A curing aid solution, a self-hardening material, a method for producing a curing aid solution, and a method for producing a self-hardening material.

Abstract

To improve the performance of self-hardening materials. [Solution] A curing aid solution comprising an element Si, an alkali, and a dispersion medium, wherein the dispersion medium contains water, and the element Si is dissolved in an alkaline aqueous solution which is a mixture of the alkali and the dispersion medium, wherein the dissolved concentration of the element Si is 55,000 ppm by mass or more and 90,000 ppm by mass or less, and the concentration of the alkali in the alkaline aqueous solution is 3.5 mol / L or more and 4.0 mol / L or less.

Description

Technical Field

[0001] The present invention relates to a curing aid solution, a self-hardening material, a method for producing a curing aid solution, and a method for producing a self-hardening material.

Background Art

[0002] As self-hardening materials such as cement paste, mortar, and concrete, cement-based materials such as ordinary Portland cement are widely used. In addition, the development of self-hardening materials using coal ash (fly ash) as a base material instead of cement-based materials has been carried out. For example, Patent Document 1 discloses that a highly dense self-hardening material can be obtained by mixing fly ash whose surface is activated by mechanochemical treatment with a mixture (curing aid solution) of a strong alkali solution and silicon powder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, a highly dense self-hardening material can be obtained by mixing fly ash and a curing aid solution, but further improvement in performance is required for workability (such as fluidity and time until hardening), compressive strength, dimensional change rate, and the like.

[0005] The present invention has been made in view of such problems, and an object thereof is to optimize the conditions of the curing aid solution and improve the performance of the self-hardening material.

Means for Solving the Problems

[0006] The main invention for achieving the above objective is a curing aid solution comprising an element Si, an alkali, and a dispersion medium, wherein the dispersion medium contains water, and the element Si is dissolved in an alkaline aqueous solution which is a mixture of the alkali and the dispersion medium, wherein the dissolved concentration of the element Si is 55,000 ppm by mass or more and 90,000 ppm by mass or less, and the concentration of the alkali in the alkaline aqueous solution is 3.5 mol / L or more and 4.0 mol / L or less.

[0007] Other features of the present invention will be made clearer by description in this specification and the accompanying drawings. [Effects of the Invention]

[0008] According to the present invention, it is possible to improve the performance of self-hardening materials. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart of the method for manufacturing the self-hardening material in this embodiment. [Figure 2] This is a schematic diagram illustrating the hardening mechanism. [Figure 3] This is a diagram showing a list of test materials. [Figure 4] This is an explanatory diagram for the processing of coal ash. [Figure 5] This diagram shows a list of slurry conditions. [Figure 6] This figure shows the formulation conditions of the test specimens in the examples. [Figure 7] This figure shows the results of a simplified flow test. [Figure 8] This figure shows the measurement results of the change in viscosity over time when the silicon concentration is 40,000 ppm. [Figure 9] This figure shows the measurement results of the change in viscosity over time when the silicon concentration is 60,000 ppm. [Figure 10] This figure shows the results of the compressive strength test for each specimen. [Figure 11] This figure shows the dimensional change rate results for each test specimen.

Mode for Carrying Out the Invention

[0010] From the description of this specification and the accompanying drawings, at least the following matters become clear.

[0011] (Aspect 1) A curing aid solution containing Si element, an alkali, and a dispersion medium, wherein the dispersion medium contains water, and the Si element is dissolved in an aqueous alkali solution which is a mixture of the alkali and the dispersion medium, and the dissolution concentration of the Si element is 55000 mass ppm or more and 90000 mass ppm or less, and the concentration of the alkali in the aqueous alkali solution is 3.5 mol / L or more and 4.0 mol / L or less.

[0012] According to the curing aid solution of Aspect 1, the performance of the self-hardening material can be improved.

[0013] (Aspect 2) A self-hardening material comprising the curing aid solution according to claim 1 and ceramic powder containing Si element at least on the surface.

