• 한국건설순환자원학회논문집
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• 제2권3호
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• pp.180-187
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• 2014

본 연구에서는 시멘트 사용량을 저감하고 다량의 혼화재를 사용하여 고강도 콘크리트 제조 과정에서 시멘트에 의한 $CO_2$ 발생량을 감소시킬 목적으로 혼화재 및 무기계 자극제를 사용한 고강도 콘크리트의 역학적 특성을 평가하였으며, HVMA 결합재 도출과 W/B 변화 및 양생온도에 따른 HVMA 고강도 콘크리트를 실험하였다. 실험결과, 다량의 혼화재와 무기계 자극제인 열병합애시와 무수석고를 혼합 사용한 HVMA 결합재 배합을 설계하였으며, 설계된 HVMA 결합재를 사용할 경우 W/B 26% 수준에서 HVMA 고강도 콘크리트 배합이 유동특성과 역학적 특성이 양호한 것으로 나타났다. 또한 HVMA 결합재를 사용한 고강도 콘크리트의 양생온도 영향을 검토한 결과, 양생온도 $20^{\circ}C$ 이상 확보한 경우에는 50MPa 이상의 고강도 HVMA 고강도 콘크리트 제조가 실용화 가능성이 높은 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제1권2호
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• pp.123-130
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• 1997

The effect of experimental factors on the Freeze-Thaw durability in the High Strength Concrete has been analyzed and investigated with [DESIGN of EXPERIMENT: L16). The Experimental parameters included the type of aggregate and mixer, the conditions of aggregates, and the difference of mixing temperature, procedure and placing, etc. It is aim of this study to provide the fundamental data on the effect of various factors on the frost resistance of high strength concrete for the practical use and research data accumulation of durability inspection. The results of this experiment indicate that the freeze-thaw durability of high strength concrete is markedly affected by the coarse aggregate source, mixing temperature and curing conditions.

• 대한치과기공학회지
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• 제42권3호
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• pp.208-212
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• 2020

Purpose: This study aimed to analyze the shrinkage and expansion strain of ultraviolet (UV)-cured resin according to the wavelength of the light source and compare the shrinkage and expansion. Methods: We prepared the mold with according to the ISO 4049 specimen. The size of the circle in the mold was prepared with a height of 6.02 mm and a diameter of 4 mm. UV-curable resin for three-dimensional (3D) printing was injected into the circular mold. The control group was irradiated with a wavelength of 400~405 nm using UV-curing equipment (400 group), and the experimental group was irradiated with a wavelength of 460~465 nm (460 group). Both groups were produced ten specimens. The produced specimen was first measured with a digital micrometer. After the first measurement, the specimen was immersed in a constant temperature water bath for 15 days, after which the second measurement was performed, and the third measurement was taken after 30 days. The measured values were analyzed using the independent sample t-test (α=0.05). Results: In the non-immersion water tank, the contraction was 0.9% in the 400 group and 1.3% in the 460 group. In the constant temperature bath, the expansion was high at -0.4% in the 400 group for 15 days, and the smallest expansion was -0.03% for the 400 group for 30 days. There were significant differences between the two groups (p<0.05). Conclusion: The 400 group had a lower UV resin specimen strain than the 460 group. Therefore, it is recommended to use the wavelength required by the UV-curing resin.

• 한국응용과학기술학회지
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• 제24권2호
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• pp.149-159
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• 2007

In order to prepare high-solid coatings, acrylic resins, HSCs [poly (EA/EMA/2-HEMA/CLA)] that contain 90% solid, were synthesized by copolymerization of ethyl acrylate (EA), ethyl methacrylate (EMA), 2-hydroxyethyl methacrylate (2-HEMA) and caprolactone acrylate (CLA). The high-solid coatings named as CHSCs (HSCs/HDI-trimer) were prepared by the curing reaction between the acrylic resins containing 90% solid contents and the isocyanates (HDI-trimer) curing agent room temperature. The curing behavior and various properties were examined on the film coated with the both high-solid coatings. The glass transition temperatures $(T_g)$ of CHSCs increased proportionally with increasing the predicted $T_g$ value by Fox equation, and had nothing to do with the solid contents. The prepared film showed good properties for $60^{\circ}$ specular gloss, impact resistance, cross-hatch adhesion and heat resistance, and bad properties for pencil hardness, drying time, and pot-life. Among the film properties, the heat resistance was very excellent and could be explained by the introduction of functional monomers of CLA.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 추계 학술논문 발표대회
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• pp.49-52
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• 2007

