Method for producing carbon dioxide absorbing sludge fine powder, and method for producing a water-curable cured body.

Abstract

[Problem] To provide a manufacturing method for a carbon dioxide absorbed sludge fine powder that has high fluidity and serves as a binder of low carbon materials. [Solution] In the present invention, water is added to residual concrete or return concrete to obtain a slurry; sand and gravel are separated and removed to obtain sludge water; a fine sand component is separated and removed from the sludge water by a wet cyclone to obtain concentrated sludge water; and the concentrated sludge water is dewatered to obtain a sludge cake. The sludge cake is placed in a rotating drum into which heated air and high-concentration carbon dioxide are supplied, and the sludge cake is pulverized and dried while being caused to absorb the carbon dioxide to obtain a carbon dioxide absorbed sludge fine powder. Alternatively, the sludge cake is placed in the rotating drum, heated air is supplied, and the sludge cake is pulverized and dried to obtain a sludge fine powder. This sludge fine powder is exposed to high-concentration carbon dioxide to obtain a carbon dioxide absorbed sludge fine powder.

Description

Technical Field

[0001] The present invention relates to a manufacturing method for obtaining fine powder that can be used as a binder by subjecting sludge cake containing cement content recovered from residual concrete or returned concrete, from which aggregate and fine sand have been removed and dehydrated, to predetermined treatment, the fine powder, and a water-curable hardened body obtained using the fine powder as a binder.

Background Art

[0002] Concrete, mortar, etc. placed at a construction site or the like are manufactured at a ready-mix concrete plant and transported by an agitator truck. Concrete that has not been used at the construction site or that has failed in the acceptance inspection is returned to the plant as so-called residual concrete or returned concrete, and it has been reported that this reaches 2 to 3% of the total concrete. Conventionally, these have been treated as industrial waste, but due to the increasing costs and environmental burden, effective utilization has been demanded.

[0003] In recent years, in order to prevent global warming, reduction of carbon dioxide emissions has been required in each field of industry. Looking at the cement manufacturing industry, which accounts for about 4% of the total carbon dioxide emissions in Japan, the carbon dioxide emissions from cement manufactured by high-temperature firing are large, reaching about 766 kg / ton in terms of the unit amount. In order to suppress carbon dioxide emissions, it is expected to establish technologies for reducing the amount of cement used or substituting a part of the cement with a binder made of other low-carbon materials.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] Patent Document 1 describes a method for recovering sludge fine powder with a high proportion of unhydrated cement from residual concrete and returned concrete. Specifically, water is added to the residual concrete and returned concrete to form a slurry, gravel and sand are removed from this slurry, and then fine sand is removed using a wet cyclone to obtain sludge water. Next, the sludge water is dewatered to obtain a dewatered cake, and this dewatered cake is placed in a rotating drum and crushed and dried simultaneously while supplying high-temperature air. Because crushing and drying are performed simultaneously, the progress of the hydration reaction is suppressed, and high-quality sludge fine powder with a high proportion of unhydrated cement is obtained. Sludge fine powder can be used as a binder that can replace part of the cement, as proposed in Patent Document 2, for example.

[0006] Patent Document 3 describes a method for obtaining a cement bulking agent by sieving crushed concrete waste or sludge generated in the concrete manufacturing process to recover the fine powder portion, and then actively absorbing carbon dioxide into this fine powder portion. However, when the fine powder portion is used as a cement bulking agent before carbon dioxide absorption, it has the problem of having a very high water absorption rate, which reduces its workability. Nevertheless, by treating the fine powder portion in a carbon dioxide gas atmosphere to carbonize it, a cement bulking agent that does not cause a decrease in workability can be obtained. [Overview of the project] [Problems that the invention aims to solve]

[0007] The sludge powder described in Patent Document 1 is obtained from waste materials such as residual concrete and returned concrete, and consumes little fuel during crushing and drying, making it a binder for low-carbon materials. Therefore, replacing part of the cement with sludge powder in a water-curable hardened body is advantageous because it can reduce carbon dioxide emissions. However, it appears that there is room to further reduce carbon dioxide emissions from sludge powder. However, increasing the amount of sludge powder used in an attempt to further reduce carbon dioxide emissions presents the challenge of reduced workability, i.e., fluidity.

