材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
54 巻 , 8 号
選択された号の論文の17件中1~17を表示しています
特集 建設材料
巻頭言
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論文
  • 大濱 嘉彦, 高橋 忍, 太田 将弘
    2005 年 54 巻 8 号 p. 804-809
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    For the purpose of developing the early strength of concrete, accelerated curings such as steam and autoclave curings are widely applied to the manufacture of precast concrete products. The uses of polymer-modified mortar and concrete are also expected for precast products. The objective of the present study is to examine the application of effective accelerated curings to styrene-butadiene (SBR)-modified mortars with hardener-free epoxy resin. SBR-modified mortars with a hardener-free epoxy resin are prepared with various polymer-cement ratios, subjected to a 1-d steam curing after a 1-d moist curing, followed by a 1-d heat curing, and tested for flexural and compressive strengths. As a result, (steam + heat)-cured SBR-modified mortars with the hardener-free epoxy resin at polymer-cement ratios of 15% or more develop about three times higher flexural and compressive strengths than unmodified mortar. Such high strength development is attributed to the improved microstructures of interfacial transition zone by SBR-epoxy resin modification in the mortars. The optimal accelerated curing for the SBR-modified mortars with the hardener-free epoxy resin is recommended as follows: 1-d moist [20°C, 90% (RH)] +1-d steam (90°C) +1-d heat (100 or 120°C) curing.
  • 藤井 隆史, 藤木 昭宏, 田中 秀和, 綾野 克紀
    2005 年 54 巻 8 号 p. 810-815
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Ordinary concrete structures are colorless and monotony. Therefore, they give an artificial and dreary impression. Many approaches for harmonizing concrete with surrounding landscape have been investigated. The coloring concrete is an approach to provide concrete with a favorable impression. The various highlights and contrasts of the scene may enable to readily distinguish elements from one another and to pick those that are most important to us at the moment. The pigment for coloring concrete, whose main component is iron oxide, can give any color without white and blue. The pigment whose main component is chrome oxide makes the color of concrete blue. The pigment whose main component is titanium oxide makes the color of concrete white. Furthermore, carbon black gives black color. When some types of pigment are mixed, the variation of concrete color is expected to be spread much more. In this paper, the effect of the dosage and the type of pigment on the color of concrete is discussed. The method to estimate the lightness and color shade of the color-conditioned concrete is proposed. The proposed method can be also available for the estimation of the color-conditioned concrete with several types of pigments. Normal Portland cement concrete and high volume blast furnace slag cement concrete were used for test.
  • 杉山 隆文, 福岡 弘誠, 辻 幸和
    2005 年 54 巻 8 号 p. 816-821
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Long term behavior of a bentonite sand mixture used for the disposal of radioactive wastes has been of great concern when it continuously contacts with concrete. This is explained by the fact that the characteristics of the bentonite will be altered due to the leaching of calcium ions in the concrete. In particular the Sodium type (Na type) bentonite exhibits a reduced expansion characteristic. However little research has been conducted using a bentonite-concrete composite system to investigate long term effects.
    In this present research an alteration of the characteristics of the Na type bentonite is studied by the use of a concrete bentonite composite specimen. An electrical migration method was employed to accelerate the transport of calcium ions present in the pore solution in concrete through the interface of a bentonite sand mixture. A constant DC voltage of 15 V was continuously applied to a concrete bentonite composite specimen for 50 days. Chemical analysis for cation content and expansion force, the measurements of EPMA and XRD were conducted.
  • 中本 純次, 戸川 一夫, 三岩 敬孝, 谷 敏行
    2005 年 54 巻 8 号 p. 822-827
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Authors have been studying for several years as for the effective utilization of sludge water produced in ready mixed concrete plants due to washing of a mixer, agitating truck dram etc. Nowadays, JIS A 5308 permits the usage under 3 percent as solids of sludge for the unit content of cement of new concrete. Recently, it is strongly requested to re-use a further large quantity of sludge water, in order to achieve the zero-emission. Sludge water consists of cement, fine particles of aggregate and water. All materials are one of the constituents of concrete. This study, in order to utilize the larger quantity of sludge water than that now allowed, is to verify the mix design of concretes containing sludge which has identical slump and compressive strength to comparative concrete. From the results of this study, it became clear that as for the high-range water reducer concrete containing stabilized sludge within the range of 3-15%, there was no problem about slump and compressive strength. It was possible to design the concrete of identical slump and compressive strength to comparative concrete. It was also confirmed that the bulk volume of coarse aggregate was available for the design method of concrete mixture.
  • 石丸 啓輔, 水口 裕之, 橋本 親典, 上田 隆雄, 藤田 和博, 近江 正明
    2005 年 54 巻 8 号 p. 828-833
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    In the Shikoku area, it is eager to request an alternative fine aggregate in stead of natural sand, in particular sea sand, by the reason of prohibition of borrowing sea sand in Seto Island Sea. In this study, the fundamental properties of concrete using copper slag (JIS A 5011-3) or second class fly ash (JIS A 6201) as a part of fine aggregate to apply for plain concrete structure is investigated. It is concluded that the concrete of 20 mm in coarse aggregate maximum size, 50% in water-cement ratio and 40 mm in coarse aggregate maximum size, 60% in water-cement ratio and up to 30%, except in the case of 50% in water-cement ratio of fly ash concrete is possible to 20%, at in volume percentage of sand using copper slag or second class fly ash is applicable for concrete structure.
