Formwork for manufacturing CO2-absorbing concrete, and method for manufacturing CO2-absorbing concrete using this formwork.

Abstract

This invention provides a formwork that can produce CO2-absorbing concrete in a shorter time by preventing dripping during the placement of concrete fluidized material while supplying sufficient CO2, and a method for producing CO2-absorbing concrete using this formwork. [Solution] The perforated formwork 1 used in the production of CO2-absorbing concrete of the present invention comprises a perforated formwork material 2 into which a plurality of introduction holes 3 for introducing CO2 are formed and into which ready-mixed concrete FC having a predetermined composition for absorbing CO2 is poured, and a breathable sheet 4 that is attached to cover the inner surface of the perforated formwork material 2 and has breathability that allows CO2 to pass through. The ready-mixed concrete FC poured into the perforated formwork material 2 reacts with the CO2 that has passed through the plurality of introduction holes 3 and the breathable sheet 4, thereby carbonizing and hardening.

Description

Technical Field

[0001] The present invention relates to a formwork for manufacturing CO2-absorbing concrete in which carbon dioxide (CO2) is absorbed and immobilized, and a manufacturing method for manufacturing CO2-absorbing concrete using this formwork.

Background Art

[0002] Ordinary concrete mainly consists of water, cement, and aggregates, and hardens through a chemical reaction between water and cement, so cement is essential. Further, cement mainly uses limestone (CaCO3), and by adding clay, iron, etc. and firing, calcium oxide compounds (CaO) and carbon dioxide (CO2) that become the main components are generated. As a result, a large amount of CO2 is released into the atmosphere. As is well known, CO2 has become a global problem as having a great impact on global warming, and countermeasures against it are urgent issues.

[0003] For this reason, the following multiple technologies related to concrete and for reducing CO2 have been proposed. A. Technology for replacing part of the cement in concrete with industrial by-products, etc. B. Technology for mixing materials in which CO2 is immobilized into aggregates or powders into concrete C. Technology for absorbing and immobilizing CO2 in concrete Although Technology A can reduce the amount of cement used and CO2 emissions, it is impossible to achieve "carbon negative" where CO2 emissions are zero or less. Although Technology B has the possibility of achieving carbon negative, it only indirectly absorbs CO2 into aggregates, etc.

[0004] In contrast to these, Technology C directly absorbs CO2 into the concrete, and has the potential to achieve carbon negativity. A known method for manufacturing concrete based on Technology C (hereinafter referred to as "CO2-absorbing concrete") is disclosed in, for example, Patent Document 1. In this manufacturing method, a special formwork is used. This formwork is a rectangular parallelepiped with an open top, and a hydraulic fluid is poured from above. This hydraulic fluid is a concrete fluid containing a carbonate component, etc. Numerous gas inlet holes are formed in the four peripheral walls of the formwork, penetrating them to introduce CO2 into the formwork.

[0005] To produce CO2-absorbing concrete using this formwork, after pouring the fluidized concrete into the formwork, CO2 is introduced into the formwork through a gas inlet hole and exposed (contacted) to the fluidized concrete. As a result, the fluidized concrete carbonates and hardens, producing CO2-absorbing concrete. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-32401 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the conventional formwork described above, the gas inlet holes penetrate the surrounding wall and communicate with the inside and outside of the formwork. As a result, while CO2 is introduced through the gas inlet holes, there is a risk that the concrete fluidizer may leak out (drift) during or immediately after placement. To prevent such dripping, one could consider limiting the dimensions or opening ratio of the gas inlet holes. However, in that case, it would not be possible to supply enough CO2 into the formwork, and as a result, sufficient concrete strength due to carbonation and hardening cannot be obtained in a short time, which would require more time to demold and reduce productivity.

