• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.667-676
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• 2007

As the 21st century began, cement and concrete that are representatives of modem building materials became a major factor in global warming, air pollution and environmental pollution. Also, the problems that are generated while pursuing high performance and high strength became social issues. Therefore, it has become urgent to prepare counter plans. This study has aimed at the recycling of sewage sludge ash and developing it as a new concept in building material which serves the environmental considerations for long-lasting developmental purpose. Also, the study aimed to find a substitute for scarce natural resources and to secure high techniques for waste recycling. The purpose of this study was also to solve fundamentally secondary environmental pollution. The results revealed that the chemical components of sewage sludge ash are mainly $SiO_2\;and\;Al_2O_3$ which are similar to the components of pozzolan. Also, it was identified that sewage sludge ash can be utilized as a hardened specimen with an alkali activated pozzolan reaction. Considering the possibility of appropriate strength development and the advantage of drying shrinkage, compared with that of cement, it was believed that sewage sludge ash can demonstrate a function as a substitute for cement given.

• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.632-643
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• 2002

The purpose of this study was two-fold. First was to evaluate whether the molecular sieving model was appropriate for ionic dissociation experiment. Second was to compare the dissociation of calcium and hydroxyl ions from five types of calcium hydroxide pastes (Pure calcium hydroxide paste, DT temporary $dressing^{\circledR},{\;}Metapaste^{\circledR},{\;}Chidopex^{\circledR},{\;}Metapex^{\circledR}$) in three vehicles (aqueous, viscous and oily) and the antibacterial effect. Each calcium hydroxide pastes was placed into 0.65ml tube with cap and then 15% polyacrylamide gel was placed onto calcium hydroxide pastes. After the gel was hardened, the tubes were filled with tridistilled water (pH 7.14) and closed with cap. The tubes were stored in $37^{\circ}C$ 100% incubator The pH reading and the concentration of calcium ions were taken at 1, 4, 7. 10, and 14 days. The brain heart infusion agar plates with S. mutans and A. actinomycetemcomitans were used far antibacterial activity test. Middle of agar plate was filled with the calcium hydroxide pastes. The plates were incubated at $37^{\circ}C$ and observations were made to detect the zones of inhibition. These data were evaluated statistically by use of the analysis of variance and duncan test. The results were as follows. 1. In fresh mixing state, the pH of five types of calcium hydroxide pastes were measured between 12.5 and 12.8. 2. The pH was increased in all five types of calcium hydroxide pastes compared with control group. In 14 days, Pure calcium hydroxide paste (11.45) and DT temporary $dressing^{\circledR}$ (11.33) showed highest pH, followed by $Metapaste^{\circledR}$ (9.49), $Chidopex^{\circledR}$ (8.37) and $Metapex^{\circledR}$ (7.59) 3. Calcium was higher in all five types of calcium hydroxide pastes compared with control group. In 14 days, Pure calcium hydroxide paste (137.29 mg%) and DT temporary $dressing^{\circledR}$ (124.6 mg%) showed highest value, followed by $Metapaste^{\circledR}$ (116.74 mg%), $Chidopex^{\circledR}$ (111.84 mg%) and $Metapex^{\circledR}$ (60.22 mg%). 4. The zones of bacterial inhibition were seen around all five types of calcium hydroxide pastes. $Chidopex^{\circledR}{\;}and{\;}Metapex^{\circledR}$ groups which include iodoform were observed significantly larger zone of inhibition in A. actinomycetemcomitans compared with the other calcium hydroxide groups (p<0.05) However, $Metapex^{\circledR}$ showed the least antibacterial effect on S. mutans compared with other groups (p<0.05). The molecular sieving model was found to be acceptable in dissociation experiment of hydroxyl and calcium ions when compared with the previous tooth model study. But this model was not appropriate for the antibacterial test.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.473-479
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• 2010

The objective of the paper is to experimentally investigate the effect of commercially avaliable fiber types such as polypropylene (PP), nylon (NY), polyvinyl alcohol (PVA) and cellulose (CL) on the engineering properties of concrete for pavement application. The results, showed the fluidity tends to decrease with fibers addition compared to that of plain concrete. As for the effect of fiber types on fluidity loss, use of NY appear to give the most favorable results among all of the fiber types investigated in this study while the effect of the fibers on air content was negligible. For the properties of hardened concrete, compressive and flexural strengths increased with fibers compared to plain concrete. The contribution of NY fibers to strength was the highest followed in the order by NY, PVA, PP, and CL. However, in the case of the splitting tensile strength, its values were increased with NY and PP only. For porosity based on MIP(mercury intrusion penetration) method, the number of around 1 was observed when NY was mixed resulting in increased cumulated amounts of porosity compared with that of plain mix. Thus, based on the consideration of fluidity and strength it was found that the addition of NY fiber showed the optimal results under the conditions applied in this study.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.541-550
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• 2011

