• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.417-420
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• 2003

Concrete with low water to binder ratio (W/B) is prone to large autogenous shrinkage. Early age cracking of concrete would be caused by tensile stress induced by large autogenous shrinkage under restrained condition. Therefore, it is necessary to measure autogenous shrinkage to control the early age cracking of concrete. An objective of this study is to investigate the effects of W/B and blast furnace slag (BFS) on autogenous shrinkage of concrete. Autogenous shrinkage of concrete with various W/B ranging from 0.42 to 0.27 and BFS contents of 0, 30 and 50% were measured. Test results show that the autogenous shrinkage of concrete increases as the W/B decreases, and all BFS concretes showed larger autogenous shrinkage than OPC concretes with the same W/B. Moreover, the higher BFS content, the larger autogenous shrinkage.

• International Journal of Concrete Structures and Materials
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• 제18권2E호
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• pp.73-77
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• 2006

This paper shows a study of the efficiency of expansive additive and shrinkage reducing admixture in controlling restrained shrinkage cracking of high performance concrete at early age. Free autogenous shrinkage test of $100{\times}100{\times}400mm$ concrete specimens and simulated completely-restrained test with VRTM(variable restraint testing machine) were performed. Creep and autogenous shrinkage of high-performance concrete with and without expansive additive and shrinkage reducing admixture were investigated by experiments that provided data on free autogenous shrinkage and restrained shrinkage. The results showed that the addition of expansive additive and shrinkage reducing admixture effectively reduced autogenous shrinkage and tensile stress in the restrained conditions. Also, it was found that the shrinkage stress was relaxed by 90% in high-performance concrete with and without expansive additive and shrinkage reducing admixtures at early age.

• Structural Engineering and Mechanics
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• 제49권6호
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• pp.763-773
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• 2014

The recently developed Ultra High Performance Concrete (UHPC) displays outstanding compressive strength and ductility but is also subjected to very large autogenous shrinkage. In addition, the use of forms and reinforcement to confine this autogenous shrinkage increases the risk of shrinkage cracking. Accordingly, this study adopts a combination of shrinkage reducing admixture and expansive admixture as a solution to reduce the shrinkage of UHPC and estimates its appropriateness by evaluating the compressive and flexural strengths as well as the autogenous shrinkage according to the age. Moreover, the coefficient of thermal expansion known to experience sudden variations at early age is measured in order to evaluate exactly the autogenous shrinkage and the thermal expansion is compensated considering these measurements. The experimental results show that the compressive and flexural strengths decreased slightly at early age when mixing 7.5% of expansive admixture and 1% of shrinkage reducing admixture but that this decrease becomes insignificant after 7 days. The use of expansive admixture tended to premature the setting of UHPC and the start of sudden increase of autogenous shrinkage. Finally, the combined use of shrinkage reducing admixture and expansive admixture appeared to reduce effectively the autogenous shrinkage by about 47% at 15 days.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.156-157
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• 2013

As the chemical shrinkage and autogenous shrinkage of paste constitutes a large part of the shrinkage of high strength concrete, a good understanding of characteristics of chemical shrinkage and autogenous shrinkage is essential in order to understand chemical shrinkage and autogenous shrinkage of concrete. In this study, a preliminary study on effect of mineral admixture on chemical shrinkage and autogenous shrinkage of paste was compared.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.687-692
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• 2002

The chemical shrinkage and the autogenous shrinkage have been determined experimentally for cement pastes incorporating different W/C ratio and different amount of the following addition: silica fume, fly ash and sand. The measurement method of the chemical shrinkage and autogenous shrinkage both were the volumetric technique. The silica fume has a effect of increasing the autogenous shrinkage while have a minor effect on the chemical shrinkage. The addition of fly-ash and sand both decreased the amount of chemical shrinkage and autogenous shrinkage.

• 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.

• 한국구조물진단유지관리공학회 논문집
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• 제10권3호
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• pp.97-105
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• 2006

고성능 콘크리트의 자기수축은 초기균열을 유도할 수 있기 때문에 내구성 측면에서 매우 중요하다. 이에 따라, 본 연구에서는 실험을 통해 혼화재료를 혼입한 고성능 콘크리트의 자기수축 특성을 분석한 후 예측모델을 제안하였다. 이를 위해 다양한 실험변수를 가진 시편에 대해 광범위한 실험을 수행하였다. 주요 실험변수는 혼화재료의 종류 및 혼입률로 설정하였으며 물-시멘트비는 30%로 고정하였다. 실험결과 플라이애시를 치환한 경우에는 자기수축량이 다소 감소하였으며, 고로슬래그를 사용한 경우에는 자기수축이 증가하였다. 또한, 수축저감제 및 팽창재의 혼입량이 클수록 고성능 콘크리트의 자기수축은 감소하는 경향을 보였다. 한편, 본 논문에서는 회귀분석을 통해 혼화재료를 사용한 고성능 콘크리트의 자기수축 예측식을 제안하였으며, 제안된 자기수축 예측식은 실험결과와 비교적 일치하였다

• 한국건축시공학회지
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• 제11권6호
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• pp.538-546
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• 2011

This paper is to experimentally investigate the strength and autogenous shrinkage of high strength mortar with the 20 % of water?binder ratio(W/B). In this study, the water substituting liquid(WSL) was used including gasoline, light oil, lamp oil, edible oil, HFE, ethanol, methanol and acetone in order to explore changes in strength and autogenous shrinkage depending on WSL type and replacement. For fresh properties, the replacement of WSL did not affect the fluidity of mortar mixtures considerably, except for ethanol and methanol. However, the replacement of WSL resulted in a slight decrease in flexural and compressive strength. For autogenous shrinkage, the replacement of WSL led to reduce autogenous shrinkage, and especially, the replacement of edible oil led to reduce autogenous shrinkage significantly due to saponification between edible oil and cement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.101-106
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• 2003

This study is to capture autogenous shrinkage in reinforced concrete. The experiment was carried out on total 13 beams. The experiment parameters are a method of curing and reinforcement ratio. Autogenous shrinkage in reinforced concrete beam was experimentally measured. Also, the distribution of autogenous shrinkage and self stress on cross section in reinforced concrete beams were calculated. The experimental results showed that autogenous shrinkage of high strength concrete were significantly higher than that of nomal strength concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.915-918
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• 2008

수화열 및 자기수축은 동일한 수화반응에 의해 필연적으로 발생되는 현상으로서 여러 연구자들에의해 수화온도와 자기수축의 깊은 상관성은 언급되어 왔으나, 아직까지 수화온도와 자기수축의 구체적인 관계에 대한 연구보고는 거의 없는 실정이다. 이에 본 연구에서는 시험체의 단면크기를 달리하여 초기 수화발열 및 자기수축의 특성을 구체적으로 분석한 후, 내부 수화온도와 자기수축의 상관성을 검토하였다. 그 결과, 시험체 단면이 증가할수록 전체적인 내부온도와 자기수축은 증가하였으며, 수화발열상승구간 및 자기수축증가구간에서 발생하는 수화온도 상승량 및 상승률, 자기수축 증가량 및 증가율은 증가하였다. 수화발열상승속도 및 자기수축증가속도가 증가할수록 구간에서 발생하는 수화온도상승량과 자기수축증가량은 증가한 반면, 수화온도상승률과 자기수축증가율은 유사하게 나타났으며, 수화발열상승 속도가 증가할수록 자기수축증가구간의 자기수축증가량과 자기수축증가속도는 증가하였다.