Biomass incineration ash-containing composition and hardened body thereof

Abstract

To provide a cement substitute composition that does not use cement, in which the composition can be handled safely, a usable time is equivalent to that of conventional cement compositions, and the properties of the composition before hardening can be easily adjusted, and to provide a hardened body thereof.SOLUTION: A biomass incineration ash-containing composition for producing a hardened body comprises: a biomass incineration ash; and an aqueous solution of salt having a salt concentration of 2.0 mass% or more. According to the present invention, a calcium silicate hydrate (C-S-H) is formed when both are mixed, and a hardened body can be obtained without the use of cement. The present invention also provides the hardened body of the biomass incineration ash-containing composition of the present invention.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a biomass incineration ash-containing composition for producing a hardened body and a hardened body thereof, and in particular to a biomass incineration ash-containing composition for producing a hardened body and a hardened body thereof, which is a cement-free cement-substitute composition. [Background technology]

[0002] The Japanese government has declared that it will aim to achieve carbon neutrality, or zero overall greenhouse gas emissions, by 2050, and the trend toward decarbonization is accelerating in all sectors.

[0003] In the construction sector, there is a need for cement-free hardened concrete alternatives, as the cement used in concrete emits large amounts of CO2 during the manufacturing process.

[0004] Non-Patent Document 1 proposes geopolymer as a cement-free concrete substitute. Figure 2(A) is a bar graph showing an example of the mixing ratio of raw materials for a conventional geopolymer, and Figure 2(B) is a bar graph showing an example of the mixing ratio of raw materials for a conventional cement composition.

[0005] Non-Patent Document 1 defines geopolymer 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 an aqueous solution of alkali metal silicate, carbonate, or hydroxide. Examples of active fillers include fly ash (coal ash) and ground granulated blast furnace slag, and examples of alkali metal silicate solutions include water glass or a mixture of water glass with a sodium hydroxide solution or a potassium hydroxide solution. Note that geopolymers may optionally contain aggregate.

[0006] Conventional cement compositions contain cement C, water W, and aggregates (fine aggregate S and aggregate G) as shown in the same figure (B), but the geopolymer in Non-Patent Document 1 is expected to produce a concrete substitute hardened body with reduced CO2 emissions during production compared to conventional methods, as shown in the same figure (A), since it does not use cement. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] "Committee Report: Research Committee on Application of Geopolymer Technology to the Construction Sector," Proceedings of the Japan Concrete Institute, Vol. 39, No. 1, 2017, published by the Japan Concrete Institute Summary of the Invention [Problem to be solved by the invention]

[0008] According to the geopolymer in Non-Patent Document 1, because it does not use cement, CO2 emissions during production are lower than those of conventional hardened cement bodies. However, as shown in Figure 2(A), it uses an alkaline irritant such as an alkali metal silicate solution, which makes it highly dangerous during production and requires careful handling of the raw materials.

[0009] In addition, as shown in Non-Patent Document 1, geopolymers have a shorter pot life than cement compositions, making them difficult to apply.

[0010] Furthermore, since an alkaline irritant is used, the effect of a chemical admixture cannot be obtained, and it is difficult to adjust the fluidity of the composition before hardening.

[0011] In view of the above problems, an object of the present invention is to provide a cement-free cement-substitute composition which can be handled safely, has a pot life equivalent to that of conventional cement compositions, and allows easy adjustment of the physical properties of the composition before hardening, and a hardened product thereof. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to achieve the above object, and as a result, have discovered that by adding seawater to biomass incineration ash and kneading the mixture, a hardened body having the desired compressive strength can be obtained without adding cement, which has led to the completion of the present invention.

[0013] That is, the invention described in claim 1 for achieving the above-mentioned object is a biomass incineration ash-containing composition for producing a hardened body, characterized in that it contains biomass incineration ash and an aqueous salt solution having a salt concentration of 2.0 mass% or more.

