Method for producing water-curable cured body containing blast furnace slag fine powder as binder

Abstract

To provide a method for producing a water-curable cured body which contains blast furnace slag fine powder as a main binder, has a high CO2 reduction effect and can obtain sufficiently high strength, and a small bleeding amount.SOLUTION: A water-curable cured body is obtained from a binder in which blast furnace slag finer powder has a first mass ratio MR1st, concrete sludge fine powder has a second mass ratio MR2nd and Portland cement has a third mass ratio MR3rd, according to the following conditions (A) to (C). (A) The MR1st satisfies 40%≤MR1st≤70%. (B) as for the MR2nd, a specific surface area of the concrete sludge fine powder is 8,000 cm2 / g or less, it satisfies 10%≤MR2nd≤40%, MR2nd≤100%-MR1st and MR2nd≤MR1st, when the specific surface area of the concrete sludge fine powder is 8,000 cm2 / g or more and 10,000 cm2 / g or less, it satisfies 5%≤MR2nd≤30%, and (C) the MR3rd satisfies MR3rd=100%-MR1st-MR2nd.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to Ground granulated blast furnace slag Water-curable hardened body with Manufacturing method This is regarding. [Background technology]

[0002] In recent years, greenhouse gas reduction targets have been set in the industrial sector, and reducing CO2 emissions has become an urgent task in the construction industry as well. Portland cement, the raw material of concrete, emits a large amount of CO2 during production, so concrete is inevitably considered to be a product that emits a large amount of CO2. In contrast, concrete manufactured using industrial by-products such as ground granulated blast furnace slag and fly ash as binders is known as low-carbon concrete, which emits less CO2. Blast-furnace cement, which contains ground granulated blast furnace slag as a binder, is classified into three types: Type A, Type B, and Type C, depending on the mixing ratio of industrial by-products and Portland cement, and is used according to the application. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6084431

[0004] Patent Document 1 proposes a hydraulic hardened body that uses concrete sludge fine powder, which is a powder containing cement recovered from unused concrete such as residual concrete and returned concrete, as a binder in addition to industrial by-products. The concrete sludge fine powder is produced as follows. That is, water is added to unused concrete to make a slurry, gravel and sand are removed from the slurry, and fine sand is removed by a wet cyclone to obtain sludge water. Next, the sludge water is dehydrated to obtain a dehydrated cake, which is placed in a rotating drum and crushed and dried simultaneously while supplying high-temperature air. Since crushing and drying are performed simultaneously, the progress of the hydration reaction is suppressed, and a powder with a high proportion of unhydrated cement, that is, concrete sludge fine powder, is obtained. The hydraulic hardened body described in Patent Document 1 is formulated with a larger amount of concrete sludge fine powder than industrial by-products, thereby suppressing CO2 emissions. Summary of the Invention [Problem to be solved by the invention]

[0005] Hydraulic hardened bodies made from blast-furnace cement, which uses industrial by-products as a binder, are excellent because they have high strength and reduce CO2 emissions. In particular, blast-furnace cement type C uses a high proportion of industrial by-products and is highly effective at reducing CO2 emissions. However, hydraulic hardened bodies made from blast-furnace cement still have issues to be resolved. Specifically, there is the issue of a large amount of water seeping out during pouring, i.e., the amount of bleeding. The higher the proportion of industrial by-products, the greater the amount of bleeding tends to be. The Architectural Institute of Japan has set the upper limit for bleeding at 0.3 cm. 3 / cm 2 However, since bleeding can cause a decrease in the bond strength between the concrete and the reinforcing bars, it is desirable to keep the amount of bleeding as small as possible.

[0006] Although the amount of bleeding of the hydraulic hardened body described in Patent Document 1 is unknown, it is a hydraulic hardened body that can ensure durability against carbonation while ensuring the necessary strength. It is configured to mix as much fine concrete sludge powder, which contains a large amount of unhydrated cement and has carbonation resistance, as possible, and the ratio of industrial by-products mixed is smaller than that of fine concrete sludge powder. The hydraulic hardened body described in Patent Document 1 is thus excellent in terms of strength and carbonation resistance, but some concerns are also seen. Specifically, it is unclear whether it can be used for applications that require particularly high strength. The hydraulic hardened body described in Patent Document 1 also achieves a strength of 21 N / mm, which is the design standard strength. 2 or 24N / mm 2 In other words, it can be used without problems for general purposes. However, since it uses a larger amount of fine concrete sludge powder, which has a smaller proportion of unhydrated cement than Portland cement, than industrial by-products, it is difficult to use it when high strength is required.

