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Yeon K.-S.,Kangwon National University | Choi Y.-S.,Korea Conformity Laboratories | Kim K.-K.,Kangwon National University | Yeon J.H.,Gachon University
Construction and Building Materials | Year: 2017

Laboratory and statistical evaluations were performed to examine the flexural fatigue performance of unsaturated polyester-methyl methacrylate (UP-MMA) polymer concrete. Target stress levels were 0.9, 0.8, 0.7, and 0.6 with a fixed stress ratio of 0.1. A 5 Hz sinusoidal load with a constant-amplitude frequency was applied to a prismatic specimen (100 × 100 × 400 mm) using a 250-kN universal testing machine (UTM). MMA contents considered were 0, 10, 20, and 30 wt.%. In addition, the two-parameter Weibull distribution was employed to analyze the fatigue life probability distributions of UP-MMA polymer concrete. Three different analysis methods—the graphical method, method of moment, and method of maximum likelihood estimation—were applied to estimate the distribution parameters of the two-parameter Weibull distribution. The results have shown that the two-parameter Weibull distribution describes the fatigue life probability distributions of UP-MMA polymer concrete with quite high statistical correlation coefficients. Also, the goodness-of-the-fit of the fatigue life data obtained was verified by means of the Kolmogorov-Smirnov test, which were all accepted at a 5% significance level. Finally, a single-log fatigue equation was derived to predict the fatigue life of UP-MMA polymer concrete. © 2017 Elsevier Ltd

Kim J.S.,Korea Conformity Laboratories | Song K.S.,Korea Conformity Laboratories | Joo H.J.,Korea Conformity Laboratories | Lee J.H.,Hoseo University | Yu I.J.,Hoseo University
Journal of Toxicology and Environmental Health - Part A: Current Issues | Year: 2010

Carbon nanotubes (CNT) possess beneficial physicochemical and mechanical properties; however, despite these advantages there are concerns regarding the adverse effects of CNT on lung and development of diseases, such as lung cancer and mesothelioma. According to fiber characteristics of length and diameter (aspect ratio), fibers with high aspect ratio (10-15 nm diameter and containing two different length distributions of 545 ± 230 and 10451 ± 8422 nm length) are more toxic to lung than low-aspect-ratio fibers (10-15 nm diameter and length of 192 nm). It was thus of interest to investigate the effects of multiwall carbon nanotubes (MWCNT) on the viability of normal human embryonic lung cells (WI-38) using trypan blue dye exclusion, the tetrazolium salt WST-1 (4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate) assay, and lactate dehydrogenase (LDH) activity assay. MWCNT produced cell growth inhibition and death at 12.5-200 μg/ml after 24-72 h of incubation. In addition, high-aspect-ratio MWCNT were found to produce higher incidence of cytotoxicity than low-aspect-ratio fibers at 50-200 μg/ml concentration. In the presence of less than 10% trace element content such as iron in MWCNT, the trace element exerted no marked effect on cellular viability. Data indicate that MWCNT inhibited cell proliferation and triggered cell death, and it would appear that the MWCNT fiber characteristics rather than impurities play a predominant role in the observed the cytotoxicity attributed to MWCNT. Copyright © Taylor & Francis Group, LLC.

Song M.Y.,Korea Conformity Laboratories | Song M.Y.,Konkuk University | Ku S.K.,Daegu Haany University | Han J.S.,Konkuk University
Food and Chemical Toxicology | Year: 2012

Fucoidan extracts from brown seaweed have anticoagulant, antithrombotic, and antiviral activities. Low molecular weight fucoidan (LMF) obtained by acid hydrolysis of high molecular weight fucoidan showed more favorable bioactivity. Despite extensive work on LMF bioactivities, detailed studies on the genotoxicity of LMF have not been conducted. As part of a safety evaluation, the potential genotoxicity of LMF was evaluated using a standard battery of tests (bacterial reverse mutation assay, chromosomal aberrations assay, and mouse micronucleus assay). The LMF was determined not to be genotoxic under the conditions of the reverse mutation assay, chromosomal aberrations assay, or mouse micronucleus assay. In a reverse mutation assay using four Salmonella typhimurium strains and Escherichia coli, LMF did not increase the number of revertant colonies in any tester strain regardless of metabolic activation by S9 mix, and did not cause chromosomal aberration in short tests with the S9 mix or in the continuous (24. h) test. A bone marrow micronucleus test in ICR mice dosed by oral gavage at doses up to 2000. mg/kg body weight/day showed no significant or dose-dependent increases in the frequency of micronucleated polychromatic erythrocytes. Use of LMF is presently expected to be safe, as anticipated intake is small compared to doses administered in the genotoxicity assays and may prove to be a useful bioactive agent after further toxicity research. © 2011 Elsevier Ltd.