[0014] According to this invention, it is presumed that calcium silicate hydrate (CSH) is formed by mixing biomass incineration ash with an aqueous solution of salt with a salinity of 2.0% by mass or more, and a hardened body can be obtained without using cement. Since no alkaline irritant is used in the production of this hardened body, the raw materials can be handled safely, and since the effects of chemical admixtures are obtained, it is easy to adjust the fluidity of the composition before hardening. Furthermore, since the hardening mechanism is the same as that of cement, the pot life is also the same as that of conventional cement compositions.

[0015] It is also preferable that the biomass incineration ash is obtained from a biomass power plant, and the furnace of the biomass power plant is preferably of the circulating fluidized bed type.

[0016] Furthermore, the biomass incineration ash is preferably fly ash generated from a biomass incineration facility.

[0017] Moreover, it is preferable that the W / BFA ratio, which is the mass ratio of the aqueous salt solution to the biomass incineration ash, is 10% or more and 60% or less.

[0018] In addition, the biomass incineration ash-containing composition of the present invention preferably contains a chemical admixture for adjusting fluidity.

[0019] Furthermore, the above object can also be achieved by a biomass incineration ash-containing composition for producing a hardened body, which contains biomass incineration ash and fresh water or an aqueous salt solution having a salt concentration of 0% by mass or more and less than 2.0% by mass, and can also be achieved by a hardened body of the biomass incineration ash-containing composition of the present invention. Effect of the Invention

[0020] According to the biomass incineration ash-containing composition and its hardened product of the present invention, it is presumed that calcium silicate hydrate (CSH) is formed by mixing the biomass incineration ash with an aqueous solution of a salt having a salt concentration of 2.0 mass% or more, and it is considered that a hardened product can be obtained without using cement. Since no alkaline irritant is used in the production of this hardened product, the raw materials can be safely handled, and since the effect of a chemical admixture is obtained, it is easy to adjust the fluidity of the composition before hardening. Furthermore, since the hardening mechanism is the same as that of cement, the pot life is also the same as that of conventional cement compositions.

[0021] Therefore, it is possible to provide a cement-substitute composition that can be handled in the same way as conventional cement compositions, even though it does not use cement. In addition, since the biomass incineration ash-containing composition and its hardened body of the present invention do not use cement, the amount of CO2 emitted during production is reduced compared to conventional methods. [Brief description of the drawings]

[0022] [Figure 1] 1 is a bar graph showing the blending ratio of raw materials of the biomass incineration ash-containing composition of Example 2. [Diagram 2] 1A is a bar graph showing an example of a mixing ratio of raw materials for a conventional geopolymer, and (B) an example of a mixing ratio of raw materials for a conventional cement composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] <Biomass incineration ash-containing composition> The biomass incineration ash-containing composition of the present invention is for producing a hardened body thereof, and contains biomass incineration ash and an aqueous salt solution having a salt concentration of 2.0 mass % or more.

[0024] Biomass incineration ash is obtained by burning woody biomass, herbaceous biomass, and other plant-derived food waste.

[0025] Examples of woody biomass include unused thinned wood, sawmill residues, recycled wood chips, sawdust, and bark. Examples of herbaceous biomass include bamboo, rice husks, sugar cane, rice straw, and tea leaves. Examples of plant-derived food residues include fruit peels and coffee grounds.

[0026] The biomass incineration ash may be any ash generated after the above-mentioned biomass incineration, but from the standpoint of promoting the use of biomass incineration ash generated as a by-product of biomass power generation and from the standpoint of a stable supply of biomass incineration ash, it is preferable that the biomass incineration ash is obtained from a biomass power plant that burns biomass such as unused thinning materials, sawmill residues, and recycled wood.

[0027] For example, biomass incineration ash has a specific surface area of ​​1,500 g / cm according to JIS R 5201 8.1 (specific surface area test, Blaine method). 2 Above 2,500g / cm 2 More preferably, it is equal to or greater than this.

[0028] The specific surface area is 1,500g / cm 2 Since the above biomass incineration ash is obtained in a high proportion from the furnace of a circulating fluidized bed type biomass power plant, it is preferable that the furnace of the biomass power plant from which the biomass incineration ash is obtained is of the circulating fluidized bed type.

[0029] Similarly, from the viewpoint of obtaining biomass incineration ash having a large specific surface area, the biomass incineration ash is preferably fly ash generated from a biomass incineration facility.

