• International Journal of Highway Engineering
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• v.10 no.3
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• pp.171-178
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• 2008

Compressive strength of concrete has been regarded as a very important parameter of the quality control both in new and existing concrete pavement. It has been used a lot as the concrete strength evaluation both in the various-mixture-using laboratory and construction field using the same mixture. An error usually occurs in the test experiments of the strength, even in the test experiments with evenly mixed and compacted specimens of the compressive strength. It is caused by the 'manually operated' compressing testing, or by the specimens preparation with eccentricity. When compressive strength of evenly mixed concrete is investigated by the curing ages at the construction field, there have to be lots of specimens. And it needs much labor and cost. To substitute the endlessly repeated test experiments of compressive strength, presumption of compressive strength, by nondestructive tests, is needed. In this study, elastic waves were used among various nondestructive tests. Compressive strength of concrete was presumed according to the curing ages, by using the shear wave velocity which is not affected by restricted conditions. In the result, shear wave velocity is very closely related to the compressive strength at the evenly mixed concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.129-136
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• 2012

Temperature of fresh concrete can be effectively used to predict the strength of concrete being cured and make an informed decision for stripping the molds. A hygrothermograph and thermo-couple sensors that require an extensive wiring have been applied to measure a temperature of concrete at the early stage of the curing process on site. However, these methods have limits to provide the temperature data in real time due to harsh working environment including frequent cutting of wires. Therefore, this study is aiming at developing a device based on wireless sensor network to measure the temperature of concrete being cured in formwork. The result showed that the wireless sensor with probe type thermistor which is developed had the same temperature data compared to the existed wire type thermistor, and we confirmed the temperature history of concrete in real time for 28 days throughout the gateway by wireless network that collects the temperature data measured from specimens in laboratory. Also, the network device for transmission can be easily separated from the probe sensor part and reused consistently. If the wireless sensor network device developed uses in the field, the temperature management of concrete will be systematically conducted from at the early stage of the curing, and especially be effective for cold weather concrete construction. In addition, it will contribute to the establishment of advanced quality control system for concrete and productivity of supervisors on site will be increased in the future.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.113-119
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• 2006

It is now established that more than two types of blended aggregate have beneficial effects on quality and supply of concrete in the long run. However, studies on blended aggregate have not widely been progressive and the evaluation method of its most favorable mixture proportion is still needed. Therefore this study investigated the most favorable mixture proportion through the physical experiment of fresh and hardened state's cement mortar, in response to three types of composite ratio, natural fine aggregate(Ns), crushed fine aggregate(Cs) and recycled fine aggregate(Rs). Test showed that increase of blending ratio of Ns and Cs improved fluidity of mot1ar. For the properties of compressive and flexural strength, mortar blending Ns and Cs properly, exhibited similar value to one using only Cs, while mortar mixing Rs showed lower strength value as less as 6% of control one. Mortar using only Rs exhibited the largest drying shrinkage value. In addition, even thought it is not a clear quantitative analysis, technical-imaging-skill presenting the most favorable mixture proportion 3-dimensionally is proposed in this research, in order to notify the proportion easily.

• Journal of the Korea Society of Computer and Information
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• v.25 no.12
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• pp.155-163
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• 2020

This study developed a system that can collect, manage, and utilize the travel routes of individuals who tested positive for coronavirus disease 2019 (COVID-19) based on the data standardization and quality management principles and presented the analysis data collected from the existing system. Unlike many other countries in the world, Korea demonstrated a rapid response by conducting epidemiological investigations. Further, the local governments have actively shared the travel routes of individuals who tested positive for COVID-19 to facilitate proactive prevention of the infectious disease per the Infectious Disease Control and Prevention Law. However, currently, there is no standard protocol for the local governments to share the information, thus complicating the process of sharing, managing, and utilizing the collected data. Therefore, this study developed a system that can facilitate sharing of the travel routes of individuals who tested positive for COVID-19 by establishing database construction procedures and using the travel route of COVID-19 patients as per the Disaster & Safety Information Sharing Platform and developing a data processing guideline, a data entry system with default templates, and Open API. Although this sharing system was designed to communicate the travel routes of COVID-19 patients, it can also be utilized in case of other infectious diseases. Therefore, it can be used as a response strategy for future outbreaks of infectious diseases.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.34 no.1
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• pp.121-143
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• 2023

This study was conducted with the aim of identifying the current status of the national authority data construction project centered on the National Library of Korea for the effective construction and utilization of national knowledge information resources. It also aimed to reveal the possibility and improvement of the national information system with the international standard identification system, and suggesting future development plans. To this end, this study conducted interviews and questionnaires with members of the Korean National Authority Data Sharing System(KNASS). The survey consisted of items related to the current status and difficulties related to the authority, the use of the KNASS, the recognition and utilization of identifiers, the awareness and utilization of the linkage with ISNI, the Importance-Performance Analysis for activating the KNASS, and the overall satisfaction and improvement direction. As a result of the analysis, it was proposed to develop rules and guidelines related to the authority works, to increase the quantity and quality of authority data, to raise understanding of the importance and establish a efficient work system, to diversify the authority service and develop a utilization model, to link the KNASS with international identifiers, and to share the necessity of the KNASS.

