• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.25-35
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• 2018

This study presents microstructural characteristics and strength properties of alkali-activated kaolin(K)-fly ash(FA) blends binders. The compressive strength, X-ray diffraction(XRD), thermogravimetric(TG) analysis and SEM/EDS were measured for hardened samples. The results were shown that all the samples had developed the compressive strength over time, regardless of replacement levels of K. It was found that when the amount of K increased, the strengths of samples decreased. In XRD result, no new crystalline phases were observed in all the hardened samples other than the crystalline components of raw FA and K, whereas TG analysis showed that N-A-S-H gel was formed as a reaction product in all the samples. Samples did not have the typical microstructure of dense, and there is little significant difference between the microstructures of the samples despite the differences in the strength testing results with replacement ratios of K. This study showed that the strength of sample was larger for lower Si/Al ratio of reaction product formed in sample. According to the correlation between Si/Al ratio and strength in this study, it is expected that if a chemical additive is used for lowering the Si/Al ratio of reaction product(i.e., increasing the $Al_2O_3$ solubility) in alkali-activated K-FA blends binders, strength improvement in K-FA blends binders could be achieved.

• Korean Journal of Plant Resources
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• v.12 no.3
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• pp.171-178
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• 1999

The purpose of this study was to investigate the optimal mixture ratio for the mycelial culture of the Pleurotus ostreatus. The chief cultural media in this study were cotton hull, sawdust and rice straw and the supplemental media were zeolite, corn cob, defatted rice bran, white cotton, tobacco trash powder, rice hull and peat. The results of this study were as follows; the optimal mixture ratio of the chief cultural media were effective in 6 : 3 : 1(V/V, %), and the mycelial growth and density in the supplemental media were considerably better 1% zeolite,3% corn cob, 5% defatted rice bran, 1% white cotton, 1% tobacco trash powder, 7% rice hull in good order. The optimal mixture ratio be to the mixed supplemental media in the chief cultural media were as follows ; 2 : 2(V/V, %) at the conditions of mixed zeolite and corn cob; 3 : 2(V/V, %) at the conditions of mixed defatted rice bran and white cotton; 1 : 3(V/V, %) at the conditions of mixed tobacco trash powder and rice hull. At the conditions of the whole cultural media mixed, the mycelial growth and density were in good conditions ; cotton hull, sawdust, rice straw, zeolite, corn cob, defatted rice bran, white cotton, tobacco trash powder, rice hull, and peat were mixed 43.0 : 17.2 : 25.8 : 2.0 : 2.0 : 3.0 : 2.0 : 1.0 : 3.0 : 1.0 (V/V, %).

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.75-84
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• 2012

In this paper, strength and leaching characteristics of water sludge-added lightweight soils(WALS) considering reinforcing materials(waste fishing net, glue treated waste fishing net and geogrid) and layer(1 or 2 layer) were investigated using unconfined compression test and leaching test. Several specimens of water sludge-added lightweight soil consisted of water sludge, cement, and bottom ash were prepared according to flowability. Reinforcing material added into these specimens were waste fishing net and geogrid. A glue treated waste fishing net was also added in order to increase interlocking between soil mixture and waste fishing net. Strength increased in the order of WALS reinforced by waste fishing net, glue treated waste fishing net, and geogrid. Strength of specimen with double layer-reinforcing material was greater than that of specimen with single layer reinforcing material. Leaching result of WALS was also satisfied with standard of ministry of environment.

• Journal of the Korea Institute of Building Construction
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• v.10 no.5
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• pp.95-102
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• 2010

In recent years, the demand for the development of high quality and cost effective materials, as well as the competition to ensure a diverse and sufficient amount of ready-mixed concrete, has been increasing rapidly. In this experiment, concretes made with different admixtures are blended with each other in different combinations and ratios, in order to identify potential problems. The first test was a slump level test, in which all of the concretes met the required numbers, as they also did in the test for air content. Plain organic acid concrete scored the highest in bleeding amount, but organic acid mix in general showed a similar outcome. In the early measurement of compressive strength, plain naphthalene concrete was the strongest. Of the blends, the 5:5 mix of organic acid and naphthalene was the strongest. In the standard measurement, the 5:5 mix of naphthalene and lignin was the strongest. Tensile strength tests revealed similar results. Length change rate proved to be greater in blended concrete than in plain concrete, and dry shrinkage rate was highest in the 7:3 ratio blends. Through SEM photo analysis, it was confirmed that the 7:3 ratio blends contained more micro-voids. In conclusion, with the exception of a specific few combinations, it was found that the blending of different types of concrete is undesirable due to the delayed coagulation time as well as the early decrease in strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.101-102
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• 2009

This paper presents experimental results of a PSC-steel hybrid beam connected with the joints which has perfobond rib shear connectors. The flexural behaviors and failure modes are investigated to verify the structural capacity of a tested hybrid beam.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.229-235
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• 2018

