• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.118-123
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• 1995

Evaluating the moisture content for sand is useful for quality cotnrol of concrete. If water content of evaluate instantly and apply for mix proportion sand of concrete, in mixing propertion of concrete, it can makes to improve of concrete quality. In this study, the evaluating method for moisture content of sand, using the electric velocity and dielectric constant was proposed as a study of quality control of concrete. The obtained results are summarized as follow. The resistance ratio was decreased as the increase of moisture content The dielectric constant was decreased as the sand of the moisture content increase.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.2
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• pp.123-129
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• 1998

Compressibility and permeability properties are the most important input parameters necessary to assess the suitability of core materials in seepage control system construction. To achieve this objective, an experimental investigation was conducted in the laboratory. For the bentonite-soil/sand mixes, consolidation and permeability tests were carried out in the conventional consolidation cell, 6Omm in diameter and 2Omm in height, was modified to perform a falling head type permeability test. From the results, the normalized relationship with respect to void ratio at liquid-limit state $(e_L)$, and the changes of compressibility and permeability for various bentonite-soil/sand mixes were presented. This approach will be helpful in proportioning mixes and predicting corresponding changes in engineering behavior. And it is possible to proportion a mix to arrive at the required compressibility without affecting the permeability.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.112-115
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• 2003

Aggregate may limit the strength of concrete, and aggregate with undesirable properties cannot produces strong concrete. Also, the properties of aggregate greatly affect the durability and structural performance of concrete. Recently, it has increased the using of crushed aggregate for concrete due to the exhaustion of good natural aggregate. In case of Korea, in 2002, the using ration of crushed stone occupies about 97% of whole coarse aggregate, and ratio of crushed sand occupies about 18.3% of whole fine aggregate. This is a study to compare and analyze the properties of crushed aggregate for concrete to do mix proportion and improve the concrete quality. According to results, it was found that nearly all the properties of crushed aggregate satisfied with the value recommended by KS.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.297-298
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• 2010

This study was investigates to the lightweight foamed concrete are uses by foamed agent to hydrogen peroxide($H_2O_2$). and then, lightweight foamed to improve the physical characteristics were mixed. mixes to type of admixture/level by changes/character to investigates, It is a purpose to look up admixture and mix proportion to be suitable in order to improve lightweight foamed concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.277-280
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• 2003

Material, mix proportion, curing condition, temperature, humidity and wind velocity have an influence on drying shrinkage of concrete. In this paper, to evaluate the effect of curing condition at early age on the drying shrinkage of concrete was investigated varying curing age for different binder. The principal conclusions from this research were as follows: 1) In case of 14 days of water curing, the drying shrinkage of concrete is smaller than 7 days of water curing, independence of type of binder. 2) In case of 4 days of water curing, the ratio of increase of drying shrinkage of concrete using fly-ash and slag powder is more remarkable than using portland cement alone, comparing the drying shrinkage of 7 days of water curing.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.89-94
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• 2003

In this research, the physical properties of self compacting concrete using ground granulated blast furnace slag and fly ash as a part of cement were investigated. Concrete using ground granulated blast furnace slag and fly ash was prepared with various ground granulated blast furnace slag(30-50 volume %) and fly ash(10-20 volume %) replacement for cement. The effect of each of the materals, which have effects on self compacting concrete made by the basic mix proportion used granulated blast furnace slag and fly ash after hardening, has been checked. The workability, flowing characteristics, resistance of segregation of materals, air content, and compressive strength of concrete using ground granulated blast furnace slag and fly ash were tested and the results were compared with those of ordinary portland cement concrete. In the experiment, we acquired satisfactory results at the point of flowing characteristics and strengths of concrete using ground granulated blast furnace and slag fly ash within the replacement ratio of 65%

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.13-23
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• 2000

In this study, an flexural test on half-scale spliced PSC-I girder was conducted to verify the efficiency of the long span spliced girder as suggested by the Korean Highway Design Specification. The experimental results showed that the specimens developed a complex failure mode due to flexural-compression and torsional stress. The cracking moment of each girder was higher the experiment than was calulated by the ACI and the ultimate strength were the almost same. To estimate the safety and the structural efficiency of the spliced girder, the proposed Yielding Resistance Index(YRI) and ductility index by American Concrete Institutes were used based on the energy concept. The proposed YRI defined the ratio of crack resisting energy and the total energy calculated from load-displacement relationship. Based on the analysis of YRI and ductility index, the flexural behavior of the spliced girder was found to be efficient. Through the experimental results, the structural behavior of proposed spliced PSC I-type girder for long span bridge was found to be more efficient than the exsisting PSC I-type girders.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.15-20
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• 1991

High-strength concrete were produced with super-plasticizer, silica fume, fly ash and blast furnace slag powder. Topics investigated inclued mix proportion, and effects of unit weight of binder, W/C ratio, additive type on the physical properties of high-strength concrete. As the result, at 20% of silica fume, unit weight of binder 700kg/$\textrm{m}^3$ and W/C=0.24, 28days compressive strength of concrete was over 1,000kgf/$\textrm{cm}^2$. And in cases of blending with silica fume 10% and fly ash or slag 10%, it was able to produce economical high-strength concrete with 28 days strength similar to silica fume 20% only, and higher strength after 90days.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.123-125
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• 2011

Pre-foaming that has been used in this study is using to control and guarantee quality, but the optimum mix proportion and regulation are not definite. Therefore, this study investigated properties of foamed concrete according to concentrations of foaming agent to improve usability of foamed concrete. Synthetic foaming agent such as AES(Alkyl Ether Sulfate) and AOS(Alpha Olefin Sulfonate) are used to make foam with 1, 3, and 5% concentrations. We found that the flow of foam concrete increases when foam concentration is high and AES is more flowable than AOS. Density and compressive strength increase when foam concentration is low.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.4
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• pp.149-156
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• 2022

Magneto-Rheological Fluid (MRF) is a functional fluid in which flow characteristics change into magnetic force due to its magnetic particles. When the semi-active control device does not use MRF for a long time, precipitation of magnetic particles and abnormal control force occur. Thus, Electro Magneto-Rheological Fluid (EMRF), which improves the precipitation of magnetic particles for MRF and exhibits existing control performance, was developed in this study. First, the optimal mix proportion ratio was selected by conducting a precipitation experiment and a controlled force test by varying the content of grease based on the existing MRF components. Also, EMRF was applied to the shear-type damper to evaluate the control performance when applied to the control device. The cylinder-type damper was developed to apply to the structure, and control performance evaluation was conducted. The result confirmed that the precipitation of the magnetic particles was improved, while the damper using EMRF exhibited excellent control performance.