• Title/Summary/Keyword: Ground seawater

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Seawater Attack Resistance of Mortars Containing Mineral Admixtures (광물질혼화재 혼합 모르타르의 해수침식 저항성)

  • 문한영;이승태;최강식
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.527-530
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    • 2002
  • In the present study, immersion test using artificial seawater was performed to evaluate the resistance of mortar specimens with or without ground granulated blast-furnace slag (SG) and fly ash (FA). Another variable was the fineness levels of SG (4,450, 6,000 and 8,000 ㎠/g). From the results of the immersion test for 270 days of exposure, the excellent resistance to seawater attack for SG mortar mixtures, especially in a high fineness levels, was confirmed. However, the reductions in compressive strength of FA mortar specimens was similar to those of OPC mortar specimens irrespective of replacement of FA.. In order to understand the deterioration mechanism due to seawater attack, X-ray diffraction (XRD) analysis were also carried out. Some reactants such as ettringite, gypsum, brucite and Friedel's salt were possibly detected through XRD technique.

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Freeze-Thaw Resistance of Blended Cement Concrete using Seawater (해수를 사용한 혼합시멘트계 콘크리트의 동결융해 저항성)

  • 문한영;김성수;이승태;김종필;박광필
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.725-730
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    • 2002
  • The durability of concrete involves resistance to freeze-thaw action, corrosion, permeation, carbonation, chemical attack and so on. Generally, properties of concrete have been well understood under the separate action of these deterioration mechanisms. However, in practice, the degradation of concrete usually is the result of combined action of physical and chemical attack and can be accelerated by the combined action of several deterioration mechanisms. In the present study, to evaluate the combined deterioration by freeze-thaw action and seawater attack, ground granulated blast-furnace slag or silica fume concrete with water or seawater as mixing water was exposed to 210 cycles of freeze-thaw action. Tests were conducted to determined the relative dynamic modulus of elasticity and compressive strength. Furthermore, The XRD, SEM and EDS analysis were performed on the deteriorated part of concrete due to freeze-thaw action and seawater attack.

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Freeze-Thaw Resistance and Void Characteristic of Blended Cement Concrete using Seawater (해수를 사용한 혼합시멘트계 콘크리트의 동결융해 저항성 및 공극특성)

  • Kim, Seong-Soo;Lee, Seung-Tae;Jung, Ho-Seop;Park, Kwang-Pil
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.589-592
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    • 2006
  • The durability of concrete involves resistance to freeze-thaw action, corrosion, permeation, carbonation, chemical attack and so on. Generally, properties of concrete have been well understood under the separate action of these deterioration mechanisms. However, in practice, the degradation of concrete usually is the result of combined action of physical and chemical attack and can be accelerated by the combined action of several deterioration mechanisms. In the present study, to evaluate the combined deterioration by freeze-thaw action and seawater attack, ground granulated blast-furnace slag or silica fume concrete with water or seawater as mixing water was exposed to 300 cycles of freeze-thaw action. Tests were conducted to determined the relative dynamic modulus of elasticity and compressive strength. Furthermore, The MIP analysis were performed on the deteriorated part of concrete due to freeze-thaw action and seawater attack.

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Crevice Corrosion Resistance of Stainless Steels in Natural Sea Water with different Post Welding Treatment

  • Lee, Y.H.;Kim, Y.H.;Kim, H.
    • Corrosion Science and Technology
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    • v.2 no.5
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    • pp.219-224
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    • 2003
  • Crevice corrosion of stainless steels in natural seawater was investigated for several post weld treatments; as-annealed, as-welded, pickled, and ground. The results confirmed the effect of the biofilm on the cathodic reaction leading to an ennoblement of the rest potential. The degree of ennoblement of corrosion potential depends on the surface finish. As-annealed and pickled samples show stable corrosion potential approaching to 200 ~ 300 mV (SCE) while as-welded and ground samples show the fluctuating corrosion potential. This points to a situation where there are conflicting effects determining the trend in free corrosion potential. Crevice corrosion initiation will tend to pull the free corrosion potential in the active direction, whereas the presence of biofilm will tend to ennoble corrosion potential. There was no visible attack on UNS S31803, S32550, and 2205W. Therefore, those stainless steel grades appeared to be resistant to crevice corrosion in natural seawater on condition of weld metal.

