Geopolymer composition

Abstract

Provided is a geopolymer composition comprising a powder component, water, and an alkali source, wherein the powder component comprises at least any one of a blast furnace slag fine powder and fly ash, the alkali source comprises at least an alkali silicate salt, the molar ratio of alkali metal ions contained in the alkali source to the water, i.e., AL / W, is less than 0.100, and the molar ratio of silicon ions contained in the alkali source to the water, i.e., Si / W, is 0.035-0.085.

Description

Geopolymer composition

[0001] The present invention relates to improving the strength development and freshness of geopolymers.

[0002] Compared to hardened cement, geopolymers have less CO2 during production. ２ It has attracted attention as a construction material with low emissions and excellent acid resistance, heat resistance, etc. In recent years, the mainstream has been to use part of ground granulated blast furnace slag as the powder raw material and alkali silicate as the alkali source due to its high early strength development.

[0003] On the other hand, when sodium silicate is used, depending on the blending conditions, the viscosity increases, which can deteriorate the fresh properties and cause poor application during driving (Non-Patent Document 1).

[0004] Patent No. 5091519

[0005] Kazuo Ichinomiya et al., 2021 Priority Research Project Report: "Research on Infrastructure Construction in a Low-Carbon Society Using New Alkali-Activated Materials," Japan Society of Civil Engineers, Concrete Committee, "Research Subcommittee on Infrastructure Construction in a Low-Carbon Society Using New Alkali-Activated Materials (233 Committee)," pp. 2-5, 2021.3. Motoki Uehara et al., Mixing, Manufacturing Methods, and Properties of Geopolymer Hardened Bodies, Proceedings of the Annual Meeting of the Japan Concrete Institute, Vol. 37, No. 1, 2015.

[0006] The geopolymer composition described in Patent Document 1, which has an alkali / water molar ratio of 0.1 or more, has high viscosity, which reduces fresh properties and causes poor application when used in concrete.

[0007] On the other hand, as described in Non-Patent Document 2, the alkali / water molar ratio has a large effect on strength, and if it is less than 0.1, it is thought that strength development at room temperature will decrease.

[0008] The present invention has been made based on the above circumstances, and its object is to provide a geopolymer composition that can reduce viscosity while maintaining sufficient early strength development and has good fresh properties.

[0009] The inventors conducted extensive research to easily obtain geopolymer compositions with improved fresh properties and compressive strength. As a result, they discovered a composition range for geopolymer compositions using alkali metal silicates that reduces viscosity and has good fresh properties while maintaining a predetermined initial strength, leading to the completion of the present invention. Specifically, they discovered that a geopolymer composition with sufficient early strength and good fresh properties can be obtained by adjusting the molar ratio of alkali metal ions contained in the alkali source of the geopolymer composition to the water (AL / W) to less than 0.100 and the molar ratio of silicon ions contained in the alkali source to the water (Si / W) to 0.035 to 0.085.

[0010] That is, the present invention provides a geopolymer composition comprising a powder component, water, and an alkaline source, wherein the powder component comprises at least one of ground blast furnace slag or fly ash, and the alkaline source comprises at least an alkali silicate, and the molar ratio of alkali metal ions contained in the alkaline source to the water: AL / W is less than 0.100, and the molar ratio of silicon ions contained in the alkaline source to the water: Si / W is 0.035 to 0.085. This is a geopolymer composition.

[0011] In the geopolymer composition of the present invention, the alkali source preferably comprises an alkali metal silicate and an alkali metal carbonate.

[0012] Preferably, the alkali metal silicate is sodium silicate, and the alkali metal carbonate is sodium carbonate.

[0013] According to the geopolymer composition of the present invention, even if AL / W is less than 0.100, by setting Si / W to 0.035 to 0.085, the viscosity can be reduced, the fresh properties are good, and the initial strength expression at room temperature is also excellent. A geopolymer composition can be obtained.

[0014] Fig. 1 shows the relationship between AL / W and 15-ply mortar flow. Fig. 2 shows the relationship between Si / W and 15-ply mortar flow. Fig. 3 shows the relationship between Si / W and compressive strength at 1 day of age.

[0015] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. In this specification, "parts" and "%" are based on mass unless otherwise specified.

