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受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

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受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

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受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

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受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

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受賞区分：出版社・新聞社・財団等の賞  受賞国：日本国

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受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

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受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

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受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

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受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

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受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

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受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Construction and Building Materials  

The early age expansion of cement paste/concrete due to expansive additives (EA) has a significant impact on the microstructure and early-age mechanical properties of cement paste and concrete. Moreover, external restraints owing to reinforcement and supports play a crucial role in reducing concrete expansion and may also affect the microstructure. In this study, a measurement technique to monitor the development of early age elastic modulus of paste (from casting to hardened stage) focusing on the effect of external restraints was established. The influence of external restraint on the microstructure and elastic modulus was examined using the Elastic Modulus Measurement Ambient Response Method (EMM-ARM) and mercury intrusion porosimetry (MIP). This study also focuses on the effect of water-to-binder (w/b) ratios and amount of EA on the early-age mechanical properties of cement paste. The experimental results revealed that under unrestrained conditions, the addition of EA caused the microstructure of the paste to become porous, resulting in a decrease in mechanical properties. Conversely, under restrained conditions, the elastic modulus of the paste with EA and the level of porosity were comparable to the paste without EA. These findings have significant implications for the utilisation of EA in concrete construction and provide potential avenues for enhancing the durability and performance of concrete structures.

DOI： 10.1016/j.conbuildmat.2024.135655

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：セメント協会  

DOI： https://doi.org/10.14250/cement.77.44

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：セメント協会  

DOI： https://doi.org/10.14250/cement.77.222

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：セメント協会  

DOI： https://doi.org/10.14250/cement.77.62

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 セメント協会  

<p>本論文は、¹H-NMR Relaxometryを炭酸化過程に適応し、炭酸化によって変化する結合水量、自由水量および全体の水分量の変動を、炭酸化進行と共に分析した。その結果、20℃、85％RH環境では、水酸化カルシウムとC-S-Hの炭酸化が確認された。横緩和時間T₂の測定から、Interlayer及びGel poreの横緩和時間が炭酸化により長くなることを確認した。熱重量/示差熱分析を用いて算出した水酸化カルシウムの炭酸化度とSolid echo法を用いて測定した結合水の変化量には負の相関関係があり、炭酸化によって水酸化カルシウム中の結合水が自由水へと変化したことを確認した。自由水について、炭酸化初期におけるC-S-H中のGel poreの水分量は増加し、Interlayerの水分量は減少した。</p>

DOI： 10.14250/cement.77.44

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 セメント協会  

<p>本研究ではCalcium aluminate silicate hydrate（C-A-S-H）の炭酸化前後の構造変化と相組成に着目し、中湿度領域での炭酸化による変質と、炭酸化後に液水と接触した際の変化を確認した。合成したC-A-S-Hについて、NMR、SEM-EDS分析、液相組成分析の結果を基に算出したCa/Si、Al/Si、H/Si、Na/Si比から構造を同定しスキマティックなモデルを示した。炭酸化後の試料には、バテライト、カルサイト、アルミノシリケートゲルの生成を確認した。生成したバテライトは、合成バテライトと異なり450℃で相転移せず、熱重量分析で450～600℃で転移することを実証した。このバテライトは液相浸漬後に相変化し、すべてカルサイトとなることを確認した。生成したアルミノシリケートゲルの組成は、Al/Si＝0.16、Ca/Si＝0.09、Na/Si＝0.09であった。</p>

DOI： 10.14250/cement.77.62

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 セメント協会  

<p>コンクリート中の液水移動を可視化するため、乾燥状態にあるコンクリートに対して一面から水分を浸漬した際のコンクリートの状態変化を、対象物表面の微細な変形を検出可能なデジタル画像相関法を用いて可視化した。変形量から主ひずみ分布の経時変化を得ることで、セメントペースト部での乾燥収縮及び液水浸透を原因とする膨潤を示す変形を可視化した。セメント系材料への液水浸透を示す吸水量及び浸透深さと時間平方根との間での線形関係の逸脱を確認し、コンクリートの骨材スケールでの分析においても、セメントペーストの吸水膨張が水分移動の特異性を生じさせることを間接的に示した。</p>

DOI： 10.14250/cement.77.222

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nuclear Engineering and Design  

Aging management and maintenance are essential processes to ensure the safety of reinforced concrete (RC) buildings in nuclear power plants (NPPs). This is because several phenomena induce cracking behavior and mechanical property changes (MPC) in concrete that might change the structural performance and durability of massive RC structures. Although massive RC structures have not been encountered with excessive loading or severe environmental conditions, structural performance and durability have changed owing to cracks regarding restraint volumetric changes (e.g., thermal and drying-shrinkage cracks) and MPC of concrete throughout the service life. This study numerically investigated the whole history of massive RC structures observed under the general conditions of NPPs in Japan. The alternation in seismic performance according to the whole history of the structure was investigated using a rigid body-spring model. The impacts of restrained cracks, the interaction with structural cracks, and the MPC of concrete were determined to clarify their significance, which is generally neglected for the design and inspection process in the engineering practice.

DOI： 10.1016/j.nucengdes.2023.112602

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Building Engineering  

Expansive additives have been used in concrete to compensate for shrinkage and to induce chemical pre-stress. The cement paste incurs internal expansive stress owing to the formation of confined portlandite and ettringite crystals in the pore network, resulting in expansion at the macroscale. In this study, a poromechanical model was designed to model the expansion of cement paste and concrete due to the formation of such expansive hydrates. The effective expansive stress on the cement paste was calculated considering the volume of the hydrates derived from the hydration model and tangent poroelastic properties estimated using a micromechanical scheme. Experiments were performed to measure the expansion of the cement paste and concrete with different amounts of expansive additives under stress-free and restraint conditions. The model predictions were compared with the experimentally measured expansion, which confirmed the rationality of the model for estimating free expansion. Finally, the extension of the current modeling framework to estimate the restrained expansion of concrete is deliberated. The proposed multiscale model can be employed by the engineers to estimate the expansion of cement paste and concrete with EA and provide insights to estimate the amount of EA required for a given application.