[0008] The present invention was made to solve the above-mentioned problems, and aims to provide a formwork for producing CO2-absorbing concrete that can supply sufficient CO2 while preventing dripping during the placement of the concrete fluid, thereby promoting the carbonation and hardening of the concrete fluid, and enabling the production of CO2-absorbing concrete in a shorter time, and a method for producing CO2-absorbing concrete using such a formwork. [Means for solving the problem]

[0009] To achieve this objective, the invention according to claim 1 is a formwork used in the production of CO2-absorbing concrete that has absorbed and fixed CO2 (carbon dioxide), comprising: a perforated formwork material having a plurality of introduction holes for introducing CO2 and into which a concrete fluid material having a predetermined composition for absorbing CO2 is poured; and a breathable sheet attached to cover the inner surface of the perforated formwork material and having breathability through which CO2 can pass, characterized in that the concrete fluid material poured into the perforated formwork material carbonizes and hardens by reacting with CO2 that has passed through the plurality of introduction holes and the breathable sheet.

[0010] The formwork for producing CO2-absorbing concrete according to the present invention comprises a perforated formwork material and a ventilation sheet attached to cover the inner surface of the perforated formwork material. The perforated formwork material has multiple introduction holes for introducing CO2, and the ventilation sheet is permeable to allow CO2 to pass through. With this configuration, a concrete fluidized material containing a carbonation component that absorbs CO2 is poured into the formwork. In this state, the poured concrete fluidized material is in contact with the ventilation sheet placed inside the formwork, so dripping (leakage of concrete fluidized material to the outside) during pouring or immediately after pouring can be prevented.

[0011] When the formwork is placed in a CO2 atmosphere after the concrete fluidization material has been poured, the CO2 flows into multiple inlet holes in the perforated formwork material, passes through a ventilation sheet, and is introduced into the formwork. As a result, the concrete fluidization material inside the formwork is exposed to CO2, its carbonation components are carbonated (absorbing CO2), and hardening occurs, producing CO2-absorbing concrete. In this case, since the dripping of the concrete fluidization material during pouring is prevented by the ventilation sheet, it is possible to secure a larger supply of CO2 by setting the dimensions of the inlet holes and the ratio of openings to be larger compared to conventional methods. As a result, the carbonation and hardening of the concrete fluidization material are accelerated from immediately after pouring, and CO2-absorbing concrete can be produced in a shorter time.

[0012] The invention according to claim 2 is characterized in that, in the formwork for manufacturing CO2 absorbing concrete as described in claim 1, the perforated formwork material is made of perforated metal having a number of holes of predetermined dimensions and perforation ratio as introduction holes.

[0013] With this configuration, by constructing the perforated formwork material from punched metal, a large number of holes with predetermined dimensions and perforation ratios can be used as introduction holes, while easily ensuring the strength, rigidity, and durability required for the perforated formwork material.

[0014] The invention according to claim 3 is a formwork for manufacturing CO2-absorbing concrete as described in claim 1, characterized in that the ventilation sheet has a predetermined low water permeability that prevents leakage of the concrete fluid when it is poured into the formwork and allows the discharge of excess water generated when the concrete fluid hardens.

[0015] With this configuration, the breathable sheet has the aforementioned predetermined low water permeability, which prevents leakage (dripping) of the concrete fluid material during and immediately after pouring into the formwork, and allows excess water generated during the hardening of the concrete fluid material to be discharged through the breathable sheet. This accelerates the hardening of the concrete fluid material and further shortens the manufacturing time of the CO2-absorbing concrete.

[0016] To achieve the above objective, the invention according to claim 4 is a method for producing CO2-absorbing concrete using a formwork described in any one of claims 1 to 3, comprising: a concrete fluidized material preparation step of preparing a concrete fluidized material by mixing water, cement, an admixture that reacts with CO2 to produce calcium carbonate, and aggregate in predetermined proportions; a concrete pouring step of pouring the prepared concrete fluidized material into a formwork; a carbonation step of placing the formwork into which the concrete fluidized material has been poured under a CO2 atmosphere, thereby introducing the admixture in the concrete fluidized material through a plurality of introduction holes in the perforated formwork material of the formwork and reacting with CO2 that has passed through a ventilation sheet, thereby carbonizing and hardening the concrete fluidized material; and a demolding step of removing the hardened concrete from the formwork after performing the carbonation step for a predetermined period of time.