[0008] The cement extender described in Patent Document 3 is excellent because it can be used without reducing the workability of concrete. Furthermore, it is excellent in that it absorbs carbon dioxide, thereby reducing carbon dioxide emissions. However, the cement extender described in Patent Document 3 cannot be expected to act as a binder, and even if it partially replaces the cement used in water-hardening bodies, the proportion is not large. This is because the method of recovering the fine powder portion from sludge described in Patent Document 3 only sieves the sludge to extract the fine powder portion, and does not substantially remove the fine sand. As a result, there are problems with the proportion of cement in the fine powder portion not being large, and the ratio of fine sand to cement portion being unknown. Therefore, even if one were to try to use the fine powder portion as a binder, it would be difficult to determine the amount to mix in order to obtain the required strength, making its use as a binder difficult.

[0009] Furthermore, the proportion of unhydrated cement in the cement content of the fine powder portion described in Patent Document 3 is also unclear. This is because Patent Document 3 does not describe how the fine powder portion is dried and turned into fine powder, and it is assumed that it is processed using a general method. In a general method, sludge is dewatered to obtain a dewatered cake, which is then dried and crushed to obtain the fine powder portion. In other words, crushing and drying are not performed simultaneously. When the fine powder portion is obtained by this method, the hydration reaction proceeds and the proportion of unhydrated cement in the total cement content inevitably becomes small. For example, as described in the paper "1. A Study on the Activity and Effective Utilization of Dried and Finely Crushed Ready-Mix Concrete Sludge (Cement and Concrete Papers No. 51 1997)", the fine powder portion obtained by a general method does not provide sufficient strength when used as a binder. In other words, the fine powder portion described in Patent Document 3 is practically unsuitable for use as a binder. Furthermore, the fine powder portion described in Patent Document 3 is only added to concrete at a concentration of about 5% in the examples described in this document, and there is also the problem that the effect on reducing carbon dioxide emissions is not significant to begin with.

[0010] This invention provides a method for producing carbon dioxide absorbing sludge fine powder, a binder that can suppress carbon dioxide emissions from residual concrete and returned concrete and possesses excellent performance. [Means for solving the problem]

[0011] This invention provides a carbon dioxide-absorbing sludge fine powder with a high proportion of unhydrated cement and carbon dioxide absorption from residual concrete or returned concrete. Composition as a manufacturing methodSpecifically, water is added to the remaining concrete or returned concrete to make a slurry. Then, gravel and sand are separated and removed from the slurry to obtain sludge water, and fine sand is separated and removed from the sludge water using a wet cyclone to obtain concentrated sludge water. This concentrated sludge water is dewatered to obtain sludge cake. The sludge cake is placed in a rotating drum and crushed and dried by supplying hot air to obtain sludge fine powder, and the sludge fine powder is exposed to a high concentration of carbon dioxide to absorb carbon dioxide and obtain carbon dioxide absorbing sludge fine powder. The sludge fine powder before carbon dioxide absorption has a specific surface area of ​​11,000 cm². 2 The quality must be less than / g, and the carbon dioxide absorption time must be within 6 hours. If mortar were manufactured using only this carbon dioxide-absorbing sludge fine powder as a binder, the compressive strength at 28 days would be 31.6 N / mm². 2 The above describes the carbon dioxide absorbing sludge fine powder. [Effects of the Invention]

[0012] The present invention provides a binder that reduces carbon dioxide emissions. Furthermore, the carbon dioxide-absorbing sludge powder produced according to the present invention has improved workability compared to sludge powder that has not absorbed carbon dioxide. [Brief explanation of the drawing]

[0013] [Figure 1] This is a flowchart showing the method for producing carbon dioxide absorbing sludge fine powder according to the first embodiment of this implementation. [Figure 2] This is a flowchart showing the method for producing carbon dioxide absorbing sludge fine powder according to the second embodiment of this implementation. [Figure 3] This is a microscopic image of sludge powder before carbon dioxide absorption. [Figure 4] This graph shows the relationship between the specific surface area and the proportion of unhydrated cement in sludge fine powder before carbon dioxide absorption. [Figure 5]A graph showing the relationship between the temperature inside the container and the mortar flow during the absorption when sludge fine powder absorbs carbon dioxide for a certain period of time.