DOI： 10.1016/j.jobe.2023.107554

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本コンクリート工学会  

<p>This paper reviews numerical studies on the effect of expansion and damage due to alkali-silica reaction (ASR) on the mechanical performance of concrete and reinforced concrete at the structural scale level. Previous research on model development that has focused on the performance of RC members or structures is collected and summarized based on how they operationalize expansion progress. The models can be divided into three categories: models that receive the target expansion amount as an input value, models that use expansion curves, and models that calculate the increase in free expansion by considering the kinetic process of ASR. The aim of the model development can be related to either the deformation of the member or the load capacity for static or dynamic load actions. Expansion transfer under confined conditions is characteristic of the ASR problem, and the methods to model expansion transfer are accordingly summarized. Various considerations concerning the effect of ASR expansion and associated damage on the concrete constitutive laws are also studied. Expansion transfer under multi-axial stress states can be accurately reproduced by the modeling of expansion redistribution and volumetric expansion reduction under stress conditions. There are diverse methods to model the resultant deterioration of mechanical properties, but the primary method is by reducing the strength and elastic modulus according to empirically determined relationships. The ideal modeling approach is still under discussion because the effect of the anisotropic cracking state on the anisotropic mechanical response still requires further study. Finally, current problems of assessment of ASR-damaged concrete structures were discussed, and the significance of the causal correlation between macroscopic expansion behavior and microscale factors was suggested.</p>

DOI： 10.3151/jact.21.655

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Cement and Concrete Composites  

Expansion of concrete due to expansive additives (EAs) is greatly affected by the degree of external restraints in the form of reinforcements and supports. Furthermore, the presence of anisotropic restraints influences concrete expansion in different directions. In this study, a chemo-mechanical model was developed to estimate concrete expansion under the framework of poromechanics. The volume of expansive hydrates was obtained from the hydration model, which was used for estimating the stress on the cement paste using poromechanical formulations. An external non-isotropic state of stress affects the orientation of crystal precipitating inside the pores of the cement paste. Thus, anisotropy in concrete expansion due to external stress was considered by maintaining the chemo-mechanical equilibrium of crystals of expansive hydrates, which was reflected in the poro-elastic constants utilized to estimate the stress at the cement paste scale. Poroelastic coefficients were estimated using a micromechanical scheme reflecting the effect of crystal orientation. Dedicated experiments were performed to comprehend the anisotropic expansion of concrete under anisotropic external restraint conditions. Finally, the applicability of the model was verified by comparing the expansion in different directions estimated from the model and experiments performed in this study with available literature data. Thus, the developed chemo-mechanical model could benefit practitioners and engineers in evaluating the expansion behavior of restrained concrete for a given application.

DOI： 10.1016/j.cemconcomp.2023.105126

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：セメント協会  

DOI： 10.14250/cement.76.238

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Expansive additives in higher dosages induce chemical prestress in concrete by imparting higher early-age expansion. However, induced stress and concrete expansion can vary significantly, depending on different restraint conditions. In addition, concrete expansion can be highly anisotropic depending on the nature of external restraints and boundary conditions. Experimentations have been performed to study the effect of uniaxial (anisotropic) restraint on the concrete expansion (in both restraint and stress-free directions) and induced prestress. A higher degree of restraint resulted in a substantial decrement in the longitudinal expansion. In contrast, expansion in the stress-free (lateral) direction was not much affected by the restraint in other direction. As a result, an overall decrement in the volumetric expansion was observed with an increase in the reinforcement ratios. Stress induced in concrete due to the restraint expansion in the longitudinal direction was found to be higher for a higher reinforcement ratio. Data provided from the current work can be used for the comprehensive modelling of expansive concrete under external restraints.

DOI： 10.1016/j.conbuildmat.2022.129330

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Engineering Fracture Mechanics  

This study aimed to develop a numerical method to evaluate thermal cracking, in terms of parameters such as thermal crack width and crack spacing, on massive reinforced concrete (RC) wall structures externally restrained by a base structure. The existing experimental study was investigated using the rigid body–spring model (RBSM) with new constitutive laws developed for this objective. Thermal cracks, which localized and propagated throughout the wall thickness, were successfully reproduced, and the good agreement with the experiment indicated the capability of the proposed numerical method. The time-dependent cracking behavior and the impacts of factors affecting thermal cracking, which are difficult to investigate experimentally, are discussed.

DOI： 10.1016/j.engfracmech.2022.108800

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Cement and Concrete Research  

The drying process of pure C3S paste with a water to binder ratio of 0.55 under different relative humidity conditions was monitored using proton nuclear magnetic resonance relaxometry. The desorption isotherm of the interlayer water was obtained experimentally. The relationship between the interlayer water content and T2 value of the interlayer water defines the surface relaxation time, which provides quantitative data regarding the adsorbed water. According to the fast exchange model, the surface area at the sealed condition was 630 m2/g-calcium silicate hydrate (C-S-H), and it decreased during drying, which was associated with an increase in chemically bound water. The ratio of the decrease in the interlayer surface area to the increase in chemically bound water was 5400 m2/g. Based on this value, the total surface area of C-S-H was calculated to 830 to 921 m2/g-C-S-H.

DOI： 10.1016/j.cemconres.2022.106762

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

There has been a recent trend in Japan toward using precast segments to reduce the burden on construction sites and improve productivity. In large-scale precast segment structures such as bridges, the deformation of precast segments must be controlled during yard storage. This paper uses the multi-scale integrated chemo-hygric computational system (DuCOM-COM3) developed and extended by our group to numerically evaluate dimensional stability during yard storage of precast concrete with fly ash for a large-scale precast segmental bridge. To demonstrate the sensitivity to deformation behavior, simulations are conducted under three hypothetical cases of outdoor air temperature, outdoor air humidity, and temperature at the top surface of the segment, including the harsh temperature conditions expected in the Shikoku region. In the sensitivity analysis using the climatic conditions obtained from the field monitoring data as input, the reproducibility of the surface temperature and shrinkage of the concrete segment is improved by introducing the absorption of shortwave radiation by solar radiation on the segment top surface as an input parameter in the simulation.

