JP7518034B2 - CO2 content measurement method - Google Patents
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- 238000000691 measurement method Methods 0.000 title claims description 8
- 239000004568 cement Substances 0.000 claims description 63
- 239000000463 material Substances 0.000 claims description 50
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 44
- 239000000920 calcium hydroxide Substances 0.000 claims description 44
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 44
- 238000005259 measurement Methods 0.000 claims description 43
- 238000000034 method Methods 0.000 claims description 40
- 238000005443 coulometric titration Methods 0.000 claims description 24
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 20
- 238000004458 analytical method Methods 0.000 claims description 11
- 238000004455 differential thermal analysis Methods 0.000 claims description 10
- 238000002411 thermogravimetry Methods 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 5
- 230000005611 electricity Effects 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 4
- 238000002834 transmittance Methods 0.000 claims description 4
- 239000012298 atmosphere Substances 0.000 claims description 3
- 230000002378 acidificating effect Effects 0.000 claims 1
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 88
- 229910002092 carbon dioxide Inorganic materials 0.000 description 44
- 235000011116 calcium hydroxide Nutrition 0.000 description 42
- 238000006297 dehydration reaction Methods 0.000 description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 9
- 239000004567 concrete Substances 0.000 description 7
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 6
- 239000011398 Portland cement Substances 0.000 description 4
- 239000002956 ash Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- 235000019738 Limestone Nutrition 0.000 description 3
- 229910000019 calcium carbonate Inorganic materials 0.000 description 3
- 235000010216 calcium carbonate Nutrition 0.000 description 3
- 229910052681 coesite Inorganic materials 0.000 description 3
- 229910052906 cristobalite Inorganic materials 0.000 description 3
- 230000018044 dehydration Effects 0.000 description 3
- 239000006028 limestone Substances 0.000 description 3
- 235000012239 silicon dioxide Nutrition 0.000 description 3
- 239000002893 slag Substances 0.000 description 3
- 229910052682 stishovite Inorganic materials 0.000 description 3
- 229910052905 tridymite Inorganic materials 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- -1 admixtures Substances 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000010881 fly ash Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000013558 reference substance Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 239000000440 bentonite Substances 0.000 description 1
- 229910000278 bentonite Inorganic materials 0.000 description 1
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 1
- 235000012241 calcium silicate Nutrition 0.000 description 1
- JHLNERQLKQQLRZ-UHFFFAOYSA-N calcium silicate Chemical compound [Ca+2].[Ca+2].[O-][Si]([O-])([O-])[O-] JHLNERQLKQQLRZ-UHFFFAOYSA-N 0.000 description 1
- 229910052918 calcium silicate Inorganic materials 0.000 description 1
- FGZBFIYFJUAETR-UHFFFAOYSA-N calcium;magnesium;silicate Chemical compound [Mg+2].[Ca+2].[O-][Si]([O-])([O-])[O-] FGZBFIYFJUAETR-UHFFFAOYSA-N 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
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- 239000004927 clay Substances 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
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- GDVKFRBCXAPAQJ-UHFFFAOYSA-A dialuminum;hexamagnesium;carbonate;hexadecahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Al+3].[Al+3].[O-]C([O-])=O GDVKFRBCXAPAQJ-UHFFFAOYSA-A 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
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- 239000011413 geopolymer cement Substances 0.000 description 1
- 229920003041 geopolymer cement Polymers 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
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- 229910001701 hydrotalcite Inorganic materials 0.000 description 1
- 229960001545 hydrotalcite Drugs 0.000 description 1
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- 239000008399 tap water Substances 0.000 description 1
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- YKAIJSHGJPXTDY-CBDGTLMLSA-N α-cao Chemical compound C([C@@H](N(CC1)C)C23C=CC4([C@H](C3)N(CCCl)CCCl)OC)C3=CC=C(O)C5=C3[C@@]21[C@H]4O5 YKAIJSHGJPXTDY-CBDGTLMLSA-N 0.000 description 1
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- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Description
本発明は、ＣＯ２含有率測定方法に関する。 The present invention relates to a method for measuring CO2 content.