[0014] According to the self-hardening material of Aspect 2, based on the Si element from the curing aid solution and the Si element from the surface of the ceramic powder, a hardly soluble and long-term stable Si chain mineral can be formed.

[0015] (Aspect 3) The self-hardening material according to Aspect 2, wherein the ceramic powder preferably contains fly ash after unburned carbon removal treatment.

[0016] According to the self-hardening material of Aspect 3, by removing (reducing) unburned carbon, the workability (fluidity, etc.) can be improved.

[0017] (Aspect 4) The self-hardening material according to Aspect 3, wherein the content of unburned carbon in the fly ash after unburned carbon removal treatment is preferably 1% or less.

[0018] The self-hardening material of embodiment 4 can further improve workability.

[0019] (Appendix 5) A self-hardening material according to any of embodiments 2 to 4, wherein the hardening aid solution preferably contains silica fume that fills the spaces between the particles of the ceramic powder.

[0020] According to the self-hardening material of embodiment 5, it is possible to easily bond the surfaces of ceramic powders together.

[0021] (Aspect 6) A method for producing a curing aid solution, comprising the steps of: mixing an alkali with a dispersion medium containing water to produce an alkaline aqueous solution having an alkali concentration of 3.5 mol / L or more and 4.0 mol / L or less; and mixing an element of Si with the alkaline aqueous solution to produce a curing aid solution having a dissolution concentration of the element of Si of 55,000 ppm by mass or more and 90,000 ppm by mass or less.

[0022] According to the method for producing a curing aid solution of Embodiment 6, a curing aid solution that can improve the performance of self-hardening materials can be obtained.

[0023] (Aspect 7) A method for producing a self-hardening material, characterized by mixing the hardening aid solution produced in embodiment 6 with ceramic powder containing Si elements on at least its surface.

[0024] According to the method for manufacturing a self-hardening material of Embodiment 7, the performance of the self-hardening material can be improved.

[0025] ===Implementation Method=== Embodiments of the present invention will be described below. In this specification, "X~Y" indicating a range means "X or more and Y or less". Also, in this specification, ppm, which is the unit of concentration, means mass ppm.

[0026] The present inventors have proposed that a cementless, self-hardening material can be manufactured using coal ash (fly ash) as a base material (see Patent Document 1). Specifically, by subjecting coal ash to mechanochemical treatment to activate the surface of the coal ash, and then applying a mixture (slurry) of a strong alkaline solution and silicon powder, the activated surface is dissolved and the surfaces are bonded together to produce a self-hardening material. This technology makes it possible to utilize industrial by-products (for example, coal ash generated when coal is burned in a thermal power plant) in the manufacture of self-hardening materials.

[0027] Furthermore, the inventors have confirmed that workability, such as fluidity, can be improved by removing unburned carbon contained in coal ash (for example, to 1% or less). In this embodiment, the conditions of the slurry (for mixing) mixed with coal ash have been improved.

[0028] First, we will explain the manufacturing method for self-hardening materials. Figure 1 is a flow chart of the manufacturing method for the self-hardening material in this embodiment. Figure 2 is a schematic diagram showing the hardening mechanism.

[0029] In the material preparation process (Figure 1: S1), preparation (processing, etc.) is carried out for both coal ash (fly ash) and slurry.

[0030] <About fly ash> Coal ash (fly ash), an industrial by-product, typically contains several percent (for example, about 5%) of unburned carbon by weight. Coal ash is equivalent to ceramic powder containing at least silicon (Si) on its surface. Therefore, the unburned carbon is removed from the coal ash (fly ash) through an unburned carbon removal treatment (S11), as shown in Figure 2.

[0031] In this embodiment, a heating treatment using a heating device (electric furnace) is employed as an example of a method for removing unburned carbon from coal ash, but the method is not limited to this, and for example, a belt conveyor type coal decontamination device may be used. In this embodiment, "removal" of unburned carbon does not mean completely removing unburned carbon from coal ash, but rather reducing (decreasing) the content of unburned carbon in coal ash. As will be described later, even coal ash that has undergone unburned carbon treatment still contains a small amount of unburned carbon. By performing unburned carbon treatment to reduce the amount of unburned carbon contained in coal ash (for example, to 1% or less), the workability (fluidity) can be improved.