DOI： 10.3151/jact.20.200

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Advanced Concrete Technology  

For safe disposal of the large volume of concrete waste generated during the decommissioning of the Fukushima Daiichi Nuclear Power Station (F1NPS), the state of Cs and Sr contamination in concrete waste must ideally be estimated in advance during waste disposal planning. Cs and Sr are primarily adsorbed by calcium silicate hydrate (C-S-H) in cementitious materials. However, the amount of adsorption varies greatly with the Ca/Si mole ratio (C/S ratio) of C-S-H and with the presence or absence of coexisting elements, both of which vary according to interactions with the environment. This study attempted to model on the results of experiments on Cs and Sr adsorption by synthetic C-S-H with varying C/S ratios. Furthermore, for verifying whether the model can be applied to F1NPS, the results calculated by the model were compared with the experimental results for Cs and Sr adsorption on cement paste subjected to environmental conditions (carbonation, leaching, and presence or absence of coexisting elements (Na, K)). It was confirmed that the present model is overall able to reproduce Cs and Sr adsorption behavior on cement paste, considering changes due to environmental conditions.

DOI： 10.3151/jact.19.1061

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Advanced Concrete Technology  

Decommissioning of the Fukushima Daiichi Nuclear Power Station (F1NPS) in a proper manner requires assessment of the contamination levels and mechanisms for contamination in the concrete structures. Between January 2018 and March 2020, Japan's Ministry of Education Ministry of Education, Culture, Sports, Science and Technology (MEXT) conducted a project called "The Analysis of Radionuclide Contamination Mechanisms of Concrete and the Estimation of Contamination Distribution at the Fukushima Daiichi Nuclear Power Station". In this review, we outline the results of this study. The experimental results from the first project indicate that concrete carbonation, Ca leaching, and drying conditions affected the adsorption behaviors of Cs and Sr and therefore, their penetration depths. Additionally, the studies showed that a-nuclides precipitated on the surface of the samples because concrete causes a high pH. A reaction transport model was developed to assess further the adsorption characteristics of Cs and Sr in carbonated cement paste and on concrete aggregates. The model used real concrete characteristics from the materials used at F1NPS and historical boundary conditions at the site, including radionuclide concentrations and penetration profiles within the turbine pit wall. Capillary water suction resulting from dried concrete was evaluated by considering structural changes in cement hydrates using X-ray CR and 1H-NMR relaxometry.

DOI： 10.3151/jact.19.950

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Cement and Concrete Research  

The role of a shrinkage reducing agent (SRA) in the hardened cement paste during a first desorption process was investigated by measuring the small-angle X-ray scattering (SAXS). Fractal disc analysis and Guinier approximation were adopted to interpret the SAXS profiles. We experimentally confirmed that the presence of SRA molecules mitigated the piling of calcium-silicate hydrate (C-S-H) sheets, which could be monitored by the increase in the thickness of the disc, representing the agglomeration of C-S-H sheets. In addition, the basal spacing of C-S-H did not change during the drying. By contrast, the diameter of the discs monotonically decreased and showed a similar trend to that of samples lacking SRA. Based on these findings, we concluded that SRA molecules were on the surface of the C-S-H sheets and mitigated the piling, facilitating water removal from the C-S-H agglomeration in the RH range of 80–40%.

DOI： 10.1016/j.cemconres.2021.106429

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Advanced Concrete Technology  

To decommission of the Fukushima-Daiichi nuclear power plant after the reactor accident, it is important to estimate the distribution of radionuclide contamination in the concrete for key elements such as Cs and Sr. A reaction transport model will be developed for these calculations. However, for a realistic model, the behaviors of Cs and Sr penetration in concrete must be experimentally investigated. A part of the results of a MEXT project called “The Analysis of Radionuclide Contamination Mechanisms of Concrete and the Estimation of Contamination Distribution at the Fukushima Daiichi Nuclear Power Station” are presented in this technical report. From our penetration analyses, the behaviors of neither Cs nor Sr were affected by each other. Additionally, the apparent diffusion coefficients of Cs and Sr were not significantly affected by the concentration or the presence of clay in the mortars. The penetration depth of Sr was smaller than that of Cs, and fly ash blended cement increased the resistance to penetration compared with ordinary Portland cement. Carbonation in the mortar samples increased the adsorption of Cs especially. Sr interacted with cement hydrates more than with clays. In oven-dried mortars, under the condition of water suction, the presence of clay retarded Cs penetration but had no effect on Sr. When the mortars were carbonated and oven-dried, the interactions between the solid phase and Cs or Sr took hours at least to complete.

DOI： 10.3151/jact.19.756

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記述言語：英語   掲載種別：論文集(書籍)内論文   出版者・発行元：Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations - Proceedings of the 10th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2020  

Japan Nuclear Energy Safety Organization (JNES) has published an aggregate test method so-called as JNES flow (the method mainly composed of international methods RILEM AAR 3 and RILEM AAR 4) and alkali-silica reaction (ASR) diagnosis method. In this research, we conducted the RILEM methods using Japanese aggregates, which were international aggregate test methods that were considered to be highly reliable. Especially, we evaluated the suitability of various RILEM aggregate testing methods for Japanese aggregates with regard to methods for detecting reactivity of late expansive aggregates, which have been reported in recent years. Furthermore, for the ASR diagnostic method that emphasizes the petrological evaluation test after collecting concrete cores samples, various test specimens with different stages of deterioration were produced, and the core appearance observation and polarization microscope observation were performed on the collected core samples. We also conducted observations using a film scanner and evaluated the applicability of the proposed ASR diagnostic method to Japanese aggregates. Based on the above, an example of the alkali aggregate reaction test flow of concrete structures effective for reactive aggregates were proposed through comparison among various domestic and international aggregate test methods. Furthermore, an example of the alkali aggregate reaction diagnosis flow of concrete structures was proposed by conducting tests with several methods using cores which were sampled from the concrete specimens and the concrete structures.

