• 한국지반신소재학회논문집
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• 제13권4호
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• pp.57-68
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• 2014

본 연구에서는 화산섬 제주의 해안지역에 산발적으로 분포하고 있는 모래들을 성인에 따라 세 개의 그룹으로 분류(규산염모래, 탄산염모래, 혼재된 모래)하여 그 특성을 정리하였다. 기본물성은 일반적인 모래의 비중에 비해 규산염모래는 다소 높고 탄산염모래는 낮은 값들을 포함하여 넓게 분포하며 전체적으로 비교적 입경이 큰 탄산염광물이 혼재되어 있어 분급이 불량하고 균등계수가 낮다. 구성성분에 따른 압축강도와의 관계는 규산염성분은 압축강도와 양의 상관을 보이고 탄산염성분은 음의 상관을 보여 서로 상반되는 경향을 보인다. 두성분의 비가 1:1을 기준으로 탄산염성분비가 작아지는 지역의 모래는 건설용 잔골재로 활용이 가능할 것으로 추정된다. 탄성계수 산정 시 압축강도의 2제곱근(ACI 308)과 3제곱근(KCI 2012)을 비교하기 위해 탄성계수를 무차원하여 검토하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.227-232
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• 2002

To evaluate the practical application of oyster shells as construction materials, an experimental study was performed. More specifically, the long-term mechanical properties and durability of concrete blended with oyster shells were investigated. Test results indicate that long-term strength of concrete blended with 10% oyster shells is almost identical to that of normal concrete. However, the long-term strength of concrete blended with 20% oyster shells Is appreciably lower than that of normal concrete. 1'hereby, concrete with higher oyster shell has the possibility giving a bad influence on the concrete long-term strength. Elastic modulus of concrete blended with crushed oyster shells decreases as the blending mixture ratio increases. Namely, the modulus is reduced by approximately 10∼15% when oyster shells are blended up to 20% replacing the fine aggregate. The drying shrinkage strain increases as the blending ratio increases. In addition, the existing model code of drying shrinkage does not coincide with the test results of this study. An adequate prediction equation needs to be developed. The utilization of oyster shells as the fine aggregate in concrete has an insignificant effect on freezing and thawing resistance, carbonation and sulfuric acid attack of concrete recycling. However, water permeability is considerably improved.

• 한국농공학회논문집
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• 제51권1호
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• pp.21-26
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• 2009

This study was performed to evaluate the physical and mechanical properties of concrete using waste activated carbon. Materials used were ordinary portlant cement, crushed coarse aggregate, natural fine aggregate, waste activated carbon, and superplasticizer. The substitution ratios of waste activated carbon were 0,1,2,3,4,5,6,7,8,9 and 10%. The unit weight was decreased and water absorption ratio was increased with increasing the waste activated carbon content, respectively. When the substitution ratio of waste activated carbon was 3%, compressive strength, flexural strength and dynamic modulus of elastisity were more higher than that of the ordinary portland cement (OPC), and it was decreased with increasing the waste activated carbon content, respectively. The most effective contents of waste activated carbon was 2% in performance and 4% in practical use Accordingly, waste activated carbon can be used for concrete material.

• 한국농공학회논문집
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• 제56권5호
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• pp.45-54
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• 2014

This study was performed to evaluate compressive strength, flexural strength, static modulus of elasticity, stress-strain ratio and durability of abrasion on EVA concrete reinforced steel fiber (SF) in order to use hydraulic structures, underground utilities, offshore structures and structures being applied soil contaminated area. It is used ordinary portland cement, crushed coarse aggregate, nature fine aggregate, EVA redispersible polymer powder, superplasticizer and deforming agent to find optimum mix design of EVA concrete reinforced steel fiber. EVA concrete reinforced SF was effected on the improvement of mechanical properties and durability of abrasion.

• Computers and Concrete
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• 제10권2호
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• pp.197-217
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• 2012

This research deals with the prediction of compressive strength of normal and high strength concrete using neural networks. The compressive strength was modeled as a function of eight variables: quantities of cement, fine aggregate, coarse aggregate, micro-silica, water and super-plasticizer, maximum size of coarse aggregate, fineness modulus of fine aggregate. Two networks, one using raw variables and another using grouped dimensionless variables were constructed, trained and tested using available experimental data, covering a large range of concrete compressive strengths. The neural network models were compared with regression models. The neural networks based model gave high prediction accuracy and the results demonstrated that the use of neural networks in assessing compressive strength of concrete is both practical and beneficial. The performance of model using the grouped dimensionless variables is better than the prediction using raw variables.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
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• pp.99-104
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• 1991

It is necessary to generalize the use for structural ALA Concrete in our country, as increasing in the need for the development of ALA and the use of ALA Concrete which is related with the diminution of the self load and foundation section of structure responding to the realistic requirement against the decrease of natural aggregate and the high-rising and large-sizing of structures. This little study, therefore intended to help in the mixing design of concrete by considering the fundamental properties of ALA Concrete used with expanded clay, which is considered by acopting the experimental factors such as unit cement content, water cement ratio and the rate of fine aggregate. By considering the results of this experiment, it has difficulty in getting expected slump with the unit water content of normal concrete because of the large absorption of lightweight aggregate, and because the weight of unit volume and specific gravity ALA Concrete are small it appears that the strength and Elastic Modulus of that are small too and that it is more ductile than normal concrete.

