• 한국구조물진단유지관리공학회 논문집
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• 제7권1호
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• pp.173-179
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• 2003

실제 현장에서 사용하고 있는 고강도 콘크리트 배합의 단위시멘트량은 대부분의 경우 소요의 슬럼프를 확보하는데 필요한 양으로 결정된다. 이 방법은 보통 강도 콘크리트의 배합설계 개념을 적용한 것이기 때문에 필요 이상의 단위시멘트량을 사용하게 된다. 따라서 상대적으로 많은 양의 시멘트를 사용하게 되어 콘크리트의 내구성을 저하시키게 된다. 이에 본 연구에서는 고강도 콘크리트의 내구성과 시공성 및 강도를 동시에 고려한 적정 단위시멘트량을 분석하였으며, 적정 단위시멘트량을 사용함에 따른 혼화제 첨가량 및 적정잔골재율에 대해 검토하였다. 실험 결과, 본 연구의 실험조건에서 단위시멘트량을 $370kg/m^3$으로부터 $550kg/m^3$까지 사용하더라도 압축강도의 차이는 거의 없는 것으로 나타났다. 따라서 콘크리트의 배합시 소요의 설계강도뿐만 아니라 내구성과 시공성을 동시에 만족하는 최소의 단위시멘트량을 결정하여 적용하여야 할 것으로 판단된다.

• 자원리싸이클링
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• 제23권3호
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• pp.13-20
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• 2014

현재 산업 및 토목기술의 발전으로 인한 콘크리트 구조물의 대형화 및 다양화가 시도되고 있으나 대형 구조물의 시공 시 발생하는 수화열은 온도균열을 유발하여 콘크리트 구조물의 내구성능을 저하시키는 문제를 발생한다. 본 논문은 시멘트의 종류에 따른 콘크리트의 내구성능 및 수화열 저감 특성을 고찰하기 위하여 보통포틀랜드시멘트, 플라이애쉬를 혼합한 2성분계 시멘트, 플라이애쉬와 고로슬래그를 혼합한 3성분계 시멘트 및 저발열 시멘트를 각 각 사용하여 제작한 콘크리트의 물성, 내구성능 및 수화특성 등의 결과를 비교 분석한 결과, 3성분계 혼합 시멘트가 내구성능 및 수화열 저감 효과에 가장 우수한 것으로 나타나 매스 콘크리트 및 내구성능이 요구되는 구조물 축조에 적합하다고 판단되었다.

• 산업기술연구
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• 제17권
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• pp.313-322
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• 1997

As the weight of trucks increases, the need for concrete pavement also increases. Therefore, the addition of fly-ash may improve the properties of pavement concrete as well as recycle fly-ash. A full factorial experiment was performed using the primary variables, such as water-cement ratio, fly-ash substitution ratio, and maximum size of coarse aggregate, as a preliminary study for optimum mixture design for pavement concrete. The results of preliminary study indicates that the addition of fly-ash is the most important factor determining concrete strength, followed by the maximum size of coarse aggregate and water-cement ratio. It, also, shows the relative importance of fly-ash substitution ratio, compared to the water-cement ratio, and the interaction effects between the primary variables. Optimum mixture designs for pavement concrete incorporating fly-ash, that satisfied the target responses, were proposed in terms of fly-ash substitution ratio, water cement ratio and maximum size of coarse aggregate.

• Computers and Concrete
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• 제18권5호
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• pp.951-968
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• 2016

In this study, pullout capacities of post-installed deformed bars anchored in low strength concrete using different bonding materials are investigated experimentally. The experimental study was conducted under outdoor and indoor conditions; on the beams of an actual reinforced concrete building and on concrete bases constructed at Istanbul Technical University (ITU). Ready-mixed cement based anchorage mortar with modified polymers (M1), ordinary cement with modified polymer admixture (M2), and epoxy based anchorage mortar with two components (E) were used as bonding material. Furthermore, test results are compared with the predictions of current analytical models. Findings of the study showed that properly designed cement based mortars can be efficiently used for anchoring deformed bars in low quality concrete. It is important to note that the cost of cement based mortar is much lower with respect to conventional epoxy based anchorage materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.485-490
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• 2000