DOI： 10.1201/9780429279119-362

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Advanced Concrete Technology  

This experimental and numerical study aims to evaluate the penetration depth of contaminated water in the concrete structures involved in the Fukushima Daiichi nuclear powerplant. The influence of the mortar mixture on water absorption was investigated by varying the composition: mortars containing aggregates from river sand and crushed limestone sand were compared, and 15% of the cement in the mixture was substituted with fly ash. The effect of temperature in nuclear conditions is also significant; therefore, water uptake at temperatures of 20 and 60°C was considered. Finally, pre-drying conditions were studied by drying the sample at two different conditions: at 105°C and at 40% RH (relative humidity) and 20°C. Water uptake was monitored using x-ray computed radiography in combination with mass measurements. In all cases, anomalous sorption, or a nonlinear relationship between penetration depth and the square root of exposure time was observed, with the sorption curves showing bimodal behavior. The aggregate type had no significant effect on the water uptake results. However, the samples containing fly ash clearly had lower water uptake rates, which can be explained by the differences in the calcium silicate hydrate (C-S-H) structures. With increasing temperature, the penetration was slightly accelerated at the beginning of the experiment, with the rate of penetration then decreasing rapidly. The densification of C-S-H at higher temperatures could contribute to this phenomenon. Microstructural rearrangements can also explain why the highest uptake rates occurred for samples that were exposed to severe drying conditions (105°C). The experimental results were consistent when the microstructural rearrangement was considered, further confirming these conclusions.

DOI： 10.3151/jact.19.168

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：論文集(書籍)内論文  

This study aims to develop an analytical tool to predict the expansion of Hauyne and free-lime based expansive additives in RC structures. Hydration of species was based on the multi-component heat of hydration model which incorporates referential heat rate at a certain temperature and thermal activities following Arrhenius' law of chemical reaction. All other time-dependent properties of concrete such as elastic modulus, temperature, pore pressure, creep, moisture status, total porosity of interlayer, gel and capillary pores are computed internally based on the micromodels of materials inside the system. Coupling this material information with poromechanics, volumetric change generated by cement hydration and shrinkage is systematically included in the modelling of concrete mechanics, which deals with macroscopic structural responses based on the space-averaged constitutive laws on the fixed four-way cracked concrete model. Finally, the models are then verified with experimental results that could prove the models’ capability in predicting the amount of expansion under various replacement ratios.

DOI： 10.1007/978-3-030-72921-9_18

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Advanced Concrete Technology  

During sorption, the microstructural evolutions of two different cement pastes (with water-to-cement ratios of 0.40 and 0.55) are studied via proton-nuclear-magnetic-resonance relaxometry. The water uptake test is performed for samples dried at 105°C under three different temperatures of 20°C, 40°C, and 60°C for the first twenty-six days of sorption. It is observed that the water went first to the larger pores before migrating to the finest ones. This behavior is accelerated with increasing temperature. The rate of water exchange between fine and large pores is estimated and found to increase with temperature for both studied mixtures. The activation energy corresponding to this water movement is calculated and found to be higher for the lowest water-to-cement ratio, owing its finer microstructure. Finally, the activation energy related to the local water transport in re-distribution from large pores to fine pores is calculated and found to be inferior to the experimental results, which can be explained by the dynamic microstructure not being considered in the classical theories.

DOI： 10.3151/jact.18.588

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Ultra-High Performance Fibre-Reinforced Cementitious Composites (UHP-FRCC) show excellent mechanical performances in terms of strength, ductility, and durability. Therefore, these cementitious materials have been successfully used for repairing, strengthening, and seismic retrofitting of old structures. However, UHP-FRCCs are not always environmental friendly products, especially in terms of the initial cost, due to the large quantity of cement that is contained in the mixture. Different rates of fly ash substitute herein part of the cement, and the new UHP-FRCCs are used to retrofit concrete columns to overcome this problem. To simulate the mechanical response of these columns, cylindrical specimens, which are made of normal concrete and reinforced with different UHP-FRCC jackets, are tested in uniaxial compression. Relationships between the size of the jacket, the percentage of cement replaced by fly ash, and the strength of the columns are measured and analyzed by means of the eco-mechanical approach. As a result, a replacement of approximately 50% of cement with fly ash, and a suitable thickness of the UHP-FRCC jacket, might ensure the lowest environmental impact without compromising the mechanical performances.

DOI： 10.3390/ma12234010

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

The Fukushima-Daiichi nuclear power station accident in East Japan in 2011 released radioactive cesium (r-Cs) into the surrounding environment. In addition to the major contamination of soil and vegetation, surrounding concrete structures have also been contaminated. Understanding the contamination characteristics is important for the decontamination or disposal of offsite and onsite concrete structures. However, r-Cs contamination of actual concrete has not been extensively investigated. In this paper, the r-Cs contamination characteristics of actual concrete are introduced on the basis of several field surveys and analysis of concrete samples taken from actual contaminated structures in the Fukushima prefecture. As no dissolution to water was detected, the surface contamination was safely removed by water-jet abrasion. However, in KCl solution, significant dissolution of r-Cs was detected. A contamination depth analysis was performed by quantitative r-Cs concentration mapping based on beta-ray radiography using imaging plates. In many cases, such as roadside gutter cover plates, r-Cs was located on the surface without significant penetration into the concrete. However, in cases such as degraded concrete, deeper penetration up to several millimeters deep was observed. In cracked concrete, the r-Cs penetrated at least 10 cm, with the contamination level decreasing one order of magnitude in the first 1 cm.

DOI： 10.3151/jact.17.659

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担当区分：筆頭著者,　責任著者  

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本コンクリート工学会  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本コンクリート工学会  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本コンクリート工学会  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本コンクリート工学会  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本コンクリート工学会  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本コンクリート工学会  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本コンクリート工学会  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Alkali release from aggregates is considered to cause expansion due to the alkali-silica reaction (ASR), owing to the increase in the hydroxide ion concentration (namely pH) of the pore solution. However, a direct validation of this assertion has not yet been made. In this research, the effects of the type of soak solution, which might better mimic the composition of the pore solution, on the behavior of alkali release from aggregates are investigated through immersion tests of aggregates. More importantly, accompanying ions dissolved from the aggregates are also measured in order to determine the mechanism for the increase in hydroxide ion concentration of the pore solution. The test results show that this increase can barely be observed, despite a considerable amount of alkalis being released. The results critically question the conventional view that alkali released from an aggregate serves to accelerate the ASR.

