Method and system for carbonating concrete structure

Abstract

To provide a system and method that safely carbonates a concrete structure with high efficiency and can easily estimate a carbonation degree.SOLUTION: The system comprises a carbon dioxide source, a pump, a first flow meter and a first concentration meter. The carbon dioxide source is constituted to store carbon dioxide contained gas. The pump is constituted to convey the carbon dioxide contained gas. The first flow meter and the first concentration meter are constituted to measure a flow rate of the carbon dioxide contained gas and a carbon dioxide concentration, respectively. The pump, the first flow meter, and the first concentration meter form a circulation path of the carbon dioxide contained gas by connecting them to each other. The carbon dioxide source is arranged on a first flow path branched from the circulation path. The circulation path is constituted to penetrate a concrete structure.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] One embodiment of the present invention relates to a method and a system for carbonating a concrete structure by bringing it into contact with carbon dioxide.

Background Art

[0002] Concrete is a structural material mainly composed of cement hydrates. Calcium hydroxide, which mainly constitutes the cement hydrates, reacts with carbon dioxide to change into calcium carbonate. This reaction is also called carbonation. By carbonation, the concrete is neutralized and its strength increases. As methods for estimating the degree of carbonation, there are known methods such as measuring the elastic wave velocity on the surface of the concrete, using a neutralization progress prediction formula, using a neutralization rate coefficient, and using the reflection light spectrum from the concrete surface (see, for example, Patent Documents 1 to 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] Through the carbonation of concrete, it is possible to contribute to the reduction of carbon dioxide, which is one of the greenhouse gases. However, the carbon dioxide that was used in this carbonation but not actually immobilized will be released into the atmosphere. Therefore, one of the problems to be solved in one embodiment of the present invention is to provide a method and a system for carbonating a concrete structure. Alternatively, one of the problems to be solved in one embodiment of the present invention is to provide a system and a method that can carbonize a concrete structure efficiently and safely and can easily estimate the degree of carbonation. Alternatively, one of the problems to be solved in one embodiment of the present invention is to provide a system and a method that can easily grasp the amount of carbon dioxide input during the carbonation of a concrete structure, the amount of carbon dioxide fixed, and the amount of carbon dioxide released into the atmosphere without being fixed by the carbonation of the input.

Means for Solving the Problems

[0005] One embodiment of the present invention is a system for carbonating a concrete structure. This system includes a carbon dioxide supply source, a pump, and a first flow meter and a first concentration meter. The carbon dioxide supply source is configured to store a carbon dioxide-containing gas. The pump is configured to transport the carbon dioxide-containing gas. The first flow meter and the first concentration meter are each configured to measure the flow rate and the carbon dioxide concentration of the carbon dioxide-containing gas. The pump, the first flow meter, and the first concentration meter are connected to each other to form a circulation path for the carbon dioxide-containing gas. The carbon dioxide supply source is arranged on a first flow path branched from the circulation path. The circulation path is configured to penetrate the concrete structure.

[0006] One embodiment of the present invention is a system for carbonating a concrete structure. The system includes a carbon dioxide source, a pump, a chamber, and a first flow meter and a first concentration meter. The carbon dioxide source is configured to store a carbon dioxide-containing gas. The pump is configured to transport the carbon dioxide-containing gas. The chamber is configured to receive the carbon dioxide-containing gas and accommodate the concrete structure. The first flow meter and the first concentration meter are each configured to measure the flow rate and the carbon dioxide concentration of the carbon dioxide-containing gas, respectively. The pump, the chamber, the first flow meter, and the first concentration meter are connected to each other to form a circulation path for the carbon dioxide-containing gas. The carbon dioxide source is connected to a first flow path branched from the circulation path.

[0007] One embodiment of the present invention is a method for carbonating a concrete structure. The method includes placing the concrete structure on a circulation path of a carbon dioxide-containing gas formed by a pump, a first flow meter, and a first concentration meter, supplying the carbon dioxide-containing gas from a carbon dioxide source on a first flow path branched from the circulation path to the circulation path, and circulating the carbon dioxide-containing gas in the circulation path using the pump. The first flow meter and the first concentration meter are each configured to measure the flow rate and the carbon dioxide concentration of the carbon dioxide-containing gas in the circulation path, respectively. The concrete structure is arranged such that the circulation path passes through the concrete structure.

