Methode for analyzing distribution of cement hardened body and biochar
By uniformly dispersing biochar in concrete and evaluating its distribution using image analysis, the problem of ammonia release in new buildings is solved, and effective ammonia inhibition and cultural asset protection are achieved.
Patent Information
- Application Number
- JP2023187585
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-01
- Publication Date
- 2025-05-15
AI Technical Summary
The prior art is difficult to effectively suppress the ammonia gas released from concrete in new buildings, resulting in the degradation of cultural assets, and traditional methods such as the use of activated carbon or adsorbents have high cost and inefficiency problems.
By dispersing biochar (biochar) uniformly in concrete, it uses its adsorbed ammonia properties to inhibit the release of ammonia, and image analysis methods are used to evaluate the distribution uniformity of biochar to ensure its uniformity in concrete.
It effectively inhibits the release of ammonia in concrete, extends the "incubation period" before building use, reduces operating costs, and prevents the degradation of cultural assets.
Smart Images
Figure 2025076002000010 
Figure 2025076002000011 
Figure 2025076002000012
Abstract
Description
[Technical field]
[0001] The present invention relates to a hardened cement body and a method for analyzing the distribution of biochar. [Background technology]
[0002] In newly constructed art galleries and museums, deterioration of cultural properties on display due to chemical substances derived from building materials has become a concern, and the Institute of Cultural Heritage has published recommended indoor levels of chemical substances (see, for example, Non-Patent Document 1). In particular, concrete, which is used in large quantities as a structural material, generates ammonia gas due to the nitrogen contained in the material. In particular, a large amount of ammonia gas is generated when concrete is mixed with ground granulated blast furnace slag (for example, see Non-Patent Document 2). Four ammonia countermeasures techniques are being implemented: "not generating ammonia," "not bringing it in," "removing it," and "managing it" (see, for example, Non-Patent Document 3). [Prior art documents] [Non-patent literature]
[0003] [Non-Patent Document 1] Air Purification Guide for Art Galleries and Museums (March 2019) [Non-Patent Document 2] Ichisuke Kobayashi and Shinji Yasu, 'Mechanism of Ammonia Generation in Concrete', Proceedings of the Japan Concrete Institute, Vol. 20, No. 2, 1998. [Non-Patent Document 3] https: / / www.shimztechnonews.com / solution / key / key10.html [Non-Patent Document 4] Kazufusa Mitani, Hiroshi Iwanami, Takayuki Kubota, Chie Obayashi, Nagao Hori, Takeshi Kawachi, 'Development of an ammonia suppression method for art galleries and museums', Obayashi Corporation Research Institute Report [Non-Patent Document 5] Naoki Kagi, Hajime Tamura, Takaori Tanaka, Shuji Fujii, 'Modeling of Emitted Gas Flux Taking into Account Ambient Temperature - Emission Mechanism of Volatile Organic Compounds in Building Materials -', Journal of the Architectural Institute of Japan, Planning and Building Engineering, 539, 45-49, 2001. Summary of the Invention [Problem to be solved by the invention]
[0004] In order to prevent deterioration of cultural properties due to ammonia gas, a "drying period" is set up until the emission of ammonia gas settles down. Generally, a dry-out period of two summers (two years) is set up after pouring new concrete. However, this is not economical because the building cannot be used immediately after completion.
[0005] Known examples of "non-generation" technologies include sheets that adsorb ammonia gas (see, for example, Non-Patent Document 4). However, this technology requires the application of sheets over a wide area, and may also introduce unnecessary chemical substances.
[0006] As a "removal" technique, for example, a method is known in which a chemical filter using activated carbon is installed in a circulating air conditioning system to remove ammonia dispersed in the room and maintain air quality. This technique requires the circulating air conditioning system to be constantly running, which results in high running costs such as filter replacement costs and electricity bills.
