• 한국농공학회지
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• 제20권1호
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• pp.4599-4613
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• 1978

This study was intended to investigate the effects of bituminous material content of soil-cement mixtures on their durability. For the purpose, unconfined compressive strength test, Freeze-thaw test, and wet-dry test were performed with three types of soil. Each type of soil was mixed with three levels of cement content and each soil-cement mixture was mixed with four levels of bituminous material content. For the unconfined compressive strength test, Freeze-thaw test and wet-dry test, 324, 108, and 108-specimens were prepared respectively. Unconfined compressive strength was measured at age of 7-days, 14-days and 28-days using 108-specimens in each age. The soil-cement loss rate due to freeze-thaw and wet-dry were calculated after 12 cycles of test using 108-specimens in each test. The results are summarized as follows : 1. Optimum moisture content was increased with increase of cement content, but maximum dry density was changed irregulary with increase of the cement content. 2. The unconfined compressive strength was increased with increase of cement content, bituminous material content and curing age. Cement is more effective factor than bituminous material on unconfined compressive strength of soil-cement Mixture. 3. It is estimated as the most economical cement content that the recommended cement content of A.S.T.M. because increasing rate of unconfined compressive strength at age of 28-days was low when cement content is above the recommanded cement content of A.S.T.M. among all types of soil. 4. Although a portion of cement content is substituted for bituminous material, the necessary unconfined compressive strength can be obtained. 5. The soil-cement loss was more influenced by wet-dry than Freeze-thaw 6. The bituminous material is more effective on the decrease of soil-cement loss than increase of unconfined compressive strength 7. The void ratio of soil-cement mixture was changet irregularly with increase of cement content, but that was decreased in proportion to the increase of bituminous material content. 8. The regression equation between the unconfined compressive strength and soil-cement loss rate were obtained as table 7.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.227-233
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• 2008

Porous concrete has large continuous voids of 20-30 % by volume, and this concrete is attractive as environmental material in Japan i.e. permeable road pavement, river bank protection with vegetation and green roof system which influence thermal environment. It is necessary to confirm the frost resistance when constructing porous concrete structure in cold region. However applicable test method and evaluation criterion of porous concrete has not defined yet. Therefore, the object of this study is to investigate the frost resistance of porous concrete and this investigation attempts to address this concern by comparing 4 kinds of specified freezing and thawing tests methods (JIS A1148 procedure A/B and RILEM CIF/CDF test) in consideration of actual environment. RILEM freeze-thaw tests are different from JIS A1148 freeze-thaw tests, which are widely adopted for evaluating the frost resistance of conventional concrete in Japan, in water absorption, cooling rate, length of freezing and thawing period, and number of freezing and thawing cycles. RILEM CIF test measures internal damage and is primarily applicable for pure frost attack. CDF test is appropriate for freeze-thaw and de-icing salt attack. JIS A1148 procedure A/B showed extremely low frost resistance of porous concrete if the large continuous voids were filled with water and the ice expansion in the large continuous voids set in during cooling. Frost resistance of porous concrete was improved by mixing coarse aggregate (G7) which particle size is smaller and fine aggregate in JIS freezing and thawing tests. RILEM CIF/CDF test showed that freeze-thaw and de-icing resistance of porous concrete was seems to be superior in that of conventional concrete.

• 자원환경지질
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• 제52권6호
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• pp.587-593
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• 2019

본 연구에서는 다초점 레이저 스캔 현미경 (confocal laser scanning microscope, CLSM)을 활용한 균열의 생성 및 성장에 대한 분석을 실시하기 위해 가압조건 및 동결/융해를 통하여 풍화를 가속시킨 실험을 수행하였다. 실험에 적용된 가압조건은 시료 3개에 각 가압틀을 이용하여 50 MPa, 55 MPa, 70 MPa로 설정하였으며 조건을 유지한 상태로 동결/융해 실험을 실시하였다. 실시된 동결/융해 실험에서 온도 조건은 -20~40℃로 설정하고, 설정 온도까지 도달시간 1시간, 유지시간 2시간을 기본으로 6시간을 1주기로 하였다. 이를 바탕으로 동결/융해 매 20주기가 끝난 후 CLSM을 활용하여 시료의 표면을 관찰하였다. 그 결과 동결/융해 실험이 반복되면서 각 시료에 발생한 균열의 개수가 7개, 10개, 19개로 가해진 압력에 따라 차이를 보였고 균열의 누적 길이도 가해진 압력이 큰 시료에서 길게 나타났다. 측정한 균열의 누적 길이와 동결/융해 실험 주기를 통해 계산한 균열의 성장 속도 역시 압력의 세기에 따라 높은 압력을 가한 시료에서 빠르게 나타났다.

