• Journal of the Korea Institute of Building Construction
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• v.14 no.3
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• pp.223-229
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• 2014

In this study, the fire resistance of high strength concrete with organic fibers and polymer powder (PW) was investigated. Two types of the specimens of ${\phi}100{\times}200mm$ and $300{\times}300{\times}600mm$ sizes were prepared. As a result of the test, it was found that the fiber-to-PW mixing ratio of 1:1 achieved the highest fluidity. Further, it was found that the mixing ratios of PP 0.05% + PW 0.05%, PNY 0.05% + PW 0.05% was sufficient to protect the high strength concrete from spalling. For the mock-up specimens of $300{\times}300{\times}600mm$ size, if the required amounts of fibers were added in the concrete. the concrete spalling was resisted. Likewise, in the case of the polymix (PM) together with PW, all the tested specimens were satisfactory for fire resistance performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.107-115
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• 1998

This paper deals with the study on injection with EPDM(Ethylene propylene dien ter polymer) the gap which narrow, long, and tubular between an ablative composite tube and a steel motor case. Small size motor assembly was designed and manufactured for man-portable air defense propulsion system. Motor assembly is consisted with steel tube, ablative composite tube and insulation rubber. Ablative composite tube was made of carbon/phenolic prepreg by rolling process and insulation rubber was made of EPDM by TPM(Trans-power molding) process. To select the insulation rubber material, we tested ablative insulation property and degradation property at first and we tested fluidity, adhesive property and hardness of EPDM rubber. Finally we designed TPM process to manufacture motor case assembly and the motor case assembly was examined by non-destructive test(X-ray).

• Structural Engineering and Mechanics
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• v.59 no.2
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• pp.261-275
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• 2016

Effect of silica fume on fresh properties, compressive strength at 28 days and fracture behavior of fly ash concrete composite were studied in this paper. Test results indicated that the fluidity and flowability of fly ash concrete composites decreased and fly ash concrete composite are more cohesive and appear to be sticky with the addition of silica fume. Addition of silica fume was very effective in improving the compressive strength at 28 days of fly ash concrete composite, and the compressive strength of fly ash concrete composite has a trend of increase with the increase of silica fume content. Results also indicated that all the fracture parameters of effective crack length, fracture toughness, fracture energy, the critical crack opening displacement and the maximum crack opening displacement of fly ash concrete composite decreased with the addition of silica fume. When the content of silica fume increased from 3% to 12%, these fracture parameters decreased gradually with the increase of silica fume content. Furthermore, silica fume had great effect on the relational curves of the three-point bending beam specimen. As the silica fume content increased from 3% to 12%, the areas surrounded by the three relational curves and the axes were becoming smaller and smaller, which indicated that the capability of concrete composite containing fly ash to resist crack propagation was becoming weaker and weaker.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.92-99
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• 2002

This paper is Intended to investigate physical properties and surface glossing of exposed concrete incorporating granulated blast furnace slag(BS). According to test results there is no remarkable variations in fluidity and air content with increase of BS, but unit weight shows decline tendency Compressive strength at later age gains considerably due to potential hydraulicity reaction of BS. It shows that drying shrinkage increases. It is found that low W/B, surface coating and high BS content lead to favorable effects on the surface glossing of exposed concrete because of filling effects on the voids of the concrete. It is improved by about 7 ％ with increase every 10 ％ of BS content. The effects of form pannel kinds on the improvement of surface glossing are in order for acryl, fancy, steel and wood.

• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.707-714
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• 2014

CFT (Concrete-Filled Tube) is a type of steel column comprised of steel tube and concrete. Steel tube holds concrete and the concrete inside tube takes charge of compressive load. This study presents structural performance of the CFT column which has 73~100 MPa high strength concrete inside. Fluidity, mechanical compression, pump pressure test in flexible pipe were conducted for understanding properties of the high strength concrete. Material properties were achieved by various experimental tests, such as slump, slump flow, air content, U-box, O-Lot, L-flow. In addition, mock-up tests were conducted to monitor concrete filling, hydration heat, compressive strength. From construction sites in Sang-am dong and University of Seo-kang, long-term behaviors could be effectively predicted in terms of ACI 209 material model considering elastic deformation, shrinkage and creep.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.62-68
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• 2009