[0007] A method is known in which activated carbon (biochar) is mixed into concrete, taking advantage of the ammonia adsorption property of activated carbon, to efficiently capture ammonia gas derived from the material and suppress ammonia gas emission from concrete. In order to efficiently capture ammonia gas, it is preferable that biochar is uniformly dispersed within the concrete. However, until now, there has been no method to quantify the degree of dispersion of biochar.
[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a hardened cement body that can efficiently suppress the emission of ammonia gas contained in the hardened cement body. Another aim of the present invention is to provide a method for analyzing the distribution of biochar in the hardened cement body. [Means for solving the problem]
[0009] The present invention has the following aspects. [1] A hardened cement composition comprising a hardened cement composition containing cement, water, fine aggregate, coarse aggregate, and biochar, The biochar content is 1 kg / m 3 More than 200kg / m 3 is as follows: A hardened cement body, wherein a heterogeneity index of the biochar in a cross section of the hardened cement body, which is calculated by the following analytical method, is 100% or less. (Analysis method) The cross section of the hardened cement body is converted into a biochar extraction image in which biochar is extracted by image analysis, and the biochar extraction image is divided into N parts (N is a natural number of 2 or more) of the same area and shape. The area ratio of the biochar in the divided biochar extraction image is calculated, and a variability index U defined by the following formula (1) is calculated from the average and standard deviation of the area ratio values (N pieces). CV The heterogeneity index of the biochar in the cross section of the hardened cement paste is calculated.
[0010]
number
[0011] [2] The hardened cement body described in [1], wherein the image analysis is a method of obtaining a biochar extraction image in which areas where biochar is distributed are extracted by binarizing the image based on brightness or luminance using image analysis software attached to a digital microscope, or a method of obtaining a biochar extraction image in which areas where biochar is distributed are extracted by carbon mapping using an electron beam microanalyzer.
[0012] [3] A method for analyzing the distribution of biochar in a cross section of a hardened cement body made of a hardened cement composition including cement, water, fine aggregate, coarse aggregate, and biochar, comprising: A first step of converting a cross section of the hardened cement body into a biochar extraction image by image analysis, the biochar being extracted; A second step of dividing the biochar extract image into N parts (N is a natural number of 2 or more) of the same area and shape, and calculating the area ratio of the biochar in the divided biochar extract image; From the average and standard deviation of the area ratio values (N pieces), the variation index U defined by the following formula (1) is calculated. CV and a third step of calculating a heterogeneity index of the biochar in a cross section of the hardened cement body, the heterogeneity index being represented by:
[0013]
number
[0014] The image analysis method of [4] is a method of obtaining a biochar extraction image in which the areas where biochar is distributed are extracted by binarizing the image based on brightness or luminance using image analysis software provided with a digital microscope, or a method of obtaining a biochar extraction image in which the areas where biochar is distributed are extracted using carbon mapping with an electron beam microanalyzer. Effect of the Invention
[0015] According to the present invention, it is possible to provide a hardened cement body capable of efficiently suppressing the emission of ammonia gas contained in the hardened cement body, and also to provide a method for analyzing the distribution of biochar in the hardened cement body. [Brief description of the drawings]
[0016] [Figure 1] This is a biochar extraction image in which the cross section of the hardened cement paste was binarized according to brightness using image analysis software attached to a digital microscope to extract the areas where biochar is distributed. [Diagram 2] This figure shows the results of dividing a biochar extract image into 16 images of equal area and shape, and calculating the area ratio of biochar within each divided image. [Diagram 3] FIG. 1 shows the results of measuring the rate of ammonia gas generation from hardened cement bodies from immediately after production until 28 days later. [Figure 4] FIG. 13 is a graph showing an estimated total amount of ammonia gas emitted from a hardened cement body immediately after production. [Diagram 5] FIG. 1 shows the relative values of the ammonia gas emission rate measured from immediately after production until 13 days later for the hardened cement body in which biochar was uniformly dispersed, the hardened cement body in which biochar was localized in the center, and the hardened cement body containing no biochar. [Figure 6] FIG. 1 shows the relative values of the ammonia gas emission rate measurement results from immediately after production until 13 days later for a hardened cement body containing biochar and a hardened cement body not containing biochar, when biochar was placed on the outside of the hardened cement body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Hereinafter, an embodiment of the present invention will be described, however, the present invention is not limited to the embodiment described below, and various modifications are possible without departing from the gist of the present invention.