[0017] In the method for producing CO2-absorbing concrete of the present invention, CO2-absorbing concrete is produced using the formwork described in any one of claims 1 to 3, as follows: First, a concrete fluid is prepared by mixing water, cement, an admixture that reacts with CO2 to produce calcium carbonate, and aggregate in predetermined proportions (concrete fluid preparation step). Next, the prepared concrete fluid is poured into the formwork (concrete pouring step). As described above, in this state, the poured concrete fluid is in contact with a ventilation sheet placed inside the formwork, so dripping during pouring and immediately after pouring can be prevented.

[0018] Next, place the formwork filled with the concrete fluidizing agent in an atmosphere of CO₂. As a result, after CO₂ flows into the plurality of introduction holes of the perforated formwork material of the formwork, it passes through the ventilation sheet and is introduced into the formwork. Then, the admixture in the concrete fluidizing agent reacts with the introduced CO₂ to carbonize and harden the concrete fluidizing agent (carbonation process). Further, after executing this carbonation process for a predetermined period, a CO₂ absorption concrete is manufactured by taking out the concrete hardened body from the formwork (demolding process).

[0019] As described above, in the formwork of the present invention, since bleeding during the placement of the concrete fluidizing agent is prevented by the ventilation sheet, it is possible to secure a larger CO₂ supply amount by setting the dimensions and aperture ratio of the introduction holes larger compared to the conventional case. Thereby, carbonation and hardening of the concrete fluidizing agent are promoted, and CO₂ absorption concrete can be manufactured in a shorter time.

[0020] The invention according to claim 5 is characterized in that, in the method for manufacturing CO₂ absorption concrete according to claim 4, it further includes a temperature adjustment step of adjusting the CO₂ atmosphere temperature to a predetermined temperature in the carbonation step.

[0021] According to this configuration, in the carbonation step, by adjusting the CO₂ atmosphere temperature to a predetermined temperature suitable for the reaction with the admixture in the concrete, the carbonation of the CO₂ absorption concrete can be further improved.

[0022] The invention according to claim 6 is characterized in that, in the method for manufacturing CO₂ absorption concrete according to claim 4, it further includes a secondary carbonation step of further carbonizing and hardening the concrete hardened body taken out from the formwork by curing it in an atmosphere of CO₂.

[0023] According to this configuration, the concrete hardened body taken out from the mold in the demolding process is further cured in an atmosphere of CO2 in the secondary carbonation process. As a result, the carbonation and hardening of the CO2-absorbing concrete can be further promoted by directly exposing the concrete hardened body to CO2.

Brief Description of the Drawings

[0024] [Figure 1] It is a perspective view showing an example of a perforated formwork for manufacturing CO2-absorbing concrete according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view of the perforated formwork of FIG. 1. [Figure 3] It is a flowchart showing a method of manufacturing CO2-absorbing concrete using a perforated formwork. [Figure 4] It is a table showing the mix of CO2-absorbing concrete used in the test. [Figure 5] It is a table showing the steps of the test of CO2-absorbing concrete. [Figure 6] It is a table showing the compressive strength of CO2-absorbing concrete obtained by a compressive strength test. [Figure 7] It is a diagram showing the relationship between the number of days after placing CO2-absorbing concrete and the compressive strength in the case of a perforated formwork and a normal formwork. [Figure 8] It is a diagram showing the relationship between the number of days after placing and the difference in compressive strength between a perforated formwork and a normal formwork. [Figure 9] It is a table showing the weight of the test piece obtained by weight measurement. [Figure 10] It is a diagram showing the relationship between the number of days after placing and the weight of the test piece in the case of a perforated formwork and a normal formwork. [Figure 11] It is a diagram showing the relationship between the number of days after placing and the change amount of the weight of the test piece in the case of a perforated formwork and a normal formwork. [Figure 12] It is a diagram showing the relationship between the number of days after placing and the difference in the change amount of the weight of the test piece between a perforated formwork and a normal formwork. [Figure 13]This table shows the carbonation depth and carbonation rate for perforated formwork and conventional formwork, obtained by measuring the carbonation depth. [Figure 14] This figure shows the relationship between the number of days after concrete pouring and the carbonation rate for perforated formwork and conventional formwork. [Figure 15] Figure 3 is a flowchart showing a method for producing CO2-absorbing concrete with an added secondary carbonation step. [Modes for carrying out the invention]