[0007] The present invention relates to Ground granulated blast furnace slag This water-curable hardened body uses as the main binder, which is highly effective in reducing CO2 emissions and has a sufficiently high strength, but also has a small amount of bleeding. Manufacturing method The purpose is to provide. [Means for solving the problem]

[0008] The present invention relates to Ground granulated blast furnace slag and concrete sludge fine powder, if necessary. do A binder containing Portland cement, aggregate, and optionally an additive. do Mixing with admixture and mixing water do Water-curable hardening material Manufacturing methodThe concrete sludge fine powder is produced by the following steps: a slurrying process in which water is added to unused concrete consisting of residual concrete or returned concrete to make a slurry; a separation process in which gravel and sand are separated and removed from the slurry to obtain sludge water; a fine sand removal process in which fine sand is separated and removed from the sludge water using a wet cyclone to obtain concentrated sludge water; a dewatering process in which the concentrated sludge water is dewatered to obtain sludge cake; and a crushing and drying process in which the sludge cake is placed in a rotating drum, hot air is supplied to crush and dry the sludge cake to obtain concrete sludge fine powder. The binder in the present invention is composed of industrial by-products in a first mass ratio MR1st, concrete sludge fine powder in a second mass ratio MR2nd, and Portland cement in a third mass ratio MR3rd. The first mass ratio MR1st is selected from the range of the following formula: do . 40% ≦ MR1st ≦ 70% The second mass ratio MR2nd is a ratio in which the specific surface area of ​​the concrete sludge fine powder is 8000 cm 2 When the value is less than / g, select the value so that the following formula is satisfied. death , 10% ≦ MR2nd ≦ 40% and MR2nd ≦ 100% - MR1st and MR2nd ≦ MR1st The specific surface area of ​​the concrete sludge powder is 8000 cm 2 / g greater than 10000cm 2 / g or less, select from the following range: do . 5% ≦ MR2nd ≦ 30% The third mass fraction MR3rd is determined by the following formula: do . MR3rd = 100% - MR1st - MR2nd When a hydraulic hardened body of standard composition is obtained by mixing and kneading a first mass ratio MR1st of ground granulated blast furnace slag as a binder and a mass ratio of Portland cement at 100% - MR1st, the compressive strength of the hydraulic hardened body at 28 days is 90% or more of the compressive strength of the hydraulic hardened body of standard composition at 28 days, and the amount of bleeding occurring during the hardening process of the hydraulic hardened body is 0.5 times or less and is 0.3 cm 3 / cm 2 Configure it as follows: Effect of the Invention

[0009] Water-curable hardened product according to the present invention Manufacturing methodIt has a high effect on reducing CO2 emissions, has high strength, and reduces bleeding. It is possible to obtain a water-curable hardened product with small . [Brief description of the drawings]

[0010] [Figure 1] 2 is a flowchart showing a method for producing a concrete sludge fine powder according to the present embodiment. [Diagram 2] This graph shows the range of the mass proportion of the binder for the water-curable hardened body of this embodiment, and also shows the range of the mass proportion of the blast furnace slag fine powder and the mass proportion of the concrete sludge fine powder when using a concrete sludge fine powder with a specific surface area of ​​8000 cm2 / g or less. [Diagram 3] This graph shows the range of the mass proportion of the binder for the water-curable hardened body of this embodiment, and also shows the range of the mass proportion of the blast furnace slag fine powder and the mass proportion of the concrete sludge fine powder when using a concrete sludge fine powder having a specific surface area of ​​more than 8000 cm2 / g and not more than 10000 cm2 / g. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present embodiment will be described. The hydraulic hardened body according to the present invention uses industrial by-products and fine powder of concrete sludge as binders. First, the fine powder of concrete sludge will be described.