Embodiments for Carrying Out the Invention

[0014] <Method for Producing Carbon Dioxide-Absorbing Sludge Fine Powder According to the First Embodiment> The method for producing carbon dioxide-absorbing sludge fine powder according to the first embodiment of the present implementation will be described. Concrete is produced by forcibly kneading ordinary Portland cement, aggregates such as gravel and sand, water, and admixtures with a forced kneading mixer. The concrete thus produced is transported to the construction site and placed, but in some cases, a part of it may remain unused or may fail the acceptance inspection. Such concrete is returned to the ready-mix concrete plant as residual concrete or return concrete, or sent to other treatment facilities. Such residual concrete or return concrete is processed to produce carbon dioxide-absorbing sludge fine powder.

[0015] As shown in FIG. 1, the slurrying step S1 is carried out to slurry the residual concrete or return concrete. That is, water is added to the residual concrete or return concrete to slurry it. This enables the cement component to dissolve sufficiently in the added water. The slurry may contain washing wastewater from washing the mixer of the agitator truck or washing wastewater in the ready-mix concrete plant.

[0016] Next, the aggregate separation process S2 is carried out. This process removes solid components such as aggregates from the slurry obtained in the slurrying process S1. This is done using multiple vibrating screens with different mesh sizes, sequentially processing the slurry to separate aggregates such as gravel and sand. The recovered aggregates are reused. The residue remaining after the aggregates have been separated is sludge water containing a large amount of cement. Following the aggregate separation process S2, the fine sand removal process S3 is carried out. In this embodiment, this process is carried out using a wet cyclone to remove fine sand, i.e., fine sand, from the sludge water. That is, concentrated sludge water is obtained. The concentrated sludge water obtained in this process is processed in the next dewatering process S4. However, if the cement content in the concentrated sludge water is low, it may be sent to the slurrying process S1 and reused as water to slurry other remaining concrete or returned concrete. In this way, the cement content of the sludge water is concentrated. Dewatering treatment S4 is carried out on the concentrated sludge water. That is, the concentrated sludge water is processed by a filter press to obtain a sludge cake. At this time, supernatant water is also obtained, which can be reused as mixing water for concrete.

[0017] The manufacturing method according to the first embodiment performs a crushing, drying, and carbon dioxide absorption step S5 on the sludge cake. That is, the sludge cake is crushed and dried while supplying high-concentration carbon dioxide thereto. Any device may be used as long as high-concentration carbon dioxide can be supplied to the sludge cake and crushing and drying can be performed simultaneously. However, in the present embodiment, a predetermined rotating drum that can efficiently perform crushing and drying and can absorb carbon dioxide is used. The rotating drum is provided with crushing and stirring blades that rotate at high speed inside and is configured to be able to supply hot air and high-concentration carbon dioxide. The concentration of carbon dioxide in the rotating drum is set to be 5% or more and 90% or less by volume ratio with respect to air. Also, the temperature is set to be 50°C or more and 400°C or less. When the sludge cake is put into the rotating drum for treatment, the sludge cake is crushed by the crushing and stirring blades, dried by the hot air, and absorbs carbon dioxide. Thereby, carbon dioxide-absorbing sludge fine powder is produced. In the crushing, drying, and carbon dioxide absorption step S5, since the crushing, drying, and carbon dioxide absorption of the sludge cake are substantially performed simultaneously, carbon dioxide-absorbing sludge fine powder with a large amount of unhydrated cement component, which suppresses the progress of the hydration reaction of the cement component, is obtained.

