• International Journal of Highway Engineering
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• v.12 no.4
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• pp.203-209
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• 2010

The base asphalt mixtures that used the waste recycle asphalt correcting from the four different overlay construction sites in Seoul city were made using the foamed asphalt method. The sample mixtures were made in different ratio of the recycle asphalt and new asphalt material and the performance of the mixtures of the different ratio was investigated in the laboratory. The laboratory tests includes the Marshall test, the indirect tensile test, the resilient modulus test, the creep test and the wheel tracking test. The test of the recycle foamed asphalt mixtures(RFA) were compared with the those of the recycle hot mix asphalt(RHA) mixtures. The performance of the RFA is comparable to that of the RHA. On the other hand, the indirect tensile strength of the RFA in dry condition is lower than that of RHA and the indirect tensile strength of the RFA in wet condition is much lower than that of the RHA.

• Journal of Korea Water Resources Association
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• v.42 no.4
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• pp.271-279
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• 2009

The objective of this study is to develop the scheme to apply one-dimensional finite volume method (FVM) to natural river with complex geometry. In the previous study, FVM using the Riemann approximate solver was performed successfully in the various cases of dam-break, flood propagation, etc. with simple and rectangular cross-sections. We introduced the transform the natural into equivalent rectangular cross-sections. As a result of this way, the momentum equation was modified. The accuracy and applicability of newly developed scheme are demonstrated by means of a test example with exact solution, which uses triangular cross-sections. Secondly, this model is applied to natural river with irregular cross-sections and non-uniform lengths between cross-sections. The results shows that the aspect of flood propagation, location and height of hydraulic jump, and numerical solutions of maximum water level are in good agreement with the measured data. Using the developed scheme in this study, existing numerical schemes conducted in simple cross-sections can be directly applied to natural river without complicated numerical treatment.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.813-824
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• 2010

Thermal conductivity of soils is one of the most important parameters to design horizontal ground heat exchangers. It is well known that the thermal conductivity of soil is strongly influenced by its density and water content because of soil's particulate structure. This paper reviewed and evaluated some of the commonly used prediction models for thermal conductivity of soils with the experimental data available in the literature. Semi-theoretical models for two-component materials were found inappropriate to estimate the thermal conductivity of dry state sands. It came out that the model developed by Cote and Konrad gave the best overall prediction for unsaturated sands available in the literature. Also, a parametric analysis is conducted to investigate the effect of thermal conductivity and water content, soil type on the horizontal ground heat exchanger design. The analysis shows that a required pipe length for the horizontal ground heat exchanger is reduced with the increase of soil thermal conductivity and water content. The calculation results also show that the dimension of the horizontal ground heat exchanger can be reduced to a certain extent by using backfilling material with a higher thermal conductivity of solid particles.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.3
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• pp.223-236
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• 2016

The objective of this study was to construct Italian ryegrass (IRG) dry matter yield (DMY) estimation models in South Korea based on climatic data by locations. Obviously, the climatic environment of Jeju Island has great differences with Korean Peninsula. Meanwhile, many data points were from Jeju Island in the prepared data set. Statistically significant differences in both DMY values and climatic variables were observed between south areas of Korean Peninsula and Jeju Island. Therefore, the estimation models were constructed separately for south areas of Korean Peninsula and Jeju Island separately. For south areas of Korean Peninsula, a data set with a sample size of 933 during 26 years was used. Four optimal climatic variables were selected through a stepwise approach of multiple regression analysis with DMY as the response variable. Subsequently, via general linear model, the final model including the selected four climatic variables and cultivated locations as dummy variables was constructed. The model could explain 37.7% of the variations in DMY of IRG in south areas of Korean Peninsula. For Jeju Island, a data set containing 130 data points during 17 years were used in the modeling construction via the stepwise approach of multiple regression analysis. The model constructed in this research could explain 51.0% of the variations in DMY of IRG. For the two models, homoscedasticity and the assumption that the mean of the residuals were equal to zero were satisfied. Meanwhile, the fitness of both models was good based on most scatters of predicted DMY values fell within the 95% confidence interval.

• Advances in concrete construction
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• v.2 no.2
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• pp.109-123
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• 2014

This paper presents chloride induced corrosion durability of reinforcing steel in geopolymer concretes containing different contents of sodium silicate ($Na_2SiO_3$) and molarities of NaOH solutions. Seven series of mixes are considered in this study. The first series is ordinary Portland cement (OPC) concrete and is considered as the control mix. The rest six series are geopolymer concretes containing 14 and 16 molar NaOH and $Na_2SiO_3$ to NaOH ratios of 2.5, 3.0 and 3.5. In each series three lollypop specimens of 100 mm in diameter and 200 mm in length, each having one 12 mm diameter steel bar are considered for chloride induced corrosion study. The specimens are subjected to cyclic wetting and drying regime for two months. In wet cycle the specimens are immersed in water containing 3.5% (by wt.) NaCl salt for 4 days, while in dry cycle the specimens are placed in open air for three days. The corrosion activity is monitored by measuring the copper/copper sulphate ($Cu/CuSO_4$) half-cell potential according to ASTM C-876. The chloride penetration depth and sorptivity of all seven concretes are also measured. Results show that the geopolymer concretes exhibited better corrosion resistance than OPC concrete. The higher the amount of $Na_2SiO_3$ and higher the concentration of NaOH solutions the better the corrosion resistance of geopolymer concrete is. Similar behaviour is also observed in sorptivity and chloride penetration depth measurements. Generally, the geopolymer concretes exhibited lower sorptivity and chloride penetration depth than that of OPC concrete. Correlation between the sorptivity and the chloride penetration of geopolymer concretes is established. Correlations are also established between 28 days compressive strength and sorptivity and between 28 days compressive strength and chloride penetration of geopolymer concretes.

