著者

Zhenzhen Wang Abudushalamu Aili Masayo Minami Ippei Maruyama

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.21, no.11, pp.934-940, 2023-11-22 (Released:2023-11-22)

参考文献数

34

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Capturing atmospheric CO2 into cement-based materials is a way to set off the CO2 emissions of concrete production. This study proposes an experimental method to track the origin of cement paste that fixes CO2 directly from the air under natural conditions. By exposing powders of well-hydrated cement paste to air, carbonated cement paste powders are obtained with different carbonation degrees. The inorganic carbon of these carbonated samples is extracted by dissolution in phosphoric acid, and the isotopic characteristics related to 13C and 14C are measured. The experimental results show that the 14C value of carbonated cement paste can be used as an indicator for tracing the origin of carbon.

著者

Osamu Kontani Takashi Okayasu Keishi Kawasumi Shunsuke Ishikawa Hiroshi Masaki Norihiko Tanaka Yasuyuki Goto Shinichi Ishioka

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.20, no.7, pp.444-483, 2022-07-27 (Released:2022-07-27)

参考文献数

46

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The Fukushima Daiichi Nuclear Power Plant lost its core cooling function due to the massive tsunami generated by the 2011 off the Pacific coast of Tohoku Earthquake, which caused core meltdown, resulting in high temperature inside the containment vessel and exposing the RPV pedestal, a reinforced concrete structure, to an unusually high temperature environment. After the earthquake, water was poured into the containment vessel to cool the molten core, and the con-crete structure was gradually cooled in the process. Since it will take at least 40 years to remove the fuel from the core, the integrity of the RPV pedestal is a major concern for the decommissioning of the Fukushima Daiichi Nuclear Power Plant. In order to assess the long-term integrity of the RPV pedestal, a horizontal loading test was conducted using a 1/6 scaled model of the RPV pedestal of Unit 1 considering the effect of the high temperature heating and subsequent wet conditions. And then, the static stress analysis of the RPV pedestal was performed considering the degradation phenomena revealed by the experiments. As a result, it was confirmed that the RPV pedestal of Unit 1 would be structurally sound for 40 years against the current design basis earthquake even if the material degradation due to severe accident and aging was considered.

著者

川人 麻紀夫 久保 智彦 大郷 貴之 図司 英明

出版者

Japan Concrete Institute

雑誌

コンクリート工学 = Concrete journal (ISSN:03871061)

巻号頁・発行日

vol.51, no.11, pp.905-910, 2013-11-01

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東北本線浦和駅周辺高架化工事では,湘南新宿ライン等の浦和駅停車を目的とした改良工事や乗降場新設がプロジェクトの一環として進められてきた。東北貨物線の改良工事においては,駅部アプローチ区間における既設高架橋の改築や補強工事,さらに乗降場新設においては,営業線供用下で既設高架橋を仮受し,既設高架橋の柱や梁を撤去・改築する工事など,これらの計画,設計ならびに施工は難易度の高いものであった。本稿では,湘南新宿ライン等浦和駅使用開始に向けて行われた既設高架橋の改築,補強ならびに仮受工事について報告する。

著者

Daisuke Kambayashi Hiroshi Sasano Shohei Sawada Kiyoteru Suzuki Ippei Maruyama

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.18, no.10, pp.618-632, 2020-10-27 (Released:2020-10-27)

参考文献数

29

被引用文献数

8

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In nuclear power plants, concretes used for biological shielding walls are exposed to radiation such as neutrons and gamma rays over the long-term operation of the plant. Previous studies have reported that neutron irradiation causes aggregate expansion due to the metamictization of quartz and feldspar leading to reduced density and a loss of the compressive strength and Young' s modulus of the concrete. Therefore, it is crucial to understand the current state of a concrete biological shield (CBS) and predict its future soundness. In this study, a rigid-body spring model, which can easily evaluate fracture behavior by using springs between each element, is used to conduct numerical analyses on a CBS. A three-phase (mortar, aggregate, and interfacial transition zone) model of a 2000 mm thick CBS is used to investigate the varying deformation responses depending on the presence or absence of reinforcing bars (rebar), creep, and an inner steel plate with five types of analyses, i.e. analysis to understand the impacts of temperature distribution, re-inforcement bars, an internal steel plate, and creep of mortar. The results show that cracking and delamination occur inside the CBS, resulting in a lack of cracking on the outside. They also show that the cracks are reduced by rebar and creep, resulting in cracks extending from the innermost edge to a depth of approximately 150 mm.