Recently, as architectural concrete structures become high-rise and megastructured, concrete become high-strengthened and, by ensuring products of more stability, air compression and rationalization of construction are required. In general, product management test of precast concrete member, specimen for management cured in the same condition with precast concrete member is substitutively used for strength test. However, large cross-sectional precast concrete members such as columns show large temperature increase in manufacturing process not only by external heating but also by concrete itself's hydration heating. Therefore, it is expected that specimen for management to predict strength and compression strength of precast concrete member shows different temperature history and strength characteristics. Concerning this, in order to suggest temperature history and strength characteristics of high strength mass concrete suitable for precast concrete application, this study comprises the inclusive investigations on the relations between management specimen with similar temperature history and core strength, and the strength characteristics per member cross-section dimensional value and per water-bonding material ratio value.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.394-401
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• 1996

This paper persents the crack control of mass concrete in massive machine foundation. The dimension of the machine foundation is 52.6m$\times$14.4m$\times$8.5m. The one distinctive characteristic of mass concrete is thermal behavior. Since the cement-water reaction is exothermic by nature, the temperature rises inside the massive concrete structure. When the heat is not quickly dissipated, it can be quite high. Significant tensile stresses may develop from the volume change associated with the increase of decrease of temperature within the mass concrete structure. To avoid occurrence of harmful cracks due to hydration heat, special attention shall be given to the construction of mass cnocrete structures. The temperature control system of mass concrete is proposed in this paper. This system contains a discussion of materials and concrete mix proportioning, thermal analysis, curing method, temperature control, and measurement of hydration heat. As will be seen throughout the paper, the proposed temperature control system have a great effect on the temperature-related cracks on mass concrete structures.

• 한국세라믹학회지
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• 제53권6호
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• pp.707-711
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• 2016

A small diameter of SiC fiber mat can produce much higher heat under microwave irradiation than the other types of SiC materials. Fabrication of high strength SiC fiber consists of iodine vapor curing on polycarbosilane precursor and heat treatment process. The curing stage of polycarbosilane fiber was maintained at $150-200^{\circ}C$ in a vacuum condition under the iodine vapor to fabricate a high thermal radiation SiC fiber. The structure and morphology of the fibers were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG) and scanning electron microscopy (SEM). In this study, the thermal properties of SiC fiber mats under microwave have been analyzed with an IR thermal camera and its image analyzer. The prepared SiC fiber mats radiated high temperature with extremely high heating rate up to $1100^{\circ}C$ in 30 seconds. The fabricated SiC fiber mats were not oxidized after the heat radiation process under the microwave irradiation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.93-96
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• 2008

This research performed strength improvement analysis after evaluating strength characteristics by estimated temperatures to evaluate the real time strength performance of 50 to 80 MPa high performance concrete equipped with heat resistance, and the results are as follows. The lesser W/B and the lesser target slump flow value difference, compression strength was shown to increase, and the more curing temperature becomes, the strength increased accordingly. According to the correlation review result of strength improvement analysis by estimated temperature change performed using logistic analysis model, the compression strength value predicted with logistic curve expression and the compression strength value measured in experiment were shown to have similar correlation, and the strength improvement analysis value by logistic model was shown to be estimated good when W/B is high.

• 한국건축시공학회지
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• 제16권6호
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• pp.529-534
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• 2016

칼슘실리케이트계 무기단열소재는 주원료로 시멘트를 90%를 사용하는 다공성 무기단열소재이다. 기존 무기단열소재와 달리 고온의 수화반응 처리가 없기 때문에 가격이 저렴하며, 불연소재의 원료를 사용하여 화제의 위험성도 적다. 칼슘실리케이트 단열소재는 $0.13g/cm^3$의 밀도와 0.050W/mK이하의 우수한 열전도도를 갖는 단열소재이다. 칼슘실리케이트 단열소재는 경량화 될수록 내부 기포를 다량 함유해야 하며 기포를 다량 함유함에 따라 단열성 또한 우수해진다. 본 연구에서는 다량의 기포를 함유하며 일정강도발현을 목표로, 칼슘실리케이트계 무기단열소재의 주성분인 시멘트가 수화반응에 따라 초기 및 장기강도발현하는 특성을 이용하여 칼슘실리케이트계 무기단열소재에 적용하여 물리적 특성을 알아보고자 하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.430-435
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• 1997

This paper presents the material properties and production of 1400kg/$\textrm{cm}^2$ ultra high-strength concrete in consideration of the history of hydration temperature for the practical utilization. A series of laboratory tests were conducted to optimize the mix proportion and then the full-scall mock up tests were performed to investigate the practicability. The thermal sensors were installed prior to concrete casting into the walls and columns, to measure the hydration temperature during the hardening process, which is inevitable to select the most appropriate curing scheme.