著者

村上 雅也

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.19, no.8, pp.39-45, 1981

著者

Hongda Guo Qing Liu Jianyu Xu Guoxing Sun

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.19, no.3, pp.240-247, 2021-03-20 (Released:2021-03-20)

参考文献数

35

被引用文献数

4

---

High-strength and lightweight are two of the most important parameters for composites in the construction field. Here, we developed a novel foam concrete structure with sandwich porous structure by using in-situ polymerized polyacrylamide and ultra-stable foam, which can obtain higher mechanical strength in comparison to the normal porous concrete with the same density. The ratio of stiffness to weight was maximized to achieve the optimal sandwich porous structure size. The SEM images showed that the interface bond between the foam concrete and the polymer modified cement paste was tight and robust. The flexural strength of the novel structure was 65.6% higher than that of the foamed concrete at the same density. The series model was established to calculate the composite thermal conductivity of the novel foam concrete structure, indicating that the heat insulation was slightly improved compared with the normal foam concrete. Moreover, water resistance displayed a slight increase by constructing this sandwich porous structure. Hopefully, the novel composite with sandwich porous structure can put a new way for designing the lightweight and high strength insulation thermal structure.

著者

横山 治郎 武田 俊明

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.13, no.9, pp.10-20, 1975

著者

Kenichi Horiguchi Toshinobu Yamaguchi Tsuyoshi Maruya Koji Takewaka

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.571-587, 2020-10-16 (Released:2020-10-16)

参考文献数

47

被引用文献数

1 2

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In this study, a method was developed to estimate accurately the chloride threshold value for corrosion initiation in reinforced concrete. In this method, chlorides are supplied through a part of the specimen surface, and half-cell potential between the rebar and reference electrode embedded in a concrete specimen was measured in every ten minutes. A sudden drop of half-cell potential was observed as the continuation of the measurement. At that time, the specimen was broken and corrosion of rebar on its narrow surface was confirmed. The chloride threshold value can be estimated by determining the chloride concentration at the time of the potential drop. The estimated chloride threshold values for normal Portland cement concrete with cement content between 254 and 446 kg/m3 are in the range of 1.6 to 3.6 kg/m3. This paper is an English translation from the authors’ previous work [Horiguchi, K., Yamaguchi, T., Maruya, T. and Takewaka, K., (2015). “A study on the method of measuring the chloride threshold value of corrosion and on the estimation of the values.” Journal of JSCE, Ser. E2, 71(2), 107-123. (in Japanese)].

著者

Yongqin Liang Licheng Wang

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.18, no.11, pp.699-715, 2020-11-20 (Released:2020-11-20)

参考文献数

112

被引用文献数

7

---

Rebar corrosion is a main cause affecting the durability and safety of reinforced concrete structures. Many mathematical models (empirical and analytical models) have been proposed to predict the corrosion-induced cracking of concrete cover over the recent decades. These models have differences in many aspects, such as constitutive laws for cracked concrete. However, each of them claimed that it could well agree with the test data. This may be due to the fact that a small amount of test data were used to verify their models. Besides, there are many uncertain factors such as the rust volumetric expansion factor and elastic modulus relating to these predictive models, which seriously weaken their effectiveness and accuracy. Thus, in this paper, the predictive performances of various mathematical models are tested by collecting an amount of test data. After that, the uncertain factors are summarized, and the reasons are analyzed though reviewing relevant knowledge in various literature. It is found that different performances are obtained for different mathematical models and test data. These uncertain factors involve many fields, such as electro-chemical factors (corrosion current density, corrosion current efficiency, corrosion rate, loading effect of corrosion current), rust properties (rust volumetric expansion factor, rust elastic modulus), long-term behavior of concrete (creep coefficient), rust penetration into concrete (amount of rust penetrated into concrete pores and cracks) and corrosion morphology. These uncertain factors are raised due to either the limit of experimental techniques, the discrepancy of parameter values, time-dependent properties, or the lack of detailed environmental information. In addition, other factors are too complex to be delicately taken into account, which have to be ignored in the predictive models. Through parameter analysis, it is found that these factors have large effects on cracking time of concrete cover. Prospective modifications of these factors are suggested, and more detailed and systematic tests should be carried out by using novel and sophisticated apparatuses in future.

