• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.503-506
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• 2005

Recently, corrosion of reforcement of reinforced concrete structures and carbonation is raised problem of durability because of exhaustion of river sand and rapid increase of sea sand and also, concrete structure of sea environment is attacked to combined deterioration according to penetration of chloride ion and carbonation, change of temperature, repetition of dryness and wetness. Therefore, In this study, data base were presented to solve the problem about using sea sand to concrete structure situated in combined deterioration environment by exposuring concrete specimen contained chloride ion under the individual and combined deterioration.

• 콘크리트학회논문집
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• 제12권5호
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• pp.69-80
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• 2000

This paper presents the prediction of remaining service life of the concrete due to steel corrosion caused by the following three cases; carbonation, using sea sand and using deicing salts. The assessment of initiation period was generalized considering the existing perdiction models in the literature, corrosion experiment and field assessment. To evaluate the prediction equation of rust growth, the corrosion accelerating experiments was performed. The polarization resistance was measured by potentiostat and the conversion coefficient of polarzation resistance to corrosion rate was determined by the measurement of real mass loss. Chloride content, carbonation, cover depth, relative humidity, water-cement ratio(W/C), and the use of deicing salts were taken into account and the resulting prediction equation of rust growth was proposed on the basis of these properties. The proposed equation is to predict the rust growth during any specified period of time and be effective in particular for predicting service life of concrete in the case of using sea sand.

• Ocean and Polar Research
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• 제40권2호
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• pp.69-75
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• 2018

We investigated the effects of environmental variations on the growth and survival rate of Stichopus japonicus to determine the optimum environmental conditions for its growth. Literature studies and a 12 month-long diver survey were carried out to understand the habitat, ecology and size of the surveyed area. Based on the collected data, we suggested optimum habitat conditions for releasing S. japonicus. Experiments on releasing S. japonicus were conducted in the breakwater of the Hwagye fishing cooperative in Hwagey-ri, Namhae-un, Gyeongsangnam-do, Korea. To implement the experiments, we divided the surveyed area into 4 sub-areas with different characteristics: (1) sand and silt zone; (2) artificial sea cucumber bank zone; (3) artificial rock bank zone; and (4) marine algae zone. The experiment lasted for 12 months. We released 32,000 sea cucumbers over $120m^2$ of each of the sand and silt zone, artificial rock bank zone and marine algae zone and released 6,000 sea cucumbers over $120m^2$ of the artificial sea cucumber bank zone. The average density of the released sea cucumbers from day 30 to day 360 after the releasing was conducted was the highest in the artificial sea cucumber bank zone ($23.7animal/m^2$), which was followed by artificial rock bank zone ($2.0animal/m^2$), marine algae zone ($1.9animal/m^2$) and sand and silt zone ($0.8animal/m^2$). The analysis on growth showed that the initial average weight of 2.3 g increased on day 360 after the releasing to 12.5 g in the artificial sea cucumber rank zone, 20.2 g in the sand and silt zone, 23.3 g in the artificial rock bank zone and 22.9 g in the marine algae zone. Results from the experiment along with the literature analysis suggest the following optimum habitat conditions: $10-15^{\circ}C$ water temperature; 28-34 psu salinity; 5-10 m water depth; 0.2-0.5 m/s velocity; rock, stone and muddy sand as substrate; and less than 20% mud in the substrate.

• 한국방재학회 논문집
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• 제8권2호
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• pp.105-110
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• 2008

Flowable fill is generally a mixture of sand, fly ash, a small amount of cement and water. Sand is the major component of most flowable fill with waste materials. Various materials, including two waste foundry sands(WFS), an anti-corrosive waste foundry sand and natural soil, were used as a fine aggregate in this study. Natural sea sand was used for comparison. The flow behavior, hardening characteristics, and ultimate strength behavior of flowable fill were investigated. The unconfined compression test necessary to sustain walkability as the fresh flowable fill hardens was determined and the strength at 28-days appeared to correlate well with the water-to-cement ratio. The strength parameters, like cohesion and internal friction angle, were determined for the samples prepared by different curing times. The creep test for settlement potential was conducted. The data presented show that by-product foundry sand, an anti-corrosive WFS, and natural soil can be successfully used in controlled low strength materials(CLSM), and it provides similar or better properties to that of CLSM containing natural sea sand.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3719-3725
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• 2012

