• Journal of the Korea Institute of Building Construction
• /
• v.18 no.4
• /
• pp.337-345
• /
• 2018

In this study, observations of oil leakage samples taken from the actual site were performed to identify the causes of the oil leakage phenomenon. As a result, the separation of the material components was determined as the main cause of the oil leakage phenomenon based on the changes in the surface conditions, and verification of this was conducted. The evaluation results confirmed that the filler component of the asphalt mastic subsided with the lapse of the settling time, and that the difference ratio of the filler contents of the upper and lower specimens was up to 23.8% after day 28. Based on these results, a hypothesis on the oil leakage mechanism of asphalt mastic was established, and then modeling of the entire process of oil leakage was performed.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.3
• /
• pp.174-181
• /
• 2018

This paper examines the structural behavior of 3D printed concrete specimens with focus on the bond between the layers. The tensile bond and flexural strengths were investigated experimentally and compared with those of specimens made by conventional mold casting. The test parameters were the time gap between printing layers and the reinforcement between vertical layers. The results showed the 3D printed specimens had voids between layers and confirmed the strength reduction due to printing time gap and the stress concentration caused by the voids. Most of the reduction in tensile bond strength between layers was due to the stress concentration at least up to certain printing time gap. Moreover, beyond a certain printing time gap (24hours), the additional reduction in tensile bond strength reached a level that could affect the structural behavior. The reinforcement between layers was helpful to increase the ductile behavior which is essential to prevent the sudden collapse of the structure. In addition, the reduction in flexural strength due to the stress concentration by the voids was observed and should be considered in the design of 3D printed wall structures against the lateral load.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.1
• /
• pp.73-81
• /
• 2017

In this paper, the periods of cold weather concrete and early frost damage depending on each region in South Korea were studied using the climate data from Korea meteorological administration. The specifications of Korea Concrete Institute(KCI) and Architectural Institute of Japan(AIJ) were applied to provide the periods of cold weather concrete. The periods of early frost damage risk(EFD) were calculated by Hasegawa's suggestion depending on 91 cities in Korea. Climate data for 5 years (2008~2012) were used to obtain both of the periods. Existing data from 1971 to 2000 were also used to compare differences in the periods between past and present study. The periods of cold weather concrete by KCI were calculated about 98 days on average. As the latitude goes up and close to mountain areas, the periods tend to be increased. The periods by present study was shown to be reduced compared to that of previous study by 1~2days. The period of EFD was provided with the level of daily lowest temperature from $-5^{\circ}C$, $-2^{\circ}C$ and $0^{\circ}C$. The beginning day of the period of EFD was earlier than the period of cold weather concrete and the finishing day of the period of EFD was later than the period of cold weather concrete.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.1
• /
• pp.67-76
• /
• 2016

Concrete exposed to severely low temperature below $-20^{\circ}C$ should be provided with proper heat supplying curing to protect the concrete from early frost damage at the time of pouring.meanwhile, so far, effective heat curingmethods of the concrete under severely low temperature are not well established in Korea. For this reason, the objective of this paper is to provide effective heat curingmethod of concrete exposed to severely low temperature to protect early frost damage by varying the combination of heat curingmaterial combinations. Temperature history,maturity development and core strength results are investigated. Fourmock-up specimens simulating slab, wall and column were prepared and heat insulation, heat supplying and both were applied. Test results indicate that the combination of quadruple layer bubble sheet(4BS) and embedding of heating cable has desirable performance for a slab, and heat supplying curing inside heat enclosure and heat generationmat also shows desirable performance for a wall, and for a column, use of EPS heat insulation has proper performance against early frost damage, which reaches $45^{\circ}D{\cdot}D$ and helps the concretemaintain above $0^{\circ}C$ within 3 days. Themethodsmentioned above are believed to be optimum protection from early frost damage of the concrete under $-20^{\circ}C$.

• Journal of the Korea Institute of Building Construction
• /
• v.19 no.2
• /
• pp.157-165
• /
• 2019

The domestic earthquake-resistant regulation was legislated firstly in 1988. However, The magnitude and frequency of earthquakes has been risen in South Korea. Therefore, the mandatory target of earthquake-resistant has been expanded. The earthquake-resistant rates of public facilities have been increased by 58.3%. On the other hand, education facilities are low with 24.8%. For the reason, more than 50% of the educational facilities are expected to be damaged by the earthquake. Especially, the 45% of educational facilities were damaged at Po-Hang earthquake. As a result, the importance of the seismic retrofit for applying existing education facilities was ended up attracting people's interesting. In this respect, in order to develop a effective seismic retrofit method, many researchers have been conducted researches and it is expected to be actively carried out in the future. However, it is insufficient to consider that how far technology has been developed. Therefore, the purpose of this study is a comparative analysis of precedent guidelines in regard to seismic retrofit applying existing education facilities between domestic and other countries. Finally, the directions of future research are suggested.

