Method for estimating amount of carbon dioxide fixed in recycled coarse aggregate

Abstract

To provide a method for estimating the amount of carbon dioxide fixed in recycled coarse aggregate, which enables the amount of carbon dioxide fixed by the recycled coarse aggregate during a storage period to be estimated in a short period of time.SOLUTION: A method includes: measuring pH of a sample of mixed mortar obtained from recycled a coarse aggregate after production and before storage; estimating a mortar mixing rate of a mixed mortar contained in the recycled coarse aggregate based on a crushing value obtained by a crushing test conducted using samples taken from the recycled coarse aggregate before storage or during storage after production; measuring pH of a sample of the mixed mortar obtained from the recycled coarse aggregate at the time of shipment after storage; calculating a decrease in pH of the mixed mortar during the storage period from the pH measurement results; estimating a CO2 fixation rate of the mixed mortar during the storage period based on the decrease in pH; and estimating an amount of CO2 fixed by the recycled coarse aggregate during the storage period based on the estimated mortar mixing rate and CO2 fixation rate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for estimating the amount of carbon dioxide fixed in recycled coarse aggregate. [Background technology]

[0002] Recycled coarse aggregate is made from concrete chunks such as debris generated during the demolition of buildings and structures, and is composed of aggregate (raw aggregate) that was used in the original concrete (raw concrete) and cement paste. This cement paste is crushed during the manufacturing process, increasing its contact area with the air, so it absorbs and fixes carbon dioxide (CO2) from the air during storage. For these reasons, recycled coarse aggregate can be used as a CO2 storage destination.

[0003] There is no standardized test method for determining the amount of CO2 fixed by recycled coarse aggregate during storage, but a common method is to take samples at the time of production (before storage) and at the time of shipping (after storage) of the recycled coarse aggregate, and determine the difference in the amount of CO2 fixed (at shipping - at production) measured by differential thermogravimetric analysis (TG-DTA) (Non-Patent Document 1). TG-DTA is a method for quantifying substances contained in a sample by simultaneously and continuously measuring the mass change (TG) and thermal behavior (DTA), such as heat generation and endothermic heat generation, that occur when the sample is heated. The amount of CO2 fixed in recycled coarse aggregate is calculated from the amount of calcium carbonate (CaCO3) measured by TG-DTA using the following formula (1) (Non-Patent Document 1). CO2 = CaCO3 × MCO2 / MCaCO3 (1) Here, MCO2 is the molecular weight of CO2, and MCaCO3 is the molecular weight of CaCO3.

[0004] Patent Document 1 aims to provide a method for easily determining whether or not a recycled aggregate can be expected to have a quality improvement effect through carbon dioxide adsorption, without having to measure the mortar mixing rate of the recycled aggregate (paragraph

[0006] ), and discloses a method for determining the quality improvement effect of carbon dioxide adsorption of recycled aggregate (

[0008]

[0015] ), and discloses that the crushing value and carbon dioxide adsorption ratio of recycled aggregate are effective indexes for determining whether or not the recycled aggregate can be expected to have a quality improvement effect through carbon dioxide adsorption

[0007] . [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-189617 A [Patent Document 2] JP 2014-237559 A [Patent Document 3] JP 2020-15659 A [Non-patent literature]

[0006] [Non-Patent Document 1] "Nationwide survey on carbon dioxide fixation through concrete use and recycling," Concrete Engineering, Vol. 49, No. 8, p. 9-16, August 2011) [Non-Patent Document 2] "Study on quality control method and evaluation criteria for the amount of mortar mixed in recycled coarse aggregate" Proceedings of the Japan Concrete Institute, Vol.35, No.1, 2013, p.1453-1458) [Non-Patent Document 3] "Study on a method for producing low-energy recycled coarse aggregate by forced adsorption of CO2 gas" Proceedings of the Japan Concrete Institute, Vol.36, No.1, 2014, p.1732-1737 [Non-Patent Document 4] "Study on Estimation Method of Penetration Depth of Deterioration Factors Using pH Distribution Obtained from Drilled Powder" Proceedings of the Japan Concrete Institute, Vol.37, No.1, 2015, p.1711-1716 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to evaluate the CO2 fixation effect of using recycled coarse aggregate, it is necessary to determine the amount of CO2 fixed. To determine the amount of CO2 fixed by recycled coarse aggregate during storage using conventional methods, it is necessary to measure using TG-DTA. However, since TG-DTA measurements require specialized analytical equipment, they must be outsourced to a testing institution. In this case, it takes several days from sending the sample to obtaining the measurement results. For this reason, it is difficult to use this method for daily management or timely confirmation of the amount of CO2 fixed at factories that manufacture recycled aggregate or recycled aggregate concrete.