温室効果ガス削減に向けた取り組みとして、製造時にＣＯ２を強制的に吸収させたコンクリート製品（以下、ＣＯ２吸収コン）が一部実用化されている。ＣＣＵＳ技術（Ｃａｒｂｏｎ ｄｉｏｘｉｄｅ Ｃａｐｔｕｒｅ ａｎｄ Ｓｔｏｒａｇｅの略で、二酸化炭素回収・貯留技術）の一種であるＣＯ２吸収コンは、２０１９年に経済産業省が発表した「カーボンリサイクル技術ロードマップ」でも言及され、普及拡大に向けた技術開発が行われている。普及拡大に当っては性能指標となる炭酸化前後での材料中ＣＯ２含有量を精度良く定量できる評価手法を確立し、標準化することも重要である。 As an effort to reduce greenhouse gas emissions, some concrete products that forcibly absorb CO2 during manufacturing (hereinafter referred to as CO2 absorption concrete) have been put into practical use. CO2 absorption concrete, a type of CCUS technology (short for Carbon Dioxide Capture and Storage), was also mentioned in the "Carbon Recycling Technology Roadmap" announced by the Ministry of Economy, Trade and Industry in 2019, and technological development is being carried out to promote its widespread use. In order to promote its widespread use, it is also important to establish and standardize an evaluation method that can accurately quantify the CO2 content in the material before and after carbonation, which is a performance indicator.
セメント系材料中のＣＯ２吸収量は、一般に示差熱－熱重量同時分析（ＴＧ－ＤＴＡ法）で所定温度範囲での質量減少量から定量されることが多い（例えば、特許文献１の実施例参照）。 The amount of CO2 absorbed in a cement-based material is generally quantified from the amount of mass loss in a given temperature range using simultaneous differential thermal analysis (TG-DTA method) (see, for example, the examples in Patent Document 1).
しかし、セメント系材料中の水酸化カルシウム含有率が所定値以上となると、水酸化カルシウムの脱水反応による影響が出てしまい、ＴＧ－ＤＴＡ法だと測定精度が低くなることがある。 However, when the calcium hydroxide content in a cement-based material exceeds a certain value, the dehydration reaction of calcium hydroxide can have an effect, and the measurement accuracy of the TG-DTA method can be reduced.
以上から、本発明は、水酸化カルシウムの脱水反応による影響が出ないように、セメント系材料中のＣＯ２含有率を精度よく測定できるＣＯ２含有率の測定方法を提供することを目的とする。 In view of the above, an object of the present invention is to provide a method for measuring the CO 2 content in a cement-based material with high accuracy without being affected by the dehydration reaction of calcium hydroxide.
測定に対する作業性を考慮すれば、ＴＧ－ＤＴＡを用いる方が良いが、既述のとおりセメント系材料中の水酸化カルシウム含有率が所定値以上となると、水酸化カルシウムの脱水反応による影響が出てしまい、測定精度が低くなることがある。そこで、本発明者らは、水酸化カルシウム含有率が所定値以上となった場合は、電量滴定法で測定することで、水酸化カルシウムの脱水反応による影響が出ないように、セメント系材料中のＣＯ２含有率を精度よく測定できることを見出した。すなわち本発明は下記のとおりである。 Considering the workability of the measurement, it is better to use TG-DTA, but as mentioned above, when the calcium hydroxide content in the cement-based material exceeds a predetermined value, the dehydration reaction of calcium hydroxide may affect the measurement accuracy, which may result in a decrease in the measurement accuracy. Therefore, the present inventors have found that when the calcium hydroxide content exceeds a predetermined value, the CO2 content in the cement-based material can be accurately measured without being affected by the dehydration reaction of calcium hydroxide by measuring with coulometric titration. That is, the present invention is as follows.
［１］ セメント系材料中のＣＯ２含有率の測定方法であって、前記セメント系材料中の水酸化カルシウム含有率が１０質量％未満の場合、示差熱－熱重量同時分析法により前記ＣＯ２含有率を測定し、前記セメント系材料中の水酸化カルシウム含有率が１０質量％以上の場合、電量滴定法により前記ＣＯ２含有率を測定するＣＯ２含有率測定方法。
［２］ 前記示差熱－熱重量同時分析法で測定を行う際の測定温度範囲が５００℃～１０００℃である［１］に記載のＣＯ２含有率測定方法。
［３］ 前記示差熱－熱重量同時分析法で測定を行う際の測定温度範囲が５００℃～８５０℃である［２］に記載のＣＯ２含有率測定方法。
［４］ 前記示差熱－熱重量同時分析法で測定を行う際の昇温速度が５℃／分～３０℃／分であることを特徴とする［１］～［３］のいずれかに記載のＣＯ２含有率測定方法。
［５］ 前記示差熱－熱重量同時分析法で測定を行う際の測定雰囲気は窒素雰囲気である［１］～［４］のいずれかに記載のＣＯ２含有率測定方法。
［６］ 前記電量滴定法が、前記セメント系材料を含む測定試料を酸性とし、発生するＣＯ２ガスを吸収液に導入し、該吸収液の透過率を一定に保持するために必要な電気量からカーボン量を測定し、この測定値をＣＯ２量に換算してＣＯ２含有率を求める方法である［１］～［５］のいずれかに記載のＣＯ２含有率測定方法。
［７］ 前記セメント系材料を含む測定試料の粒度が６００μｍ以下である［６］に記載のＣＯ２含有率測定方法。
［８］ 前記セメント系材料を含む測定試料を酸性とするために、前記測定試料に塩酸濃度が０．１ｍｏｌ／Ｌ～１２ｍｏｌ／Ｌである塩酸を添加する、［６］又は［７］に記載のＣＯ２含有率測定方法。
[1] A method for measuring a CO2 content in a cement-based material, the method comprising: measuring the CO2 content by simultaneous differential thermal analysis and thermogravimetry when the calcium hydroxide content in the cement-based material is less than 10% by mass; and measuring the CO2 content by coulometric titration when the calcium hydroxide content in the cement-based material is 10% by mass or more.