• Journal of the Korean GEO-environmental Society
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• v.23 no.9
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• pp.17-23
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• 2022

Using cement as a road subbase is economical, easily modified and supplemented and has excellent road pavement quality control. In addition, cement adheres well to sandy soils without adhesion, and it plays a role of permanently preserving adhesion in viscous soils with adhesion, so it can be widely applied as stable treatment with the advantages of increased strength, reduced compressibility. and improved durability. However, while cement is excellent in terms of strength for a road subbase, the material properties mean that it is difficult to maintain and reinforce when cracks or fractures occur due to dry shrinkage, and the pH increases in the ground due to hexavalent chromium eluting from cement. which can cause environmental problems such as groundwater contamination. Therefore, this study evaluates the usability of alternatives in the road base layer such as environmentally cementitious stabilizer and on-site soil generated from the site. We intend to reduce the environmental damage and evaluate the durability. To evaluate the applicability of the site, Environmental stability test and freeze-thaw test and wetting-drying test was conducted to evaluate the strength characteristics of alternative materials on the road through the limited performance evaluation of environmentally cementitious stabilizer. The test ranges were set at mixing ratios of 10%, 20%, and 30% and ages of three days, and 28 days old to evaluate the early strength and reference strength according to the mixing ratio of the environmentally cementitious stabilizer.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.2
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• pp.121-127
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• 2024

In this study, the applicability of replacing DG(Desulfurized Gypsum) from oil refinery with CCCMs(Carbon dioxide Conversion Capture Materials) as an ALC(Auto-claved LIghtweight Concrete) raw material was examined, and basic properties of ALC was measured. The main chemical components of DG and CCCMs were CaO and SO₃, and an increase in LOI(Loss of ignition) due to mineral carbonation reaction was verified. The crystalline phases of CCCMs were CaCO₃, CaSO₄, Ca(OH)₂, and CaSO₄·2H₂O. When DG, a raw material for ALC production, was replaced with CCCMs, foaming height, pore shape, absolute dry gravity, and compressive strength results measured similar for all binders. In addition, the formation of tobermorite which is main crystalline phase of ALC was shown for all specimens in microstructural analysis.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.35 no.1
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• pp.169-192
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• 2024

This study was conducted with the aim of providing a foundation for high-quality national place name authority data by developing Korean-specific guidelines for place name authority data in response to the need for systematic construction and standardization of authority databases. To this end, a survey of domestic and international trends and cases related to place name authority data was conducted, and the rules and guidelines of each country for establishing place name authority data were analyzed. Based on these surveys and rule analyses, the scope of concepts and terminology required to build a place name authority database were defined and the direction for the development of place name authority data guidelines was set. The analysis also determined the scope and framework of the guidelines, and how they should be referenced to existing rules. The structure of the guidelines proposed in this study is based on the original RDA and NCR. Based on the implications derived from the analysis process, the guidelines were organized and presented in terms of scope of construction, selection and recording of preferred place names, recording of variant place names, and attributes of place names to propose a technical guideline for place name authority data that fits the Korean situation. Future discussions were revealed accordingly.

• Journal of the Korean GEO-environmental Society
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• v.22 no.10
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• pp.21-29
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• 2021

Most concrete gravity-type dams in and out of the country were constructed by column method to control cracks caused by concrete hydration heat generated during construction, resulting in a certain level of leakage after impoundment through various causes, such as contraction joints and construction joints. However, due to the characteristics of concrete structures that shrink and expand according to temperature, concrete dams have vertical joints and drains to allow penetration. PVC waterproof shows excellent effects in completion of the dam, which however increases the possibility of interfacial failure due to different thermal expansion. Other causes of penetration may include problems with quality control during installation, generation of cracks due to heat of hydration of concrete, waterproofing methods, etc. In the case of Bohyunsan Dam in Yeongcheon, North Gyeongsang Province, the amount of drainage in the gallery was checked and underwater, and it was confirmed that there are many penetrations from drainage holes connected to vertical joints, and that some of the PVC waterproofs are not fully operated. As a new method to prevent penetration through vertical joints, D.S.I.M. (Dam Sealing Innovation Method) developed by World E&C was applied to Bohyunsan Dam and checked the amount of drainage in the gallery. As a result of first testing three most leaking vertical joints, the drain in the gallery was reduced by 87% on the average and then applied to the remaining 13 locations, which showed a 83% reduction effect based on the total drain in the gallery. Summing up these results, it was found that D.S.I.M. preventing water leakage from the upstream face is a valid construction method to reduce the water see-through and penetration quantity seen in downstream faces of concrete dams. If D.S.I.M. is applied to other concrete dams at domestic and abroad, it is expected that it will be very effective to prevent water leakage through vertical joints that are visible from downstream faces.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.535-541
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• 2013

The urbanization affects significantly on a natural water circulation system by increasing the imperviousness rate. It is also negatively affecting on urban temperature, environmental pollution, water quality, and aqua-ecosystems. The Korea MOE (Ministry of Environment) adapted a new environmental policy in order to reduce the impact of urbanization, which is the Green Stormwater Infrastructure (GSI) program. The GSI can be achieved by protecting conservable green spaces, enlarging more green spaces, and constructing more permeable pavements. The GSI is including many different techniques such as bioretention, rain garden, infiltration trench and so on. Also It is the infrastructures using natural mechanisms of soils, microorganisms, plants and animals on a water circulation system and pollutant reduction. In this research, a multi functional GSI technology with infiltration-filtration mechanisms has been developed and performed lab-scale tests to evaluate the performances about infiltration rate restoration and pollutant reduction. The most of pollutants including metals, organics and particulates were reduced about 50~90% due to water infiltration and storage functions. The clogging was found when the TSS loading rate was reached on $8.3{\sim}9.0kg/m^2$, which value is higher than the values in literatures. It means the new technology can show high performances with low maintenances.