[0008] In addition, the conventional method can be used to measure using recycled coarse aggregates containing raw aggregates, but the sampling error is large, and in order to calculate the accurate amount of CO2, it is necessary to increase the frequency of sampling and measurement. On the other hand, it is possible to analyze using cement paste mixed in the recycled coarse aggregate, but it is necessary to determine the amount of cement paste in the recycled coarse aggregate. In general, the recycled coarse aggregate is immersed in hydrochloric acid to dissolve the cement paste, and the amount is calculated from the mass difference before and after dissolution. However, it takes one to several days to dissolve the cement paste, and the hydrochloric acid needs to be replaced during that time, which is time-consuming and labor-intensive, making it difficult to use for daily management. In addition, there is also the issue that it cannot be used when the raw aggregate is limestone.

[0009] Patent Document 1 lists the crushing value and the carbon dioxide adsorption ratio as indicators used to judge whether or not the quality of recycled aggregate can be improved, but does not estimate the amount of CO2 fixed in the recycled aggregate during storage. In addition, Patent Document 2 measures the CO2 content of mortar from the amount of inorganic carbon using a coulometer (product name / manufactured by Nippon Ans Co., Ltd.) in the examples, but this is a measurement by a conventional method. In addition, Patent Document 3 discloses a method for fixing carbon dioxide in a cementitious hardened body, but does not disclose the measurement of the amount of fixed carbon dioxide.

[0010] In view of the problems with the conventional technology as described above, the present invention aims to provide a method for estimating the amount of carbon dioxide (CO2) fixed in recycled coarse aggregate, which can estimate the amount of carbon dioxide fixed by the recycled coarse aggregate during the storage period in a short period of time. [Means for solving the problem]

[0011] A method for estimating the amount of carbon dioxide fixed in recycled coarse aggregate to achieve the above object is a method for estimating the amount of carbon dioxide fixed by the recycled coarse aggregate during a storage period from production of the recycled coarse aggregate from concrete blocks to shipment, comprising the steps of: a first step of obtaining a sample of mixed mortar from the recycled coarse aggregate after production and before storage and measuring the pH; a second step of conducting a crushing test using a sample taken from the recycled coarse aggregate after production and before storage or during storage to obtain a crushing value of the recycled coarse aggregate; a third step of estimating a mortar mixing rate of the mixed mortar contained in the recycled coarse aggregate based on the crushing value; a fourth step of obtaining a sample of mixed mortar from the recycled coarse aggregate after storage and at the time of shipment and measuring the pH; a fifth step of calculating an amount of decrease in pH of the mixed mortar during the storage period from the pH measurement results of the first step and the fourth step; a sixth step of estimating a CO2 fixation rate of the mixed mortar during the storage period based on the amount of decrease in pH; and a seventh step of estimating an amount of CO2 fixed by the recycled coarse aggregate during the storage period based on the mortar mixing rate in the third step and the CO2 fixation rate in the sixth step.

[0012] According to this method for estimating the amount of carbon dioxide fixed in recycled coarse aggregate, the amount of CO2 fixed by the recycled coarse aggregate during the storage period from its production to shipment can be estimated in a shorter time than the conventional TG-DTA method by utilizing the crushing value of the recycled coarse aggregate and the measurement results of the pH of the mixed mortar contained in the recycled coarse aggregate before and after storage.

[0013] In the above method for estimating the amount of carbon dioxide fixation in recycled coarse aggregate, the mortar mixing ratio of the mixed mortar in the third step can be estimated based on the crushed value obtained in the second step from the relationship between the crushed value and the mortar mixing ratio obtained in advance.