[0032] Next, a mechanochemical treatment (S12) is performed to activate the surface of the coal ash that has undergone unburned carbon removal treatment (unburned carbon-removed fly ash). Hereafter, the mechanochemical treatment will also be referred to as "MC treatment" or "grinding treatment". In Figure 2, the dashed line indicates that the fly ash has had its surface activated. In this way, the MC treatment imparts reactivity to the surface of the unreactive particles (in this case, coal ash), allowing the coal ash to function as a binder.

[0033] MC treatment is a process that imparts chemical properties (reactivity) to a solid material by applying mechanical treatments such as impact, shear, and friction. It can also be used to homogenize the components by crushing the particles. Examples of equipment capable of performing such treatments include mixing devices such as ball mills, vibratory mills, planetary ball mills, and media stirring mills, as well as crushers such as ball media mills, roller mills, and mortars, and jet crushers. In the embodiments described later, a planetary ball mill is used. Alternatively, equipment such as "Attrita" or "Alchemi" manufactured by Nippon Coke Industries Co., Ltd. may be used.

[0034] <About Slurry> Furthermore, in the material preparation process (S1), an alkali and a dispersion medium are mixed to produce a strong alkaline aqueous solution (hereinafter also referred to as a strong alkaline solution) (S13).

[0035] The dispersion medium is used to disperse or dissolve each component and includes water. Water contributes to the dissolution of compounds containing Si by dissolving alkalis and thus creating alkalinity. It is preferable to use water that contains as few impurities as possible. Specifically, it is preferable to use, for example, deionized water (ion-exchanged water), pure water, ultrapure water, or distilled water.

[0036] Furthermore, alkalis have the function of increasing the pH of a solution when added, and dissolve substances containing the element Si (silicon powder). Preferably, the alkali is an alkali metal hydroxide, and in this embodiment, potassium hydroxide (KOH), which is a hydroxide of potassium (an alkali metal), is used as the alkali. In this embodiment, the molar concentration of the alkali refers to the number of moles of alkali present in 1 L of solution (mol / L).

[0037] Next, a mixing treatment is performed in which a strong alkaline solution and silicon fine powder are mixed together to form a slurry (S14). In this embodiment, silica fume, mainly composed of amorphous silica, is used as the silicon fine powder.

[0038] This process generates a silicon mixture (slurry) in which silicon components are dissolved in a strong alkaline solution. The slurry is used to bind the coal ash (fly ash) particles together and is equivalent to a hardening aid solution.

[0039] In the examples described later, we focused on the potassium concentration and silicon dissolution concentration (hereinafter also simply referred to as silicon concentration) in the slurry (curing aid solution), and prototype slurries with varying potassium and silicon concentrations were prepared and used to evaluate their effect on the cured paste. Conventionally, the potassium concentration in the slurry was 3.0 mol / L and the silicon concentration was 40,000 ppm, but the results of the examples confirmed that it is desirable to increase the potassium and silicon concentrations above the conventional conditions. Specifically, a silicon concentration of 55,000 ppm to 90,000 ppm and a potassium concentration of 3.5 mol / L to 4.0 mol / L are desirable (details will be described later).

[0040] Next, in the mixing process of each material (Figure 1: S2), the surface-activated, unburned carbon-removed coal ash (fly ash) is mixed with a silicon mixture (slurry). As a result, as shown in Figure 2, Si from the fly ash surface and Si from silica fume are bonded together in a chain-like manner, producing a sparingly soluble, long-term stable Si chain mineral. The Si from silica fume also plays a role in filling the gaps in the fly ash.

[0041] Then, in the filling and curing process (Figure 1: S3), the mixture of fly ash and slurry is filled (cast) into a formwork and cured for a predetermined period. This makes it possible to manufacture a self-hardening material that does not use cement (cementless).