[0018] Incidentally, the sludge cake processed by the crushing, drying, and carbon dioxide absorption process S5 is required to possess a predetermined quality. In practice, the sludge cake is processed by the crushing, drying, and carbon dioxide absorption process S5 described above, but the condition is that it should be of the quality of the sludge powder that would be obtained if it were processed by another method. This other method of processing also uses the rotating drum described above. However, carbon dioxide is not supplied to the rotating drum, only high-temperature air is supplied. By crushing and drying the sludge cake without supplying carbon dioxide in this way, sludge powder should be obtained. The sludge powder obtained in this way is in the state shown in the micrograph in Figure 3. This micrograph is described in the paper "Development of Ready-Mixed Concrete Using Dried Sludge Powder as an Admixture (Kajima Technical Research Institute Annual Report No. 66, published December 1, 2018)". The sludge powder contains some fine sand, but it can be seen that it contains a relatively large amount of aggregated hydration products generated when cement is hydrated, and unhydrated cement.

[0019] This paper also includes the graph shown in Figure 4. By solidifying sludge fine powder with resin and cutting it, the proportion of each substance can be determined by examining the cross-sectional area occupied by each substance. Figure 4 shows the ratio of the cross-sectional area of ​​unhydrated cement to the total sludge fine powder for various sludge fine powders with different specific surface areas. The specific surface area here was measured using a Blaine permeation apparatus as specified in JIS R 5201 Cement Physical Testing Methods. This method is a test that derives the specific surface area of ​​powder from the airflow, based on the assumption that "in a bed of powder consisting of spherical particles, the total internal area of ​​the path through which the gas passes is equal to the total surface area of ​​the powder, and the total volume of the path is equal to the void volume of the bed." When this test is performed on sludge fine powder, coarse aggregates such as hydration products are present around the cement, so the specific surface area obtained from the test is large because air passes through the coarse aggregates during the test. Therefore, the more aggregates of hydrated sludge powder there are, and the less unhydrated cement there is, the higher the specific surface area. As shown in this graph, for sludge powder usable as a binder, the unhydrated cement accounts for 50% or more of the cross-sectional area of ​​the total sludge powder. At this point, the specific surface area is 12,000 cm². 2 It is guaranteed to be less than / g, and the proportion of unhydrated cement is high. In particular, if the cross-sectional area ratio is 55% or more, the specific surface area is 11,000 cm². 2 The amount is less than / g, and the proportion of unhydrated cement is high. Therefore, in the manufacturing method according to this embodiment, the sludge cake to be processed in the crushing, drying, and carbon dioxide absorption step S5 is such that, if the sludge cake is crushed and dried to obtain sludge fine powder, the ratio of the cross-sectional area of ​​unhydrated cement to the total sludge fine powder is 50% or more, more preferably 55% or more.

[0020] <Method for producing carbon dioxide-absorbing sludge fine powder according to the second embodiment> The method for producing carbon dioxide absorbing sludge fine powder according to the second embodiment of this implementation will be described. The manufacturing method according to the second embodiment of this implementation is shown in Figure 2, and most of the steps are the same as the manufacturing method according to the first embodiment. Specifically, the slurrying step S1, aggregate separation step S2, fine sand removal step S3, and dewatering step S4 are the same steps. Therefore, the explanation of these steps will be omitted. The crushing and drying step S11 will be explained first.

[0021] The manufacturing method according to the second embodiment involves performing a crushing and drying step S11 on the sludge cake. The apparatus used in this step can be any apparatus that crushes and dries the sludge cake, but the rotary drum used in the manufacturing method according to the first embodiment can be used. The sludge cake is placed in the rotary drum and rotated while hot air is supplied. As a result, the sludge cake is crushed by the crushing and stirring blades and dried by the hot air to obtain sludge fine powder. In this sludge fine powder, the cross-sectional area ratio of unhydrated cement to the total sludge fine powder is 50% or more.