著者

Toshifumi Kikuchi Yasuhiro Kuroda

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.9, no.1, pp.115-124, 2011-02-23 (Released:2011-02-22)

参考文献数

12

被引用文献数

28 78

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One of the largest contributors of the greenhouse gas emission is the production of cement for use in concrete. However, concrete is well-known for its carbon dioxide (CO2) uptake by carbonation. The purpose of this study was to consider the CO2 uptake in demolished and crushed concrete. In this study, three kinds of experiments and survey were carried out, including (1) an experiment using mortar specimens made in the laboratory so as to identify the conditions that accelerate CO2 uptake, (2) an experiment using concrete obtained from the demolition site and (3) a survey on the CO2 uptake in recycled crusher-run stone obtained from recycling plants. The experiment on new mortar and demolished concrete pointed out that the CO2 uptake in cement hydrate increases significantly when the particles are relatively small and when they are alternately wetted and dried. Furthermore, the survey on concrete at recycling plants found the amount of CO2 uptake in one ton of recycled crusher-run stone to be approximately 11 kilograms. Finally, using this value, the life cycle of CO2 of concrete structures was calculated and shown to be approximately 5.5% less when the CO2 uptake is taken into account compared to when it is not taken into account.

著者

Peiyi Zhang Atsushi Teramoto Takaaki Ohkubo

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.18, no.9, pp.521-531, 2020-09-24 (Released:2020-09-24)

参考文献数

32

被引用文献数

6

---

The adhesion failure of the interface between concrete and rendering mortars often leads to the degradation of the reinforced concrete building envelopes. Although several methods to improve the adhesion properties between concrete and rendering mortar have been proposed, there is no system to evaluate the effectiveness of these methods from the perspective of durability. To this end, this study proposed an experimental method to evaluate the durability of rendering mortar and concrete adhesion systems at the laboratory level. In this technique, a cyclic thermal load is applied to a part of the rendering mortar surface to accelerate the degradation; this part represents an external wall subjected to solar radiation. Subsequently, appropriate constraints are applied to the loaded part of the mortar to reproduce the actual degradation mechanism. Numerical simulation and experimental results support the effectiveness of the proposed accelerated degradation method. Considering the rate of decrease in the bond strength as a criterion to evaluate the durability, the influence of several known factors on the durability can be explicitly ranked. The durability assessment method can facilitate the comparison of novel solutions during the development stage.

著者

Daisuke Yamazaki Mitsuyasu Iwanami Masaaki Isa

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.18, no.8, pp.463-472, 2020-08-28 (Released:2020-08-28)

参考文献数

9

被引用文献数

4

---

The steel-plate bonding method used to reinforce concrete slabs in bridges has a long record of adoption, and has played an important role for many years. Favorable conditions have been observed with this method in periodic inspections; however, as part of durability tests, decreases in strength of the epoxy resin adhesive (which is one of its component materials) have been observed following over time outdoor exposure under standard environmental conditions. Investigations into the causes of decreased strength of epoxy resin adhesive are useful for increasing long-term durability in future infrastructure maintenance. The estimation of environmental factors that incorporate exposure conditions and the results of conducting accelerated tests revealed that the performance of epoxy resin adhesive was influenced by humidity. Additionally, decreases in strength accompanying reaction progress of epoxy resin were also observed. These results indicate that the degradation due to water absorption and the generation of internal stress due to the progress of the curing reaction of the epoxy resin are the causes of the decrease in the strength of the epoxy resin.

著者

久保田 信雄 柄川 伸一 松岡 彰 清水 徹

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.30, no.5, pp.29-43, 1992

被引用文献数

1

---

高速湾岸線の多摩川・川崎航路トンネルは沈埋工法で建設が進められている。本報告は, 沈埋函の函体, 基礎ぐい, 函体, 継手部の設計, ひびわれ制御対策, 函体製作工事, 函体艤装工事について紹介するものである。

著者

石原 猛男

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.25, no.1, pp.34-39, 1987

著者

田村 富雄

出版者

Japan Concrete Institute

雑誌

コンクリート工学

巻号頁・発行日

vol.16, no.5, pp.39-42, 1978

著者

山田 順治 寺本 秀男 塚山 隆一

出版者

Japan Concrete Institute

雑誌

コンクリートジャーナル (ISSN:00233544)

巻号頁・発行日

vol.10, no.1, pp.47-64, 1972

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本論文の筆者山田, 寺本, 塚山の3氏は, 昭和46年5月土木学会総会において「急速施工を目途とした特殊セメントの開発ならびに実用化」の業績により, 吉田賞を受賞された。本誌ではすでに, 新材料新工法委員会が「アサノスーパーベロセメント超早強ボルトランドセメトント」 (1970年8月号) として紹介しており, 今回はこの新しいセメントの開発の経過と利用とをくわしく紹介するために本論文を登載した。

著者

嵩 英雄

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.12, 2013-12-01

著者

Wengui Li Zhihui Sun Zhiyu Luo Surendra P. Shah

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.15, no.3, pp.110-125, 2017-03-22 (Released:2017-03-22)

被引用文献数

3 8

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We reported “Influence of Relative Mechanical Strengths between New and Old Cement Mortars on the Crack Propagation of Recycled Aggregate Concrete” in Journal of Advanced Concrete Technology, Vol. 15 (2017) No. 3 p. 110-125; doi: 10.3151/jact.15.110. After publication of the paper, we have become aware of the copyright violation from the original research. We therefore wished to retract the paper and apologize for any inconvenience caused by the retraction.