[0016] <Geopolymer composition> The geopolymer composition of the present invention is a geopolymer composition comprising a powder component, water, and an alkali source, wherein the powder component comprises at least one of ground blast furnace slag or fly ash, and the alkali source comprises at least an alkali silicate, wherein the molar ratio of alkali metal ions contained in the alkali source to the water: AL / W is less than 0.100, and the molar ratio of silicon ions contained in the alkali source to the water: Si / W is 0.035 to 0.085. The geopolymer composition of the present invention has sufficient early strength development and good fresh properties.

[0017] Here, the early strength in the present invention means the compressive strength on the first day of age based on a compressive strength test performed in accordance with the compressive strength test method described in JIS A 1108. The early strength of the geopolymer composition of the present invention is preferably a strength that allows it to be removed from the formwork, for example, 10.0 N / mm ２ It is preferable that the strength is 12.0 N / mm or more. ２ More preferably, it is 14.0 N / mm or more. ２ More preferably, it is equal to or greater than this.

[0018] In addition, the fresh properties in the present invention can be evaluated, for example, by a 15-stroke mortar flow (fluidity) test in accordance with the mortar flow test described in JIS A 5201. From the viewpoint of workability, the 15-stroke mortar flow in the geopolymer composition of the present invention is preferably 160 mm or more, more preferably 170 mm or more, and even more preferably 180 mm or more.

[0019] (Fly ash) Fly ash is fine ash that is collected from the exhaust gas by a dust collector, among the ash by-products of combustion of coal and / or biomass fuel in a boiler of a thermal power plant or the like. ２ , Al ２O ３ Fly ash for concrete containing the above as a main component and specified as types I to IV according to JIS A 6201 based on particle size and flow value is preferred, and although the standard is not particularly limited, types I and II, which have a fine particle size and are highly reactive, are more preferred.

[0020] (Ground granulated blast furnace slag) Ground granulated blast furnace slag is produced when producing pig iron, and contains CaO, SiO ２ , Al ２ O ３ , MgO as the main component. Examples of ground granulated blast furnace slag include those containing 20% ​​by mass or more and 60% by mass or less of calcium, calculated as calcium oxide (CaO). In particular, the use of ground granulated blast furnace slag 4000 for concrete, as specified in JIS A 6206, is more preferable from the viewpoint of the strength development and shrinkage property at room temperature of the hardened geopolymer body produced using the resulting geopolymer composition.

[0021] In the geopolymer composition of the present invention, the powder component contains at least one of ground granulated blast furnace slag or fly ash, but preferably contains both ground granulated blast furnace slag and fly ash. The fly ash content relative to the total mass of the fly ash and ground granulated slag is preferably 50 to 90% by mass, and more preferably 60 to 85% by mass from the perspective of durability of the resulting hardened geopolymer composition. A content of 50% by mass or more is preferable from the perspective of maintaining good fluidity when mixed with water to form a geopolymer composition, making it easy to achieve sufficient workability, and also from the perspective of expanding the effective use of fly ash. Furthermore, a content of 90% by mass or less results in good strength development of the hardened geopolymer composition at an early age.

[0022] (Alkaline Source) The alkali source contains alkali metal ions (Li ＋ , Na ＋ , K ＋Typical examples of alkali metal salts include alkali metal silicates, alkali metal carbonates, and alkali metal hydroxides. In the geopolymer composition of the present invention, the alkali source contains at least an alkali metal silicate. A combination of an alkali metal silicate and an alkali metal carbonate is preferred because they have a relatively low heat of solution, do not adversely affect the mixing process, and can produce a hardened geopolymer composition with excellent compressive strength when cured at room temperature. The alkali source, such as an alkali metal silicate or alkali metal carbonate, may be in the form of a liquid or powder, or an anhydrous salt, hydrate, or aqueous solution. Powder is preferred for its ease of transport and application.

[0023] The alkali metal silicate powder is sodium silicate powder (SiO ２ / NaO ２ Examples of suitable powders include sodium silicate powder (SiO 2 ), potassium silicate powder, potassium metasilicate powder, and lithium silicate powder (molar ratio: about 1.95 to 3.4), and sodium metasilicate powder (type 1, type 2), potassium silicate powder, potassium metasilicate powder, and lithium silicate powder. Sodium silicate powder (SiO 2 ) is preferred because it has excellent strength and durability and is a relatively inexpensive powder material. ２ / NaO ２ Molar ratio: about 1.950 to 2.2, H ２ O=about 20% by mass is preferred.

[0024] The alkali metal carbonates include sodium carbonate (Na ２ CO ３ ), potassium carbonate (K ２ CO ３ ), lithium carbonate (Li ２ CO ３ Sodium carbonate powder is preferred because it is relatively inexpensive and has high reactivity with ground slag.

