• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.325-328
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• 2008

Recently increasing interest in high-rise building around the world for more than 100 floor, the trend is the increasing use of high-strength and high-flowable concrete so as of productivity improvements and cost savings to improve the performance of the early strength development. This study is to reach the optimal combination by reviewing the performance of high-rise building which is required. The results, lower the ratio of W/B was an increase in compressive strength and early strength in the use of admixture decreased in the combination of higher replacement ratio of admixture.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.51-59
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• 2012

The cold weather concrete poured in the winter season can cause the problem of the Due to recent high-rise building is made. In this research, the nominal mix of the early strength in concrete tried to be set through the mixing proportion experiment for each empirical variable and each component strength properties for the early strength improvement tries to be examined. In the cold weather concrete experiment, the cement and high early strength (type3) cement improving in OPC than OPC was excellent. The polycarboxylic acid based compound was exposed to be excellent in the intensity revelation properties. Because the using of the fly ash was disadvantageous it was excluded from this experiment. It showed the optimum temperature for the intensity revelation up over $12^{\circ}C$.

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.536-543
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• 2001

Nowadays, with high-stoned and large-sized of structures, high-strength concrete is applicable to various methods. When high-strength concrete is used jointly with system form, seizing on the development of compressive strength at early age is very important in aspect of construction process. Because system form is stripped more faster than ordinary form. But, we have little data of compressive strength before system-form is stripped, and it isn't yet established that decision criterion of the time when system-form is stripped. So this paper deals with the development of compressive strength at early age before system-form is stripped. In this study, the experimental results indicate the boundary of curing temperature and mixing factor that is able to get needful early-strength in the application of slip-form method, and curing temperature must be kept over 15 degrees in winter season.

• Journal of the Korea Institute of Building Construction
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• v.14 no.4
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• pp.322-328
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• 2014

In this study, revelation performance of concrete at early age according to types of cement, water reducing ratio of high performance superplasticizer and mixing of accelerator for early hydration was examined aiming for reduction of construction period of framework through securing strength at early age of concrete. It was observed that strength at early age, 5MPa in 12hours, 14MPa in 18hours, is secured by early strength improvement type cement and using promotion admixture for early hydration which are Sodium persulfate, Potassium hydroxide. Therefore cost reduction is expected to be possible in construction site by reducing construction period of frame work.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.85-94
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• 1999

It was investigated to evaluate the characteristics of cement-flyash paste which was affected the replacement level, curing method and chemical admixtures. The strength of cement-flyash paste was lower than that of cement paste only and the differences increased with increasing the replacement level. However, in steam curing, the strength of cement-flyash pastes was improved and specially, the early strength was effectively increased. The inclusion of $Na_2SO_4$ increased the early strength of cement-flyash paste. In addition, the strength of concrete including 30% of fly ash and $Na_2SO_4$ has improved and obtained the highest strength compared to other concrete mixes.

• Magazine of the Korea Concrete Institute
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• v.10 no.1
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• pp.101-108
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• 1998

시멘트 대체재로 사용하는 플라이애쉬(0, 10 , 30 ,50 %)를 혼입한 콘크리트의강도발현을 관찰하기 위해 각각 21$^{\circ}C$에서 수중양생과 85$^{\circ}C$에서 증기양생방법을 채택하여 실험하였다. 수중양생한 보통 콘크리트는 플라이애쉬 혼입량이 증가할수록 조기재령에서는 낮게 강도발현을 하였으나. 28일 압축강도를 기준으로 하여 물.시멘트비를 변화한 배합비(결합재량 증가)의 실험결과는 조기강도발현이 향상되었다. 특히 플라이애쉬를 30%혼입한 콘크리트는 우수하게 강도발현을 하였다. 그리고 동일한 28일 압축강도를 갖는 배합비(결합재량 증가)에서 증기양생한 플라이애쉬콘크리트는 보통콘크리트보다 강도발현이 비슷하거나 향상되었으며, 양생온도는 플라이애쉬콘크리트의 강도발현에 많은 영향을 미치는 것으로 관찰되었다.

• Journal of the Korea Institute of Building Construction
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• v.13 no.3
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• pp.227-234
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• 2013

In this research, early strength development performance of early strength improvement type ordinary cement which is economically feasible early strength cement(Type III), improved early strength ordinary cement(Type I), was estimated to derive minimum curing temperature and proper water to cement ratio according to cement for early strength development through examination of fresh concrete properties and compressive strength according to water to cement ratio curing $10^{\circ}C$, $15^{\circ}C$ and $20^{\circ}C$ to suggest fundamental data for practical use of early strength concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.541-544
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• 2008

Recently, due to the increase of high-rise buildings construction, many researches for making harden of concrete earlier and remove of forms faster are being performed to reduce construction period. The purpose of this study is to analysis which mixing condition and curing temperature of early strength concrete. Porperties of concrete by the different factors, such as the type of active admixtures, mineral admixtures, curing temperature, the amount of binder, etc. Through the test of concrete using the different type of admixture, PC type was more excellent than PNS type admixture. The concrete Strength remarkably will be able to confirm that decreases from temperature below 12$^{\circ}C$.

• Magazine of the Korea Concrete Institute
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• v.7 no.1
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• pp.126-135
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• 1995

The strength development of PFA concretes were invest~gated in this study. The work undertaken was divided into two parts which considered both the influence of PFA replacement level up to 45% and the effect of cement type at the high PRA leveI(45%). The additiorlal cement considered included a rapdhardemng portland ccnlent. The full range of concrete struc tural grades were studied anti ciight cu~ing contlltiorls covering those 11:ied 111 practlce were examined. The early strength retluced wit11 increasing PFA content. However, post 28days, the reverse was observed. It was posslhle through the use of rapid hardening portland cement at the high PFA level to achieve similar early strength to OPC concrete, with the same benefits noted above also being obtained post 28 days. The compressive strength uf hlgh PYA content concrt:tes at hgh temperature m s found to be higher than the ccmtrol at all ages hoth in water and alr. The same trends were observed at low t.ernperature in air. However, the reverse occur-ed at the low temperature In water.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.237-245
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• 2010

Recently, deflection of the slab during construction periods becoming one of the important issues because of increasing the large-span structures. Early removing the form and support of the slab to achieve the rapid construction cause falling-off in quality of the structures. To reduce these deterioration and make rapid construction, construction of strength and stiffness gain model is needed by the research about the early-age concrete properties. Previous research results indicated that concrete model in existing design codes could not provide the mechanical properties of early age concrete. This paper carried out the concrete compressive strength tests on the curing age at early age stage. Evaluation of the accuracy of compressive strength and modulus of elasticity gain formula in existing various design codes was performed based on this test results, and new design model was proposed. This new model will be useful to develop the new rapid construction methods or prevent the deterioration of the deflection at construction periods. Material tests were performed at 1, 3, 7, 14, 28 curing days, total 159 cylinder style specimens were tested. Based on analyzing the test results, the relationship between compressive strength and modulus of elasticity at early age was proposed.