[0008] One embodiment of the present invention is a method for carbonating a concrete structure. The method includes placing a concrete structure on a circulation path of a carbon dioxide-containing gas formed by a pump, a chamber, a first flow meter, and a first concentration meter, supplying the carbon dioxide-containing gas from a carbon dioxide source on a first flow path branched from the circulation path to the circulation path, and circulating the carbon dioxide-containing gas in the circulation path using the pump. The chamber is configured to store the carbon dioxide-containing gas. The first flow meter and the first concentration meter are configured to measure the flow rate and the carbon dioxide concentration of the carbon dioxide-containing gas in the circulation path, respectively. The concrete structure is placed in the chamber.

Brief Description of the Drawings

[0009]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6A

Figure 6B

Best Mode for Carrying Out the Invention

[0010] Hereinafter, each embodiment of the present invention will be described with reference to the drawings and the like. However, the present invention can be implemented in various modes without departing from the gist thereof, and is not to be construed as being limited to the description of the embodiments exemplified below.

[0011] For the sake of clearer explanation, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is merely an example and does not limit the interpretation of the present invention. In this specification and each figure, elements having the same functions as those already described with respect to the previously shown figures may be denoted by the same reference numerals, and duplicate explanations may be omitted.

[0012] In this specification, concrete refers to a cured product that does not exhibit fluidity, which is obtained by the hardening of a cement hydrate produced by the reaction of cement, which is one of the raw materials, with water. Therefore, mortar that does not contain aggregate is also included in the category of concrete. Concrete may contain fine aggregate with a diameter of 5 mm or less and coarse aggregate with a diameter exceeding 5 mm (for example, larger than 5 mm and 20 mm or less, or 10 mm or more and 20 mm or less). On the other hand, concrete before hardening, that is, a mixture containing cement and water and having fluidity without being completely hardened, is called ready-mixed concrete (also referred to as fresh concrete). Ready-mixed concrete may contain additives such as AE agents (air-entraining agents), fluidizing agents, and thickeners in addition to cement, water, and aggregate.

[0013] Hereinafter, a system (hereinafter also simply referred to as the "system") and method for carbonating a concrete structure according to one embodiment of the present invention will be described. There are no restrictions whatsoever on the size, shape, installation location, etc. of the concrete structure to be carbonated. Therefore, the concrete structure may be, for example, columns, walls, beams of buildings or houses, piers and abutments of bridges, dams, levees and breakwaters provided in rivers and harbors, wave-dissipating blocks, and concrete for road and tunnel lining. Alternatively, it may be a movable property (concrete product) containing concrete such as concrete blocks and paving stones having various shapes. Carbonation may be performed before the ready-mix concrete applied to the concrete structure is completely cured, or after the ready-mix concrete is completely cured.

[0014] 1. Configuration of the System FIG. 1A shows a block diagram of a system 100 according to one embodiment of the present invention. The system 100 includes a carbon dioxide source 110, a pump 120, and a flow meter 140 and a concentration meter 150. The system 100 may further include a buffer tank 130. The pump 120, the flow meter 140, and the concentration meter 150 are connected by a tube through which a carbon dioxide-containing gas can flow, and form a circulation path 102 indicated by a dashed line in FIG. 1A by the pump 120, the flow meter 140, and the concentration meter 150. In other words, the pump 120, the flow meter 140, and the concentration meter 150 are arranged on the circulation path 102. When the buffer tank 130 is provided, the buffer tank 130 is also arranged on the circulation path 102 and is connected to other components such as the pump 120 by a tube to form the circulation path 102. In the system 100, a flow path (branch path) 106 for discharging the carbon dioxide-containing gas from the circulation path 102 is further connected to the circulation path 102. The flow path 106 is a tube branched from the circulation path 102, and a valve 174 for controlling its opening and closing is provided in the flow path 106. Although details will be described later, the concrete structure 200 to be carbonated is also arranged on the circulation path 102. Therefore, by circulating the carbon dioxide-containing gas in the circulation path 102 using the pump 120 (see the curved arrow), the carbon dioxide-containing gas repeatedly passes through the pump 120, the flow meter 140, and the concentration meter 150, and can repeatedly contact the concrete structure 200.