Application of electromagnetic methods to the investigation of seawater intrusion into coastal aquifer - A case study in the Hasunuma area, Chiba Prefecture, Japan

  • Mitsuhata Yuji;Uchida Toshihiro
    • 한국지구물리탐사학회:학술대회논문집
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    • 2003.11a
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    • pp.335-339
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    • 2003
  • The estimation of seawater intrusion into deep aquifers has been becoming an important subject in terms of site characterization for geological disposal of radioactive waste. Conventional direct-current resistivity methods have been used for ground water explorations and recently have been applied to environmental problems. However, electromagnetic methods are more practical and useful for such a deep investigation. We consider audio-frequency magnetotelluric (AMT) and surface-to-borehole electromagnetic (EM) tomography methods as promising tools for the investigation of deep aquifer. These methods were tested in the Hasunuma area, Chiba Prefecture, Japan. Although the study area is in an urban area, high-quality AMT data were acquired, which was mainly accomplished by night-time data recording and remote-reference data processing. One-dimensional inversion results of the AMT data revealed two extremely conductive zones, which is consistent with the electrical conductivity profile of pore water in core samples. It can be interpreted as the seawater intrusions into both zones. However, the chemical analysis of the groundwater sampled in the deep zone suggests that this groundwater must be fossil seawater that had been confined during sedimentation processes. In addition, the permeability coefficient of the deep layer is very low. Thus the deep conductive zone corresponds to the fossil seawater regarded as being difficult to flow.

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Evaluation on Surface Scaling and Frost Resistance for concrete Deteriorated due to Cyclic Freezing and Thawing with Inherent Chloride

  • Kim, Gyu Yong;Cho, Bong Suk;Lee, Seung Hoon;Kim, Moo Han
    • Corrosion Science and Technology
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    • v.6 no.4
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    • pp.177-185
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    • 2007
  • The purpose of this study is to evaluate freezing-thawing and surface scaling resistance in order to examine the frost durability of concrete in a chloride-inherent environment. The mixing design for this study is as follows: 3 water binder ratios of 0.37, 0.42, and 0.47; 2-ingredient type concrete (50% OPC concrete and 50% ground granulated blast-furnace slag), and 3-ingredient type concrete (50% OPC concrete, 15% fly ash, and 35% ground granulated blast-furnace slag). As found in this study, the decrease of durability was much more noticeable in combined deterioration through both salt damage and frost damage than in a single deterioration through either ofthese; when using blast-furnace slag in freezing-thawing seawater, the frost durability and surface deterioration resistance was evaluated as higher than when using OPC concrete. BF 50% concrete, especially, rather than BFS35%+FA15%, had a notable effect on resistance to chloride penetration and freezing/expansion. It has been confirmed that surface deterioration can be evaluated through a quantitative analysis of scaling, calculated from concrete's underwater weight and surface-dry weight as affected by the freezing-thawing of seawater.

Characteristics on the distribution of salinity of airborne sea salt by height (높이에 따른 비래염분량의 감소 특성)

  • Lee Jong Suk;Choi Won Sung;Kim Do Gyeum;Moon Han Young
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.261-264
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    • 2005
  • For concrete structures immersed in seawater, the concentration of chloride used to estimate the chloride diffusion coefficient can be defined as the seawater chloride concentration. However, for seashore concrete structures which are not coming into direct contact with seawater, establishing the interface concentration of chloride becomes delicate. In addition, concrete structures are greatly affected by salt attack primarily due to airborne sea salt like it can be seen through the corrosion of rebar. This study intends to investigate characteristics on the salinity of airborne sea salt by height. Salinity measurement devices were installed at height of 2, 10 and 19m on the seashore water tower located in the area of Samchuk in the Eastern coast. Analysis results of the decrease of salinity with respect to the height above the ground at a distance of 30m from the seashore showed that the reduction reached about 40$\%$ at a height of 10m and 60$\%$ at 20m.

