• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.271-272
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• 2010

This thesis is researched to compare the shrinkage of lightweight concrete depending on depth to normal concrete. It is used artificial lightweight aggregate which has 20% of pre-absorb value by lightweight concrete. When water-binder ratio is 30%, average shrinkage of lightweight concrete section decreased than normal concrete, but differential shrinkage of lightweight concrete section increased. However water-binder ratio is 40%, average shrinkage and differential shrinkage of lightweight concrete section decreased than normal concrete.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.159-169
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• 2010

A multiphysics model analysis including moisture transport, heat transfer and solid mechanics and experiments on the normal and light weight concrete were carried out in order to study the effect of preabsorbed water in the light weight aggregates on the drying and shrinkage characteristics of concrete. Consequently, with fixed water-cement ratio, loss of water content of normal and light weight concrete were compared and the results showed that the lightweight concrete lost less moist than the normal concrete in early age and long term which was by moist supply effect. Accordingly, shrinkage strain size and distribution of lightweight concrete were decreased, and shrinkage reducing effect was efficient in early age with water cement ratio 0.3 and in both early age, and long term with water cement ratio 0.5. The comparison of analysis results and exaperimental results indicate that characteristic values of moisture transport and the relation humidity and shrinkage strain from this study are resonable for application for other differential shrinkage analysis in lightweight concrete.

• Magazine of the Korea Concrete Institute
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• v.4 no.4
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• pp.115-122
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• 1992

폐쇄 폐콘크리트를 재활용한 재생콘크리트의 강도특성을 천연골재를 사용한 일반콘크리트와 비교하였다. 동결융해 처리수의 압축강도와 3점휨 재하시험하의 변형율을 측정하였다. 재생콘크리트는 동결융해 처리 후 압축강도 보존율이 더 높았다. 재생콘크리트는 또한 높은 변형율과 처짐에 민감함을 보였으나 파괴와 관련된 다른 성질들은 일반콘크리트와 유사하거나 더 좋은 것으로 나타났다. 그러므로 폐콘크리트를 구조용 콘크리트 제조에 재 사용이 가능할 것으로 보여진다. 그러나 실제 사용을 위하여는 콘크리트에 있어서 중요한 성질인 압축강도가 더 증진되어야 하며 최대 변형율도 보다 자세히 점검되어야 한다.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.11-20
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• 2009

By using the artificial lightweight aggregate for the natural aggregate depletes and destruction of environment and the application of lightweight concrete in structure, the lightweight concrete is manufactured. The fundamental characteristics by the waterbinder ratio was evaluated. It is suggested the method to control of pre-absorbed water of the lightweight aggregate. Lightweight concrete with pre-absorbed aggregate has similar characteristics compared to normal weight concrete regardless of water-binder ratio. According to the water-binder ratio, the drying condition, and the rebar, the unit mass of the lightweight concrete showed the reduction of 14.6${\sim}$21.0% as the range of 1,668${\sim}$1,998 $kg/m^3$ in comparison to the normal weight concrete. The lightweight aggregate pre-absorbed water showed the deferent evaporation quantity according to the water-binder ratio. As the water-binder ratio is lower, the oven dry vapour water is larger, therefore the internal curing water is increasing. In the same water-binder, comparing the normal concrete the lightweight concrete shows lower compressive strength which is due to the different strength of an aggregate. In the air dry curing, the normal weight concrete has a lower strength improvement effect in w/c 0.3 than the ratio 0.4 and 0.5. However, the strength improvement effect has increasing as the water-binder ratio was low in the light concrete.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.76-82
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• 2002

The rapid-set cement concrete causes high hydration temperature and nay result in a high drying shrinkage and shrinkage-induced cracking. This problem may be fixed by incorporating polypropylene fibers in rapid-set cement concrete, because of increased toughness, resistance to impact, corrosion, fatigue, and durability. A series of concrete drving shrinkage tests was peformed in order to investigate the shrinkage properties of polypropylene fiber reinforced concrete with experimental variables such as concrete types, fiber reinforcement, W/C ratio, with and without restraint. Uni-axially restrained bar specimens were used for the restrained shrinkage tests. The results were as follows; The dry shrinkage of rapid-set cement concrete was much lessor than that oi OPC, probably because of smaller weight reduction rate by early hydration and strength development. The constraint and bridging effects caused by polypropylene fibers were great for the rapid-setting cement concrete when compared with that of plain concrete, and this resulted In increased resistance against tensile stress and cracking.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.349-352
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• 2008