• 한국농공학회지
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• 제38권4호
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• pp.137-146
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• 1996

This paper presents the results of field experience from an experimental pavement construction on a low volume road using recycled concrete. The recycled concrete was prepared by replacing a half of coarse aggregate with recycled aggregate. Virgin natural sand was used as fine aggregate together a plasticizer and a fly ash (0.8% and 5% by wt. of cement, respectively). The load bearing capacity of the subbase made of recycled aggregate was acceptable. The length, thickness and width of the pavement were l00m, 20cm and 3m, respectively. From construction experience, it was found that workability and finishability of the recycled concrete mixture were relatively poor, but strengths were satisfactory. Flexural strength, compressive strength and elastic modulus at 28 days were 54Kg/$cm^2$, over 250Kg/$cm^2$, and 220,OOOKg/$cm^2$, respectively. The construction could be performed by hand without much difficulty. The surface was finished smoothly by wet fabric and only minor cracks were found on the surface.

• Computers and Concrete
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• 제30권1호
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• pp.9-17
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• 2022

This paper discusses the effect of high temperatures (T_s) on the compressive strength and stress-strain curve of recycled fine aggregate concrete (RFAC), based on the experimental results. A total of 90 prisms (100 mm×100 mm×300 mm) were tested. The results show that the compressive strength and elastic modulus of RFAC specimens decreased significantly with increasing T values. As T increased, the strain corresponding to peak stress decreased first when T<200℃ and then increased afterwards. With increasing T values, the stress-strain curves became flat gradually, the peak stress dropped gradually, and ε_p decreased when T<200℃ and increased in the T range of 400-800℃. A stress-strain relations for RFAC exposed to high T_s is proposed, which agree quite well with the test results and may be used to practical applications.

• Advances in concrete construction
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• 제16권5호
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• pp.269-276
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• 2023

In order to study the effect of rubber particle size and admixture on the frost resistance of self-compacting concrete, three self-compacting concrete specimens with equal volume replacement of fine aggregate by rubber particles of different particle sizes were prepared, while conventional self-compacting concrete was made as a comparison specimen. The degradation law of rubber aggregate self-compacted concrete under freeze-thaw cycles was investigated by fast-freezing method test. The results show that the rubber aggregate has some influence on the mechanical properties and freeze-thaw durability of the self-compacting concrete. With the increase of rubber aggregate, the compressive strength of self-compacting concrete gradually decreases, and the smaller the rubber aggregate particle size is, the smaller the effect on the compressive strength of the matrix; rubber aggregate can improve the frost resistance of self-compacting concrete, and the smaller the rubber particle size is, the more obvious the effect on the improvement of the frost resistance of the matrix under the same dosage. Through the research of this paper, it is recommended to use 60~80 purpose rubber aggregate and the substitution rate of 10% is chosen as the best effect.

• 한국터널지하공간학회 논문집
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• 제24권4호
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• pp.317-326
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• 2022

구조용 합성섬유는 작은 비중에 의한 반발률 감소, 지하수 및 해수에 의한 부식 발생의 우려가 없어 강섬유의 대체재로 구조용 합성섬유의 관심이 최근 높아지고 있다. 본 연구에서는 시멘트 복합체의 잔골재 조립률이 구조용 섬유의 인발강도 및 인발에너지에 미치는 영향을 평가하기 위한 실험연구를 수행하였다. 조립률 1.96, 2.69, 3.43인 잔골재로 시멘트 몰탈을 제작하였으며 구조용 합성섬유 1종(polypropylene), 강섬유 1종(hooked ends type)을 대상으로 단일섬유 dog bone shape 공시체를 제작하여 pull-out 실험을 수행하였다. 실험결과 구조용 합성섬유 공시체에서 시멘트 몰탈의 조립률이 증가할수록 인발강도 및 인발에너지가 증가함을 알 수 있었다. 구조용 합성섬유의 경우 시멘트 몰탈과 섬유 사이의 마찰력이 인발메커니즘의 중요인자로 시멘트 몰탈의 잔골재 조립률이 높아질수록 골재 입자가 크고 거칠어지며 섬유와 시멘트 몰탈 사이의 마찰력이 증가하여 섬유의 인발을 억제하기 때문으로 판단된다. 반면, 강섬유 공시체의 경우 시멘트 몰탈 조립률 증가에 따른 인발강도 및 인발에너지의 뚜렷한 경향성은 나타나지 않았다. 이는 강섬유 hooked ends 부분의 기계적 정착이 시멘트 복합체와 강섬유 사이의 마찰력과 비교하여 인발저항력에 미치는 영향이 더 크므로 시멘트 복합체의 잔골재 조립률 변화가 인발저항력에 상대적으로 적은 영향을 미치는 것으로 판단된다.