Geopolymer composition

Abstract

To provide a geopolymer composition that enables utilization of glass polishing waste as an active filler.SOLUTION: A geopolymer composition comprises an active filler and an alkali activator, wherein the active filler includes glass polishing waste. The active filler may further contain aluminum hydroxide. The active filler may also contain blast furnace slag. The alkali activator preferably has a molar ratio A / W of sodium hydroxide to water within a range of 0.06 to 0.30.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a geopolymer composition comprising an active filler and an alkaline activator. [Background technology]

[0002] In recent years, global warming caused by carbon dioxide (CO2) emissions has progressed rapidly and become a social problem. CO2 emissions from the cement industry account for a large proportion of this problem. Currently, the cement that is industrially produced on a large scale is Portland cement (JIS A 5210), whose main raw material is limestone. Limestone is primarily composed of calcium carbonate (CaCO3), which decomposes into calcium oxide (CaO) at approximately 900°C when fired, simultaneously emitting CO2. For this reason, the geopolymer method has attracted attention as a technology for producing concrete without using Portland cement, with the aim of reducing CO2 emissions and making effective use of industrial waste.

[0003] Geopolymer is a material defined as "a material that does not use cement clinker, but is hardened using a raw material (active filler) whose main component is amorphous aluminum silicate and at least one of an aqueous solution of alkali metal silicate, carbonate, or hydroxide." Fly ash, metakaolin, blast furnace slag, etc. are generally used as active fillers, and various developments are underway, including as a concrete substitute, ion adsorbent, and building material.

[0004] Conventional geopolymer compositions are made from a filler containing either fly ash, blast furnace slag, sewage incineration sludge or metakaolin, an alkali activator containing either potassium hydroxide, sodium hydroxide, sodium silicate or potassium silicate, and aggregate (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-239446 Summary of the Invention [Problem to be solved by the invention]

[0006] Glass shavings are generated as a by-product during the glass polishing process, and recycling of this shavings is desired. Compared to fly ash, glass shavings contain more amorphous components and less aluminum, so it is unclear whether they can be used as a geopolymer active filler. Furthermore, if they can be used, the optimal blend is unknown, so it is necessary to determine whether they can be used and the optimal blend.

[0007] The object of this invention is to provide a geopolymer composition that can utilize glass grinding as an active filler. [Means for solving the problem]

[0008] The present invention solves the above problems by the means described below. The invention of claim 1 is a geopolymer composition comprising an active filler and an alkaline activator, wherein the active filler comprises glass grinding dust.

[0009] The invention of claim 2 is a geopolymer composition according to claim 1, characterized in that the active filler contains aluminum hydroxide.

[0010] The invention of claim 3 is a geopolymer composition according to claim 1, characterized in that the active filler contains blast furnace slag.

[0011] The invention of claim 4 is a geopolymer composition according to claim 1, characterized in that the alkaline activator has a molar ratio A / W of sodium hydroxide to water in the range of 0.06 to 0.30. [Effects of the Invention]

[0012] According to the present invention, glass grinding dust can be used as the active filler. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a process diagram showing the production procedure for geopolymer compositions of examples and comparative examples of this invention. [Figure 2] 1 is a graph showing the relationship between A / W and compressive strength in examples of the present invention and comparative examples. [Figure 3] 1 is a graph showing the relationship between Si / A and compressive strength in examples of the present invention and comparative examples. [Figure 4] 1 is a graph showing the relationship between W / P and compressive strength in examples of the present invention and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (Geopolymer composition) The geopolymer composition according to an embodiment of the present invention is made from an active filler, an alkali activator, and aggregate. The geopolymer composition is hardened by reacting with alkali to crosslink and polymerize silicate complexes (SiO4), resulting in a hardened geopolymer. This embodiment may also contain sodium gluconate, water, etc.

[0015] (active filler) The activated filler is a powder (powder raw material) that is activated by an alkaline activation solution and polymerizes and solidifies. In this embodiment, the activated filler includes glass grinding dust and blast furnace slag. In this embodiment, the activated filler may also include aluminum hydroxide, silica fume, etc.