[2] The method for measuring CO 2 content according to [1], wherein the measurement temperature range when measuring by the differential thermal-thermogravimetric simultaneous analysis method is 500 ° C to 1000 ° C.
[3] The method for measuring CO 2 content according to [2], wherein the measurement temperature range when measuring by the differential thermal-thermogravimetric simultaneous analysis method is 500 ° C to 850 ° C.
[4] The method for measuring CO 2 content according to any one of [1] to [3], characterized in that the heating rate when measuring by the differential thermal-thermogravimetric simultaneous analysis method is 5 ° C./min to 30 ° C./min.
[5] The method for measuring CO2 content according to any one of [1] to [4], wherein the measurement atmosphere when measuring by the differential thermal-thermogravimetric simultaneous analysis method is a nitrogen atmosphere.
[6] The method for measuring CO2 content according to any one of [1] to [5], wherein the coulometric titration method comprises acidifying a measurement sample containing the cement-based material, introducing the generated CO2 gas into an absorbing solution, measuring the amount of carbon from the amount of electricity required to maintain the transmittance of the absorbing solution constant, and converting this measurement value into the amount of CO2 to obtain the CO2 content.
[7] The CO 2 content measurement method according to [6], wherein the particle size of the measurement sample containing the cement-based material is 600 μm or less.
[8] In order to acidify the measurement sample containing the cement-based material, hydrochloric acid having a hydrochloric acid concentration of 0.1 mol / L to 12 mol / L is added to the measurement sample. The CO 2 content measurement method according to [6] or [7].
本発明によれば、水酸化カルシウムの脱水反応による影響が出ないように、セメント系材料中のＣＯ２含有率を精度よく測定できるＣＯ２含有率測定方法を提供することができる。 According to the present invention, it is possible to provide a CO 2 content measurement method capable of accurately measuring the CO 2 content in a cement-based material without being affected by the dehydration reaction of calcium hydroxide.
以下、本発明を詳細に説明する。
なお、本発明における部や％は、特に規定しない限り質量基準で示す。
また、本発明でいうセメントコンクリートとは、セメントペースト、セメントモルタル、及びコンクリートの総称である。
The present invention will be described in detail below.
In the present invention, parts and percentages are based on mass unless otherwise specified.
In addition, the cement concrete referred to in the present invention is a general term for cement paste, cement mortar, and concrete.
本発明に係るセメント系材料中のＣＯ２含有率の測定方法は、セメント系材料中の水酸化カルシウム含有率に応じて適切な測定方法を適用するものである。すなわち、セメント系材料中の水酸化カルシウム含有率が１０％未満の場合、示差熱－熱重量同時分析法によりＣＯ２含有率を測定する。また、セメント系材料中の水酸化カルシウム含有率が１０％以上の場合、電量滴定法によりＣＯ２含有率を測定する。なお、水酸化カルシウム含有率が１０％である場合は、水酸化カルシウムの脱水の影響を受けない安全側の評価方法であることを考慮して電量滴定法で測定を行うことが好ましい。 The method for measuring the CO2 content in a cement-based material according to the present invention applies an appropriate measurement method depending on the calcium hydroxide content in the cement-based material. That is, when the calcium hydroxide content in the cement-based material is less than 10%, the CO2 content is measured by simultaneous differential thermal-thermogravimetric analysis. When the calcium hydroxide content in the cement-based material is 10% or more, the CO2 content is measured by coulometric titration. When the calcium hydroxide content is 10%, it is preferable to measure by coulometric titration, considering that it is a safe evaluation method that is not affected by dehydration of calcium hydroxide.
