• Journal of the Korean Society of Industry Convergence
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• v.16 no.1
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• pp.1-8
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• 2013

In case that W/B is 20%, 30%, 40% respectively, the effects of additive and shrinkage reducing agent on the autogenous shrinkage for high strengthen concrete through the substitution of FA and SF analysis were obtained as following conclusions. When the ratio of FA increased, the compressive strength of high strengthen concrete is decreased in the early times. As the ratio of SF increase, the compressive strength also increased. Comparing with PC(Portland Cement) for 7 days curing, the strength is 13.8% of FA10 + SR0.5 and 19.2% of FA15 + SR0.5 decreased when W/B is 20%, and 6.1% of SF7.5 + SR0.5, 4.8% of SF15 + SR0.5, the strength are increased. In case that W/B is 30%, 13.1% of FA10 + SR0.5 19.1% of FA15 + SR0.5 the strength is decreased and 4.1% of SF 7.5 + SR0.5, 7.2% of SF15 + SR0.5 the strength are increased. In case of W/B 40%, 4.3% of FA10 + SR0.5, and 8.7% of FA15 + SR0.5, the strength is decreased and 3.3% of SF7.5 + SR0.5, 6.3% SF15 + SR0.5 the strength is increased. When the ratio of SR is 0.5%, autogenous shrinkage strain of OPC concrete appeared $-417{\times}10-6$ in 56days curing, the shrinkage strain is decreased 23.7%. The reducing effects of autogenous shrinkage when the mineral and shrinkage agent are used are the same as ones when only shrinkage agent used.

• International Journal of Highway Engineering
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• v.19 no.1
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• pp.45-52
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• 2017

PURPOSES : The main purpose of this study is to develop a high elastic modulus and low-shrinkage roller-compacted concrete base (RCCB) in order to prevent fatigue cracking and reflective cracking in the asphalt surface layer of composite pavement. Using a rigid base material with low shrinkage can be a solution to this problem. Moreover, a strong rigid base with high elastic modulus is able to shift the location of critical tensile strain from the bottom of the asphalt layer to the bottom of the rigid base layer, which can prevent fatigue cracking in the asphalt layer. METHODS : Sensitivity analysis of composite pavement via numerical methods is implemented to determine an appropriate range of elastic modulus of the rigid base that would eliminate fatigue cracking. Various asphalt thicknesses and elastic moduli of the rigid base are used in the analysis to study their respective influences on fatigue cracking. Low-shrinkage RCC mixture, as determined via laboratory testing with various amounts of a CSA expansion agent (0%, 7%, and 10%), is found to achieve an appropriate low-shrinkage level. Shrinkage of RCC is measured according to KS F 2424. RESULTS : This study shows that composite pavements comprising asphalt thicknesses of (h1) 2 in. with E2 > 19 GPa, 4 in. with E2 > 15 GPa, and 6 in. with E2 > 11 GPa are able to eliminate tensile strain in the asphalt layer, which is the cause of fatigue cracking in this layer. Shrinkage test results demonstrate that a 10% CSA RCC mixture can reduce shrinkage by 84% and 93% as compared to conventional RCC and PCC, respectively. CONCLUSIONS : According to the results of numerical analyses using various design inputs, composite pavements are shown to be able to eliminate fatigue cracking in composite pavement. Additionally, an RCC mixture with 10% CSA admixture is able to reduce or eliminate reflective cracking in asphalt surfaces as a result of the significant shrinkage reduction in the RCC base. Thus, this low-shrinkage base material can be used as an alternative solution to distresses in composite pavement.

• Composites Research
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• v.26 no.3
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• pp.182-188
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• 2013

The purpose of this study was to measure the volumetric polymerization shrinkage kinetics and stress of a silorane-based dental restorative composite and compare it with those of conventional methacrylate-based dental composites. Two methacrylate-based composites (Z250, Z350 flowable) and one silorane-based composite (P90) were investigated. The volumetric polymerization shrinkage of the composites during light curing was measured using a laboratory-made volume shrinkage measurement instrument based on the Archimedes' principle, and the polymerization stress was also determined with the strain gage method. The shrinkage of silorane-based composites (P90) was the lowest, and that of Z350 flowable was the highest. Peak polymerization shrinkage rate was the lowest in P90 and the highest in Z350 flowable. The time to reach peak shrinkage rate of P90 was longer than those of the methacrylate-based composites. The polymerization shrinkage stress of P90 was lower than those of the methacrylate-based composites.

