Method for producing admixture, method for producing binder-comprising composition, method for producing mortar composition, method for producing concrete, and method for producing precast concrete

Abstract

To provide a method for producing an admixture by which a larger amount of sewage sludge incineration ash can be added as a concrete admixture.SOLUTION: Activated sewage sludge incineration ash slurry is prepared by mixing sewage sludge incineration ash with water, sand and a saturated calcium hydroxide solution and subjecting the mixture to ball mill mixing using a rotary pedestal. An admixture is prepared by drying the sewage sludge incineration ash slurry by heating. A rotation speed of the rotary pedestal is 30 rpm to 50 rpm. The amount of water is 25 to 200%, the amount of sand is 40 to 80%, and the amount of saturated calcium hydroxide solution is 20 to 80% with respect to the mass of sewage sludge incineration ash. The mixing time of the ball mill mixing is 1 to 5 hours. The heating and drying is performed at 90°C to 110°C for one day and night or longer.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention particularly relates to a method for producing admixtures, a method for producing binder-containing compositions, a method for producing mortar compositions, a method for producing concrete, and a method for producing precast concrete, using sewage sludge incineration ash used in concrete production.

Background Art

[0002] Sewage sludge is sludge generated in sedimentation ponds and reaction tanks at treatment plants during sewage treatment, and sewage sludge incineration ash (hereinafter abbreviated as "SA") is combustion ash obtained by incinerating sewage sludge to reduce its volume. The annual amount of industrial waste discharged in Japan is approximately 380 million tons, and sewage sludge accounts for approximately 20% of this. Although the recycling rate of sewage sludge decreased from 78% to 55% due to the impact of the Great East Japan Earthquake, it recovered to 73% in 2016. There are three major applications for recycled sewage sludge: (1) use in the cement field such as mortar compositions and concrete like construction materials such as bricks, cement, and alternative aggregates; (2) use in green agricultural land as composted fertilizer; and (3) use in the energy field as solid fuel and digested gas. However, only a part of it can be effectively utilized as a resource, and approximately 30% of sewage sludge is still landfilled. Therefore, it is an important technical issue to promote the expansion of application uses and the increase in usage volume by enhancing the value of SA as a resource.

[0003] Here, SA has three advantages as a material in the cement field. That is, (1) Ca(OH)2 generated by the hydration reaction of cement can react with the silica component in SA through a pozzolan reaction to generate calcium silicate hydrate and potentially enhance the compressive strength. (2) There is little variation in components throughout the year, and (3) stable supply is possible.

[0004] According to Patent Document 1, acid-resistant concrete is described which is produced by mixing water, industrial by-products, an alkali stimulant, an expansion agent, fine aggregate, coarse aggregate, and a high-performance water reducer, and which does not require coating or the like and has a long service life. It is also possible to use SA as industrial waste in the acid-resistant concrete of this Patent Document 1.

[0005] According to Non-Patent Document 1, a technique for highly activating SA is described in which SA particle water, sand, and a saturated calcium hydroxide solution are mixed and ball-milled and subdivided to about 5 μm. Different from fly ash which is pulverized coal combustion ash (hereinafter abbreviated as "FA"), although conventional SA contains a large amount of phosphorus component, it can be highly activated by converting the saturated calcium hydroxide solution into calcium phosphate and subdividing it. The highly activated SA produced by this ball milling becomes a slurry containing water (hereinafter referred to as "SA slurry").

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, the conventional SA slurry described in Non-Patent Document 1 contains a large amount of water. Therefore, when adding a large amount to concrete, the amount of water cannot be corrected beyond the unit water amount, and there is an upper limit to the amount that can be added. In other words, there is a quantitative limit to how much SA can be mixed into concrete, and technology that would allow it to be used in larger quantities was needed.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a method for manufacturing an admixture that solves the above-mentioned problems and enables activated SA to be added in larger amounts as a concrete admixture. [Means for solving the problem]