[0022] The sludge fine powder obtained in this way is subjected to the carbon dioxide absorption step S12. In the carbon dioxide absorption step S12, the sludge fine powder is placed in a container equipped with a stirring means, a high concentration of carbon dioxide is supplied into the container, and the temperature inside the container is raised to 50°C or higher. When exposed to carbon dioxide for a predetermined time, for example, 30 minutes or more, or 1 hour or more, while stirring, the sludge fine powder absorbs carbon dioxide. In other words, carbon dioxide-absorbing sludge fine powder is obtained.

[0023] In the manufacturing method according to this second embodiment, waste heat may be recovered from the rotating drum in the crushing and drying step S11, and the recovered waste heat may be used in the carbon dioxide absorption step S12 to heat the container. Utilizing waste heat saves energy accordingly. In other words, it is possible to further reduce carbon dioxide emissions.

[0024] <Properties of carbon dioxide absorbing sludge fine powder> The carbon dioxide-absorbing sludge fine powder produced by the manufacturing methods according to the first and second embodiments can be used as a binder. When using carbon dioxide-absorbing sludge fine powder as a binder to mix mortar, etc., it has higher fluidity and superior workability compared to when using sludge fine powder that has not absorbed carbon dioxide, i.e., sludge fine powder obtained in the crushing and drying step S11 of the manufacturing method according to the second embodiment, as a binder. Furthermore, a water-curable hardened body can be obtained using carbon dioxide-absorbing sludge fine powder as a binder. Carbon dioxide-absorbing sludge fine powder not only improves workability compared to sludge fine powder, but because it absorbs carbon dioxide, it can be said to be a low-carbon material with low carbon dioxide emissions. [Examples]

[0025] Experiments were conducted to investigate how much carbon dioxide a sludge powder can absorb over time, and how its quality changes as a result of this absorption. Experimental method: To conduct experiments with sludge fine powders having different specific surface areas, steps S1 to S11 of the method for producing carbon dioxide-absorbing sludge fine powder according to the second embodiment shown in Figure 2 were carried out on three types of residual concrete A, B, and C, which differed in the time from concrete mixing to step S1, to obtain sludge fine powders A0, B0, and C0 that had not absorbed carbon dioxide. These sludge fine powders A0, B0, and C0 were each placed in experimental containers, and the carbon dioxide concentration in the containers was adjusted to 80% by volume ratio with air, and the temperature inside the containers was set to 50°C to allow carbon dioxide absorption, obtaining carbon dioxide-absorbing sludge fine powders A3, B3, and C3 with an absorption time of 3 hours. Similarly, carbon dioxide-absorbing sludge fine powders A6, B6, C6, A12, B12, C12, ..., A24, B24, and C24 with carbon dioxide absorption times of 6 hours, 12 hours, 18 hours, and 24 hours, respectively. For each of the obtained sludge powders A0, B0, and C0, the specific surface area and density were measured. For each of the carbon dioxide-absorbing sludge powders A3-A24, B3-B24, and C3-C24, the amount of carbon dioxide absorbed (by weight) was measured and summarized in Table 1. Note that the specific surface area and density of A, B, and C are for sludge powders A0, B0, and C0 before carbon dioxide absorption.

[0026] [Table 1]

[0027] Consideration: It was confirmed that carbon dioxide absorbing sludge fine powders A3-A24, B3-B24, and C3-C24 all absorb carbon dioxide, and that the amount of carbon dioxide absorbed increases with longer absorption time. When comparing the amount of carbon dioxide absorbed over the same absorption time, carbon dioxide absorbing sludge fine powders C3-C24, which had the largest specific surface area before carbon dioxide absorption (C0), absorbed the most carbon dioxide, while carbon dioxide absorbing sludge fine powders A3-A24, which had the smallest specific surface area (A0), absorbed the least. This is because cement hydration products adhere to the unhydrated cement particles as rough aggregates in a film-like structure, and the more hydration products there are, the larger the specific surface area. In other words, a larger specific surface area means more hydration products. Since these hydration products absorb carbon dioxide, it is thought that C0, with its large specific surface area and abundant hydration products, absorbs more carbon dioxide over the same absorption time compared to A0 and B0. [Examples]