[0025] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 shows a perforated formwork, which is an example of a formwork according to an embodiment of the present invention. As shown in Figures 1 and 2, ready-mixed concrete (concrete fluidized material) FC is poured into this perforated formwork 1. The perforated formwork 1 comprises a perforated formwork material 2 having numerous introduction holes 3 for introducing CO2, and a ventilation sheet 4 attached to the inner surface of the perforated formwork material 2.

[0026] The perforated formwork material 2 is assembled into a rectangular parallelepiped by two rectangular front and rear plates 2a, two side plates 2b, and one bottom plate 2c, with the top surface open. These plates 2a to 2c are made of metal such as iron. The front and rear plates 2a and the side plates 2b are made of perforated metal, and the introduction holes 3 are formed by numerous perforations with predetermined hole diameters and opening ratios.

[0027] The ventilation sheet 4 is attached to the inner surfaces of the front and rear plates 2a and side plates 2b of the perforated formwork material 2, excluding the bottom plate 2c, so as to cover them. The ventilation sheet 4 has permeability that allows CO2 to pass through, while having a predetermined degree of low water permeability that makes it difficult for water to pass through. More specifically, this predetermined degree of low water permeability is such that it prevents leakage of the concrete fluid material poured into the perforated formwork 1, while allowing the discharge of excess water generated when the concrete fluid material hardens.

[0028] Next, with reference to Figure 3, a method for manufacturing CO2-absorbing concrete using perforated formwork 1 will be described. First, in step 1 (illustrated as "S1"; the same applies hereafter), perforated formwork 1 is prepared, which includes the perforated formwork material 2 and ventilation sheet 4 with the configuration described above. Note that the perforated formwork 1 shown in Figure 1 is an example, and the actual shape and dimensions of the formwork will be set according to the concrete product to be manufactured.

[0029] Next, in Step 2, ready-mix concrete (fluidized concrete) FC is prepared (fluidized concrete preparation step). Ready-mix concrete FC is concrete that is still soft, made by mixing water, cement, coarse aggregate, fine aggregate, and admixtures in predetermined proportions. The admixture also contains γ-type dicalcium silicate (γ-C2S) as a carbonation component. This γ-C2S reacts with CO2 to produce calcium carbonate, and as it hardens, CO2-absorbing concrete is produced.

[0030] In the next step, step 3, the prepared ready-mix concrete FC is poured into the perforated formwork 1 from above (concrete pouring process). As shown in Figures 1 and 2, in this state after pouring, a ventilation sheet 4 is interposed between the ready-mix concrete FC and the perforated formwork material 2. Therefore, even if the diameter and perforation ratio of the introduction holes 3 are relatively large, dripping of the ready-mix concrete FC from the introduction holes 3 during pouring and immediately afterward can be effectively prevented.

[0031] Next, in step 4, CO2 is introduced into the perforated formwork 1, and the ready-mixed concrete FC inside the perforated formwork 1 is reacted with the CO2 and hardened by carbonation (carbonation process). Specifically, the perforated formwork 1 in which the ready-mixed concrete FC has been poured is placed in a sealed container (not shown), and CO2 is supplied to the sealed container. As this CO2, for example, high-concentration CO2 sealed in a CO2 cylinder can be used. In addition, various exhaust gases such as exhaust gas from thermal power plants, exhaust gas from boilers, and exhaust gas containing CO2 emitted in the manufacturing process of other products can be used.

[0032] CO2 supplied to the sealed container flows into multiple inlet holes 3 of the perforated formwork material 2, then passes through the ventilation sheet 4 and is introduced into the perforated formwork 1. As a result, the ready-mixed concrete FC is exposed to CO2 (cured in a CO2 atmosphere), and its admixtures react with the CO2 (carbonation) and harden, thereby producing a hardened concrete body.