[0015] (1) Carbon dioxide source The carbon dioxide supply source 110 is a cylinder or a tank configured to store a high-pressure carbon dioxide-containing gas. There is no particular restriction on the carbon dioxide concentration in the carbon dioxide-containing gas, and it may be higher than the carbon dioxide concentration in the atmosphere. To achieve efficient carbonation, preferably, the carbon dioxide concentration is 10% by volume or more and 100% by volume or less, 50% or more and 100% by volume or less, or 90% by volume or more and 100% by volume or less. The carbon dioxide-containing gas may further contain a noble gas such as nitrogen, oxygen, or argon as a gas other than carbon dioxide. The pressure of the carbon dioxide-containing gas in the carbon dioxide supply source 110 is, for example, 1 MPa or more and 5 MPa or less at 15°C. Although not shown, a regulator is attached to the carbon dioxide supply source 110 to adjust the pressure of the carbon dioxide-containing gas discharged from the carbon dioxide supply source 110.

[0016] The carbon dioxide supply source 110 is not disposed on the circulation path 102, but is disposed on a flow path (branch path) 104 that is a tube branched from the circulation path 102. The connection position between the flow path 104 and the circulation path 102 can be arbitrarily determined, but it is preferably upstream of the pump 120 and the flow path 104 is connected to the circulation path 102 downstream of the concentration meter 150. Since the concrete structure 200 is downstream of the pump 120 and upstream of the concentration meter 150, by adopting the above connection relationship, a carbon dioxide-containing gas with a high carbon dioxide concentration can be supplied to the concrete structure 200 via the pump 120. In addition, the carbon dioxide in the carbon dioxide-containing gas after contacting the concrete structure 200 can be monitored by the concentration meter 150 without being affected by the carbon dioxide-containing gas before contacting the concrete structure 200. As an optional configuration, a valve 170 for controlling the opening and closing of the connection between the flow path 104 and the circulation path 102 may be provided on the flow path 104. Alternatively, the function of the valve 170 may be realized by a regulator.

[0017] (2) Pump The pump 120 is a driving mechanism for transporting and circulating the carbon dioxide-containing gas in the circulation path 102. There is no restriction on the configuration of the pump 120, and it may be a positive displacement pump or a non-positive displacement pump. Examples of the former include piston pumps, diaphragm pumps, plunger pumps, gear pumps, screw pumps, tube pumps, etc. Examples of the latter include centrifugal pumps and propeller pumps. The pressure is applied to the carbon dioxide-containing gas in the circulation path 102 by the pump 120, and the pressurized carbon dioxide-containing gas is supplied directly to the concrete structure 200 or after being stored in the buffer tank 130.

[0018] (3) Flowmeter and concentration meter The flowmeter 140 is a device for measuring the flow rate of the carbon dioxide-containing gas circulating in the circulation path 102. There is no restriction on the installation position of the flowmeter 140. For example, the flowmeter 140 may be installed upstream or downstream of the pump 120. There is no restriction on the mechanism by which the flowmeter 140 measures the flow rate. Therefore, the flowmeter 140 may be a float-type flowmeter, a turbine-type flowmeter, or a diaphragm-type flowmeter, a Coriolis-type flowmeter. By using a float-type flowmeter or a turbine-type flowmeter, the system 100 can be constructed at low cost. The flowmeter 140 may be configured to transmit the measured value to an external terminal. Thereby, the flow rate of the carbon dioxide-containing gas can be monitored on the external terminal.

[0019] The carbon dioxide concentration meter 150 is a device that measures the carbon dioxide concentration in the carbon dioxide-containing gas circulating in the circulation path 102. The concentration meter 150 is located downstream of the concrete structure 200 and upstream of the pump 120. The concentration meter 150 may be provided upstream of the flow meter 140 and downstream of the concrete structure 200. There is no restriction on the mechanism by which the concentration meter 150 measures the carbon dioxide concentration. Therefore, the concentration meter 150 may be a concentration meter that utilizes non-dispersive infrared absorption, a concentration meter equipped with a solid electrolyte sensor that decomposes and utilizes carbonates such as sodium carbonate, or a concentration meter equipped with a photoacoustic sensor. The concentration meter 150 may also be configured to transmit the measured value to an external terminal. Thereby, the carbon dioxide concentration in the carbon dioxide-containing gas can be monitored on the external terminal.