[0030] Examples of the aqueous salt solution having a salt concentration of 2.0% by mass or more include seawater, artificial seawater, and diluted waters thereof.

[0031] In the present invention, the salt concentration is the total concentration of sodium salt, magnesium salt, calcium salt, and potassium salt, and the metal ions (Mg 2+ , Na + It is believed that these factors contribute to increasing the strength of the hardened body.

[0032] The salt concentration of the aqueous salt solution having a salt concentration of 2.0% by mass or more is preferably 3.0% by mass or more, from the viewpoint of improving the strength of the hardened body.

[0033] From the viewpoint of easy availability, the aqueous salt solution having a salt concentration of 2.0 mass % or more is preferably seawater.

[0034] Furthermore, the biomass incineration ash-containing composition of the present invention preferably contains a chemical admixture for adjusting fluidity. Examples of the chemical admixture for adjusting fluidity include an air entraining agent, a water reducing agent, an air entraining water reducing agent, and a high-performance air entraining water reducing agent.

[0035] In addition to the above-mentioned chemical admixtures for adjusting fluidity, the biomass incineration ash-containing composition of the present invention may contain various other admixtures, such as hardening accelerators, setting retarders, quick-setting agents, waterproofing agents, foaming agents, foaming agents, non-separating admixtures in water, water retention agents, drying shrinkage reducing agents, separation reducing agents (thickeners), and antifreeze / cold resistance agents, as necessary.

[0036] Furthermore, the biomass incineration ash-containing composition of the present invention may contain aggregates such as soil and sand. From the viewpoint of promoting the utilization of biomass incineration ash, it is preferable that the composition does not contain aggregates, and it is particularly preferable that the biomass incineration ash-containing composition is composed of biomass incineration ash and an aqueous solution of salt with a salt concentration of 2.0 mass% or more (however, it may contain an optional chemical admixture for adjusting fluidity and the above-mentioned other optional admixtures).

[0037] In addition, when an optional chemical admixture for adjusting fluidity and the above-mentioned other optional admixtures are contained in the biomass incineration ash-containing composition of the present invention, the total amount of the chemical admixture for adjusting fluidity and the above-mentioned other admixtures is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less per 100 parts by mass of biomass incineration ash.

[0038] On the other hand, since the present invention is premised on not using cement, which emits a large amount of CO2 during the manufacturing stage, the biomass incineration ash-containing composition of the present invention does not contain cement.

[0039] The biomass incineration ash-containing composition of the present invention has a W / BFA ratio, which is the mass ratio of the aqueous solution of the salt (W) to the biomass incineration ash (BFA), of preferably 10% or more and 60% or less, more preferably 15% or more and 50% or less, and particularly preferably 20% or more and 40% or less.

[0040] If the W / BFA ratio is less than 10%, the fresh properties of the biomass incineration ash-containing composition will be too hard, even if a chemical admixture for adjusting fluidity is included, making it difficult to form the desired hardened body.

[0041] Furthermore, when the W / BFA ratio exceeds 60%, the amount of calcium silicate hydrate (CSH) formed decreases due to a shortage of biomass incineration ash, resulting in a significant decrease in the compressive strength of the hardened body.

[0042] In addition, when the biomass incineration ash-containing composition of the present invention contains a chemical admixture or admixture for adjusting fluidity, the mass of the admixture or admixture is to be added to the mass of the salt aqueous solution having a salt concentration of 2.0 mass% or more in calculating the W / BFA ratio.

[0043] Next, the method for producing the biomass incineration ash-containing composition of the present invention will be described.

[0044] The biomass incineration ash-containing composition is basically prepared by a method similar to that used for preparing general mortar. Specifically, the biomass incineration ash is first added to a well-known hand mixer, pan mixer, or the like used for producing mortar. If a powder component is added in addition to the biomass incineration ash, it is added at this stage and powder mixing is performed.

[0045] After adding biomass incineration ash or mixing the powder, add an aqueous solution of salt with a salt concentration of 2.0% by mass or more and knead. After kneading, it is preferable to scrape off insufficiently mixed deposits from the corners of the mixer and around the stirring blades. After kneading again, the cement composition is obtained.

