巻号一覧
46 巻 (2007)
- 4 号 p. 194-
- 3 号 p. 147-
- 2 号 p. 105-
- 1 号 p. 3-
46 巻, 2 号
選択された号の論文の5件中1～5を表示しています
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丸 章夫2007 年 46 巻 2 号 p. 105-111
発行日: 2007/06/04
公開日: 2011/09/20
ジャーナル フリーMany types of unusual cracking occurs in concrete structures containing calcareous aggregates such as limestone or coral reef, but few studies have been conducted on these phenomena.
It has previously been reported that this unusual occurence of cracking in concrete is due to an alkali-carbonate or an alkali-silica reaction which is derived from limestone containing fine clay or silica. However, the calcareous aggregates are produced in Japan contain a small amounts of silica and there are few dolomitic limestone deposits in Japan.
A mineralogical study was therefore conducted on cracked concrete structure contained calcareous aggregates. The results indicated following common characteristics:(1) A large quantity portlandite cement mineral was formed.(2) Cement minerals such as 3CaO·Al2O3·8-12H20 or 4CaO·Al2O3. 3H2O were formed.(3) In cases where of 4CaO·Al2O3·3H2O appeared, gel filled cracks or air babbles were observed.(4) The components of gel, filled cracks and air babbles in concrete originated from within the cement. The gel was a biproduct of a reaction with in cement, and was not responsible for the cracking of concrete by swelling.
It is thought that cracking in concrete contaning calcareous aggregates is caused by swelling, which is due to the formation of large amounts of portlandite and calcium alminate hydrate. It is also thought that this unusual reaction is related to the powder grade of the cement, the water: cement ratio in the concrete or inadequate curing during concrete placement. This study is on going and the results of which will be reported in the near future.抄録全体を表示PDF形式でダウンロード (9494K) -
中西 亮介, 和田 信一郎, 鈴木 正哉, 犬飼 恵一2007 年 46 巻 2 号 p. 112-119
発行日: 2007/06/04
公開日: 2011/09/20
ジャーナル フリーImogolite is a unique tubular aluminum silicate having Si/Al molar ratio of 0.5. The external and internal tube diameters of imogolite are approximately 2.0 nm and 0.5 to 1.0 nm, respectively. The length of the tube ranges from a few dozen nm to a few 4 m. Because imogolite has not only large specific surface area but also high adsorption capacity and high affinity for water, it is expected to be used as heat exchange material and desiccant. Imogolite, however, doesn't exist in abundance in nature, so it must be artificially synthesized much before it is used as industrial materials.
We prepared concentrated instantaneously mixed solutions from sodium orthosilicate and aluminum chloride solutions. Al concentration of these solutions was 100 mmol L-1. Instantaneously mixed solutions were dialyzed for some dozen hours and heated in glass centrifuge tube with reflux condensers at around 100°C for 120 h. We obtained appreciable amount of imogolite from dialyzed solutions. Al concentration of the starting inorganic solution is the highest to yield imogolite.
We also heated instantaneously mixed solution without dialysis at 100°C for 144 h in erlenmeyer flasks with reflux condensers heterogeneously and homogeneously. The former heating condition gave near-translucent gel and the latter gave white dense precipitate. We found that more than 90% Si and 80% Al in the initial mixed solutions were incorporated into the both precipitates and the Si/Al ratios of the products were from 0.54 to 0.56. The XRD patterns and FTIR spectra were similar. These precipitates gave broad XRD peaks at 3.4 and 2.2 Å, slight peak at around 22 and 12 Å. The FTIR spectra showed broad and strong bands at 965, 570 and 430 cm-1. TEM observation showed that these products consisted of very fine solid particles and they formed spherical and semispherical aggregates.抄録全体を表示PDF形式でダウンロード (5260K) -
1. 分散液における導電率と粘度の関係鈴木 啓三, 佐藤 努, 米田 哲朗, 榎戸 洋之2007 年 46 巻 2 号 p. 120-130
発行日: 2007/06/04
公開日: 2011/09/20
ジャーナル フリーMontmorillonite samples were obtained from the suspension of Yamagata-bentonite with four purification processes to investigate underlying conditions which cause their viscosity. The samples were also treated repeatedly by 70% 2-propanol solution with different times to prepare the samples with different amounts of water soluble salts. Moreover, the treatments with sodium acetate-acetic acid solution (pH:5.0) and NaCl solution were conducted to dissolve Ca-carbonate minerals and to homo-ionize the samples. Electrical conductivity (relating to the amount of water soluble salts) and viscosity of the montmorillonite suspensions were measured for the samples with different pre-treatments. From the results of measurements, the following conclusions were obtained. 1. Viscosities of the montmorillonite suspension are negatively correlated with their electrical conductivities. Under the higher content of water soluble salts (higher electrical conductivity), viscosity of the samples is lower. 2. In the salt concentration of 2.5×10-6-2.5×10-4moll -1, zeta-potentials of the samples are almost constant. 3. Even under the same content of water soluble salts, the obvious difference in viscosity of the samples with four purification processes was observed. The order of viscosity among the samples was not changed even after treatments with sodium acetate-acetic acid solution (pH: 5.0) and Na C1 solution. Consequently, the difference in the viscosity, therefore, may not arise from the external chemical conditions such as content of water soluble salts and species of exchangeable cation. 4. The observed difference in viscosity among the samples would be attributed to the difference in aspect ratios or particle sizes (sizes in a-b plane) of montmorillonite in the samples with different purification processes.抄録全体を表示PDF形式でダウンロード (1549K) -
鬼形 正伸2007 年 46 巻 2 号 p. 131-138
発行日: 2007/06/04
公開日: 2011/09/20
ジャーナル フリーPDF形式でダウンロード (4484K) -
2007 年 46 巻 2 号 p. 139-
発行日: 2007/06/04
公開日: 2022/04/22
ジャーナル フリーPDF形式でダウンロード (689K)
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