既述のとおり、作業性を考慮すると、示差熱－熱重量同時分析法が好ましいが、セメント系材料中の水酸化カルシウム含有率が所定値以上となると、水酸化カルシウムの脱水反応による影響が出てしまい、測定精度が低くなることがある。一方で、電量滴定法によれば、水酸化カルシウム含有率によらずＣＯ２含有率を精度よく測定することができる。しかし、汎用性や作業性は示差熱－熱重量同時分析法に劣ってしまう。そこで、本発明では水酸化カルシウムの脱水反応による影響が出てしまう水酸化カルシウム含有率を特定し、その含有率により２つの測定方法を適切に選択することで、作業性が考慮されながらＣＯ２含有率が精度よく測定される。 As mentioned above, in consideration of workability, the differential thermal-thermogravimetric simultaneous analysis method is preferable, but when the calcium hydroxide content in the cement-based material is equal to or greater than a certain value, the dehydration reaction of calcium hydroxide may affect the measurement accuracy, which may result in a decrease in measurement accuracy. On the other hand, the coulometric titration method allows the CO 2 content to be measured accurately regardless of the calcium hydroxide content. However, the versatility and workability are inferior to the differential thermal-thermogravimetric simultaneous analysis method. Therefore, in the present invention, the calcium hydroxide content that is affected by the dehydration reaction of calcium hydroxide is specified, and the two measurement methods are appropriately selected according to the content, thereby allowing the CO 2 content to be measured accurately while taking workability into consideration.
ここで、セメント系材料中の水酸化カルシウム含有率は、示差熱－熱重量同時分析法における４００℃～５００℃の質量減少を水酸化カルシウムの脱水量とみなして、式１から定量することが好ましい。 Here, the calcium hydroxide content in the cement-based material is preferably quantified using Equation 1, with the mass loss at 400°C to 500°C in simultaneous differential thermal and thermogravimetric analysis regarded as the amount of dehydration of calcium hydroxide.
（式１）
水酸化カルシウム含有率（％）＝［ΔｍＣａ（ＯＨ）２／（ｍ０－ｍ１，０００）］×７４．１０／１８．０２×１００
ここに、ΔｍＣａ（ＯＨ）２：水酸化カルシウムの脱水量（ｍｇ）、ｍ０：測定に用いた試料量（ｍｇ）、ｍ１，０００：１,０００℃までの質量減少量（ｍｇ）
(Equation 1)
Calcium hydroxide content (%) = [ΔmCa(OH) 2 / (m0 - m1,000)] × 74.10 / 18.02 × 100
Here, ΔmCa(OH) 2 : amount of dehydration of calcium hydroxide (mg), m0: amount of sample used in measurement (mg), m1,000: amount of mass reduction up to 1,000° C. (mg)
また、測定対象となるセメント系材料としては、セメント、混和材、セメント組成物、セメントコンクリートが挙げられる。 Cementitious materials that can be measured include cement, admixtures, cement compositions, and cement concrete.
（セメント）
本発明でいうセメントとは、特に制限されないが、ポルトランドセメントを含有するものが好ましく、たとえば普通、早強、超早強、低熱、及び中庸熱等の各種ポルトランドセメントが挙げられる。また、これらポルトランドセメントに、高炉スラグ、フライアッシュ、又はシリカを混合した各種混合セメント、都市ゴミ焼却灰や下水汚泥焼却灰などを原料として製造された廃棄物利用セメント、いわゆるエコセメント（Ｒ）、及び石灰石粉末等を混合したフィラーセメント等が挙げられる。また、従来セメントに比べてＣＯ２排出量が少ないジオポリマーセメント、サルフォアルミネートセメント、石灰石焼成粘土セメント（ＬＣ３）も挙げられる。
(cement)
The cement in the present invention is not particularly limited, but preferably contains Portland cement, and examples thereof include various Portland cements such as normal, early strength, super early strength, low heat, and moderate heat. In addition, examples thereof include various mixed cements in which blast furnace slag, fly ash, or silica is mixed with these Portland cements, waste cements produced using municipal waste incineration ash and sewage sludge incineration ash as raw materials, so-called Ecocement (R), and filler cements in which limestone powder and the like are mixed. In addition, examples thereof include geopolymer cements, sulfoaluminate cements, and limestone calcined clay cements (LC3), which emit less CO2 than conventional cements.