[0046] <Hardened body of composition containing biomass incineration ash> The hardened body of the biomass incineration ash-containing composition of the present invention is a hardened body obtained by hardening the biomass incineration ash-containing composition of the present invention. Specifically, the biomass incineration ash-containing composition prepared as above is poured into a suitably installed formwork and cured to obtain the hardened body. Note that reinforcing bars are not incorporated into the formwork, and therefore the obtained hardened body does not contain reinforcing bars.

[0047] The biomass incineration ash-containing composition poured into the formwork is subjected to compaction to remove air bubbles. Compaction is performed by vibration compaction using a vibrator.

[0048] After compaction, the mixture is cured until it attains the required compressive strength, and a hardened body of the biomass incineration ash-containing composition of the present invention is obtained.

[0049] The hardening mechanism of biomass incineration ash and an aqueous solution of salt such as seawater with a salt concentration of 2.0 mass% or more is similar to the hardening mechanism of cement and water. That is, it is considered that the biomass incineration ash contains CaO and SiO2, and when this comes into contact with water, calcium silicate hydrate (CSH) is formed, which causes the biomass incineration ash-containing composition to harden. Furthermore, in the present invention, as described above, Mg 2+ , Na +It is believed that metal ions such as these contribute to the acceleration of hardening.

[0050] On the other hand, fly ash (coal ash) has no or little CaO, so CSH does not form, and therefore the combination of coal ash and seawater does not produce a hardened body with sufficient compressive strength.

[0051] According to the biomass incineration ash-containing composition and its hardened body of the present invention, it is presumed that calcium silicate hydrate (CSH) is formed by mixing the biomass incineration ash with an aqueous salt solution having a salt concentration of 2.0 mass% or more, and it is considered that a hardened body can be obtained without using cement.

[0052] In the production of this hardened body, since no alkaline irritant is used, the raw materials can be handled safely, and since the effects of chemical admixtures are obtained, the fluidity of the composition before hardening can be easily adjusted. Furthermore, since the hardening mechanism is the same as that of cement, the pot life is also the same as that of conventional cement compositions.

[0053] Furthermore, geopolymers often use multiple materials, and there are no established methods for mix design. However, the hardening mechanism of the biomass incineration ash-containing composition of the present invention is similar to the hardening mechanism of cement and water, and basically, hardening is possible by combining biomass incineration ash with an aqueous salt solution with a salinity of 2.0 mass% or more, such as seawater, making mix design easy.

[0054] Therefore, it is possible to provide a cement-substitute composition that can be handled in the same way as conventional cement compositions, even though it does not use cement. In addition, since the biomass incineration ash-containing composition and its hardened body of the present invention do not use cement, the amount of CO2 emitted during production is reduced compared to conventional methods.

[0055] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the invention.

[0056] For example, the biomass incineration ash-containing composition for producing a hardened body of the present invention contains an aqueous salt solution having a salt concentration of 2.0 mass% or more. However, depending on the required compressive strength, the biomass incineration ash-containing composition for producing a hardened body of the present invention may contain an aqueous salt solution having a salt concentration of 0 mass% or more and less than 2.0 mass% or fresh water instead of the above-mentioned aqueous salt solution.

[0057] That is, in another embodiment, the biomass incineration ash-containing composition for producing a hardened body of the present invention contains biomass incineration ash and fresh water or an aqueous salt solution having a salt concentration of 0 mass % or more and less than 2.0 mass %.

[0058] Examples of salt solutions or freshwater with a salinity of 0% by mass or more and less than 2.0% by mass include lake water, river water, well water, and tap water. In addition, salt solutions produced by diluting seawater with these fresh waters are also included in the salt solutions or freshwater with a salinity of 0% by mass or more and less than 2.0% by mass.

[0059] From the viewpoint of promoting the utilization of biomass incineration ash, the biomass incineration ash-containing composition for producing the hardened body of the present invention in this embodiment preferably does not contain other components such as aggregates, and it is particularly preferable that the biomass incineration ash-containing composition consists of biomass incineration ash and an aqueous salt solution having a salt concentration of 0 mass% or more and less than 2.0 mass% (however, it may contain the above-mentioned optional chemical admixture for adjusting fluidity and the above-mentioned other optional admixtures).