[0020] (4) Buffer tank The buffer tank 130, which has an arbitrary configuration, is configured to increase the amount of carbon dioxide-containing gas introduced into and circulated in the circulation path 102, and is configured to store the carbon dioxide-containing gas pressurized by the pump 120. By providing the buffer tank 130, a large amount of carbon dioxide-containing gas can be circulated in the circulation path 102, so that a large amount of carbon dioxide can be supplied to the concrete structure 200. The volume of the buffer tank 130 can be appropriately selected according to the size of the concrete structure 200 to be carbonated and the degree of carbonation. For example, it may be 1 L or more and 2000 L or less, 50 L or more and 1000 L or less, 100 L or more and 500 L or less, or 1 L or more and 10 L or less. As will be described later, the pressure of the carbon dioxide-containing gas in the circulation path 102 is adjusted to be higher than the atmospheric pressure (about 0.1 MPa) and 0.5 MPa or less. Therefore, the buffer tank 130 is configured to be able to store at least the gas within the above range of pressure. Note that a compressor in which the functions of the pump 120 and the buffer tank 130 are integrated may be used as the pump 120 and the buffer tank 130.

[0021] (5) Other configurations On the circulation path 102 of the system 100, in addition to the pump 120, buffer tank 130, flow meter 140, and concentration meter 150 described above, various components can be arranged. For example, as shown in the block diagram of FIG. 1B, the system 100 can include a pressure regulator 160 on the circulation path 102. The pressure regulator 160 is provided on the downstream side of the pump 120. The pressure regulator 160 has a pressure increasing valve and is configured to maintain or increase the pressure of the carbon dioxide-containing gas on its upstream side. When the pressure regulator 160 is provided, the arrangement position of the flow meter 140 is arbitrary, but by arranging the flow meter 140 on the downstream side of the pump 120 and the upstream side of the pressure regulator 160, the pressure of the carbon dioxide-containing gas in contact with the concrete structure 200 can be measured more accurately. The arrangement location of the concentration meter 150 is also arbitrary and may be arranged on the upstream side or the downstream side of the pressure regulator 160.

[0022] In the carbonation of the concrete structure 200, calcium hydroxide, which is the main component of concrete, reacts with carbon dioxide to produce calcium carbonate and water. Therefore, as carbonation progresses, the water in the carbon dioxide-containing gas circulating through the circulation path 102 increases. To prevent corrosion of the pump 120, buffer tank 130, etc. by water, a moisture trap device 180 may be provided on the circulation path 102. There are no restrictions on the configuration of the moisture trap device 180 either. For example, a configuration may be adopted in which the circulating carbon dioxide-containing gas is cooled to 0 °C or lower to trap water vapor as water or ice. Alternatively, the moisture trap device 180 may be configured such that a porous adsorbent material such as silica gel or zeolite is brought into contact with the carbon dioxide-containing gas. The arrangement location of the moisture trap device 180 is also arbitrary. For example, it may be provided on the upstream side of the pump 120 and on the downstream side of the flow meter 140, concentration meter 150, or pressure regulator 160. Alternatively, it may be provided on the downstream side of the concrete structure and on the upstream side of the flow meter 140, concentration meter 150, or pressure regulator 160. When the moisture trap device 180 is provided, a valve 176 for forming a bypass path from the carbon dioxide supply source 110 to the flow path 106 without passing through the moisture trap device 180 may be provided.

[0023] System 100 may further additionally include a valve 172 for discharging the carbon dioxide-containing gas. The valve 172 is disposed on a flow path (branch path) 108 branched from the circulation path 102. By not arranging a concentration meter or a flow meter in the flow path 108, the carbon dioxide-containing gas can be discharged at a large flow rate when the valve 172 is opened. Therefore, the valve 172 can be used as a release valve in an emergency (for example, when the pressure in the circulation path 102 becomes abnormally high).

[0024] System 100 may further include a flow meter 142 and / or a concentration meter 152 on the downstream side of the valve 174 in the flow path 106. By providing the flow meter 142 and / or the concentration meter 152, the total amount and the carbon dioxide concentration of the carbon dioxide-containing gas discharged from the circulation path 102 can be grasped. Therefore, the amount of carbon dioxide used for carbonation can be estimated more accurately. Since the flow meter 142 and the concentration meter 152 can have the same or similar configurations as the flow meter 140 and the concentration meter 150 respectively, further description is omitted.

