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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.

Yeon K.-S.,Kangwon National University | Yeon J.H.,Gachon University | Choi Y.-S.,Korea Conformity Laboratories | Min S.-H.,Kangwon National University
Construction and Building Materials | Year: 2014

Objective: This study explores the deformation characteristics of acrylic polymer concrete (PC) to examine the viability of using acrylic PC as an infrastructure material. Materials: An acrylic resin with benzoyl peroxide (BPO) initiator and N,N-dimethylaniline (DMA) accelerator was used as a binder for PC. As an auxiliary accelerator, methacrylic acid (MAA) was employed. Methods: A series of laboratory experiments was performed to measure the setting shrinkage, coefficient of thermal expansion (CTE), and stress-strain relation of acrylic PC. Experimental variables were MAA contents (0, 5, and 10 parts per hundred parts of resin (phr)) and curing temperatures (10, 20, and 30 °C). Results: The result showed that the ultimate setting shrinkage tended to increase as the MAA content and curing temperature increased. Furthermore, it was found that MAA had a significant effect on the rate of setting shrinkage development especially at very early ages. The CTE of acrylic PC tended to decrease with the increased MAA content. The experimental results also indicated that compressive strength, ultimate compressive strain, and modulus of elasticity of acrylic PC were substantially affected by MAA content. © 2014 Elsevier Ltd. All rights reserved.

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.

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.

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.

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