• Structural Engineering and Mechanics
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• 제38권4호
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• pp.503-516
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• 2011

Uncertainty in concrete properties, including concrete modulus of elasticity and modulus of rupture, are predicted by developing a microstructural homogenization model. The homogenization model is developed by analyzing a concrete representative volume element (RVE) using the finite element (FE) method. The concrete RVE considers concrete as a three phase composite material including: cement paste, aggregate and interfacial transition zone (ITZ). The homogenization model allows for considering two sources of variability in concrete, randomly dispersed aggregates in the concrete matrix and uncertain mechanical properties of composite phases of concrete. Using the proposed homogenization technique, the uncertainty in concrete modulus of elasticity and modulus of rupture (described by numerical cumulative probability density function) are determined. Deflection uncertainty of reinforced concrete (RC) beams, propagated from uncertainties in concrete properties, is quantified using Monte Carlo (MC) simulation. Cracked plane frame analysis is used to account for tension stiffening in concrete. Concrete homogenization enables a unique opportunity to bridge the gap between concrete materials and structural modeling, which is necessary for realistic serviceability prediction.

• Advances in concrete construction
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• 제5권3호
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• pp.183-199
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• 2017

This paper reports an experimental study into the rheological behaviour of Smart Dynamic Concrete (SDC). The investigation is aimed at quantifying the effect of the varying amount of mineral admixtures on the rheology, setting time and compressive strength of SDC containing natural sand and crushed sand. Ordinary Portland cement (OPC) in conjunction with the mineral admixtures was used in different replacement ratio keeping the mix paste volume (35%) and water binder ratio (0.4) constant at controlled laboratory atmospheric temperature ($33^{\circ}C$ to $35^{\circ}C$). The results show that the properties and amount of fine aggregate have a strong influence on the admixture demand for similar initial workability, i.e., flow. The large amounts of fines and lower value of fineness modulus (FM) of natural sand primarily increases the yield stress of the SDC. The mineral admixtures at various replacement ratios strongly contribute to the yield stress and plastic viscosity of SDC due to inter particle friction and cohesion.

• Nuclear Engineering and Technology
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• 제42권2호
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• pp.175-182
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• 2010

As part of a fundamental study on the volume reduction of contaminated concrete wastes, the separation characteristics of the aggregates and the distribution of the radioactivity in the aggregates were investigated. Radioisotope $^{60}Co$ was artificially used as a model contaminant for non-radioactive crushed concrete waste. Volume reduction for radioactively contaminated dismantled concrete wastes was carried out using activated heavy weight concrete taken from the Korea Research Reactor 2 (KRR-2) and light weight concrete from the Uranium Conversion Plant (UCP). The results showed that most of the $^{60}Co$ nuclide was easily separated from the contaminated dismantled concrete waste and was concentrated mainly in the porous fine cement paste. The heating temperature was found to be one of the effective parameters in the removal of the radionuclide from concrete waste. The volume reduction rate achieved was above 80% for the KRR-2 concrete wastes and above 75% for the UCP concrete wastes by thermal and mechanical treatment.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.598-601
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• 2006

The Purpose of this study is to develope the method for early recovery of the biodiversity in the oligotrophical costal area, it is important in the recovery of the biodiversity to make kelp forest grow in the concerned area. In order for it, sufficient nutrient is required as well as the proper seedbed, Hence in this study, granulated fertilizer, which contains nutrient, such as nitrogen, phosphorus and etc, is coated by cement paste, and then is mixed in to the porous concrete in order to provide seedbed and nutrient simultaneously. As a result of examination of growth property of marine plants of multiple performance concrete for kelp forest regeneration, seaweeds is adhered plentifully when the number of days is longer. when the granular fertilizer mixed. adherence and growth of marine plants is excellent and is stabilized over the long run. In case 6 month of the number of days immersed, marine plants and growth will appear.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.353-354
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• 2009

시멘트 결합재로 널리 사용되어지고 있는 고로 수쇄 슬래그 분말을 각종 분쇄기를 사용하여 입도별로 분쇄하고, 이를 혼합하여 충전률과 유동특성을 비교 분석하였으며, 입도분포 또한 비교분석 하였다. 충전률과 유동특성은 비례의 경향이 크게 나타났고, 입도분포가 넓을수록 유동특성은 높았다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.347-348
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• 2009

이 연구는 CO$_2$ 저감을 위한 획기적인. 방안으로 제철공장에서 부산되는 용융 고로슬래그를 시멘트 주원료의 하나로 이용하여 제조한 클링커를 석고와 혼합하여 페이스트 공시체를 제작하여 물성을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.341-342
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• 2009

본 연구는 폐콘크리트 미립분 대체율 및 입도변화에 따른 응결시간, 플로우, 휨강도 그리고 압축강도의 물리적 특성을 검토하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.103-106
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• 2008

Because the physical·chemical properties of bottom ash are inferior, most bottom ash is disused. But the use of bottom ash helps in reducing environmental pollution and solving some bottom ash waste problems. So, we have been investigating about the optimum mixture, hardening mechanism, curing condition and environmental safety of a paste composed of a bottom ash and alkali. optimal mixing proportion of bottom ash solid was cement 5%, water 30%, NaOH 10%. After curing during 28days, bottom ash solid can be achieved compressive strength 15.13MPa. As a result, Compressive strength tests of alkali-activated bottom ash have potential as a replacement of coarse aggregate.

• 한국세라믹학회지
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• 제52권6호
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• pp.483-488
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• 2015

Blast furnace slag(BFS) is well known for its hardening mechanism in ordinary Portland cement with alkali activation due to its latent hydraulic property. The possibility of using calcium compound as activator for BFS has been investigated in this study. The hydration properties of calcium compound activated BFS binders were explored using heat of hydration, powder X-ray diffraction and compressive strength testing. Heat of hydration results indicate that the hydration heat of BFS is lower than OPC paste by about 50%. And ettringite as hydration product was formed continuously as the calcium sulfate was decreased. The maximum compressive strength of hardened BFS mortar at 28 days is confirmed to be 83% as compared with hardened OPC mortar.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.102-105
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• 2003

The purpose of this study is to examine the influence of the flowability and the compressive strength of concrete after the improving of grain shape of the coarse aggregate and fine aggregate fineness modulus. According to the experimental results, the coarse aggregate after improvement of grain shape it lead to be down by 6% fine aggregate ratio, from 47% to 41%. The 0.5% increase of fine aggregate fineness modulus lead to 3% increase of concrete slump, and 1% reduction of concrete air content. While compressive strength on fine aggregate fineness modulus, it was increased until fineness modulus 3.0, but after it reached by 3.5 it was decreased. The compressive strength of the coarse aggregate after improving the grain shape was decreased by 6% due to loss of the adhesion of cement paste.