Jung S.H.,Korea Conformity Laboratories | Kwon S.-J.,Hannam University
Central European Journal of Engineering | Year: 2013

Among the wastes from coal combustion product, only fly ash is widely used for mineral mixture in concrete for its various advantages. However the other wastes including bottom ash, so called PA (pond ash) are limitedly reused for reclamation. In this paper, the engineering properties of domestic pond ash which has been used for reclamation are experimentally studied. For this, two reclamation sites (DH and TA) in South Korea are selected, and two domestic PAs are obtained. Cement mortar with two different w/c (water to cement) ratios and 3 different replacement ratios (0%, 30%, and 60%) of sand are prepared for the tests. For workability and physical properties of PA cement mortar, several tests like flow, setting time, and compressive strength are evaluated. Several durability tests including porosity measuring, freezing and thawing, chloride migration, and accelerated carbonation are also performed. Through the tests, PA (especially from DH area) in surface saturated condition is evaluated to have internal curing action which leads to reasonable strength development and durability performances. The results show a potential applicability of PA to concrete aggregate, which can reduce consuming natural resources and lead to active reutilization of coal product waste. © Versita sp. z o.o.

Kim J.S.,Korea Conformity Laboratories | Song K.S.,Korea Conformity Laboratories | Lee J.H.,Hoseo University | Yu I.J.,Hoseo University
Archives of Toxicology | Year: 2011

Dispersion is one of the key obstacles to evaluating the in vitro and in vivo toxicity of carbon nanotubes (CNTs), as the aggregation or agglomeration of CNTs in culture media or vehicles complicates the interpretation of the toxicity test results. Thus, to test the dispersion of CNTs in biocompatible solutions, 5 known biocompatible dispersants were selected that are widely used for nanomaterial toxicity evaluation studies. Single-wall nanotubes (SWCNTs) and multi-wall nanotubes (MWCNTs) were both dispersed in these dispersants and their macrodispersion evaluated using a light absorbance method. The dispersion stability of the dispersed SWCNTs and MWCNTs was also evaluated for 16 weeks, plus the dispersants were tested for their innate toxicity using trypan blue dye exclusion, lactate dehydrogenase (LDH) leakage, and neutral red assays. All the dispersants were found to be biocompatible in the cytotoxicity tests when compared with a positive control of 2% Triton X-100. In the dispersion tests, 0.02, 0.1, and 0.5% MWCNTs and SWCNTs were diluted in the respective dispersants. Distilled water and dimethylsulfoxide (DMSO) both showed a poor macrodispersion of only 1-13% for the various CNT concentrations. In 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), the 0.02 and 0.1% MWCNTs showed a macrodispersion of 11 and 74%, respectively, while the 0.02 and 0.1% SWCNTs showed a macrodispersion of 15 and 16%, respectively. In 0.5% bovine serum albumin (BSA), the 0.02, 0.1, and 0.5% MWCNTs showed a very good macrodispersion of 32, 53, and 70%, respectively, yet the 0.02% SWCNTs only showed a macrodispersion of 17%. In 1% Tween 80, the 0.02-0.5% SWNCTs exhibited a good macrodispersion of 27-81%, whereas the 0.02-05% MWCNTs only showed a macrodispersion of 13-23%. The dispersion stability of the CNTs during 16 weeks was in the following descending order of BSA, Tween 80, DPPC, and DMSO for the MWCNTs and BSA, DPPC, Tween 80, and DMSO for the SWNCTs. Thus, appropriate dispersants are proposed according to the type of CNT, experiment concentration, and treatment duration. Also, it is suggested that the dispersibility, dispersion stability, and biocompatibility of the selected dispersant should all be confirmed before a toxicity evaluation. © 2011 Springer-Verlag.

Park S.-S.,Korea University | Kwon S.-J.,Hannam University | Jung S.H.,Korea Conformity Laboratories | Lee S.-W.,Chosun University
Construction and Building Materials | Year: 2012

The pores and pore connectivity in concrete cause rapid water permeation. This is an important characteristic of porous material. Cracks in early aged concrete can be easily caused by restraint stress due to the process of hydration heat or drying shrinkage. Cracked concrete is vulnerable to water permeation. This can lead to rapid corrosion of the steel inside. In this paper, numerical modeling of water permeability in cracked concrete is performed, considering the behavior of early aged concrete such as porosity and saturation. Previously developed models that cover hydration, pore structure, and moisture transport are analyzed. The crack effect on water permeation in a representative elementary volume (REV) is analytically derived through averaging water permeation in sound concrete and crack width. An analysis technique is proposed through the equivalent permeability model in REV. Thirty-three concrete samples with crack width of 0.1-0.4 mm are prepared and water penetration tests (WPT) are performed to verify the proposed technique. The proposed technique is evaluated to reasonably predict both the increasing permeability with crack opening and the decreasing permeability with extended curing period. © 2011 Elsevier Ltd. All rights reserved.