The research conducts a four-point loading test by making two reinforced concrete beams(HSCC test specimen and conventional concrete test specimen) in order to apply an HSCC with a normal strength(30MPa) to a structure. Also, it compares and analyzes the characteristics of the flexural behavior of HSCC and conventional concrete. The stiffness and ductility of the test specimens of HSCC and conventional concrete show similar behavior, but HSCC is more effective in crack control than conventional concrete. The result of the research demonstrates that HSCC can be applied in the construction site.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.253-254
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• 2010

This study is about evaluation of shrinkage of concrete used oxidized EFS(electric-furnaceslag) aggregate. As a result, the shrinkage of concrete used oxidized EFS aggregate is decreased to about 40% in proportion to replacement of oxidized EFS aggregate in total aggregate volume.

• Magazine of the Korea Concrete Institute
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• v.9 no.1
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• pp.195-206
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• 1997

비선형 layered 유한요소법과 비선형 프로그래밍 기법에 의하여 주어진 기존의 철근콘크리트 보의 휨강도 및 연성을 근사하게 나타낼 수 있는 강섬유고강 철근콘크리트 보(Reinforced Steel Fibrous Concrete Beam : RSFC Beam)의 인장 및 압축철근량, 강섬유의 혼입률 등을 산정하였다. 개발된 모델을 이용하여 콘트리트의 압축강도 및 철근비가 서로 다른 일반 철근콘크리트 보에 있어서 강섬유보강 콘크리트를 사용할 경우, 기존 철근을대체하는 강섬유의 량과 또한 이로 인한 인장 \ulcorner 압축 철근량의 변화량을 조사하였다. 기존 문헌에 나타난 강섬유보강 콘크리트보의 전간강도식을 이용하여 일반 철근콘크리트보와 비교하여 강섬유보강 철근콘크리트 보에서 증가될 수 있는 스터럽의 간격을 산정하였다.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.541-548
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• 2003

This study is to investigate the temperature curve and development of compressive strength due to the curing conditions and to evaluate the optimum curing condition of test specimens showing the same development of strength to that of real structures in cold weather. The results of temperature curve with curing conditions in mock-up tests showed the trend of decrease plain concrete with insulation form, plain concrete with heating, concrete with accelerator for freeze protection, and control concrete in turn. The strength development of plain concrete of inside and outside of shelter showed the very slow strength gains due to early freezing, but that of concrete with accelerator for freeze protection showed the gradual increase of strength with time. From this, it is clear that accelerator for freeze protection has the effects of reducing the freezing temperature and accelerating the hardening under low temperature. Strength test results of small specimens embedded in members and located in insulation boxes at the site are similar to that of cores drilled from the members at the same ages, thus it is clear that these curing methods are effective for evaluation in-place concrete strength.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.135-146
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• 1996

In this study, the properties of super flowing concrete containing fly ash were experimentally investigated and compared with those of ordinary concrete. Tests were carried out on five types of super flowing concrete mixes containing fly ash and three types of ordinary concrete mixes without fly ash. Flow test, 0-funnel test, box test, L type test and slump test were carried out to obtain the properties for flowability and workability of fresh concrete. The mechanical properties of hardened concrete were also investigated in terms of compressive strength, splitting tensile strength, modulus of elasticity, creep and drying shrinkage. In fresh concrete, it was found that super flowing concrete had excellent workability and flowability compared with ordinary concrete, and had self-compactable performance. Super flowing concrete *also had good mechanical properties at both early and late ages with compressive strength reaching as high as 40 MPa at 28 days. The creep deformation of super flowing concrete investigated was relatively lower than that of ordinary concrete, but drying shrinkage was much higher.