• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3719-3725
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• 2012

Due to the recent shortage of well-graded river sand resulting from a rapid growth of concrete construction, sea sand, crushed sand, and etc. are increasingly used instead. It is, however, well noted that non-washed sea sand leads to corrosion of the reinforcing steel in concrete, and thus eventually results in damage to concrete. Also, the crushed sand is not being widely used, since it is difficult to maintain the allowable amount of passing 0.08mm sieve and to adjust grading. On the other hand, because the fine sand of Nakdong-River has a poor grading but good quality as a fine aggregate for concrete, it is strongly needed to investigate the fine sand as an alternative fine aggregate. Thus, the purpose of this research is to evaluate the physical properties of the fine sand of Nakdong-River to utilize it actively as a fine aggregate. For this purpose, after the sand samples were collected according to typical location of main stream of Nakdong-River, the physical properties such as density in oven-dry condition, grading, unit volume mass, and etc. of them were estimated. It was observed from the test results that physical properties of the fine sand of Nakdong-River except grading were found to be excellent.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.195-202
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• 1994

In this research, a lot of triaxial test results (CID) are analyzed to study the curvature characteristics of failure envelope of sand and parametric relationship between shear strength and state parameter by Been and Jefferies. In the conventional triaxial tests, correction for the change of sectional area of a sample and for membrane influence is essential especially in order to determine critical state (or steady state) condition more correctly. Based on the test results, a model to express the shear strength of fine sand as a function of density and stress level is presented and curvature characteristics of shear failure envelope and parametric relationship between state parameter and shear strength parameters are evaluated.

• Journal of the Korean Geotechnical Society
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• v.17 no.1
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• pp.99-107
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• 2001

일반적으로 샌드파일 설치로 인해 파일주변지반은 교란되어 스미어 영향과 배수저항에 의해 압밀지연 현상이 발생하는 것으로 알려져 있다. 특히 예민한 점성토 지반일 경우 교란정도가 크며, 틱소트로피현상이 지연될 경우 지지력 및 압축특성은 불리하게 된다. 본 연구에서는 원지반 특성이 파악된 채취시료를 이용하여 완전 교란조건에서의 실내모형시험과, 염분농도변화에 의한 실내역학시험을 실시하였다. 실내모형시험 결과 낮은 하중단계에서의 압밀계수는 비교란 시료의 특성과 유사하게 나타났으며, 염분농도 증가에 따라 일축압출강도가 증가하고 강도회복은 빠르며 압축지수는 작게 나타났다. 결과적으로 점성토지반 간극수중 염분농도는 강도증대와 압축특성 변화에 영향을 주며, 틱소트로피 증대의 영향요소가 적은 담수지반에서 샌드파일을 시공할 경우 발생하는 과다침하의 한 원인으로 여겨지는바, 이와 같은 요인은 측방유동에 의한 침하거동과 함께 고려하여야 할 영향요소로 파악되어야 할 것으로 판단된다.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.429-433
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• 2007

Cement mortar and concrete can be used as grouts but problems regarding shrinkage and the discord of coefficients of thermal expansion between grouts and HDPE pipes has to be solved. Thermal conductivities of wet condition two times larger than those of dry condition, except for pure cement mortar. The addition of sand into the cement grouts greatly increases the thermal conductivity. The addition of bentonite into the cement grouts reduces thermal conductivity thus reducing the density. Bentonite grouting must be used only below the groundwater table since bentonite grouts possesses high shrinkage property in dry condition. The addition of sand prevents the shrinkage of bentonite grouts. Bentonite manufactured in Korea can be used since they possess similar thermal conductivities with imported products. The addition of sand into the bentonite grouts greatly increases the thermal conductivity.

• Resources Recycling
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• v.8 no.1
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• pp.44-51
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• 1999

Converter slag was reduced and modified by the simultaneous addition of carbon and waste foundry sand as a $SiO_2$ source. The basic properties such as phase distribution, composition, specific density, hardness. absorption of water and compressive strength of modified slags were measured. The Iron recovery was significantly affected by the basicity of slag. The properties of slow cooled-modified slags of basicity 1.34 arc very similar to the natural aggregates.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.90-97
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• 2003

The purpose of this study is to understand the dissipation pattern of excess pore pressure after liquefaction which governs the post-liquefaction behavior of liquefied sand deposits. 1-g shaking table tests were carried out on 5 different kinds of sands, all of which had high liquefaction potentials. During the tests excess pore pressure at various depths, and surface settlements were measured. The measured curve of the excess pore pressure dissipation was simulated using the solidification theory, and from the analysis of the velocity of dissipation, the dissipation pattern of excess pore pressure after liquefaction was examined. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size ( $D_{10}$) divided by the coefficient of uniformity ( $C_{u}$), and the increase in the initial relative density of the ground played a role in shifting this correlation curve toward an increased dissipation velocity. From the correlation, an approximate method was recommended for prediction of the dissipation curve of excess pore pressure after liquefaction in saturated sand deposits.s.s.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.713-718
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• 2006