[0010] The method for producing an admixture of the present invention is a method for producing an admixture for concrete containing sewage sludge incineration ash, and is characterized in that the sewage sludge incineration ash is mixed with water, sand, and a saturated calcium hydroxide solution and mixed in a ball mill to produce an activated sewage sludge incineration ash slurry, and the sewage sludge incineration ash slurry is dried by heating. The admixture manufacturing method of the present invention is characterized in that, in the ball mill mixing, the rotation speed of the rotating stand is 30 rpm to 50 rpm, the amount of water is 25 to 200%, the amount of sand is 40 to 80%, and the amount of saturated calcium hydroxide solution is 20 to 80% relative to the mass of the sewage sludge incineration ash, the mixing time of the ball mill mixing is 0.3 to 2 hours, the average particle size of the sewage sludge incineration ash is 5 μm or less, layered crystals are attached to the surface of the particles by the ball mill mixing, and the drying by heating is performed at 90°C to 110°C for at least one day. The method for producing a binder-containing composition of the present invention is characterized by blending the admixture produced by the above-mentioned method for producing an admixture with a binder. The method for producing a binder-containing composition of the present invention is characterized in that the dried admixture is mixed so that the mass ratio of the binder is 10% to 35% and the admixture is an internal replacement of sand or binder. The method for manufacturing a mortar composition according to the present invention is characterized by manufacturing a mortar composition using the binder-containing composition manufactured by the method for manufacturing a binder-containing composition described above. The method for manufacturing concrete according to the present invention is a method for manufacturing concrete containing incinerated sewage sludge ash, wherein water, sand, and a saturated calcium hydroxide solution are mixed with the incinerated sewage sludge ash and ball mill mixing is performed to produce an activated incinerated sewage sludge ash slurry, and the incinerated sewage sludge ash slurry is dried by heating to obtain an admixture, and the dried admixture is blended so as to be 10% to 35% by weight ratio of cement and to replace a part of sand or binder. The method for manufacturing precast concrete according to the present invention is characterized by manufacturing precast concrete using the concrete manufactured by the method for manufacturing concrete described above. The method for manufacturing precast concrete according to the present invention is characterized by performing centrifugal molding during manufacturing.

Advantages of the Invention

[0011] According to the present invention, there is provided an admixture manufacturing method in which water, sand, and a saturated calcium hydroxide solution are mixed with incinerated sewage sludge ash and ball mill mixing is performed to produce an activated SA slurry, and this is dried by heating to produce an admixture that can be blended into concrete in a larger amount than conventional SA slurry.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0013] In order to promote the effective use of SA, the inventors of the present invention have developed an activation method by ball mill mixing. Specifically, by using SA, water, sand, a saturated calcium hydroxide solution, and balls with a high density such as stainless steel, and performing wet ball mill mixing using a rotating gantry, an SA slurry with improved compressive strength expression of SA was invented. However, the SA slurry contained a large amount of water. Therefore, when designing the concrete mix, it was necessary to reduce the water contained in the SA slurry from the unit water amount, and the maximum addition was limited to less than 20% by sand replacement.

[0014] Therefore, the inventors of the present invention repeatedly conducted experiments and produced a dried product of SA slurry by heating it to about 90°C to 110°C (hereinafter referred to as "SA dry powder") and added it to concrete. Then, the SA dry powder could be added in a larger amount, for example, up to about 30% at most, compared to the conventional SA slurry. Furthermore, it was noticed that when adding the SA dry powder to the concrete composition in this state, the compressive strength of the mortar increased more than when adding it in the state of SA slurry. The inventors of the present invention completed the SA dry powder as a concrete admixture according to the present invention by comparing these conditions and actually proceeding with the experiments. As a result, it became possible to incorporate the SA dry powder containing activated SA in the production of a larger amount of mortar compositions and concrete than before.

[0015] Hereinafter, embodiments of the admixture production method of the present invention, the binder-containing composition production method using SA, the mortar composition production method, the concrete production method, and the precast concrete production method will be described.

[0016] 〔Admixture Production Method〕 The admixture manufacturing method according to this embodiment is a method for manufacturing an admixture for concrete containing SA. In this method, water, sand, and a saturated calcium hydroxide solution are mixed with SA and ball mill mixing is performed to produce an activated SA slurry. The sewage sludge incineration ash slurry is dried by heating.

[0017] The SA according to this embodiment can use sewage sludge incineration ash obtained during sewage treatment, which may contain normal phosphorus. In this case, it is preferable to use SA with an average particle size of about 10 to 15 μm. Furthermore, as the SA of this embodiment, it is also possible to use "super ash" in which the particle size of SA is adjusted as described in Patent Document 1.

[0018] The water according to this embodiment is not particularly limited and may be tap water. The pH and the like of the water according to this embodiment are also arbitrary.

[0019] The sand according to this embodiment can use standard sand such as that used for fine aggregates of ordinary concrete. Specifically, for example, it corresponds to JIS A 5005 crushed sand (hard sandstone), and it is preferable to use those with a density of about 2.62 g / cm 3 More specifically, it is possible to use JIS standard sand for mortar, silica sand, etc.