[0025] As shown in FIG. 2, system 100 may further include a chamber 190 on the circulation path 102. The chamber 190 is provided on the downstream side of the pump 120 and the buffer tank 130. When the pressure regulator 160 is provided, the chamber 190 is on the downstream side of the pump 120 and is disposed on the upstream side of the pressure regulator 160. The flow meter 140 and / or the concentration meter 150 may be disposed on the upstream side or the downstream side of the chamber 190. Since the chamber 190 also forms the circulation path 102, the carbon dioxide-containing gas is introduced into the chamber 190 and then discharged. As will be described later, the chamber 190 is configured to be able to accommodate one or more concrete structures 200. Although not shown, the chamber 190 may be provided with a heating mechanism for heating the carbon dioxide-containing gas. The heating mechanism may be configured to heat the carbon dioxide-containing gas at a temperature of 30°C or higher and 100°C or lower, 40°C or higher and 60°C or lower, for example. The higher the temperature of the carbon dioxide-containing gas, the greater the carbon dioxide fixation rate can be.

[0026] The material contained in the tube connecting each component can also be arbitrarily selected. For example, it may be a metal such as copper, stainless steel, or aluminum, or it may contain polymers such as poly(tetrafluoroethylene), polyvinyl chloride, silicone resin, polyurethane, polypropylene, natural rubber or synthetic rubber, polyester, or polyamide.

[0027] 2. Method for carbonating a concrete structure Hereinafter, a method for carbonating the concrete structure 200 using the system 100 will be described.

[0028] (1) Connection between the concrete structure and the system A flowchart showing an example of a method for carbonating the concrete structure 200 is shown in FIG. 3. As shown in FIG. 3, first, the concrete structure 200 is connected to the system 100. There are no particular restrictions on the connection method. For example, as shown in FIG. 4A, a through-hole 200a is provided in the concrete structure 200, and the tube 122 constituting the circulation path 102 is connected to both ends of the through-hole 200a. The through-hole 200a may be provided in the concrete structure 200 in advance, or may be formed by processing the existing concrete structure 200. The tube 122 itself does not penetrate the through-hole 200a. Therefore, the through-hole 200a constitutes the circulation path 102, and the inner wall of the through-hole 200a comes into contact with the carbon dioxide-containing gas. In other words, the circulation path 102 penetrates the concrete structure 200. With this configuration, leakage of the carbon dioxide-containing gas is prevented, and the carbon dioxide in the carbon dioxide-containing gas can be used efficiently and safely.

[0029] There is no restriction on the number of through holes 200a provided in each concrete structure 200, and a plurality of through holes 200a may be provided (FIG. 4B). In this case, the tube 122 may be branched and its branched end may be connected to the through hole 200a. There is no restriction on the inner diameter and shape of the through hole 200a (the shape of the surface perpendicular to the extending direction of the through hole 200a), and it may be appropriately determined according to the size, shape, design, degree of carbonation, etc. of the concrete structure 200.

[0030] Alternatively, as shown in FIG. 5, a chamber 190 may be provided on the circulation path 102, and one or a plurality of concrete structures 200 may be arranged in the chamber 190. A tube 122 is connected to the chamber 190 such that the inside of the chamber 190 forms the circulation path 102. Thereby, the carbon dioxide-containing gas can pass through the chamber 190, and leakage of the carbon dioxide-containing gas is prevented. Note that the chamber 190 does not necessarily need to form a hermetically sealed space inside. For example, the chamber 190 may be configured to cover the concrete structure 200 by being arranged on the surface on which the concrete structure 200 is installed or arranged without having a bottom surface.

[0031] (2) Introduction and circulation of carbon dioxide-containing gas Thereafter, a carbon dioxide-containing gas is introduced into the circulation path 102. Specifically, the valves 170 and 174 are opened. When the valves 172 and 176 are provided, these valves are closed to form a bypass path from the carbon dioxide supply source 110 to the flow path 106. Thereafter, a carbon dioxide-containing gas is supplied from the carbon dioxide supply source 110 to the circulation path 102, and the pump 120 is operated. Thereby, the circulation path 102 is filled with the carbon dioxide-containing gas. When the buffer tank 130 is used, the buffer tank 130 is filled with a carbon dioxide-containing gas at a predetermined pressure.