[0014] In addition, the CO2 fixation rate of the mixed mortar in the sixth step can be calculated based on the decrease in pH of the mixed mortar obtained in the fifth step from the following formula (2) which shows the relationship between the decrease in pH of the mixed mortar obtained in advance and the CO2 fixation rate of the mixed mortar. MCO2 = a × ΔpH + b (2) Where, MCO2: CO2 fixation rate (%) of mixed mortar during the storage period ΔpH: The decrease in pH of the mixed mortar during the storage period a, b: coefficients

[0015] In addition, the amount of CO2 fixed by the recycled coarse aggregate during the storage period in the seventh step can be calculated by the following formula (3). JPEG2025029765000002.jpg34160However, RGCO2: The amount of CO2 fixed per ton (t) of recycled coarse aggregate during the storage period (kg-CO2 / t) RG: Mass of the recycled coarse aggregate (t) M m : Mortar mixing rate (%) MCO2: CO2 fixation rate (%) of the mixed mortar during the storage period

[0016] In addition, the amount of CO2 fixed per ton (t) of the recycled coarse aggregate during the storage period can be estimated within the range of ±1 kg-CO2 / t. Effect of the Invention

[0017] According to the present invention, the amount of carbon dioxide (CO2) fixed by recycled coarse aggregate during storage can be estimated in a short period of time. [Brief description of the drawings]

[0018] [Figure 1] 4 is a flowchart for explaining each step of a method for estimating the amount of carbon dioxide fixed in recycled coarse aggregate according to the present embodiment. [Diagram 2] 1 is a graph showing the relationship between the 2.5 mm crushing value and the mortar mixing ratio of recycled coarse aggregates M and L shown in Non-Patent Documents 2 and 3. [Diagram 3] 1 is a graph showing the relationship between the amount of decrease in pH of the mixed mortar obtained in this experiment and the CO2 fixation rate (actual measured value) during the storage period. [Figure 4] 1 is a graph showing the relationship between the actual measured value and the estimated value of the CO2 fixation rate of the mixed mortar. [Diagram 5] 1 is a graph showing the relationship between the actual measured value and the estimated value of the amount of CO2 fixed by recycled coarse aggregate during the storage period. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a flow chart for explaining each step of a method for estimating the amount of fixed carbon dioxide in recycled coarse aggregate according to this embodiment.

[0020] In this embodiment, recycled coarse aggregate undergoes the following processes: use as a building or structure, demolition of the building or structure, production (S01) by crushing and classifying concrete blocks such as demolition debris generated during the demolition using a crusher or other crushing machine at a factory, storage (S02), and subsequent shipping (S03), as shown in Fig. 1. The time range of CO2 fixation of the recycled coarse aggregate targeted in this embodiment does not include the period of use or the time of CO2 fixation during demolition, but is the period (storage period) from production (S01) to shipping (S03) in Fig. 1.

[0021] Each step of the method for estimating the amount of fixed carbon dioxide in recycled coarse aggregate according to this embodiment is performed as shown in Fig. 1. That is, first, mixed mortar (mortar lump) is obtained from the recycled coarse aggregate after production and before storage, and is dissolved in a solvent and extracted. That is, a sample of the mixed mortar is taken from the recycled coarse aggregate, and the sample is ground to prepare a powder sample (S11), and the pH is measured by a pH test (S12).

[0022] Meanwhile, a sample is taken from the recycled coarse aggregate after production and before storage or during storage, and a crushing test is carried out (S13), and the crushing value of the recycled coarse aggregate under a load of 200 kN is obtained (S14).

[0023] Next, the amount of mixed mortar contained in the recycled coarse aggregate (mortar mixing rate) is estimated based on the crushing value obtained in step S14 from the relationship between the crushing value and the amount of mixed mortar obtained in advance (S15). Note that the order of performing the sampling in step S11 and the sampling in step S13 is not limited to this order, and they may be performed simultaneously in parallel as long as both are performed after production and before storage, or the sampling in step S13 may be performed before the sampling in step S11.

[0024] Next, mixed mortar (mortar lump) is obtained from the recycled coarse aggregate after storage and at the time of shipping, and is dissolved in a solvent for extraction. That is, a sample of mixed mortar is obtained from the recycled coarse aggregate, and the sample is ground to prepare a powder sample to prepare a suspension (S16), and the pH is measured by a pH test (S17).

[0025] Next, the amount of decrease in pH of the mixed mortar during the storage period (before and after storage) is calculated from the results of the pH measurements in steps S12 and S17 (S18).