[0016] Glass abrasive scrap (hereinafter referred to as GAS (glass abrasive scrap)) is a by-product produced during the glass grinding process. Since glass abrasive scrap contains less aluminum than fly ash, which is commonly used as an active filler, it can be used as a substitute for fly ash by adding aluminum.

[0017] Blast furnace slag (hereinafter sometimes referred to as BFS) is a by-product obtained during the refining of iron in a blast furnace. Blast furnace slag is a substance formed by combining non-iron components such as silica contained in iron ore and ash from coke, which is used as a reducing agent, with limestone, an auxiliary raw material. The main components of blast furnace slag are calcium oxide (CaO), silicon dioxide (SiO2), and alumina (Al2O3). Blast furnace slag is standardized under JIS A 6206. Blast furnace slag is an amorphous substance, and the calcium contained in this slag reacts in the geopolymer composition to produce calcium silicate hydrate (CSH), which hardens. For these reasons, the blast furnace slag contained in the geopolymer composition has excellent reactivity.

[0018] In this embodiment, aluminum hydroxide (hereinafter, sometimes referred to as AH) may be included as the active filler. When glass grinding swarf is included as the active filler, the aluminum hydroxide can be effectively utilized when used as a fly ash substitute, since the glass grinding swarf contains a large amount of amorphous components and a relatively small amount of aluminum components. For example, scrap material from Shinkansen bullet trains (registered trademark) can be used as the aluminum hydroxide. In this embodiment, gibbsitic aluminum hydroxide with a monoclinic crystal structure is used as the aluminum hydroxide.

[0019] In this embodiment, silica fume (hereinafter, sometimes referred to as SF) may be included as an active filler. Silica fume is a by-product obtained by collecting dust from exhaust gases generated during the production of ferrosilicon, metallic silicon, electrolytic zirconia, and other materials. SF is an amorphous spherical microparticle primarily composed of silicon dioxide (SiO2), and its components are specified in JIS A 6207. Silica fume is used as a source of silicate monomer. The SiO2 contained in silica fume is gradually dissolved in alkali, gradually producing silicate monomer (Si(OH)4), which contributes to the hardening of the geopolymer composition. This allows for a longer setting time for the geopolymer composition compared to when alkali silicates are used as the silicon source.

[0020] (Alkaline activator) The alkaline activator is a solution used to knead the filler and aggregate. The alkaline activator is a substance that dissolves in water and exhibits strong alkalinity. Examples of alkaline activators include water glass (sodium silicate solution or potassium silicate solution), potassium hydroxide (KOH) solution, sodium hydroxide (NaOH) solution, and sodium metasilicate powder. The alkaline activator activates the aluminosilicate contained in the filler upon contact with it, eluting cations such as Al ions and Si ions. In this embodiment, sodium hydroxide is used from the perspectives of ensuring usable time, preventing cracking, and ease of on-site construction work.

[0021] (aggregate) Aggregates commonly used in concrete or mortar are used. Aggregates are classified as fine or coarse aggregates based on particle size, as natural or artificial aggregates based on origin, and as lightweight, normal, or heavy aggregates based on density. Lightweight aggregates are preferred for lightweight construction, while fine aggregates are classified as lightweight, normal, or heavy aggregates based on density, and can be selected appropriately depending on the application of the geopolymer hardened material. Silica sand, for example, is used as a fine aggregate. Silica sand is a sand-like material whose main component is silicon dioxide (SiO2). JIS-standard products and mixed silica sand with particle size adjusted according to JIS standards are used as silica sand.

[0022] (Sodium gluconate) Sodium gluconate is used as a set retarder (a retarding fluidizer). When included in geopolymer compositions, sodium gluconate delays the setting of the geopolymer composition, extending its usable life and providing favorable workability.

[0023] (Other ingredients) The geopolymer composition according to this embodiment may contain other components. The other components may include, but are not limited to, conventional components used in concrete, such as fluidizers, shrinkage reducing agents, rust inhibitors, waterproofing agents, antifoaming agents, dust reducing agents, pigments, etc.

[0024] The geopolymer composition according to the embodiment of the present invention has the following effects. (1) In this embodiment, glass shavings are used as an active filler. Therefore, glass shavings, which are generated as a by-product during the glass grinding process, can be used as an active filler to produce a high-strength hardened geopolymer body.

