• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.69-78
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• 2011

As recent concrete products changed to pursue high class, high quality, and high strength, as translucent concrete was developed to meet esthetic effects and exhibition purpose of structures. This study aims at introducing fabrication methods of various shapes of translucent concrete and evaluating feasibility of using mineral admixture such as fly ash, ground granulated blast furnace slag and granulated glass throughout experimental tests. As the result, it was found that compressive strength of translucent concrete block at 28 days is 32.2MPa and higher elastic modulus and Poisson's ratio than ordinary concrete block, which means that translucent concrete is widely applicable to structural purpose. Application of fly ash as a replacement of cement showed lower strength of 85 to 96% than Portland cement. In the meanwhile, ground granulated blast furnace slag showed 82 to 96% depending on the amount of replacement. The use of granulated glass as replacement of optical fiber was not applicable due to invisibility of light in concrete.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.3
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• pp.359-366
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• 2007

Slow sand filtrations have been widely used for water treatment in small communities, however their capacity is often limited by high turbidity in the raw water. For this reason, several pre-treatment facilities were required for a slow sand filter. Turbidity removal from the highly turbid raw water was investigated in roughing filters as a pre-treatment process. The roughing filters followed by rapid mixing tank were operated in the form of a contact filtration. In several jar tests, the predetermined optimum aluminium sulfate (alum) doses for turbid water of 30 and 120NTU were 30 and 50mg/L, respectively. At the optimum alum dose, physically optimum parameters including G value of $220sec^{-1}$ and rapid mixing time of 3 minutes were applied to the contact filtration system. Without addition of alum, the filtrate turbidity from the roughing filters, packed respectively with different media such as sand, porous diatomite ball and gravel, was in the range of 5~30NTU at filtration velocities of 30 and 50m/day. However, the application of a contact filtration to roughing filters showed stably lower filtrate turbidity below 1.0NTU at filtration velocity of 30 m/day. Although the filtration velocity increased to 50m/day, filtrate turbidity was still below 1.0NTU in both single and double layer roughing filters. At influent turbidity of 120NTU, the filtrate turbidity was over 5 NTU in the triple layer roughing filter, which shortened the filter run time. The flocs larger than $10{\mu}m$, formed in the rapid mixing tank, were almost captured through the roughing filter bed, while the almost flocs smaller than $10{\mu}m$ remained in filtrate.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.223-231
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• 1998

Existing cast in place piles made by grouting cement mortar have many problems that cracks by autogeneous and drying shrinkage bring about the deterioration of force for piles, segregations by the submersion of ground water occur and also, high cement contents lead to rise the manufacturing cost. Therefore, this study is intended to investigate the mechanical properties of high performance mortar, incorporating expansive additives and fly ash. for cast in place piles. According to the experimental results, as the contents of expansive additives increase in mortar mixture, fluidity decrease and air contents shows inverse tendency. Setting time is delayed. Although compressive strength at 7days shows a decline tendency. compressive strength at 28days and 91days increase slightly with 5% of expansive additives. As fly ash increase in mortar mixture, high fluidity is shown, air contents increase and setting time is delayed at fresh state, and additives are, the larger length change is, whereas shrinkage decrease with the increase of fly ash.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.295-301
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• 2019

Currently, the most commonly used decontamination agent in the country is calcium chloride, and the use of decontamination agents nationwide is on the rise due to climate change in the country. The deicing agent, aimed at deicing snow, is sprayed and the chloride is frozen and thawed by the dissolved surface water, causing various damages such as deterioration to the concrete. Therefore, in this study, the reactive urethane polymer was manufactured to coat concrete surface protection material, which is a method that prevents moisture from externally penetrating by applying to concrete surfaces, and the mixing agent was selected through the size control of molecules and surface modification, and the properties of penetrant stiffening agents and the application method of concrete was evaluated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.104-112
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• 2019

The material properties of the 3D printing cement composite mortar were evaluated, and the performance range in which printing was possible was calculated using the void ratio in a fresh state as a single index. As a results of the tests, as the water-binder ratio (W/B) increased, the mortar flow value increased and the density and strength decreased. As the sand-binder ratio (SS/B) increased, the mortar flow value decreased. However, strength and density increased and decreased up to a certain SS/B. As admixture-binder ratio (Ad/B) increased, mortar flow value, density, and strength decreased. These trends make it difficult to mix-design to meet the target performances of 3D printing mortars, represented by extrudability and buildability. The value of mortar flow increased proportionally with the void ratio, while the density and strength apparently decreased as the void ratio increased. This indicates that void ratio can be utilized as a single index for controlling the material properties in the design of mortar mixtures. It was found that mortar mixture could be printed by a 3D printer when the void ratio was in the range from 0.6 to 0.7. This was verified by printing a mortar which has the void ratio of 0.634. The mortar was produced with the mixture design of W/B 35.0%, SS/B 60.0%, and Ad/B 0.1%. Further research applying diverse admixtures is needed to improve the quality of 3D printing output mortars.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.635-642
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• 2008

