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Hwaseong, South Korea

Kim Y.-Y.,Chungnam National University | Lee B.-J.,JNTINC Co. | Kwon S.-J.,Hannam University
Advances in Materials Science and Engineering | Year: 2014

Diffusion coefficient from chloride migration test is currently used; however this cannot provide a conventional solution like total chloride contents since it depicts only ion migration velocity in electrical field. This paper proposes a simple analysis technique for chloride behavior using apparent diffusion coefficient from neural network algorithm with time-dependent diffusion phenomena. For this work, thirty mix proportions of high performance concrete are prepared and their diffusion coefficients are obtained after long term-NaCl submerged test. Considering time-dependent diffusion coefficient based on Fick's 2nd Law and NNA (neural network algorithm), analysis technique for chloride penetration is proposed. The applicability of the proposed technique is verified through the results from accelerated test, long term submerged test, and field investigation results. © 2014 Yun-Yong Kim et al. Source


Lee B.J.,JNTINC Co. | Prabhu G.G.,KPR Institute of Engineering and Technology | Lee B.C.,Korea Conformity Laboratories | Kim Y.Y.,Chungnam National University
Waste Management and Research | Year: 2016

This article presents the test results of an investigation carried out on the reuse of coal bottom ash aggregate as a substitute material for coarse aggregate in porous concrete production for marine ranch applications. The experimental parameters were the rate of bottom ash aggregate substitution (30%, 50% and 100%) and the target void ratio (15%, 20% and 25%). The cement-coated granular fertiliser was substituted into a bottom ash aggregate concrete mixture to improve marine ranch applications. The results of leaching tests revealed that the bottom ash aggregate has only a negligible amount of the ten deleterious substances specified in the Ministry of Environment - Enforcement Regulation of the Waste Management Act of Republic Korea. The large amount of bubbles/air gaps in the bottom ash aggregate increased the voids of the concrete mixtures in all target void ratios, and decreased the compressive strength of the porous concrete mixture; however, the mixture substituted with 30% and 10% of bottom ash aggregate and granular fertiliser, respectively, showed an equal strength to the control mixture. The sea water resistibility of the bottom ash aggregate substituted mixture was relatively equal to that of the control mixture, and also showed a great deal of improvement in the degree of marine organism adhesion compared with the control mixture. No fatality of fish was observed in the fish toxicity test, which suggested that bottom ash aggregate was a harmless material and that the combination of bottom ash aggregate and granular fertiliser with substitution rates of 30% and 10%, respectively, can be effectively used in porous concrete production for marine ranch application. © The Author(s) 2015. Source


Lee B.J.,JNTINC Co. | Kim J.S.,Korea Institute of Construction Technology | Jang Y.I.,Chungnam National University
Key Engineering Materials | Year: 2016

In this study, the optimal mixing conditions for recycled cold asphalt, which recycled waste asphalt and used cementless binders, was assessed through verification of the performance. The cementless binder mixing ratio of 6% desulfurization gypsum substitution rate for blast furnace slag was found to have the most outstanding properties. For the Marshall stability, 4% filler mixing brought about a 1.92 times strength increase effect compared to OPC. The flow value testing showed that an increase in the use of asphalt emulsion resulted in an increased flow value while it decreased with the increase in filler substitution rate. The optimal mixing condition that satisfied mechanical performance and durability among the test conditions assessed in this study was found to be 4% filler mixed. © (2016) Trans Tech Publications, Switzerland. Source


Lee B.J.,JNTINC Co. | Kee S.-H.,Dong - A University | Oh T.,Incheon National University | Kim Y.-Y.,Chungnam National University
Advances in Materials Science and Engineering | Year: 2015

The primary objective of this study is to investigate the effects of cylinder size (150 by 300 mm and 100 by 200 mm) on empirical equations that relate static elastic moduli and compressive strength and static and dynamic elastic moduli of concrete. For the purposes, two sets of one hundred and twenty concrete cylinders, 150 by 300 mm and 100 by 200 mm, were prepared from three different mixtures with target compressive strengths of 30, 35, and 40 MPa. Static and dynamic tests were performed at 4, 7, 14, and 28 days to evaluate compressive strength and static and dynamic moduli of cylinders. The effects of the two different cylinder sizes were investigated through experiments in this study and database collected from the literature. For normal strength concrete (≤40 MPa), the two different cylinder sizes do not result in significant differences in test results including experimental variability, compressive strength, and static and dynamic elastic moduli. However, it was observed that the size effect became substantial in high strength concrete greater than 40 MPa. Therefore, special care is still needed to compare the static and dynamic properties of high strength concrete from the two different cylinder sizes. © 2015 Byung Jae Lee et al. Source


Lee B.-J.,JNTINC Co. | Lee J.,Korea Conformity Laboratories | Jang Y.-I.,Chungnam National University
Contemporary Engineering Sciences | Year: 2015

This study examined the physical and mechanical properties as well as the marine organism adhesion characteristics of the porous concrete that used recycled aggregate and specially treated granular fertilizer in order to present fundamental data for the effective use of recycled aggregates that were generated as byproducts of construction and for field application of the porous concrete used for the restoration of the marine ecosystem. The experimental results showed that the difference between the target void ratio and actually measured void ratio was approximately 2.0% and that the compressive strength tended to decrease rapidly when the target void ratio and recycled aggregate mixing ratio exceeded 20% and 50%, respectively. In addition, the adhesion ability of marine organisms to porous concrete was superior when the target void ratio was greater than 20% and the influence on the adhesion ability according to the mixing of recycled aggregates was insignificant. Moreover, it was observed that the adhesion ability of marine organisms improved when the specially treated granular fertilizer was mixed. Therefore, the appropriate target void ratio of 20% and the recycled aggregate mixing ratio of 50% are thought to be effective when considering the strength of the porous concrete for marine ecosystem restoration and the adhesion characteristics of marine organisms. © 2015 Buung-Jae Lee et al. Source

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