DOI： 10.3151/jact.16.61

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Ultra High Performance - Fiber Reinforced Cementitious Composites (UHP-FRCC) has successfully developed in the last decades. They show excellent mechanical properties and durability, due to the highly dense microstructure produced by extremely low water/binder ratio and large amounts of cement. Thus, replacing part of the cement content with High Volume Fly Ash (HVFA) could be an effective way to improve also the ecological properties of UHP-FRCC. Indeed, most of the carbon footprint of cement-based composites is caused by the CO2 production of cement manufacturing. On the other hand, HVFA tends to reduce the mechanical properties of UHP-FRCC, especially at the early age. To evaluate the effect of some cement replacement (20, 50 and 70% by weight), a series of uniaxial compression and tensile tests have been performed and described in this paper. At the same time, through the Eco-Mechanical Index (EMI), ecological performances are evaluated on the basis of the measured mechanical properties. As a result, the application of UHP-FRCC in full-scale structures (e.g., composite concrete columns) is really convenient in the presence of HVFA, although the material properties (the compressive strength, in particular) show an opposite trend.

DOI： 10.1007/978-94-024-1194-2_29

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

J-GLOBAL

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Meso- and micro-scale structural changes in matured hardened cement paste dried slowly for 1.5 years at different relative humidities (RHs) are evaluated by small-angle X-ray scattering profiles covering a q range of 0.017 nm− 1–30 nm− 1 with a fractal disc-shaped particle analysis and Guinier approximation. The fractal disc-shaped particle analysis revealed that calcium–silicate–hydrate (C–S–H) agglomerations are very thin (~ 2.5 nm) and of relatively large width (~ 35 nm) under high RH conditions. However, the agglomerations are segmented (in width) into ~ 10 nm below an RH of 40%. The Guinier approximation found the possibility that the scattering profiles in the range of 2 nm− 1–8 nm− 1 correspond to a spacing between C–S–H monolayers and it showed stepwise changes at 40%–50% RH. The stepwise behavior of the distance between C–S–H monolayers may explain a kink in water vapor desorption at around 40% RH.

DOI： 10.1016/j.cemconres.2016.10.002

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Ultra-high-performance fiber-reinforced cementitious composite (UHP-FRCC) has been successfully developed over the last decade. UHP-FRCC shows very high strength and high durability because of its very low water binder ratio and dense microstructures. Moreover, by incorporating a combination of steel and mineral fibers with different sizes in the mixture design, UHP-FRCC also exhibits high ductility and high energy absorption capacity, even under uniaxial tensile stress. The high ductility of UHP-FRCC materials shows strain hardening behavior with multiple cracking after the occurrence of the first crack. While extensive research on the tensile and bending behavior of this composite under short-term loading is reported, only limited results can be found on time-dependent behavior of UHP-FRCC under sustained long-term loading, which is strongly related to the situation of real structures. This paper presents experimental results concerning the time-dependent behavior of cracked UHP-FRCC specimens under sustained bending load. In bending creep test, sustained load with 50 % of the pre-cracking load was applied to a pair of prismatic specimens of 50 x 100 x 400 mm under a 4-point bending setup. The performance of UHP-FRCC is compared with those of conventional fiber reinforced cementitious composites(FRCC) using steel and synthetic fibers, which are investigated within the Round Robin Test (RRT) organized by RILEM TC 261-CCF. The results showed that UHP-FRCC exhibited smaller creep deformation at the sustained loading condition than the conventional FRCC, even when the initial deformation of the UHP-FRCC is much larger than the conventional FRCC. Cracking pattern, in terms of crack width and number of cracks, was also studied in both composites under sustained loads. As a result, the superior resistance of UHP-FRCC was obtained with respect to conventional FRCC.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Ultra-High-Performance Fiber-Reinforced Cementitious Composite (UHP-FRCC) shows very high strength and durability due to its very dense microstructure. While extensive research on the tensile and bending behavior of this composite under short-term loading has been reported, limited results are available on the time dependent behavior of UHP-FRCC under sustained loading, which are strongly related to the real-life-structures. This paper presents experimental results concerning creep behavior of cracked UHP-FRCC specimens under sustained tensile and bending loads up to 28 days. Under uniaxial tension, the load is applied to dog-bone type specimens. In the case of bending creep test, a sustained load is applied to a pair of prismatic specimens in a 4-point bending setup. The results show that UHP-FRCC exhibits low creep deformation under both these loading conditions. Furthermore, deflection hardening behavior lasts under Cracking behavior in terms of crack width and number of cracks under sustained loads in both composites is also studied and their comparisons are presented in the paper.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 セメント協会  

<p>アルカリシリカ反応（ASR）による劣化は、反応性骨材内部で生成するアルカリシリカゲル（ASG）が引き起こす膨張に起因することは明らかなものの、コンクリート内部での膨張圧およびこれに伴う膨張ひび割れの発生機構は完全な解明に至っていない。そこで、急速膨張性の安山岩を用いて単純な系のモデル試験体を作製し、促進養生後の試験体切断面のASG分布およびひび割れを観察した。その結果、ASRに伴う膨張圧は反応性骨材単体で生じるのではなく、反応性骨材周囲に緻密なセメントペーストマトリクスが、反応性骨材外部へのASGの滲出を抑制することによって、ASGが反応性骨材内部に累積されて生じると考えられた。</p>

DOI： 10.14250/cement.71.272

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

For the purpose of performance evaluation of an existing reinforced concrete member, a chemo-thermo-hygro model to predict the spatial and temporal changes of physical properties of concrete in the member, named the "Computational Cement-Based Material Model (CCBM)", was proposed. This proposed simulation model includes models of rate of hydration of cement minerals, phase composition, and resultant properties of cement paste (i.e., compressive strength, Young's modulus, Poisson's ratio, thermal expansion coefficient, autogenous shrinkage, drying shrinkage, heat capacity, heat transfer coefficient, water vapor sorption isotherms, and water transfer coefficient). Furthermore, the model for compressive strength of concrete considered the variation in cement paste strength due to its colloidal features as well as micro-defects produced around aggregate due to differences in volume between aggregates and mortar upon heating and drying. The concrete properties of spatial distribution and temporal changes were evaluated by coupling these models with heat and water transport. Validation of these models was achieved by using existing experimental data. Using this CCBM, a thick concrete wall made with moderate Portland cement with a water-to-cement ratio of 0.55 under one-sided heating was simulated and potential problems that can arise during an integrity evaluation were discussed. If the required compressive strength, which was assessed within 91 days of placement, remains unchanged, an additional hydration process can build an adequate strength margin to overcome the risk of strength reduction due to heat and drying. However, in the case that the required strength is increased due to a re-evaluated risk, such as the magnitude of an earthquake, performance evaluation is not trivial as the core sample taken from the side where the execution of sampling is possible could exhibit a greater strength than the average strength of the target concrete member. Therefore, numerical evaluation might aid in this kind of situation.

