• Journal of the Korea Institute of Building Construction
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• v.18 no.3
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• pp.267-275
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• 2018

This study is to investigate the effect of various temperature and humidity conditions on the strength and efflorescence of alkali activated slag cement(AAS) using the red mud. As a result of examining the strength and efflorescence characteristics of AAS mixed with red mud according to the curing conditions, The compressive strength and flexural strength were the highest at 28 days, but the absorption rate, efflorescence area and soluble $Na^+$ elution were lowest in standard wet curing compared to the air curing, high temperature curing and low temperature curing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.196-197
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• 2013

This study is the experiment for manufacturing the Lightweight non-cement matrix based on the Blast furnace slag. And, the matrix was manufactured matrix by generating the bubble just by the reaction of KOH that is the alkali accelerator and paper ash, instead of the general foaming agent, that is the waste managed of incineration the pulp sludge generated in the process of manufacturing the paper. Consequently, the density according to the addition rate of KOH represented the tendency to increase. And it showed up that density of the matrix adding KOH 22.5% was the lowest. As to the strength test result, strength following addition rate of KOH increased. Since the bubble is generated in the reaction of KOH and paper ash, this shows the very low intensity but it is determined to be the result that the amount of vacant space is decreased because the bubble generated in the mixture process comes up as the specific gravity difference.

• The Korean Journal of Pain
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• v.26 no.1
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• pp.94-97
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• 2013

Vertebroplasty (VP) can effectively treat pain and immobility caused by vertebral compression fracture. Because of complications such as extravasation of bone cement (polymethylmethacrylate, PMMA) and adjacent vertebral fractures, some practitioners prefer to inject a small volume of PMMA. In that case, however, insufficient augmentation or a subsequent refracture of the treated vertebrae can occur. A 65-year-old woman visited our clinic complaining of unrelieved severe low back and bilateral flank pain even after she had undergone VP on the $1^{st}$ and $4^{th}$ (L1 and L4) lumbar vertebrae a month earlier. Radiologic findings showed the refracture of L1. We successfully performed the repeat VP by filling the vertebra with a sufficient volume of PMMA, and no complications occurred. The patient's pain and immobility resolved completely three days after the procedure and she remained symptom-free a month later. In conclusion, VP with small volume cement impaction may fail to relieve fracture-induced symptoms, and the refracture of an augmented vertebral body may occur. In this case, repeat VP can effectively resolve both the persistent symptoms and problems of new onset resulting from refracture of the augmented vertebral body due to insufficient volume of bone cement.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.3
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• pp.37-42
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• 2018

The use of fly ash in construction materials is increasing worldwide due the various advantages of using it, such as to produce durable concrete, or to use less cement and thus lower carbon dioxide emissions. The quality of fly ash is often determined by loss on ignition value (LOI), where an upper limit of LOI is set in each country for quality control purpose. However, due to many reasons, production of high LOI fly ash is increasing that cannot be utilized in concrete, ending up in landfill. In this study, the effect of fly ash use in cementitious materials on nitrogen oxides adsorption is examined. In particular, the effect of using high LOI, and thus high carbon content fly ash on nitrogen oxides adsorption is investigated. The results suggest that the higher carbon content fly ash is related to higher nitrogen dioxide adsorption, although normal fly ash was also more effective in nitrogen dioxide adsorption than ordinary portland cement. Also, higher replacement rate of up to 40% of fly ash is beneficial for nitrogen dioxide adsorption. These results demonstrate that high carbon fly ash can be used as construction materials in an environmentally friendly way where strength requirement is low and where nitrogen oxides emissions are high.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.7
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• pp.19-26
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• 2018

This study tested 25 lightweight aggregate concrete (LWAC) mixtures using the expanded bottom ash and dredged soil granules to examine the compressive strength gain of such concrete with different ages. The test parameters investigated were water-to-cement ratios and the natural sand content for the replacement of lightweight fine aggregate. The compressive strength gain rate in the basic equation specified in fib model code was experimentally determined in each mixture and then empirically formulated as a function of the water-to-cement ratio and oven-dried density of concrete. When compared with 28-day compressive strength, the tested LWAC mixtures exhibited relatively low gain ratios (0.49~0.82) at an age of 3 days whereas the gain ratios (1.16~1.41) at 91 days were higher than that (1.05~1.15) of the conventional normal-weight concrete. Thus, the fib model equations tend to overestimate the early strength gain of LWAC but underestimate the long-term strength gain. The proposed equations are in good agreement with the measured compressive strength development of LWAC at different ages, indicating that the mean and standard deviation of the normalized root mean square errors determined in each mixture are 0.101 and 0.053, respectively.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3235-3241
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• 2022