[0018] [Hardened cement paste] A hardened cement product according to another embodiment of the present invention is a product (hardened product) obtained by hardening a hardenable cement composition.
[0019] "Hardenable cement composition" The hardenable cement composition includes cement, water, fine aggregate, coarse aggregate, and biochar.
[0020] <Ingredients> (cement) The cement is not particularly limited as long as it is a powder whose main raw materials are limestone, clay, silica stone, iron oxide raw materials, etc., and hardens by a chemical reaction with water. Examples of the cement include portland cement (JIS R 5210:2009), blast furnace cement (JIS R5211:2009), silica cement (JIS R 5212:2009), fly ash cement (JIS R 5213:2009), and ecocement (JIS R 5214:2009). The cement is preferably at least one selected from the group consisting of Portland cement and blast-furnace cement, and more preferably at least one selected from the group consisting of ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, blast-furnace cement type A, blast-furnace cement type B, and blast-furnace cement type C.
[0021] There are six types of Portland cement - normal, early strength, extra early strength, moderate heat, low heat and sulfate resistant - and their respective low alkali types, for a total of 12 types (JIS R 5210:2009).
[0022] Blast-furnace cement is classified into Type A, Type B, and Type C blast-furnace cement depending on the amount of blast-furnace slag mixed in (JIS R 5211:2009). Blast-furnace cement type A: Blast-furnace slag content: 5-30% by mass Blast-furnace cement type B: Blast-furnace slag content 10-60% by mass Blast-furnace cement type C: blast-furnace slag content 60-70% by mass
[0023] Portland cement generates carbon dioxide from the thermal decomposition of limestone during firing (CaCO3 → CaO + CO2↑) and the fuel required for firing during the manufacturing process. On the other hand, blast furnace slag powder, which is an admixture for blast furnace cement, does not require firing, so the amount of carbon dioxide generated during cement production can be reduced in proportion to the amount of blast furnace slag mixed. Therefore, blast furnace cement is preferable as the cement used in the hardening cement composition, and blast furnace cement type B or blast furnace cement type C, which have a large amount of blast furnace slag mixed, are more preferable, and blast furnace cement type C is even more preferable. In addition, ECM (registered trademark) (energy CO2 minimum) cement, which has the same amount of blast furnace slag mixed as blast furnace cement type C, may be used as the blast furnace cement.
[0024] The content of cement in the hardenable cement composition is not particularly limited, but is preferably 200 kg / m 3 More than 500kg / m 3 Less than 250kg / m is preferable. 3 More than 400kg / m 3 Less than 300 kg / m is more preferable. 3 More than 350kg / m 3 The following is even more preferred:
[0025] (water) The water is not particularly limited, and any water that is usually used when mixing cement, such as tap water, well water, or groundwater, can be used.
[0026] The water content in the hardenable cement composition is not particularly limited, but is preferably 50 kg / m 3 More than 250kg / m 3 Less than 100kg / m is preferable. 3 More than 200kg / m 3 The following is more preferred:
[0027] Furthermore, the ratio (mass %) of water to cement in the hardenable cement composition is not particularly limited, but is preferably from 40% to 65%, and more preferably from 45% to 60%.
[0028] (fine aggregate) There are no particular limitations on the fine aggregate, and any fine aggregate that is normally mixed with cement can be used, but sand with a particle size of 5 mm or less is preferred. The particle size of the fine aggregate is the particle size measured according to the sieve test method for aggregates (JIS A 1102:2014).