[0012] <Fine concrete sludge powder> Concrete is produced by mixing Portland cement, aggregates such as gravel and sand, water, and admixtures in a forced mixing mixer. The concrete produced in this way is transported to a construction site and poured, but there are cases where some of it remains unused or fails the acceptance inspection. Such concrete is returned to a ready-mixed concrete plant as leftover concrete or returned concrete, or sent to other processing facilities. In other words, it is unused concrete. The concrete sludge fine powder used in the hydraulic hardened body according to this embodiment is produced by processing such unused concrete.

[0013] In the method for producing fine concrete sludge powder, a slurrying step S1 is first carried out as shown in Fig. 1. That is, water is added to virgin concrete to make a slurry. This allows the cement content to be sufficiently dissolved in the added water. The slurry may contain washing wastewater from washing the mixer of a truck agitator or washing wastewater from a ready-mixed concrete plant.

[0014] Next, the aggregate separation step S2 is carried out. This is a step in which solids such as aggregates are removed from the slurry obtained in the slurry formation step S1. This is carried out using multiple vibrating sieves with different mesh sizes, and the slurry is sequentially processed to separate aggregates such as gravel and sand. The collected aggregates are reused. The under-sieve residue remaining after the aggregates are separated becomes sludge water that contains a large amount of cement.

[0015] Following the aggregate separation step S2, a fine sand removal step S3 is carried out. In this embodiment, this step is carried out using a wet cyclone to remove fine sand, i.e., fine sand, from the sludge water. In other words, concentrated sludge water is obtained. The concentrated sludge water obtained in this step is treated in the next dewatering step S4. However, if the concentrated sludge water contains a low amount of cement, it may be sent to the slurrying step S1 and reused as water for slurrying other unused concrete. In this way, the cement content of the sludge water is concentrated.

[0016] The concentrated sludge water is subjected to a dewatering step S4. That is, the concentrated sludge water is treated by a filter press to obtain a sludge cake. At this time, supernatant water is also obtained, which can be reused as concrete mixing water. Finally, the sludge cake is subjected to a crushing and drying step S5. Any device may be used in this step as long as it crushes and dries the sludge cake. However, in this embodiment, a specific rotating drum that can efficiently crush and dry the sludge cake is used. The rotating drum is provided with a crushing and stirring blade that rotates at high speed inside, and hot air is supplied. The sludge cake is placed in the rotating drum, rotated, and hot air is supplied. Then, the sludge cake is crushed by the crushing and stirring blade, and dried by the hot air to obtain a concrete sludge fine powder.

[0017] <Consideration of the mixing ratio of water-curable hardening material> The inventors have found that replacing part of Portland cement with fine concrete sludge powder as a binder has the effect of reducing the amount of bleeding in a water-curable hardened body. The inventors have found that the effect of reducing the amount of bleeding varies depending on the quality of the fine concrete sludge powder, that is, the specific surface area measured by the Blaine method, and that the larger the specific surface area, the greater the effect of reducing the amount of bleeding. The inventors have presumed that the reason why the fine concrete sludge powder has such an effect is as follows. In other words, in the fine concrete sludge powder, unhydrated cement and hydration products are mixed, but the hydration products are attached to the unhydrated cement particles as coarse aggregates in the form of a film. Since they are coarse aggregates, the higher the ratio of the hydration products, the larger the specific surface area. If the specific surface area is large, the area in contact with water becomes large, and it is inevitably easy to absorb moisture. Therefore, it has been presumed that the fine concrete sludge powder with a large specific surface area has a high effect of absorbing moisture immediately after mixing and reducing the amount of bleeding.