[0026] Next, the CO2 fixation rate of the mixed mortar during the storage period is estimated based on the decrease in pH of the mixed mortar obtained in step S18 (S19). For example, it is calculated based on the decrease in pH of the mixed mortar obtained in step S18 from the following formula (2) showing the relationship between the decrease in pH of the mixed mortar and the CO2 fixation rate of the mixed mortar obtained in advance (S19).

[0027] MCO2 = a × ΔpH + b (2) Where, MCO2: CO2 fixation rate of mixed mortar during storage period (%) ΔpH: Decrease in pH of mixed mortar during storage a, b: coefficients

[0028] The amount of CO2 fixed by the recycled coarse aggregate during the storage period is estimated based on the mortar mixing rate estimated in step S15 and the CO2 fixation rate estimated in step S19 (S20). For example, the amount of CO2 fixed by the recycled coarse aggregate during the storage period is calculated using the following formula (3).

[0029]

number

[0030] Where, RGCO2: Amount of CO2 fixed per ton (t) of recycled coarse aggregate (kg-CO2 / t) RG: Mass of recycled coarse aggregate (t) M m : Mortar mixing rate (%) MCO2: CO2 fixation rate (%) of mixed mortar during storage

[0031] According to the method for estimating the amount of fixed carbon dioxide in recycled coarse aggregate of this embodiment, instead of calculating the amount of cement paste in the conventional method, the amount of mixed mortar (mortar contained in recycled aggregate) is estimated from the crushing value (S13 to S15), the amount of CO2 fixed by the mixed mortar during the storage period is estimated using the difference (decrease) in pH of the mortar block contained in the recycled coarse aggregate before and after storage (S18, S19), and the amount of CO2 fixed by the recycled coarse aggregate during the storage period is estimated using these estimation results (S20), so that the estimation can be performed in a shorter time than the conventional method using TG-DTA. That is, by simply performing the crushing test of the recycled coarse aggregate (S13) and the pH test of the mixed mortar contained in the recycled coarse aggregate before and after storage (S12, S17), the amount of CO2 fixed by the recycled coarse aggregate during the storage period can be estimated more simply and in a shorter time than the conventional method.

[0032] Next, we will explain the method for measuring the crushing value in steps S13 and S14 in Figure 1. This method for measuring the crushing value complies with JIS A 5023:2018 Appendix C.

[0033] (1) A sample obtained from the produced recycled coarse aggregate before storage is packed into a weighing container and then the mass is measured. (2) The sample is transferred to the test vessel, packed, and then the steel plunger is placed flat on the sample in the test vessel. (3) The test vessel is placed on the loading device and loaded at a rate of 40 kN per minute. (4) After the applied load reaches 200 kN, the load is returned to zero. (5) Sift the sample in the test container through a 2.5 mm sieve and weigh the mass of the sample that passes through the sieve. (6) Calculate the mass fraction of the sample that passed through the 2.5 mm sieve relative to the total sample. (7) The above procedure is carried out three times, and the average value of the three tests is the crushing value.

[0034] In addition, although JIS A 5023:2018 Appendix C specifies that the load in (4) is 100 kN, the load was set to 200 kN because there is a good relationship between the crushing value of the recycled coarse aggregate and the mortar mixing ratio at a load of 200 kN (see Non-Patent Documents 2 and 3).

[0035] Next, a method for measuring the pH of the mixed mortar in steps S11, S12 and steps S16, S17 in FIG. 1 will be described (see Non-Patent Document 4).

[0036] (1) Take a sample of mixed mortar from the recycled coarse aggregate, grind it so that it passes through a 150 μm sieve, and obtain a powder sample. (2) Place the powder sample in a container and prepare a suspension with a solids concentration of 10%. (3) Place the measuring part of a glass electrode pH meter into the suspension and seal the opening of the container to prevent outside air from entering the container. (4) Stir the suspension with a magnetic stirrer (rotation speed: 200 to 300 rpm) for 24 hours. (5) The pH of the suspension is measured continuously every 5 minutes from the start of stirring until the end of stirring. (6) The maximum pH value measured within 24 hours shall be the pH of the mixed mortar.

[0037] [Verification experiment] (Experimental conditions) For the purpose of verifying the effectiveness of the estimation method of this embodiment for different types of recycled coarse aggregate and storage methods, an experiment was carried out with the factors and levels shown in Table 1 below. The combinations of types of recycled coarse aggregate and storage methods used in this experiment are shown in Table 2 below. Note that recycled coarse aggregates L and M refer to the types of recycled coarse aggregate, and the applicable range is stipulated by the JIS standard.

