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| 1.
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鳥居, 和之 ; 川村, 満紀 ; Torii, Kazuyuki ; Kawamura, Mitsunori
概要:
金沢大学理工研究域環境デザイン学系<br />Recently, chemical soil stabilization are actively adopted for the improvement of the soft ground
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on which roads or buildings will be constructed. In addition to traditional stabilizers of Potland cement and lime, the industrial by-products such as fly ash and pulverized blastfurnace slag are also used for the purpose of increasing the effectiveness of cement and lime as a stabilizer and their effective utilization in soil stabilization. The objective of this study is to reval the mechanisms of strength development of the compacted stabilized soils from a microstructural view-point. The compressive strength, modulus of deformation and pulse velocity of various compacted soils stabilized with cement, lime and lime-fly ash (or pulverized blastfurnace slag) were measured. Their microstructures were also characterized by the SEM observation and pore size distributions obtained by the mercury intrusion porosimeter. The relationships between strength and changes in microstructure in compacted stabilized soils are discussed.
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| 2.
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HA, Tuan Minh ; Fukada, Saiji ; Torii, Kazuyuki ; 深田, 宰史 ; 鳥居, 和之
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金沢大学理工研究域環境デザイン学系<br />Structural responses have been used as inputs in the evaluation procedures of civil structures fo
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r years. Apart from the degradation of a structure itself, changes in the environmental conditions affect its characteristics. For adequate maintenance, it is necessary to quantify the environment-induced changes and discriminate them from the effects due to damage. This study investigates the variation in the vibration responses of prestressed concrete (PC) girders, which were deteriorated because of the alkali-silica reaction (ASR), concerning ambient temperature and humidity. Three PC girders were exposed to outdoor weather conditions outside the laboratory, one of which had a selected amount of fly ash in its mixture to mitigate the ASR. The girders were periodically vibration tested for one and a half years. It was found that when the temperature and humidity increased, the frequencies and damping ratios decreased in proportion. No apparent variation in the mode shapes could be identified. A finite element model was proposed for numerical verification, the results of which were in good agreement with the measured changes in the natural frequencies. Moreover, the different dynamic performances of the three specimens indicated that the fly ash significantly affected the vibrations of the PC girders under ASR deterioration. © 2017 Tuan Minh Ha et al.
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| 3.
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Ha, Tuan Minh ; Fukada, Saiji ; Torii, Kazuyuki ; 深田, 宰史 ; 鳥居, 和之
概要:
金沢大学理工研究域環境デザイン学系<br />In the Hokuriku region, alkali-silica reaction (ASR) caused severe degradations in many concrete
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bridges. However, criteria for repair and replacement works of these structures are still unclear. For the development of damage evaluation procedure, it is necessary to investigate the load-carrying capacity of prestressed concrete (PC) girders affected by ASR-induced deterioration in actuality. This study constructed two full-size PC specimens from the high-early-strength Portland cement and reactive aggregates, and then exposed them to outdoor environmental conditions. One of them was specially mixed with a controlled amount of fly ash. After one and a half years of outdoor exposure, destructive loading tests were carried out to investigate the difference in loading capacity of the girders. From results of the long-term exposure and the tests, the flexural strength and the rigidity of the specimen with fly ash were not degraded while ASR was also effectively suppressed. In addition, cylindrical concrete cores were taken at different positions of both girders to analyze the relationship between mechanical properties of concrete such as compressive strength, static elastic modulus, and ultrasonic wave propagation speed. Results of the coring test showed that the mechanical properties of concrete cores varied according to their collecting positions and directions. © 2017 Japan Concrete Institute.<br />出版者照会(事後報告)
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| 4.
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鳥居, 和之 ; 川村, 満紀 ; 枷場, 重正 ; 五十嵐, 心一 ; Torii, Kazuyuki ; Kawamura, Mitsunori ; Hasaba, Shigemasa ; Igarashi, Shinichi
概要:
金沢大学理工研究域環境デザイン学系<br />In the regions of the cold weather, the deterioration of the subbase in roads by freezing-thawing
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action is often observed. Although the durability of stabilized soils is considered to be important, the evaluation of the resistibility of stabilized soils against freezing-thawing cycles has been little established in general. The purpose of this study is to evaluate the resistibility of the various stabilized soils against freezing-thawing cycles in terms of the compressive strength of the stabilized soils undergoing freezing-thawing cycles. The relationship between the resistibility against the freeezing-thawing cycles and the microstructure in the stabilized soils is discussed on the basis of the pore size distributions.