著者

Hiroshi Sasano Ippei Maruyama Shohei Sawada Takahiro Ohkubo Kenta Murakami Kiyoteru Suzuki

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.18, no.10, pp.648-677, 2020-10-28 (Released:2020-10-28)

参考文献数

80

被引用文献数

19

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To evaluate the radiation-induced degradation of concrete, a rigid-body spring network model is introduced that takes into account the three phases in concrete: mortar, aggregate, and the interfacial transition zone. The proposed model enables evaluation of the change in the physical properties of concrete affected by aggregate expansion under the free restraint condition. Good agreement with previous experimental data is found for the linear expansion of the concrete specimen and the compressive strength, Young’s modulus, and splitting tensile strength. Based on the numerical results, it is concluded that, to reproduce the physical property changes in concrete, the expansion of mortar due to the radiation-induced expansion of fine aggregate and/or creep behavior must be considered. In addition, it is clarified that an isolated expansion of mortar with a lack of expansion in the coarse aggregate also degrades the concrete and, consequently, analysis of the type of aggregate used is critical for predicting the properties of concrete under neutron irradiation. Furthermore, the impact of inhomogeneous expansion of rock-forming minerals in coarse aggregates on physical property changes is studied, showing that such a partial expansion in the aggregates and the resultant cracks in aggregates greatly influences the reduction of the Young’s modulus, with minimal impact on the reduction of compressive strength. The proposed model can be used to evaluate concrete degradation due to radiation-induced volumetric expansion of aggregate caused by the metamictization of rock-forming minerals.

著者

早川 智浩 富井 孝喜 青木 茂 古城 誠

出版者

Japan Concrete Institute

雑誌

コンクリート工学 = Concrete journal (ISSN:03871061)

巻号頁・発行日

vol.50, no.4, pp.338-344, 2012-04-01

参考文献数

13

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上面増厚工法の増厚材に高流動高じん性モルタルを用いた新しい上面増厚工法(タフスラブ・ラピッド工法)を開発した。本工法は,従来工法である鋼繊維補強コンクリートの課題であった機械設備のコンパクト化,充てん性および一体性の確保,薄層施工,鋼繊維による防水層への影響を解決した。本稿では,新しく開発した増厚材の性質およびその増厚材を用いて実施した施工性能確認試験とその結果について述べる。

著者

岩島 保 波田 匡司 坂本 真 柳井 修司

出版者

Japan Concrete Institute

雑誌

コンクリート工学 = Concrete journal (ISSN:03871061)

巻号頁・発行日

vol.51, no.8, pp.641-647, 2013-08-01

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新名神高速道路に建設された川下川橋は,神戸市と宝塚市を跨ぐ急峻な谷間に架かるPRC 3径間連続ラーメン箱桁橋であり,橋脚高95m,最大張出し架設長110mを有する国内最大規模のコンクリート橋である。本橋は,高強度鉄筋を使用した大口径深礎,高強度鉄筋と高強度コンクリートを使用した中空断面の高橋脚,桁高12mのコンクリートウェブを有する広幅員かつ長支間の主桁など,特徴的な構造を有する。本稿では,これらの部材に適用したコンクリートの特徴とその施工方法ならびに施工結果について報告する。

著者

河原木 忍 宮本 誠 今野 繁 伊藤 和彦

出版者

Japan Concrete Institute

雑誌

コンクリート工学 = Concrete journal (ISSN:03871061)