[0042] <<Examples>> <Test materials> Figure 3 shows a list of test materials.

[0043] For the coal ash (fly ash), we used dust collection ash (abbreviated as Isogo 7) from the Isogo Thermal Power Plant.

[0044] Furthermore, the slurry used was potassium hydroxide (KOH) from Wako Reagents and silica fume powder (ELCHEM 940U: manufactured by ELCHEM Japan Co., Ltd.), which is a silica powder mainly composed of amorphous silica (mixing conditions are described later).

[0045] Figure 4 is an explanatory diagram of the coal ash treatment (unburned carbon removal treatment, MC treatment, etc.). As shown in Figure 4, the unburned carbon removal treatment involved heating in an electric furnace at 600°C for 1 hour. This reduced the unburned carbon content to less than 1% (approximately 0.1% in this case). Furthermore, grinding treatment (MC treatment) was performed for 3 hours using a Fritsch planetary ball mill to activate the surface (bring it to a mechanochemical state).

[0046] Figure 5 shows a list of slurry conditions. The slurry was prepared by heating and dissolving silica fume (SF) in a KOH solution using a hot stirrer.

[0047] The potassium hydroxide (KOH) slurry was prepared at three concentrations per liter of solution: 3.0 mol (3.0 mol / L), 3.5 mol (3.5 mol / L), and 4.0 mol (4.0 mol / L).

[0048] Furthermore, the silicon (Si) concentration in the slurry was set to two types: 40,000 ppm and 60,000 ppm. For example, as shown in Figure 5, in the case of 40,000 ppm, 4.7 g of silica fume (SF) was dissolved in 50 g of alkali (KOH) solution. In the case of 60,000 ppm, 6.2 g of silica fume (SF) was dissolved in 50 g of alkali (KOH) solution. Note that the mixing conditions of alkali (KOH) solution and silica fume (SF) in the preparation of the test specimens (Figure 6), described later, differ from the mixing amounts in Figure 5, but the ratio of alkali (KOH) solution to silica fume (SF) is the same.

[0049] <Method for preparing test specimens> Figure 6 shows the formulation conditions of the test specimens in the examples. The test specimens were paste-cured bodies. In Figure 6, the abbreviation of the test specimen (slurry type) is indicated by the potassium concentration - silicon (Si) concentration of the slurry. For example, test specimen No. 1 (conventional conditions) has a slurry potassium concentration of 3.0 mol / L and a silicon concentration of 40,000 ppm.

[0050] As shown in Figure 6, in the specimens with a silicon concentration of 40,000 ppm (No. 1-3), 8.52 g of silica fume (SF) was added to 90.52 g of KOH solution. In the specimens with a silicon concentration of 60,000 ppm (No. 4-6), 11.32 g of silica fume (SF) was added to 91.43 g of KOH solution.

[0051] Furthermore, as shown in Figure 6, the amount of slurry is the sum of the amount of silica fume (SF) and the amount of mixing water (W: KOH solution). For example, in the case of specimen No. 1, the amount of silica fume (SF) is 8.52 (g) and the amount of mixing water (W: here, a 3 mol / L KOH solution) is 90.52 (g), so the amount of slurry (g) is 99.04 (= 8.52 + 90.52). Also, for example, in the case of specimen No. 6, the amount of silica fume (SF) is 11.32 (g) and the amount of mixing water (W: here, a 4 mol / L KOH solution) is 91.43 (g), so the amount of slurry (g) is 102.75 (= 11.32 + 91.43).

[0052] Furthermore, as shown in Figure 6, the binder (B) contains coal ash (fly ash) and silica fume (SF). In other words, the amount of binder (B) is the sum of the amount of coal ash and the amount of silica fume (SF). For example, in the case of specimen No. 1, there are 270g of coal ash and 8.52g of silica fume (SF), so the amount of binder (B) in grams is 278.52 (=270 + 8.52).

[0053] The ratio of mixing water (W) to binder (B) (W / B) is preferably between 25% and 60%, of which 32.5% was chosen because it consistently yields high compressive strength.

