Method for measuring the amount of carbon dioxide fixed in concrete, and apparatus for measuring the amount of carbon dioxide fixed in concrete

Abstract

To provide a method for measuring the amount of carbon dioxide fixed by concrete that can easily and quickly measure the amount of carbon dioxide fixed by concrete. [Solution] A method for measuring the amount of carbon dioxide fixed by concrete, comprising: a pre-carbonation weight measurement step of measuring the weight of a concrete specimen; a carbonization curing step of placing the specimen in a sealed container and passing carbon dioxide through the sealed container; a post-carbonation weight measurement step of measuring the weight inside the sealed container after passing carbon dioxide; and a step of determining the amount of carbon dioxide fixed by the specimen based on the difference between the weight measured in the post-carbonation weight measurement step and the weight measured in the pre-carbonation weight measurement step.

Description

Technical Field

[0001] The present invention relates to a method for measuring the amount of carbon dioxide fixed in concrete and a measuring apparatus therefor.

Background Art

[0002] Towards the realization of a carbon-neutral society, carbon dioxide fixation technology has also attracted attention in the concrete field. For example, Patent Document 1 discloses a carbonation curing facility for absorbing carbon dioxide in concrete.

[0003] Conventionally, as methods for measuring the amount of carbon dioxide fixed in concrete, generally, the TOC (TOC: Total Organic Carbon) method and the TG (thermogravimetric measurement)-DTA (differential thermal analysis) method are known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conventional methods for measuring the amount of carbon dioxide fixed in concrete have problems such as the high cost of the measuring apparatus and the time and cost required for measurement when the measurement is entrusted to a measuring institution.

[0006] Therefore, an object of the present invention is to provide a method for measuring the amount of carbon dioxide fixed in concrete and a measuring apparatus therefor that can measure the amount of carbon dioxide fixed in concrete simply and quickly.

Means for Solving the Problems

[0007] The present invention provides a method for measuring the amount of carbon dioxide fixed by concrete, comprising: a pre-carbonation weight measurement step of measuring the weight of a concrete specimen; a carbonization curing step of placing the specimen in a sealed container and passing carbon dioxide through the sealed container; a post-carbonation weight measurement step of measuring the weight inside the sealed container after passing carbon dioxide through it; and a step of determining the amount of carbon dioxide fixed by the specimen based on the difference between the weight measured in the post-carbonation weight measurement step and the weight measured in the pre-carbonation weight measurement step.

[0008] The present invention provides a device for measuring the amount of carbon dioxide fixed in concrete, comprising: a sealed container capable of housing and sealing a test specimen molded from concrete; a dehumidifier placed inside the sealed container; and a carbon dioxide cylinder connected to the sealed container and capable of passing carbon dioxide through the sealed container. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method and apparatus for measuring the amount of carbon dioxide fixed in concrete, which can easily and quickly measure the amount of carbon dioxide fixed in concrete. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a diagram showing the schematic configuration of a carbon dioxide fixation amount measuring device according to an embodiment of the present invention. [Figure 2A] Figure 2A illustrates the concept of weight change due to carbonation of concrete. [Figure 2B] Figure 2B illustrates the concept of weight change due to carbonation of concrete from a different perspective. [Figure 3A] Figure 3A is a table showing the materials used in the concrete of the test specimens. [Figure 3B] Figure 3B is a table showing the concrete mix for the test specimens. [Figure 4]Figure 4 is a table showing the measurement results of the weight increase inside the container. [Figure 5] Figure 5 is a table showing an example of the test analysis results for TG-DTA. [Figure 6] Figure 6 is a graph showing a comparison between the amount of carbon dioxide fixed calculated from the increase in weight inside the container and the amount of carbon dioxide fixed calculated from TG-DTA. [Figure 7] Figure 7 is a flowchart showing the processing flow of the concrete carbon dioxide fixation amount measurement method according to this embodiment. [Modes for carrying out the invention]

[0011] (Carbon dioxide fixation measurement device) Embodiments of the present invention will be described with reference to the drawings. Figure 1 is a diagram showing the schematic configuration of a carbon dioxide fixation amount measuring device 1 according to an embodiment of the present invention.

