• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.818-821
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• 2004

Generally, the high performance concrete of drying cracking and autogenous shrinkage are tend to be increased. In the previous study, it was found that the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separtely using method of that. This study is to investigated the durability of high performance concrete using expansive additive and shrinkage reducing agent. Test results showed that the high performance concrete using expansive additive and shrinkage reducing agent had very good not only the durability performance such as salt injury, carbonation, resistance to freezing-thawing and permeability but also the resistance to shrinkage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.787-794
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• 2006

Generally, high performance concrete has characteristics such as low water-cementitious material ratio, lots of unit binder powder, thus the heat of hydration, autogenous shrinkage are tend to be increased. This study is to investigated the effect of the expansive additive and shrinkage reducing agent on the shrinkage properties of high performance concrete as a study to develop the reduction technology of the concrete shrinkage. Test results showed that the expansive additive and shrinkage reducing agent were effective the reduction of shrinkage of high performance concrete. Especially, the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separately using method of that. Also, it analyzed that the combination of expansive additive of 5% and shrinkage reducing agent of 1% was the most suitable mixture, considering to the fluidity, strength and shrinkage properties.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.789-792
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• 2005

Development of high-strength concrete and improved durability has brought new opportunities to the construction industry. However, some attention was given to characteristics of such concrete, in particular with respect to their cracking sensitivity. It has been argued and demonstrated experimentally that a low water/cement ratio concrete undergoes shrinkage due to self-desiccation. This so-called autogenous shrinkage cracking is a major concern for concrete durability. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive for reducing the risk of shrinkage-introduced cracking. This paper aimed at forecasting deformation of high strength cement paste with expansive additive for early age.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.569-577
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• 2015

The aim of this study is to qualitatively evaluate the cracking control effects of expansive concrete used in reinforced concrete building. The result of experiments in laboratory shows that autogenous shrinkage and drying shrinkage are suppressed by using expansive additive. The tensile stress-strength ratio is lower in expansive concrete than normal concrete under fully restrained condition. Compression stress could be effectively generated in early age in the walls in buildings by the use of expansive additive, and tensile stress due to drying shrinkage at later age eventually decreased. Additionally, visual observation at long-term ages shows that the cracking area of expansive concrete was approximately 35% of normal concrete, which confirms that the use of expansive additive reduces concrete cracking in reinforced concrete buildings.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.785-793
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• 2003

This study is intended to analyze the effectiveness of expansive additive, shrinkage reducing agent and combination of the two to reduce the autogenous and drying shrinkage of high performance concrete using mineral admixture such as fly ash, blast furnace slag powder and silica fume. According to results, when expansive additive and shrinkage reducing agent are mixed within an appropriate mixing ratio, fluidity and air content are not influenced, and the enhancement of compressive strength is favorable at the age of 91 and 180days. At the mixing ratio of expansive additive of 5% and 10%, the autogenous and drying shrinkage is reduced by 32∼68% and 25∼49% respectively in comparison with plain concrete. And they are reduced by 18∼34% and 16∼26% respectively at the mixing ratio of shrinkage reducing agent of 0.5% and 1.0%, compared with plain concrete. The mixture of EA-SR combined with expansive additive and shrinkage reducing agent is most effective for reduction of shrinkage. Therefore, it is considered that the using method in combination with expansive additive and shrinkage reducing agent is effective to reduce the shrinkage of high performance concrete using mineral admixture such as fly ash, blast slag powder and silica fume.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.283-288
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• 1999

This study is performed to evaluate slump , air content, compressive strength and length change ratio of non-shrinkage high strength ocncrete is achieved by 10% expansive additive contained. The length change ration of non-shrinkage high strength concrete which is in water curing, shows 0.055% expansion in 10% expansive additive contained concrete and 0.308 expansion in 20% expansion additive contained concrete when it is curing 28 days.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.581-586
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• 2005

High-performance concrete (HPC), which is particularly sensitive to self-desiccation, is required to be durable even in severe environmental conditions, i.e. costal area, cold district, etc. However, in recent years, some attention was particularly given to cracking sensitivity of high performance concrete at early age. It has been argued and demonstrated experimentally that such concrete undergoes autogenous shrinkage due to self-desiccation at early age under restrained condition, nd, as a result, internal tensile stress may develop, leading to micro cracking and macro cracking. This shrinkage-introduced crack produces a major serviceability problem for concrete structures. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive additive for reducing the risk of autogenous shrinkage-introduced cracking. However, the research on hydration model of expansion additive has been hardly researched up to now. This paper presents a study of the hydration model of Ettringite-Gypsum type expansive additive. As a result of comparing forecast values with experiment value, proposed model is shown to expressible of hydration of expansive additive.

• Geomechanics and Engineering
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• v.15 no.6
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• pp.1219-1225
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• 2018

In this study, a comprehensive laboratory experimental programme was conducted on expansive soil with a high swelling potential to study the influence of different additive materials on swelling pressure and index properties. Lime, sand, multifilament fiber and fibrillated fiber were used for stabilization of expansive soil. Lime, sand and fibers were respectively added to the expansive soil at 0-7%, 0-80%, 0-0.5%. On each mixture that was prepared by the proportions mentioned above, Atterberg limits, compaction, and swelling pressure tests were conducted. From the result of these experiments, the swelling pressure-time relation could be replaced by a rectangular hyperbola established to facilitate the prediction of ultimate percent swelling with a few initial data points. The best type of additive and its optimum ratio for engineering purposes could be estimated rapidly by this approach.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.349-354
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• 2003

The objective of this paper is to investigate the length change of high performance concrete using expansive additives to reduce autogenous shrinkage and drying shrinkage. The kinds and the contents of expansive additives are varied. The expansive additives are used made from Japan(CSA type;JEA), China(CSA type;CEA) and Korea(gypsum type; KEA), respectively. According to results, remarkable variations of the properties at fresh concrete are not found with dosage of expansive additives. For compressive strength, it decreases about 6-10% with expansive additives of 10%. Autogenous shrinkage decreases about 32%, and drying shrinkage does about 35%, respectively, with expansive additives of 5%, and about 68% and about 55%, with expansive additives of 10%. Accordingly, expansive additives demand requires 10% by cement weight in order to reduce shrinkage of high performance concrete more effectively in the sphere of this study, and JEA shows the best shrinkage reducing performance among the tested expansive additives.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.23-28
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• 1998

In this paper, the compensation of the shrinkage in high performance concrete by applying CSA expansive additives are discussed. According to toe experimental results, fluidity and strength decrease with the increase of the dosage of expansive additives. When 5% of expansive additive are mixed, not only high fluidity and strength, but also the compensation of drying-shrinkage can be achieved.