[0028] Experiments were conducted to investigate the performance of the sludge powders A0, ... and carbon dioxide-absorbing sludge powders A3, ... obtained in the experiment of Example 1 when used as binders. Experimental method: The sludge powders A0, B0, C0, and carbon dioxide-absorbing sludge powders A3, B3, ..., C24 obtained in the experiment of Example 1 were used as binders, and mortar was mixed in accordance with the Japanese Industrial Standard JIS R5201. The flow value of each mortar was investigated in accordance with JIS R5201. These mortars were then hardened, and their compressive strength at 28 days was investigated. The results are summarized in Table 2.

[0029] [Table 2]

[0030] Consideration: Regarding fluidity, it was confirmed that the flow values ​​of mortars using carbon dioxide-absorbing sludge powders A3, A6, ..., C24 as binders increased (improved) as the carbon dioxide absorption time increased from 3 hours, 6 hours, ..., to 24 hours. In other words, it was confirmed that the workability of mortars using sludge powder as a binder is improved by allowing carbon dioxide to be absorbed by the sludge powder.

[0031] However, the degree of change in flow value was greatest for carbon dioxide-absorbing sludge powders C3-C24 in C0, which has the largest specific surface area, and smallest for carbon dioxide-absorbing sludge powders A3-A24 in A0, which has the smallest specific surface area. The reason for this is that in sludge powders A0, B0, and C0 before carbon dioxide absorption, the cement hydration products adhere to the unhydrated cement particles as aggregates in a film-like manner. A large amount of hydration products increases the specific surface area, and a large portion of the water in the mortar is incorporated into the hydration products, reducing fluidity. When carbon dioxide is absorbed into sludge powders A0, B0, and C0, which have low fluidity, the hydration products absorb the carbon dioxide and crystallize calcium carbonate and other substances, making it difficult for them to absorb water from the mortar, thus improving fluidity. Therefore, sludge powder C0, which has the largest specific surface area before carbon dioxide absorption, has poorer fluidity and the lowest flow value compared to A0 and B0 due to the larger amount of hydrated products. However, sludge powders C3 to C24, after carbon dioxide absorption, show a significant improvement in fluidity as carbon dioxide absorption progresses, and the improvement in flow value is even greater. In contrast, sludge powder A0, which has the smallest specific surface area before carbon dioxide absorption, shows a small improvement in flow value due to carbon dioxide absorption because it originally contains a small amount of hydrated products.

[0032] Furthermore, in all three cases (A0, B0, and C0), the magnitude of the improvement in flow values ​​converged after an absorption time of about 6 hours, and thereafter, the flow values ​​hardly changed even when the absorption time was increased. When considering a favorable flow value for mortar using sludge powder as a binder, we can refer to mortar using ordinary Portland cement as a binder. When manufacturing mortar from ordinary Portland cement, the flow value is generally 160 mm to 170 mm. However, mortars using carbon dioxide absorbing sludge powders A3, B3, ..., C24 as binders all have a flow value of 170 mm or more, which can be considered a favorable result. From this, it can be seen that if the temperature inside the container is 50°C, carbon dioxide absorbing sludge powder that is sufficiently fluid and usable as a binder can be obtained by absorbing carbon dioxide for more than 3 hours. [Examples]