巻号頁・発行日

vol.50, no.1, pp.69-73, 2012-01-01

著者

José Granja Renan Rocha Ribeiro Thomas Russo Rodrigo Lameiras Miguel Azenha

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.21, no.10, pp.803-820, 2023-10-26 (Released:2023-10-26)

参考文献数

59

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The influence of temperature on the hydration of cementitious materials has been traditionally modelled using the maturity concept and Arrhenius law. This approach yields a single material property, called apparent activation energy (Ea), that describes the whole temperature dependence. Determining Ea experimentally has sparked controversy, such as whether the different properties (e.g., compressive strength, tensile strength, E-modulus) exhibit different Ea, whether a single Ea value exists for the entire hydration process, or whether cement paste and concrete possess the same Ea. Furthermore, studies measuring Ea from elastic modulus measurements are truly scarce, likely due to experimental challenges with measuring this property at early-ages. This work investigated the influence of temperature on the elastic modulus evolution of cement paste and concrete. A single mix for each material was tested with the EMM-ARM (Elasticity Modulus Measurement through Ambient Response Method) methodology under three different isothermal conditions. The resulting elastic modulus evolution curves were used to derive Ea evolution curves from two traditional computation methods: the ‘speed’ method and the ‘derivative of speed’ method. Results showed that the elastic modulus evolution of both materials initially presented a constant Ea, independent of temperature and hydration development as preconized by the classical Arrhenius law. However, as hydration progressed to later stages, the activation energy exhibited evident dependencies on both temperature and hydration levels. Cement paste and concrete consistently exhibited different Ea values throughout hydration, with concrete having higher values. The use of the Ea curves to superimpose the different experimental elastic modulus evolution curves by means of the equivalent age concept led to near-perfect superpositions, strengthening the validity of this concept when applied to elastic modulus evolution.

著者

Ngoc Kien Bui Ryo Kurihara Wei Wang Manabu Kanematsu Hikotsugu Hyodo Miku Takano Hiroshi Hirao Takafumi Noguchi Ippei Maruyama

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.21, no.3, pp.166-188, 2023-03-30 (Released:2023-03-30)

参考文献数

105

被引用文献数

1

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This study investigates the wet carbonation of concrete fines with CO2 and natural air gas bubbling in a carbonation system at low temperatures. After the air- and CO2-wet carbonations, the properties of a solution and hydrated cement paste powder are determined. In the air and CO2-wet carbonations, more Ca is extracted into the solution at a low temperature of 5°C. This high Ca concentration in the solution through air-wet carbonation primarily originates from the portlandite and unhydrated phases of the cement paste. Even in solutions with high pH values, the rehydration process and C–S–H decomposition occur simultaneously in air-wet carbonation. Moreover, CO2-wet carbonation indicates that the decalcification of C–S–H occurs rapidly, even in the presence of portlandite. Air-wet carbonation presents a potential method for the direct air capture of CO2 using concrete waste fines in a short period.

著者

Yuliia Khmurovska Petr Štemberk

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.19, no.6, pp.668-686, 2021-06-24 (Released:2021-06-24)

参考文献数

40

被引用文献数

6

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This paper presents a catalogue of possible radiation-induced damage of rock aggregates, which was compiled using the relevant literature and confirmed numerically. The catalogue describes two common and six specific cases of rock aggregate damage. Additionally, the catalogue is supported by a validated numerical model, which is based on Rigid-Body Spring Model. The detailed numerical analysis and the result description of all the cases shown in the catalogue are presented in this paper. The main dependencies are also discussed and the related conclusions are drawn, of which the most important are that the damage of the rock can be delayed and increased rapidly after the delay; even a small amount (1%) of a highly expansive mineral leads to a significant reduction of mechanical properties of the rock; and a partial recovery of the elastic modulus of the rocks is possible even for significantly damaged rocks. It is believed that this paper will help to predict the radiation-induced degradation of rock aggregates as well as support the future development of related analytical models.