[0018] As mentioned above, hydraulic hardened bodies made of blast furnace cement, that is, hydraulic hardened bodies using industrial by-products as binders, have the advantages of being strong and having a high effect of suppressing CO2 emissions, but also have the disadvantage of a slightly large amount of bleeding. Therefore, the present inventors have considered how to solve the disadvantages without compromising the advantages by replacing part of the Portland cement mixed in a certain ratio in blast furnace cement with fine concrete sludge powder. In other words, it is a hydraulic hardened body that has high strength, a high effect of suppressing CO2 emissions, and a small amount of bleeding. They decided to conduct experiments to determine the appropriate mixing ratio of binders to obtain such a hydraulic hardened body. EXAMPLES

[0019] Test 1: The powdered granulated blast furnace slag, an industrial by-product, and ordinary Portland cement were used, and the specific surface area measured by the Blaine method was 8000 cm 2 The concrete sludge fine powder with a specific surface area of ​​7910 cm2 or less was used, and various compositions were prepared by kneading these with aggregates and water to obtain various hydraulic hardened bodies. The bleeding amount of these hydraulic hardened bodies was measured, and the compressive strength at 28 days was also measured. The results are summarized in Table 1 below. In the experiment, the specific surface area of ​​the concrete sludge fine powder was 7910 cm2. 2 / g was used.

[0020] [Table 1]

[0021] In Table 1, the hydraulic hardened bodies I-01 to I-05 have a mixing ratio of ground granulated blast furnace slag in the binder, i.e., a mass ratio of 70%, which is the upper limit of the mass ratio of industrial by-products in blast furnace cement type C. Similarly, the hydraulic hardened bodies I-06 to I-10 have a mass ratio of ground granulated blast furnace slag in the binder of 60%, which is the upper limit of the mass ratio of industrial by-products in blast furnace cement type B. And the hydraulic hardened bodies I-11 to I-15 have a mass ratio of ground granulated blast furnace slag in the binder of 40%, which is the mass ratio of industrial by-products in blast furnace cement type B, which is relatively frequently used. The hydraulic hardened bodies I-01, I-06, and I-11 all have a mass ratio of 0% concrete sludge powder. In other words, they are hydraulic hardened bodies using conventional blast furnace cement types C and B, whose binders consist only of ground granulated blast furnace slag and ordinary Portland cement. Therefore, these hydraulic hardened bodies I-01, I-06, and I-11 are referred to as hydraulic hardened bodies having the standard mix in this specification. Hydraulic hardened bodies I-02 to I-05 are hydraulic hardened bodies I-01 having the standard mix, with part of the normal Portland cement replaced with fine concrete sludge powder. Similarly, hydraulic hardened bodies I-07 to I-10 are hydraulic hardened bodies I-06 having the standard mix, with part of the normal Portland cement replaced with fine concrete sludge powder, and hydraulic hardened bodies I-12 to I-15 are hydraulic hardened bodies I-11 having the standard mix, with part of the normal Portland cement replaced with fine concrete sludge powder.

[0022] The inventors have defined the conditions required for the hydraulic hardened body of the present invention as follows. First, the first condition is that high strength can be obtained, and the compressive strength of the hydraulic hardened body at 28 days of age must be 0.9 times or more the compressive strength of a hydraulic hardened body of standard mix with the same mass ratio of industrial by-products. In other words, the condition is that the hydraulic hardened body must have substantially the same strength as a hydraulic hardened body of standard mix. Next, the condition is that the bleeding amount of the hydraulic hardened body must be 0.5 times or less the bleeding amount of a hydraulic hardened body of standard mix with the same mass ratio of industrial by-products. With this condition, as can be seen from Table 1, the upper limit of the bleeding amount of 0.3 cm stipulated by the Architectural Institute of Japan is 0.5 times or less. 3 / cm 2 The conditions are stricter. This can surely eliminate the drawbacks of hydraulic hardened bodies kneaded from conventional blast furnace cement. Based on these conditions, the hydraulic hardened bodies I-02, ... were judged for the amount of bleeding and the compressive strength at 28 days, and the results are summarized in Table 1. Similarly, the results of whether or not the conditions for the amount of bleeding and the compressive strength at 28 days were met are summarized in Table 1 as an overall judgment. In the graph of FIG. 2, hydraulic hardened bodies I-03, ... that passed the overall judgment and hydraulic hardened bodies I-02, ... that failed are plotted. The area surrounded by the dotted line in the graph indicates the range of the mass ratio of the binder in the hydraulic hardened body according to the present invention. EXAMPLES