[0025] (2) In this embodiment, aluminum hydroxide is included as an active filler. Therefore, when glass grinding dust, which is rich in amorphous components and relatively low in aluminum components, is used as a substitute for fly ash, the aluminum hydroxide waste can be effectively utilized.

[0026] (3) In this embodiment, blast furnace slag is used as an active filler. Therefore, by adding blast furnace slag instead of aluminum hydroxide or by adding blast furnace slag together with aluminum hydroxide, a high-strength hardened geopolymer body can be produced. [Example]

[0027] Next, an embodiment of the present invention will be described.

[0028] [Table 1]

[0029] [Table 2]

[0030] Table 1 shows the starting materials used in the examples and comparative examples. Table 2 shows the main chemical components of the glass grinding dust used in the examples in comparison with fly ash. The glass grinding dust shown in Table 1 is a material generated during the grinding process of architectural plate glass. It is characterized by its boron- and lead-free content, high alkali content, consistent composition, and absence of impurities, making it an unused resource. The glass grinding dust had a volume mean diameter of 8.489 μm, a number mean diameter of 1.164 μm, and an area mean diameter of 3.791 μm, which was not significantly different from the volume mean diameter of 7.127 μm, number mean diameter of 1.525 μm, and area mean diameter of 3.989 μm for ordinary Portland cement (see Chuken Consultants' website). As shown in Table 2, chemical composition analysis of the major components using X-ray fluorescence analysis (XRF) revealed higher concentrations of Na and Ca and lower concentrations of Al compared to fly ash. Powder X-ray diffraction (XRD) analysis of the glass grinding dust shown in Tables 1 and 2 confirmed that the main crystalline component was quartz (SiO2). Standard cement sand used for cement strength tests was used as fine aggregate.

[0031] [Table 3]

[0032] Table 3 shows the formulations of the geopolymer compositions of the examples and comparative examples. The A / W ratio shown in Table 3 is the molar ratio of the alkaline component to water in the used solution. Si / A is the molar ratio of silicon in the silica fume to the alkaline component in the solution. W / P is the volume ratio of pure water component to powder (glass grinding dust + blast furnace slag powder + aluminum hydroxide), and is defined as a concept equivalent to the water-cement ratio in general cement mortar.

[0033] [Table 4]

[0034] Table 4 shows the characteristics of the geopolymer compositions of the examples and comparative examples. Using the glass grinding dust shown in Table 1 as the starting material, various geopolymers of Examples 1 to 15 and Comparative Examples 1 to 6 shown in Tables 3 and 4 were produced, and the usability of the glass grinding dust and the effects of adding aluminum hydroxide were confirmed.

[0035] FIG. 1 is a process diagram showing the procedure for producing the geopolymer compositions of the examples and comparative examples. The geopolymer composition was prepared using a melting method, in which SF was added as a silicon component instead of water glass during mixing. The melting method exhibited similar strength development in the range of blast furnace slag (BFS) content compared to the conventional method using water glass (the conventional method). Figure 2 shows the manufacturing procedure for the geopolymer mortar prepared in this study. Glass abrasive dust (GAS), aluminum hydroxide (AH), blast furnace slag (BFS), silica fume (SF), and fine aggregate cement standard sand (S) were mixed and stirred in a mortar mixer or concrete mixer, followed by the addition of sodium hydroxide (NH) solution and stirring. The set retarder sodium gluconate (GNa) was added and stirred to complete the mixing. After confirming the fresh properties of the prepared fresh mortar, it was filled into a φ5cm x 10cm mold, sealed, and heated to 80°C over 4.5 hours, held at 80°C for 10 hours, and cooled to 30°C over 4.5 hours.

[0036] [Table 5]

[0037] Table 5 shows the test results for the fresh properties and strength of the geopolymer compositions of the Examples and Comparative Examples. The flow values ​​shown in Table 5 are measurements of the geopolymer mortars of Examples 1-15 and Comparative Examples 1-6 after conducting the flow test specified in JIS R 5201. 0 hits represents the spread of the mortar immediately after lifting the mortar flow cone vertically, and 15 hits represents the spread after dropping the flow table 15 times at a rate of 1 hit per second. The flow value is measured in mm from the length of the most spread part of the mortar to the part perpendicular to this direction. The higher the flow value (the greater the spread), the softer the mortar.

