• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.77-78
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• 2020

In Korea, more than 30,000 tons of waste Styrofoam are produced every year. Styrofoam is spent more than 500 years decomposing during the reclamation process, so it needs to be recycled. The recycling rate of waste styrofoam continues to be the third highest in the world, but it is lower than that of Germany and Japan. Therefore, measures are needed to increase the recycling rate of waste Styropol. Another problem is that cement is mainly used in existing lightweight foam concrete. However, large amounts of CO2 from cement-producing processes cause environmental pollution. Currently, Korea is increasing its greenhouse gas reduction targets to cope with energy depletion and climate change, and accelerating efforts to identify and implement reduction measures for each sector. In 2013 alone, about 600 million tons of carbon dioxide was generated in the cement industry. Therefore, this study replaces CO2 generation cement with furnace slag fine powder, uses crude steel cement for initial strength development of bubble concrete, and manufactures hardening materials to study its properties using waste styrofoam. As a result of the experiment, the hardening agent replaced by micro powder of furnace slag was less intense and more prone to absorption than cement using ordinary cement. Further experiments on the segmentation and strength replenishment of furnace slag are believed to contribute to the manufacture of environmentally friendly lightweight foam concrete.

• 콘크리트학회지
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• 제6권5호
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• pp.149-157
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• 1994

보통 포틀랜드 시멘트와 수용성 고분자 물질인 hydroxy propyl methyl cellulose(HPMC), 미세골재 및 혼화재료를 사용하여 W/C=0.1이 되도록 물을 첨가하고 twin roll mill로 혼합 성형한 후 60일간 양생하여 고강도 시멘트 경화체를 제조하였다. 이 경화체에 대한 휨강도 및 파괴인성을 검토하였다. SiC 분말 및 백색시멘트를 첨가한 경우 휨강도는 약 100MPa정도, 탄성계수는 80-95GPa의 값을 나타내었다. 실리카흄을 첨가한 경우 휨강도는 80MPa, 탄성계수는 60GPa의 값을 나타내었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.25-28
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• 2006

This study investigated pre-mixed cement combined with ordinary portland cement, BF and SF, in order to manufacture cement binder, which is possible to produce 150MPa ultra high strength concrete. The BF used in this study reduces and control hydration heat. It can also improve concrete fluidity, while AP increases hydration product and accelerates reaction of BF. SF has micro filler effect and makes pozzolanic reaction. It also fabricates high density internal organization. This developed pre-mixed cement can reduce hydration heat and increase hydration product. It is possible to fabricate high density organization and to secure homogeneity. The mock-up test of ultra high strength concrete showed excellent dispersibility and workability and indicated compressive strength more than 150MPa at 28 days.

• Geomechanics and Engineering
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• 제33권2호
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• pp.211-219
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• 2023

This study analyzes the changes in the physical properties of grout by irradiating it with ultrasonic energy and assesses the injectability of the grout into deep rock fractures. The materials used in the research are OPC (Ordinary Portland Cement) and MC (Micro Cement), and are irradiated depending on the water/cement ratio. After irradiating the grout with ultrasonic energy, viscosity, compressive strength, and particle size are analyzed, and the results of the particle size analysis were applied to Nick Barton's theory to evaluate the injectability of the grout into deep rock fractures under those conditions. It was found that the viscosity of the grout decreased after ultrasonic wave irradiation, and the rate of viscosity reduction tended to decrease as the water/cement ratio increased. Additionally, an increase in compressive strength and a decrease in particle size were observed, indicating that the grout irradiated with ultrasonic energy was more effective for injection into rock fractures.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.138-139
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• 2021

The MiDF Cement Composite is a high-performance construction material with low defects that dehydrates surplus water through pressurization and minimizes air gap between particles. In other words, the performance expression of the MiDF cement complex is affected by pressurized conditions. Thus, this study analyzed the physical characteristics of MiDF cement complex according to the power and pressure of the ga-power and the time of application and intends to use it as a basic data for optimal mixing.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.140-141
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• 2020

Concrete has a lower thermal conductivity or thermal diffusion coefficient compared to other building materials, so it is widely used as fireproof compartment material or refractory material for structures. However, in the event of thermal damage such as fire, cement curing agents and aggregates act differently, resulting in heat generation or deterioration of tissue due to dehydration, resulting in deterioration of physical properties and fire resistance. Therefore, in this study, the processing structure of cement paste is measured through nitrogen absorption method. The test specimen is a cement paste of 40% W/C and is set at 1000 ℃ under heating temperature conditions. As the temperature rose, the micro-pore mass below was reduced based on about 0.01 감소m, but the air gap above that was increased.Thus, in the range of pores measured in nitrogen adsorption, the air mass tended to decrease under high temperature conditions.

• 한국세라믹학회지
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• 제55권5호
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• pp.480-491
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• 2018

Calcium phosphates (CaP) were prepared by a wet chemical method. Micro-crystalline dicalcium phosphate (DCPD) was precipitated at $37^{\circ}C$ and pH 5.0 using $Ca(OH)_2$ and $H_3PO_4$. The precipitated DCPD solution was kept at $37^{\circ}C$ for 96 h. Artificial bone cement was composed of DCPD, $Ca(H_2PO_4)_2{\cdot}H_2O$ (MCPM), and $CaSO_4{\cdot}1/2H_2O$, $H_2O$ and aqueous poly-phosphoric acid solution. The wet prepared CaP powder was used as a matrix for the bone cement recipe. With the addition of aqueous poly-phosphoric acid, the cement hardening reaction was started and the CaP bone cement blocks were fabricated for the mechanical strength measurement. For the tested blocks, the mechanical strength was measured using a universal testing machine, and the microstructure phase analysis was done by field emission scanning electron microscopy and X-ray diffraction. The cement hardening reaction occurred through the decomposition and recrystallization of MCPM and $CaSO_4{\cdot}1/2H_2O$ added on the surface of the wet prepared CaP, and this resulted in grain growth in the bone cement block.