[0023] Test 2: The powdered granulated blast furnace slag, an industrial by-product, and ordinary Portland cement were used, and the specific surface area measured by the Blaine method was 8000 cm 2 / g greater than 10000cm 2 The concrete sludge fine powder with a specific surface area of ​​10150 m2 or less was used, and various compositions were prepared by kneading these with aggregates and water to obtain various hydraulic hardened bodies. The bleeding amount and compressive strength at 28 days of age of these hydraulic hardened bodies were measured. The results are summarized in Table 2 below. In the experiment, the specific surface area of ​​the concrete sludge fine powder was 10150 m2.2 / g was used.

[0024] [Table 2]

[0025] In Table 2, the hydraulic hardening bodies II-01 to II-05 have a mass ratio of 70% granulated blast furnace slag powder in the binder, the hydraulic hardening bodies II-06 to II-10 have a mass ratio of 60% granulated blast furnace slag powder in the binder, and the hydraulic hardening bodies II-11 to II-15 have a mass ratio of 40% granulated blast furnace slag powder in the binder. Hydraulic hardening bodies II-01, II-06, and II-11 all have a mass ratio of 0% concrete sludge powder, and are hydraulic hardening bodies made of the standard mix. Hydraulic hardened bodies II-02 to II-05 are the same as hydraulic hardened body II-01, which has a standard mix ratio, but in which part of the ordinary Portland cement has been replaced with fine concrete sludge powder. Hydraulic hardened bodies II-07 to II-10 are the same as hydraulic hardened body II-06, which has a standard mix ratio, but in which part of the ordinary Portland cement has been replaced with fine concrete sludge powder. Hydraulic hardened bodies II-12 to II-15 are the same as hydraulic hardened body II-11, which has a standard mix ratio, but in which part of the ordinary Portland cement has been replaced with fine concrete sludge powder.

[0026] The pass / fail judgment was made based on the same conditions as those in Experiment 1. That is, the compressive strength of the hydraulic hardened body at 28 days was 0.9 times or more the compressive strength of the hydraulic hardened body of the standard mix with the same mass ratio of the industrial by-product, and the bleeding amount of the hydraulic hardened body was 0.5 times or less the bleeding amount of the hydraulic hardened body of the standard mix with the same mass ratio of the industrial by-product. Table 2 summarizes the pass / fail judgment and the overall judgment for these two conditions. In the graph of FIG. 3, the hydraulic hardened body II-02, ..., and the hydraulic hardened bodies II-10 and II-15, which passed the overall judgment, are plotted. In the graph, the area surrounded by the dotted line indicates the range of the mass ratio of the binder in the hydraulic hardened body according to the present invention.

[0027] From the overall judgment of Experiment 1 and Experiment 2, the mixing ratio of the binder in the water-setting hardened body according to the present invention, that is, the mass ratio, was determined as follows. The binder is composed of industrial by-products in a first mass proportion MR1st, concrete sludge fine powder in a second mass proportion MR2nd, and Portland cement in a third mass proportion MR3rd. (A) The first mass ratio MR1st is selected from the range of the following formula. 40% ≦ MR1st ≦ 70% (B) The second mass ratio MR2nd is a ratio in which the specific surface area of ​​the concrete sludge fine powder is 8000 cm 2 When the value is less than 1 / g, the value should be selected so as to satisfy the following formula. 10% ≦ MR2nd ≦ 40% and MR2nd ≦ 100% - MR1st and MR2nd ≦ MR1st The specific surface area of ​​the concrete sludge powder is 8000 cm 2 / g greater than 10000cm 2 When the content is less than 1 / g, select from the range of the following formula. 5% ≦ MR2nd ≦ 30% (C) The third mass fraction MR3rd is expressed by the following formula: MR3rd = 100% - MR1st - MR2nd is determined.