Lee G.,Korea Conformity Laboratories | Han D.,University of Texas at Austin | Han M.-C.,Cheongju Univesrity | Han C.-G.,Cheongju Univesrity | Son H.-J.,Cheongju Univesrity
Construction and Building Materials | Year: 2012

This study investigates experimentally the synergistic effect of a polypropylene (PP) and a nylon (NY) fiber combination to provide improved spalling protection of high-strength concrete subjected to fire. Optimum levels of fiber contents for spalling protection with a less adverse effect on workability are provided based on the results of the fire test by varying the NY and PP fiber content. The combination of NY and PP fibers shows a synergistic effect on spalling protection; that is, by using a combination of NY and PP fibers, the same level of spalling protection is achieved using half as much fiber content as that when PP or NY fiber is used alone. The combined fibers show no explosion occurring even at 0.05% of NY (0.025% out of 0.05%) and PP (0.025% out of 0.05%) fiber content. By combining both the comparably low melting point of PP fiber, which is useful at the early stage of a fire, and the larger number of fibers that can be used due to the thinner diameter of NY fiber, which is useful at the later stage of fire, the combination of the two fibers can improve spalling protection by providing connections between pores with low fiber content. © 2012 Elsevier Ltd. All rights reserved.

Yoo S.W.,Woosuk University | Kwon S.-J.,Hannam University | Jung S.H.,Korea Conformity Laboratories
Construction and Building Materials | Year: 2012

This paper presents an analysis technique for AGS (autogenous shrinkage) in high performance concrete (HPC) with mineral and chemical admixtures. In this paper, comprehensive tests are performed to evaluate the behavior of AGS in HPC. Six mix proportions for evaluating the effect of FA (fly ash), SF (silica fume), and their combinations are prepared. Additional six mix proportions are also prepared for evaluation of the effect of SRA (shrinkage reducing agent), EA (expansive agent), and their combinations. Considering initial setting time and amount of admixture, analysis technique is proposed for prediction of AGS in HPC with mineral and chemical admixture, which can handle the compressive strain due to SRA and EA addition. The results from the proposed technique are compared with test results and they showed a reasonable agreement with test results for verification. © 2012 Elsevier Ltd. All rights reserved.

Park S.-S.,Korea University | Kwon S.-J.,Hannam University | Jung S.H.,Korea Conformity Laboratories
Construction and Building Materials | Year: 2012

Chloride-induced corrosion in reinforcing steel is one of the major durability problems in reinforced concrete (RC) structures. Fick's 2nd law can be simply applied to submerged RC structures however it has a very limited application to partially saturated condition. Furthermore, if RC structures have cracks on their surface in partially saturated condition, additional diffusion and permeation due to crack width should be considered for the quantitative evaluation of chloride penetration. In this paper, an analytical model is proposed for an evaluation of chloride behavior in cracked concrete. Both chloride diffusion and water permeation in a Representative Element Volume (REV) with crack are considered, which assume averaged transport of ion mass. Through rapid chloride penetration test (RCPT) for specimens with different crack width, crack effect on diffusion is analyzed considering crack width (0.1-0.4 mm). Utilizing the crack effect on diffusion and permeation, an analysis technique for chloride behavior in cracked concrete is proposed based on the framework considering thermodynamic coupling of hydration, moisture transport, and micro-structure formation. The proposed technique shows a possibility of evaluation for chloride penetration in partially saturated-cracked concrete through the comparison with the results from salt spraying test (SST), which are in good agreement. © 2011 Elsevier Ltd. All rights reserved.

Song M.Y.,Korea Conformity Laboratories | Song M.Y.,Konkuk University | Ku S.K.,Daegu Haany University | Kim H.J.,Keimyung University | Han J.S.,Konkuk University
Food and Chemical Toxicology | Year: 2012

Delayed gastrointestinal (GI) motility is frequent adverse effect associated with chemotherapy due to oxidative stress, activation of 5-HT3 receptors or serotonin releases from enterochromaffin cells. Fucoidan, extracts from brown seaweeds, has been showed antioxidant related favorable pharmacological activities including digestive tract protective effects. Low molecular weight fucoidan (LMF) obtained by acid hydrolysis of high molecular weight fucoidan has been showed more favorable bioactivities. This study was conducted to determine whether or not LMF can prevent delayed GI motility induced by the antineoplastic drug cisplatin chronically administered, once per week for five consecutive weeks. LMF ameliorating the chronic cisplatin treatment related body weight decreases, delayed GI motility, and enhanced the antioxidant defense systems. In addition, LMF also inhibited the cisplatin treatment related GI gastrin and serotonin changes, including enzyme activities involved in serotonin metabolism and enterochromaffin cells. The overall effects of LMF 10 mg/kg were similar to that of ondansetron 1 mg/kg, a serotonin 5-HT3 receptor antagonist. The present results supported that LMF have favorable ameliorating effect on the delayed GI motility induced by chemotherapy, modulated the GI enterochromaffin cells, serotonin and gastrin-producing cells with antioxidant effects. This effect of LMF may help improve accompanying digestive disorders by chemotherapy. © 2012 Elsevier Ltd.

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