[0032] Subsequently, valves 170 and 174 are closed. If valve 176 is provided, it is opened. Thereby, a circulation path 102 is formed, and the circulation of the carbon dioxide-containing gas is started using pump 120. Note that these valve operations, i.e., the circulation of the carbon dioxide-containing gas, are started after the flow rate of the carbon dioxide-containing gas measured by flow meter 140 reaches a steady state and the carbon dioxide concentration measured by concentration meter 150 coincides with or substantially coincides with the carbon dioxide concentration of the carbon dioxide-containing gas filled in carbon dioxide supply source 110. When pressure regulator 160 is used, the circulation of the carbon dioxide-containing gas is started after the flow rate corresponding to the pressure set by pressure regulator 160 is reached and the carbon dioxide concentration coincides with or substantially coincides with the carbon dioxide concentration of the carbon dioxide-containing gas filled in carbon dioxide supply source 110. The pressure of the carbon dioxide-containing gas in circulation path 102 may be set to 0.1 MPa or more and 0.5 MPa or less, or 0.1 MPa or more and 0.3 MPa or less using pump 120 or pressure regulator 160. Thereby, since the carbon dioxide-containing gas at or above atmospheric pressure can repeatedly come into contact with concrete structure 200, the carbonation rate increases and the carbon dioxide-containing gas can be efficiently utilized.

[0033] (3) Monitoring of Carbonation and Discharge of Carbon Dioxide-Containing Gas The carbonation monitoring can be performed based on the carbon dioxide concentration and flow rate in the carbon dioxide-containing gas circulating in the circulation path 102. Specifically, from the volume of the circulation path 102 (i.e., the total volume of the pump 120, flow meter 140, concentration meter 150, buffer tank 130, pressure regulator 160, moisture trap device 180, through hole 200a or chamber 190, and tube 122 that make up the circulation path 102) and the change amount of the carbon dioxide concentration, the amount of carbon dioxide consumed by carbonation is calculated. Also, the amount of calcium hydroxide reacting with carbon dioxide can be calculated from the volume and composition of the concrete structure 200. Therefore, by using the flow meter 140 and the concentration meter 150, the progress state of carbonation can be monitored in real time. Also, by providing communication devices for transmitting the measured values to an external terminal to the flow meter 140 and the concentration meter 150, the progress state of carbonation can also be monitored remotely.

[0034] When the carbonation has not reached a predetermined level, the circulation can be continued. When the carbonation has reached a predetermined level, the valve 174 is opened, and the carbon dioxide-containing gas is discharged through the flow path 106 using the pump 120. Here, the predetermined level of carbonation is appropriately determined from, for example, the pressure, flow rate, carbon dioxide concentration of the carbon dioxide-containing gas, the composition of the concrete, the temperature of carbonation, the volume of the circulation path 102, the rate of carbonation (carbonation depth), etc. At this time, the flow rate and carbon dioxide concentration of the discharged carbon dioxide-containing gas are measured using the flow meter 142 and the concentration meter 152, respectively. Since the pressure outside the circulation path 102 is atmospheric pressure, carbon dioxide-containing gas at atmospheric pressure remains in the circulation path 102. For this reason, the sum of the volume of the carbon dioxide-containing gas flowing through the flow meter 142 and the volume of the circulation path 102 becomes the total volume of the carbon dioxide-containing gas used for carbonation. From this total volume and the change amount of the carbon dioxide concentration, the amount of carbon dioxide consumed by carbonation can be estimated, and the degree of carbonation can be grasped.

[0035] In addition, when the carbon dioxide concentration in the carbon dioxide-containing gas significantly decreases as carbonation progresses, or when the flow rate of the carbon dioxide-containing gas significantly decreases, the carbon dioxide-containing gas in the circulation path 102 may be discharged, and according to the method described above, the carbon dioxide-containing gas may be supplied from the carbon dioxide source 110 to the circulation path 102 again.

[0036] As described above, by carbonating the concrete structure 200 using the system 100, the progress of carbonation can be monitored extremely simply, and the amount of fixed carbon dioxide can be grasped. Generally, when the concrete structure 200 is a movable property and its weight can be easily measured, the degree of carbonation can be estimated from the weight change before and after carbonation. However, the weight of the movable concrete structure 200 cannot always be easily measured. Also, in the case of an immovable concrete structure, it is substantially impossible to measure the weight. On the other hand, in the carbonation method using the system 100 according to one embodiment of the present invention, carbonation can be monitored in real time and the amount of fixed carbon dioxide can be grasped without using special or large-scale measuring devices and without being affected by external environments such as temperature, humidity, and carbon dioxide concentration on the concrete surface, and the composition and type of concrete. Further, when the chamber 190 is used, carbonation can be monitored and the amount of fixed carbon dioxide can be accurately grasped without destroying the concrete structure 200.