• 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.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.90-96
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• 2009

Injection molding process is one of the most important methods to produce plastic parts with high efficiency and low cost. Today, injection molded parts have been increased dramatically the demand for high strength and quality applications. This report investigates that the optimum injection molding condition for minimum of shrinkage. Molding shrinkage is occurred by several reasons such as thermal shrinkage, a hardening process and compressibility. This report concentrate on shrinkage by a hardening process. As Change a holding pressure and holding time, checked deflections of X, Y, Z directions by shrinkage based on same condition. In conclusion, it was found that holding pressure is stronger and holding time is longer, the deflection by shrinkage is smaller because injection molding needs enough time for cooling and high density. The FEM Simulation CAE tool. Moldflow, is used for the analysis of injection molding process.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.362-367
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• 1998

The purpose of this study is to examine the influences of polystyrene content and St/UP on the setting shrinkage and strengths of polymer mortar with waste expanded polystyrene resin as a shrinkage-reducing agent, and to recommend the optimum binder formulations for product of low-shrinkage polymer mortar. In this paper, polymer mortar is prepared with waste expanded polystyrene content and St/UP, and tested for setting shrinkage, flexural and compressive strengths. From the test results, irrespective of increasing of waste expanded polystyrene resin, the strengths reduction of polymer mortar with waste expanded polystyrene(EPS) resin is not recognized. And the setting shrinkage is reduced with EPS resin content. The waste expanded polystyrene resin as a shrinkage-reducing agent can be used in the same manner as commercial polystyrene resin. In this study, we can obtain the optimum mix proportions of polymer mortar using EPS resin.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.257-260
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• 2003

This study discusses the properties of shrinkage of high performance concrete with W/B and water content. According to results, drying shrinkage decrease of water content due to the influence of autogenous shrinkage. And drying shrinkage is reduced with a decrease of water content. As W/B decreases, autogenous shrinkage increases because shrinkage by hydration is generated greatly due to an increase of binder content. Also, as water content decreases, it is reduced because of a decrease of cement paste by cement content.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.647-650
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• 2005

This paper is to investigate the shrinkage properties of ultra high strength concrete(UHSC) incorporating $5\%$ of expansive additives(EA) along with $1\%$ of shrinkage reducing agent(SRA). UHSC subjected to steam curing and incorporated with steel fiber exhibited higher compressive strength than control UHSC by as much as50MPa at 7days, while at 28days, noticeable change in compressive strength was not observed between UHSC mixtures. Control UHSC subjected to steam curing had a $922{\times}10^6$ of autogenous shrinkage strain value, which was 6.7 times of drying shrinkage strain value at 42 days. The combination of EA and SRA resulted in a decrease in autogenous shrinkage by as much as half of control mixture. Steam curing contributed to the reduction of autogenous shrinkage by as much as $11\%$ compared with that of standard curing.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.3-9
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• 2007

Fiber-reinforced self-compacting concrete (FRSCC) is a new type of concrete mix that can mitigate two opposing weaknesses: poor workability in fiber-reinforced concrete and cracking resistance in plain SCC concrete. This study focused on early-age cracking of FRSCC due to restrained drying shrinkage, one of the most common causes of cracking. In order to investigate the effect of fiber on shrinkage cracking of FRSCC, ring shrinkage tests were performed for polypropylene and steel fiber-reinforced SCC. In addition, finite element analyses for those specimens were carried out considering drying shrinkage based on moisture diffusion, creep, cracking resistance of concrete, and the effect of fiber. The analysis results were verified via a comparison between the measured and calculated crack width. From the test and analysis results, the effectiveness of fiber with respect to reducing cracking was confirmed and some salient features on the shrinkage cracking of FRSCC were obtained.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.83-85
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• 2010

This study, by analyzing autogenous shrinkage of high-strength mortar according to changes of curing temperature, examined whether or not predictive autogenous shrinkage by an accumulated temperature method can be calculated. As a result, it could be known that dependency of autogenous shrinkage on temperature can be examined, but the autogenous shrinkage amount according to accumulated temperature was similar before and after the early $100 ^{\circ}D{\cdot}D$ and, after that, the difference in shrinkage amount by curing temperature was large.