• Geomechanics and Engineering
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• 제23권2호
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• pp.179-187
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• 2020

Freezing-thawing cycles have significant effect on soils engineering behavior in frozen areas. This effect is more considerable in fine-graded than coarse-grained soils. The objective of this study is improving soil durability and strength in continues freezing-thawing cycles. For getting this purpose mixture of Polyvinyl Acetate (PVAc) and Ethylene Glycol Monobutyl Ether (EGBE) has been added to fine-grained soil and final prepared samples were tested at different freezing-thawing cycles. PVAc was mixed with 1%, 2% and 3% of soil weight. Half of PVAc weight was used as weight of EGBE. Freezing-Thawing cycles were exposed to samples and they were tested at different cycles. Results showed that adding mixture of PVAc+EGBE improved strength and durability of samples up to 10 freezing-thawing cycles. Unconfined compress strength tests were applied to samples and stress and strain of samples were tested on failure time. Behavior of samples was different at different percentages of mixture. Results showed that increasing amount of PVAc from 1% to 2% had more considerable effect on final stress than 2% to 3%. Using higher percentages of PVAc + EGBE mixture leaded to that samples carried more strain before collapsing. Another result gained from tests was that, freezing-thawing effect was more considerable after fourth cycles. It means differences between first and fourth cycles were more considerable than differences between fourth and tenth.

• 한국농공학회지
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• 제33권2호
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• pp.112-119
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• 1991

Some experiments were carried out to investigate the effects of freezing and thawing on the strength and strain characteristics of alluvial silty clay under the different temperatures, loading and moisture conditions. The results were as follows; 1. The soil used was proved to be consisted of silty clay with honey-combed structure, and showed higher dilatancy, frost activity and lower stability in natural state. 2. Soil treated with freezing and thawing cycles showed lower compressive strength compared with the non treated, The strength decreased with incement of freezing and thawing cycles. It's shapes of stress-strain curves were flat and did not formulate a peak while the peak strength of higher moisture content soil decreased with the increment of moisture content. It's decrement ratio was most distinctly shown at the first one cycle of freezing and thawing. 3. The cohesion decreased due to freezing and thawing cycles but internal frcition angle was not changed. 4. The liquid limit decreased with increment of freezing and thawing cycles, and became almost constant after three cycles of freezing and thawing. 5. The strength under simple loading at failure mode was appeared to be higher compared with the cyclic loading after freezing and thawing but initial moisture content effect was not observed. 6. Ice lense was not observed within 50% of ice content ratio but observed over 100%. The higher the ice content ratio, the higher the peak strength. As a matter of fact, it seems that an optimum ice content ratio exists for plastic mode and the least compressive strength.

• 한국농공학회논문집
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• 제46권2호
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• pp.59-66
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• 2004

This study was performed to evaluate the freezing and thawing properties of the high strength concrete using recycled coarse aggregate. The recycled coarse aggregate replaced natural crushed aggregate by 0%, 25%, 50%, 75% and 100%. The compressive strength of the concrete using recycled coarse aggregate showed more than 300 kgf/$cm^2$ at the curing age 28 days. The mass loss ratio by freezing and thawing was less than 1% at all mix type. The relative dynamic modulus of elasticity was decreased with increasing the freezing and thawing cycles. Also, the durability factor by the freezing and thawing was decreased with increasing the content of recycled coarse aggregate. But, the recycled concrete except 100% recycled coarse aggregate showed 60 or more durability factor in the freezing and thawing 300 cycles. Accordingly, these recycled coarse aggregate can be used for high strength concrete.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.190-191
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• 2014

The building insulation materials shall keep their thermal conductivity constant even when the freezing and thawing repeats for over a long time. But, in this condition of repeated freezing and thawing, the organic building insulation material may suffer the degradation in the thermal performance as the gas put into the insulation materials gets out slowly over a long time. Accordingly, in this study, the change in the thermal performance has been tested and evaluated when the repeated freezing and thawing cycles happen.

• 한국지반공학회논문집
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• 제29권1호
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• pp.81-92
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• 2013

본 논문에서는 계절적 환경변화로 인한 동결-융해 반복과정에 노출되는 옹벽의 시간 의존적 거동에 대한 수치 해석 연구 내용을 다루었다. 이를 위해 먼저 동결-융해 반복과정에 노출되는 옹벽에 대한 열-수리-응력 연계해석 기반의 모델링 기법을 정립하였으며 이러한 모델링 기법을 토대로 다양한 온도변화 조건에 대한 매개변수 연구를 수행하였다. 그 결과 다양한 온도변화 특성 중 옹벽의 거동에 미치는 주된 영향인자는 계절적 평균동결온도와 반복회수인 것으로 나타났다. 반면 동결온도의 지속시간에 대한 영향을 검토한 결과 벽체변위 및 수평토압에 큰 영향을 미치지 않는 것으로 검토되었다. 한편, 벽체에 작용하는 수평토압은 동결-융해 작용에 의한 영향을 거의 받지 않는 것으로 검토되어 결국 동결-융해로 인한 벽체 변위 증가 현상은 토압 증가에 그 원인을 찾기 보다는 동결-융해 현상으로 인한 재료적 열화 현상에 그 원인을 찾아야 할 것으로 검토되었다.