• 한국임상수의학회지
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• 제17권1호
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• pp.121-128
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• 2000

The effects of cryosurgery on tear production and histological changes of the third eyelid were studied in dogs. Clinically normal 12 mixed breeds weighing 2∼6 kg were divided into three groups and treated as follows; 45 seconds double freeze-thaw treated group, 60 seconds double freeze-thaw treated group and 90 seconds double freeze-thaw treated group. The significant decrease of the tear production after cryosurgery was shown in all groups throughout the observed periods(p<0.05). However, there was no difference among groups. The main complications after cryosurgery were chemosis and conjunctival injection. Other complications such as eyelid edema, eyelid depigmentation and keratitis were more preominent in group III compared to those of groups I and II. On histopathological examination, chronic inflammatory changes and regeneration of the third eyelid glands were noted in group I and predominated loss of the third eyelid glands and necrosis of hyaline cartilage were observed in group III However, such changes were less appeared in group II. The results of this study suggested that double freeze-thaw cryosurgery for 60 seconds on the third eyelid glands would be the most effective method for treating tear staining syndrome.

• 터널과지하공간
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• 제6권2호
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• pp.144-156
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• 1996

The deformation behaviors under uniaxial compressive cyclic loading were investigated for fresh rocks and freeze-thaw cycled samples. The Pocheon granite which is one of the most popular building stone in Korea was selected for tests. 0.5 Hz and 50% of dynamic strength were used as test conditions for frequency and fatigue span, respectively. For freezethaw procedure, sample were frozen for 3 hours under the temperature of -2$0^{\circ}C$ and then followed 3 hours thawing under the temperature of +2$0^{\circ}C$. Twenty seven samples were used as untreated and seventy three for freeze-thaw samples. No failure occurred up to 15000 cycles at the stress level of 60% of dynamic strength, indicating that the lowest strees level for fatigue failure may be around 60% of dynamic strength. Permanent strain and damping capacity curves show that there were three stages when rock behaves like under creep. Young's moduli were increased and Possion's ratios were decreased with the increase of the number of cycles. Possion's ratios varied more rapidly than Young's moduli did with the increase of the number of cycles. This may represent that most microcracks developed by fatigue stress are parallel to the axis of loading. The deformation behavior of freeze-thaw cycled samples were almost the same as that of untreated samples. However, the result of freeze-thaw cycled samples showed lower regression constant, indicating that the physical durability of rock is much lowered because of cyclic temperature variation.

• Geomechanics and Engineering
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• 제14권3호
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• pp.301-306
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• 2018

Stabilization of clayey soil has been studied from past to present by mixing different additives to the soil to increase its strength and durability. In recent years, there has been an increasing interest in stabilization of soils with natural pozzolans. Despite this, very few studies have investigated the impact of pozzolanic additives under freeze-thaw cycling. This paper presents the results of an experimental research study on the durability behavior of clayey soils treated with lime and perlite. For this purpose, soil was stabilized with 6% lime content by weight of dry soil (optimum lime ratio of the the soil), perlite was mixed with it in 0%, 5%, 10%, 20%, 25% and 30% proportions. Test specimens were compacted in the laboratory and cured for 7, 28 and 84 days, after which they were tested for unconfined compression tests. In addition to this, they were subjected to 12 closed system freeze-thaw cycles after curing for 28 days. The results show that the addition of perlite as a pozzolanic additive to lime stabilized soil improves the strength and durability. Unconfined compressive strength increases with increased perlite content. The findings indicate that using natural pozzolan which is cheaper than lime, has positive effect in strength and durability of soils and can result cost reduction of stabilization.