[0012] As shown in Figure 1, the carbon dioxide fixation amount measuring device 1 includes a carbon dioxide cylinder 10 and a carbonation container 50. The carbon dioxide cylinder 10 is connected to the carbonation container 50 via piping 20. A regulator 30 is provided in the piping 20. The carbon dioxide in the carbon dioxide cylinder 10 is supplied to the carbonation container 50 via piping 20. The amount of carbon dioxide supplied from the carbon dioxide cylinder 10 to the carbonation container 50 is regulated by the regulator 30.

[0013] (Carbonation container) A dehumidifier 60 is provided inside the carbonation container 50. A test specimen 70 is also placed inside the carbonation container 50. The test specimen 70 is a concrete molded product on which the amount of carbon dioxide fixed is measured. It is preferable that the test specimen 70 is not placed directly on the bottom surface 52 of the carbonation container 50. In the example shown in Figure 1, the test specimen 70 is placed on the bottom surface 52 via a base member 80. By not placing the test specimen 70 directly on the bottom surface 52 of the carbonation container 50, carbon dioxide is more easily fixed from the bottom surface 52 side of the test specimen 70.

[0014] The concrete in this application is concrete containing calcium oxide. An example of concrete containing calcium oxide is cement concrete.

[0015] (Method for measuring carbon dioxide fixation amount) The method for measuring the carbon dioxide fixation amount in this embodiment focuses on the fact that the weight of concrete increases when carbonated, and measures the carbon dioxide fixation amount based on the weight change before and after carbonation.

[0016] The main reactions in the process of concrete fixing carbon dioxide by carbonation are as follows chemical reactions. First, a hydration reaction occurs. In the hydration reaction, calcium oxide reacts with water to produce calcium hydroxide. CaO + H2O -> Ca(OH)2 Next, a reaction with carbon dioxide occurs. In the reaction with carbon dioxide, calcium hydroxide reacts with carbon dioxide to produce calcium carbonate and water. Ca(OH)2 + CO2 -> CaCO3 + H2O

[0017] By this reaction with carbon dioxide, calcium ions in the concrete react with carbon dioxide. And calcium carbonate is produced. Through this process, carbon dioxide is fixed in the concrete.

[0018] Referring to Figure 2A, the concept of weight change due to carbonation of concrete will be explained. Figure 2A is a diagram showing the concept of weight change due to carbonation of concrete. The bar graph on the left side of Figure 2A shows the specimen before carbonation. The bar graph on the right side shows the specimen after carbonation. The vertical axis of Figure 2A indicates weight.

[0019] The weight of the specimen before carbonation is the sum of the weight of the concrete (calcium oxide) and the excess water (volatile matter) adsorbed by the concrete.

[0020] As described above, carbon dioxide fixation produces carbonate (calcium carbonate) and water generated during carbonation (water produced by carbonation (evaporation)).

[0021] Therefore, the weight of the sample after carbonation is the sum of the weight of the concrete (calcium oxide), the excess water adsorbed on the concrete, the carbonate (calcium carbonate), and the water generated during carbonation (water generated by carbonation (evaporation)).

[0022] (Evaporation) Both the excess water adsorbed on the concrete before carbonation and the water generated during carbonation (water generated by carbonation) are evaporable moisture (evaporated portion). These can be dehumidified by the dehumidifier 60 inside the carbonation container 50. The excess water adsorbed on the concrete before carbonation or the water generated by carbonation that has been dehumidified by the dehumidifier 60 is called dehumidified moisture.

[0023] As shown in Figure 2A, the difference between the weight of the specimen before carbonation and the sum of the weight of the specimen after carbonation and the weight of the dehumidified water, i.e., the increase in weight, represents the weight of carbon dioxide fixed.

[0024] Thus, the method for measuring carbon dioxide fixation is based on the idea that the difference between the weight of the specimen before carbonation and the weight of the specimen and the weight of water evaporated from the specimen after carbonation represents the amount of carbon dioxide fixed.

[0025] Refer to Figure 2B to explain the weight change due to carbonation of concrete from a different perspective. Figure 2B is a diagram illustrating the concept of weight change due to carbonation of concrete from a different perspective. The bar graph on the left of Figure 2A shows the specimen before carbonation. The bar graph in the center shows the specimen after carbonation. The bar graph on the right hypothetically shows the weight of the specimen after carbonation.