[0029] The content of the fine aggregate in the hardenable cement composition is not particularly limited, but is preferably 600 kg / m 3 More than 1000kg / m 3 Less than 700kg / m is preferable. 3 More than 900kg / m 3 The following is more preferred:
[0030] (coarse aggregate) The coarse aggregate is not particularly limited, and a coarse aggregate that is usually mixed with cement can be used, but gravel (crushed stone) with a particle size of more than 5 mm is preferable. The upper limit of the particle size of the gravel (crushed stone) is not particularly limited, but 25 mm or less is preferable. The particle size of the coarse aggregate is the particle size obtained by measuring according to the sieving test method for aggregates (JIS A 1102:2014).
[0031] The content of the coarse aggregate in the hardenable cement composition is not particularly limited, but is preferably 800 kg / m 3 More than 1200kg / m 3 Less than 900kg / m is preferable. 3 More than 1100kg / m 3 The following is more preferred:
[0032] (Biochar) Biochar is a solid material made by heating biomass at temperatures above 350°C under controlled oxygen concentrations that do not cause combustion (2019 Refinement of the 2006 IPCC Guidelines for National Greenhouse Gas Inventories).
[0033] The particle size of biochar is not particularly limited, but is preferably 10 mm or less, more preferably 5 mm or less. The lower limit of the particle size of biochar is not particularly limited, but is preferably 0.1 mm or more, more preferably 1 mm or more. Note that the particle size of biochar over 1 mm is the particle size obtained by measuring according to the sieving test method for aggregates (JIS A 1102:2014), and the particle size of biochar less than 1 mm is the average particle size obtained by measuring the particle size distribution using a laser diffraction particle size distribution measuring device.
[0034] The content of biochar in the hardenable cement composition is not particularly limited, but is preferably 5 kg / m 3 More than 100kg / m 3 Less than 10kg / m is preferable. 3 More than 80kg / m 3 Less than 15kg / m is more preferable. 3 More than 60kg / m 3 The following is even more preferable. When the biochar content is within this range, a better balance between the amount of ammonia fixed (ammonia reduction amount) and the workability of the hardened cement body is achieved.
[0035] It is preferable to use biochar as a substitute for a part of the fine aggregate. In this case, the total content of the fine aggregate and biochar in the hardenable cement composition is not particularly limited, but is preferably 600 kg / m 3 More than 1000kg / m 3 Less than 700kg / m is preferable. 3 More than 900kg / m 3 The following is more preferred:
[0036] (Other Ingredients) The hardenable cement composition may be a mixture of conventionally used components, provided that the effects of the present invention are not impaired.
[0037] <Method for producing hardenable cement composition> The hardenable cement composition can be produced by kneading cement, water, fine aggregate, coarse aggregate, and biochar. The kneading method is not particularly limited, and can be carried out by a conventionally known kneading method for hardenable cement compositions using a gravity mixer (tilt-type drum mixer, etc.), a forced mixing mixer (horizontal single-shaft type, horizontal double-shaft type, pan type, etc.), etc.
[0038] The hardened cement body of this embodiment has a biochar content of 1 kg / m 3 More than 200kg / m 3 Less than 5kg / m 3 More than 100g / m 3 Less than 20kg / m is preferable. 3 More than 80kg / m 3 The following is more preferable. When the content of biochar is within this range, a better balance between the effect of suppressing ammonia emission and the workability of the hardened cement body is achieved.
[0039] In the hardened cement body of the present embodiment, the heterogeneity index of biochar is 100% or less, preferably 90% or less, and more preferably 80% or less, in a cross-sectional image analysis. If the heterogeneity index of biochar exceeds the upper limit, there is a possibility that a sufficient ammonia emission suppression effect cannot be obtained.
[0040] The heterogeneity index of biochar in the hardened cement paste of this embodiment is the variation index U defined by the following equation (1): CV It is expressed as:
[0041]
number
[0042] In the above formula (1), N is the number of divisions of the image, A i is the area ratio of biochar in each divided image, μ bin represents the average area percentage of biochar in each segmented image.