• Geomechanics and Engineering
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• 제35권1호
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• pp.95-108
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• 2023

Soft soil ground is a crucial factor limiting the development of the construction of transportation infrastructure in coastal areas. Soft soil is characterized by low strength, low permeability and high compressibility. However, the ordinary treatment method uses Portland cement to solidify the soft soil, which has low early strength and requires a long curing time. Microbially induced carbonate precipitation (MICP) is an emerging method to address geo-environmental problems associated with geotechnical materials. In this study, a method of bio-cementitious mortars consisting of MICP and cement was proposed to stabilize the soft soil. A series of laboratory tests were conducted on MICP-treated and cement-MICP-treated (C-MICP-treated) soft soils to improve mechanical properties. Microscale observations were also undertaken to reveal the underlying mechanism of cement-soil treated by MICP. The results showed that cohesion and internal friction angles of MICP-treated soft soil were greater than those of remolded soft soil. The UCS, elastic modulus and toughness of C-MICP-treated soft soil with high moisture content (50%, 60%, 70%, 80%) were improved compared to traditional cement-soil. A remarkable difference was observed that the MICP process mainly played a role in the early curing stage (i.e., within 14 days) while cement hydration continued during the whole process. Micro-characterization revealed that the calcium carbonate filling the pores enhanced the soft soil.

• 자원환경지질
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• 제43권2호
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• pp.177-184
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• 2010

시멘트 그라우트가 지반의 차수목적으로 사용될 경우 유동성, 입경 및 블리딩이 중요한 역할을 한다. 이들의 성질을 결정하는 가장 중요한 요소 중의 하나는 그라우트의 물시멘트비이며, 지반침투성능을 개선하기 위해서 보통포틀랜드 시멘트 외에 평균입경이 작은 마이크로 시멘트를 사용하고 있다. 또한, 주입효과는 지반조건뿐만 아니라 배합비 및 시멘트의 입경에 따라 좌우된다. 주입에 의한 침투효과를 평가하는 방법으로서는 실제 지반에서 시험 주입하는 것이 가장 확실한 방법이지만 이와 같은 시험주입은 많은 경비와 시간을 필요로 한다. 때문에 주입의 적합여부나 침투효과를 대략적으로 파악하기 위한 간단하고 실용적인 시험방법이 필요하게 된다. 우리나라의 경우 아직 실내에서 그라우트 주입을 재현할 수 있는 기준 및 장비가 전혀 없는 실정이다. 본 연구에서는 실내에서 여러 가지 그라우트의 주입을 일정하게 재현할 수 있는 가압침투주입장치를 개발하였으며 공시체 제작의 표준을 마련하였다. 가압침투주입시힘을 실시하여 자료를 분석한 결과 침투성능은 물시멘트비가 증가할수록 선형적으로 증가하였으며 재료의 평균입경이 작을수록 침투성능이 개선되었다. 또한 마이크로 시멘트인 마이셈 8000과 초미분말 시멘트인 콜로이드 슈퍼 시멘트의 침투성능을 비교한 결과 평균입경이 상대적으로 작은 콜로이드 슈퍼 시멘트가 침투성능이 좋은 것으로 나타났다.

• Restorative Dentistry and Endodontics
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• 제36권2호
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• pp.132-138
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• 2011

연구목적: 본 연구는 3종의 이중중합 레진시멘트에서 자가중합법과 이중중합법이 중합도에 미치는 영향을 간접적으로 알아보고자 시간경과에 따라 미세경도를 측정하였다. 연구 재료 및 방법: 실험을 위해 자가접착 레진시멘트인 Maxcem Elite (Kerr)와 Rely-X Unicem (3M ESPE) 및 전통형 레진시멘트인 Rely-X ARC (3M ESPE)를 사용하였으며 각 레진시멘트를 동일한 크기의 테플론 몰드에 채우고 자가중합법과 이중중합법으로 중합을 하여 각각 10개씩 시편을 제작하였으며 중합 시작 후 10분, 30분, 1시간, 3시간, 6시간, 12시간, 24시간이 지난 시점에 미세경도를 측정하였다. 결과: 각 시점에서 레진시멘트별로 중합법 사이의 비교를 위한 independent samples t-test 및 모든 실험군 사이의 비교를 위한 one-way ANOVA와 Scheffe 사후검정을 95% 유의수준에서 실시하여 다음과 같은 결과를 얻었다. 1. 모든 실험군에서 시간이 경과함에 따라 미세경도가 증가하는 경향을 보였다. 2. Maxcem에서 중합 1시간 후 부터를 제외하고 이중중합이 자가중합에 비해 높은 미세경도 값을 보였다(p<0.05). 3. 매 시점에서 자가중합법의 Rely-X Unicem이 가장 낮은 미세경도를 보였으며 이중중합법의 Rely-X Unicem이 가장 높은 미세경도 값을 보였다. 결론: 이상의 실험 결과로 볼 때 이중중합 레진시멘트의 충분한 중합을 위해서는 광조사를 반드시 하여야 할 것으로 생각한다.