• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.151-156
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• 2002

Drying shrinkage cracking which may be caused by the relatively large specific surface is a matter of grave concern for latex modified concrete(LMC) overlay and rapid-setting cement latex modified concrete(RSLMC) overlay. LMC and RSLMC were studied for field applications very actively in terms of strength and durability in Korea. However, there were no considerations in drying shrinkage. Therefore, the purpose of this study was to investigate the drying shrinkage properties of LMC and RSLMC with the main experimental variables such as cement types(ordinary portland cement, rapid setting cement), latex contents(0, 5, 10, 15, 20%), W-C ratios, and curing days at a controlled environment of 60% of relative humidity and 2$0^{\circ}C$ of temperature. The drying shrinkage for specimens was measured with a digital dial gauge of Demec. The test results showed that the drying shrinkage of LMC and RSLMC were considerably lower than that of OPC and RSC, respectively. This might be attributed to the interlocking of hydrated cement and aggregates by a film of latex particles, water retention due to hydrophobic, and colloidal properties of the latexes resulting in reduced water evaporation.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.277-280
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• 2003

Material, mix proportion, curing condition, temperature, humidity and wind velocity have an influence on drying shrinkage of concrete. In this paper, to evaluate the effect of curing condition at early age on the drying shrinkage of concrete was investigated varying curing age for different binder. The principal conclusions from this research were as follows: 1) In case of 14 days of water curing, the drying shrinkage of concrete is smaller than 7 days of water curing, independence of type of binder. 2) In case of 4 days of water curing, the ratio of increase of drying shrinkage of concrete using fly-ash and slag powder is more remarkable than using portland cement alone, comparing the drying shrinkage of 7 days of water curing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.166-167
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• 2015

The purpose of this study is to examine the effect on drying shrinkage of self-healing epoxy-modified mortars(EPMMs) using expansive admixtures. The EPMMs are prepared with polymer-binder ratios of 0 and 10%, and tested for drying shrinkage and pore structure analysis. As a result, regardless of the expansion and swelling agent content, the drying shrinkage of the EPMMs is remarkably decreased than that of unmodified mortars. Also, the pore size distribution of the EPMMs is moved to smaller size in comparison with unmodified mortars. In this study, the EPMM with expansive agent 7.5% and swelling agent 2.5% is recommended as a optimal mix proportion for reduction of drying shrinkage.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.297-303
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• 2016

Shrinkage Reducing Agent(SRA) was developed in order to control drying shrinkage cracks in concrete, and the use of SRA is increasing since it can control drying shrinkage cracks and improve the quality of concrete structures. Although there are many types of prediction equations of drying shrinkage strain, there is no prediction method which can consider the effect of SRA up to the present. Therefore, it is impossible to predict the tensile stress generated by drying shrinkage of SRA concrete, and to investigate the quantitative serviceability limit state of SRA concrete. In this study, the drying shrinkage of SRA concrete was investigated by experiment and analysis in order to suggest the predictability of drying shrinkage of SRA concrete. As a result, AIJ model, ACI model, GL2000 model showed there was a correlation between the predicted values and the experimental values within the error range of ${\pm}10%$. However, CEB-FIP model and B3 model underestimated the experimental values.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.533-536
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• 2005

Drying shrinkage and strength of the redispersible SBR and PAE powder-modified mortars were experimentally investigated. Results of the study that the drying shrinkage rapidly increased until 7 days of age and it was then saturated to the value of about $1\~2\times10^{4}$ after 14 days. It turned out that the polymer-cement ratio exerted more influence on the drying shrinkage than the content of powder shrinkage-reducing agent did. Flexural (compressive) strength of the mortar increased (decreased) as the polymer-cement ratio increased and it was 7$\~$11 (23$\~$39) MPa at 7 days of age. The average (maximum) increasing (decreasing) rate turned out to be about 10 (30) $\%$. As in the drying shrinkage case, the polymer-cement ratio exerted more influence on both flexural and compressive strengths than the content of powder shrinkage agent did.

• Steel and Composite Structures
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• v.47 no.4
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• pp.539-550
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• 2023

Owing to the obstruction of section steel on the moisture diffusion in concrete, the existing shrinkage prediction models overestimate the time-dependent deformation of steel reinforced concrete (SRC) columns, particularly for the SRC columns with enclosed section steels. To solve this issue, this study deals with analytical and experimental studies on the drying shrinkage for this type of column. First, an effective method for predicting the drying shrinkage of concrete based on finite element model is introduced and two crucial parameters for simulation of humidity field are determined. Then, the drying shrinkage of SRC columns with enclosed section steels is investigated and two modified parameters, which depend on the ambient relative humidity and the ratio of section steel size to column size, are introduced to the B3 model. Finally, an experiment on the shrinkage deformation of SRC columns with enclosed section steels is conducted. Comparing the predicted results with the experimental ones, it demonstrates that the modified B3 model is quite reasonable.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.193-200
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• 2002

Drying shrinkage cracking which may be caused by the relatively large specific surface IS a matter of grave concern for latex modified concrete(LMC) overlay and rapid-setting cement latex modified concrete(RSLMC) overlay. LMC and RSLMC were studied for field applications very actively in terms of strength and durability in Korea. However, there were no considerations in drying shrinkage. Therefore, the purpose of this dissertation was to study the drying shrinkage properties of LMC and RSLMC with the main experimental variables such as cement types(ordinary portland cement, rapid setting cement), water-cement ratios and curing days at a same controlled environment of 60% of relative humidity and $20^{\circ}C$ of temperature The drying shrinkage for specimens was measured with a digital dial gauge of Demec. The test results showed that the drying shrinkage of LMC and RSLMC were considerably lower with low water-cement ratio, respectively This might be attributed to the interlocking of hydrated cement and aggregates by a film of latex particles, water retention due to hydrophobic, and colloidal properties of the latexes resulting in reduced water evaporation.

• 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 Korea Concrete Institute Conference
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• 2004.05a
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• pp.676-679
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• 2004

In this study, we considered the characteristic of drying shrinkage from age of high strength concrete with garnet minute powder to be industry by-product. The factors of experiment are unit water content$(160kg/m^3)$, water-binder ratio(30, $35\%$), fine aggregate ratio(40, 42, $44\%$), admixture replacement ratio(0, 10, $20\%$), admixture type(garnet minute powder, fly ash, blast-furnace slag). We make a comparative study of shrinkage about concrete with a passage of age(1, 3, 7, 14, 28, 56, 91 days). As a result of experiment, we reach a conclusion as follow. In the same mix condition, as unit water content and fine aggregate ratio go up, the drying shrinkage ratio increase. In the drying shrinkage ratio according to admixture replacement ratio, it goes up when admixture replacement Ratio increase in case of fly ash and blast-furnace slag. But, drying shrinkage ratio decrease when admixture replacement ratio increase in case of garnet minute powder.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.407-408
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• 2009

Drying shrinkage have influence on the durability of concrete structure. Various models have been suggested to predict the drying shrinkage, experimentally. In this study, the drying shrinkage with Concrete strength and Curing condition was measured, and compared with representative model code. As a result, drying shrinkage was reduced as W/C ratio decrease, and total shrinkage greatly reduced in 4 week wet curing case. The test results agreed with EC2 model better than the other.