Because of occuring easily the crack, debond, lutting on asphalts pavement of bredge decks under traffic's heavy weigt load. We investigated the application of latex modified concrete to resurface and repaire bridge decks for preventing the above problems. Here, Using the ordinary portland cement and high early cement, We rested mix design, workability, compressive strength, adhesive power, drying shrinkage, carbonation, and economic estimation etc. We selected the condition of application to resurface and repaire bridge decks and detected high early cement is superior to ordinary portland cement in results of analyzing the application of the repairing bridge decks and economic estimations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.489-492
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• 2006

A chloride is an important deteriorating factor which governs the durability of the reinforced-concrete structures under marine environments. Also, the main penetration mechanism of chloride ion into concrete is a diffusion phenomenon and numerous methods have been proposed to determine the diffusion coefficient of chloride ion quickly. In this study, electrically accelerated experiments were carried out in order to evaluate diffusion coefficient of the chloride ion into concrete. The methods were diffusion cell test method in which the voltage of 15V(DC) was applied. The type of cement is blended cement in which the admixtures of blast-furnace slag and fly ash were used. In conclusion, the diffusion coefficient of chloride ion is much affected according to mineral admixtures and the diffusion coefficient of ternary blended cement showed very low values. it is presumably said that this result is due to highly densified pore structures by the aid of slag substitution and pozzolanic activity of fly ash.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
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• pp.123-128
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• 1998

Currently the study on the effective use of the fly ash is concentrated as construction materials, which is by product of electric power generating plants. Fly ash, therefore, can be used as concrete admixture for the purpose of not only increasing the concrete quality but also of utilizing materials. Within the country it is not easy to use fly ash for the construction purpose because the properties of fly ash are varied due to the use of different raw ores in the various power plants. And little previous construction experiments and the basic experiments about the formation of bubbles are performed. In this study the water-cement ratio is varied in 3 different values and compressive strength is measured and freeze-thaw experiments are preformed to establish the relationships between water-cement ratios and the durability. And also for each batch of different water-cement ratio fly ash is substituted 10%, 20% and 30% of cement and concrete mixture the admixture and the formation of bubbles and also freeze-thaw resistance.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.183-186
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• 1995

Most defects in the cement concrete pavement take place mainly on the joints. These corner cracks don't happen as often as others relatively. it happens continuously. In order to analyze the structural behavior of the corner cracks, The finite element structural analysis was performed on the representative section of the cement concrete pavements using JSLAB which uses FEM analysis method. On plain cement concrete pavements, The result shows that loading not only on the joints but also on the center of slab brings out the maximum stress on the corner of slab and it is expected to make the corner cracks.

• Computers and Concrete
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• 제16권5호
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• pp.775-793
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• 2015

Moisture transport in concrete in atmospheric environment was studied in this paper. Based on the simplified formula of the thickness of the adsorbed layer, the pore-size distribution function of cement paste was calculated utilizing the water adsorption isotherms. Taking into consideration of the hysteresis effect in cement paste, the moisture diffusivity of cement paste was obtained by the integration of the pore-size distribution. Concrete is regarded as a two-phase composite with cement paste and aggregate, neglecting the moisture diffusivity of aggregate, then moisture diffusivity of concrete was evaluated using the composite theory. Finally, numerical simulation of humidity response during both wetting and drying process was carried out by the finite difference method of partial differential equation for moisture transport, and the numerical results well capture the trend of the measured data.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.1-6
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• 1990

Joints are provided in cement concrete pavements to control transverse and longitudinal cracking that occur due to restrained deformations caused by moisture and temperature variations in the slab. But the construction of joints reduces the load-carrying capacity of the pavement at the joints, and pavements have beem deteriorated by cracks at the slab edges along the joints due to traffic loads. Therefore, it is important to analyze the behavior of joints accurately in the design of cement concrete pavements. In this study, the mechanical behavior of cement concrete pavement slabs is analyzed by the plate-finite element model, and Winkler foundation model is adopted to analyze the subgrades. The load transfer mechanism of joints are composed of dowel action, aggregate interlocking, and tied-key action, and the analytical program is developed using these joint models.