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Determination of an Underground Seawater Flow Using a TEM Decay Curve (TEM감쇠곡선을 이용한 해수의 지하 유동현상 파악)

  • 황학수;문창규;이상규;이태섭
    • Economic and Environmental Geology
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    • v.34 no.5
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    • pp.499-506
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    • 2001
  • The geophysical monitoring technique using the high resolution time-domain electromagnetic (TEM) method with a coincident loop away was applied for determination of an underground seawater flow in the coastal areas. In comparison of the TEM monitoring to direct current (DC) resistivity monitoring, the TEM response to the under ground seawater flow is less sensitive than the DC resistivity response. However, the TEM monitoring is more effective in terms of measuring time, survey expense, and real-time data processing than the DC monitoring thor evaluating the spatial distribution of the fresh water-seawater transition zone in a regional area.

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Evaluation of dynamic behaviors of gravity-based structures under seismic load considering fluid-structure-ground interactions

  • Hyo-Jin Kim;Sunghun Jung;Seongpil Cho
    • Structural Engineering and Mechanics
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    • v.88 no.3
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    • pp.251-262
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    • 2023
  • This paper presents a method for assessing the dynamic responses of gravity-based structures (GBS) under various seismic loads, with a focus on fluid-structure-ground interactions. Models of GBSs and their surrounding environments were developed, incorporating interaction effects among the structure, seawater, and seabed. Dynamic responses of the GBS subjected to three seismic loads-Chi-Chi, Northridge01, and Northridge02-were calculated, with consideration of both horizontal and vertical accelerations, as well as displacements. Parametric studies indicated that the primary factors affecting the dynamic responses of GBS were seismic loads characterized by significant input forces and accelerations. The frictional force on the ground had minimal impact on the horizontal and vertical displacements of the GBS. Weight emerged as a critical factor in anchoring the GBS to the ground and minimizing vertical accelerations and displacements.

Physical and chemical analyses of ground-water by impacts of tunneling at coastal urban region in Busan (부산시 해안 인근 지역에서의 터널 굴착에 따른 지하수 거동 영향 평가)

  • Kim, Hyoung-Soo;Lee, Ju-Hyun;Ahn, Ju-Hee;Jeong, Ui-Jin;Kim, Jun-Mo;Yoon, Woon-Sang;Chung, Sang-Yong;Lee, Jin-Moo;Woo, Sang-Woo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.457-464
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    • 2005
  • In the case of tunneling, the equilibrium state of hydro-geologic environments destroy and change abruptly in some section of whole works. Specially, it's very possible for seawater to intrude toward the site of tunnel if the field is nearly located in a costal region. In this study, we have evaluated the mechanism related between groundwater flow and seawater intrusion that by impacts of tunneling. Various hydro-geological field tests have performed for getting four representative hydrogeologic properties of geologic formations such as transmissivity (T), storativity(S), longitudial dispersity(${\alpha}_L$), and effective porosity($n_e$). For the effect of tunneling, the numerical model was first simulated based on the governing equation of groundwater flow. The results showed that the maximum drawdown was 17.2m and the total inflow into the tunnel had the range from 0.48 to $3.63m^3/day/m$. Secondly, the three dimensional numerical model was analyzed to investigate a characteristic of seawater intrusion based on the previous simulated results of groundwater flow. The results showed the seawater moved as the range of $200{\sim}220m$ from the initial interface between seawater and groundwater toward the tunnel.

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