Example

[0037] In this example, an example of carbonating a concrete block using the system 100 will be described.

[0038] As schematically shown in FIG. 6A, a concrete block having a height, width, and length of 100 mm, 100 mm, and 400 mm, respectively, and a through hole 200a (φ9 mm) penetrating the center of the cross section perpendicular to the longitudinal direction was produced. The cement used was ordinary Portland cement manufactured by Taiheiyo Cement Corporation, and the unit water content was 170 kg / m 3, the amount of cement per unit was set to 340 kg / m 3 This concrete block was placed on the circulation path 102 of the system 100 shown in FIG. 1A. That is, tubes 122 were connected to both ends of the through-hole 200a, and the concrete block was placed between the buffer tank 130 and the flow meter 140. A mixed gas containing 80% by volume of carbon dioxide and 20% by volume of nitrogen was introduced from the carbon dioxide supply source 110 into the circulation path 102, and the pressure of the mixed gas injected into the through-hole 200a was adjusted to 0.3 MPa using the pressure regulator 160, and the circulation was started. The flow rate of the mixed gas at this time was 1 L / min.

[0039] Twenty-four hours and 72 hours after the start of the circulation of the mixed gas, the concrete block was cut in a direction perpendicular to its longitudinal direction, and an ethanol solution of 1% phenolphthalein as an indicator was sprayed on the exposed cross-section. Since concrete in which carbonation has not progressed shows alkalinity, the indicator turns red, but when carbonation occurs, the pH drops below about 10, so no color development is observed. Therefore, the rate of carbonation (carbonation depth) can be determined from the range where the indicator shows color. As schematically shown in FIG. 6B, 24 hours after the start of the circulation of the mixed gas, no color development of the indicator was observed in the range 200b where the distance D from the center of the cross-section was about 30 mm, and color development was observed only in the range 200c around the range 200b. On the other hand, 72 hours after the start of the circulation of the mixed gas, no color development of the indicator was observed throughout the cross-section. From this, it was confirmed that under the conditions of this example, carbonation of the concrete block was not completed 24 hours after the start of the circulation of the mixed gas, and the entire concrete block was carbonated within 72 hours or less.

[0040] A part of the concrete block 72 hours after the start of the circulation of the mixed gas was collected and differential thermal calorimetry was performed. Specifically, using a differential thermal thermogravimetric analyzer (model Thermo Plus EVO02 TG-DTA) manufactured by Rigaku Corporation, the sample was heated under a nitrogen gas flow with a temperature increase rate of 10 °C / min, and the amount of carbon dioxide fixed in the concrete block was estimated assuming that the weight loss from 700 °C to 900 °C was due to the contribution of carbon dioxide removal by the thermal decomposition of calcium carbonate. As a result, the carbon dioxide fixed in the concrete block was estimated to be 140 kg / m 3 It was estimated as such. From the carbonation depth determined using an indicator and the results of differential thermal calorimetry, it was found that 50.4 g and 560 g of carbon dioxide were fixed 24 hours and 72 hours after the start of the circulation of the mixed gas, respectively.

[0041] The carbon dioxide concentrations measured by the concentration meter 150 24 hours and 72 hours after the start of the circulation of the mixed gas were 78% and 75%, respectively. Based on these results, the amount of carbon dioxide fixed in the concrete block was calculated according to the method described above. As a result, the amount of fixed carbon dioxide was estimated to be 56.9 g 24 hours after the start of the circulation of the mixed gas and 427 g 72 hours after the start, and a good agreement was obtained with the results calculated using differential thermal calorimetry and an indicator.

[0042] The above results indicate that by applying the system 100 according to one embodiment of the present invention and the carbonation method of the concrete structure 200 using the same, carbonation can be monitored at any time, and the amount of carbon dioxide fixed in the concrete structure 200 can be estimated non-destructively.

[0043] Each of the embodiments described above as embodiments of the present invention can be implemented in appropriate combination as long as they do not contradict each other. Based on each embodiment, those in which a person skilled in the art appropriately adds, deletes, or changes the design of components are also included in the scope of the present invention as long as they have the gist of the present invention.

[0044] Even if there are other operational effects different from those brought about by each of the above-described embodiments, those that are obvious from the description in this specification or can be easily predicted by those skilled in the art are naturally understood to be brought about by the present invention.