[0026] As shown in the bar graph on the left, the original weight of the specimen before carbonation is defined as weight (A). Weight (A) includes the weight of the concrete, the weight of the non-evaporating water contained in the specimen, and the weight of the evaporating water.

[0027] After carbonation, as shown in the central bar graph, the weight of the fixed carbon dioxide is added to the weight of the concrete, etc. Let the weight of the specimen after carbonation be weight (B). Also, after carbonation, water evaporates during the carbonation curing process. In the carbon dioxide fixation amount measurement method of this embodiment, this evaporated water is recovered in the dehumidifier 60 inside the carbonation container 50.

[0028] The bar graph on the right is a hypothetical bar graph in which the weight components have been rearranged, including the water recovered by the dehumidifier 60, in order to determine the weight of fixed carbon dioxide. In the bar graph on the right, the weight of the water recovered by the dehumidifier 60 is denoted as weight (C), and the weight of fixed carbon dioxide is denoted as weight (D). Weight (D) can be calculated by the following formula. D = B + CA In other words, the increase in weight from the original specimen (A) is equal to the weight of the fixed carbon dioxide (D).

[0029] An example of measuring carbon dioxide fixation using a carbon dioxide fixation measurement method is described. The carbon dioxide fixation measurement method can be performed using the carbon dioxide fixation measurement device 1 shown in Figure 1. The carbon dioxide fixation measurement device 1 functions as a carbonation curing device. In the carbon dioxide fixation measurement device 1, a sealed container with a capacity of 20 liters was used as the carbonation container 50. Carbon dioxide was supplied from the carbon dioxide cylinder 10 to the carbonation container 50 by adjusting the regulator 30. At that time, the pressure of the carbon dioxide was maintained at 10 kPa.

[0030] Within the carbonation container 50, moisture moves from the test specimen 70 to the dehumidifier 60. When measuring the increase in weight within the carbonation container 50, the sum of the increase in weight of the test specimen 70 and the weight of the moisture moved to the dehumidifier 60 can be considered as the increase in weight within the container. The weight of the moisture moved to the dehumidifier 60 can be said to be the weight of the moisture removed.

[0031] Here, it is possible that the moisture inside the carbonation container 50 is also included in the moisture transferred to the dehumidifier 60. However, the amount of moisture that can be considered as moisture inside the carbonation container 50 is negligible. One reason for this is that the capacity of the carbonation container 50 is not large, for example, 20L or less compared to the volume of the test specimen inside the container, which is 0.196L. Therefore, in the carbon dioxide fixation amount measurement method of this embodiment, the moisture inside the carbonation container 50 can be considered negligible.

[0032] The materials and concrete mix used in specimen 70 for the measurement are shown in Figures 3A and 3B. A tin mold with a diameter of φ50 × 100 mm was used to form the specimen. Concrete of test mixes No. 1 to No. 3 shown in Figure 3B was poured into this mold to obtain specimen 70.

[0033] After the concrete had been sealed and cured at a room temperature of 20°C for two days, it was removed from its mold and placed in a carbonation container 50. Carbonation curing was carried out for three days in an environment of 20°C, 100% carbon dioxide concentration, and 60% humidity (the humidity was maintained at approximately 60% by operating the dehumidifier 60), while dehumidifying with a dehumidifier 60.

[0034] To verify the accuracy of the carbon dioxide fixation amount measured by the carbon dioxide fixation amount measurement method of this embodiment, the amount of carbon dioxide fixation calculated based on the weight increase of the carbonation container 50 before and after carbonation curing was compared with the amount of carbon dioxide fixation calculated by test analysis.

[0035] The weight increase of the carbonation container 50 was calculated based on the sum of the weight of the test specimen 70 and the amount of moisture removed by the dehumidifier 60. An electronic scale with a weighing capacity of 6000g and a resolution of 0.1g was used for weight measurement.