（混和材）
次に本発明でいう混和材とは、砂や砂利などの骨材、高炉水砕スラグ微粉末、高炉徐冷スラグ粉末、石灰石微粉末、フライアッシュ、及びシリカフューム、火山灰など天然ポゾラン等の混和材料、膨張材、急硬材、ベントナイト等の粘土鉱物、並びに、ハイドロタルサイト等、通常のセメント系材料に用いられる公知公用の混和材が挙げられる。特に、γ－２ＣａＯ・ＳｉＯ２、３ＣａＯ・２ＳｉＯ２、α－ＣａＯ・ＳｉＯ２、及びカルシウムマグネシウムシリケートからなる群から選ばれる１種又は２種以上の非水硬性化合物を含むセメント混和材を混和させたセメント系材料、ならびに廃コンクリート、焼却灰など炭酸塩原料にＣＯ２を固定化させた炭酸塩のＣＯ２含有率測定で有効である。
(admixture)
Next, the admixture in the present invention includes aggregates such as sand and gravel, finely divided powder of granulated blast furnace slag, powder of slowly cooled blast furnace slag, finely divided powder of limestone, fly ash, and natural pozzolans such as silica fume and volcanic ash, expansive materials, quick hardening materials, clay minerals such as bentonite, and well-known admixtures used in ordinary cement-based materials such as hydrotalcite. In particular, it is effective for measuring the CO2 content of cement-based materials mixed with cement admixtures containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO.SiO2, 3CaO.2SiO2 , α- CaO.SiO2 , and calcium magnesium silicate, as well as carbonates obtained by fixing CO2 in carbonate raw materials such as waste concrete and incineration ash.
（１）示差熱－熱重量同時分析法
示差熱－熱重量同時分析法は、試料及び基準物質の温度をプログラムに従って変化させながら、試料の重量変化測定及び試料と基準物質の温度差を測定する示差熱測定を同時に行う手法で、ＴＧ－ＤＴＡ（法）とも表記される。
(1) Simultaneous Differential Thermal Analysis - Thermogravimetry Differential thermal analysis - thermogravimetry is a method in which the temperature of a sample and a reference substance are changed according to a program while simultaneously measuring the change in weight of the sample and differential thermal analysis, which measures the temperature difference between the sample and the reference substance. It is also referred to as TG-DTA (method).
示差熱－熱重量同時分析法でＣＯ２の含有率の測定を行う際の測定温度範囲は、炭酸カルシウムの脱炭酸温度と測定に要する時間の観点から、５００℃～１０００℃であることが好ましく、５００℃～８５０℃であることがより好ましい。ＣＯ２の含有率は式２から求まる。 The measurement temperature range when measuring the CO2 content by simultaneous differential thermal analysis and thermogravimetry is preferably 500°C to 1000°C, more preferably 500°C to 850°C, from the viewpoint of the decarbonation temperature of calcium carbonate and the time required for measurement. The CO2 content is calculated from Equation 2.
（式２）
ＣＯ２含有率（％）＝［ΔｍＣａＣＯ３／（ｍ０－ｍ１，０００）］×１００
ここに、ΔｍＣａＣＯ３：炭酸カルシウムの脱炭酸量（ｍｇ）、ｍ０：測定に用いた試料量（ｍｇ）、ｍ１，０００：１,０００℃までの質量減少量（ｍｇ）
(Equation 2)
CO 2 content (%) = [ΔmCaCO 3 /(m0-m1,000)]×100
Here, ΔmCaCO 3 : amount of decarbonated calcium carbonate (mg), m0: amount of sample used in measurement (mg), m1,000: amount of mass reduction up to 1,000° C. (mg)
昇温速度は、熱変化の温度、吸熱または発熱ピークの大きさ、ピークのシャープさ、測定に要する時間の観点から、５℃／分～３０℃／分であることが好ましく、５℃／分～１０℃／分であることが好ましい。 The heating rate is preferably 5°C/min to 30°C/min, more preferably 5°C/min to 10°C/min, from the viewpoints of the temperature of the thermal change, the magnitude of the endothermic or exothermic peak, the sharpness of the peak, and the time required for measurement.
測定雰囲気はＯ２、ＣＯ２などを含まない不活性ガスである必要があり、示差熱－熱重量同時分析法において一般的に用いられる窒素雰囲気であることが好ましい。 The measurement atmosphere must be an inert gas that does not contain O 2 , CO 2 or the like, and is preferably a nitrogen atmosphere that is generally used in simultaneous differential thermal analysis and thermogravimetry.
（２）電量滴定法
電量滴定法は、セメント系材料を含む測定試料を酸性とし、発生するＣＯ２ガスを吸収液に導入し、該吸収液の透過率を一定に保持するために必要な電気量からカーボン量を測定し、この測定値をＣＯ２量に換算してＣＯ２含有率を求める方法である。
(2) Coulometric titration In the coulometric titration, a measurement sample containing a cementitious material is acidified, the generated CO2 gas is introduced into an absorbing solution, and the amount of carbon is measured from the amount of electricity required to maintain the transmittance of the absorbing solution constant. This measurement value is converted into the amount of CO2 to determine the CO2 content.