• 콘크리트학회지
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• 제10권4호
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• pp.163-169
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• 1998

폐콘크리트로부터 생산된 재생굵은골재를 쇄석골재 대신하여 콘크리트에 활용하기 위하여 압축강도, 휨강도의 특성 및 동결융해저항성을 측정하였다. 쇄석골재로 일정비율 대체한 재생콘크리트는 보통콘크리트에 비하여 압축 및 휨강도가 낮았으며, 플라이애쉬 혼입한 재생콘크리트는 보통콘크리트와 비슷한 강도변화를 나타냈다. 동결융해저항성은 물.시멘트비, 재생굵은골재 대체율 그리고 플라이애쉬의 첨가량에 따라 차이점을 보였으나. 물.시멘트비가 낮을수록 플라이애쉬 혼입량이 적을수록 그리고 재생굵은골재 대체율이 80%일 때 저항성이 가장 우수한 것으로 나타났다.

• 터널과지하공간
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• 제13권3호
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• pp.215-224
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• 2003

자연 상태에서의 물리적 풍화를 실험적으로 재현하기 위해서 동결-응해 시험을 실시하였다. 시험 과정에서 탄성파 속도, 흡수율, 무게 및 부피 변화 등의 물리적 성질을 측정하였으며, 시험 전 및 시험 종료 후에 일축압축시험을 실시하여 강도 및 탄성 계수의 변화도 조사하였다. 시료의 무게 및 부피 변화는 풍화의 진전 정도와 명확한 상관관계를 보이지 않았으나 탄성파 속도와 일축압축강도 및 탄성계수는 풍화가 진행되면서 감소함을 보였다. 시험 결과는 암반 사면의 장기적 안정성 평가에 이용될 수 있을 것으로 기대된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.261-262
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• 2009

우리나라에서 시멘트 콘크리트 포장에서 알칼리-골재 반응에 의한 파손이 보고된 후, 알칼리-골재 반응에 대한 대책 방안 수립이 연구되고 있다. 본 연구에서는 시멘트 콘크리트 포장에서 알칼리-골재 반응을 억제하기 위한 방법으로 프리믹스 방식으로 플라이애시를 전체 바인더 증량(시멘트 + 플라이애시)의 20%를 치환하는 방법을 적용하였다. 동결-융해 실험에서 공기량 3% 이하의 시편을 제외하고 모두 시편의 3사이클 후 상대동탄성계수는 90 %이상이었고, 스케일링 실험에서 50 사이클 후 무게 손실량이 1kg/$m^3$이하가 측정되어 내구성이 우수한 것을 알 수 있었다.

• 터널과지하공간
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• 제21권2호
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• pp.145-150
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• 2011

사암과 안산암에 대한 풍화특성을 살펴보기 위하여 동결융해 반복시험을 실시한 후, 두 암석에 대한 중량 감소율, 탄성파속도, 일축압축강도 등의 물성 변화를 측정하였다. 중량 변화의 경우 두 암석 모두에서 동결 융해 반복 횟수가 증가함에 중량이 감소하는 경향을 보였다. 특히 안산암에서는 중량 감소 경향이 시험편에 따라 매우 불규칙하게 나타났다. 탄성파속도 변화에 있어서 사암은 5%이상의 감소 경향을 보였으며, 안산암은 동결융해 반복시험 500 사이클까지 탄성파속도 변화가 거의 없다가 1000 사이클부터 5%이상의 감소 현상을 보였다. 이것은 안산암이 비교적 풍화에 강한 암석인 반면, 사암은 풍화받기 쉬운 암석인 것을 의미한다. 또한 안산암의 탄성파속도 변화 양상은 안산암의 중량 변화와 일치한다. 사암의 일축압축시험 결과에서 일축압축강도는 동결융해 반복시험 초기 사이클 구간에서 미미한 강도저하를 보이다 64 사이클부터는 불규칙한 경향을 나타냈다. 결과적으로, 중량 감소가 적은 암석 시험편일수록 강도저하율도 작게 나타났다.