• Title/Summary/Keyword: cement composition

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Recent Trend of Esthetic All-Ceramic Materials and Guidelines for Correct Cementation (올세라믹 심미 수복재료의 최신 동향과 적합한 시멘트 선택 및 사용)

  • Park, Yeong-Joon
    • The Journal of the Korean dental association
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    • v.58 no.7
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    • pp.413-434
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    • 2020
  • Recently, there are much improvement in optical and mechanical properties of dental ceramic materials coupled with improved fabrication techniques, which have caused a considerable shift in the preference of the dentists to ceramic restorations. Because the chemical composition and microstructure of all-ceramic materials are different by the type, correct choice of cement type and surface treatment procedure, and cementation strategy is essential for the success of ceramic restorations with adequate retention and decreased incidence of complications. This manuscript reviews on the most often prescribed and some newly developed ceramic materials, and the selection criteria and usage guidelines of cement materials that are used in conjunction with various ceramic materials. This manuscript emphasizes that continuous updating the information of newly developed ceramic and cement materials and application techniques by the dentists and dental staffs are demanding in response to the constantly improving ceramic and cement materials and corresponding application protocol changes.

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Microstructure and Mechanical Strength of Hardened Paste of Hydroxyapatite Cement Containing Whisker Phase (휘스커상을 함유한 수산화아파타이트시멘트 경화체의 미구조-강도 특성)

  • 손영도;송태웅
    • Journal of the Korean Ceramic Society
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    • v.36 no.12
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    • pp.1342-1349
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    • 1999
  • In order to improve the density and the mechanical strength without change in chemical composition the hardened pastes of hydroxyapatite cement were reinforced with powders and/or whiskers of hydroxyapatite. The powders behaved as a seed of hydroxyapatite formation rather than a filler while the whiskers were mrerly dispersed in matrix and capillary pores of the hardened bodies leading to increase in mechanical strength. But the increase in strength But the increase in strength was nnt enough owing to the lack of homogeneous dispersion of the fibers. The highest diametral tensile strength of 18.5 MPa was measured at the hardened hydroxyapatite body in which well-dispersed whisker phase formed uniformly during hydro-thermal curing of power-added and dry-formed hydroxyapatite cement.

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Studies on Manufacturing Possibility of Paper Sludge-Cement Boards (II) - Physical and Mechanical Properties and SEM Observation - (제지(製紙) 슬러지-시멘트보드이 제조가능성(製造可能성)에 관(關)한 연구(硏究)(II) - 물리(物理)·기계적(機械的) 성질(性質) 및 SEM 측정(測定) -)

  • Kim, Sa-Ick;Oh, Jung-Soo
    • Journal of the Korean Wood Science and Technology
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    • v.22 no.2
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    • pp.37-45
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    • 1994
  • The possibility of reusing the paper sludge as a raw material of composition board mixed with cement was investigated. For the measurement of physical and mechanical properties, wood coment board and sludge combinend cement boards were fabricated with the three weigh ratios of paper sludge 10 % (SI), 20 % (S II) and 30 % (S III) to cement weight. For adding the cement hardning, $CaCl_2$ was also added to each mixed paste with the ratio of 1 %, 3 % and 5 % to cement weight, respectively. Crystal formation in paper sludge-, wood-cement composites was observed by scanning electron microscope. The results were summarized as follows. 1. Density and partial compressive strength of each specimens were relatively high in the order of sludge I, sludge II, Korean pine, Italian poplar and sludge III, sludge I, Korean pine, sludge II, Italian poplar and sludge III. 2. The mechanical properties of sludge-cement boards (S I and II) were higher than that of wood-cement boards prepared with Korean pine and Italian poplar. But the mechanical properties of wood-cement boards were improved by the adding of $CaCl_2$. 3. Water absorption and thickness swelling were increased with increase of sludge content to cement weight. 4. In SEM observation, sludge-cement composites showed sufficiently formed crystals but wood-cement composites showed poorly formed crystals.

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Enhancement of the Characteristics of Cement Matrix by the Accelerated Carbonation Reaction of Portlandite with Supercritical Carbon Dioxide

  • Kim, In-Tae;Kim, Hwan-Young;Park, Geun-Il;Yoo, Jae-Hyung;Kim, Joon-Hyung;Seo, Yong-Chil
    • Proceedings of the IEEK Conference
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    • 2001.10a
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    • pp.586-591
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    • 2001
  • This research investigated the feasibility of the accelerated carbonation of cement waste forms with carbon dioxide in a supercritical state. Hydraulic cement has been used as a main solidification matrix for the immobilization of radioactive and/or hazardous wastes. As a result of the hydration reaction for major compounds of portland cement, portlandite (Ca(OH)$_2$) is present in the hydrated cement waste form. The chemical durability of a cement form is expected to increase by converting portlandite to the less soluble calcite (CaCO$_3$). For a faster reaction of portlandite with carbon dioxide, SCCD (supercritical carbon dioxide) rather than gaseous $CO_2$, in ambient pressure is used. The cement forms fabricated with an addition of slated lime or Na-bentonite were cured under ambient conditions for 28days and then treated with SCCD in an autoclave maintained at 34$^{\circ}C$ and 80atm. After SCCD treatment, the physicochemical properties of cement matrices were analyzed to evaluate the effectiveness of accelerated carbonation reaction. Conversion of parts of portlandite to calcite by the carbonation reaction with SCCD was verified by XRD (X-ray diffraction) analysis and the composition of portlandite and calcite was estimated using thermogravimetric (TG) data. After SCCD treatment, tile cement density slightly increased by about 1.5% regardless of the SCCD treatment time. The leaching behavior of cement, tested in accordance with an ISO leach test method at 7$0^{\circ}C$ for over 300 days, showed a proportional relationship to the square root of the leaching time, so the major leaching mechanism of cement matrix was diffusion controlled. The cumulative fraction leached (CFL) of calcium decreased by more than 50% after SCCD treatment. It might be concluded that the enhancement of the characteristics of a cement matrix by an accelerated carbonation reaction with SCCD is possible to some extent.