セメント系材料を含む測定試料を酸性とするために、測定試料に塩酸濃度が０．１ｍｏｌ／Ｌ～１２ｍｏｌ／Ｌである塩酸を添加することが好ましく、２ｍｏｌ／Ｌ～１２ｍｏｌ／Ｌであることがより好ましい。当該塩酸濃度の塩酸によれば、セメント系材料中の炭酸塩を十分に溶解し、ＣＯ２ガスを発生させることができる。 In order to acidify a measurement sample containing a cement-based material, it is preferable to add hydrochloric acid having a hydrochloric acid concentration of 0.1 mol/L to 12 mol/L, and more preferably 2 mol/L to 12 mol/L, to the measurement sample. Hydrochloric acid with this concentration can sufficiently dissolve carbonates in the cement-based material and generate CO2 gas.
電量滴定法は、例えば、クーロメーターにて行うことが好ましい。クーロメーターは、抽出装置で測定試料から二酸化炭素を取り出し、電量滴定によってＣＯ２量を測定する装置である。 The coulometric titration is preferably carried out, for example, with a coulometer, which is a device that extracts carbon dioxide from a measurement sample with an extraction device and measures the amount of CO2 by coulometric titration.
示差熱－熱重量同時分析法及び電量滴定法のいずれにおいても、セメント系材料を含む測定試料の粒度は、塩酸による溶解時間や十分に溶解することが可能な粒子径の観点から、６００μｍ以下であることが好ましく、１μｍ～２００μｍであることがより好ましい。粒度は、ふるいにより測定することができる。 In both simultaneous differential thermal analysis and coulometric titration, the particle size of the measurement sample containing the cement-based material is preferably 600 μm or less, and more preferably 1 μm to 200 μm, from the viewpoint of the dissolution time in hydrochloric acid and the particle size that can be sufficiently dissolved. The particle size can be measured using a sieve.
（使用材料）
セメント：普通ポルトランドセメント、市販品
混和材Ａ：ＣａＯ／ＳｉＯ２のモル比２．０の配合で製造したダイカルシウムシリケート
混和材Ｂ：ＪＩＳ Ｒ ９００１に規定された消石灰特号に相当する消石灰、市販品
水：水道水
(Materials used)
Cement: Ordinary Portland cement, Commercial admixture A: Dicalcium silicate admixture manufactured with a molar ratio of CaO/ SiO2 of 2.0 B: Slaked lime corresponding to the special slaked lime specified in JIS R 9001, Commercial water: Tap water
（セメント系材料の作製）
表１に示す配合でＪＩＳ Ｒ５２０１「セメントの物理試験方法」に準じてセメントペーストを作製した。水セメント比（Ｗ／Ｃ）を４８％とし、混和材Ａ及び混和材Ｂをセメント１００部に対し０、２０、５０部添加した。
(Preparation of cement-based materials)
Cement pastes were prepared according to JIS R5201 "Physical Testing Methods for Cement" with the composition shown in Table 1. The water-cement ratio (W/C) was 48%, and 0, 20, and 50 parts of admixture A and admixture B were added to 100 parts of cement.
作製した各セメントペーストからなる５×５×５ｃｍの角柱供試体をそれぞれ作製した。打設後、材齢１日で脱型した供試体の打設面の裏面を残し、他の５面をアルミテープでシールした供試体を用意した。脱型直後の供試体中心部から採取した試料に加え、アルミテープでシールした供試体に炭酸化養生（環境温度：２０℃、相対湿度：６０％、５％ＣＯ２）を７日（炭酸化期間７日）、２８日（炭酸化期間２８日）施した。
炭酸化養生しない供試体（炭酸化期間０日）及び上記炭酸化養生した供試体について、暴露面から１０ｍｍ厚（試料採取場所：暴露面）と、その反対側の面（試料採取場所：裏面）から１０ｍｍ厚、暴露面から１０ｍｍ厚及びその反対面から１０ｍｍ厚を除いた部分（試料採取場所：中心部）をタガネと金槌を用いて採取することで、水酸化カルシウムの含有率が１０％未満となるセメント系材料を７サンプル（水酸化カルシウムの含有率４．２％～９．６％、平均含有率６．７６％）、及び、水酸化カルシウムの含有率が１０％以上となるセメント系材料を１８サンプル（水酸化カルシウムの含有率１１．２％～３４．４％、平均含有率２０．８２％）用意した。採取した試料を粉砕して粒度が１５０μｍ以下のセメント系材料とし、これに対してアセトンによる水和停止と４０℃乾燥を行い、ＴＧ－ＤＴＡ法及び電量滴定法によりＣＯ２含有率を下記のようにして測定した。
Each cement paste was used to prepare a 5 x 5 x 5 cm rectangular column specimen. After casting, the specimen was demolded after 1 day of age, and the back side of the poured surface was left, while the other five surfaces were sealed with aluminum tape to prepare a specimen. In addition to the sample taken from the center of the specimen immediately after demolding, the specimen sealed with aluminum tape was subjected to carbonation curing (ambient temperature: 20°C, relative humidity: 60%, 5% CO2 ) for 7 days (carbonation period 7 days) and 28 days (carbonation period 28 days).
