• 콘크리트학회논문집
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• 제14권2호
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• pp.249-256
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• 2002

물-결합재 비(W/B)가 낮고 결합재량이 많은 고성능 콘크리트에는 자기수축이 많이 발생한다. 자기수축은 외부로부터 콘크리트로의 수분 이동이 없는 상태에서 시멘트의 수화반응에 의한 물의 소비 결과로 나타나는 자기건조에 의해 발생한다. 본 연구에서는 플라이애시의 사용 유무에 따른 고성능 콘크리트의 자기수축 특성을 실험을 통해 조사하였다. 또한 시간에 따른 슬럼프 및 플로우 변화, 공기량 등의 굳지 않은 콘크리트의 성질과 압축강도, 탄성계수 등의 역학적 성질에 대한 실험을 수행하였다. 실험결과, W/B가 낮을수록 자기수축이 증가하였으며, W/B가 동일한 경우 플라이애시를 사용하면 재령 초기에 콘크리트의 압축강도가 다소 느리게 발현되지만, 자기수축은 상당히 감소하였다. 또한, W/B가 낮은 고강도 콘크리트일수록 이른 재령에서 보통강도 콘크리트에 비하여 자기수축과 압축강도의 발현률이 크게 나타났다. 이상의 실험 결과로부터, 플라이애시를 사용하여 고성능 콘크리트의 제조가 가능하며 자기수축을 줄일 수 있다는 결론을 얻었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.13-16
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• 2006

This paper investigates the shrinkage behavior of Ultra High Strength(UHSC) having three water-to-cementitious material ratio, 0.20, 0.16, 0.12. All of mixtures have same design compressive strength. Free shrinkage test for autogenous and drying shrinkage using $100{\times}100{\times}400$ prismatic specimen was conducted. On all mixture, Effects of fly ash and blast-furnace slag on each shrinkage test results were also investigated. The largest portion of autogenous shrinkage was observed in UHSC12 (w/b=0.12) and the measured strain was as high as 80% of the total drying shrinkage strain. The autogenous shrinkage of UHSC decreased as the amount of fly ash increased as demonstrated in the literature. However, the results of the effect of blast-furnace slag on autogenous shrinkage were somewhat different from previous researches.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.485-488
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• 2006

The shrinkage properties of the high strength concrete using the cement of Type I, Type III and Type IV was examined, and the following results were obtained. (1) Consideration of the autogenous shrinkage when evaluating appropriately the shrinkage properties of the high strength concrete is indispensable. (2) The autogenous shrinkage prediction expression of JSCE can estimate the properties of autogenous shrinkage of the cement made from korea with in general sufficient accuracy. (3) It is necessary to advance examination which used Korean aggregate about dry shrinkage from now on, and to attain highly accuracy of the autogenous shrinkage prediction expression.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 춘계 학술논문 발표대회 학계
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• pp.69-72
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• 2009

This study reviewed the reduction effect of autogenous shrinkage of high strength mortar by plant edible oils based on existing studies, in an effort to find the method of reducing autogenous shrinkage of high strength concrete. To summarize the results, first as characteristics of fresh mortar, substitution of plant edible oil showed slight reduction in liquidity. Compressive strength was reduce at age of 28 days compared to plain mix regardless of type and substitution ratio. Ratio of change in the length of autogenous shrinkage of high strength mortar by plant oils was found to reduce compared to the plain, and the reduction effect was most satisfactorγ in bean oil.

• 펄프종이기술
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• 제43권5호
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• pp.17-26
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• 2011

Drying behavior and physical properties of HwBKP, SwBKP, and OCC handsheets depending on kneading, refining and wet pressing were analyzed. The maximum drying shrinkage velocity was newly adopted to verify the effect of mechanical treatment of pulps by evaluating drying behavior according to varying the kneading, refining and wet pressing treatments. Those various treatments were changed to evaluate the relationship between the maximum drying shrinkage velocity and handsheets properties. When the drying shrinkage and the maximum drying velocity increased by refining and wet-pressing, handsheets strength was increased. The maximum drying shrinkage velocity showed higher correlation with physical properties of paper than WRV at different refining loads at SwBKP and mixed pulp. At high wet-web dryness, drying shrinkage, the maximum drying shrinkage velocity and strength properties of handsheet were increased. It meant that drying shrinkage behavior was highly affected by not only fibers' shrinkage but also fiber bonding. Kneading pre-treatment for KOCC and SwBKP effectively modified fiber properties and increasing paper strength and drying shrinkage. The effect of kneading pre-treatment was also confirmed by the maximum drying shrinkage velocity. Strength properties of mixed pulp handsheets were not increased by the kneading pre-treatment, although the maximum drying shrinkage velocity and WRV was increased. It meant that fibers network bonding of HwBKP was limited because of ves sels and ray cells' interference for bonding. Therefore in order to improve paper strengths containing HwBKP by mechanical treatments, interference of vessels and ray cells for fiber bondings should be carefully controlled.