[0036] For comparative testing and analysis, the results obtained by TG (thermogravimetric analysis)-DTA (differential thermal analysis) were adopted. In the TG-DTA analysis, the thermal decomposition temperature of calcium carbonate was set to a range of 450°C to 750°C based on the change in the DTG (differential thermogravimetric curve), and the weight loss was determined to calculate the carbon dioxide content. Furthermore, the carbon dioxide content calculated from the amount of carbon in the aggregate measured by EMIA-Step (carbon and sulfur analyzer) was subtracted, and the result was calculated per cubic meter of concrete. 3 The amount of carbon dioxide fixed per unit was calculated.

[0037] (Increase in weight inside the carbonation container) Figure 4 shows the measurement results of the weight increase inside the container. Figure 4 is a table showing the measurement results of the weight increase inside the container for each of the test formulations No. 1 to No. 3. In all of the test formulations No. 1 to No. 3, the total weight of the test specimen after carbonation, including the dehumidified moisture, increased compared to the weight before carbonation. The test was conducted in a sealed carbonation container, and there was no movement of moisture to the outside. Therefore, the dehumidified moisture is considered to be the evaporation of excess water from the test specimen and the evaporation of water generated by carbonation. In other words, the weight increase before and after carbonation (ΔM) is considered to be due to carbon dioxide fixation. Therefore, the amount of carbon dioxide fixed was converted from the weight increase by dividing ΔM by the volume of the test specimen.

[0038] (Test analysis results) Figure 5 shows an example of the TG-DTA test analysis results. Figure 5 shows the TG (thermogravimetric analysis) and DTA (differential thermal analysis) results for specimen No. 1, as well as the DTG (differential thermogravimetric curve). As shown in Figure 5, no dehydration by Ca(OH)2 was observed around 400°C. This confirmed that the specimen was carbonated.

[0039] (Comparison results between carbon dioxide fixation amount calculated from the increase in weight inside the container and carbon dioxide fixation amount calculated from TG-DTA) Referring to Figure 6, we will explain the comparison results between the amount of carbon dioxide fixed calculated from the increase in weight inside the container and the amount of carbon dioxide fixed calculated from TG-DTA. Figure 6 is a graph showing the comparison results between the amount of carbon dioxide fixed calculated from the increase in weight inside the container and the amount of carbon dioxide fixed calculated from TG-DTA. As shown in Figure 6, for all formulation types (test formulations) from No. 1 to No. 3, the amount of carbon dioxide fixed calculated from the increase in weight inside the container and the amount of carbon dioxide fixed calculated from TG-DTA were approximately the same.

[0040] The results shown in Figure 6 demonstrate that the amount of carbon dioxide fixed can be measured by converting it from the increase in weight inside the container.

[0041] (Carbonates in dehumidified moisture) This section describes the measurement of carbonates in the dehumidified water collected by dehumidifier 60. To verify whether the dehumidified water contained products of carbonation, the dehumidified water was dried in a constant temperature dryer at 105°C for 24 hours, and the weight of the residue was measured.

[0042] After drying the dehumidified moisture, the weight of the residue was 0.0g. This indicates that no carbonates were present in the dehumidified moisture. In other words, the amount of carbon dioxide fixed in the dehumidified moisture can be considered negligible.

[0043] As described above, in the concrete carbon dioxide fixation amount measurement method of this embodiment, the amount of carbon dioxide fixed can be measured by converting it from the increase in weight inside the container.

[0044] (Process flow of the measurement method) The processing flow of the method for measuring the amount of carbon dioxide fixed in concrete according to this embodiment will be explained with reference to Figure 7. Figure 7 is a flowchart showing the processing flow of the method for measuring the amount of carbon dioxide fixed in concrete according to this embodiment. In Figure 7 and the following explanation, S1 indicates step 1. The same applies to S2 and subsequent steps.

[0045] (S1) Step S1 is the step of preparing and curing concrete specimens. Specimen preparation can be done using formwork, for example, as explained earlier. Curing can also be done under conditions such as 2 days at room temperature, as explained earlier.

[0046] (S2) Step S2 is the step in which the weight of the specimen is measured before carbonation curing. In S2, the weight of the specimen is measured. In the weight measurement in S2, the total weight of the specimen is measured, including the weight of the water adsorbed on the specimen before curing.