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大代, 武志 ; 鳥居, 和之
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広野, 真一 ; 鳥居, 和之
概要:
Volcanic rocks such as andesite have popularly been used for aggregates in the Hokuriku District. Therefore, the andesit
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ic aggregates have contributed to a steady occurrence of alkali-silika reaction (ASR) in concrete. Taking into account the effective utilization of local materials, so-called “Chisan-chisho”, both the reduction in the environmental impact and the rationalization of natural resources, positive countermeasures for mitigating ASR by using blended cements with fly ash (FA) or blast-furnace slag (BFS) are most expected. This paper examines the mitigating effects of mineral admixtures on ASR of mortars by the accelerated mortar-bar test (ASTM C 1260). As the result of test, the replacement with FA or BFS at normal percentages recommended by JIS A 5308 decreased significantly the expansion of mortar bars using reactive andesitic aggregates in the Noto peninsula. Especially, a high-quality fine FA produced in the Hokuriku District is hopeful in its practical use of concrete mixtures. Furthermore the ASR mitigating effects by mineral admixtures are assessed with a good performance by the test method “ASTM C 1260”.
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奥山, 和俊 ; 鳥居, 和之
概要:
A large number of bridge piers in Japan, which were mostly constructed in the 1970s or 1980s, are suffering from serious
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damages caused by alkali-silica reaction (ASR). The concrete using reactive andesite successively expanded for more than 30years, leading to the serious damage of structural elements of bridge pier. In the case study of Kashima Bridge in Ishikawa Prefecture, the degree of deterioration of bridge pier due to ASR was investigated by both visual inspection of cracking and non-destructive testing. Furthermore, the mechanical properties of concrete and the degree of fracture of steel bars were examined for the purpose of strengthening design of bridge pier. Based on the classification of ASR deterioration level of each element, the steel plate bonding was adopted for the column, after the pillow beam had been totally reconstructed. This paper describes the mineralogical properties of reactive andesite used in concrete and the mechanical properties of concrete cores taken from bridge pier. Furthermore, monitoring and strengthening methods applied for Kashima Bridge pier are introduced together with non-destructive testing by means of ultrasonic wave inspection. In the maintenance of this bridge, a monitoring using crack sensors has been successfully applied in order to ensure the daily safety of bridge. ©2008 The Society of Materials Science, Japan.
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湊, 俊彦 ; 鳥居, 和之
概要:
There exist large numbers of ASR-deteriorated bridges on the Noto expressway through the center of Noto peninsula in Ish
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ikawa Prefecture. In some serious cases, a very severe deterioration which appears to directly be related with the reduction in load carrying capacity of structures has occurred; the significant decrease in compressive strength of concrete, the loss in bonding strength around steel reinforcement, and the fracture of steel reinforcement at the bent and so on. This study aims at investigating both the mix proportions of concrete and the rock type of reactive aggregates used in ASR-deteriorated bridges. Furthermore, the relationships between mechanical properties of cores taken from various portions of bridge pier and ASR degradation ranks classified by the various inspection were discussed for the purpose of the diagnosis and maintenance procedures of these bridges. © 2010 The Society of Materials Science. Japan.
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| 9.
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鳥居, 和之 ; 川村, 満紀 ; 枷場, 重正
概要:
Recently, chemical soil stabilizations are actively adopted for the improvement of the soft ground on which the road and the foundation for offshore structures will be constructed. The industrial by-products such as gypsum, coal ashes,
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blastfurnace slag and basic oxygen furnace slag can be used effectively for the soil stabilization. In this paper, the characteristics of soil stabilizations with various industrial by-products are discussed from the viewpoints of the types of reaction products which are responsible for the development of strength in the stabilized soils.
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鳥居, 和之
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