The Korea Atomic Energy Research Institute (KAERI) is planning the construction of the KIJANG Research Reactor (KJRR) for stable supply of ⁹⁹Mo. The Fission ⁹⁹Mo Production Process (FMPP) of KJRR produces solid waste such as spent uranium cake and alumina cake, and liquid waste in the form of intermediate level liquid waste (ILLW) and low level liquid waste (LLLW). This study thus established the operating range and optimum operating conditions for the cementation of ILLW from FMPP. It also evaluated whether cement waste form samples produced under optimum operational conditions satisfy the waste acceptance criteria (WAC) of a disposal facility in Korea (Korea radioactive waste agency, KORAD). Considering economic feasibility and safety, optimum operational conditions were achieved at a w/c ratio of 0.55, and the corresponding salt content was 5.71 wt%. The cement waste form samples prepared under optimum operational conditions were found to satisfy KORAD's WAC when tested for structural stability and leachability. The results indicate that the proposed cementation conditions for the disposal of ILLW from FMMP can be effectively applied to KJRR's disposal facility.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.7
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• pp.778-782
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• 2007

This study investigated the dechlorination mechanisms of TCE by Fe(II) associated with cement. Batch slurry experiments were peformed to investigate the behaviors of selected ions; Fe(II), Fe(III), $Ca^{2+}$, $SO_4^{2-}$ in cement/Fe(II) system. The kinetic experiments of TCE in cement/Fe(II) systems showed that injected Fe(II) was mostly sorbed on cement within 0.5 day and 90% of injected 200 mM sulfate was sorbed on cement within 0.5 day when $[TCE]_0$ = 0.25 mM and $[Fe(II)]_0$ = 200 mM. The kinetic experiments of TCE in hematite/CaO/Fe((II) systems were conducted for simulation of cement/Fe(II) system. Calcium oxide that is one of the major components in cement hydration reactions or has a reactivity in limited conditions. Hematite assumed the ferric iron oxide component of cement. The reactivities observed in hematite/CaO/Fe(II) system were comparable to those reported for cement/Fe(II) systems containing similar molar amounts of Fe(II). The behavior of Fe(II) and $SO_4^{2-}$ sorbed on solid phase at an early stage of reaction in hematite/CaO/Fe(II) system was similar to that of cement/Fe(II) system. Ferric ion was released from hematite at an early period of reaction at low pH. The experimental evidence of kinetic test using hematite/CaO/Fe(II) system implies that the reactive reductant is a mixed-valent Fe(II)-Fe(III) mineral, which may be similar to green rust. Fe(II) sorbed on cement can be converted to new mineral phase having a reactivity such as Fe(II)-Fe(III) (hydr)oxides in cement/Fe(II) systems.

• Journal of the Korea Institute of Building Construction
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• v.8 no.2
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• pp.107-112
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• 2008

According to Korean Architectural Standard Specification (KASS) , at the design stage of the specified concrete strength, strength correction with each temperature level should be considered to secure required strength at 28 days even in low temperature condition, In this paper, the period for the strength correction at the stage of mixture design of the concrete using ordinary Portland cement(OPC) specified in KASS was determined with each region of south Korea based on the meteorological data of KMA(Korea meteorological administration) by applying KASS-5 regulation. In case of 28 days of strength control age, the period for strength correction with 6MPa was calculated to $50{\sim}60$ days and, with 3 MPa. to around 80 days. The period for the strength correction was shown to be decreased with the rise of altitude. The period to consider the delay of the strength development due to low temperature including the period of cold weather concrete was nearly 7 months around 1 year. References for determining the strength correction factors with each region of south Korea was provided in this paper. Further investigation of strength correction of the concrete containing blended cement is to studied.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.315-318
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• 2009

본 논문에서는 해상 기초 교각 매스 콘크리트의 수화열 저감 방안을 다루었다. 저발열 콘크리트, Mesh형 거푸집 공법 등에 대한 실험을 수행하여 각각의 수화열 저감효과를 평가하였다. 현장 실험은 사용 시멘트와 거푸집의 종류, 거푸집의 사용 면수에 따라 총 4 type으로 구성하였으며, 이에 대한 실험 결과와 유한 요소 해석 결과를 비교, 검증하여 최종적인 수화열 저감 성능을 도출하고자 하였다. 실험을 통해, 저발열 시멘트와 유로폼을 사용하는 것이 수화열 저감을 위해 효과적인 방법으로 판명되었으나 추가 공사비의 발생으로 효율성이 떨어질 것으로 판단된다. 또한 Mesh형 거푸집 적용 면 수와 온도 상승 저감 효과는 비례하는 것을 알 수 있었지만 내 외부 온도차가 다소 크게 나타나 수화열에 의한 균열 발생 확률면에서는 다소 불리하게 나타났다. 그러나 실험 단계에서 생략된 양생과 관리를 통하여 균열의 저감효과를 거둘 수 있을 것으로 판단되며, 추가적으로 거푸집 해체 단계를 생략함으로 공기단축 측면에서 유리할 것으로 판단된다.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.329-332
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• 1999

The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as underground box structure, mat-slab of nuclear reactor buildings, dams or large footings, foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, pre-cooling which lowers the initial temperature of fresh concrete with ice flake, pipe cooling which cools the temperature of concrete with flowing water, design change which considers steel bar reinforcement, operation control and so on. The objective of this paper is largely two folded. Firstly we introduce the cracks control technique by employing low-heat cement mix and thermal stress analysis. Secondly it show the application condition of the cracks control technique like sidewall of LNG in Inchonl.