  • ―EPMAを利用した塩化物イオン濃度分布の測定―
    松下 博通, 前田 悦孝, 藤田 数正, 祝井 健志
    2005 年 54 巻 8 号 p. 834-841
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    As a part of the research on application of blast-furnace slag to prestressed concrete, chloride ion penetration of the high strength concrete used blast-furnace slag was examined paying attention to wet curing period. Besides, in order to measure detailed distribution of the chloride ion concentration, we propose an approach with EPMA technique and it compared with the former method. As the result, concrete mixed with ground granulated blast-furnace slag increased the concentration of chloride ion near the surface of concrete, but decreased its penetration to inside. Furthermore, by EPMA technique, it is possible to compute detailed distribution of chloride ion concentration and it has checked that use of EPMA was significant in the evaluation of chloride ion concentration on the surface of concrete, while there are some errors about an absolute value.
  • 濱田 秀則, Tarek Uddin MOHAMMED, 山路 徹
    2005 年 54 巻 8 号 p. 842-849
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    A detailed investigation on 30-years old concrete specimens of 150 mm in diameter and 300 mm in height made with ordinary portland cement (OPC), high early strength portland cement (HES), moderate heat portland cement (MH), slag cement of type B (SCB), and alumina cement (AL) was carried out. In each specimen, steel bars were embedded at cover depths of 20, 40, and 70 mm. Mineralogy and microstructure of mortar portions at the inner and outer regions, coarse aggregate-mortar interface and steel-concrete interface were investigated. Carbonation depth, acid-soluble chloride contents, electro-chemical and corrosion condition of embedded steel bars were evaluated. It is concluded from the results that the microstructure of concrete at the outer region for SCB and AL becomes denser compared to the inner region. For AL, the inner region is relatively more porous and also a porous steel-concrete interface is found. Chloride ingress in concrete was lower for SCB and AL compared to OPC, HES and MH. However, more corrosion over the steel bars was found for AL. The surface condition of the steel bars embedded in concrete made with SCB remains as same as the initially polished condition. Utilization of SCB is concluded as one of the best choices to improve long-term durability of marine concrete structures.
  • 米野 現樹, 鈴木 哲也, 池田 幸史, 大津 政康
    2005 年 54 巻 8 号 p. 850-854
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Damage of concrete is quantitatively estimated by applying AE rate-process analysis and damage mechanics. Controlled-damage specimens are prepared by freezing-thawing and carbonation. AE behavior in the compression test is analyzed as the rate process. From damage mechanics, a damage parameter is estimated. Using these parameters, compression behavior in concrete is analyzed quantitatively. As a result, it is demonstrated that the degree of damage is estimated quantitatively.
  • 氏家 勲, 加藤 和教, 小西 吉満, 沼田 正人
    2005 年 54 巻 8 号 p. 855-860
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Cracks in concrete structure cause deterioration of durability due to corrosion of reinforcement. Although crack width is controlled in less than the allowable value in the present design method, concrete structure with cracks deteriorate more easily than that without cracks. The objective of this study is to develop the reinforced concrete member that a crack doesn't occur in serviceability limit state. This study gave attention to a super high strength of Reactive Powder Composite (RPC), especially a high tensile strength on crack development. RPC consists of premixed powder in selected combination of cement, silica particles, siliceous sand, special water reducing agent, and steel fibers.
    A part of tension zone in reinforced concrete beam was fortified by RPC. The cross-sectional area of RPC part was varied in three ways. Flexural load tests of beam were carried out. The crack development moment of the beams fortified by RPC increased with the increase of reinforcing area of RPC. When the bending moment that the cracks with permissible crack width for corrosion of reinforcement develop in the usual reinforced concrete beam acted, cracks didn't occur in the beams reinforced with RPC suitably. The flexural behaviours of the beam reinforced with RPC could be analysed by elastic theory in the range of service state. When the bending moment on the occurrence of the crack is estimated, the restraint stress due to autogeneous shrinkage of RPC must be taken into consideration.
