• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.89-92
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• 2005

Our country has experienced variations in temperature as belong to the area of the continental climate that shows four significant seasons. These occur quality of construction. As the hydration of cement processes, the strength of concrete is developed. In order to improve the quality of concrete, various conditions including temperature and humidity should be maintained appropriately and concrete itself should be cured sufficiently This paper is basic experiment for estimating influence of strength by seasonal mock-up concrete's heat of hydration and estimate relationship of compressive strength development by curing temperature. And show basic document as quality control.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.3_4
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• pp.90-98
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• 1995

The recycled concrete, average compressive strength of which was 2l0kg/cm$^2$ or higher with slump range of 14~18cm, was prepared by replacing 25% and 50% by weight of coarse aggregate with recycled aggregate from waste concrete. Mix design method for crushed aggregates was used and all specimens were cured by normal moisture curing method. A plasticiser and a fly ash were added to the mix to improve performance of recycled concrete. Flexural strength, stress- strain relationship and fracture toughness were evaluated by comparing with those of normal concretes. Recycled concrete showed, in general, lower flexural strength and fracture toughness, and higher strain under the same stress level. Fly ash in the concrete had an effect of reducing the strength and fracture toughness on both normal and recycled concretes. Since fly ash is known to improve many properties of concrete, while reducing strength properties, decision for using fly ash should be made carefully depending on the intended usage of the recycled concrete.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.615-621
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• 2016

SiC-polycrystalline fiber (Tyranno SA, Ube Industries, Ltd.) shows very high heat-resistance and excellent mechanical properties up to very high temperatures. However, further increase in the strength is required. Up to now, we have already clarified the relationship between the strength and the defect-size of the SiC-polycrystalline fiber. The defects are formed during the conversion process from the raw material (amorphous Si-Al-C-O fiber) into SiC-polycrystalline fiber. In this conversion process, a degradation of the Si-Al-C-O fiber and a subsequent sintering of the degraded fiber proceed as well, accompanied by a release of CO gas and compositional changes, to obtain the dense SiC-polycrystalline fiber. Since these changes proceed in each filament, the strict control should be needed to minimize residual defects on the surface and in the inside of each filament for achieving the higher strength. In this paper, the controlling factors of the fiber strength and the fine structure will appear.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1069-1080
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• 2008

The mechanical characteristic of Lightweight Foamed Soil(LWFS) are investigated in this research. LWFS is composed of the in-suit soil, cement and foam to reduce the unit-weight and increase compressive strength. The unconfined compressive tests are carried out on the prepared specimens of LWFS with various soil types to investigate the relationship between compressive strength of LWFS and physical properties of soil. The result indicate that coefficient of gradation($C_g$) and liquid limit(LL) are more important factor affecting compressive strength than other physical properties of soil and coefficient of gradation($C_g$) and liquid limit(LL) can standard to determine the optical soil among the in-situ soils for LWFS.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.501-508
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• 2002

The percentage of a mountainous district in our country is comparatively high but the concern for rock mass has been disregarded for a long time. Especially for rock slope, the most important factors are geometric characteristics and their shear strength parameter. In this paper, parametric studies are performed using the distinct element computer program UDEC-BB for rock slopes. Parameters adopted in this paper are joint angle, spacing, persistence, aperture and shear strength parameters (JRC, JCS, basic friction angle). To estimate slope stability, shear strength reduction method is used. The most important factors affecting rock slope stability are joint angle and spacing. The relationship between average displacement calculated by UDEC-BB and safe factor by shear strength reduction method is researched.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.2
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• pp.99-107
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• 2000

The objective of this study are to compare the development of compressive strength of epoxy mortars used as repairing materials with respect to maturity , and to propose a model predicting strength development of epoxy mortars. A series of tests are carried out for the hardener contents of 30, 40 and 50 percentage of epoxy resin and compressive strengths are measured at the age of 6, 12, 24, 72, 120 and 168 hours respectively under the cure temperature of 0, 10, 20 and 3$0^{\circ}C$. The datum temperature is estimated by measured strengths, and the maturity is calculated with the estimated datum temperature. The compressive strength of epoxy mortars can be predicted by regression analysis from the maturity-compressive strength relationship.

• Structural Engineering and Mechanics
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• v.17 no.6
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• pp.863-878
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• 2004

Steel corrosion in reinforced concrete structures leads to concrete cover cracking, reduction of bond strength, and reduction of steel cross section. Among theses consequences mentioned, reduction of bond strength between reinforcement and concrete is of great importance to study the behaviour of RC members with corroded reinforcement. In this paper, firstly, an analytical model based on smeared cracking and average stress-strain relationship of concrete in tension is proposed to evaluate the maximum bursting pressure development in the cover concrete for noncorroded bar. Secondly, the internal pressure caused by the expansion of the corrosion products is evaluated by treating the cracked concrete as an orthotropic material. Finally, bond strength for corroded reinforcing bar is calculated and compared with test results.

• Journal of Korean Association for Spatial Structures
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• v.20 no.4
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• pp.111-121
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• 2020

There has been increasing interest in UHPC (Ultra-High Performance Concrete) materials in recent years. Owing to the superior mechanical properties and durability, the UHPC has been widely used for the design of various types of structures. In this paper, machine learning based compressive strength prediction methods of the UHPC are proposed. Various regression-based machine learning models were built to train dataset. For train and validation, 110 data samples collected from the literatures were used. Because the proportion between the compressive strength and its composition is a highly nonlinear, more advanced regression models are demanded to obtain better results. The complex relationship between mixture proportion and concrete compressive strength can be predicted by using the selected regression method.

• Architectural research
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• v.23 no.1
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• pp.11-17
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• 2021

A concrete-filled circular steel tube beam was fabricated, and a bending test was performed to analyze its failure modes, displacement ductility, bending-shear strength, and load-central deflection relationship. For the bending test, the installation position of the shape memory alloy (SMA) inside and outside the double-skin steel tube was used, and the rebar installation position, the concrete strength, the mixing of fibers, and the inner-outer diameter ratio as the main parameters. The test results showed that the installation positions of the reinforcements inside and outside the double-skin steel tube and the inner-outer diameter ratio of the steel tube affected the ductility, maximum load, and failure mode. In general, the specimen made of general concrete with SMA installed outside and inside (OI) the double-skin steel tube showed the best results.

• Journal of Digital Convergence
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• v.19 no.4
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• pp.177-183
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• 2021

The purpose of this study was to investigate the double mediation effects of interpersonal relationship ability and self-efficacy in the link between family strengths and self-esteem of college students. To this end, a survey was conducted for 1 month in November 2019, targeting 340 students conveniently sampled from C city in Chungcheongbuk-do and J city in Jeollabuk-do, and the analysis was conducted using SPSS Win. 25 and SPSS PROCESS Macro. The applied statistical techniques were mean comparison analysis (t-test, One-ANOVA), correlation analysis, and PROCESS Macro model No. 6 to analyze the double mediating effect. The main findings of the study are: First, self-esteem was significantly higher in education major than in other majors. Second, as a result of correlation analysis, self-esteem showed a significant positive correlation with family strength, interpersonal relationship ability, and self-efficacy. Third, as a result of the double mediation effect analysis, interpersonal relationship ability and self-efficacy double mediated in the relationship between family strength and self-esteem. The results of this study can be used as basic data to enhance the self-esteem of college students by utilizing interpersonal relationship ability and self-efficacy.