding fine aggregate can produce mortar as in the previous examples. Mixing coarse aggregate with mortar can produce concrete. Examples of aggregates include natural aggregates such as river sand and gravel, sea sand and gravel, land sand and gravel, mountain sand and gravel, and silica sand, crushed rocks, and industrial waste and by-products such as slag aggregate, including blast furnace slag aggregate, copper slag aggregate, electrooxidation furnace slag aggregate, ferronickel aggregate, molten slag aggregate from municipal waste incineration ash, recycled aggregate, clinker ash, and artificial lightweight aggregate. It is preferable to use aggregates that meet the respective JIS standards.

[0108] In addition, in order to improve the performance of the hardened one-part geopolymer composition, particularly tensile strength, flexural strength, elongation capacity and toughness, reinforcing materials such as steel fiber, glass fiber, polypropylene fiber, carbon fiber, aramid fiber, polyolefin fiber, vinylon fiber and cellulose fiber may be mixed into the one-part geopolymer composition of the present invention.

Claims

1. A first powder component which is at least one powder selected from ground granulated blast furnace slag, fly ash, biomass combustion ash, silica fume, and volcanic ash; and a second powder component which is at least one powder selected from ground granulated blast furnace slag, fly ash, biomass combustion ash, silica fume, and volcanic ash. ２ a second powder component, the second powder component being a powder containing 2. A composition for one-part geopolymer according to claim 1, wherein a portion of the first powder component is replaced with at least one powder selected from the group consisting of stone powder, slowly cooled blast furnace slag powder, fluidized bed coal ash, metakaolin, copper slag powder, red mud, calcined clay other than metakaolin, sewage sludge incineration ash molten slag powder, municipal waste incineration ash molten slag powder, and perlite powder.

3. The composition for one-part geopolymer according to claim 1, wherein the second powder component is at least one powder selected from crushed concrete having a particle size of 0.63 mm or less, dry powder of fresh concrete sludge, and steel slag powder.

4. A composition for one-part geopolymer described in claim 1, wherein the content of the second powder component is 10% by mass or more and 40% by mass or less in terms of the total amount of the first powder component and the second powder component, which is 100% by mass.

5. The composition for one-part geopolymer according to claim 1, further comprising a third powder component, which is at least one powder selected from alkali metal carbonates, alkali metal bicarbonates, alkali metal metasilicates, alkali metal orthosilicates, and hydrates of these salts.

6. A composition for one-part geopolymer described in claim 1, wherein the addition rate of the third powder component is 5% by mass or more and 30% by mass or less relative to 100% by mass of the total amount of the first powder component and the second powder component.

7. A one-part geopolymer hardened body obtained by adding water or water that does not contain alkali metal silicate and alkali metal hydroxide to the composition for one-part geopolymer described in any one of claims 1 to 6.

8. A one-part geopolymer hardened body obtained by adding water or water not containing alkali metal silicate and alkali metal hydroxide, and aggregate or aggregate and fiber to the composition for one-part geopolymer described in any one of claims 1 to 6.

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