• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.115-125
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• 1999

The purpose of this experimental research is to investigate the properties of workability and strength of the concrete containing admixtures such as silica fume, fly ash, ground granulated blast-furnace slag, and rice husk ash. For this purpose, the workability and the strength of the concrete containing each admixture were tested and analyzed according to the unit weight of binder and the replacement ratio of each admixture. As a result, considering their workability and strength, the existence of minimum binder weight and optimum replacement ratio of concrete containing admixture to plain concrete were obtained for each admixture.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.377-383
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• 2007

In recent years the field application of high performance concrete has been increased to improve the quality and reliability of concrete structures. The mix design of the high performance concrete includes the 2 set-off mixture theory of mortar and coarse aggregate and that of paste and aggregate. The 2 set-off mixture theory of mortar and coarse aggregate has a problem of having to determine its value through repeated experiments in applying the rheological characteristics of mortar. The 2 set-off mixture theory of paste and aggregate has never been applied to high performance concrete since it doesn't take into account the relationship between optimum fine aggregate ratio and unit volume of powder nor does it consider the critical aggregate volume ratio. As the mixture theory of these high performance concretes, unlike that of general concrete, focuses on flowability and charge-ability, it does not consider intensity features in mix design also, the unit quantity of the materials used is determined by trial and error method in the same way as general concrete. This study is designed to reduce the frequency of trial and error by accurately calculating the optimum fine aggregate ratio, which makes it possible to minimize the aperture of aggregate in use by introducing the maximum density theory to the mix design of high performance concrete. Also, it is intended to propose a simple and reasonable mix design for high performance concrete meeting the requirements for both intensity and flowability. The mix design proposed in this study may reduce trial and error and conveniently produce high performance concrete which has self-chargeability by using more than the minimum unit volume of powder and optimum fine aggregate with minimum porosity.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.273-279
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• 2003

The purpose of this study is to clarify the effect of the monomer ratio on properties of the polymer-modified mortars using methylmethacrylate-butyl acrylate(MMA/BA) latexes, and to obtain basic data necessary to develop appropriate latexes for cement modifiers. From the test results, we knew that the pore volume of polymer-modified mortars using MMA/BA latexes at bound MMA contents of 60 and 70 percent is 7.5∼75nm and the fine pore volume is increased with an increase in the polymer-cement ratio. The total pore volume of polymer-modified mortars using MMA/BA latexes is linearly reduced with an increase in the bound MMA content and increased in the polymer-cement ratio. In general, the superior compressive strength of polymer-modified mortars using MMA/BA latexes is obtained at a bound MMA content of 70 percent and a polymer-cement ratio of 15%. And, the water absorption and chloride ion penetration depth are greatly affected by the polymer-cement ratio rather than the bound MMA content. The important factors affecting the properties of polymer-modified mortars using MMA/BA latexes polymerized with various monomer ratios are the variations of the pore size distribution with changing bound MMA content and the polymer-cement ratio.

• Korean Journal of Social Welfare Studies
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• v.44 no.1
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• pp.61-87
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• 2013

The main purpose of this paper is to analyze the quality of life of poor women. This study utilized data combined KLIPS with Time Use Survey for an analysis and analyzed time at the intersection of the class and gender. With discretionary time as center, this study investigated poverty status from the quality of life. And in order to make comparison more clearly, object was classified into 4 groups; non-poor male, poor male, non-poor female and poor female. Study results are as follows; First of all, poor women had the shortest discretionary time among all the groups and also had highest poverty rate of living quality. And this study found that deprivation of non-poor female headed householder is serious. Second, analysis of inequality level between and within groups through Theil index indicated that gender influence in poor strata was 3 times higher than that of non-poor strata. This study found that poor women experienced mixed exclusion at the point where gender and class crossed. And this study also has a meaning that an empirical analysis was conducted through above matters on secondary poverty and hidden poverty of poor women which existing researches were unable to discover.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.247-254
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• 2014