Explanation of Signs

[0045] 100: System, 102: Circuit, 104: Flow path, 106: Flow path, 108: Flow path, 110: Carbon dioxide supply source, 120: Pump, 122: Tube, 130: Buffer tank, 140: Flow meter, 142: Flow meter, 150: Concentration meter, 152: Concentration meter, 160: Pressure regulator, 170: Valve, 172: Valve, 174: Valve, 176: Valve, 180: Moisture trap device, 190: Chamber, 200: Concrete structure, 200a: Through hole, 200b: Range, 200c: Range

Claims

1. A carbon dioxide supply source configured to store a carbon dioxide-containing gas, a pump configured to transport the carbon dioxide-containing gas, and a first flow meter and a first concentration meter configured to measure the flow rate and the carbon dioxide concentration of the carbon dioxide-containing gas, respectively, wherein the pump, the first flow meter, and the first concentration meter are connected to each other to form a circulation path for the carbon dioxide-containing gas, the carbon dioxide supply source is disposed on a first flow path branched from the circulation path and the circulation path is configured to penetrate a concrete structure, a system for carbonating the concrete structure.

2. A carbon dioxide supply source configured to store a carbon dioxide-containing gas, a pump configured to transport the carbon dioxide-containing gas, a chamber configured to introduce the carbon dioxide-containing gas and accommodate a concrete structure, and a first flow meter and a first concentration meter configured to measure the flow rate and the carbon dioxide concentration of the carbon dioxide-containing gas, respectively, wherein the pump, the chamber, the first flow meter, and the first concentration meter are connected to each other to form a circulation path for the carbon dioxide-containing gas, and the carbon dioxide supply source is connected to a first flow path branched from the circulation path, a system for carbonating a concrete structure.

3. The system according to claim 1 or 2, further comprising a moisture trap device on the circulation path.

4. The system according to claim 1 or 2, further comprising a second concentration meter and a second flow meter configured to measure the carbon dioxide concentration and the flow rate of the carbon dioxide-containing gas, respectively, on a second flow path branched from the circulation path.

5. The system according to claim 1 or 2, further comprising a buffer tank configured to store the carbon dioxide-containing gas on the circulation path.

6. The system according to claim 1 or 2, further comprising a pressure regulator configured to adjust the pressure of the carbon dioxide-containing gas in the circulation path on the circulation path.

7. A method for carbonating a concrete structure, placing the concrete structure on a circulation path of a carbon dioxide-containing gas formed by a pump, a first flow meter, and a first concentration meter Supplying the carbon dioxide-containing gas from a carbon dioxide source on a first flow path branched from the circulation path to the circulation path, and circulating the carbon dioxide-containing gas in the circulation path using the pump, including the first flowmeter and the first concentration meter are configured to measure the flow rate and carbon dioxide concentration of the carbon dioxide-containing gas in the circulation path, respectively, the method wherein the concrete structure is arranged such that the circulation path penetrates the concrete structure.

8. A method for carbonating a concrete structure, placing the concrete structure on a circulation path of a carbon dioxide-containing gas formed by a pump, a chamber, a first flowmeter, and a first concentration meter, supplying the carbon dioxide-containing gas from a carbon dioxide source on a first flow path branched from the circulation path to the circulation path, and circulating the carbon dioxide-containing gas in the circulation path using the pump, including the chamber is configured to store the carbon dioxide-containing gas, the first flowmeter and the first concentration meter are configured to measure the flow rate and carbon dioxide concentration of the carbon dioxide-containing gas in the circulation path, respectively, the method wherein the concrete structure is arranged in the chamber.

9. The method according to claim 7 or 8, further comprising trapping water in the carbon dioxide-containing gas using a moisture trap device arranged on the circulation path.

10. discharging the carbon dioxide-containing gas in the circulation path to a second flow path branched from the circulation path, and The method according to claim 7 or 8, further comprising measuring the carbon dioxide concentration and the flow rate of the discharged carbon dioxide-containing gas using a second concentration meter and a second flowmeter arranged on the second flow path.

11. The method according to claim 7 or 8, further comprising storing the carbon dioxide-containing gas in a buffer tank arranged on the circulation path.

12. The method according to claim 7 or 8, further comprising adjusting the pressure of the carbon dioxide-containing gas in the circulation path using a pressure regulator arranged on the circulation path.

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