• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.9-10
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• 2017

In case of the concrete is poured into the HPC(Hollow Precast Concrete) column, the shrinkage condition of the HPC surface and the infilled concrete may be different, causing an interfacial space and deteriorating the integration performance. In this study, manufacturing HPC column mold and and the drying shrinkage properties with the charging concrete were examined. As a result, case of the shrinkage reducing agent showed the best drying shrinkage reduction effect. In the case of the expansive agent, the length change was lower than that of plain, but the difference from the shrinkage reducing agent was large, so it is considered that mixing condition of expansion mixing condition should be improved.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.209-210
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• 2021

This study aims to develop ultra-low-shrinkage high-quality concrete. Therefore, the concrete drying shrinkage characteristics according to the type and amount of the shrinkage reducing agent were reviewed. As a result, the performance of Hexylene Glycol(HG) and Polyol was superior to that of PolyEthylene Glycol(PEG), which is most widely used in Korea. In addition, the shrinkage reduction effect was improved as the amount of PEG was increased, but the disadvantage of the strength reduction when excessive use was confirmed.

• Journal of Industrial Technology
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• v.25 no.B
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• pp.73-80
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• 2005

Durability of concrete structures is seriously compromised by cracking at early-age concretes, particularly in high-strength or high-performance concrete structures. Since early-age cracking is influenced by various factors that affect the hydration process, early-age shrinkage and stress/strain development, the behavior at early-age is highly complex and no rational methodologies for its control have yet been established. Concrete structures often present volumetrical changes particularly due to thermal and moisture related shrinkages. Volumetric instability is detrimental to the performance and durability of concrete structures because structural elements are usually restrained. These restrained shrinkages develope tensile stresses which often results in cracking in combination with the low fracture resistance of concrete. Early-age defects in high-performance concrete due to thermal and autogenous deformation shorten the life cycle of concrete structures. Thus, it is necessary to examine the behavior of early-age concrete at the stages of design and construction. The purpose of this study was to propose a shrinkage models of VES-LMC (very-early strength latex-modified concrete) at early-age considering thermal deformation and autogenous shrinkage.

• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.245-252
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• 2017

Recently, structures such as large retailers, outlets and warehouses have been increasing in accordance with changes in consumption patterns. Since these structures include ultra-flat slab members, they are thoroughly managed to control slab cracking by the plastic and drying shrinkage. In order to control the cracking of the slab member, a chemical crack reduction method is used. In particular, the use of the shrinkage reducing agent has been examined. However, domestic research results are limited. In this study, the shrinkage properties of concrete using shrinkage reducing agent and the drying shrinkage properties according to the mixing factors were investigated. The performance of domestic shrinkage reducing agent was appeared similar to that of overseas high-grade shrinkage reducing agent. As the shrinkage reducing agent usage increased, the drying shrinkage reduction effect increased. At the age of 100 days, the dry shrinkage rate of specimen with the shrinkage reducing agent of 1.5%was shown about half that of the specimen without the shrinkage reducing agent. The shrinkage reducing agent was gound to have no specific performance change for the use of the admixture.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.621-628
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• 2005

Recently, it is noticed that autogenous shrinkage of high-performance concrete causes early crack in high performance concrete structures. The purpose of the present study is to derive a realistic equation to estimate the autogenous shrinkage of high performance concrete and to apply to structural analysis. For this purpose, several series of concrete specimens have been tested. When water-binder ratio is fixed to $30\%$, major test variables were the type and contents of mineral admixture. The autogenous shrinkage of HPC with fly ash slightly decreased than that of OPC concrete, but the use of blast furnace slag increased with the autogenous shrinkage. A prediction equation to estimate the autogenous shrinkage of HPC with mineral admixture was derived and proposed in this study. The proposed equation show reasonably good correlation with test data on autogenous shrinkage of HPC with mineral admixture. The finite element program developed in this study provides the useful tool for the flexural analysis including the autogenous shrinkage model. By this program, we know that the tensile stress considering the autogenous shrinkage of reinforced concrete structures increase $20\~27\%$ than that not considering.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.519-525
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• 2016