The present study prepared lightweight foam-soil concrete mixtures classified into three groups. Considering the sustainablility, workability, and compressive strength development of such concrete, high-volume supplementary cementitious materials (SCMs) were used as follows: 20% cement, 15% fly ash, and 65% ground granulated blast-furnace slag. As main test parameters selected for achieving the compressive strength of 1MPa and dry density of $1,000kg/m^3$, the unit solid content (dredged soil and binder) ranged between 900 and $1,807kg/m^3$, and soil-to-binder ratio varied between 3.0 and 7.0. Test results revealed that the flow of the lightweight foam-soil concrete tended to decrease with the increase of unit soil content. The compressive strength of such concrete increased with the increase with the unit binder content, whereas it decreased as soil-to-binder ratio increased, indicating that the compressive strength can be formulated as a function of its dry density and soil-to-binder ratio.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.216-216
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• 2004

본 논문은 우리가 일상 생활에서 접하는 에어컨의 핵심 부품인 열 교환기의 제작과정 중에서 확관 공정에서의 확관속도 최적화에 관한 것이다 여기서 열 교환기는 구멍 뚫린 박판형태의 방열핀과 이 구멍을 통과하는 구리재질의 관인 헤어핀의 2가지 주요 부품으로 구성되어있다 그리고 확관기(Fig. 1)에 있어서의 확관공정은 Fig. 2에서 보는 바와 같이 소성변형을 통한 관의 반지름 방향의 팽창으로 방열핀과 헤어핀을 결합시켜주는 높은 정밀도를 요구하는 작업이다.(중략)

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.307-308
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• 2009

The ultra high strength concrete classed 80 MPa for Lotte Town at pusan has many hydrated materials due to low water to binder ratio and high admixture contents and improved void structure caused by C-S-H gel corresponding to pozzolan and latent hydraulicity of FA and BS. Moreover, durability of the concrete is superior because there was no penetration of carbon dioxide, chloride and chloric ion caused by its fine internal constitution.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.513-516
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• 2004

The purpose of this study is to investigate properties of porous concrete according to volume of binder and compaction energy. The result of this study, as compaction energy goes on increasing, the actual measured void ratio is decreased according as a change of compaction energy and volume of binder. The compaction energy has a very near value by target void ratio on the whole when it is $50kN{\cdot}m/m^2,\;50\~75kN{\cdot}m/m^2$ in case of target void ratio is $15\%\;and\;25\%$. As compaction energy goes on increasing, compressive strength of specimens picked up when target void ratio is $20\%\;and\;25\%$. Also, compressive strength of specimens bluntly picked up when compaction energy is over $50\~75kN{\cdot}m/m^2$.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.6
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• pp.101-110
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• 2010

This study was performed to evaluate the void ratio and strength of porous polymer concrete used coarse aggregates and unsaturated polyester resin to find optimum mix design of porous polymer concrete for planting block. Also, this study was performed to evaluate the planting properties of herbaceous plant and cool-season grass in porous polymer blocks based on the experimental results of porous polymer concrete to develop environmentally friendly planting blocks. Tests for the void ratio and compressive strength of porous polymer concrete were performed at the curing age 7 days. Also, kinds of plants such as Tall fescue, Perennial ryegrass, Lespedeza and Alfalfa for planting were applied to porous polymer blocks. Within 6 weeks after seed, initial germination ratio, cover view and growth length for planting blocks were estimated by various methods.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.381-384
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• 2008

This study investigated spalling prevention and fire resistance properties of the high strength concrete using pre-mixed cement containing fiber to prepare the method for the effective throwing of hybrid fiber. For result of a fire test, almost specimens were protected from fire except 15% of W/C. Totally, the pre-mixed cement containing fiber was favorable compared with passive mixing method for the spalling prevention. It is more effective to prevent spalling caused by fine diversion of fiber even in high strength concrete because it contained many corporate materials. Moreover, the temperature history of the side steel bar on the column test with pre-mixed cement containing fiber did not over 538$^{\circ}C$ which is the average for the standard of fire resistance performance.