[0038] [Table 1]

[0039] [Table 2]

[0040] (Experimental Results) Mortar mixing ratio (actual value) The mortar mixing rate (actual measured value) of each recycled coarse aggregate after production and before storage was determined by immersing the recycled coarse aggregate in hydrochloric acid and measuring the mass difference before and after dissolution. The results are shown in Table 3 below.

[0041] [Table 3]

[0042] CO from mixed mortar 2 Fixation rate (actual value) The CO2 fixation rate (actual value) of the mixed mortar during the storage period was calculated by calculating the amount of CO2 in the mixed mortar before and after storage from the TG-DTA measurement results using the following formula (4), and then calculating the difference between the values ​​before and after storage. The results are shown in Table 4 below. CO2 fixation rate of mixed mortar (actual value) = CO2 fixation rate after storage - CO2 fixation rate before storage (4)

[0043] [Table 4]

[0044] CO from recycled coarse aggregate 2 Fixed amount (actual value) The amount of CO2 fixed by the recycled coarse aggregate during the storage period (actual value) was calculated by substituting the actual values ​​of the mortar mixing rate and the CO2 fixation rate of the mixed mortar into the above formula (3), and is shown in Table 5 below.

[0045] [Table 5]

[0046] Measurement results of pH decrease of mixed mortar The pH measurement results for each sample and the amount of pH decrease before and after storage are shown in Table 6 below.

[0047] [Table 6]

[0048] Next, the estimation results obtained by the estimation method of this embodiment will be compared with actual measured values ​​to verify them.

[0049] Estimation of mortar mixing ratio The mortar mixing ratio (estimated value) was calculated by substituting the crushed value into the following formula (5) obtained by linear regression of the relationship between the crushed value (crushing test using a 2.5 mm sieve) of recycled coarse aggregates M and L shown in Non-Patent Documents 2 and 3 and the mortar mixing ratio, as shown in Figure 2. The estimated mortar mixing ratio, the actual measured value in Table 3, and the difference between the estimated value and the actual measured value are shown in Table 7 below.

[0050] M m =3.94×CV-9.5 (5) Here, Mm: Mortar mixing rate (%) CV: Crushing value (%)

[0051] [Table 7]

[0052] CO of mixed mortar during storage 2 Estimation of fixation rate The CO2 fixation rate (estimated value) of the mixed mortar was calculated by substituting the amount of decrease in pH of the mixed mortar into the following formula (6) obtained by linear regression of the relationship between the amount of decrease in pH of the mixed mortar obtained in this experiment and the CO2 fixation rate (actual value) during the storage period, as shown in Figure 3. The estimated values ​​of the CO2 fixation rate of the mixed mortar during the storage period, the actual values ​​in Table 4, and the difference between the estimated values ​​and the actual values ​​are shown in Table 8 below. Figure 4 shows the relationship between the actual values ​​and the estimated values ​​of the CO2 fixation rate of the mixed mortar.

[0053] M CO2 = 0.9557 × ΔpH (6) Here, M CO2: CO2 fixation rate (estimated value) of mixed mortar during storage period (%) ΔpH: Decrease in pH of mixed mortar before and after storage

[0054] [Table 8]

[0055] CO of recycled coarse aggregate during storage 2 Estimation of fixed quantity The amount of CO2 fixed in the recycled coarse aggregate (estimated value) was calculated by substituting the above-mentioned estimated value of the mortar mixing rate and the estimated value of the CO2 fixation rate of the mixed mortar into the above-mentioned formula (3). The estimated value, actual measured value, difference between the estimated value and the actual measured value, and error rate of the amount of CO2 fixed in the recycled coarse aggregate during the storage period are shown in Table 9 below. Figure 5 shows the relationship between the actual measured value and the estimated value of the amount of CO2 fixed in the recycled coarse aggregate during the storage period.