[0028] The hydraulic hardened body according to the present invention also aims to reduce CO2 emissions. Portland cement emits a large amount of CO2, while industrial by-products and concrete sludge fine powder reduce emissions. Therefore, reducing the mass ratio of Portland cement as a binder leads to reduced CO2 emissions. Therefore, the following condition may be added to the mass ratio of the binder in the hydraulic hardened body according to the present invention. MR1st + MR2nd > MR3rd EXAMPLES

[0029] Test 3: In both Experiment 1 and Experiment 2, the water-binder ratio was limited to 60%. The amount of bleeding should be smaller if less water is mixed, but even when the water-binder ratio is less than 60%, such as 40% or 50%, an experiment was conducted to confirm that the amount of bleeding is small for the water-setting hardened body kneaded with the mass ratio of binder determined above. At the same time, it was decided to confirm that the condition for compressive strength at 28 days was met. In experiment 3, blast furnace slag powder, an industrial by-product, ordinary Portland cement, and a concrete mixture with a specific surface area of ​​7910 cm2 measured by the Blaine method were used. 2 The water-to-binder ratio was 40%, 50%, and 60% to obtain hydraulic hardened bodies, and the bleeding amount and compressive strength at 28 days were measured. The results are shown in Table 3.

[0030] [Table 3]

[0031] As is clear from Table 3, even for water-curable hardened bodies with a water-binder ratio of less than 60%, the bleeding amount and 28-day compressive strength were both within the specified ratio range compared to the water-curable hardened body of the standard mix, which was the condition set by the inventors, and it was confirmed that the conditions were met.

Claims

1. A method for producing a hydraulic hardened body by kneading a binder consisting of only ground granulated blast furnace slag, ground granulated concrete sludge, and Portland cement which is mixed as required, aggregate, an admixture which is added as required, and mixing water, comprising: The concrete sludge fine powder is produced by a slurrying process in which water is added to unused concrete, which is made of residual concrete or returned concrete, to produce a slurry; a separation step of separating and removing gravel and sand from the slurry to obtain sludge water; a fine sand removal step of separating and removing fine sand from the sludge water using a wet cyclone to obtain concentrated sludge water; a dewatering step of dewatering the concentrated sludge water to obtain a sludge cake; A crushing and drying process in which the sludge cake is placed in a rotating drum and hot air is supplied thereto to crush and dry the sludge cake to obtain a concrete sludge fine powder. The binder is a mixture of the ground granulated blast furnace slag in a first mass ratio MR1st, the ground granulated concrete sludge in a second mass ratio MR2nd, and Portland cement in a third mass ratio MR3rd, (A) The first mass ratio MR1st is selected from the range of the following formula, 40% ≦ MR1st ≦ 70% (B) The second mass ratio MR2nd is set to a value in which the specific surface area of ​​the concrete sludge fine powder is 8000 cm 2 When the value is less than / g, the following formula should be satisfied: 10% ≦ MR2nd ≦ 40% and MR2nd ≦ 100% - MR1st and MR2nd ≦ MR1st The specific surface area of ​​the concrete sludge fine powder is 8000 cm 2 / g greater than 10000cm 2 When the value is less than / g, select from the range of the following formula: 5% ≦ MR2nd ≦ 30% (C) The third mass ratio MR3rd is calculated by the following formula: MR3rd = 100% - MR1st - MR2nd The decision should be made as follows: When the ground granulated blast furnace slag is used as a binder in the first mass ratio MR1st and the mass ratio of Portland cement is 100% - MR1st, the mixture is kneaded to obtain a hydraulic hardened body of standard composition, The compressive strength of the water-cured hardened body at 28 days is 90% or more of the compressive strength of the water-cured hardened body at 28 days of the standard blend, and the amount of bleeding occurring during the curing process of the water-curable cured body is 0.5 times or less the amount of bleeding occurring during the curing process of the water-curable cured body of the standard formulation and is 0.3 cm3 / cm2 or less.

2. The method for producing a water-setting hardened body according to claim 1 , wherein a water-binder ratio, which is a ratio of the kneading water to the binder, is set to 60% or less.

3. The first mass ratio MR1st, the second mass ratio MR2nd, and the third mass ratio MR3rd are expressed by the following formula: MR1st + MR2nd > MR3rd The method for producing a hydraulically cured product according to claim 1 or 2, wherein the above formula (1) is selected so as to satisfy the above formula (1).

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