著者

藤井 孝晏 玉井 定道 西村 勝尚 志水 史典

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.33, no.4, pp.45-54, 1995-04-01

参考文献数

2

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当建物は20階建て高層RC造集合住宅である。設計基準強度600 kgf/cm2のコンクリート, SD 490の高強度鉄筋を使用し断面の縮小化・鉄筋量の削減を図った。柱・はり・床・壁の主架構を構成する部材はすべてサイト製作によるPCa部材とし, はり主筋を柱はり接合部内において接合する極めてPCa化率の高い構・工法を開発し, 実用化した。その結果, 省力化・省資源・工期短縮・高品質化が図れた。<BR>本稿では, 建物概要, 高強度材料を用いたサイト製作PCa部材の設計と構・工法および高強度コンクリートに関する施工と品質管理について報告する。

著者

池田 光次 大部薗 和久 岡田 滋夫 西本 好克

出版者

Japan Concrete Institute

雑誌

コンクリート工学

巻号頁・発行日

vol.38, no.10, pp.35-40, 2000

被引用文献数

1

著者

Nolan Wesley Hayes Qiang Gui Ammar Abd-Elssamd Yann Le Pape Alain Benjamin Giorla Sihem Le Pape Eric R. Giannini Zhongguo John Ma

出版者

Japan Concrete Institute

雑誌

Journal of Advanced Concrete Technology (ISSN:13473913)

巻号頁・発行日

vol.16, no.4, pp.179-190, 2018-04-26 (Released:2018-04-27)

参考文献数

41

被引用文献数

23

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A large-scale testing program on alkali silica reaction (ASR)-affected concrete structural members without shear rein-forcement representative of structural members found in nuclear power plants is presented. Three concrete specimens, designed to experience a free expansion rate of approximately 0.15% per year were fabricated and placed within a controlled environmental chamber (38 ± 1°C (100 ± 2°F) and 95 ± 5% relative humidity (RH)). Sixty-four (64) embed-ded transducers and twelve (12) long-gauge fiber-optic sensors provide evidence of strong anisotropic expansion and oriented ASR-induced cracking resulting from the confinement effect caused by the reinforcement layout and addi-tional structural boundary conditions. Surface cracking is not indicative of internal ASR-induced damage/expansion.

著者

加藤 昌二

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.7, pp.571-577, 2013-07-01

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晴海二丁目マンションC1街区新築工事は,湾岸エリアに建つ超高層免震マンションで,C2街区と合わせたツインタワーマンションの第1期として計画されたものである(図-1)。今回の超高層免震マンションの施工は,建物を構成する要素それぞれが,「日本一」であったり「日本初」であったりと,その計画と施工は大変に難易度の高い工事であった。我々が模索した,この工事における「最適化施工」の内容を,躯体を中心に述べる。

著者

柳田 淳一 大沼 薫春 山口 勝 山田 雅裕

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.2, pp.163-170, 2012-02-01

参考文献数

6

被引用文献数

1

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プレキャストコンクリート部材は,認定を受けたプレキャストコンクリート製造工場で製造されることから,一般に高い水準で品質が安定している。本報では,品質確保のためのプレキャストコンクリート製造工場の認定制度の概要と最近の品質管理方法の一例を示した。また,今後の建築の現場打ちRC構造物では,コンクリートのかぶり厚さの検査を電磁誘導法で測定する機会が増えることから,プレキャストコンクリート部材のかぶり厚さ検査における電磁誘導法の適用性について検討した結果を報告する。

著者

市田 弘 渡辺 俊雄

出版者

Japan Concrete Institute

雑誌

コンクリートジャーナル (ISSN:00233544)

巻号頁・発行日

vol.11, no.10, pp.17-26, 1973

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原子炉の遮蔽コンクリートとして数多い実績を持つ重量コンクリートを強力な波力の作用する灯標建設に応用した施工報告である。コンクリート構造物としての強度 (σ<SUB>28</SUB>, =180kg/cm<SUP>2</SUP>) 指定が比重指定に加わったことが, この工事を価値あるものとした。設計から施工への実験的研究で工法の成功を裏づけ, また実施工の面でも台風が急襲したことなど工法選択の安全性, 確実性を認識させた。<BR>コンクリート量は陸上打設160m<SUP>3</SUP>, 海上打設110m<SUP>3</SUP>であり, コンクリートはすべてプレパクト工法によって施工した。<BR>ブイ標識から灯標に変わり航路確保, 光源保守が非常に安全かつ容易になった。