[0020] The saturated calcium hydroxide solution according to this embodiment is preferably prepared by dissolving slaked lime corresponding to JIS R 9001 Special Grade, that is, calcium hydroxide (Ca(OH)2), in a saturated state in the above-mentioned water. The density of calcium hydroxide before dissolution is preferably about 2.30 g / cm 3 for example.

[0021] The ball mill mixing according to this embodiment is a mixing method in which materials and balls are placed in a container and rotated on a rotating base to make fine powder (atomization). In this embodiment, ball milling is performed using balls with a specific density or higher. Specifically, as balls with a specific density or higher, it is preferable to use ceramic balls such as zirconia (ZrO2) balls with a density of at least 6.00 g / ml, stainless steel balls with a density of about 7.9 g / ml, and the like. By using such balls with a specific density or higher, SA with high hardness can be activated, and an SA slurry can be produced.

[0022] Here, it is preferable that a plurality of balls with different diameters are used for the ball according to this embodiment. Specifically, as shown in the examples described later, in the case of a 500 ml wide-mouth reagent bottle, for example, in the case of zirconia balls, it is preferable to mix a plurality of balls with a diameter of 15 mm or more, specifically, 3 or more. More specifically, it is preferable to use a plurality of balls with different diameters because a more activating effect can be obtained. In the case of stainless steel balls, as shown in the examples described later, it is more preferable to mix 10 balls with a diameter of 15 mm and 5 balls with a diameter of 10 mm. Note that during the actual activation of SA, based on the configuration of such a 500 ml wide-mouth reagent bottle, it is possible to scale up to handle it.

[0023] As a more specific configuration of the ball milling mixture according to this embodiment, the rotation speed of the rotating base is 30 rpm to 50 rpm, water is 25 to 200%, sand is 40 to 80%, and the amount of saturated calcium hydroxide solution is 20 to 80% with respect to the mass of incinerated sewage sludge ash. The mixing time of the ball milling mixture is 0.3 to 2 hours, the average particle diameter of the incinerated sewage sludge ash is 5 μm or less, and by the ball milling mixture, a state where layered crystals adhere to the surface of the particles is obtained. Drying by heating is preferably carried out at 90°C to 110°C for one day and one night or more. Within such a range, SA is micronized with balls having a specific density or higher, and the SA slurry containing the activated SA is dried, whereby dry SA powder with a specific moisture content or less and a smooth texture can be produced.

[0024] Also, by ball mill mixing according to the present embodiment, it is preferable that the average particle diameter of SA particles is 5 μm or less. Specifically, by pulverizing SA under each of the above-described conditions and the scaled-up conditions, it is more preferable that the apparent average particle diameter of SA particles is about 5 μm or less.

[0025] Furthermore, by ball mill mixing according to the present embodiment, it is preferable that a state is obtained in which layered crystals are attached to the surface of the particles. That is, specifically, when pulverizing SA particles, it is possible to cause the phosphorus contained in SA to react with calcium hydroxide to generate calcium phosphate crystals that suppress the setting delay phenomenon of concrete.

[0026] Drying by heating according to the present embodiment is performed at 90°C to 110°C for one day and one night or longer, and it is preferable to dry so as to be below a specific moisture content. As this condition, for example, it may conform to the drying method described in a test method known to those skilled in the art such as JIS A 1102. Also, as the heat source, for example, relatively low-temperature ones such as waste heat from a sewage incineration plant and waste heat from other factories or boilers may be used.

[0027] In addition, in the method for activating SA, phosphorus contained in SA is immobilized by reacting with a saturated calcium hydroxide solution. At this time, it is also possible to absorb and immobilize not only phosphorus but also carbon dioxide extracted from the atmosphere and / or exhaust gas in the saturated calcium hydroxide solution.

[0028] This carbon dioxide can be, for example, the one absorbed or compressed by an absorption and compression facility from the atmosphere. Or, non-compressed carbon dioxide contained in the atmosphere at about 400 ppm may be used. Furthermore, it is also possible to use carbon dioxide contained in combustion exhaust gases such as petroleum, coal, and natural gas, and / or incineration exhaust gases of waste. Among these, for the combustion exhaust gas, it is also possible to use the exhaust gas of a rotary kiln furnace used in cement manufacturing. Furthermore, for the incineration exhaust gas of waste, it is also possible to use the exhaust gas during the incineration of sewage sludge. In this case, simultaneously with the acquisition of the above-mentioned sewage sludge incineration ash, the exhaust gas can be used for calcium carbonate production. Furthermore, by also using the waste heat in the above-mentioned drying, the carbon dioxide emissions can be further reduced.