[0033] Furthermore, because the breathable sheet 4 has the aforementioned low water permeability, excess water generated during concrete hardening can be discharged through the breathable sheet 4. This accelerates the hardening of the concrete and further shortens the manufacturing time of the CO2-absorbing concrete.

[0034] Furthermore, the CO2 atmosphere temperature may be adjusted to a predetermined temperature during the carbonation process (temperature adjustment process). This adjustment of the CO2 atmosphere temperature is performed, for example, by installing a temperature sensor that detects the CO2 atmosphere temperature and a heater (neither shown) that heats the inside of the sealed container in a sealed container, and controlling the heater so that the detected CO2 atmosphere temperature becomes a predetermined temperature (target temperature) suitable for the reaction between CO2 and the admixture of the concrete fluidizer. Through this temperature adjustment, the hydration reaction is promoted by heating with the heater, and the carbonation of the CO2 absorbing concrete can be performed well by maintaining the CO2 atmosphere temperature at the predetermined temperature.

[0035] Next, after the carbonation process, for example, when a predetermined period has elapsed since the placement of the ready-mix concrete (FC), the hardened concrete is removed from the perforated formwork 1 (demolition process). This completes the production of the CO2-absorbing concrete.

[0036] Next, referring to Figures 4 to 14, the conditions and results of the tests conducted to confirm the effectiveness of the CO2-absorbing concrete manufacturing method described above will be explained. In this effectiveness confirmation test, multiple test specimens (test pieces) of CO2-absorbing concrete were prepared using the manufacturing method described above, with a perforated formwork equipped with the perforated formwork material and ventilation sheet according to the present invention. As shown in Figure 5, compressive strength tests, weight measurements, and carbonation depth measurements were performed on these test specimens. As a comparative example, test specimens of CO2-absorbing concrete were prepared using a conventional formwork without inlet holes, and the same tests and measurements were performed. The conditions and results of the tests will be explained in detail below.

[0037] • Test conditions A. Concrete material mix As shown in Figure 4, the concrete material is based on the standard mix of ready-mix concrete used at a ready-mix concrete plant (first row of the same figure), and 1 m³ of that ready-mix concrete 3 Of these, the amount of powdered material (usually cement) (375 kg) was replaced with ordinary cement (295 kg) + admixture (γ-C2S) (80 kg) (second row of the same figure). In addition, the amount of ready-mix concrete required to prepare the 18 test specimens was (0.03 m³). 3 The values ​​were converted using the same weight ratio to obtain the desired result (third row of the same figure).

[0038] B. Fabrication of perforated formwork A perforated metal sheet made of iron-stainless steel with a 62.9% perforation ratio was prepared by rolling a 3mm thick iron-stainless steel plate into a cylindrical shape and attaching a bottom to it. This perforated metal sheet conforms to the specifications of JIS A 1132, Method for Preparing Concrete Strength Test Specimens, 5. Test Specimens for Compressive Strength Test, and the dimensions of the test specimens are φ100mm × H200mm. Next, nine perforated formworks were prepared by fitting and attaching a 0.165mm thick breathable sheet, formed into a cylindrical shape with tape, inside the perforated formwork. The breathable sheet allows CO2 to pass through easily while being poorly permeable to water to the extent mentioned above. In addition, nine standard plastic formworks without holes were prepared to create comparative test specimens of the same dimensions.

[0039] C. Preparation of test specimens First, 10 liters of waste concrete, with the coarse aggregate (gravel) and fine aggregate (sand) removed, were poured into a rotating drum, rotated for 90 seconds, and then discarded. Next, 0.03 m³ of concrete, necessary for the preparation of 18 test specimens, was used. 3 Of the 30 liters of materials, the powdered materials (ordinary cement, γ-C2S) were first placed in the rotating drum and mixed for 20 seconds. Then, water and admixtures were added and mixed for another 20 seconds, followed by the addition of coarse and fine aggregates, and the drum was rotated for another 90 seconds. The air content and slump value of the concrete were also measured, and if these values ​​were significantly far from the target values, the mixing process was repeated. The mixed ready-mix concrete was then poured into nine perforated formwork and nine standard formwork.