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Abstract A method for predicting volume changes of aggregate during variations in humidity and temperature was studied. Siliceous rock aggregates commercially available in Japan were sampled from various regions and subjected to XRD (X-ray diffraction) analysis, thermal analysis, and volume change experiments. Drying shrinkage strain and the thermal expansion coefficient of the aggregates were found to be related to their mineral composition and bound water content. Experiments confirmed that drying shrinkage was correlated with the chlorite and bound water content of the aggregate, and that thermal expansion coefficients were correlated with the aggregate's quartz content.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Abstract Short-term length change isotherms (SLCIs) and water vapor sorption isotherms are useful to eliminate the effects of the colloidal features of C-S-H. SLCIs of hardened cement pastes initially conditioned by drying to equilibrium at different relative humidities (RHs) were measured over a complete RH loop between 5% and 98%. Based on the correlation between incremental thickness of adsorption and incremental strain from 40% to 98% RH, the basal spacing of C-S-H above 40% RH appears to increase further with increasing water vapor sorption. However, no correlation of these values was found from 5% to 40% RH and the basal spacing is considered stable in this domain. These properties of C-S-H are directly related to its isothermal volume change as a function of RH. It can be concluded that the dominant shrinkage driver above 40% RH is disjoining or hydration pressure and that below 40% RH is change in surface energy.

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Understanding changes in the strength and Young's modulus of concrete under long-term drying or heating less than or equal to 90°C is crucial for managing the aging of industrial buildings. We collected experimental data on changes in the physical properties of concrete components, aggregates, cement pastes, and concretes containing different aggregates and mortar under different heating and drying conditions. The change in compressive strength of concretes under various drying or heating conditions was explained by the behavior of the cement paste matrix and damage accumulation caused by differences in volume changes between the aggregate and mortar. In contrast, the variation in the Young's modulus of concrete caused by the drying or heating conditions was mainly explained by the increase in the number of voids due to internal cracking in the concrete. © 2014 Elsevier Ltd.

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The body of data about the reaction kinetics of cement has greatly grown in recent years, and in terms of techniques for the prediction of the resulting hydrate formation phases, databases contributing to thermodynamic equilibrium calculations have been developed and are growing increasingly sophisticated. On the other hand, though many studies on cement aim to contribute to concrete engineering and numerical model researchers have pointed out the necessity of shedding light on the relationship between the microstructures generated by hydration and physical properties, such data remains scarce. This study investigated Portland cements using two commonly used water-cement ratios and three types of mineral compositions in the material age range of up to one year. The phase composition in relation to cement hydration was determined by X-ray powder diffraction and Rietveld analysis. In terms of physical properties, compressive strength and Young's modulus were measured through loading tests, and Young's modulus and Poisson's ratio were also obtained from the ultrasonic pulse propagation velocity of longitudinal and transverse waves. Further, water vapor adsorption tests to shed light on moisture behavior were conducted, yielding the BET specific surface area. Thermal conductivity, an important determinant of thermal behavior, was measured using the transient hot wire method. On the premise of the application of these physical properties to numerical calculations, their correlation with the information obtained from the phase composition was considered, leading to the proposal of simple and relatively high-accuracy empirical formulas. Further, background information about raising the correlation of these empirical formulas was also discussed. Copyright © 2014 Japan Concrete Institute.

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper reports the microstructural changes and resultant bulk physical property changes in hardened cement paste (hcp) during the first desorption process. The microstructural changes and solid-phase changes were evaluated by water vapor sorption, nitrogen sorption, ultrasonic velocity, and 29Si and 27Al nuclear magnetic resonance. Strength, Young's modulus, and drying shrinkage were also examined. The first drying process increased the volume of macropores and decreased the volume of mesopores and interlayer spaces. Furthermore, in the first drying process globule clusters were interconnected. During the first desorption, the strength increased for samples cured at 100% to 90% RH, decreased for 90% to 40% RH, and increased again for 40% to 11% RH. This behavior is explained by both microstructural changes in hcp and C-S-H globule densification. The drying shrinkage strains during rapid drying and slow drying were compared and the effects of the microstructural changes and evaporation were separated. © 2014 Elsevier Ltd.

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Cement pastes undergo elevated temperature histories due to hydration heat liberation at early ages. Thermal expansion coefficients of cement paste and concrete change with age, showing a decrease after mixing, a subsequent minimum and then a gradual increase. These changes contribute to thermal strain. In this study, effects of water-cement ratio and cement type on volume changes in early-age cement pastes were experimentally examined using a newly developed apparatus capable of simultaneously determining both thermal expansion coefficient and total strain of cement pastes. The dependence of the thermal expansion coefficient on hydration was affected by water-cement ratio, cement type, elevated temperature history and particularly by the free water content of the cement pastes, while the relationship between thermal expansion coefficient and free water content varied with water-cement ratio. A notable increase in thermal expansion coefficient at early ages was observed when water-cement ratio was low and alite content in cement was high. At a water-cement ratio of 0.30, low-heat Portland cement paste resulted in a small total strain while moderate-heat and ordinary Portland cement pastes showed larger strains. Because no particular difference was observed in the thermal strains, shrinkage in the low-heat Portland cement paste was attributed to autogenous strain. At a water-cement ratio of 0.40, self-desiccation had a significant influence upon autogenous shrinkage and dependence of thermal expansion coefficient on hydration, and the effect of the mineral composition of cements was notable. However, for cement pastes with a water cement ratio of 0.55, no significant effects of self-desiccation were observed, probably because considerable excess water was present. © 2013 RILEM.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society of Mechanical Engineers, Power Division (Publication) POWER  