[0043] In the present embodiment, the image analysis of the cross section of the hardened cement body is not particularly limited, but may be, for example, a method of binarizing the microscopic image obtained by photographing the cross section of the hardened cement body with a digital microscope (for example, Keyence's digital microscope VHX-6000) by brightness or luminance using the attached image analysis software to obtain a biochar extraction image in which the area where biochar is distributed is extracted. When the particle size of the biochar is small and the image of the cross section of the hardened cement body cannot be appropriately binarized with a digital microscope, it is preferable to obtain a biochar extraction image in which the area where biochar is distributed is extracted by a method using carbon mapping of the cross section of the hardened cement body using an electron beam microanalyzer (EPMA) or a method using carbon mapping of a scanning electron microscope (SEM-EDS) with an energy dispersive X-ray analyzer. After obtaining the biochar extraction image, the biochar extraction image is divided into N parts of the same area and shape ((N is a natural number of 2 or more). N is, for example, 16), and the area ratio of biochar in the divided biochar extraction images is calculated. Next, the average and standard deviation of the area ratio of biochar (N pieces) are used to calculate the variability index U defined by the above formula (1). CV The obtained variability index U CV is the heterogeneity index of biochar in the cross section of the hardened cement paste. In other words, the heterogeneity index is an index that indicates the distribution of biochar in the cross section of the hardened cement paste.
[0044] <Manufacturing method of hardened cement> In the method for producing a hardened cement product of the present embodiment, the hardened cement product is obtained by hardening the above-mentioned hardenable cement composition.
[0045] The hardening of the hardenable cement composition is usually carried out by leaving it to stand at a temperature of 0°C or higher and 50°C or lower.
[0046] According to the hardened cement body of this embodiment, the content of biochar is 1 kg / m 3 More than 200kg / m 3Since the heterogeneity index of biochar in the cross section of the hardened body calculated by the above analysis method is 100% or less, the emission of ammonia gas contained in the hardened cement body can be efficiently suppressed.
[0047] The hardened cement body thus obtained reduces the emission of ammonia gas. New concrete generates ammonia gas due to the nitrogen contained in the material. In particular, when using cement that contains blast furnace slag, such as blast furnace cement, a large amount of ammonia gas is likely to be generated. In newly built art galleries and museums, the generated ammonia gas causes discoloration of artworks and cultural properties stored there.
[0048] In order to prevent deterioration of artworks and cultural properties due to ammonia gas, measures are sometimes taken to wait six months to a year after completion for the generation of ammonia gas to subside, but this is not economical as the completed building cannot be used immediately. Also, sheets that absorb ammonia gas have been developed, but this requires work to be applied over a wide area.
[0049] By using biochar as an ammonia gas emission inhibitor, it is possible to reduce carbon dioxide emissions when producing a hardenable cement composition, and to inhibit the emission of ammonia gas from the hardened cement body (concrete) obtained by hardening the hardenable cement composition. This prevents ammonia gas from being released into the atmosphere without the need to cover it with an ammonia gas adsorption sheet, and prevents deterioration of artworks and cultural properties due to ammonia gas.
[0050] In addition, the hardened cement body of this embodiment can be expected to have an effect of suppressing the emission of chemical substances other than ammonia gas that are emitted from concrete, such as volatile alkaline compounds (such as ammonia) and volatile organic compounds (such as alkylamines).