[0029] Furthermore, in the above-described embodiment, although an example of activating only SA has been described, it is also possible to further mix any one or an arbitrary combination of blast furnace slag fine powder, FA, crushed waste concrete, and concrete sludge. This concrete sludge is cement sludge (concrete sludge) discharged from centrifugally formed concrete. Furthermore, it is also possible to use only blast furnace slag fine powder, FA, and crushed waste concrete without mixing SA. Thus, when using only blast furnace slag fine powder, FA, and crushed waste concrete, if the hardness is relatively lower than that of SA, it is also possible to use a ball having a density less than a specific density, such as an alumina ball, as the ball for ball mill mixing.

[0030] Here, the FA according to this embodiment is pozzolanic coal ash (fly ash) for concrete collected by a dust collector for pulverized coal combustion of coal in a thermal power plant. The FA according to this embodiment is preferably, for example, fly ash type II defined in JIS A 6201 or similar products thereof, having a density of about 2.20 g / cm 3 or so.

[0031] In addition, the blast furnace slag fine powder according to this embodiment is fine powder by-produced in the pig iron manufacturing process. This blast furnace slag fine powder is preferably, for example, the one having a specific surface area of powder fineness 4000 defined by JIS A 6206. Also, it is preferable that the density is about 2.91 g / cm 3 cm.

[0032] In addition, it is also possible to use the above-mentioned concrete sludge instead of the saturated calcium hydroxide solution or in addition to the saturated calcium hydroxide solution. Thereby, it is also possible to use it for applications as an aggregate that generates calcium carbonate and absorbs carbon dioxide.

[0033] 〔Method for manufacturing binder-containing composition〕 The method for manufacturing a binder-containing composition according to this embodiment is characterized by blending SA dry powder, which is an admixture manufactured by the above-mentioned admixture manufacturing method. More specifically, when manufacturing the mortar composition according to this embodiment, SA dry powder obtained by drying the activated SA slurry and / or the above-mentioned industrial waste that has absorbed carbon dioxide are used as admixtures, and a premix or mixture containing a binder and other admixtures (hereinafter simply referred to as "binder-containing composition") can also be prepared.

[0034] Here, the binder according to this embodiment may be a substance that contains cement, blast furnace slag fine powder, FA, silica fume, etc., reacts with water, and generates a substance that contributes to the development of the strength of concrete. Among these, as the cement according to this embodiment, it is possible to use ordinary Portland cement, blast furnace cement, fly ash cement, silica cement, and mixed cements thereof. Among these, the ordinary Portland cement may be various Portland cements having properties such as moderate heat, low heat, early strength, ultra-early strength, sulfate resistance, etc. Also, as the ordinary Portland cement, for example, with a density of 3.15 g / cm defined by JIS R 5210 etc. 3 about, and a specific surface area of 3310 cm 2Those with a / g level may also be used.

[0035] Here, in the silica fume according to the present embodiment, most of the dust collected as dust in the exhaust gas from the arc-type electric furnace is amorphous spherical silica (SiO2) or the like. This silica fume is preferably one having a density of 2.30 g / cm as defined in JIS A 6207. 3 It is preferably used for densification and strength improvement.

[0036] In addition, as the binder according to the present embodiment, it is also possible to use a substance for concrete that does not use Portland cement. This concrete that does not use Portland cement may be, for example, the concrete described in Patent Document 1. Furthermore, in addition to blast furnace slag fine powder, FA, and silica fume, it is possible to use a composition such as a composition for geopolymers, which is used as a binder for concrete in a broader sense by those skilled in the art. That is, the binder-containing composition according to the present embodiment can widely correspond to binders for cement-containing concrete and cementless concrete.

[0037] Here, in the binder-containing composition according to the present embodiment, the activated SA dry powder and the dried admixture are preferably blended so as to be an internal substitution of sand (fine aggregate) or cement at a mass ratio of 10% to 35% of the cement. This blending is preferably 15% to 30% in terms of the mass ratio of the cement because, as shown in the examples described later, the compressive strength is particularly the highest. Furthermore, in the case of a configuration that does not use Portland cement, such as the concrete composition described in Patent Document 1, it is possible to use an amount more than that of SA described in Patent Document 1.

[0038] Note that the binder-containing composition according to the present embodiment may also be provided in a form including any one or an arbitrary combination of fine aggregate and water reducing agent. In this case, the mixing ratio and the like may be changed depending on whether it is precast or cast on site.

[0039] 〔Mortar Composition and Concrete Manufacturing Method〕 It is possible to manufacture a mortar composition or concrete using the binder-containing composition manufactured by the method for manufacturing a binder-containing composition according to this embodiment. Specifically, water, fine aggregate, and other admixtures are added to the binder-containing composition according to this embodiment, or coarse aggregate is also added thereto, and the mixture is kneaded, molded, and cured to manufacture a mortar composition or concrete.