[0047] (S3) Step S3 is the step of carbonation curing the specimen. In S3, carbon dioxide is fixed to the specimen. Specifically, for example, the specimen is placed in a carbonation container, and carbon dioxide is supplied to the carbonation container while maintaining a predetermined temperature and humidity, and while dehumidifying. The carbonation curing period can be, for example, 3 days.

[0048] (S4) Step S4 is the step in which the weight is measured after carbonation curing. In S4, in addition to the weight of the specimen, the weight of the moisture removed in the carbonization container is measured. The weight of the moisture removed in the carbonization container is, for example, the weight of the moisture removed by the dehumidifier if one is installed in the carbonization container.

[0049] Through steps S3 and S4, moisture inside the sealed carbonization container is collected using a dehumidifier, and the weight of the moisture collected by the dehumidifier is measured.

[0050] (S5) Step S5 is the step for calculating the amount of carbon dioxide fixed. In S5, the difference between the weight after carbonation curing and the weight before carbonation curing is calculated. Then, the increase in weight from the weight before carbonation curing to the weight after carbonation curing is divided by the volume of the specimen. This is how the amount of carbon dioxide fixed in the specimen is calculated.

[0051] The method for measuring the amount of carbon dioxide fixed by concrete in this embodiment ends in S5.

[0052] The embodiments of the present invention have been described above. The present invention is not limited to the embodiments described above, and various modifications, variations, and combinations are possible.

[0053] For example, the material of the carbonation container 50 as a sealed container can be a material with low moisture permeability and moisture absorption, such as a metal such as stainless steel. Alternatively, the material of the carbonation container 50 may be a resin, or a laminate of metal and resin. It is preferable that the carbonation container 50 is in a form in which its inside and outside are thermally insulated.

[0054] The shape and size of the carbonation container 50 should preferably be as small as possible, in accordance with the form and arrangement of the dehumidifier 60 and the test specimen 70. This allows for more accurate measurements.

[0055] It is preferable to introduce the test specimen into the carbonation container 50 using a method that minimizes human intervention. Furthermore, it is preferable to make the equipment placed inside the carbonation container 50, such as the dehumidifier 60 and measuring device, cordless to improve the airtightness of the carbonation container 50.

[0056] The source of carbon dioxide supplied to the carbonation container 50 is not limited to a carbon dioxide cylinder. For example, carbon dioxide may be supplied to the carbonation container 50 from a carbon dioxide supply line installed in a factory. Furthermore, the adjustment of the carbon dioxide pressure in the carbonation container 50 is not limited to adjustment using a valve such as a regulator. A pressure adjustment mechanism may be provided in the carbonation container 50, and the pressure of the carbon dioxide may be adjusted by this mechanism. Moreover, the adjustment of the carbon dioxide pressure is not limited to manual adjustment; for example, an adjustment mechanism that automatically adjusts the pressure based on the detection result of a pressure sensor may be provided. [Explanation of symbols]

[0057] 1. Carbon dioxide fixation amount measuring device 10 carbon dioxide cylinders 20 Piping 30 Regulator 50 Carbonation containers 52 Bottom 60 Dehumidifier 70 Specimen 80 Base component

Claims

1. A method for measuring the amount of carbon dioxide fixed by concrete, A pre-carbonation weight measurement step for measuring the weight of a specimen molded from concrete, The test specimen is placed in a sealed container, and a carbonization curing step is performed by passing carbon dioxide through the sealed container, A post-carbonation weight measurement step, which measures the weight inside the sealed container after passing carbon dioxide through it, The step includes determining the amount of carbon dioxide fixed in the specimen based on the difference between the weight measured in the post-carbonation weight measurement step and the weight measured in the pre-carbonation weight measurement step. Method for measuring carbon dioxide fixation.

2. A dehumidifier is placed inside the aforementioned sealed container. The weight measured in the post-carbonation weight measurement step is the sum of the weight of the test specimen and the weight of the moisture removed by the dehumidifier. The method for measuring the amount of carbon dioxide fixed according to claim 1.

3. A device for measuring the amount of carbon dioxide fixed by concrete, A sealed container capable of housing and sealing concrete specimens, A dehumidifier placed inside the sealed container, The system comprises a carbon dioxide cylinder connected to the sealed container and capable of passing carbon dioxide through the sealed container, A device for measuring the amount of carbon dioxide fixed by concrete.

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