In recent years, epoxy-coated reinforcing bars have been widely used in order to prevent the corrosion of ordinary reinforcing bar. However, they have a bad balance between performance and cost. Especially, they have a brittleness properties, low bond strength to cement concrete and no good bend-ability in the field. The purpose of this study is to evaluate the tensile properties and adhesion of hybrid-type anti-corrosion polymer cement slurry (PCS). PCSs are prepared with four types polymer dispersions using fly ash and silica fume, and tested for proper coating thickness, tensile properties, adhesion to steel plate and bend-ability. From the test results, the viscosity of PCS is effected by polymer dispersion types, and is a little decreased by using fly ash. The coating thickness of PCS has a proper thickness at polymer-binder ratio of 100%. It is apparent that the coating thickness has various values according to viscosity of PCS, water-binder ratio and polymer-binder rato. PCS has a good various anticorrosion properties and physical properties such as tensile strength, adhesion and bend-ability. It is also recommended that proper coating thickness to reinforcing bar is in the ranges of 150 to $250{\mu}m$ for bond strength, adhesion and bend-ability. It is also expected that the coated reinforcing bar using PCS is widely used instead of epoxy coated reinforcing bar in the industrial field.

• Magazine of the Korea Concrete Institute
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• v.11 no.4
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• pp.61-67
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• 1999

물론 이 글이 콘크리트 분야에 종사하는 사람이 알아야 하는 모든 것을 언급하지는 않는다 ; 본인의 저서 'Properties of Concrest'의 판매에 나쁜 영향을 주고 싶지도 않다. 내가 원하는 것은 콘크리트를 제작할 때 우리 모두가 주의를 기울여야 하는 중요한 몇 가지를 강조하는 것이다. 포트랜드 시멘트만 들어있는 보통의 콘크리트가 사용되는 시대는 이미 사라져가고 있고, 단순한 응용을 제외하고는 곧 사라질 것이다. 대부분의 경우는 가능한 일련의 시멘트계 재료 중에 선택을 해야 한다. 혼화제, 특히 고성능 감수제는 중요한 역할을 한다. 물을 많이 첨가하는 것이 작업성을 높이는 유일한 방법도 아니고 최선의 방법도 아니다. 성능을 기준으로 한 기준설정에 관여하는 사람은 이 모든 것을 명심해야 한다. 그렇지 않으면 시방기준에 명시된 규정과 근원적인 요구사항이 잘못 이해되고, 시험배합을 통해서만 잘못되었다는 것이 분명해지게 된다. 그 단계에서는 예상보다, 비록 틀린 것이지만, 더 많은 비용이 들 것이다. 시방규정은 통상적인 조항 외에 갈수록 내구성에 관심을 더 많이 보인다. 가끔은 내구성이 구조물의 기대수명에 대한 연수로 표현되기도 한다. 이 숫자를 배합재료에 관한 자료로 변환시키는 데는 여러 배합재료 및 배합비가 콘크리트의 성질에 미치는 영향에 관하여 깊이 알고 있어야 한다. 모든 사람이 그러한 구체적인 지식을 가질 필요는 없지만, 각 조직마다 상의할 수 있는 사람은 있어야 한다. 엔지니어가 언급한 규정이 따로 없고, 도면의 주를 참고하거나 구체적인 절이 명시되지 않은 상태에서 국가 시방기준을 통해서 조금씩 내용을 수집해야 하는 경우의 상황은 더 난감하다. 이러한 경우는 배합설계나 재료의 선택을 책임지고 있는 사람이, 환경에 대한 노출조건 및 필요한 배합재료에 관하여 잘 알고 있어야 한다. 일반적으로 말해서 콘크리트의 배합은 필요한 특정용도에 따라서 선택되어야 한다. 이것이 사람들이 고성능 콘크리트라 부르는 것이라고도 할 수 있다. 내 생각으로는 고성능 콘크리트와 보통 콘크리트의 경계는 곧 사라질 것이고, 앞으로 대다수 고객에게 주문 콘크리트 혹은 맞춤 콘크리트를 제공해야 할 것이다. 만약 이러한 접근방식에 더 많은 비용이 든다면, 그것을 보상하는 방법은 콘크리트에 대한 이미지를 높이고, 또한 앞으로 모든 용도에 계속적으로 이용될 수 있도록 하는 것이다. 아니면 구조물을 보수하고, 보수한 것을 또 보수하고, 해체하고 해야 할 것이다. 결국은 재활용 골재를 생산할 수 있다고 웃으면서 말할지 모르지만, 이런 식으로는 불만을 지닌 사용자가 콘크리트를 가능하면 멀리하게 만들 것이다. 콘크리트는 절대 심각한 경쟁에 처하지 않을 것이라는 가정은 무모하다. 내가 배합비에 대해서 강조해 왔지만, 이것으로 최종적으로 좋은 콘크리트가 된다는 보장은 없다. 비빔에서는 일반적으로 큰 문제는 없지만 골재에 함유된 수분을 더 잘 제어해야하고 주의를 게을리하지 말아야 한다. 비빔시간은 모든 재료가 잘 섞이기에 충분해야 하는데, 마이크로 실리카가 포함되어 있을 경우에는 더욱 그렇다. 단위시간당 믹서의 작업량을 높이기 위해서 충분히 비비지 않아서는 안된다. 그리고 마지막으로, 콘크리트가 타설되고 다져진 후, 적절하게 양생이 되어야 한다. 마이크로 실리카가 배합에 사용되었을 경우에는 특히 그러하지만, 이것은 모든 콘크리트에서 양생을 잘하는 것이 피복부에서 유해물질이 유입되는 것을 최소화하고 철근을 완전히 보호하는데 있어서 절대적이다. 내가 지금까지 말한 것은 콘크리트에 관한 충분한 지식과 이해를 필요로 한다. 이것은 당연하고 또한 적절한 것이라고 생각한다. 왜냐하면 더 이상 콘크리트를 수준낮은 싸구려 재료로 간주해서는 안되기 때문이다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.70-78
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• 2023