[0040] That is, as a concrete manufacturing method according to this embodiment, water, sand, and a saturated calcium hydroxide solution are mixed with SA and ball mill mixing is performed to produce an activated sewage sludge incineration ash slurry. The produced sewage sludge incineration ash slurry is dried by heating to obtain an admixture, and the dried admixture can be blended so as to be 10% to 35% by weight ratio of cement and to replace the internal proportion of sand or binder. Here, in the following examples, in order to confirm the strength improvement as an admixture, it is calculated as an internal replacement of sand to adjust the volume without changing the amount of binder. However, it is also possible to increase the strength as an internal replacement of the binder.

[0041] Here, as the fine aggregate according to this embodiment, crushed sand (sand) and calcium carbonate can be used. This sand can be the same sand as that used in the production of the above-described SA slurry or other sands in the cement field. Further, as the calcium carbonate, an environmentally friendly calcium carbonate manufactured using carbon dioxide extracted from the atmosphere and / or exhaust gas as a raw material may be used. In this case, it is also possible to use calcium carbonate obtained by reacting a calcium hydroxide solution and / or concrete sludge with carbon dioxide by the above-described carbon dioxide absorption method.

[0042] As the concrete according to this embodiment, in addition to SA dry powder, it is also possible to further include industrial waste that has absorbed carbon dioxide and use it. In this case, in addition to Portland cement, or in addition to Portland cement, it is also possible to include those having a configuration that hardens using geopolymers, pozzolanic reactions, or latent hydraulicity.

[0043] Here, when hardening concrete using a pozzolanic reaction or latent hydraulicity, an alkali stimulant for FA and blast furnace slag fine powder may be mixed. Since the main components of FA are silica and alumina, it can be hardened by a pozzolanic reaction that generates calcium silicate hydrate and the like with an alkali stimulant. Blast furnace slag fine powder can also be hardened by "latent hydraulicity" that generates calcium silicate hydrate and calcium aluminate hydrate with an alkali stimulant and hardens.

[0044] Here, as the above-mentioned alkali stimulant, it may mainly contain calcium carbonate (slaked lime) similar to that produced by the above-mentioned carbon dioxide absorption method. With this alkali stimulant, it is possible to harden FA and blast furnace slag fine powder with or without using Portland cement. Also, calcium carbonate that replaces sand or a binder as fine aggregate can be used as an alkali stimulant.

[0045] Furthermore, as the fine aggregate according to this embodiment, it is also possible to use slag-based aggregates, for example, fine aggregates produced from granulated blast furnace slag, electric furnace oxidized slag aggregates, silica fume, etc.

[0046] Also, as the coarse aggregate according to this embodiment, general coarse aggregates such as sandstone can be used. This coarse aggregate corresponds to, for example, JIS A 5005 crushed stone 2005 (hard sandstone), and it is preferable that the density is about 2.67 g / cm 3 or so.

[0047] In addition, in the production of the mortar composition or concrete of the present embodiment, fibers, water reducing agents, high-performance water reducing agents, fluidizing agents, retarders, waterproof admixtures, moisture-proof admixtures, foaming agents, thickeners, antifreezing agents, coloring agents, workability enhancers, anti-corrosion agents, defoaming agents, setting regulators, shrinkage reducing agents, cement accelerating agents, polymer emulsions, etc. can be appropriately blended.

[0048] The concrete according to the present embodiment may be manufactured by compacting by centrifugal forming, vibration molding, or placing on-site construction.

[0049] 〔Precast concrete〕 The concrete according to the present embodiment can be used for the production of precast concrete. This precast concrete is preferably used for products that particularly require strength. In this case, when manufacturing concrete products in a dedicated factory, by setting the composition and strength to be optimal, the manufacturing efficiency can be increased and the manufacturing cost can be optimized.

[0050] Here, the concrete according to the present embodiment may be manufactured by centrifugal forming or vibration molding. When compacting the concrete according to the present embodiment by centrifugal forming, a mixture of water, the above-mentioned binder-containing composition, expansion material, fine aggregate, coarse aggregate, and water reducing agent blended in the above-mentioned ratio (hereinafter simply referred to as "mixture") is filled into a mold for centrifugal forming, and the mold is rotated at high speed on a molding machine, and finally compacted at an acceleration of about 30 to 50 G using centrifugal force, and the excess water is discharged as sludge water (concrete sludge). At this time, the acceleration may be increased in several stages to compact so that the excess water is properly drained and compacted tightly. As this stage, for example, compact at 5 G, 15 G, and 35 G at a ratio of 1 minute, 1 minute, and 7 minutes, respectively. By manufacturing in this way by compacting with centrifugal forming, the strength of the concrete according to the present embodiment can be increased, and further, the time for steam curing can be shortened, and it becomes possible to manufacture high-performance cylindrical structures and the like. Note that it is also possible to add carbon dioxide to this concrete sludge and use it for the production of calcium carbonate described above.