This paper concerns the measurement of thermal conductivity of grouting materials for ground loop heat exchanger. A thermal conductivity meter, QTM-500 based on modified transient hot wire method was used to measure the thermal conductivity of neat bentonite and mixtures of bentonite and various additives. Relative to the total mixture mass, as the percent additive was increased the mixture thermal conductivity increased. For the bentonite-silica sand mixtures, the higher density of the sand particles resulted in much higher mixture thermal conductivity.

• Advances in concrete construction
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• v.9 no.2
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• pp.207-215
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• 2020

This paper describes the experimental studies carried out to determine the properties of fresh and hardened concrete with Recycled Plastic Waste (RPW) as a partial replacement material for fine aggregates. In the experimental study, RPW was used for replacing river sand and manufactured sand (M sand) aggregates in concrete. The replacement level of fine aggregates was ranging from 5% to 20% by volume with an increment of 5%. M40 grade of concrete with water cement ratio of 0.40 was used in this study. Two different types of RPW were used, and they are (i) un-activated RPW and (ii) activated RPW. The activated RPW was obtained by alkali activation of un-activated RPW using NaOH solution. The hardened properties of the concrete determined were dry density, compressive strength, split tensile strength, flexural strength and ultrasonic pulse velocity (UPV). The properties of the concrete with river sand, M sand, activated RPW and un-activated RPW were compared and inferences were drawn. The effect of activation using NaOH solution was investigated using FT-IR study. The micro structural examination of hardened concrete was carried out using Scanning Electron Microscopy (SEM). The test results show that the strength of concrete with activated RPW was more than that of un-activated RPW. From the results, it is evident that it is feasible to use 5% un-activated RPW and 15% activated RPW as fine aggregates for making concrete without affecting the strength properties.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.409-414
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• 1998

To examine the detectability of the aerosol and/or Yellow dust from China crossing over the Yellow sea, three works carried out as follows , Firstly, a comparison was made of the visible(VIS), water vapor(WV), and Infrared(IR) images of the GMS-5 and NOAA/AVHRR on the cases of yellow sand event over Korea. Secondly, the spectral radiance and reflectance(%) was observed during the yellow sand phenomena on April, 1998 in Seoul using the GER-2600 spectroradiometer, which observed the reflected radiance from 350 to 2500 nm in the atmosphere. We selected the optimum wavelength for detecting of the yellow sand from this observation, considering the effects of atmospheric absorption. Finally, the atmospheric radiance emerging from the LOWTRAN-7 radiative transfer model was simulated with and without yellow sand, where we used the estimated aerosol column optical depth ($\tau$ 673 nm) in the Meteorological Research Institute and the d'Almeida's statistical atmospheric aerosol radiative characteristics. The image analysis showed that it was very difficult to detect the yellow sand region only by the image processing because the albedo characteristics of the sand vary irregularly according to the density, size, components and depth of the yellow sand clouds. We found that the 670-680 nm band was useful to simulate aerosol characteristics considering the absorption band from the radiance observation. We are now processing the simulation of atmospheric radiance distribution in the range of 400-900 nm. The purpose of this study is to present the preliminary results of the aerosol and/or Yellow dust detectability using the Ocean Scanning Multispectral Imager(OSMI), which will be mounted on KOMPSAT-1 as the ocean color monitoring sensor with the range of 400-900 nm wavelength.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.73-85
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• 2002

This paper is focused on studying the undrained cyclic triaxial behavior of saturated Nak-dong River sand, using anisotropically consolidated specimens. A test of isotropically consolidated specimens was performed to compare the results of the anisotropically consolidated specimens. The cyclic shear stre3ngth of the sand under various combinations of initial static shear stress and relative density was considered. Failure was defined as a 5% double amplitude cyclic strain and a 5% residual axial strain for both reversal stress and no reversal stress conditions. Using this definition, the cyclic strength of the anisotropically consolidated specimens was affected by the initial static shear stress. For anisotropically consolidated Nak-dong River dense sand, the cyclic strength is greater than that of Toyolura silica sand but is smaller than that of Dogs Bay carbonate sand. By comparing the experimental and predictecl results, it was possible to predict the residual pore pressure of Nak-dong River sand using Hyodo's model with initial static shear stress subjected cyclic loading.