Methods for assessing the soundness of concrete exposed to irradiation are being developed within the framework of a project of the Nuclear Regulation Authority (NRA) "Japan Ageing Management Program for System Safety". This paper presents the background of this project and recent research works. The major reason for deterioration of concrete under irradiation conditions is expansion of aggregate due to neutron and gamma-ray irradiation. Dislocation of atoms in covalent structures of aggregate minerals, and resultant lattice constant change and alteration to amorphous phase are produced by fast neutrons. In addition, through electronic exertion, some energy deposition is accumulated as permanent distortion/strain in atomic structures. Other effects are also summarized. We plan to conduct a neutron irradiation test from May 2013. In selecting mix proportions and concrete components for the irradiation test program, sample size as a function of capsule size and gamma-heating, cement type, and aggregate size and type are determined based on preliminary experiments. Copyright © 2013 by ASME.

DOI： 10.1115/POWER2013-98114

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3130/aijs.78.1203

担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本材料学会  

Hydrated hardened cement paste samples using white cement were cured under different relative humidity conditions. After 180-day drying, Adsorption and desorption isotherms as well as chemically bound water of cured hardened cement paste were measured. Based on the adsorption data, it was concluded that drying process has two different effects on a sorption property. One effect was seen in drying process over 70%RH. Capillary pore with more than 2nm size was collapsed and amount of capillary condensation is decreased as it is dried in the lower relative humidity. The second effect was seen in drying process under below 60%RH. The vapor BET surface area was dramatically decreased as cement paste cured in lower relative humidity. From the change of chemically bound water and vapor BET surface area, it was deduced that a reaction of silanol to siloxane bond in C-S-H poses decrease in vapor adsorption sites.

DOI： 10.2472/jsms.62.219

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Sustainable Construction Materials and Technologies  

Water vapor sorption isotherms, nitrogen sorption isotherms, and bending strength of cement paste cured with different relative humidity for 1 year are measured. Effect of drying on microstructure has two ways. One is nano-scale effect, in which nano-scale pore among globules is collapsed due to capillary tension or solution and re-precipitation cycle of C-S-H. The other one is atomic-scale effect, in which water adsorption sites are reduced due to drying by changing of other than Si network. From such effect, cement paste shows different nature of microstructure according to thermodynamic conditions, and resultantly, the physical properties are altered.

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3130/aijs.77.1819

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本建築学会  

Prediction system for compressive concrete strength in aged structural member is proposed. This system is composed of models of rate of hydration, cement paste phase composition, heat production, specific heat, compressive strength, vapor desorption isotherm, coupled heat and moisture transfer. Each model is verified through experimental data. This system is aiming for the structural member which can not be accessed or can not be evaluated by the core sample test. Using non-destructive data or quality control sample's data, this system might illustrate the distribution and development of concrete strength in structural member properly. From the calculation results for a concrete member exposed to high temperature condition, strength development as well as distribution is quite sensitive to the boundary condition, and this concludes that the evaluation of structural member under such special condition needs precise boundary conditions.

DOI： 10.3130/aijs.77.323

Scopus

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3130/aijs.77.153

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Structural and Construction Engineering  

Hydration process of many kinds of cement paste is investigated by powder X-ray diffraction (XRD)/Rietveld analysis. The parameters of the present study are type of cement (Ordinary Portland cement, Low heat cement, and Eco-cement), water to cement ratio (0.50, 0.35), and curing temperature (283, 293, 313K). In this contribution, reaction of aluminate phase (3CaO·Al 2O 3) and ferrite phase (4CaO·Al 2O 3· Fe 2O 3) are focused and evaluated. Experimental results show that the reaction of both aluminate phase and ferrite phase are affected by the temperature and presence of calcite. When system includes calcite, monocarbonate aluminate is mainly produced, rather than ettringite. And in the case of high curing temperature, Al 2O 3 is reacted as amorphous. Regarding ferrite phase, the reaction degree at the age of 1 year decrease as curing temperature increases, this can be presumed due to dense amorphous phase around cement minerals. Based on these experimental facts, simple hydration model is proposed to evaluate development of hydration degree of aluminate phase and ferrite phase.

DOI： 10.3130/aijs.76.1

Scopus

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3130/aijs.76.1737

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3130/aijs.76.1033

担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3130/aijs.76.865

担当区分：最終著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3130/aijs.76.231

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3130/aijs.76.213

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

水セメント比が30％、40％、55％、骨材体積比が0％から60％の12調合のセメント硬化体及びモルタルを作製し、若材齢から縦波・横波伝搬速度試験を行うことでポアソン比と動弾性係数を得た。その結果、骨材量により速度は異なるが、全ての試験体でポアソン比は硬化に伴い減少し、ある値に収束した。ポアソン比の経時変化を考慮して、複合則理論によって動弾性係数の骨材量依存性を検討した結果、ポアソン比を考慮しない場合と比較して、骨材量が40％以上の領域で若材齢における推定精度が向上するものがみられた。一方、骨材量が60％のものは動弾性係数を過大に推定する結果となり、空気量の影響を考慮する必要があると考えられた。

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

合成したC-S-Hに関して、Ca/Siモル比の変化に伴う水蒸気吸着性状の変化について検討を行った。水蒸気吸着等温試験および熱分析により、C-S-Hの水蒸気吸着性状に関する実験値を取得し、Nonatらが提唱しているC-S-H溶解平衡モデルを基とした構造モデルおよび水蒸気吸着モデルを提案し、水蒸気吸着BET比表面積の予測を試みた。その結果、Ca/Siモル比の変化に伴う比表面積の変化をC-S-H表面の反応基の変化に基づき予測できるモデルが構築された。