著者

Haonan Liu Zhao Xie Ruixue Yu Ning Zhang

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.20, no.3, pp.127-138, 2022-03-11 (Released:2022-03-11)

参考文献数

50

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The pore structure of concrete is highly complex and random. Fractal theory is used to describe the characteristics of its pore structure. Ds (surface fractal dimension) is commonly used to characterize the surface roughness of the pores. However, the existing Ds model is limited to two dimensions and there are unreasonable assumptions about the shape of the pores and the method of measuring pores is not applicable. Therefore, this paper proposes a three-dimensional (3-D) model for calculating the Ds. The new parameter Dss represents the chaotic degree of element morphology in the 3-D pore system. When Dss=0, the pore morphology tends to be the same. The larger Dss value is, the more divergent and diversified pore morphology is. The specimens in two states of standard curing and high temperature drying were prepared and the pore structure parameters of the specimens were calculated by combining CT scanning, Deep Learning and 3-D reconstruction. By comparing Dss and Dv (volume fractal dimension) and other parameters, it is found the 3-D pore system of concrete is more chaotic and becomes more complex under the effect of high temperature drying. It also confirms the reliability of the 3-D fractal dimension model proposed in this paper.

著者

Hadiza Mohammed Inés Garcia-Lodeiro Hajime Kinoshita

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.19, no.12, pp.1296-1308, 2021-12-23 (Released:2021-12-23)

参考文献数

28

被引用文献数

1

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Large quantities of aqueous secondary waste are generated from the processing of contaminated water after the nu-clear accident in Japan. Cementation of these wastes is challenging because their significant radioactivity may cause the radiolysis of water contents in cement, posing a risk of hydrogen gas generation. The application of calcium aluminate cement modified with phosphates (CAP), as an alternative cementing system, is interesting because this system is based on acid-base reaction, and its water content can be reduced by mild heating once the system is mixed. The present study focused in the use of Secar 71, a calcium aluminate cement with a high alumina and low silica compositions, and its effects of on the production of CAP system at elevated temperatures. The modification of Secar 71 with phosphates was successful, and the reduction of water content by about 35% was achieved in the CAP system containing SrCl2 after curing the system at 80°C for 7 days. The micro cracks, typically observed in the CAP system cured at lower temperature, was significantly reduced by curing at 80°C. The obtained results show a potential of Secar 71 to prepare CAP for cementation of aqueous secondary wastes.

著者

Takeru Kanazawa Takuro Nakamura Junichi Sakaguchi Kazuhiro Kawaguchi

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.20, no.1, pp.18-29, 2022-01-25 (Released:2022-01-25)

参考文献数

29

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This study presents a kinematic model for flexural analysis of RC beams and columns subjected to freeze-thaw action based on upper bound theorem. The developed model enables analytical derivation of the contribution of damaged concrete when actual deterioration profile is idealized as an assemblage of undamaged and damaged zones based on freeze-thaw depth obtained from concrete core specimens. The accuracy of the analysis is verified by comparing its predictions with available 21 RC columns and beams failing in flexure after freeze-thaw exposure. The predicted results show good agreement with the test results within error of 6% on average. Thereafter, the developed analysis predicts the ultimate moment capacity of a RC beam, which was taken from an existing bridge slab replaced because of the combined effect of frost damage and fatigue. Results demonstrate that the present analysis could support a rational decision-making regarding the need for repair or rehabilitation. This paper is the English translation from the authors’ previous work [Kanazawa, T., Nakamura, T., Sakaguchi, J. and Kawaguchi, K., (2021). “Flexural analysis combined with freeze–thaw depth for RC linear members.” Journal of Japan Society of Civil Engineers, Ser. E2 (Materials and Concrete Structures), 77(4), 177-186. (in Japanese)].