[0033] An experiment was conducted to investigate how the temperature inside the container during carbon dioxide absorption affects the efficiency of carbon dioxide absorption when carbon dioxide is absorbed by sludge powder. Experimental method: Sludge powder D0 was obtained from residual concrete D in the same manner as in the experiment of Example 1. This sludge powder D0 was placed in an experimental container and carbon dioxide was absorbed in the same manner as in the experiment of Example 1. However, the carbon dioxide absorption time was set to 1 hour, and only the temperature inside the container during absorption was varied. For three patterns of temperature inside the container during absorption (30°C, 100°C, and 300°C), carbon dioxide absorbing sludge powders D1-30, D1-100, and D1-300 were obtained, respectively. These powders D0, D1-30, D1-100, and D1-300 were then used as binders, and mortar was mixed in accordance with the Japanese Industrial Standard JIS R5201, and the flow value was investigated in accordance with JIS R5201. Furthermore, these mortars were hardened, and the compressive strength at 28 days of age was investigated. Table 3 summarizes the carbon dioxide absorption (by weight), mortar flow value, and mortar strength for these fine powders D0, D1-30, D1-100, and D1-300. Note that the specific surface area and density of D are for sludge fine powder D0 before carbon dioxide absorption.

[0034] [Table 3]

[0035] Consideration: As can be seen from the table, when comparing samples with the same absorption time (1 hour), it can be confirmed that the amount of carbon dioxide absorbed increases as the temperature inside the container during absorption increases, and furthermore, the flow value of the mortar increases. To further investigate the flow value of the mortar, the carbon dioxide absorbing sludge fine powders D1-30, D1-100, and D1-300 were plotted with the temperature inside the container on the x-axis and the flow value on the y-axis, and the graph in Figure 5 was obtained. As can be seen from the graph, the flow value of the mortar increases in proportion to the temperature inside the container during carbon dioxide absorption. As mentioned above, referring to the flow value of mortar using ordinary Portland cement as a binder, a flow value of 170 mm or more for mortar using sludge fine powder as a binder is preferable, so it can be seen that a favorable flow value can be obtained if the temperature inside the container during carbon dioxide absorption is 160°C or higher. From this, it can be seen that when the carbon dioxide absorption time is short, such as 1 hour, a favorable carbon dioxide absorbing sludge fine powder can be obtained by absorbing carbon dioxide at a container temperature of 160°C or higher. [Industrial applicability]

[0036] The carbon dioxide absorbing sludge fine powder according to this embodiment can be used as a ground improvement material or as a solidifying agent added to fluidized soil.

Claims

1. A slurrying process involves adding water to the remaining concrete or returned concrete to make a slurry, A separation step to separate and remove gravel and sand from the slurry to obtain sludge water, A step to remove fine sand particles from the sludge water using a wet cyclone to obtain concentrated sludge water, A dehydration step to obtain a sludge cake by dehydrating the concentrated sludge water, A crushing and drying process is performed by placing the sludge cake in a rotating drum and supplying hot air to crush and dry it to obtain fine sludge powder. A method for producing carbon dioxide-absorbing sludge powder, comprising a carbon dioxide absorption step of exposing the sludge powder to a high concentration of carbon dioxide to absorb carbon dioxide and obtain carbon dioxide-absorbing sludge powder, The carbon dioxide absorption process has a specific surface area of ​​11,000 cm². ２ The sludge fine powder, of a quality of less than / g, is made to absorb carbon dioxide within an absorption time of 6 hours or less. When mortar is manufactured using only the carbon dioxide-absorbing sludge fine powder as a binder, the compressive strength at 28 days is 31.6 N / mm². ２ The above describes a method for producing carbon dioxide absorbing sludge fine powder.

2. The carbon dioxide absorption process has a specific surface area of ​​8000 cm². ２ A method for producing carbon dioxide-absorbing sludge powder according to claim 1, wherein carbon dioxide is absorbed by the sludge powder having a quality of less than / g.

3. The crushing and drying process is designed to recover the waste heat generated from the rotating drum. The method for producing carbon dioxide absorbing sludge powder according to claim 1 or 2, wherein the carbon dioxide absorption step is carried out while stirring the sludge powder and the high-concentration carbon dioxide, and while heating using the waste heat.

4. A method for producing a water-curable cured body, comprising containing, at least as part of a binder, carbon dioxide absorbing sludge fine powder produced by the method for producing carbon dioxide absorbing sludge fine powder described in claim 1 or 2.

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