• Smart Structures and Systems
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• 제17권1호
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• pp.45-58
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• 2016

Freezing and thawing cycles induce deterioration and strength degradation of concrete structures. This study presumes that a large quantity of contact-type defects develop due to the freezing and thawing cycles of concrete and evaluates the degree of defects based on a nonlinearity parameter. The nonlinearity parameter was obtained by an impact-modulation technique, one of the nonlinear ultrasonic methods. It is then used as an indicator of the degree of contact-type defects. Five types of damaged samples were fabricated according to different freezing and thawing cycles, and the occurrence of opening or cracks on a micro-scale was visually verified via scanning electron microscopy. Dynamic modulus and wave velocity were also measured for a sensitivity comparison with the obtained nonlinearity parameter. The possibility of evaluating strength degradation was also investigated based on a simple correlation of the experimental results.

• 한국지반신소재학회논문집
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• 제13권3호
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• pp.49-58
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• 2014

본 논문에서는 계절적 환경변화로 인한 동결-융해 반복과정에 노출되는 옹벽구조물의 거동에 관한 축소 모형실험 연구 내용을 다루었다. 이를 위해 먼저 동결-융해 과정을 모사할 수 있는 모형 옹벽 실험 장치를 구현하고 실제 계절별 온도 변화 과정을 모사하였으며 다양한 흙의 함수비 및 뒤채움흙의 종류 등을 따른 영향 변화를 고찰을 위한 모형실험을 수행하였다. 실험 결과 계절별 온도변화에 따른 동결-융해 반복 과정은 옹벽의 변위를 증가시키고 토압을 증가시키는 것으로 검토되었다. 아울러 동결-융해 반복 사이클의 영향은 흙의 초기 함수비가 클수록 그리고 세립분을 많이 포함할수록 증가되는 것으로 검토되었다. 본 논문에서는 도출된 연구결과가 실무적 차원에서 지니는 의미에 대한 내용을 기술하였다.

• 한국지반신소재학회논문집
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• 제10권1호
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• pp.19-28
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• 2011

본 논문에서는 동결-융해 반복작용이 화강풍화토의 압축강도 특성에 미치는 영향에 관한 내용을 다루었다. 이를 위해 세립분 함유량을 변화시켜 다양한 시료조건을 조성한 후 동결-융해 시험 환경을 조성한 후 동결-융해 반복작용 사이클을 강제 부가하였다. 시료에 대한 평면변형률압축시험 및 미세입자구조의 변화를 가시적으로 확인할 수 있는 전자주사현미경(SEM) 촬영 및 분석을 수행하였다. 먼저, SEM 분석 결과 화강풍화토는 동결-융해 반복작용에 노출될 경우 입자들이 뭉쳐 간극이 증가하는 추세를 보였다. 한편, 압축강도 특성의 경우 세립분 함유량에 따라 다소 차이를 보이는 것으로 나타났는데 세립분 함유량이 적은 경우에는 강도저하 현상을, 세립분 함유량이 많은 경우에는 강도 증가 현상을 보임을 확인할 수 있었다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.294-300
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• 1999

After researching the physical properties of the concrete included Rice Husk Ash(RHA concrete) and workability of fresh concrete admixed RHA, we have tested durability of RHA-concrete against freeaing and thawing in the winter using rapid freezing and thawing test method(KS F 2456) . There aretwo hypotheses to explain the failure mechanism of a freezing and thawing action. First, the hydraulic pressure in the pores of freezing concrete make an internal stress of concrete structures outbreaking micro crack in the face of concrete, Second, Frost action causing damage to cement paste repeatedly come from soil frost action, freezing water in the capillaries. Initial Relative Dynamic Modulus of Elasticity (DME) was biggest in cae of unit binder weight 600kgf/㎥ and relative dynamic modulus of elasticity increased until 300cycles. In general , initial relative DME was proportional to unit binder weight . Relative DME was decreased in proportion to unit binder weight in the case of 300, 400, 500kgf/㎥ , but relative DME fo the others remained more than 90% until 300 cycles. It was not good effect of intermixed RHA to concrete in case of below unit binder weight 300kgf/㎥ and the resistance of freezing and thawing was not good either.

• Structural Engineering and Mechanics
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• 제90권5호
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• pp.481-492
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• 2024

This research examined the mechanical behavior of fiber-reinforced concrete at unstable environmental conditions. Concrete composites with varying percentages of steel and glass fibers were analyzed. Compressive, indirect tensile, and fracture toughness properties were evaluated using the Edge Notched Disc Bend (ENDB) test under freezing-thawing and acidic environments and the results were compared with normal conditions. Steel fibers decreased the strength in the specified cycles, while glass fibers showed a normal strength trend. The compressive, tensile and fracture toughness of the samples containing 1.5 vol.% fibers showed a 1.28-, 2.13- and 4.5-fold enhancement compared to samples without fibers, after 300 freezing-thawing cycles, respectively.