• Journal of the Korean housing association
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• v.17 no.5
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• pp.9-16
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• 2006

The researches on the environmental friendly buildings have carried out on the materials, environmental property, technical elements and etc., and various buildings with these green materials have built and under construction nowadays and became a new trend of the green building. And recently, new building technique which builds the wall with the soil and wood and very easy to construct (called M Earthen House) was introduced as the green building and rapidly propagated. But the research on the indoor climatic characteristics, the ability to control the environmental comfort and the influence to the human beings of these buildings are not sufficiently identified yet. In this paper, the indoor environmental characteristics and the temperature controlling ability of these buildings in summer season were measured and analysed by the Portable Indoor Air Quality Monitor(BABUC/A, LSI) measuring equipments, ana the subjective test on the thermal environment of the subjects were carried out to evaluate the thermal comfort. The results can be summarized as follows; 1) Compared to the outdoor dry bulb temp.($15.4{\sim}28.7^{\circ}C$), the indoor temp. was $19.5{\sim}26.8^{\circ}C$. It showed the temperature controlling ability of the M earthen house was outstanding. And the indoor relative humidity, compared to the outdoor($45.4{\sim}100%$), was $58.1{\sim}76.4%$, it showed the humidity controlling ability of the M earthen house was also outstanding. 2) The thermal environment was evaluated as 'comfort'(neutral-slightly warm) and the humidity was also evaluated as 'comfort'(neutral-slightly humid). So, the results of the physical and subjective evaluation on the indoor thermal comfort in summer season were 'neutral' and 'comfort' coincidently, it was confirmed that the controlling ability of the indoor temperature and humidity of the M earthen house was very excellent.

• Journal of the Korean GEO-environmental Society
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• v.15 no.10
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• pp.5-13
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• 2014

In this research, in order to study insulation effect of commercial XPS and recycled PE aggregates for prevention of frost heave in the roadbed of railroad track from the freezing temperature, model tests were carried out in the large freezing room. For this, thermal conductivities were measured for various dry densities, water contents, temperatures and mixing ratios of PE aggregates. From the tests, it can be seen that thermal conductivities of roadbed decrease with the increase of the ratio of mixed PE aggregates. However it was sensitive to the changes of temperature and water content due to the amount of water in the voids. From the model test of railroad track, it can be seen that the time to reach $0^{\circ}C$ was longer for XPS than that for the PE aggregates. Also the test shows best insulation effect can be achieved when XPS board was installed above the PE aggregate layer rather than the opposite order.

• 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.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.213-220
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• 2016

In order to drive on road safely, the type of road design and construction is basically needed to optimize driver's safety and vehicle performance. Although the heavy traffic highways were built by reflecting these factors, the national highways and local roads have still taken a lot of problems. In this study, we analyzed the behavior characteristics of a vehicle according to the speed variation of the vehicle using the PC-Crash program for the traffic accidents reconfiguration at GULUN interchange located Hongcheon in Gangwon Province. the conditions outlet surface of the road for analysis were dry road surface, wet road surface and icy road surface. As a result, we identified the fact that the friction coefficient of road surface and the speed of vehicle affected to vehicle behavior characteristics of outlet shape in GULUN interchange, and showed the possibility that we can verify a problem about road design through to this simulation in advance.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1838-1844
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• 2007

The Wonhyo Tunnel on KTX railroad line is a section of latest concerns from domestic environmental NGOs, which focus on potential destruction of ecosystem or the like due to ever-depleted swamp water at about 300m upward from the tunnel under construction. As a result of study, out of all swamps in the vicinity of the tunnel, it was found that Mujechi 1st and 2nd swamps have been getting smaller in their area little by little since 50 years ago primarily under the influence of eroded streams around lower swamp and even ever-increasing annual mean temperature. As the result of monitoring about swamp before work, it was found that swamp water depends absolutely on amount of rainfall. Besides, the results of monitoring during work also didn't show any leakage generated in the tunnel during and after excavation works with regard to a wheat field swamp in the most vicinity of the tunnel (80m away). On the other hand, it was found that the range affected by ground water sink in tunnel section without grouting process amounted to about 100m around the tunnel, which indicates that such ground water sink has no significant impact upon most of swamps near the tunnel. As the result of testing by two well tracer test around swamps, it was noted that swamp water didn't run out from the bottom of swamp even with adjacent ground water level sunk in factitious ways. And the results of physical survey showed that swamp kept saturated even in dry season when ground water level becomes lower than the bottom of swamp. Therefore, even supposing that ground water level becomes sunk due to tunnel works, it is estimated that the water level of swamps would be still kept owing to impervious layer(peat beds).