This research examined engineering properties of high performance concrete, when substitution rate of BS increases. A summary of the test result is as follows. The fluidity of unset concrete increases as the substitution rate of BS increases. The amount of air is reduced more or less, but it seems that enough amount of air can be secured by using more air-entraining agent. Setting time is dramatically delayed as the substitution rate of BS increases. The compressive strength of hardening concrete was weaker than OPC before 28 days passes, due to latent hydraulic property of BS. However, after 28 days, it shows same or better property, which is exceptional for the practical uses of hyper strength concrete. Changes in drying shrinkage rate is quite much, because when hydration happens, the amount of free water in concrete increased as W/B gets larger. The amount of drying shrinkage increases as BS substitution rate increases, but every composition shows less than $-500{\times}10^{-6}$, which is relatively fine.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.55-61
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• 2017

This paper is to investigate experimentally the effect of substitution of recycled coarse aggregate(RCA) under 13mm on the engineering properties of the concrete using gap graded coarse aggregates. Concretes with 0.4 of water to cement ratio(W/C) were fabricated to achieve 30MPa of design strength with coarse aggregate over 13mm in size with the maximum size of 25mm. RCA was substituted for coarse aggregate over 13mm from 10% to 50% and crushed coarse aggregate under 13mm was also substituted for coarse aggregate over 13mm from 20% to 40%, respectively. Test results indicated that the replacement of RCA up to 20% resulted in an increase of fluidity and strength. It also caused a decrease in the drying shrinkage due to dense packing effect by achieving continuous grading of mixed aggregates. For practical application of RCA, when properly substituted, the use of RCA enabled the concrete to reduce water contents and sand to aggregate ratio in mixing design stage of the concrete. And, it can also enhance the compressive strength of the concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.235-242
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• 2019

The objective of this study is to modify the mixture proportions of concrete that were developed for section enlargement strengthening elements using a specially designed binder composed of 5% ultra-rapid hardening cement, 10% polymer, and 85% ordinary portland cement in order to assign the self-compaction property to such concrete. The self-compaction abilities of concrete were estimated by the performance criteria specified in JSCE and EFNARC provions. Test results showed that the increase in the unit binder content at the consistent water-to-bider ratio led to increase in viscosity of fresh concrete but did not exhibit the decrease in the fluidity due to a greater viscosity. The mixture proportioning of self-compaction section enlargement concrete could be considered at the following conditions: unit binder contents of $430kg/m^3{\sim}470kg/m^3$ and fine aggregate-to-total aggregate ratios of 40%~46% at the water-to-binder ratio of 38%.

• Journal of the Korea Institute of Building Construction
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• v.18 no.6
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• pp.551-558
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• 2018

This study evaluate the fluidity and hardening properties of mortar by replacement ratio of ferronickel slag powder to estimate the applicability of ferronickel slag powder for cement replacement materials. Ferronickel slag powder was replaced by 0, 5, 10, 15 and 20% of the cement weight. In addition, blast furnace slag powder and fly ash were also used for comparing with the mixtures using ferronickel slag powder. As the test results, the micro-hydration heat of the mixture containing the ferronickel slag powder was lower than that of the mixtures containing the same amount of blast furnace slag powder and fly ash. The flow of the sample with ferronickel slag powder was relatively higher than the other mixtures. In all ages, the compressive strength of the mixture with ferronickel slag powder and fly ash was similar to that of the mix containing only fly ash. In case of drying shrinkage, the mixture containing ferronickel slag powder exhibited lower drying shrinkage than the mixture using blast furnace slag powder, and similar to the mixture containing fly ash.

• Journal of the Korea Institute of Building Construction
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• v.19 no.5
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• pp.449-456
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• 2019

Recent developments in architectural technologies and programs have enabled architects to think creatively and design free-form architecture. however, there are many problems in the production technology of FCP(Free-Form Concrete Panel). In particular, reduced accuracy due to lack of free-form panel production technology can lead to redesign of buildings as a result, problems such as an increase in construction cost and period. Therefore, this experiment aimed to compensate the decrease of the accuracy according to the displacement difference and to derive the proper mixing ratio for maintaining the shape during the free-form panel curing. In this study, molds were made using paraffin that is a recyclable phase change material. Concrete Panel is usually produced from Portland cement, dead burn magnesia, phosphate, borax and fine aggregate. In this study, four mixing ratios of FCP were selected after each material was blended to determine the proper blending ratio of the fluidity phase, the water absorption rate and the water content of the test piece. FCP was fabricated on the basis of the selected four compounding ratios and thickness and error rate were measured. Based on the error rate of the measured FCP, the quality standard was satisfied among the four compounding ratios.