[0051] [Method of analyzing biochar distribution] A method for analyzing biochar distribution according to one embodiment of the present invention is a method for analyzing the distribution of biochar in a cross section of a hardened cement body made of a hardened cement composition containing cement, water, fine aggregate, coarse aggregate, and biochar, the method including a first step of converting the cross section of the hardened cement body into a biochar extraction image in which biochar is extracted by image analysis; a second step of dividing the biochar extraction image into N parts (N is a natural number of 2 or more) of the same area and shape, and calculating the area ratio of biochar in the divided biochar extraction image; and a second step of calculating a variation index U defined by the above formula (1) from the average and standard deviation of the area ratio values (N pieces). CV and a third step of calculating a heterogeneity index of biochar in a cross section of the hardened cement paste, represented by:
[0052] In the first step, an image obtained by image analysis of a cross section of a hardened cement body is converted into a binary image. The image analysis of the cross section is not particularly limited, but may be, for example, a method in which the cross section of the hardened cement body is photographed with a digital microscope (e.g., Keyence Digital Microscope VHX-6000) and the microscopic image obtained is binarized by brightness or luminosity using the attached image analysis software to obtain a biochar extraction image in which the area where the biochar is distributed is extracted. When the particle size of the biochar is small and the image of the cross section of the hardened cement body cannot be appropriately binarized using a digital microscope, it is preferable to obtain a biochar extraction image in which the area where the biochar is distributed is extracted by a method using carbon mapping of the cross section of the hardened cement body using an electron beam microanalyzer (EPMA) or a method using carbon mapping of a scanning electron microscope with an energy dispersive X-ray analyzer (SEM-EDS).
[0053] In the second step, the binary image obtained in the first step is divided into N parts (N is a natural number greater than or equal to 2) of equal area and shape, and the area proportion of biochar within each divided image is calculated.
[0054] In the third step, the variation index U defined by the above formula (1) is calculated from the average and standard deviation of the area ratio values (N pieces) obtained in the second step. CV The obtained variability index U CV is an index of biochar heterogeneity in the cross section of the hardened cement paste.
[0055] According to the method for analyzing the distribution of biochar of this embodiment, it is possible to analyze the distribution of biochar in a hardened cement body.
[0056] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. EXAMPLES
[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.
[0058] [Production Example] <Material> (W)Water Tap water (C) Cement Portland cement Blast-furnace cement type B (containing 30-60% by mass of blast-furnace slag) ECM cement (contains 60-70% blast furnace slag by mass, equivalent to blast furnace cement type C) (S1) Fine aggregate Sand (particle size 5mm or less) (S2) Fine aggregate Sand (particle size 5mm or less) (G) Coarse aggregate Gravel (grain size: over 5mm, 25mm or less) (Biochar) Biochar Powder (particle size 1mm or less) Granular (particle size 2mm~5mm)
[0059] <Manufacturing method> Water (W), cement (C), fine aggregate (S1), fine aggregate (S2), coarse aggregate (G) and biochar were mixed using a tilting drum mixer in the proportions shown in Table 1 to produce hardenable cement compositions (Examples 1 to 6). The obtained hardenable cement compositions were allowed to stand at 20°C to produce hardened cement bodies. Examples 2 to 6 in which biochar was mixed are working examples, and Example 1 in which biochar was not mixed is a comparative example.
[0060] [Table 1]
[0061] [Evaluation of biochar heterogeneity index] The degree of uniform dispersion of biochar in the hardened cement paste was quantitatively evaluated by image analysis of the cross section of the hardened cement paste. Specifically, multiple images of the cross sections of the hardened cement bodies of Examples 3 to 5 were obtained and analyzed to calculate the area ratio of biochar within an area of 75 mm x 75 mm. The following are some of the image analysis results for Examples 3 and 5. First, the image of the cross section of the hardened cement body was converted into a binary image in order to extract the locations where biochar was present. As shown in Figure 1, a microscopic image of the cross section of the hardened cement body taken with a microscope was binarized by brightness or chromaticity to obtain a biochar extraction image in which the locations where biochar was distributed were extracted. Next, as shown in Figure 2, the biochar extraction image was divided into 16 equal areas and shapes, and the biochar area ratio in each divided image (15 mm x 15 mm) was calculated. This analysis was performed on multiple cross-sectional images, and the biochar area ratio in a 75 mm x 75 mm range was calculated. Finally, the coefficient of variation (variation index U ) indicating the variation was calculated from the average and variance of the biochar area ratio values (25 values) using the above formula (1). CV ) was calculated. The variability index U CV The analysis results are shown in Table 2.