[0038] The compressive strength is the measured value when the geopolymer mortar of Examples 1 to 15 and Comparative Examples 1 to 6 was applied to a size of φ5 cm x 10 cm and a compressive strength test was conducted in accordance with JIS A 1108. The splitting tensile strength is the measured value when the geopolymer mortar of Examples 1 to 15 and Comparative Examples 1 to 6 was applied to a size of φ5 cm x 10 cm and a splitting tensile strength test was conducted in accordance with JIS A 1132, as with the compressive strength.

[0039] As shown in Table 5, in Examples 1, 5, 6, 9, 10, 11, and 13, in which aluminum hydroxide was added, a geopolymer hardened body with higher strength was obtained compared to Examples 2 and 4, in which aluminum hydroxide was not added. As a result, it was confirmed that the addition of aluminum hydroxide makes it possible to produce a geopolymer hardened body with even higher strength.

[0040] For Examples 1 to 15, it was confirmed that by adding blast furnace slag, high-strength hardened geopolymer bodies could be produced using the melting method, just like the hardened geopolymer bodies produced from fly ash. Furthermore, for Examples 2 and 4, which did not contain aluminum hydroxide, it was confirmed that adding blast furnace slag could produce high-strength hardened geopolymer bodies.

[0041] On the other hand, sufficient compressive strength could not be obtained in Comparative Examples 2, 3, and 5, in which amorphous aluminum hydroxide was added. Furthermore, in Comparative Examples 1 to 6, the flow values ​​tended to be lower overall compared to Examples 1 to 15, and it was confirmed that the formulations were difficult to knead.

[0042] Fig. 2 is a graph showing the relationship between A / W and compressive strength for Examples and Comparative Examples. Fig. 3 is a graph showing the relationship between Si / A and compressive strength for Examples and Comparative Examples. Fig. 4 is a graph showing the relationship between W / P and compressive strength for Examples and Comparative Examples. As shown in Figs. 2 to 4, Examples 1 to 15 were able to achieve sufficient compressive strength compared to Comparative Examples 1 to 6. For example, concrete used in railway PC (prestressed concrete) sleepers is specified as having a compressive strength of 49.1 MPa or more (JIS E1201, E1202), and in the civil engineering field, it is sometimes used with a compressive strength of around 30 MPa. Although the compressive strength varies depending on the field of use and application, Examples 1 to 15 were confirmed to have sufficient compressive strength.

[0043] As shown in Figure 2, it was confirmed that by keeping the molar ratio (A / W) of sodium hydroxide to water in the range of 0.06 to 0.30, sufficient compressive strength can be obtained even if the A / W is lower than when fly ash is added. As shown in Figure 3, it was confirmed that the strength generally increases as the molar ratio (Si / A) of the silicon in the silica fume to the alkaline component in the solution increases. As shown in Figure 4, it was confirmed that the strength tends to increase as the amount of powder (glass polishing chips + aluminum hydroxide + granulated blast furnace slag) volume ratio (W / P) increases.

[0044] From the above, it was confirmed that geopolymers can be produced using glass grinding waste and aluminum hydroxide waste as active fillers. It was also confirmed that a geopolymer with sufficient compressive strength can be obtained by using glass grinding waste with aluminum hydroxide added as an aluminum component and blast furnace slag as active fillers.

[0045] The present invention is not limited to the above-described embodiment, and various modifications and alterations are possible as described below, and these are also within the scope of the present invention. In this embodiment, an example has been described in which silica fume is added as the active filler, but it is also possible to add coal ash such as clinker ash, or industrial waste containing glass components such as sewage incineration sludge.

Claims

1. A geopolymer composition comprising an active filler and an alkaline activator, the active filler comprises glass grinding; A geopolymer composition comprising:

2. 2. The geopolymer composition of claim 1, the active filler comprises aluminum hydroxide; A geopolymer composition comprising:

3. 2. The geopolymer composition of claim 1, the active filler comprises blast furnace slag; A geopolymer composition comprising:

4. 2. The geopolymer composition of claim 1, The alkaline activator has a molar ratio (A / W) of sodium hydroxide to water in the range of 0.06 to 0.30; A geopolymer composition comprising:

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