[0054] The method for manufacturing the test specimen involved preparing fly ash and slurry separately according to the procedure in step S1 of Figure 1, mixing the fly ash and slurry in step S2, pouring the mixture into a cylindrical mold in step S3, subjecting it to sealing and curing in a 40°C constant temperature oven for 2 days, and then drying and curing it at 40°C for 5 days after demolding.

[0055] <Exam Content and Method> The following tests were performed on each specimen in Figure 6.

[0056] (Simple flow test of paste) The paste, immediately after mixing, was poured into an acrylic container (28 mm inner diameter, 23 mm height) placed on a stainless steel plate. The container was then gently lifted, and the spread of the paste was measured as a flow value. For each specimen, the flow value was measured at two points: in the direction of maximum spread and in a direction perpendicular to it, and the average of these two points was used.

[0057] (Changes in paste viscosity over time) The time-dependent change in the viscosity of the paste was measured using a rheometer (viscometer). A Malvern Panalytical KINEXUS Lab+ rotary rheometer was used. The paste was placed between 3cm diameter stainless steel discs, with a gap (paste thickness) of 1mm. A 0.2% shear strain was applied at a frequency of 5Hz, and the paste's response was measured. The sampling interval was 10 seconds.

[0058] (Compressive strength testing and dimensional change rate measurement of the test specimen) • Compressive strength: Measured using specimens 7 days old (2 days sealed and cured, 5 days dried). Three specimens were used per strength level. A Shimadzu Autograph was used for the compressive strength test. • Dimensional change rate: The dimensions of the specimen were measured at two orthogonal points: immediately after demolding following sealing and curing at 2 days of age, and after drying and curing at 7 days of age. The average of these measurements was calculated as the diameter at each age. The dimensional change rate was calculated using the diameter at 2 days of age as the denominator and the difference between the diameter at 2 days and 7 days of age (diameter at 7 days - diameter at 2 days of age) as the numerator. In other words, a negative dimensional change rate indicates that the specimen shrank during hardening, while a positive dimensional change rate indicates that the specimen expanded during hardening.

[0059] <Test Results> (Simple flow test of paste) Figure 7 shows the results of a simplified flow test. The horizontal axis of the figure indicates the type of slurry (indicated by abbreviation), and the vertical axis indicates the flow value. The dotted line in the figure indicates the diameter of the container used for flow measurement (28 mm), and flow was defined as the increase (spread) from this value.

[0060] In a slurry with a silicon concentration of 40,000 ppm, increasing the potassium concentration from 3.0 mol / L to 3.5 mol / L doubled the flow rate. However, at a potassium concentration of 4.0 mol / L, the flow rate decreased slightly compared to when it was 3.5 mol / L.

[0061] In the case of a slurry with a silicon concentration of 60,000 ppm, the flow value was higher than in the case with a silicon concentration of 40,000 ppm, and there was almost no change in the flow value even when the potassium concentration was changed. This suggests that the spread of the paste may have reached its upper limit due to the relationship between the wettability of the paste and the stainless steel plate (it cannot be concluded that the viscosity of the paste reached its upper limit).

[0062] (Changes in paste viscosity over time)

[0063] Figure 8 shows the measurement results of the change in viscosity over time when the silicon concentration is 40,000 ppm, and Figure 9 shows the measurement results of the change in viscosity over time when the silicon concentration is 60,000 ppm. In Figures 8 and 9, the horizontal axis shows the elapsed time (minutes) from immediately after mixing, and the vertical axis shows the viscosity η (Pa·s).

[0064] At a silicon concentration of 40,000 ppm (Figure 8), increasing the potassium concentration from 3.0 mol / L to 3.5 mol / L resulted in a decrease in viscosity at all measurement times. Furthermore, increasing the potassium concentration from 3.5 mol / L to 4.0 mol / L resulted in similar viscosity from 0 minutes (immediately after mixing) to around 13 minutes, after which a slight decrease in viscosity occurred.

