• 한국건설순환자원학회지
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• 제11권3호
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• pp.14-17
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• 2016

• 한국건설순환자원학회지
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• 제11권2호
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• pp.26-29
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• 2016

• 한국건축시공학회지
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• 제9권4호
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• pp.131-137
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• 2009

건설 폐기물의 대부분을 차지하는 폐콘크리트를 처리하여 재활용하는 비율이 증가하고 있다. 하지만 재활용 골재의 낮은 품질로 인한 부정적 인식과 압축강도, 휨강도, 전단강도, 동결융해 저항성, 연성 등의 낮은 강도특성 때문에 순환골재를 구조물에 활용사례가 미비한 실정이다. 따라서 본 연구에서는 순환골재 콘크리트의 성질 개선을 목적으로 강섬유를 혼입하여 재료실험과 부재실험을 하였으며, 그 결과는 다음과 같다. 각종 실험결과를 종합한바, 강섬유 혼입 순환골재 30% 실험체는 기준실험체와 동등이상의 압축강도, 인장강도, 전단내력, 동결융해 저항성을 갖는 것으로 나타나, 순환골재 치환율 30%까지는 실제 구조물에 대한 적용이 가능할 것으로 사료된다.

• 한국해양공학회지
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• 제17권4호
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• pp.16-22
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• 2003

The mechanical characteristics of newly recycled aggregate concrete on the basis of the proposed mix design model have been studied to develop the precast artificial fishing reefs. In the first task, the experimental test for the recycled aggregates taken from Jeju Island has been carried out to verify the material properties in terms of specific gravity, percentage of solids, absorption and abrasion of coarse aggregates. In the second task, the experimental parameters of newly recycled aggregate concrete are investigated to meet with the requirements of guidelines with respect to slump, unit weight, pH, ultrasonic velocity, void ratio, and compressive strength which are made of sea-shore sand ad slag cement. The natural aggregate and polypropylene fiber are added to newly recycled aggregate concrete to improve the compressive strength and quality. The optimal mix proportions for compressive strength are W/C=30％, S/a=15％, NA/G=50％ in porous concrete case, W/C=40％, S/a=45％ in plain concrete case, and W/C=40％, S/a-45％, PF=1.0kg/㎥ in fiber reinforced concrete case.

• Computers and Concrete
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• 제24권3호
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• pp.193-206
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• 2019

Although concrete is the most widely used construction material, its deficiency in shrinkage and low tensile resistance is undeniable. However, the aforementioned defects can be partially modified by addition of fibers. On the other hand, possibility of adding waste materials in concrete has provided a new ground for use of recycled concrete aggregates in the construction industry. In this study, a constant combination of recyclable coarse and fine concrete aggregates was used to replace the corresponding aggregates at 50% substitution percentage. Moreover, in order to investigate the effects of fibers on mechanical and durability properties of recycled aggregate concrete, the amounts of 0.5%, 1%, and 1.5% steel fibers (ST) and 0.05%, 0.1% and 0.15% polypropylene (PP) fibers by volumes were used individually and in hybrid forms. Compressive strength, tensile strength, flexural strength, ultrasonic pulse velocity (UPV), water absorption, toughness, elastic modulus and shrinkage of samples were investigated. The results of mechanical properties showed that PP fibers reduced the compressive strength while positive impact of steel fibers was evident both in single and hybrid forms. Tensile and flexural strength of samples were improved and the energy absorption of samples containing fibers increased substantially before and after crack presence. Growth in toughness especially in hybrid fiber-reinforced specimens retarded the propagation of cracks. Modulus of elasticity was decreased by the addition of PP fibers while the contrary trend was observed with the addition of steel fibers. PP fibers decreased the ultrasonic pulse velocity slightly and had undesirable effect on water absorption. However, steel fiber caused negligible decline in UPV and a small impact on water absorption. Steel fibers reduce the drying shrinkage by up to 35% when was applied solely. Using fibers also resulted in increasing the ductility of samples in failure. In addition, mechanical properties changes were also evaluated by statistical analysis of MATLAB software and smoothing spline interpolation on compressive, flexural, and indirect tensile strength. Using shell interpolation, the optimization process in areas without laboratory results led to determining optimal theoretical points in a two-parameter system including steel fibers and polypropylene.

• Advances in concrete construction
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• 제16권6호
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• pp.303-316
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• 2023

Using industrial wastes and construction and demolition (C&D) wastes is potentially advantageous for concrete production in terms of sustainability improvement. In this paper, a sustainable Self-Compacting Concrete (SCC) made with industrial wastes and C&D wastes was proposed by considerably replacing natural counterparts with recycled coarse aggregates (RCAs) and supplementary cementitious materials (SCMs) (i.e., Fly ash (FA), ground granulated blast furnace slag (GGBS) and silica fume (SF)). A total of 12 SCC mixes with various RCAs and different combination SCMs were prepared, which comprise binary, ternary and quaternary mixes. The mechanical properties in terms of compressive strength and static elasticity modulus of recycled aggregates (RA-SCC) mixes were determined and analyzed. Microstructural study was implemented to analyze the reason of improvement on mechanical properties. By means of life cycle assessment (LCA) method, the environmental impacts of RA-SCC with various RCAs and SCMs were quantified, analyzed and compared in the system boundary of "cradle-to-gate". In addition, the comparison of LCA results with respect to mechanical properties was conducted. The results demonstrate that the addition of proposed combination SCMs leads to significant improvement in mechanical properties of quaternary RA-SCC mixes with FA, GGBS and SF. Furthermore, quaternary RA-SCC mixes emit lowest environmental burdens without compromising mechanical properties. Thus, using the combination of FA, GGBS and SF as cement substitution to manufacture RA-SCC significantly improves the sustainability of SCC by minimizing the depletion of cement and non-renewable natural resources.