[0025] When an alkali metal silicate and an alkali metal carbonate are used in combination, the content of the alkali metal carbonate relative to the total mass of the alkali metal silicate and the alkali metal carbonate is preferably 5% by mass to 50% by mass.

[0026] The molar ratio AL / W of alkali metal ions (AL) to water (W), which constitutes the alkali source, is less than 0.100. If AL / W is 0.100 or more, the viscosity of the geopolymer composition increases, causing problems during the production of hardened geopolymer compositions. From the above viewpoint, AL / W is preferably 0.095 or less, more preferably 0.090 or less, and even more preferably 0.085 or less.

[0027] The molar ratio Si / W of silicon ions (Si) to water (W) constituting the alkalinity source is 0.035 to 0.085. If Si / W is less than 0.035, the compressive strength of the hardened geopolymer decreases, and if Si / W is more than 0.085, the viscosity of the geopolymer composition is high, making it difficult to use in field work and hindering construction. From the above viewpoints, it is preferable that Si / W is 0.050 to 0.070.

[0028] (Water) The water is not particularly limited and tap water, ion-exchanged water, pure water, etc. can be used.

[0029] In addition to the above, various admixtures and additives can be added to the geopolymer composition of the present invention as long as they do not impair the effects of the present invention. For example, known materials used in concrete, such as fluidizers, shrinkage reducing agents, rust inhibitors, waterproofing agents, setting retarders, antifoaming agents, dust reducing agents, pigments, and calcium carbonate powder, can be added.

[0030] In addition to the above, various aggregates can be added to the geopolymer composition of the present invention depending on the application. For example, known aggregates used in concrete such as lightweight aggregate, ordinary aggregate, heavy aggregate, limestone aggregate, slag aggregate, and silica sand can be added.

[0031] (Method for producing geopolymer composition) The geopolymer composition of the present invention can be produced by simultaneously or sequentially mixing predetermined amounts of powder components, alkali source, water, and, if necessary, various admixtures and aggregates, and then kneading them appropriately using a kneading device. The kneading device is not particularly limited, and examples include a forced twin-shaft mixer used for mixing concrete.

[0032] The method for producing a geopolymer composition includes, for example, a powder mixing step in which a powder component, a powdered alkali source, and an aggregate are powder-mixed, and a kneading step in which water is added after the powder mixing step. Note that a secondary kneading step in which admixtures such as a fluidizer and a setting retarder are mixed and kneaded after the kneading step may be provided.

[0033] (Method for manufacturing hardened geopolymer composition) After the kneading step or the secondary kneading step of the geopolymer composition, the geopolymer composition can be cured at a temperature range of 5°C to 90°C to obtain a hardened geopolymer composition. In particular, when an alkali metal silicate and an alkali carbonate are used in combination as the alkali source of the geopolymer composition, a hardened geopolymer composition with excellent compressive strength can be obtained by curing at room temperature of 5 to 35°C. Other curing conditions are not particularly limited, and commonly used curing conditions may be used. For example, steam curing, sealed curing, air curing, underwater curing, etc. may be used.

[0034] <Other embodiments> The geopolymer composition of the present invention is not limited to the above-described embodiments, and various modifications may be made within the scope of the present invention. Furthermore, part of the configuration of an embodiment can be deleted. Also, well-known technology can be added to the configuration of an embodiment.

[0035] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited to the following examples. Various modifications and applications are also included in the present invention as long as the features of the present invention are not significantly impaired.

[0036] (Raw materials) Powder components (1) Fly ash (FA): Type II fly ash (compliant with JIS A 6201) (2) Ground slag (BS): Ground blast furnace slag 4000 (compliant with JIS A 6206) Alkali source (alkali silicate, alkali carbonate) (3) Powdered sodium silicate (Ns): Sodium silicate powder (SiO ２ / Na ２ O molar ratio = 1.98, H ２(O = approximately 20% by mass, manufactured by our company) (4) Soda ash (Nc): Sodium carbonate powder (manufactured by our company) Other raw materials (5) Fine aggregate (s): Fine aggregate (JIS standard sand) (6) Added water: Ion-exchanged water

[0037] [Preparation of Geopolymer Composition (Mortar)] The formulation of the geopolymer composition (mortar) is shown in Table 1. After preparing the powdered geopolymer composition, the geopolymer composition was obtained as mortar.