최근, 건설공사의 급증으로 인한 양질의 하천모래의 고갈로, 콘크리트용 대체골재로서 바다모래, 부순모래 및 순환잔골재 등의 사용이 증가하고 있다. 그러나, 미세척 바다모래는 함유된 염화물로 인하여 철근콘크리트 구조물에 사용할 경우, 철근부식 유발로 구조물의 내구성에 악영향을 미치고, 부순모래는 미립분이 많고 입도조정이 어려워서 철근콘크리트 구조물에 널리 사용되지 못하고 있는 실정이다. 한편, 낙동강 세사는 낙동강 중 하류에 대규모로 분포하고 있고, 입도를 제외하면 콘크리트용 잔골재로서 품질이 우수하므로 이에 관한 연구가 시급히 요구되고 있다. 따라서 본 연구의 목적은 콘크리트 잔골재로서 낙동강 세사를 적극적으로 활용하기 위하여 그것의 물성을 평가하는 것이다. 이를 위하여 낙동강 본류 대표위치별로 시료를 채취하여 이들의 절건밀도, 입도, 단위용적질량 등의 물성을 평가하였는데, 그 결과 낙동강 세사는 입도를 제외하면 잔골재로서의 물성이 우수한 것으로 나타났다.

• 한국지구과학회지
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• 제44권4호
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• pp.264-274
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• 2023

The Korea Strait comprises a continental shelf in a shallow sea that experienced glacio-eustastic sea-level changes during the Quaternary period. A long core of 76.6 m in length was acquired at the South Sea Drilling Project site (SSDP-101; 34°19.666'E and 128°16.335'N) with a 60 m water deep. The uppermost massive sand beds were interpreted as sandy sediments of the nearshore marine sand ridge in the shallow sea during the transgression of sea level, whereas the lower parts of alternating sandy and muddy beds were interpreted as deposits in marsh, estuary, and tidal flat environments. A three-layered geoacoustic model was reconstructed for the sedimentary succession in the high-resolution seismic profile based on a 140-grain size and sediment type of core SSDP-101. For the actual underwater simulation and experiments, the in-situ P-wave speeds were calculated using the sound speed ratio of the Hamilton method.

• 한국수산과학회지
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• 제31권5호
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• pp.609-621
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• 1998

1. 연구지역내 sand ridge들은 10$\~$20 m 높이의 비대칭형태이며, 등수심선과 평행하게 발달해 있고, sand ridge의 경사진 부분에서는 지역에 따라 sand wave 형태의 이미지가 나타나는 것으로 보아 현재 다소 활동성이 있는 것으로 보인다. 2. Ridge 주변 위치별 입도, 물리적 성질, 음파전달속도 값은 차이가 크지 않았는데, 이것은 본 연구지역의 주 퇴적상인 사질의 퇴적층이 판의 형태로 넓게 분포하고 있기 때문이다. 3. 코어 하부에는 해수면이 상승하면서 생성된 transgressive sand sheet 퇴적상의 특징을 지시하는 40$\~$200cm 두께의 자갈, 패각편, 조립사가 혼재된 퇴적상이 나타난다. 이들 사질의 분급이 양호하지 않은 이유는 해수면이 상승하면서 조류나 고에너지 환경에서 재동(reworking)되어 퇴적된 palimpsest와 관련된 것으로 사료된다.

• 한국대기환경학회지
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• 제20권2호
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• pp.143-151
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• 2004

The chemical composition of PM$_{2.5}$ was measured at Gosan, Jeju for two weeks each in November 2001 and spring 2002. In the latter part of the measurement period of November 2001, designated as the polluted period in this work, secondarily formed ion components as well as primarily emitted elemental carbon were high. PM$_{2.5}$ mass concentration was also high in this polluted period compared with the yellow sand period, in which daily average of PM $_{10}$ peaked up to 520 $\mu\textrm{g}$/㎥. Increase of major components of anthropogenic origin in the polluted period was not correlated with the variation in sea salt components while increase of crustal components in the yellow sand period was highly correlated with the variation in sea salt components. Trace elements were generally higher in the yellow sand period; however, toxic heavy metals such as zinc, cadmium and lead were the highest in the polluted period.d.d.d.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.597-600
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• 1999

Recitly, the use of sea-sand is increasing in the construction due to the rapid reduction of river-sand. In that case, one of the major problem is that a sand salt in sea-sand induce the corrosion of embedded reinforcing bar in concrete. In addition, the deterioration of concrete quality arises a social problem in the durability of reinforced concrete. This research is aimed at providing the data for the control of design method of repair and rehabilitation in the reinforced concrete structure by means of the evaluation of structural performance due to corrosion.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.153-159
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• 1999

The objective of this study was to investigate the bond strength properties of antiwashout underwater concrete. The fine aggregate(river sand, blended sand (river sand : sea sand = 1 : 1), condition of cast and cure(sea water, fresh water), and compressive strength of proportion(210kgf/$\textrm{cm}^2$ ~ 330kgf/$\textrm{cm}^2$) were chosen as the experimental parameters. The experimental results show that the underwater segregation resistance was increased, but flowability (slump flow) and air contents were decreased as the compressive strength of proportion increased. Bond strength of antiwashout underwater concrete was similar to plain concrete. From this study, rational analytic formula for the modulus of rupture and bond stress are to be from compressive strength of concrete.