[0060] In addition, when an optional chemical admixture for adjusting fluidity and the above-mentioned other optional admixtures are contained in the biomass incineration ash-containing composition of the present invention, the total amount of the chemical admixture for adjusting fluidity and the above-mentioned other admixtures is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less per 100 parts by mass of biomass incineration ash.

[0061] According to the biomass incineration ash-containing composition for producing a hardened body of the present invention, it is presumed that calcium silicate hydrate (CSH) is formed when CaO and SiO2 in the biomass incineration ash come into contact with water, and it is considered that a hardened body of the biomass incineration ash-containing composition can be obtained without using cement.

[0062] In addition, in the examples described below, the inventors have confirmed that a biomass incineration ash-containing composition consisting of biomass incineration ash and tap water can be prepared without separation, and that a hardened body having a predetermined compressive strength can be obtained from this biomass incineration ash-containing composition within 7 days of curing.

[0063] Furthermore, since the composition contains a salt solution or fresh water with a salinity of 0% by mass or more and less than 2.0% by mass, even in areas where a salt solution with a salinity of 2.0% by mass or more, such as seawater, cannot be obtained, such as when preparing a biomass incineration ash-containing composition for producing a hardened body of the present invention in inland areas, the composition can be prepared using fresh water such as nearby river water or tap water. EXAMPLES

[0064] The present invention will be specifically described below by showing examples, but the present invention is not limited to these examples.

[0065] 1. Preparation of biomass incineration ash-containing composition Biomass incineration ash (fly ash purchased from Buzen Biomass Power Plant (Oita Prefecture), density 2.47 g / cm) was placed in a Hobart-type mortar mixer with a nominal capacity of 10 L. 3 ) was added, and an air-entraining water-reducing agent (product number: Master Pozzolith® No. 70, manufacturer: Pozzolith Solutions Inc., density 1.00 g / cm 3) was further added and mixed with artificial seawater (※1) to obtain a biomass incineration ash-containing composition. In Example 2-2, tap water was added instead of the artificial seawater. The physical properties of the obtained biomass incineration ash-containing composition, as well as the mixing ratios of the biomass incineration ash, AE water-reducing agent, and artificial seawater are shown in Table 1 below.

[0066] *1: Part number 3-3419-01, artificial seawater MARINE ART SF-1, AS ONE Co., Ltd., diluted with distilled water to the specified concentration. Density 1.03g / cm 3 This corresponds to the aqueous salt solution of the present invention having a salt concentration of 2.0 mass % or more.

[0067] 2. Measurement of fresh properties In this embodiment, the Vf20 value is basically used for the fresh properties of the biomass incineration ash-containing composition. However, for the biomass incineration ash-containing composition having such a soft fresh property that it cannot be measured by the Vf20 value, the non-fall flow value is used.

[0068] (i) Measurement of Vf20 value The flow cone (JIS A 5201) was filled with the prepared biomass incineration ash-containing composition and placed on the table vibrator. The flow cone was then gently raised vertically. Only the biomass incineration ash-containing composition with a diameter of 100 mm was placed on the table vibrator. The table vibrator was vibrated for 20 seconds in this state, and the diameter of the biomass incineration ash-containing composition was then measured in 1 mm units to confirm the spread of the biomass incineration ash-containing composition in the diametric direction.

[0069] (ii) Measurement of unfallen flow value The flow value was measured in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement (Mortar Flow Test)". However, before measuring the flow value, the test specimen was not subjected to a drop motion after removing the flow cone.

[0070] [Table 1]

[0071] *2: When measuring the Vf20 value of Examples 2 and 2-2, molding was performed by vibration compaction using a table vibrator.

[0072] FIG. 1 is a bar graph showing the blending ratio of the raw materials of the biomass incineration ash-containing composition of Example 2.