  • 辻 正哲, 石川 雄志, 畑中 強志, 澤本 武博, 飯田 竜太, 岡本 大
    2005 年 54 巻 8 号 p. 861-868
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    It is important to place reinforcing bars accurately as specified on the drawing and secure bars against movement. Actually, bar positions move under the construction work even though the displacements are large or small. Therefore, the bar arrangements have to be modified to the accurate position by bending work of bars where the displacements are over the allowable tolerances. In this study, the effects of mending work of main bars on mechanical behavior of reinforced concrete members are investigated, and inadequate bending works that adversely affect the strength of concrete members are discussed. Where the main bars displaced from specified position are sharply bent to joint new bars at accurate position, main bars are cut by repetition of bending and rebending under alternative low cyclic fatigue load as a seismic load. When the main bars are bent in member which can sustain sufficient load by a wide margin as a foundation, the inclination of main bars for modification is recommended to be less than 1:5 (desirably 1:7) to ensure specified load capacity. Because larger inclinations make the rigidity of member low by pull out of main bars from base member. Modification of main bars from outside to inside to secure effective depth can be allowed even in column member by confirming the inclination for modification under 1:5, the sufficient tie bars at all plastic hinge zones extending to cross section where effective depth is modified to be specified value, the enough tie bars to prevent bent main bars which are going to be straight under force from pushing out concrete cover, and durability changed by thinner cover.
論文
  • 奥屋 和彦, 近藤 良之
    2005 年 54 巻 8 号 p. 869-874
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Earthquakes cause damages by fatigue at welded joints of steel structures. Structures which were not seriously damaged would be continuously used even after earthquakes. The fatigue strength of those structures, however, might have been decreased due to the cyclic straining during earthquake. In order to clarify the effect of large cyclic straining on the fatigue strength of the welded joint, low cycle fatigue crack propagation test under large straining as well as high cycle fatigue tests after large cyclic straining were performed on welded joint made of 780 MPa class high strength steel. Experimental results showed that the high strength steel welded joint exhibited an excellent fatigue limit characteristic in the case of reversal stressing. However, the fatigue limit is quite sensitive to mean strain. The application of positive mean strain substantially decreased the fatigue limit. Moreover, the cyclic application of large strain caused fatigue crack, which caused the substantial decrease of fatigue strength. The amount of reduction in fatigue limit was larger in the case of high strength steel compared to that in the case of low strength steel.
  • 堀川 教世, 春山 義夫, 境田 彰芳, 上田 宗輝
    2005 年 54 巻 8 号 p. 875-880
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    In this paper, tensile and fatigue properties of poly-p-Phenylene benzobisoxazole (PBO) fiber have been investigated. The tensile test was carried out with a gauge length of 12.5 mm and displacement rate of 0.5 mm/min. The tensile strength data were analyzed in terms of the Weibull probability distribution function. Fatigue test was performed using an electromagnetic force fatigue tester. The fatigue testes were carried out at a frequency of 10 Hz with three stress ratios of 0.1, 0.5, and 0.7. It was found from the tensile strength test that the distribution of PBO fiber strengths expressed as Weibull distribution function with 2 parameters. The test results clearly showed that the fatigue behavior appeared in the S-N characteristic curves. The relation between the stress amplitude and the fatigue life depended on the stress ratio. However, the relation between the maximum stress and the fatigue life was independent of the stress ratio, and the maximum stress was most suitable parameter to describe the fatigue strength at the different stress ratios. Consequently, it became clear that the fatigue strength of the PBO fibers was not cycle dependent, but is time dependent. In addition, it is found by SEM observation that there are distinct differences between the surface image of tensile test specimen and that of fatigue test specimen, i.e., the crack length in the fatigue test specimens are much longer than that in the tensile test specimens.
  • 江尻 正一, 後藤 昌英, 佐々木 敏彦, 広瀬 幸雄
    2005 年 54 巻 8 号 p. 881-886
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    The X-ray stress measurement is an effective method of nondestructive inspection for the residual stress in the surface layer of steel materials. However, the sin2ψ method, which is commonly used as X-ray stress measurement, is inapplicable to such anisotropic materials as textured materials because the theory supposes isotropic elastic polycrystalline materials as sample.
    The applicable X-ray stress measurement to textured materials was investigated on the assumption that information about each crystallite orientation was deduced by crystallite orientation distribution (ODF). Applied to measure the stress of the titanium carbide nitride (TiCN) film with the ‹111› preferred orientation, the residual stress value was determined from the measured lattice strain. The strong compressive stress value was observed in the film. Compared with methods of other models, the result indicated a small difference from the ‹111› ideal fiber texture model and was situated between the texture model and sin2ψ method.
  • 鈴木 浩治, 金原 勲, 斉藤 博嗣, 船見 国男
    2005 年 54 巻 8 号 p. 887-894
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    The primary purpose of this study is to statistically characterize the tensile strength of kenaf (Hibiscus cannabinus L.) bast fibers, which are now using for fiber-reinforcing composite materials. This paper is the first part of the present study, and reports the experimental procedures and results for geometrical measurements and monofilament tensile strength test of the kenaf bast fibers sampled from the identical portion in an individual plant. Cross-sectional geometries of the fibers, which in the mesoscopic level consist of elementary fibrous cells and inter-cell materials, were found to vary severely along and among fibers. A method to estimate cross-sectional areas of this plant fiber from their mutually-perpendicular side views was also proposed. Large variations of monofilament strength of the fibers were observed. The strength with gauge length fixed was found to be well described by the two-parameter Weibull distribution in practice, but Weibull shape and scale parameters were different from each of different gauge lengths, which may be primary due to the along-and-among geometrical variation and “mesoscopic” internal structure of the fibers.
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