• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.44-49
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• 1992

Selected strength characteristics of recycled concrete using crushed waste concrete were compared with those of conventional concrete using natural aggregate. Compressive strength, bonding at the interface between recycled aggregate and fresh mortar, strain and deflection under three-point bending were evaluated. Recycled concrete, in general, showed lower compressive strength, lower edlastic modulus, higher stain and higher deflection under the same loading level, compared with those of conventional concretes. However, the strength retaining ratios of recycled concretes were higher than those of conventional concretes. The compressive strength which is one of the most important load carrying capacities of concrete should be improved for successful re-use of waste concrete in structural concrete.

• Journal of the Korean Home Economics Association
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• v.35 no.1
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• pp.257-262
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• 1997

In this thesis considering the problems shown in the usage of interlining of clothes and in the process of sewing the breaking away strength which is meant by adhesion is analysed by experimennt in which Polyamide content is dealed with at the 5 level to raise the adhesive strength by using the one-sided non woven adhesive interlining made in this country as the samples. After examing the optimum in the process of Cotton and polyester fabrics and adhered fabrics practical for blouse and jacket and analysing the breaking away strength the wanted property of matter and the change with the repeated laundry We reach at the following results. 1. The adhesive strength of the two adhered fabrics were strongly appeared in order of cotton>polyester. 2. The order of the breaking away strength by the interlinings of adhesive fabrics was A5> A4> A3> A2> A1. 3. The breaking away strength of the two adhered fabrics was weakened by the repeated laundry and the breaking away phenomena were fewer under the most suitable conditions than the various conditions.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.217-219
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• 2012

In this study, the experiment was conducted in the level of mortar as one of the basic studies on pre-cast concrete which acceleration curing is not done. This study has the purpose to develop the strength of mortar into 20MPa within 6 hours in the condition of room temperature using admixtures which can accelerate C3S hydration reaction. In this experiment, W/C was fixed into 20%, PCE which can stimulate C3S was used as an accelerating admixture. From the results of this experiment, maximum content of accelerating admixture was 1%. Also, as more than 20MPa was measured through 6-hour compressive strength, it can be known that strength can be developed without steam-curing.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.337-342
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• 1994

This experimental study is aiming to investigate the hysteritic behavior of high-strength R/C columns subjected to axial load and lateral load reversals. The five 1/4 scaled specimens were made of high-strength concrete with the design strength load(n=0.2f'cAg, n=0.4f'cAg) and type of transverse reinforcement. From the test results, strength and stiffness degradation of columns under higher axial load is much more serious than that under lower axial load. ductility of columns is enhansed with increasing amount of transverse reinforcement, shear strength is depended on the level of axial load.

• Korean Journal of Human Ecology
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• v.19 no.4
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• pp.641-653
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• 2010

This study invesitgated the mediation effect of self-resilience on the relationship between perceived family strength and adolescents' level of adjustment at school. Participants were 479 elementary and middle school students from Daejeon. Data were analysed by SPSS 12.0 and Structural Equation Modeling with AMOS 5.0. Results were as follows: Firstly, family strength gives a direct effect on adolescent's school adjustment. Secondly, family strength is mediated by self-resilience on adolescent's school adjustment. Thirdly, significant differences in the path coefficients of the two groups were not found. These results indicate that we should expand the subjects of family and juvenile welfare, including general adolescents and general families, in order to improve family strength. In addition, programs such as the personal relationship and confidence elevation programs should be enacted to support elementary students' self-resilience.

• Advances in concrete construction
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• v.4 no.3
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• pp.195-206
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• 2016

Today, application of additives to replace cement in order to improve concrete mixes is widely promoted. Micro-silica is among the best pozzolanic additives which can desirably contribute to the concrete characteristics provided it is used properly. In this paper, the effects of AP2RC and P1RB micro-silica gels on strength characteristics of normal concrete are investigated. Obtained results indicated that the application of these additives not only provided proper workability during construction, but also led to increased tensile, compressive and flexural strength values for the concrete during early ages as well as ultimate ones with the resulting reduction in the porosity lowering permeability of the micro-silica concrete. Furthermore, evaluation of microbial contamination of the mentioned gels showed the resultant contamination level to be within the permitted range.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.27-32
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• 1997

It was fond that the compressive and flexural strength of recycled concrete was decreased with increasing the content of recycled aggregate and the early compressive strength was also decreased with increasing Fly Ash level. In comparison with recycled concretes producing various sources, the trend were similar to those shown above, but the differences were minor. the development of Flexural strength in both concretes was similar, but the recycled concrete is lower in the ratio of flexural strength and compressive strength. The drying shrinkage of recycled concrete is increased with increasing the amount of recycled aggregate, particularly the maximum differences were reached between at 2 and 3 weeks.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.123-127
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• 2005

EVA Powder modified high strength concretes were prepared by varying polymer/binder mass ratio with a constant water/binder mass ratio of 0.3. The effect of EVA powder on the slump, hydration heat, compressive and flexural strength, toughness and water absorption ratio was studied. In hydration heat test, temperature of hydration reaction displayed almost fixed level regardless of containing rate of EVA powder, but peak time of hydration reaction displayed late inclination as containing rate of powder increases. With the same water/binder mass ratio, the compressive strength and water absorption of EVA powder modified concretes decreased slightly when EVA powder was added and the flexural strength of EVA powder modified concretes rised slightly when EVA powder was added. Also, the toughness of the modified concretes can be improved markedly. The interpenetrating structure between the polymeric phase and cement hydrates formed at a $2{\sim}6%$(containing rate of EVA powder). The properties of the polymer modified concretes were influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases.

• Journal of Korea Foundry Society
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• v.19 no.6
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• pp.484-492
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• 1999

The microstructures and mechanical properties of high strength yellow brass, Al bronze and Sn bronze alloys fabricated by gravity die casting and squeeze casting were investigated. A rapid cooling of casting was enhanced by pressure applied during solidification of Cu alloys, the cooling rate of casting was more great for high strength yellow brass alloy than other Cu alloys. Grain size and phases of the squeeze cast products become refined to 1/2 level compared to gravity die castings. Squeeze cast Al bronze and high strength yellow brass has about 10-20% higher yield and tensile strength and slighter decreased or nearly same elongation, compared to gravity die cast ones. Sn bronze has nearly same strength and hardness, but shows increased in elongation, compared to gravity die cast ones.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.171-174
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• 2009

This study analyzes the change of the basic characteristics of pavement concrete according to the reinforcement of macro-fiber and the results of the study can be summarized as follows. In the case of the compressive strength of the concrete, the fiber reinforced pavement concrete shows a small decreasing level compared to the basic mixing of pavement concrete (hereafter referred as 'Plain') based on the aging of 28 days. In particular, the polypropylene fiber made in Korea represents a decrease in the strength about 12% compared with that of the Plain. In the case of the tensile strength, it shows certain improvements in the tensile performance compared with that of the Plain. In particular, in the case of the polyvinyl alcohol fiber that shows the largest improvement in tensile performance, it shows an increase in its strength about 21%. In the case of the bending strength, there are no improvements in its strength in the fiber reinforced concrete compared to that of the Plain.