[0051] Furthermore, in addition to the centrifugal molding described above, the concrete of the present embodiment can also be used as precast concrete formed by vibration. Examples of products formed by vibration molding include box culverts and manholes. Any of these products can be manufactured by the same manufacturing method as the manufacturing process of precast concrete such as hume pipes. That is, it can be manufactured simply by changing centrifugal molding to vibration molding. Therefore, the mixture of the present embodiment can also be applied to the production of precast concrete products formed by vibration.

[0052] If appropriate curing methods and temperature control are sufficiently carried out, it is also possible to place the mixture of the present embodiment on-site.

[0053] Here, the concrete of the present embodiment may have different required performances depending on the product to which it is applied. In this case, similar to the ratio of water (W) to cement (C) (W / C) in concrete, the ratio of water (W) to the total powder amount (P) of the mixture (W / P) can be finely adjusted to cope with it. Alternatively, instead of this W / P, it is also possible to adjust using the water (W) / binder (B) ratio (hereinafter referred to as "W / B"). Here, the W / B according to the present embodiment can be decreased or increased within a range that satisfies the required performances of strength and fluidity. In addition, it is possible to adjust the addition amount of the above-mentioned SA dry powder and other industrial waste to obtain a formulation corresponding to various requirements.

[0054] Also, if necessary, the fine aggregate ratio (s / a), the addition amount of admixture (Ad), etc. can be appropriately adjusted to match the fresh properties (slump: SL, air content: Air) of the mixture with the required performances of the product to which it is applied. Furthermore, the concrete according to this embodiment may be cured under high pressure and high temperature after molding. This curing may be, for example, an appropriate time for those skilled in the art of about 1 day to 28 days.

[0055] By configuring as described above, the following effects can be obtained. Conventionally, when attempting to add a large amount of SA slurry as described in Non-Patent Document 1 to concrete, since the adjustment of water above the unit water amount cannot be made, there was an upper limit to the addition amount of the SA slurry. Also, during transportation, etc., the sewage sludge incineration ash and sand in the SA slurry settled, and sufficient stirring was required during use, and facilities, etc. were also necessary. For this reason, it was not possible to use a large amount of SA slurry in the production of mortar compositions or concrete.

[0056] On the other hand, by producing SA dry powder obtained by drying the SA slurry according to this embodiment by heating and using it as an admixture, it becomes possible to add a larger amount than when mixing the SA slurry itself into concrete. That is, it can be used in large quantities in the production of mortar compositions or concrete. Moreover, when the SA dry powder is blended, it becomes possible to enhance the compressive strength compared to the conventional SA slurry. As a result, SA can be used in large quantities as a concrete admixture.

[0057] Also, in the conventional SA slurry, the aqueous solution of unreacted saturated calcium hydroxide contained reacts with the components of the sewage sludge incineration ash and gradually causes a curing reaction. Therefore, even when stabilized, there was a limit to the usable period. On the other hand, since the SA dry powder is below a specific moisture content, such an effect reaction hardly occurs, and the quality as an admixture can be maintained. For this reason, it can be packed in a highly barrier bag, etc., and can be stored for a longer period than the SA slurry and mixed when necessary. Thus, the convenience in production can be enhanced.

[0058] Also, when centrifugally molding an admixture composed of fine particles, the inner surface properties sometimes became a problem. In contrast, the SA dry powder according to this embodiment has good dispersibility, and as shown in the examples described later, even when added at 30%, the inner surface properties are good.

[0059] Furthermore, in the concrete according to this embodiment, since Ca by calcium hydroxide is added, it can be expected to enhance the activity of hardening. Furthermore, when calcium carbonate produced by appropriately containing carbon dioxide extracted from the atmosphere and / or exhaust gas as a raw material is added, it becomes possible to reduce carbon dioxide during concrete production as a result.

[0060] Note that the concrete according to this embodiment can be used for applications other than precast concrete. For example, the concrete according to this embodiment can also be used in ordinary construction, various production facilities, etc.

[0061] Next, the present invention will be further described with reference to examples based on the drawings, but the following specific examples do not limit the present invention.