[0065] At a silicon concentration of 60,000 ppm (Figure 9), increasing the potassium concentration from 3.0 mol / L to 3.5 mol / L resulted in a decrease in viscosity at all measurement times. Furthermore, increasing the potassium concentration from 3.5 mol / L to 4.0 mol / L resulted in nearly the same viscosity.

[0066] Furthermore, at a silicon concentration of 60,000 ppm, a tendency for viscosity to decrease was observed at all potassium concentrations in the range of 0 to 30 minutes compared to the case of 40,000 ppm. However, after 40 minutes, the viscosity became lower at a potassium concentration of 4.0 mol / L and a silicon concentration of 60,000 ppm.

[0067] These results indicate that increasing the silicon concentration to 60,000 ppm is effective in increasing the flow rate. Furthermore, a potassium concentration of 3.5 mol / L or higher is considered optimal.

[0068] (Compressive strength testing and dimensional change rate measurement of the test specimen) Figure 10 shows the results of the compressive strength test for each specimen. The horizontal axis of the figure shows the abbreviation for the specimen (in this case, the abbreviation for slurry), and the vertical axis shows the compressive strength (N / mm²). 2 This indicates that...

[0069] When comparing samples with the same silicon concentration (40,000 ppm or 60,000 ppm), compressive strength increases almost linearly with increasing potassium concentration.

[0070] Furthermore, when the potassium concentration remains the same at 3.0 mol / L, increasing the silicon concentration from 40,000 ppm to 60,000 ppm results in a compressive strength of 5.6 N / mm². 2 The compressive strength increased. It was confirmed that when the alkali concentration was 3.5 mol / L and 4.0 mol / L, increasing the silicon concentration from 40,000 ppm to 60,000 ppm resulted in a greater increase in compressive strength.

[0071] These results confirm that increasing the silicon concentration in the slurry has a significant effect on increasing compressive strength, and that further increasing the alkali concentration (potassium concentration in this case) is also effective.

[0072] Figure 11 shows the results of the dimensional change rate for each specimen. The horizontal axis of the figure shows the abbreviation for the specimen (in this case, the abbreviation for slurry), and the vertical axis shows the dimensional change rate (%). As mentioned above, a negative dimensional change rate indicates that the specimen shrank during hardening. Conversely, a positive dimensional change rate indicates that the specimen expanded during hardening.

[0073] When comparing the results at the same silicon concentration (40,000 ppm or 60,000 ppm), a tendency for contraction to lessen with increasing potassium concentration was observed. In particular, when the potassium concentration was 3.0 mol / L and the silicon concentration was 60,000 ppm, a contraction of approximately -0.7% occurred, but when the potassium concentration was increased to 4.0 mol / L, the result shifted to expansion of 0.003%.

[0074] Therefore, it is estimated that increasing the potassium concentration of the alkaline aqueous solution from 3.0 mol / L (conventional conditions) is effective in suppressing the shrinkage of the test specimen.

[0075] Based on the results of the examples, the following conditions for the slurry were confirmed.

[0076] By increasing the silicon concentration beyond the conventional 40,000 ppm, the paste flow can be increased, improving its fluidity.

[0077] Furthermore, compressive strength can be increased by increasing the silicon concentration from the conventional 40,000 ppm and the alkali concentration (potassium concentration) from the conventional 3.0 mol / L. Note that another evaluation (not shown) has confirmed that hardened materials can be produced with a silicon concentration up to 90,000 ppm. Therefore, considering variability, a silicon concentration of 55,000 ppm to 90,000 ppm is preferable. Also, if the potassium concentration exceeds 4.0 mol / L, the pH becomes too high, increasing the risk. Therefore, a potassium concentration of 3.5 mol / L to 4.0 mol / L is preferable.

[0078] ===Regarding other embodiments=== The above embodiments are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention can be modified and improved without departing from its spirit, and it goes without saying that the present invention includes equivalents thereof.

