• 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.

• Journal of the Korea Institute of Building Construction
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• v.22 no.1
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• pp.45-55
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• 2022

Ultra-low shrinkage concrete is very effective for securing the quality and appearance of a concrete structure because it can control the drying shrinkage cracks of the concrete structure to within a certain limit. In this study, with the purpose of commercializing ultra-low shrinkage concrete, the optimal amount of expansive agent and shrinkage reducing agent was determined through a lab test, and a concrete wall mock-up test was conducted to examine the shrinkage properties and crack control effects of ultra-low shrinkage concrete. As a result, it was confirmed that there was little drying shrinkage deformation in the wall specimen, and furthermore that no cracks were generated.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.269-272
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• 2004

After concrete casts, temperature decent and shrinkage bring volume changes of concrete pavement. Microcracking and cracking in concrete pavement are caused by these volume changes. As a result, durability of concrete pavement is deteriorated. Recently, Very-Early Strength Latex Modified concrete(below:VESLMC) from the beginning of High-Way is used as urgent repair material for bridge deck. The advantage of VESLMC is that compressive and flexural strength at 3 hours age are 4.5MPa and 21MPa respectively. It allows the traffic to open in 3 hours. But, this material has the problem which is early-age shrinkage cracking caused by water self-dissipation with rapid hydration reaction and water evaporation with body dry. Unfortunately, until now, the research about early-age shrinkage of VESLMC leaves something to be desired. Therefore, the purpose of this study is to present the early-age shrinkage of VESLMC respect to latex contents and shrinkage ratio to maximum length change that can help field engineers' skill. Latex contents of 0, 5, 10, 15, $20\%$ in standard of same workability in VESLMC are selected by experimental variables. After initial set, shrinkage value was measured with 10mm LVDT for 3 days. The results of maximum shrinkage ratio were 0.019, 0.017, 0.023, $0.027\%$ respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.321-326
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• 2000

Many different polymer based concrete materials are known today, but the large setting or hardening shrinkage of polymer concrete is a problem to overcome in their practical applications. The setting shrinkage reaches about five to ren times he drying shrinkage ordinary cement concrete, i.e, 50 to $60\times10^{-4}$. This paper deals with a reduction in the hardening shrinkage of unsaturated polyester resin concrete which is treated with respect to shrinkage-reducing agent content, S/a ratio and catalyst content, and tested for length change during hardening, and flexural and compressive strength. It is show that the change of shrinkage-reducing agent content and S/a ratio affected the length change of the unsaturated polyester resin concrete during hardening.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.61-64
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• 2006

Comparing with traditional high performance concrete, ultra high performance concrete (UHPC) has the property of high-tenacity. However, drying shrinkage and autogenous shrinkage can be arisen as the major defect to UHPC. In this study, therefore, it was tested to reduce drying shrinkage and autogeneous shrinkage by adding expanding admixture (EA) and shrinkage reducing agent (SRA). As a result, for a case drying shrinkage, the shrinkage was decreased by 94% when EA was exchanged, and it was decreased by 64% when SRA was added. For the case of autogenous shrinkage, the mortar was expanded at early age and the shrinkage was decreased by 87% when EA was exchanged, and the shrinkage was decreased by 70% when SRA was added.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.592-595
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• 2004

This Study discusses the properties of drying shrinkage of concrete slab with W/B, water content, fiber and anti-shrinkage agent. According to results, drying shrinkage is reduced with decrease of water content and W/B. Also, compared with plain concrete, drying shrinkage is reduced by using of fiber, anti-shrinkage agent and adding ratio of anti - shrinkage agent. Therefore, in the range of workability if water content and W/B are reduced and using of fiber and anti-shrinkage agent are performed properly, crack by drying shrinkage can be prevented effectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.485-488
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• 2006

The shrinkage properties of the high strength concrete using the cement of Type I, Type III and Type IV was examined, and the following results were obtained. (1) Consideration of the autogenous shrinkage when evaluating appropriately the shrinkage properties of the high strength concrete is indispensable. (2) The autogenous shrinkage prediction expression of JSCE can estimate the properties of autogenous shrinkage of the cement made from korea with in general sufficient accuracy. (3) It is necessary to advance examination which used Korean aggregate about dry shrinkage from now on, and to attain highly accuracy of the autogenous shrinkage prediction expression.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.315-320
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• 1998

The experimental set-up and one-dimensional analytical model have been developed to investigate the tensile behavior of reinforced concrete member due to restrained drying shrinkage. The experimental results have been compared with the analytical prediction of the maximum residual stress of steel and concrete due to restrained shrinkage. The tensile residual stress concrete by one-dimensional bilinear model shows 0.19 and 0.63 of tensile strength for 0.83% and 3.29 of steel ratio. The residual tensile stress of concrete increases as the steel ratio increases. The effect of steel fiber has not influenced the residual stress due to restrained shrinkage of concrete.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.249-256
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• 2002

High performance concrete is prone to large autogenous shrinkage due to its low water to binder ratio (W/B). The autogenous shrinkage of concrete is caused by self-desiccation as a result of water consumption by the hydration of cement. In this study, the autogenous shrinkage of high performance concrete with and without fly ash was Investigated. The properties of fresh concrete, slump loss, air content, and flowability as well as the mechanical properties, compressive strength and modulus of elasticity, were also measured. Test results was shown that the autogenous shrinkage of concrete increased as the W/B decreased. For the same W/B, the autogenous shrinkage of high strength concrete with fly ash was considerably reduced although the development of its compressive strength was delayed at early ages. Furthermore, the autogenous shrinkage and compressive strength of high strength concrete were more rapidly developed than those of normal strength concrete. It was concluded that fly ash could improve the quality of high strength concrete with respect to the workability and autogenous shrinkage.

• Computers and Concrete
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• v.23 no.5
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• pp.329-334
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• 2019

Traffic flow capacity of some old road bridges is insufficient due to limited deck width. In such cases bridge deck widening is a common solution. For multi-girder reinforced concrete (RC) bridges it is possible to add steel-concrete composite girders as the new outermost girders. The deck widening may be combined with bridge strengthening thanks to thickening of the existing deck slab. Joint action of the existing and the added parts of such bridge span must be ensured. It refers especially to the horizontal plane at the interface of the existing slab and the added concrete layer as well as to the vertical planes at the external surfaces of the initially outermost girders where the added girders are connected to the existing bridge span. Since the distribution of the added concrete is non-uniform in the span cross-section the structure is particularly sensitive to the added concrete shrinkage. The shrinkage induces shear forces in the aforementioned planes. Widening of a 12 m long RC multi-girder bridge span is numerically analysed to assess the influence of the added concrete shrinkage. The analysis results show that: a) in the vertical plane of the connection of the added and the existing deck slab the longitudinal shear due to the shrinkage of the added concrete is comparable with the effect of live load, b) it is necessary to provide appropriate longitudinal reinforcement in the deck slab over the added girders due to tension induced by the shrinkage of the added concrete.