Examples

[0062] (Materials used) The materials used are ordinary Portland cement (C: density 3.16 g·cm -3 ), sewage sludge incineration ash (SA: density 2.60 g·cm -3 , BET specific surface area 3.78 m 2 ·g -1 ), tap water (W), standard sand (S: for cement association strength test), saturated calcium hydroxide solution (sat.Ca(OH)2), manufactured by Kanto Chemical Co., Inc., special grade dissolved). The chemical composition of SA used in this example is shown in Table 1 below. The unit is mass%.

[0063]

Table 1

[0064] (Manufacturing procedure) First, the manufacturing procedure of SA dry powder will be described. The powder added with SA was put into a 500 ml wide-mouth reagent bottle and mixed in a ball mill. Then, it was kneaded with a mortar mixer, molded in a 4·4·16 mold, and pre-cured. After that, it was demolded and cured in water (water temperature 20°C), and a compression test was conducted. Hereinafter, the details of these processes will be described.

[0065] First, for ball mill mixing, 25% by mass of ordinary Portland cement compliant with JIS A 6201 was replaced with SA, and SA was also replaced in the same way for comparison. The procedure for ball mill mixing was to add SA, saturated calcium hydroxide solution, water, standard sand, and stainless steel balls to a wide-mouth reagent bottle (outer diameter 73 mm, length 168 mm, internal volume 500 ml, made of low-density polyethylene), and use a two-stage ball mill rotating stand for mixing to prepare SA slurry.

[0066] The ball mill mixing conditions during SA slurry preparation were based on the optimal mixing method of conventional FA and were set as follows. (1) The rotation speed of the rotating stand was 30 rpm, (2) the mixing time was 1 hour, and with respect to the mass of the admixture, (3) the amount of saturated calcium hydroxide solution was 50%, (4) the amount of water was 62%, and (5) the amount of sand was 44%. The formulation (Admixture) of ball mill mixing and the ball mill mixing conditions are shown in Table 2 below.

[0067]

Table 2

[0068] Thereafter, the manufactured SA slurry was heated and dried for a whole day and night at about 90°C to 110°C until it reached a predetermined mass. This drying method complied with the sieve analysis test method for aggregates of JIS A 1102:2014. Thereby, SA dry powder, which is an admixture obtained by drying SA slurry, was manufactured.

[0069] (Compressive Strength Test) Specimens were prepared by vibration molding or centrifugal molding of mortar added with SA dry powder, and their strength characteristics were confirmed. As a mixture, mortar (hereinafter referred to as "admixture-added mortar") was prepared by adding SA dry powder (SA powder) in the range of 0% to 30% by weight to replace fine aggregate with respect to cement. In the following tables and figures, those with an SA dry powder substitution rate (SA substitution rate) of 0% are shown as "No. 1", 10% as "No. 2", 15% as "No. 3", 20% as "No. 4", and 30% as "No. 5".

[0070] For the preparation of specimens, referring to JIS R 5201, the remaining water and standard sand were added and kneaded. Kneading was performed using a JIS mortar mixer. After that, in vibration molding, the fresh mixture was filled in two layers into a cylindrical mold made of tin (φ100×200 mm), and while applying vibration with a table vibrator, it was compacted in two layers to prepare a specimen of a cylindrical hardened body. On the other hand, in centrifugal molding, the fresh mixture was filled into a centrifugal molding mold (φ200×300 mm), the mold was rotated at high speed on a molding machine, and it was compacted using centrifugal force at an acceleration close to 40G, and the excess water in the mixture was discharged as sludge water. At this time, at the acceleration and molding time shown in Table 3 below, the acceleration was increased in several steps for compaction to prepare a specimen of a centrifugal hardened body. The formulation of the admixture-added mortar is shown in Table 3 below.

[0071]

Table 3

[0072] In terms of fresh properties, although the amount of water reducing agent used to obtain the same workability increased compared to mixing SA slurry into mortar without drying it, it was within an appropriate range of use. After molding these specimens, steam curing was performed under the conditions shown in Table 4 below.

[0073]

Table 4

[0074] Thereafter, each specimen was demolded and cured in water at 20°C for 28 days, and the compressive strength was measured on the 7th, 14th, 21st, and 28th days.

[0075] The compression test was carried out in accordance with JIS R 5201. Six specimens were measured each time, and the average value was taken as the measured value.

[0076] (Results of vibration molding) Table 5 below shows the measurement results of the compressive strength (N / mm 2 ) for each age (days) of the specimens (No. 1 to No. 5) prepared by vibration molding.

[0077] [Table 5]

[0078] Figure 1 shows a graph of each value in Table 5. In the graph, the horizontal axis represents the age (days), and the vertical axis represents the compressive strength (N / mm 2 ).