[0040] D. Curing and Testing As described above, the work items for curing and testing after pouring the concrete and preparing the test specimens are as shown in Figure 5. This point will be explained below. (On the day of concrete pouring) The 18 test specimens prepared as described above were placed in a sealed container, and with the lid closed, CO2 was supplied to the container at a flow rate of, for example, 1 liter / min to begin the CO2 curing process. During this curing process, the inside of the sealed container was heated with a heater, and the temperature, humidity, and CO2 concentration inside the container were measured. The heater was also controlled so that the measured temperature inside the sealed container reached the target temperature.

[0041] (1st day after pouring) One day after concrete placement, the CO2 supply was stopped, and with the sealed container opened, all 18 specimens were removed from the container, capped for compressive strength testing, and then demolded. Next, the weight of each demolded specimen was measured. Of these specimens, three specimens with perforated formwork and three specimens with standard formwork were designated as specimens from day one after placement (first curing) (No. 1-1 to 1-3, No. 2-1 to 2-3), and compressive strength tests were conducted on each of them.

[0042] Furthermore, the carbonation depth was measured for these specimens as follows: First, each specimen was split, and phenolphthalein solution was sprayed onto the split surface. Next, the boundary between the carbonated, lighter-colored area and the uncarbonated, darker-colored area was identified on the split surface, and the distance from the top, bottom, left, and right surfaces of the specimen to the boundary was measured as the carbonation depth (see Figure 13). The carbonation rate (volume fraction) was also calculated from the four measured carbonation depths. The remaining 12 specimens were returned to a sealed container, and the CO2 curing process was resumed under the same conditions as before.

[0043] (2nd day after pouring) Two days after concrete placement, the CO2 supply was stopped, and with the sealed container opened, all 12 specimens were removed from the container and their weights were measured. Of these specimens, three with perforated formwork and three with standard formwork were used as specimens (No. 1-4 to 1-6, No. 2-4 to 2-6) on the second day after placement (second curing), and a compressive strength test was conducted. Furthermore, the carbonation depth was measured for these specimens in the same manner as described above. The remaining six specimens were returned to the sealed container, and CO2 curing was resumed under the same conditions as before.

[0044] (3rd day after pouring) Three days after concrete placement, the CO2 supply was stopped, and with the sealed container opened, all six specimens were removed from the container and their weights were measured. Compression strength tests were then conducted on three of these specimens (No. 1-7 to 1-9, No. 2-7 to 2-9) as specimens from the third day after placement (third curing period). Furthermore, the carbonation depth was measured on these specimens in the same manner as described above, concluding all tests and measurements.

[0045] • Test results A. Compressive strength Figure 6 shows a list of the compressive strengths obtained from the compressive strength test for each test specimen, as well as the average compressive strength for three test specimen groups that have the same formwork and number of days after pouring (= number of curing cycles). Hereafter, the latter average compressive strength will be referred to as "compressive strength SC" in the explanation. Figure 7 is a graph showing the relationship between the number of days after pouring and this compressive strength SC, and Figure 8 is a graph showing the relationship between the number of days after pouring and the difference in compressive strength SC between perforated formwork and normal formwork.

[0046] As shown in Figures 6 and 7, the compressive strength SC on the first day after concrete placement is 13.9 N / mm² when using a standard formwork. 2 In contrast, when using perforated formwork, a larger 16.6 N / mm² is obtained. 2A clear difference was observed. This is thought to be because, as confirmed in the measurement results of the carbonation depth described later, in the case of normal formwork, CO2 is supplied only from the top surface of the test specimen during the first day after placement, whereas in the case of perforated formwork, CO2 is supplied from the sides as well as the top surface of the test specimen, thereby promoting the carbonation (absorption of CO2) of the concrete and the resulting hardening.