[0079] (About fly ash) In the embodiments described above, coal ash (fly ash) was used, but the invention is not limited to fly ash; any ceramic powder containing Si elements on its surface is acceptable. The ceramic powder containing Si elements on its surface is not particularly limited, and known materials can be used. For example, blast furnace slag may be used. Alternatively, ceramic powders described in paragraphs "0016" and "0017" of Japanese Patent Application Publication No. 2008-239433 may be used.

[0080] Furthermore, while the above embodiment exemplified a mechanochemical treatment using a planetary ball mill, the treatment is not limited to this method as long as it can activate the surface of the coal ash.

[0081] Furthermore, although the previously described embodiment included a treatment to remove unburned carbon, this treatment is not required. However, if unburned carbon is present, performing the treatment to remove it can reduce the amount of unburned carbon, thereby improving workability (such as fluidity).

[0082] (About slurry) In the embodiments described above, silica fume was used as the silicon fine powder, but the invention is not limited to this, and any substance that can supply dissolved silicon element (Si element) in the presence of an alkali is acceptable. For example, silicon oxide (silica) powder, silicon nitride powder, silicon carbide powder, silicon oxidizide powder, silicon carbide nitride powder, polysilicon powder, etc. may also be used. Alternatively, silicic acids such as orthosilicic acid, pyrosilicic acid, metasilicic acid, and metadisiliic acid, or silicates such as potassium silicate (K2SiO3) and sodium silicate (Na2SiO3) may also be used.

[0083] Furthermore, although potassium hydroxide solution was used as the strong alkaline solution (alkaline aqueous solution) in the above-described embodiment, it is not limited to this, and any alkaline solution that is alkaline enough to elute silicon ions from silicon fine powder will suffice. For example, an aqueous solution of sodium hydroxide (sodium hydroxide solution) may be used.

[0084] (Regarding self-hardening materials) In the embodiments described above, a paste was evaluated, but self-hardening materials are not limited to pastes. For example, fine aggregate may be added to make mortar, or fine aggregate and coarse aggregate may be added to make concrete (cementless concrete).

[0085] Furthermore, in the step of mixing coal ash (fly ash) and silicon mixture (slurry) (step S2), other materials (for example, water-reducing agents and retarders to adjust the time until hardening, and shrinkage-reducing agents to prevent cracking) may be added.

Claims

1. It contains the element Si, an alkali, and a dispersion medium. The aforementioned dispersion medium contains water. A curing aid solution obtained by dissolving the Si element in an alkaline aqueous solution which is a mixture of the alkali and the dispersion medium, A curing aid solution characterized in that the dissolution concentration of the Si element is 55,000 ppm by mass or more and 90,000 ppm by mass or less, and the concentration of the alkali in the alkaline aqueous solution is 3.5 mol / L or more and 4.0 mol / L or less.

2. A self-hardening material characterized by comprising the curing aid solution described in claim 1 and ceramic powder containing Si element at least on its surface.

3. The self-hardening material according to claim 2, The ceramic powder includes fly ash that has been treated to remove unburned carbon, which is produced by treating fly ash to remove unburned carbon. A self-hardening material characterized by the following:

4. The self-hardening material according to claim 3, The unburned carbon content in the fly ash treated to remove unburned carbon is 1% or less. A self-hardening material characterized by the following:

5. The self-hardening material according to claim 2, The curing aid solution contains silica fume that fills the spaces between the particles of the ceramic powder. A self-hardening material characterized by the following:

6. The process involves mixing an alkali with a dispersion medium containing water to produce an alkaline aqueous solution with an alkali concentration of 3.5 mol / L or more and 4.0 mol / L or less, A step of mixing the Si element with the alkaline aqueous solution to produce a curing aid solution in which the dissolution concentration of the Si element is 55,000 ppm by mass or more and 90,000 ppm by mass or less, A method for producing a curing aid solution, characterized by having the following characteristics.

7. A method for producing a self-hardening material, characterized by mixing the hardening aid solution produced in claim 6 with ceramic powder containing Si elements on at least its surface to produce a self-hardening material.

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