For the test specimens not subjected to carbonation curing (carbonation period 0 days) and the test specimens subjected to the carbonation curing, samples were taken using a chisel and a hammer from a 10 mm thickness from the exposed surface (sample collection location: exposed surface), a 10 mm thickness from the opposite surface (sample collection location: back surface), and a portion excluding a 10 mm thickness from the exposed surface and a 10 mm thickness from the opposite surface (sample collection location: center portion). In this way, 7 samples of cement-based materials with a calcium hydroxide content of less than 10% (calcium hydroxide content 4.2% to 9.6%, average content 6.76%) and 18 samples of cement-based materials with a calcium hydroxide content of 10% or more (calcium hydroxide content 11.2% to 34.4%, average content 20.82%) were prepared. The collected samples were pulverized to obtain cement-based materials with particle sizes of 150 μm or less, and the hydration of the materials was stopped with acetone and dried at 40°C. The CO2 content was measured by the TG-DTA method and the coulometric titration method as described below.
（１）ＴＧ－ＤＴＡ法によるＣＯ２含有率測定
ＴＧ－ＤＴＡ（ＮＥＴＺＳＣＨ ＪＡＰＡＮ株式会社製、ＴＧ－ＤＴＡ２０００ＳＡ型）を使用し、測定は窒素雰囲気下において昇温速度１０℃／分で１０００℃まで昇温を行った。得られたＴＧ－ＤＴＡ曲線を基に、５００℃～８５０℃の範囲におけるＣａＣＯ３由来のＣＯ２量に相当する質量減少量を求め、その差分から各セメント系材料のＣＯ２含有率を求めた。表１に結果を示す。
(1) Measurement of CO2 content by TG-DTA method TG-DTA (TG-DTA2000SA type, manufactured by NETZSCH JAPAN Co., Ltd.) was used, and the temperature was raised to 1000 ° C. at a heating rate of 10 ° C. / min in a nitrogen atmosphere. Based on the obtained TG-DTA curve, the mass loss equivalent to the amount of CO2 derived from CaCO3 in the range of 500 ° C. to 850 ° C. was calculated, and the CO2 content of each cement-based material was calculated from the difference. The results are shown in Table 1.
（２）電量滴定法によるＣＯ２含有率測定
クーロメーター（日本アンス株式会社製、２０００Ｓ－ＣＡＴ型）を使用し、三角フラスコに入れた各セメント系材料に塩酸（塩酸濃度：３ｍｏｌ／Ｌ）を加えて、スターラーで攪拌、発生するＣＯ２ガスを窒素で吸収液へ導入させ、吸収液の透過率を一定保持に要する電気量からカーボン量を測定し、ＣＯ２含有率に換算した。表１に結果を示す。
(2) Measurement of CO2 content by coulometric titration Using a coulometer (2000S-CAT model, manufactured by Nippon Ans Co., Ltd.), hydrochloric acid (hydrochloric acid concentration: 3 mol/L) was added to each cement-based material placed in an Erlenmeyer flask, stirred with a stirrer, and the generated CO2 gas was introduced into the absorbing solution with nitrogen. The amount of carbon was measured from the amount of electricity required to maintain the transmittance of the absorbing solution at a constant level, and converted into the CO2 content. The results are shown in Table 1.
図１に水酸化カルシウムの含有率が１０％未満となるセメント系材料（７サンプル）のＴＧ－ＤＴＡ法及び電量滴定法の測定結果を示す。水酸化カルシウムの含有率が１０％未満の場合は、ＴＧ－ＤＴＡ法及び電量滴定法の測定結果は一致しており、いずれも精度よくＣＯ２含有率を測定できた。 Figure 1 shows the results of measurements of TG-DTA and coulometric titration for cement-based materials (7 samples) with a calcium hydroxide content of less than 10%. When the calcium hydroxide content was less than 10%, the results of the TG-DTA and coulometric titration methods were consistent, and both methods were able to measure the CO2 content with high accuracy.