[0047] Furthermore, in the case of standard formwork, the compressive strength SC is 13.9 → 22.0 → 27.4 N / mm² for 1 day → 2 days → 3 days after pouring. 2 This trend continues. In contrast, for perforated formwork, the compressive strength SC over the same period is 16.6 → 23.8 → 30.2 N / mm². 2 The results showed that, compared to the case of conventional formwork, generally greater compressive strength was obtained, and it was confirmed that the difference between the two remained almost constant (did not shrink) (see Figures 7 and 8). This is thought to be because, in both the case of perforated formwork and conventional formwork, demolding was performed on the first day after pouring, and thereafter CO2 was supplied similarly from the top and sides of the test specimen, resulting in the carbonation and hardening of the concrete proceeding at a similar rate.

[0048] As described above, by pouring concrete into perforated formwork and curing it with CO2, the carbonation and hardening of the concrete can be accelerated immediately after pouring, increasing the strength of the concrete, and thereby enabling the production of CO2-absorbing concrete in a shorter time.

[0049] B. Weight Figure 9 shows a list of the weights of each test specimen obtained by weight measurement, and the average weight for each group of test specimens with the same formwork and number of days after pouring (= number of curing cycles). Hereafter, the latter average weight will be referred to as the "test specimen weight" for each test specimen group, and the explanation will proceed accordingly. Figure 10 is a graph showing the relationship between the number of days after pouring and this test specimen weight, Figure 11 is a graph showing the relationship between the number of days after pouring and the change in test specimen weight for perforated formwork and normal formwork, based on the time of capping, and Figure 12 is a graph showing the relationship between the number of days after pouring and the difference in the change in test specimen weight shown in Figure 11 between perforated formwork and normal formwork.

[0050] As shown in these figures, in the case of perforated formwork, the weight of the test specimen remains almost constant or increases slightly from 1 to 3 days after casting, suggesting that the specimen absorbs CO2 to a similar extent as the decrease in moisture content due to heating. In contrast, in the case of conventional formwork, the weight of the test specimen clearly decreases from 1 to 3 days after casting, which suggests that CO2 absorption is slower compared to the case of perforated formwork.

[0051] C. Carbonation depth Figure 13 shows a list of the carbonation depth and carbonation rate for each test specimen obtained by carbonation depth measurement, as well as the average carbonation rate for each test specimen group with the same formwork and number of days after pouring (= number of curing cycles). Hereafter, the average value of the carbonation rate will be used as the "carbonation rate" for each test specimen group in the explanation. Figure 14 is a graph showing the relationship between the number of days after pouring and this carbonation rate.

[0052] As shown in Figure 13, the carbonation depth from the left and right sides on the first day after placement was 0 for the case of the standard formwork, while it was 10 mm on each side for the case of the effective formwork, showing a clear difference. Furthermore, the carbonation rate from day 1 to day 2 to day 3 after placement was 2.5% → 23.5% → 40.6% for the case of the standard formwork. In contrast, for the case of the effective formwork, it progressed from 37.5% → 53.9% → 55.1%, showing a particularly large difference on the first day after placement compared to the case of the standard formwork, and a generally higher carbonation rate was obtained. This is thought to be because, during the first day after placement, with the case of the standard formwork, CO2 is supplied only from the top surface of the test specimen, whereas with the case of the perforated formwork, CO2 is supplied from the sides as well as the top surface of the test specimen, thereby promoting the carbonation of the concrete and the resulting hardening.

[0053] Based on the results of the above effectiveness verification tests, the effect of the present invention, which is that by using the effective formwork of the present invention to pour concrete containing carbonation components and curing it in a CO2 atmosphere, the carbonation and hardening of CO2-absorbing concrete is promoted, and its production can be carried out in a shorter time, has been clearly verified.