Many researches have been performed on concrete with fly ash and bottom ash. However researches on concrete with pond ash (PA) and its application to RC (Reinforced Concrete) structure are limitedly carried out. This paper presents an applicability of PA concrete in construction of real size structure. Referring to the previous study, 2 domestic PA samples with normal performance are selected and 2 replacement ratios (25% and 50%) to fine aggregate are considered for 5 PA concrete structures consisting of column, slab, and wall. In order to evaluate the property of fresh concrete, several tests including air content, slump, and setting time are performed. Using cored out samples from hardened PA concrete structure, tests for strength, resistance to carbonation and chloride penetration are carried out and compared with control samples. Additionally, tests for rebound hardness, drying shrinkage, and hydration heat are performed for PA concrete structure. The test results showed that PA concrete has reasonable strength and durability performances compared to those of normal concrete. Therefore, its potential application to RC structure is promising. The PA aggregate can be more actively used for RC structures with better quality control for content of fly ash, bottom ash, and unburned carbon.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.129-136
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• 2010

This study is to investigate experimentally the engineering characteristics of cement mortar according to the replacement method and contents of recycled aggregate powder (RP) by collecting the recycled aggregate powder with the maximum size of below 0.08 mm and 0.15 mm. then, the results of the study can be summarized as follows. The flow of flesh mortar represented a trend in decreasing while the recycled aggregate powder was substituted as it is compared with that of plain. In addition, in case of correlation between tests, it appeared that the correlation between flow and ring flow is big. In the case of the characteristics of hardened mortar, the strength showed more improvements as the RP was substituted to aggregate than the case, which is substituted to aggregate. In addition, it was verified that the results in which the RP was substituted to aggregate by 5% represented similar values to that of the plain according to the passage of age.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.2
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• pp.61-69
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• 2020

Purpose: Zirconia fixed partial dentures with mandibular 2^nd premolar and 2^nd molar as abutments are fabricated and then the effects of inter-abutment distance on fracture resistance of zirconia fixed partial dentures is studied. Materials and Methods: The materials used in this study are Cameleon S zirconia block and S2 zirconia block, which are divided into CS Group and S2 Group applying different inter-abutment distance for each material, and the sintered zirconia fixed partial denture was luted to the epoxy resin die using a temporary luting cement, and then the fracture resistance was measured by placing a 6 mm diameter hardened steel ball on the occlusal surfaces of the pontics and applying pressure at a cross head speed of 1.0 mm/min on a universal testing machine with a load cell of 5.0 kN. Results: The fracture resistance of zirconia fixed partial dentures is not significantly affected by inter-abutment distance The fracture resistance of zirconia fixed partial dentures in CS Group was significantly higher in 15 mm of inter-abutment distance than in 13 mm and 17 mm of inter-abutment distance (P < 0.05). The fracture resistance of zirconia fixed partial dentures in S2 Group was not significantly different between the three groups (P > 0.05). Conclusion: The fracture resistance of zirconia fixed partial dentures with mandibular 2^nd premolar and 2^nd molar as abutments does not significantly affected by the inter-abutment distance.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.117-128
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• 2016

Chemical reaction tests were performed to assess the properties of hardened specimens of cement pastes (KS-1 Portland and Class G) exposed to supercritical CO₂ for 1, 10, and 100 days. After exposure, the samples' measured permeability and strength were compared with values measured for pristine samples. The pristine cements had permeabilities of 0.009~0.025 mD, which increased by one order of magnitude after 100 days of exposure (to 0.11~0.29 mD). The enhancement of permeability is attributed to the stress release experienced by the samples after removal from the pressure vessel after exposure. Despite its enhancement, the measured permeability mostly remained lower than the API (American Petroleum Institute) recommended maximum value of 0.2 mD. The degradation of the cement samples due to exposure to supercritical CO₂ led to a layer of altered material advancing inwards from the sample edges. The Vickers hardness in the altered zone was much higher than that in the unaltered zone, possibly owing to the increase in density and the decrease in porosity due to the carbonation that occurred in the altered zone. Hardness close to the edge within the altered zone was found to have decreased significantly, which is attributed to the conversion of C-S-H into less-strong amorphous silica.