[0062] [Table 2]
[0063] From the results shown in Table 2, the heterogeneity index in the hardened cement body of Example 3 was 82%, and the heterogeneity index in the hardened cement body of Example 5 was 135%. In other words, it was found that the biochar was uniformly dispersed in the hardened cement body of Example 3, whereas the biochar was non-uniformly dispersed in the hardened cement body of Example 5. As a result of similar evaluation, the non-uniformity index of the hardened cement paste of Example 4 was 71%.
[0064] [Evaluation of the ammonia emission suppression effect of biochar] The rate of ammonia gas generation was measured for each of the hardened cement bodies of Examples 1 to 6 from immediately after production until 28 days later. The rate of ammonia gas generation was measured according to the small chamber method of the Japan Air Cleaning Association's guideline "No. 34-1999 Guideline for the measurement method of molecular pollutants generated from clean room constituent materials." A series of operations was carried out in a clean room (ISO class 6). The hardened cement body was placed in a glass desiccator with an internal volume of 6 L, clean air was circulated at 1.0 L / min, and the air that had passed through was collected in pure water for several hours by the impinger method. The ammonium ion concentration in the collected liquid was quantitatively analyzed by ion chromatography, and the average rate of ammonia generation from the test specimen was calculated as μg / m. 2 / h and compared (m 2 (The surface area of the hardened cement paste is shown in Fig. 3.) Furthermore, the total amount of ammonia gas emitted immediately after production for each of the hardened cement bodies of Examples 1 to 6 (hereinafter, the total amount of ammonia gas emitted is referred to as the "total emission amount") was estimated. The total emission amount was estimated from the following equation (3) by obtaining the following regression equation (2) using a previously reported binomial exponential function model based on the data on the change in emission rate over time. Note that this model assumes that gas desorption from the material surface is dominant in the early stages of emission, and that as gas emission near the surface progresses, gas diffusion from inside the material becomes dominant (for example, see Non-Patent Document 5). The results are shown in Figure 4.
[0065]
number
[0066]
number
[0067] [Evaluation of the effect of localized biochar on emission reduction] A hardened cement body was manufactured with the same composition as in Example 3. However, unlike Example 3, it was manufactured so that biochar was localized only in the center of the hardened cement body. The hardened cement body with biochar localized in the center was designated as Example 5. The ammonia gas emission rate was measured according to the small chamber method of the Japan Air Cleaning Association's guideline "No. 34-1999 Guideline for the measurement method of molecular pollutants generated from clean room constituent materials." The series of operations was carried out in a clean room (ISO class 6). The hardened cement body was placed in a glass desiccator with an internal volume of 6 L, clean air was circulated at 1.0 L / min, and the air that passed through was collected in pure water by the impinger method for several hours. The ammonium ion concentration in the collected liquid was quantitatively analyzed by ion chromatography, and the average ammonia generation rate from the test specimen was calculated as μg / m 2 / h and compared as relative values (m 2 (R: surface area of the hardened cement body) The results of comparing the ammonia gas emission rates of the hardened cement bodies of Examples 1 and 3 are shown in FIG. From the results shown in Figure 5, when comparing the case where biochar was uniformly distributed in the hardened cement body (Example 3) with the case where the same amount of biochar was localized in the center of the hardened cement body (Example 5), the emission suppression effect of Example 3 was consistently higher from the early stage of ammonia gas emission than that of Example 5. In other words, a more effective ammonia gas emission suppression effect was obtained by distributing biochar uniformly in the hardened cement body rather than localizing it in the center.