[0054] It should be noted that the present invention is not limited to the embodiments described and can be implemented in various forms. For example, the perforated formwork 1 shown in Figure 1 is merely an example, and the actual shape and dimensions of the formwork will of course be set according to the concrete product to be manufactured. Furthermore, the number, size, shape, and perforation ratio of the introduction holes 3 formed in the effective formwork material 2 are not limited to those shown in the embodiments, and appropriate ones can be arbitrarily adopted according to the mix of the ready-mixed concrete FC to be poured and the size of the perforated formwork 1. In addition, although the effective formwork material 2 is made of perforated metal with many holes formed in it in the embodiments, it is not limited to this, and may be made of multiple wires or elongated plates assembled in a grid pattern. In this case, if the rigidity of the effective formwork material is insufficient, stiffening materials may be installed.

[0055] Furthermore, the concrete mix shown in Figure 4 is merely an example, and any mix suitable for the present invention can be adopted. In addition, although the manufacturing method in Figure 3 is described as performing concrete demolding after a predetermined period has elapsed since placement, it is not limited to this, and may be performed, for example, when it is estimated that the required compressive strength has been achieved.

[0056] Furthermore, in the manufacturing method shown in Figure 3, the manufacturing process is completed by demolding after the carbonation step. However, as shown in Figure 15, a secondary carbonation step (step 6) may be performed after the demolding step, in which the hardened concrete is cured in a CO2 atmosphere. This can further accelerate the carbonation and hardening of the CO2-absorbing concrete. In addition, the details of the configuration can be appropriately modified within the scope of the spirit of the present invention. [Explanation of Symbols]

[0057] 1. Perforated formwork (formwork) 2 Perforated formwork material 3. Inlet holes 4. Breathable sheet FC ready-mixed concrete (concrete fluidized material)

Claims

1. CO ２ CO2 absorbed and fixed ２ A formwork used in the manufacture of absorbent concrete, CO ２ Multiple introduction holes are formed for introducing CO ２ A perforated formwork material on which a concrete fluidized material containing a carbonation component that absorbs carbonation is poured, It is attached so as to cover the inner surface of the perforated formwork material, CO ２ It comprises a breathable sheet that allows air to pass through, The concrete fluidized material poured into the perforated formwork material passes through the plurality of introduction holes in the perforated formwork material and through the ventilation sheet, and CO2 ２ CO is characterized by carbonation and hardening through a reaction with [another substance]. ２ Formwork for manufacturing absorbent concrete.

2. The perforated formwork material is made of perforated metal having a number of holes having predetermined dimensions and opening ratios as introduction holes, as described in claim 1. ２ Formwork for manufacturing absorbent concrete.

3. The ventilation sheet has a predetermined water impermeability that prevents leakage of the fluidized concrete during placement in the formwork and allows discharge of excess water generated during curing of the fluidized concrete, and is the CO according to claim 1, characterized in that ２ A formwork for manufacturing absorption concrete.

4. Using the formwork described in any one of claims 1 to 3, CO ２ A manufacturing method for producing absorbent concrete, Water, cement, CO2 ２ A concrete fluidization preparation step involves preparing the concrete fluidization by mixing an admixture that reacts with an aggregate to produce calcium carbonate and aggregate in a predetermined ratio, A concrete pouring step in which the prepared concrete fluid material is poured into the formwork, The formwork on which the aforementioned fluidized concrete was poured was then CO ２ By placing it in such an atmosphere, the admixture in the concrete fluidizer is introduced through the multiple introduction holes in the perforated formwork material of the formwork, and CO2 passes through the ventilation sheet. ２ A carbonation step in which the concrete fluid material is carbonated and hardened by reacting with, After performing the carbonation process for a predetermined period, a demolding process is performed to remove the hardened concrete from the formwork. CO characterized by having ２ A method for manufacturing absorbent concrete.

5. In the carbonation process, CO ２ The CO2 CO2 according to claim 4, further comprising a temperature adjustment step for adjusting the ambient temperature to a predetermined temperature. ２ A method for manufacturing absorbent concrete.

6. In the carbonation process, the hardened concrete removed from the formwork is CO ２ The CO2 compound according to claim 4, further comprising a secondary carbonation step of further carbonation and hardening by curing in an atmosphere. ２ A method for manufacturing absorbent concrete.

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