CiNii Research

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

高炉スラグ微粉末を混和したセメント硬化体の長さ変化等温線、脱着・吸着等温線、ヤング率・ポアソン比、および密度を実験的に取得し、著者が提案したDerjaguinの水和親力に基づく水和圧理論に基づき、高炉スラグ微粉末を混和したセメント硬化体の乾燥収縮性状および表面の親水性について考察した。その結果、高炉スラグ微粉末を混和したセメント硬化体の親水性は、普通ポルトランドセメントのそれよりも大きく、表面と水との相互作用力の減水定数が大きくなる結果となり、このことが、高炉スラグ微粉末を用いたセメント硬化体の保水性および大きな乾燥収縮性状につながるものとわかった。

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

普通ポルトランドセメントを用いた水セメント比0.40、0.55の初期高温履歴を受けたセメント硬化体の比表面積の経時変化について検討を行った。吸着等温線、粉末X線回折/リートベルト解析の結果から、セメント硬化体の比表面積、C-S-H量およびC-S-HのCaO/SiO₂モル比の同定を行い、比表面積との関係を評価し、併せて、合成C-S-Hとの比較を行った。その結果、初期高温履歴の影響により、長期的な比表面積の増進が停滞すること、C-S-Hの平均CaO/SiO₂モル比が増大すること、セメント硬化体の比表面積とC-S-H量は、水セメント比、温度条件によらず一つの曲線で評価されることが明らかとなった。

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

セメント硬化体の吸着等温線が何に支配されているか、あるいは乾燥プロセス中に任意温度・相対湿度条件下でどれだけの含水状態で平衡となるのかに関する支配的要因を明らかにすることを最終的な目的として、まずは、ヒステリシスが生じるメカニズムを考察した。セメント硬化体の吸着等温線試験を行いそこで生じる現象について既往の文献も含めて考察を行った結果、乾燥条件下、および乾燥後の吸湿プロセスの極初期ではC-S-Hが化学的に反応し、Si-O-Si結合が増加して比表面積が減少するものと考えられた。このメカニズムを検証する目的で、合成したC-S-Hの異なる乾燥条件時の赤外吸収スペクトル、NMRスペクトルを測定し、乾燥条件下でSi-O-Si結合が増加することが定性的に確認された。

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

J-GLOBAL

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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Expansive additives are being widely used as shrinkage reducing/compensating admixture to reduce the early-age cracking and chemical prestressing. Such expansive additives influence the composition of cement hydration products and mechanical properties (stiffness and strength) of the cement and concrete, which ultimately affects the early age deformation. In the current study, the EMM-ARM (Elastic Modulus Measurement by Ambient Response Method), is used because of its ability to continuously monitor cement's real-time stiffness development paste with expansive additives. Stiffness development of the cement paste with expansive additives is captured in the unrestrained condition by allowing the free expansion during the stiffness measurement. An expansive additive, based on free lime, with a 10% (by weight) cement replacement ratio is studied in the current work. Results from the EMM-ARM are compared to the elastic modulus measurement from the compression testing of cylindrical specimens, and the mechanisms of expansive action on the microstructure in early-age are discussed.

DOI： 10.1007/978-3-030-72921-9_26

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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その他リンク： https://www.aij.or.jp/paper/detail.html?productId=624690

記述言語：日本語   出版者・発行元：日本建築学会  

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その他リンク： https://www.aij.or.jp/paper/detail.html?productId=624694

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語  

J-GLOBAL

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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その他リンク： https://www.aij.or.jp/paper/detail.html?productId=601357

記述言語：日本語   出版者・発行元：日本建築学会  

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その他リンク： https://www.aij.or.jp/paper/detail.html?productId=601349

記述言語：日本語   出版者・発行元：日本建築学会  

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その他リンク： https://www.aij.or.jp/paper/detail.html?productId=601356

記述言語：日本語   出版者・発行元：一般社団法人 セメント協会  

<p>アルカリシリカ反応（ASR）による劣化は、反応性骨材内部で生成するアルカリシリカゲル（ASG）が引き起こす膨張に起因することは明らかなものの、コンクリート内部での膨張圧およびこれに伴う膨張ひび割れの発生機構は完全な解明に至っていない。そこで、急速膨張性の安山岩を用いて単純な系のモデル試験体を作製し、促進養生後の試験体切断面のASG分布およびひび割れを観察した。その結果、ASRに伴う膨張圧は反応性骨材単体で生じるのではなく、反応性骨材周囲に緻密なセメントペーストマトリクスが、反応性骨材外部へのASGの滲出を抑制することによって、ASGが反応性骨材内部に累積されて生じると考えられた。</p>

DOI： 10.14250/cement.71.272

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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その他リンク： https://www.aij.or.jp/paper/detail.html?productId=427867

記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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その他リンク： https://www.aij.or.jp/paper/detail.html?productId=415001

記述言語：日本語   出版者・発行元：日本建築学会  

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その他リンク： https://www.aij.or.jp/paper/detail.html?productId=419156

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：公益社団法人 日本コンクリート工学会  

DOI： 10.3151/coj.51.291

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記述言語：日本語   出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.78.1203

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.77.323

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記述言語：日本語   出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.77.509

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記述言語：日本語   出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.77.1819

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記述言語：日本語   出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.77.153

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記述言語：日本語   出版者・発行元：日本建築学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本建築学会  

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記述言語：日本語   出版者・発行元：日本建築学会  

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DOI： 10.3130/aijs.76.213

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出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.76.1

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出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.76.231

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出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.76.1737

CiNii Research

出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.76.1033

CiNii Research

出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.76.865

CiNii Research

出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.76.865

CiNii Research

出版者・発行元：日本建築学会  

DOI： 10.3130/aijs.76.1033

CiNii Research

記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Research

記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Research

記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Research

記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Research

記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Research

記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

CiNii Research

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Research

記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Research

記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Books

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記述言語：日本語   出版者・発行元：日本建築学会  

CiNii Research

開催年月日： 2011年2月

記述言語：日本語  

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開催年月日： 2010年7月

記述言語：日本語  

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開催年月日： 2010年2月

記述言語：日本語  

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開催年月日： 2010年2月

記述言語：日本語  

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開催年月日： 2009年7月

記述言語：日本語  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

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