• 콘크리트학회논문집
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• 제23권6호
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• pp.741-747
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• 2011

이 연구에서는 강도수준 및 강도발현 속도에 따른 콘크리트의 자기수축과 예측모델의 적용성을 비교하였고, 다양한 양생조건을 적용시켜 자기수축을 검토하였다. 연구 결과에 따르면 콘크리트가 강도가 증가할수록 자기수축이 증가하는 것으로 나타났다. 그러나 동일한 콘크리트 강도의 경우라도 강도발현 속도가 빠른 OPC의 경우 초기 자기수축은 크지만 최종 자기수축은 BFS의 경우가 더 큰 것으로 나타났다. 초기 습윤양생은 자기수축 저감에 영향을 미치며 특히 24시간 이상 습윤양생을 실시하면 최종 자기수축은 크게 감소하는 것으로 나타났다. 기존의 EC2모델은 콘크리트 특성을 적절히 반영하지 못하는 것으로 나타났으며 자기수축을 보다 효과적으로 예측할 수 있는 수정 모델식을 제안하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.95-100
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• 2003

The shrinkage of high strength/high performance concrete is very important property for the good working of a structure since it very often generates early age cracking due to thermal and autogenous shrinkage. Autogenous shrinkage occurs as a result of internal moisture depletion due to hydration and temperature-induced effects. The level of autogenous shrinkage occurring due to hydration also depends on temperature history at very early age. It is necessary that effect of temperature on autogenous shrinkage is investigated since the stress generated due to autogenous shrinkage is quantified. In this study, Effect of hydration heat evolution on autogenous shrinkage of high strength concretes with W/C=25-40% was investigated.

• 한국건축시공학회지
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• 제4권2호
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• pp.81-88
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• 2004

The purpose of this study is to investigate the chemical shrinkage and autogenous shrinkage of high strength cement paste and silica fume and fly ash and sand to cement ratio by the method of volumetric tests, and also investigate the autogenous shrinkage of high measurement method, and compare the results of volumetric test and linear length measurement test. A series of cement paste which have W/C ratio of 25%, 35%, 45% respectively were planed to study the effect of the W/C ratio to the shrinkages, and a series of cement paste which were replaced the cement by the silica fume and fly ash with 5%, 10%, 15% as the mass of cement respectively were planed to investigate the effects of poazolana to the shrinkages. A series of mortar which have a C/S ratio of 1:1, 1:1.5, 1:2 respectively were planed to investigate the shrinkage resistant effect of aggregate.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 추계 학술논문 발표대회
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• pp.1-4
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• 2007

Because reinforced concrete structures were being high more and more in recent year, concrete was being demanded high performance of high strength and high fluidity. But various characteristics must be confirmed besides guarantee of demand strength in ultra-high strength concrete. In ultra-high strength concrete, autogenous shrinkage and drying shrinkage grow big because of a low water cement ratio and much quantity of binder. So dangerousness of crack generation grow big in early ages. And ultra-high strength concrete is influenced by use materials more than ordinary strength concrete. In this study we were examined mix design, atuogenous shrinkage and pumpability of ultra-high strength concrete to apply on the ground.

• 한국구조물진단유지관리공학회 논문집
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• 제13권3호통권55호
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• pp.93-100
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• 2009

본 연구는 대형 대단면 지하공간에 적용하기 위한 고강도 콘크리트의 개발 및 적용을 위한 연구의 일환으로 50MPa급의 고강도 콘크리트의 제조를 위해 플라이애쉬와 고로슬래그미분말의 치환에 따른 최적 배합을 선정하고, 비구속 수축 실험과 수축균열 실험을 통해 정량적으로 평가하였다. 콘크리트의 압축강도는 전배합이 7일 재령에서 30MPa을 넘었고, 28일 재령에서는 설계강도를 모두 안정적으로 획득하였다. 고강도 콘크리트에 고로슬래그를 사용할 경우 자기수축량이 커지고, 다량 치환할 경우 수축변형이 증가하고 강도발현이 지연되어 수축에 의한 균열 발생의 우려가 있다. 혼화재를 다량 치환한 고강도 콘크리트 배합은 수화반응과 건조 효과에 영향을 주는 초기 재령의 양생 조건에 대한 검토가 필요하다.