• Journal of the Korea Institute of Building Construction
• /
• v.22 no.6
• /
• pp.585-596
• /
• 2022

The purpose of this study is to propose an assessment method to analyze clay collectively referred to as fine particles of clay components contained in fine aggregates, and to propose quality standards for clay use through correlation with the performance of concrete to verify the properties of clay measured according to the method. As a result, it is analyzed that it will be suitably utilized as a method to assess the fine particles of the clay component of fine aggregates through the component analysis of XRF. Regarding the related quality standards, considering the error rate of about 10% of KCS 14 20 10, the related quality standards were analyzed to be safe when Al₂O₃+Fe₂O₃+MgO is 23.5% or less and SiO₂+K₂OSiO₂+K2₂O is 66.5% or more. To build on this study, it is expected that a comprehensive review will be conducted through additional follow-up studies such as on clay of coarse aggregates and durability analysis to establish a system for quality control of the soil fraction of aggregates.

• Journal of the Korea Institute of Building Construction
• /
• v.22 no.1
• /
• pp.23-34
• /
• 2022

The purpose of this study is to evaluate the adhesion properties of polymer cement composites for crack repair of an RC structure. Polymer cement composites are manufactured from cement, three types of polymers and silica fume, and the mixture is designed by adjusting the water cement ratio and AE reducing agent so that the viscosity target of the polymer cement composites is 700mPa·s or less. According to the test results, the Type-A adhesion in tension of the polymer cement composite exceeded the adhesion standard of 1.0MPa of the polymer finishing material, and furthermore, depending on the type of polymer, the adhesion in tension was highest for SAE, followed in descending order by EVA, and SBR. In addition, the adhesion in tension of Type-B is up to 1/4.5 lower than that of Type-A, but the incorporation of silica fume shows a significant improvement in terms of adhesion in tension. Based on this study, the basic mixing design of the polymer cement composites required for viscosity and adhesive performance required for crack repair of the RC structure was completed. It could be proposed as an optimal mixing design under conditions for intermixing polymer type EVA, SAE, and P/C 80%-100%.

• Spatial Information Research
• /
• v.17 no.1
• /
• pp.131-144
• /
• 2009

Recently, a lot of local autonomous entities are promoting Ubiquitous City(U-City) Construction by integrating Information Communication Technology(ICT) with city development, and also internationally, a lot of cities are making efforts to develop U-City to intensify a city's competitive strength and improve life quality of city dwellers. In keeping with such a stream of the times, each local autonomous entity and project developer are developing a lot of methodologies to establish optimal U-City in corresponding cities and also inquiring into a variety of development procedures, such as connecting existing urban development methods with information establishment methods. The method used usually is to establish Information strategy Plan(ISP) for a city which will be developed through consulting in the stage of city development planning. ISP is to establish vision & strategy for building the ubiquitous city and is a methodology including city vision, strategy, goal, and implementation method, etc. However, due to a lot of variables, such as a variety of city environment, establishment period, budget, information technology, and etc., it is difficult to contain establishment plans for every occasion in a similar method, in reality. Therefore, it is naturally necessary to suggest plans for city vision & strategy, and selection of element technology/service. Thus, this paper suggests models for vision & strategy establishment of U-City and suggests Top-Down Approach and Bottom-Up Approach method as a plan for U-City establishment. In addition, this paper analyzes general promotion methodologies for constructing U-City and analyzes how these two strategic methods [Top-Down Approach and Bottom-Up Approach] for city vision establishment are composed in such a methodology, to define and analyze its constituent plan.

• Journal of the Korea Concrete Institute
• /
• v.18 no.4 s.94
• /
• pp.527-534
• /
• 2006

This paper outlines a new strengthening technique for concrete beams using externally unbended high-strength bars. The advantages of proposed method lie in speed and simplicity of construction compared to the alternative strengthening method. Externally unbended reinforcement retains many of the advantages over external unbended prestressed tendons. It eliminates time consuming stressing operations. Clearance requirements around anchorages are reduced as access is not required for prestressing jacks. Test results of eight specimens on reinforced concrete beams using different reinforcement materials such as carbon fiber sheet, steel plate and high-tension bar are reported. The beam strengthened by carbon fiber sheet showed a brittle failure mode due to the separation of fiber. As a result of draped profile of external bar, the maximum strength of the beam were increased by up to 212 percent and the deflections were reduced by up to 65 percent. Test results show that the beams reinforced with high-tension bar are superior to reference specimens, especially for the strength and deformation capacity.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.853-856
• /
• 2008

Lightweight foamed concretes are mainly used in apartment building construction for building room floor insulation, sound proof and height difference adjustment, etc. However, existing lightweight foamed concretes have problems like volume reduction by foam removal and excessive crack occurrence, etc, and for compensation, they developed improved concrete binders for lightweight foamed concrete with special characteristics by adding admixture materials used in concrete manufacturing. Therefore, this study reviewed the possibility of its practical use by analyzing all the engineering characteristics after producing imitation member proposed as actual binders and piling lightweight foamed concrete as improved lightweight foamed concrete binder through prior study, the results are as follows. Plain in which various pulverulent materials are mixed showed about 230mm of flow value, satisfying the target flow value, and at 100mm member, about 4mm of settlement occurred, showing a settlement depth reduction effect double the OPC. On strength, OPC showed highest value, but the three levels all showed strengths above the specified value of KS standard 0.5 grade. From the analysis of drying shrinkage member crack, plain, about 0.1mm, was shown very excellent against drying shrinkage crack.