[0038] [Preparation of powdered geopolymer composition] Fly ash, slag powder, soda ash, and powdered sodium silicate were weighed according to the recipe in Table 1, placed in a polyethylene bag, and stirred for 3 minutes to prepare a uniformly dispersed powdered geopolymer composition. The content (Vol%) of blast furnace slag powder relative to the total powder components, which contribute to the compressive strength and 15-stroke mortar flow value (fluidity), and (A + W) / F were all set to the same value.

[0039] [Mixing of mortar using powdered geopolymer composition] The powdered geopolymer composition and water were added to a Hobart mixer and stirred for 1 minute, then fine aggregate was added and mixed for 30 seconds, scraped off for 15 seconds, and then mixed for another 2 minutes to obtain a uniformly mixed geopolymer composition as mortar. The 15-stroke mortar flow value and compressive strength of the resulting mortar were measured, and the results are shown in Table 2.

[0040]

[0041] *AL / W: The molar ratio of sodium (Na) atoms contained in soda ash and powdered sodium silica to the water molecules (W) in the added water and powdered sodium silica. *Si / W: The molar ratio of silicon (Si) atoms contained in powdered sodium silica to the water molecules (W) in the added water and powdered sodium silica. *(A+W) / F: The ratio of the volume (A+W) of the solution made by mixing the alkaline component (A) consisting of soda ash and powdered sodium silica with added water to the volume (F) of the powder component consisting of fly ash and pulverized slag.

[0042] (Comparative Examples 1 to 3) Comparative Examples 1 to 3 are geopolymer compositions whose formulations are adjusted so that the Si / W (molar ratio) is greater than 0.085 and the AL / W (molar ratio) is 0.100 or more.

[0043] (Examples 1 to 5) Examples 1 to 5 are geopolymer compositions whose formulations were adjusted so that the Si / W (molar ratio) was 0.035 to 0.085 and the AL / W (molar ratio) was less than 0.100.

[0044] (Comparative Example 4) Comparative Example 4 is a geopolymer composition in which the formulation is adjusted so that the Si / W (molar ratio) is less than 0.035 and the AL / W (molar ratio) is less than 0.100.

[0045] [15-hit mortar flow test] In accordance with the mortar flow test prescribed in JIS A 5201, the mortar flow values ​​of Comparative Examples 1 to 4 and Examples 1 to 5 were measured after 15 dropping motions immediately after mixing. The results are shown in Table 2. The relationship between AL / W and Si / W and the 15-hit mortar flow is shown in Figures 1 and 2.

[0046] [Compression Strength Test] The mortars of Comparative Examples 1 to 4 and Examples 1 to 5 were sealed in containers of φ (diameter) 50 mm × 100 mm, and sealed and cured at 20°C until the specified material ages (1 day, 3 days, 7 days, and 28 days) were reached.

[0047] The mortars cured to the specified ages (1 day, 3 days, 7 days, and 28 days) were subjected to a compressive strength test in accordance with the compressive strength test method specified in JIS A 1108 to measure their compressive strength. The results are shown in Table 2. The relationship between Si / W and compressive strength at 1 day is shown in Figure 3.

[0048]

[0049] As shown in Figures 1 and 2, the 15-stroke flow decreased with increasing Si / W, and the degree of decrease was significant above 0.085. Furthermore, the 15-stroke flow decreased linearly with increasing AL / W. Therefore, in order to obtain a geopolymer composition with good fresh properties and a 15-stroke flow of 160 mm or more, it was effective to keep AL / W below 0.100 and Si / W below 0.085.

[0050] As shown in Figure 3, the compressive strength at the early age of the material increases with increasing Si / W, and the degree of increase tends to increase sharply at 0.035 or more. Therefore, in order to obtain a geopolymer composition with good early strength development, it is effective to set Si / W to 0.035 or more.

Claims

1. A geopolymer composition comprising a powder component, water, and an alkali source, wherein the powder component comprises at least one of ground blast furnace slag or fly ash, the alkali source comprises at least an alkali metal silicate, and the molar ratio of alkali metal ions contained in the alkali source to the water: AL / W is less than 0.100, and the molar ratio of silicon ions contained in the alkali source to the water: Si / W is 0.035 to 0.

085.

2. The geopolymer composition of claim 1, wherein the alkali source comprises an alkali metal silicate and an alkali metal carbonate.

3. The geopolymer composition of claim 1, wherein the alkali metal silicate is sodium silicate.

4. The geopolymer composition of claim 2, wherein the alkali metal carbonate is sodium carbonate.

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