著者

寺西 浩司 江口 清 中込 昭 今村 輝武

出版者

Japan Concrete Institute

雑誌

コンクリート工学

巻号頁・発行日

vol.32, no.4, pp.54-63, 1994

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高層部の柱を充?形鋼管コンクリート構造としたホテルが, 福井県において2件施工された。グランディア芳泉ホテルでは, 地上12階のうち5階以上の8層, 一方のポートヒル芳泉ホテルでは, 地上8階のうち3階以上の6層の柱にこの構造形式が適用されている。本物件の施工の特徴は, 凝集状シリカフュームを混入した充?コンクリートを開発し, 地上のポンプから直接, 鋼管内部へ圧入した点である。このような工法を確立するために, 充?コンクリートの調合を検討し, 実大スケールの鋼管柱を用いた圧入実験を実施している。本報告では, これらの事前検討結果と, 施工時のコンクリートの製造・管理方法およびコンクリートの充?結果を紹介する。

著者

アルカンタラ プリモアラン 今井 弘

出版者

Japan Concrete Institute

雑誌

コンクリート工学論文集 (ISSN:13404733)

巻号頁・発行日

vol.10, no.2, pp.13-28, 1999

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A new approach in the classification of the resulting failure mode, whether shear, bond splitting or flexure, for reinforced concrete columns is presented. Particular emphasis is placed on the analysis of the strain distribution in the main reinforcement based on the truss and arch model theory. Failure mode prediction from the proposed alternative method is compared with results from several series of column experiments. The proposed method is shown to provide a high level of precision in classifying failure modes with the proper consideration of the presence of inner rows of main bars and the effect of axial loading.

著者

北村 俊男 村井 義則 磯田 和彦

出版者

Japan Concrete Institute

雑誌

コンクリート工学 (ISSN:03871061)

巻号頁・発行日

vol.28, no.3, pp.107-111, 1990

著者

富岡 紘

出版者

Japan Concrete Institute

雑誌

コンクリート工学 (ISSN:03871061)

巻号頁・発行日

vol.23, no.8, pp.50-57, 1985

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本四連絡橋亀浦高架橋は, 神戸・鳴門ルート大鳴門橋に接続する四国側の長大PC道路橋である。 本橋は暫定4車線で施工されているため, 全幅が18.25mと比較的広く, 2径間連続箱げた橋および3径問連続箱げた橋2連からなる。2径間部はフレシネー工法, 3径間部はディビダーク工法によりそれぞれ施工され, そのうち道路および漁港施設と交差する部分の側径間部の施工にあたっては, 仮支柱を構築してワーゲン施工を行った。 本稿は, 3径間部の上部工の施工について述べる。

著者

Ippei Maruyama Wataru Kotaka Bui Ngoc Kien Ryo Kurihara Manabu Kanematsu Hikotsugu Hyodo Hiroshi Hirao Ryoma Kitagaki Masaki Tamura Masato Tsujino Satoshi Fujimoto Takafumi Noguchi

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.19, no.10, pp.1052-1060, 2021-10-08 (Released:2021-10-08)

参考文献数

20

被引用文献数

14

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Countermeasures against carbon dioxide emissions are a concern in the construction field as well as in society. To solve this problem, a concept for new calcium carbonate concrete is proposed, and this concept is validated experimentally. In the proposed concept, calcium carbonate comprising Ca originating from demolished concrete or other Ca-containing industrial wastes and HCO3- from CO2 gas collected from the air or emitted by industrial plants acts as a binder for aggregates, which can be natural rocks or crushed demolished concrete. This short paper describes the details of the process of making calcium carbonate concrete and discusses future perspectives.

著者

斎藤 二郎 芳賀 孝成

出版者

Japan Concrete Institute

雑誌

コンクリート工学 (ISSN:03871061)

巻号頁・発行日

vol.20, no.2, pp.14-21, 1982

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地下連続壁工法は, 海外より我が国に導入されて以来, 主に土留壁の施工に利用されてきたが, 今日, 利用範囲は拡大し, 施工実績もますます増大している。本稿では, 地下連続壁の発展の経緯を顧みた後, 大規模土留壁, 構造物の基礎, 円形立坑などへの今後の利用の動向を述べる。また, 安定液中へのコンクリート打設法, プレストレスを導入する工法, プレキャスト版を用いる工法などの研究・開発の動向も紹介する。