[0079] Regarding this graph, the relative compressive strength ratio (%) when the age of 28 days of the SA dry powder without mixing (No. 1) is set to 100% is shown in Table 6 below.

[0080] [Table 6]

[0081] Figure 2 shows a graph of each value in Table 6. In the graph, the horizontal axis represents the age (days), and the vertical axis represents the relative compressive strength ratio.

[0082] Also, the relative compressive strength ratio (%) when the same each value is set to 100% at the time of demolding (age 1 day) is shown in Table 7 below.

[0083] [Table 7]

[0084] Figure 3 shows a graph of each value in Table 7. In this graph, the horizontal axis represents the SA addition rate (%), and the vertical axis represents the relative compression strength. The nuclear series indicates that triangles represent the time of demolding and an age of 1 day, squares represent an age of 7 days, circles represent an age of 14 days, and diamonds represent an age of 28 days.

[0085] The compressive strength of the concrete in the vibration-molded specimens increased with the substitution rate of SA dry powder reaching a peak around 20%. However, sufficient strength was also obtained in No. 5 with a 30% substitution.

[0086] (Results of centrifugal molding) Next, a compressive strength test was also conducted on specimens (centrifugally molded specimens) obtained by centrifugally molding the same batch of concrete. The results are shown in Table 8 below.

[0087]

Table 8

[0088] Figure 4 shows a graph of each value in Table 8. In the graph, the horizontal axis represents the SA substitution rate (%), and the vertical axis represents the compressive strength (N / mm 2 ). In centrifugal molding, excess water is dehydrated and the apparent water-cement ratio (W / C) becomes smaller, so the compressive strength increases compared to vibration molding. Also in this example, in the centrifugally molded specimens replaced with SA dry powder, the compressive strength increased by about 2% - 10%. Thus, even when SA dry powder was added, no influence on the compressive strength due to centrifugal molding was observed.

[0089] Next, since SA dry powder is composed of fine particles, the inner surface properties during centrifugal molding were observed. Figure 5 shows the inner surface of the centrifugally molded specimens. The inner surface properties were normal at any substitution rate from No. 1 to No. 5, and even when 30% of SA dry powder was added, there were no particular problems with the formability of the inner surface.

[0090] It goes without saying that the configurations and operations of the above embodiments are examples, and can be appropriately changed and implemented without departing from the gist of the present invention.

Claims

1. A method for producing an admixture for concrete containing sewage sludge incineration ash, comprising: mixing water, sand, and a saturated calcium hydroxide solution with the sewage sludge incineration ash and performing ball mill mixing to produce an activated sewage sludge incineration ash slurry; drying the sewage sludge incineration ash slurry by heating. A method for producing an admixture, characterized by the above.

2. In the ball mill mixing: the rotation speed of the rotating mount is 30 rpm to 50 rpm; based on the mass of the sewage sludge incineration ash, the water is 25% to 200%, the sand is 40% to 80%, and the amount of the saturated calcium hydroxide solution is 20% to 80%; the mixing time of the ball mill mixing is 0.3 to 2 hours; the average particle size of the sewage sludge incineration ash is 5 μm or less; by the ball mill mixing, a state where layered crystals adhere to the surface of the particles is achieved; the drying by heating is carried out at 90°C to 110°C for at least one day and night. A method for producing an admixture according to Claim 1, characterized by the above.

3. Mixing the admixture according to Claim 1 or 2 and a binder. A method for producing a binder-containing composition, characterized by the above.

4. The dried admixture is blended at a mass ratio of 10% to 35% of cement so as to be an internal substitution of sand or the binder. A method for producing a binder-containing composition according to Claim 3, characterized by the above.

5. Producing a mortar composition using the binder-containing composition produced by the method for producing a binder-containing composition according to Claim 4. A method for producing a mortar composition, characterized by the above.

6. A method for producing concrete containing sewage sludge incineration ash, comprising: mixing water, sand, and a saturated calcium hydroxide solution with the sewage sludge incineration ash and performing ball mill mixing to produce an activated sewage sludge incineration ash slurry; drying the sewage sludge incineration ash slurry by heating to obtain an admixture; blending the dried admixture at a weight ratio of 10% to 35% of cement so as to be an internal substitution of sand or a binder. A method for producing concrete, characterized by the above.

7. Producing precast concrete using the concrete produced by the method for producing concrete according to Claim 6. A method for producing precast concrete, characterized by the above.

8. Performing centrifugal molding during production. A method for producing precast concrete according to Claim 7, characterized by the above.

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