図２に水酸化カルシウムの含有率が１０％以上となるセメント系材料（１８サンプル）のＴＧ－ＤＴＡ法及び電量滴定法の測定結果を示す。水酸化カルシウムの含有率が１０％以上の場合は、ＴＧ－ＤＴＡ法及び電量滴定法の測定結果は一致しない場合が多く存在した。ＴＧ－ＤＴＡ法ではその原理上、水酸化カルシウムの脱水反応による影響が出てしまい、測定精度が低くなる。一方で、電量滴定法は水酸化カルシウムの脱水反応による影響はない。つまり、測定結果の不一致は、ＴＧ－ＤＴＡ法の測定精度によるものといえる。したがって、水酸化カルシウムの含有率が１０％以上の場合は、電量滴定法を採用する方が精度よくＣＯ２含有率を測定できるといえる。 Figure 2 shows the measurement results of the TG-DTA method and the coulometric titration method for cement-based materials (18 samples) with a calcium hydroxide content of 10% or more. When the calcium hydroxide content is 10% or more, the measurement results of the TG-DTA method and the coulometric titration method often do not match. In principle, the TG-DTA method is affected by the dehydration reaction of calcium hydroxide, which reduces the measurement accuracy. On the other hand, the coulometric titration method is not affected by the dehydration reaction of calcium hydroxide. In other words, the inconsistency in the measurement results can be said to be due to the measurement accuracy of the TG-DTA method. Therefore, when the calcium hydroxide content is 10% or more, it can be said that the CO2 content can be measured more accurately by adopting the coulometric titration method.
以上から、水酸化カルシウムの脱水反応による影響が出ないように、セメント系材料中のＣＯ２含有率を精度よく測定できるＣＯ２含有率を測定するには、セメント系材料中の水酸化カルシウム含有率が１０％未満の場合、作業性の点から示差熱－熱重量同時分析法によりＣＯ２含有率を測定し、セメント系材料中の水酸化カルシウム含有率が１０％以上の場合は良好な精度の点から電量滴定法によりＣＯ２含有率を測定することが適切といえる。 From the above, in order to measure the CO2 content in a cement-based material with high accuracy without being affected by the dehydration reaction of calcium hydroxide, when the calcium hydroxide content in the cement-based material is less than 10%, it is appropriate to measure the CO2 content by differential thermal-thermogravimetric simultaneous analysis from the viewpoint of workability, and when the calcium hydroxide content in the cement-based material is 10% or more, it is appropriate to measure the CO2 content by coulometric titration from the viewpoint of good accuracy.
本発明は、土木・建築分野等で、種々のセメント系材料のＣＯ２含有率を測定する際に幅広く使用することができる。
INDUSTRIAL APPLICABILITY The present invention can be widely used in the fields of civil engineering and construction, etc., when measuring the CO2 content of various cement-based materials.
Claims (8)
前記セメント系材料中の水酸化カルシウム含有率が１０質量％未満の場合、示差熱－熱重量同時分析法により前記ＣＯ２含有率を測定し、
前記セメント系材料中の水酸化カルシウム含有率が１０質量％以上の場合、電量滴定法により前記ＣＯ２含有率を測定するＣＯ２含有率測定方法。 A method for measuring the CO2 content in a cement-based material, comprising:
When the calcium hydroxide content in the cement-based material is less than 10% by mass, the CO2 content is measured by simultaneous differential thermal analysis and thermogravimetry;
A CO2 content measurement method, in which, when the calcium hydroxide content in the cement-based material is 10 mass% or more, the CO2 content is measured by coulometric titration.
The CO 2 content measurement method according to claim 6 or 7, wherein hydrochloric acid having a hydrochloric acid concentration of 0.1 mol / L to 12 mol / L is added to the measurement sample containing the cement-based material to make the measurement sample acidic.
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| JP2000193658A (en) | 1998-10-22 | 2000-07-14 | Sumitomo Metal Mining Co Ltd | Quantitative determination and evaluation method of deterioration of water vapor cure light-weight bubble concrete |
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| JP2016017025A (en) | 2014-07-11 | 2016-02-01 | デンカ株式会社 | Cement composition and method for producing the same |
| JP2020152631A (en) | 2019-03-13 | 2020-09-24 | 太平洋セメント株式会社 | Method for producing cement powder composition |
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| JP2000193658A (en) | 1998-10-22 | 2000-07-14 | Sumitomo Metal Mining Co Ltd | Quantitative determination and evaluation method of deterioration of water vapor cure light-weight bubble concrete |
| JP2001316113A (en) | 2000-05-01 | 2001-11-13 | Denki Kagaku Kogyo Kk | Alkali metal aluminate and its manufacturing method |
| US20150168369A1 (en) | 2013-03-05 | 2015-06-18 | Korea Institute Of Construction Technology | Method for evaluating semi-quantitatively of concrete carbonization and evaluating apparatus using the same |
| JP2016017025A (en) | 2014-07-11 | 2016-02-01 | デンカ株式会社 | Cement composition and method for producing the same |
| JP2020152631A (en) | 2019-03-13 | 2020-09-24 | 太平洋セメント株式会社 | Method for producing cement powder composition |
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