[0068] [Evaluation of the ammonia emission suppression effect by including biochar in hardened cement] A hardened cement body was manufactured with the same composition as in Example 1, and the same amount of biochar as in Example 3 was placed on the outside of the hardened cement body for the purpose of absorbing the ammonia emitted from the hardened cement body. This test example was designated as Example 6. The ammonia gas emission rate was measured in accordance with the small chamber method of the Japan Air Cleaning Association's guideline "No. 34-1999 Guideline for the measurement method of molecular pollutants generated from clean room constituent materials." A series of operations was carried out in a clean room (ISO class 6). The hardened cement body was placed in a glass desiccator with an internal volume of 6 L, clean air was circulated at 1.0 L / min, and the air that had passed through was collected in pure water by the impinger method for several hours. The ammonium ion concentration in the liquid after collection was quantitatively analyzed by ion chromatography, and the average ammonia generation rate from the test specimen was calculated in μg / m 2 / h and compared (m 2 (where: surface area of the hardened cement body) The ammonia gas emission rates of the hardened cement bodies of Examples 1 and 3 are compared in FIG. From the results shown in Figure 6, when comparing the case where biochar was contained in the hardened cement body (Example 3) with the case where the same amount of biochar was placed outside the hardened cement body (Example 6), in the early stages of ammonia gas emission (1 day and 1.5 days of material age), the emission suppression effect of Example 6 was higher than that of Example 3. However, from the 2nd day of material age onwards, the emission suppression effect of Example 3 became higher than that of Example 6. In other words, by containing biochar in the hardened cement body rather than placing it outside, a more effective ammonia gas emission suppression effect was obtained over a longer period of time. [Industrial Applicability]
[0069] The hardened cement of the present invention maintains the same performance and workability as conventional hardened cement that does not contain biochar, and can be used in place of conventional hardened cement that does not contain biochar.
Claims
1. A hardened cement composition comprising a hardened cement composition containing cement, water, fine aggregate, coarse aggregate, and biochar, The content of the biochar is 1 kg / m ３ More than 200kg / m ３ is as follows: A hardened cement body, wherein a heterogeneity index of the biochar in a cross section of the hardened cement body, which is calculated by the following analytical method, is 100% or less. (Analysis method) The cross section of the hardened cement body is converted into a biochar extraction image in which biochar is extracted by image analysis, and the biochar extraction image is divided into N parts (N is a natural number of 2 or more) of the same area and shape. The area ratio of the biochar in the divided biochar extraction image is calculated, and a variation index U defined by the following formula (1) is calculated from the average and standard deviation of the area ratio values (N pieces). ＣＶ The heterogeneity index of the biochar in the cross section of the hardened cement paste is calculated. [0010] (In formula (1), N is the number of divisions of the image, A ｉ is the area ratio of biochar in each divided image, μ ｂｉｎ represents the average area ratio of biochar in each segmented image.)
2. The cement hardened body described in claim 1, wherein the image analysis is a method of obtaining a biochar extraction image in which areas where biochar is distributed are extracted by binarizing the image based on brightness or luminance using image analysis software attached to a digital microscope, or a method of obtaining a biochar extraction image in which areas where biochar is distributed are extracted by carbon mapping using an electron beam microanalyzer.
3. A method for analyzing a distribution of biochar in a cross section of a hardened cement body, the cross section being made of a hardened cement composition including cement, water, fine aggregate, coarse aggregate, and biochar, comprising: A first step of converting a cross section of the hardened cement body into a biochar extraction image by image analysis, the biochar being extracted; A second step of dividing the biochar extract image into N parts having the same area and shape (N is a natural number of 2 or more), and calculating the area ratio of the biochar in the divided biochar extract image; From the average and standard deviation of the area ratio values (N pieces), a variation index U defined by the following formula (1) is calculated. ＣＶ and a third step of calculating a heterogeneity index of the biochar in a cross section of the hardened cement body, the heterogeneity index being represented by: [0025] (In formula (1), N is the number of divisions of the image, A ｉ is the area ratio of biochar in each divided image, μ ｂｉｎ represents the average area ratio of biochar in each segmented image.)
4. The method for analyzing biochar distribution described in claim 3, wherein the image analysis is a method of obtaining a biochar extraction image in which areas where biochar is distributed are extracted by binarizing the image based on brightness or luminance using image analysis software provided with a digital microscope, or a method of obtaining a biochar extraction image in which areas where biochar is distributed are extracted using carbon mapping with an electron beam microanalyzer.