[0073] As shown in Example 2 of Table 1, a biomass incineration ash-containing composition having a predetermined fresh property was obtained by adding artificial seawater (tap water for Example 2-2) to biomass incineration ash and kneading it. As shown in FIG. 1 and Table 1, the biomass incineration ash-containing composition of the present invention does not contain an alkaline irritant (such as an aqueous solution of an alkali metal silicate) unlike the geopolymer, so the fresh property of Example 2 was somewhat hard, but by adding an AE water-reducing agent as in Examples 3 and 4 and adjusting the amount of the agent added, it was possible to adjust the hardness of the biomass incineration ash-containing composition.

[0074] The adjustment of the hardness of the biomass incineration ash-containing composition in its fresh state by adding an AE water-reducing agent can also be understood from a comparison between Comparative Example 1 and Example 1.

[0075] 3. Production of hardened body of biomass incineration ash-containing composition The biomass incineration ash-containing composition obtained in 1. Preparation of biomass incineration ash-containing composition above was filled into a formwork (inner diameter 50 mm x height 100 mm), and the biomass incineration ash-containing compositions of Examples 2, 2-2, and 3 were compacted with a table vibrator (vibration frequency: 60 Hz), and the biomass incineration ash-containing compositions of Examples 4-5 and Comparative Example 2 were compacted by tapping 2-3 times with a tamper. The compacted biomass incineration ash-containing composition was cured in air (standard curing) until the material age of 7 days, and thereafter, was cured in water until the material age of 91 days, to obtain a hardened body of the biomass incineration ash-containing composition.

[0076] The compressive strength of each hardened specimen was measured at 7 days, 28 days, and 91 days in accordance with JIS A 1108:2018 "Test method for compressive strength of concrete." The results are shown in Table 2.

[0077] [Table 2]

[0078] *3: The hardened specimen used for the test compressive strength measurements is currently undergoing curing, and results after 28 and 91 days have not yet been obtained, so those data have not yet been acquired.

[0079] As shown in Examples 2 to 4 in Table 2, a hardened body could be obtained from a biomass incineration ash-containing composition containing biomass incineration ash and artificial seawater, and the hardened body showed high compressive strength even at an age of 28 days without the addition of cement. According to Example 2-2, a hardened body can be obtained from a biomass incineration ash-containing composition containing tap water and biomass incineration ash instead of artificial seawater. Although the hardened body is inferior to that of Example 2, which used artificial seawater, at the stage of 7 days of age, it is presumed that sufficient compressive strength can be obtained depending on the application.

[0080] In addition, a comparison between Comparative Example 1 and Example 1 revealed that even in cases where the W / BFA ratio is low and the fresh properties of the biomass incineration ash-containing composition are too hard to mold, the composition can be molded by adding an AE water reducer.

[0081] Furthermore, a comparison of Examples 2 to 4 shows that even when the fresh properties were adjusted by adding an AE water reducing agent, the effect on the compressive strength was small. [Industrial Applicability]

[0082] The biomass incineration ash-containing composition of the present invention is a cement-free cement substitute composition and is used to produce a hardened body. The hardened body obtained is used as a mounting material to be placed under embankments, seawalls, roads, etc.

Claims

1. A biomass incineration ash-containing composition for producing a hardened body, comprising biomass incineration ash and an aqueous salt solution having a salt concentration of 2.0 mass% or more.

2. The biomass incineration ash-containing composition according to claim 1, characterized in that the biomass incineration ash is obtained from a biomass power plant.

3. The biomass incineration ash-containing composition according to claim 2, characterized in that the furnace of the biomass power plant is of the circulating fluidized bed type.

4. The biomass incineration ash-containing composition according to claim 1, characterized in that the biomass incineration ash is fly ash generated from a biomass incineration facility.

5. The biomass incineration ash-containing composition according to claim 1, characterized in that the W / BFA ratio, which is the mass ratio of the aqueous salt solution to the biomass incineration ash, is 10% or more and 60% or less.

6. The biomass incineration ash-containing composition according to claim 1, further comprising a chemical admixture for adjusting fluidity.

7. A biomass incineration ash-containing composition for producing a hardened body, comprising biomass incineration ash and fresh water or an aqueous salt solution having a salinity of 0% by mass or more and less than 2.0% by mass.

8. A hardened body of the biomass incineration ash-containing composition according to any one of claims 1 to 7.

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