[0056] [Table 9]

[0057] As described above, the following was confirmed from the results of the verification experiment regarding the effectiveness of the method for estimating the amount of CO2 fixed by the recycled coarse aggregates M and L during the storage period according to this embodiment. (1) The CO2 fixation rate of the mixed mortar during storage can be estimated using the decrease in pH. (2) The amount of CO2 fixed by recycled coarse aggregate during the storage period can be estimated using the mortar mixing rate estimated from the crushing value and the CO2 fixation rate estimated from the decrease in pH of the mixed mortar. (3) As shown in Figure 5, the difference between the estimated and measured amounts of CO2 fixed per ton (t) of recycled coarse aggregate during the storage period is generally within ±1 kg-CO2 / t.

[0058] Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to these, and various modifications are possible within the scope of the technical concept of the present invention.

[0059] In step S11 in Fig. 1, samples were taken from the recycled coarse aggregate after production but before storage, and "before storage" includes not only before the start of storage but also immediately after the start of storage. In step S16 in Fig. 1, samples were taken from the recycled coarse aggregate after storage and at the time of shipment, and "after storage and at the time of shipment" includes not only at the time of shipment but also immediately after storage and the period of preparation for shipment. [Industrial Applicability]

[0060] According to the present invention, the amount of carbon dioxide fixed by recycled coarse aggregate during the storage period can be estimated more easily and in a shorter time than conventional methods. Therefore, for example, in a factory that produces recycled coarse aggregate or recycled coarse aggregate concrete, the amount of CO2 fixed by recycled coarse aggregate during the storage period can be used as one of the daily management items.

Claims

1. A method for estimating the amount of carbon dioxide fixed by recycled coarse aggregate during a storage period from production of the recycled coarse aggregate from concrete blocks to shipment, comprising: A first step of obtaining a sample of mixed mortar from the recycled coarse aggregate after production and before storage and measuring the pH; A second step of performing a crushing test using a sample taken from the recycled coarse aggregate after production and before or during storage to obtain a crushing value of the recycled coarse aggregate; A third step of estimating a mortar mixing ratio of the mixed mortar contained in the recycled coarse aggregate based on the crushing value; A fourth step of obtaining a sample of mixed mortar from the recycled coarse aggregate after storage and at the time of shipping and measuring the pH; A fifth step of calculating a decrease in pH of the mixed mortar during the storage period from the pH measurement results of the first step and the fourth step; CO of mixed mortar during the storage period ２ A sixth step of estimating the fixation rate based on the decrease in pH; The mortar mixing rate in the third step and the CO ２ The amount of CO fixed by the recycled coarse aggregate during the storage period based on the fixation rate ２ and a seventh step of estimating the amount of carbon dioxide fixed in recycled coarse aggregate.

2. 2. The method for estimating the amount of carbon dioxide fixation in recycled coarse aggregate as described in claim 1, wherein the mortar mixing ratio of the mixed mortar in the third step is estimated based on the crushed value obtained in the second step from a relationship between the crushed value and the mortar mixing ratio obtained in advance.

3. The CO of the mixed mortar in the sixth step ２ The fixation rate was calculated by comparing the decrease in pH of the mixed mortar and the CO ２ The method for estimating the amount of carbon dioxide fixation in recycled coarse aggregate according to claim 1 or 2, wherein the amount of carbon dioxide fixation is calculated based on the decrease in pH of the mixed mortar obtained in the fifth step from the following equation (2) which shows the relationship with the fixation rate: MCO ２ =a×ΔpH +b (2) However, MCO ２ : CO of mixed mortar during the storage period ２ Fixed rate (%) ΔpH: decrease in pH of the mixed mortar during the storage period a, b: coefficients

4. In the seventh step, the CO fixed by the recycled coarse aggregate during the storage period is ２ The method for estimating the amount of carbon dioxide fixation in recycled coarse aggregate according to claim 1 or 2, wherein the amount is calculated by the following formula (3). However, R.G.C.O. ２ : CO fixed per ton (t) of recycled coarse aggregate during the storage period ２ amount (kg-CO ２ / t) RG: Mass of the recycled coarse aggregate (t) M ｍ : Mortar mixing rate (%) MCO ２ : CO of mixed mortar during the storage period ２ Fixed rate (%)

5. The amount of CO fixed per ton (t) of the recycled coarse aggregate during the storage period ２ The amount is ±1kg-CO ２ The method for estimating the amount of carbon dioxide fixed in recycled coarse aggregate according to claim 1 or 2, wherein the amount of carbon dioxide fixed in recycled coarse aggregate is estimated within a range of / t.

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