Blast furnace slag, a by-product of the steel industry, is mostly recycled as concrete admixture, but electric arc furnace slag has not been recycled to date. In particular, since electric arc furnace slag partially contains free lime (free-CaO) in the discharge, it is necessary to review this in order to recycle f or construction materials. Recently an atomizing process which is a method of rapidly cooling electric arc furnace slag has been developed and applied. Therefore, in order to use the fine aggregate of oxidized slag from electric furnace restored by this method as an aggregate for concrete, physical damage and chemical reviewing are required. In this study, a physical and chemical review was conducted on the fine aggregate of Electric Arc Furnace Oxidizing Slag (EFOS) as a by-product of the steel manufacturing process with atomizing process. In this experimental study, EFOS was experimentally examined about whether it can be used as concrete fine aggregate. Also, we intend to provide basic data for the future use of the EFOS fine aggregate. As a result of the experimental study, it was found that the fine aggregate of the EFOS satisfied the quality standards of the fine aggregate for concrete in most items specified by Korean Standard.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.54-60
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• 2024

The present study was aimed to evaluate the removal of the trace pollutants (heavy metals and microplastics) in the sewage treatment plant by using the jellyfish Extract at Immunity reaction (JEI) of Aurelia coerulea. The experiment was conducted on two different scales: the lab scale using a Jar-tester and the Pilot system scale equipped with two newly developed devices in the laboratory, the active tube connection mixed system and the concentration integrated separation device. Compared to anionic polymers currently used in the field, JEI showed similar or higher efficiency to remove the trace pollutants. When JEI was added to the effluent through the Pilot system, the combination of JEI and the trace pollutants was maximized through two mixing processes, and as a result, the removal rate of the trace pollutants was greatly improved. Based on these results, we propose the present technology as an alternative to removing trace pollutants that can reduce ecosystem risk and minimize the generation of inorganic waste, away from the existing method.

• Economic and Environmental Geology
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• v.56 no.1
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• pp.103-114
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• 2023

The Christian Museum of Gongju Jeil Church was first built in 1931 and was largely damaged during the Korean War, but the walls and chimneys have been preserved. This building has a high architectural values in that the chapel was reconstructed in 1956, and maintains its original form through repair of damaged parts rather than new construction. The stained glass windows were as installed in 1979 and has a great significance in the Dalle de Verre method using lump glass. However, some of the stained glass damaged partially, such as various cracks and splits, and vertical and horizontal cracks in the joint fillers of supporting the colored glass. As the structural materials of the stained glass window, an iron frame and cement mortar filled with it were used, and corrosion of iron, cracking of mortar and granular decomposition appear partially due to weathering. In the joint fillers, the content of Ca and S is very high, indicating that gypsum were used as admixtures, and the gypsums grow in a rhombohedral and forms a bundle, which is investigated to have undergone recrystallization. As a result of modeling the ultrasonic velocity at the joint fillers, the left and right windows at the entrance show relatively weak in the range of 800 to 1,600m/s, and the lower right corner of the altar window and the upper left corner of the center window were also 1,000 to 1,800m/s, showing relatively low physical properties. And gypsums produced during the neutralization of lime mortar were detected in the joint fillers and contaminants on the surface. Such salts may cause damage to the joint material due to freezing and thawing, so appropriate preventive conservation is required. Also, since various damage types are complexly appearing in stained glass window and joint filler, customized conservation treatment should be reviewed through clinical tests.