This paper reports on analyzing the free and restrained shrinkage characteristic of ternary grout used cementitious admixture. In this study, the cementitious admixture was used such as fly ash, ziricania silica fume by combination of expansive additive (a, b) and shrinkage reducing agent. And a number of basic performance tests were conducted to investigate bleeding, volume change, fluidity and compressive strength behavior. According to the results, within appropriate mixing ratio, even the fluidity is not influenced by expansive additive and shrinkage reducing agent, the resistant properties of bleeding, volume change, shrinkage and compressive strength are increased. Comparing with plain grout, the free shrinkage reduced by a minimum of 29% which specimens are added expansive additive and shrinkage reducing agent. The combination of expansive additive a and shrinkage reducing agent is the most effective for reduction of shrinkage. And increasing the mixing ratio of expansive additive and shrinkage reducing agent extended cracking time. Nevertheless, combined addition of expansive additive a 2.0% and shrinkage reducing agent 0.50% has best shrinkage reduction behavior and not appeared cracking. From the above, the mixing ratio of 2.0% of expansive additive a and 0.50% of shrinkage reducing agent is high performance ternary grout for PSC bridge.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.127-128
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• 2014

The aim of this research is selecting an economical aggregate type for ultra-high strength concrete with 80 to 120 MPa of compressive strength. As the tests, the effect of water-to-binder ratios and types of aggregate on autogenous shrinkage of ultra-high strength concrete were evaluated. as the results of a series of tests performed, the slump flow was satisfied the target range of 600 ± 100 mm, and the concrete mixture with RLA showed higher elastic modulus than the other cases. For the autogenous shrinkage preventing performance, in the case of water-to-binder ratio of 15, and 20 %, the mixture with BA showed slightly improved autogenous shrinkage reducing effect than the mixture with RLA while the mixture with RLA showed better performance at 25 % of water-to-binder ratio. Therefore, based on the tests results of slump flow, elastic modulus, and autogenous shrinkage, the RLA is considered as a better aggregate type for this purpose.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.545-548
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• 2004

This paper is to investigate the shrinkage properties of high performance concrete (HPC) with mixture adjustment by using mock-up specimens. HPC with mixture adjustment needed a higher dosage of SP agent due to fluidity reduction and a larger dosage of AE agent due to the reduction of air content. Setting time of HPC with mixture adjustment exhibited earlier than that of control HPC by as much as 6 hours. HPC with mixture adjustment gained more than 70MPa of compressive strength. Autogenous shrinkage of Control HPC was found to be $-340\times40^{-6}$ at 49days when the expansion value by thermal effect was excluded and HPC with mixture adjustment $-175\times10^{-6}$, which was the half of the value of control HPC. Drying shrinkage of center section of HPC with mixture adjustment showed similar tendency with autogenous shrinkage because of no internal moisture movement, while surface section had larger drying shrinkage. The specimen embedded with reinforcing bar had smaller deformation caused by confinement of reinforcing bar.

• Steel and Composite Structures
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• v.26 no.3
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• pp.303-314
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• 2018

Drying shrinkage in concrete caused by drying and the associated decrease in moisture content is one of the most important factors influencing the long-term deflection of steel-concrete composite slabs. The presence of profiled steel decking at the bottom of the composite slab causes non-uniform drying from top and bottom of the slab resulting non-uniform drying shrinkage. In this paper, a hydro-mechanical analysis method is proposed to simulate the development of non-uniform shrinkage through the depth of the composite slab. It also demonstrates how this proposed analysis method can be used in conjunction with previously presented structural analysis model to calculate the effects of non-uniform shrinkage on the long-term deflection of the slab. The method uses concrete moisture diffusion model to simulate the non-uniform drying of composite slab. Then mechanical models are used to calculate resulting shrinkage strain from non-uniform drying and its effect on the long-term behaviour of the composite slabs. The performance of the proposed analysis method is validated against experimental data.

• International Journal of Highway Engineering
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• v.20 no.2
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• pp.19-25
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• 2018

PURPOSES : This purpose of this study is to analyze the effect to autogenous shrinkage of the top-layer material of a two-lift concrete pavement mixing both silica fume and polymer powder. METHODS : The bottom-layer of a two-lift concrete pavement was paved with original portland cement (OPC) with a 20~23 cm thickness. Additionally, the top-layer which is directly exposed to the environment and vehicles was paved with a high-performance concrete (HPC) with a 7~10 cm thickness. These types of pavements can achieve a long service life by reducing joint damage and increasing the abrasion and scaling resistance. In order to integrate the different bottom and top layer materials, autogenous shrinkage tests were performed in this study according to the mixing ratio of silica fume and polymer powder, which are the admixture of the top-layer material. RESULTS : Autogenous shrinkage decreased when polymer powder was used in the mix. Contrary to this, autogenous shrinkage tended to rise with increasing silica fume content. However, the effects were not significant when small amounts of polymer powder were used (3% and 11%). CONCLUSIONS : The durability and compressive strength increase when silica fume is used in the mix. The flexural strength considerably increases and autogenous shrinkage of concrete decreases when polymer powder is used in the mix. As seen from above, the proper use of these materials improves not only durability, but also autogenous shrinkage, leading to better shrinkage crack control in the concrete.