• Economic and Environmental Geology
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• v.51 no.5
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• pp.429-438
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• 2018

Since concrete is a hardened aggregates of various materials, it needs to be crushed for chemical analyses. However, the effect of sample crushing on the analytical results has not been precisely assessed till today. In this study, we prepared concrete test pieces using Portand cements and fly ashes as binding materials, and ponded ashes and sands as aggregates and analyzed the heavy metals of the test pieces using Standards for Fair Testing of Soil Contamination (SFTSC) and Wastes (SFTW). For this, each test piece was partially crushed at first and sieved for separation of grains of <0.15 mm, 0.15-0.5 mm, and 0.5-5 mm from the same crushed samples (Crushing Method I). Results of those samples using SFTSC showed a clear trend that analyzed heavy metal concentrations are higher in the finer fractions. Particularly, fractions with <0.15 mm indicated much higher concentrations than the theoretical ones, which were calculated based on the concentrations of individual materials and their mixing fractions. In contrast, the analytical results were generally comparable with the theoretical ones when the test pieces were totally pulverized such that all the crushed grains were <0.15 mm in size (Crushing Method II). These results are associated with the fact that cement materials and fly ashes, which are high in heavy metals relative to other materials, are enriched in the fine fractions. The analytical results using the SFTW derived very low concentrations in most of parameters and did not indicate the dependence of concentrations on the crushing methods due to using distilled water as leaching agent.

• Korean Journal of Environmental Agriculture
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• v.1 no.2
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• pp.99-104
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• 1982

These studies were carried out to investigate the damage of root rot of hop by heptachlor residues in soil at nine farm fields and pot experiment for two years from 1980 to 1981. 1) Pot experiment results indicated that root rot of hop occurred in farm field were caused by heptachlor phytotoxicity. 2) The damage of root rot of the hop was found by heptachlor residues in soil. Hop root in the low concentration of heptachlor was turned to brown mottle, and then rotted. In high concentration, the hop root was decreased in number, blocked in growth, and resulted to greyish change with death. 3) Hop vine damaged by heptachlor was hardened and broken with ease. 4) Heptachlor epoxide which was inferred to be the main cause of hop root rot gave the damage to hop at 0.009 ppm reisdues in soil. 5) The phytotoxicity of heptachlor was proved to last for 10 years or more in this study.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.7-7
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• 2011

Quantum beam technology has been expected to develop breakthroughs for nanotechnology during the third basic plan of science and technology (2006~2010). Recently, Green- or Life Innovations has taken over the national interests in the fourth basic science and technology plan (2011~2015). The NIMS (National Institute for Materials Science) has been conducting the corresponding mid-term research plans, as well as other national projects, such as nano-Green project (Global Research for Environment and Energy based on Nanomaterials science). In this lecture, the research trends in Japan and NIMS are firstly reviewed, and the typical achievements are highlighted over key nanotechnology fields. As one of the key nanotechnologies, the quantum beam research in NIMS focused on synchrotron radiation, neutron beams and ion/atom beams, having complementary attributes. The facilities used are SPring-8, nuclear reactor JRR-3, pulsed neutron source J-PARC and ion-laser-combined beams as well as excited atomic beams. Materials studied are typically fuel cell materials, superconducting/magnetic/multi-ferroic materials, quasicrystals, thermoelectric materials, precipitation-hardened steels, nanoparticle-dispersed materials. Here, we introduce a few topics of neutron scattering and ion beam nanofabrication. For neutron powder diffraction, the NIMS has developed multi-purpose pattern fitting software, post RIETAN2000. An ionic conductor, doped Pr2NiO4, which is a candidate for fuel-cell material, was analyzed by neutron powder diffraction with the software developed. The nuclear-density distribution derived revealed the two-dimensional network of the diffusion paths of oxygen ions at high temperatures. Using the high sensitivity of neutron beams for light elements, hydrogen states in a precipitation-strengthened steel were successfully evaluated. The small-angle neutron scattering (SANS) demonstrated the sensitive detection of hydrogen atoms trapped at the interfaces of nano-sized NbC. This result provides evidence for hydrogen embrittlement due to trapped hydrogen at precipitates. The ion beam technology can give novel functionality on a nano-scale and is targeting applications in plasmonics, ultra-fast optical communications, high-density recording and bio-patterning. The technologies developed are an ion-and-laser combined irradiation method for spatial control of nanoparticles, and a nano-masked ion irradiation method for patterning. Furthermore, we succeeded in implanting a wide-area nanopattern using nano-masks of anodic porous alumina. The patterning of ion implantation will be further applied for controlling protein adhesivity of biopolymers. It has thus been demonstrated that the quantum beam-based nanotechnology will lead the innovations both for nano-characterization and nano-fabrication.