• 한국건설순환자원학회논문집
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• 제1권1호
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• pp.98-107
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• 2005

고속도로 건설 및 유지관리 과정에서 발생되는 폐콘크리트의 재활용을 위하여 현장파쇄에 의한 순환골재의 생산 및 도로용 재료의 시방기준 준수여부를 평가하여 최적의 파쇄방법을 선정하였으며, 최적 파쇄방법에 의해 생산된 순환골재를 이용한 시험시공을 실시하였다. 현장파쇄 순환골재의 입도시험결과 임팩트 크러셔 또는 죠, 콘크러셔 조합형이 소요입도에 적합한 순환골재를 생산할 수 있었다. 생산된 순환골재를 동상방지층에 적용할 경우 함수비 변동에 의한 건조밀도 변화가 작으므로 천연골재에 비하여 관리가 쉬운 장점이 있었으며, 빈배합콘크리트 기층의 경우 재령 7일 압축강도는 순환골재의 종류에 관계없이 10MPa를 상회하므로 현장적용에는 큰 문제가 없음을 알 수 있었다. 시험시공 적용 결과 동상방지층의 경우 순환 굵은골재, 스크리닝스 및 모래를 소요입도로 혼합하였을 때 양호한 지지력을 나타내었으며, 순환골재 빈배합 콘크리트의 강도는 천연쇄석에 비하여 71~85% 강도를 나타내었으나 배합강도 5.8MPa를 크게 상회하였으므로 현장적용에는 문제없음을 확인하였다.

• 한국건설순환자원학회논문집
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• 제10권4호
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• pp.475-481
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• 2022

순환골재는 생산과정에서 발생하는 미세균열 및 순환골재 표면에 존재하는 시멘트 페이스트 성분의 존재로 인해, 천연골재에 비해 높은 흡수율을 가지며, 이로 인해 콘크리트에 골재로서 사용할 경우 작업성 저하, 강도의 저하 등의 문제가 발생하게 된다. 골재의 수급이 점점 어려워지고 있는 현 상황에, 골재 수급의 대안이 될 수 있는 순환골재를 적극적으로 활용하기 위한 방법으로, 본 연구에서는 Tam et al.이 제안한 2단계 배합과정을 활용하였고, 이를 이용해 제조한 콘크리트의 압축강도, 탄성계수, 및 염소이온 확산계수를 일반 배합과정을 적용한 천연골재 콘크리트 및 100 % 치환율의 순환골재 콘크리트와 비교 분석하였다. 실험 결과에 따르면, 압축강도와 탄성계수는 물시멘트비에 관계없이, 2단계 배합방법으로 제작한 순환골재 콘크리트가 일반배합과정으로 배합된 순환골재 콘크리트에 비해 높게 나타났으며, 천연골재 콘크리트에 근접하는 역학적 성능을 발휘하였다. 그러나 염소이온 확산계수의 경우 순환골재 콘크리트가 천연골재 콘크리트보다 높게 측정되었으며, 2단계 배합과정의 적용에 따른 염소이온 확산계수의 감소는 확인할 수 없어, 2단계 배합이 내구성에는 크게 기여하지 않는 것으로 판단된다.

• 한국건설순환자원학회논문집
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• 제4권1호
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• pp.62-67
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• 2016

본 연구에서는 순환골재 용출수의 pH가 실제 환경에 미치는 영향을 평가하기 위하여 기존 순환골재 pH 측정방법 중 용매의 종류, 용출시간, 순환골재 크기에 따라 다양한 방법으로 평가하였다. 또한 순환골재가 현장에 재활용 되었을 때를 가정하여 토양에 의한 pH 완충능력을 평가하였고, 현장재현 모형시험을 통해 순환골재 pH가 실제 하천환경에 미치는 영향을 조사하였다. 순환골재에 의한 pH의 오염도는 자연계에서의 실제 오염농도와는 차이가 있음을 확인하였으며, 특히 실제 현장에서 토양층의 확보가 이뤄진다면 토양의 자연정화 능력에 의해 환경에 미치는 영향은 작을 것으로 평가되었다. 또한 순환골재로부터 발생하는 알칼리성의 pH 유출수가 유입되더라도 하천의 자정능력에 의해 pH 영향은 거의 없는 것으로 평가되었다.

• 한국건축시공학회지
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• 제13권1호
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• pp.29-37
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• 2013

In this study, a zero-cement brick is manufactured by replacing cement with recycled aggregates and blast furnace slag powder. Experimental tests were conducted with standard sized samples of $190{\times}57{\times}90mm$ (KS F 4004), and this manufacturing technique was simulated in practice. Results showed that the zero-cement brick with 0.35 W/B had the highest compressive strength, but the lowest absorption ratio. This absorption ratio of zero-cement brick with 0.35 W/B was lower than the required level determined by KS F 4004. Hence, to increase the absorption ratio, crushed fine aggregate (CA) and emulsified waste vegetable oil (EWO) were used in combination in the zero-cement brick. It was found that the zero-cement brick with CA of 20% and EWO of 1% had the optimum combination, in terms of having the optimum strength development (12 MPa) and the optimum absorption ratio (8.4%) that satisfies the level required by KS. In addition, it is demonstrated that for the manufacturing of zero-cement brick of 1000, this technique reduces the manufacturing cost by 5% compared with conventional cement brick.