In this study, recycled aggregate and natural aggregate were mixed in advance using an aggregate mixing facility that was developed to improve the quality of recycled aggregate concrete. Then the mixed aggregate was applied and concrete characteristics before and after a mix were considered. Based on the findings extracted, this study aimed to suggest a new direction for quality stabilization and application activation of recycled aggregate. The test results of change rates of mortars and coarse aggregates in fresh concrete mixed by a concrete mixer, before and after mixing aggregates showed that the variations of the mortars and coarse aggregates in the concrete mixed with the aggregates beforehand were decreased than those in the concrete before mixing them. The variation of compressive strength and the mean compressive strength at the ages of 3 and 7 days showed similar results before and after the aggregates were mixed, and the strength at the age of 28 days before and after mixing them showed larger deviation than that at the ages of 3 and 7 days. The use of the mixed aggregates after mixing aggregates beforehand reduced the variation in strength and is believed that it is advantageous for long-age strength development. The above results show that the variations of coarse aggregates and compressive strength in the concrete using the mixed aggregates produced by mixing recycled aggregates and natural aggregates beforehand are reduced so it will be possible to produce the homogeneous concrete by mixing aggregates beforehand.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.441-446
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• 2006

유역에서 발생한 고탁수가 저수지내에서 장기화하는 현상에 관한 대책은 장기간이 소요되는 유역관리 대책과 탁수저감일수를 최소화하는 선택취수 개념의 우선 방류기법 등이 있다. 하류하천으로의 탁수 우선배제를 실시하기 위해서는 댐 방류탁수가 하류에 미치는 영향을 정확히 예측할 수 있는 하천탁도 예측 및 관리시스템 구축이 필요하다. 최근 고탁수현상을 경험한 낙동강 수계에서는 본류의 탁도 관리를 위해 임하댐 및 안동댐의 연직 탁도 분포 변화에 따라 댐 방류탁수에 의한 영향을 최소 또는 기준치 이하로 할 수 있는 댐 연계운영에 관한 조건 도출이 필요하다. 선택취수에 관한 수치모의 결과를 이용하여 저수지내 온도 및 탁도 분포 변화와 취수탑의 수문운영에 따른 방류수의 온도 및 탁도를 예측할 수 있다. 본 연구에서는 이와 같은 결과를 이용하여 안동댐과 임하댐의 방류조건에 대한 하류하천 합류부에서의 2차원 이송 확산 수치모의를 수행하고자 하였다. 이와 같은 연구를 성공적으로 수행하기 위해서는 지속적인 현장조사를 통한 지점별 탁도-SS 상관관계 도출, 비정상 흐름 및 수질모의 검 보정, 탁도예측 결과 검증이 필요하다. 평면 2차원 흐름 및 수질 모의 결과에 의하면, 임하댐 방류 탁도로 인한 반변천의 고탁수는 안동댐 방류 수에 지배를 받는 낙동강 본류와 합류되는 지점에서부터 약 5 km 떨어진 지점에서 횡방향 완전혼합이 이루어지는 것으로 나타났다. 이와 같은 모의결과는 완전혼합을 가정하는 1차원 수질모델링의 초기 입력자료에 사용됨으로써 1차원 탁도 모의결과의 정확성을 높이는 데 사용될 수 있다. 이를 이용하여 낙동강 수계 댐 연계운영에 따른 낙동강 탁도 예측모의를 수행하고, 이 결과를 이용하여 낙동강 탁도 예경보 시스템을 구축해야 할 것이다. 또한 선택취수 등을 통해 저수지 관리를 효과적으로 수행하기 위해서는 저수지 내부의 탁도 거동을 정확히 예측할 수 있어야 한다. 따라서 추후 동수역학 및 열역학에 기초한 3차원 수치모형 연구와 성층흐름에 정밀한 밀도류 실험연구 및 이에 대한 적용이 필요할 것으로 판단된다.

• Journal of the Korean Chemical Society
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• v.21 no.5
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• pp.379-383
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• 1977

Since the organophilic bentonite disperses well in polymer matrix, a composite material of polymer and bentonite was studied for its mechanical properties. To increase the degree of dispersion and the bond in forces to the polymer matrix, bentonite, encapsulated by imidazoline, was used as a filler. Polyethylene powder of particle size of 100 mesh was used, and organophilic bentonite, so-called bentone, whose particle size was 250 mesh was also used in this experiment. V-type mixer was used for mixing and Banbury mixer was used for melt-blending. The sample specimen were made by heating the mixture in the plate press, and the specimen were formed as a sheet, exactly the same as the mold on the plate. Tensile strength, bending strength and compressive strength were studied specially. Tensile strength, elongation rate, bending strength and bending rate at constant pressure were decreased as the filler content increased. Compressive strength was increased as the filler content increased.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.291-298
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• 2015

In this paper, a bundled diagonal reinforcement using high performance steel fiber was proposed to enhance the construct ability and seismic performance. Experiments of coupling beam was composed of four specimens and the hysteretic behavior evaluated for reverse cyclic loading to specimens using high performance steel fiber. The main variables of the experiment is a amount of stirrup and bundled reinforcement, depending on whether the mix of steel fiber. Specimen which criteria was applied 100% of stirrup and bundled diagonal reinforcement of ACI318 criteria. With this, by appling same diagonal reinforcement, two specimens were created by adjusting stirrup of 75%, 50%. So, a total of four specimens were produced. When coupling beam was placed concrete, this experiment was mixed in a content of steel fiber 1%. All the specimens were produced by aspect ratio 3.5(l/h=1050/300) to a half-scale. In this result, two specimens as reduced to stirrup of 75%, 50% was no significant difference in the strength, stiffness and energy dissipation capacity, respectively compared to the stirrup of 100%.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.245-248
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• 2014