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Sulfate Attack According to the Quantity of Composition of Cement and Mineral Admixtures (시멘트 화학성분(C3A)과 무기 혼화재에 따른 황산염 침투 특성)

  • Ahn, Nam-Shik;Lee, Jae-Hong;Lee, Young-Hak
    • Journal of the Korea Institute of Building Construction
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    • v.11 no.6
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    • pp.547-556
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    • 2011
  • The primary factors affecting concrete sulfate resistance are the chemical composition of the Portland cement, and the chemistry and quantity of mineral admixtures. To investigate the effect of those on the sulfate attack, the testing program involved several different mortar mixes using the standardized test, ASTM C1012. Four different cements were evaluated, including one Type I cement, two Type I-II cements, and one Type V cement. Mortar mixes were also made with mineral admixtures, as each cement was combined with three different types of mineral admixtures. One Class F fly ash, one Class C fly ash, and one ground granulated blast furnace slag (GGBFS) were added in various percent volumetric replacement levels. Expansion measurements were taken and investigated with the expansion criteria recommended by ASTM.

Raw Materials Composition of Recycled Cement from Waste Concrete Powder (폐콘크리트 미분말을 활용한 재생시멘트의 원료조합)

  • Kwon, Eun-Hee;Ahn, Jae-Cheol;Park, Dong-Cheon;Kang, Byeung-Hee
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2012.11a
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    • pp.61-62
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    • 2012
  • This study is for analyzing possibility of utilizing as cement from waste concrete. The scrapped fine powder which contains a large amount of hydrate of cement can supercede lime stone, and greenhouse gas reductions are expected. However, Fine Aggregate powder efficient separation technology development is essential for that limestone substitution effect and reduce greenhouse gas emissions in order to facilitate through the recycling of the scrapped fine powders.

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Oyster Shell waste is alternative sources for Calcium carbonate (CaCO3) instead of Natural limestone

  • Ramakrishna, Chilakala;Thenepalli, Thriveni;Nam, Seong Young;Kim, Chunsik;Ahn, Ji Whan
    • Journal of Energy Engineering
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    • v.27 no.1
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    • pp.59-64
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    • 2018
  • In this paper, we investigated the alternative sources of limestone. Oyster shell waste originated from aquaculture that causes a major disposal landfill problem in coastal sectors in southeast Korea. Their inadequate disposal causes a significant environmental problems araised. Bio mineralization leads to the formation of oyster shells and consists $CaCO_3$ as a major phase with a small amount of organic matter. It is a good alternative material source instead of natural lime stone. The utilization of oyster shell waste for industrial applications instead of natural limestone is major advantage for conservation of natural limestone. The present work describes the limestone and oyster shells hydraulic activity and chemical composition and characteristics are most similar for utilization of oyster shell waste instead of natural limestone.

The Experiment Study on Chloride Binding of Cement Paste According to The Al/Ca+Si Ratio (Al/Ca+Si 비에 따른 시멘트 페이스트의 염화물 고정에 관한 실험적 연구)

  • Lee, Yun-Su;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2016.05a
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    • pp.51-52
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    • 2016
  • This paper researches the Chloride Binding of Cement Paste according to the Ca/Si and Ca/Al Ratio. The mechanisms of chloride ion binding are not completely known, although it is believed that Alumina contents in cementitious system have an important role. For changing cement paste composition, Ordinary Portland Cement(OPC) paste is substituted by Granulated Ground Blast Slag(GGBS). With increasing the ratio of GGBS substitution(Thus alumina contents is increasing), The chloride binding capacity has a tendency to increase of binding chloride ion capacity.

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Study on the Strength Development of cement paste using High-Early-Strength Cement and Hardening Accelerator (조강시멘트와 경화촉진제가 압축강도에 미치는 영향에 대한 실험적 연구)

  • Min, Tae-Beom;Jo, In-Seong;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2013.05a
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    • pp.56-58
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    • 2013
  • In order to develop concrete generating compressive strength of 15MPa~30MPa aging for 6~12 hours in the room temperature curing, Hardening accelerator containing Ca2+ mixed with rapid hardening portland cement containing C3S in quantity. The result was that the more addictive contents of Hardening accelerator is, the more greatly early compressive strength was improved. That s because the composition of Ca(OH)2 was mass-produced at early-ages.

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A Study on the Evaluation Method of Water Leakage Repair in Polyacrylic Resin (폴리 아크릴 레진의 누수 보수 평가에 관한 연구)

  • Cho, Il-Kyu;Kim, Keun-Hur;Oh, Sang-Keun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2017.11a
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    • pp.223-224
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    • 2017
  • In this study, various materials such as epoxy material, urethane material, cement material, and acrylic material are used to solve the water leakage occurring in underground structures. However, in the reality that the durability is insufficient and the effect is insufficient, it is aimed to improve the repairing effect by using cement and acrylics in combination. As a first study, we tried to verify the performance of improve the performance by checking the product properties according to the composition ratio of polyacrylic resin. Polyacrylic resin is evaluated in three different composition ratios. When the material is selected for polyacrylic resin, it is applied to the field to understand the maintenance effect and durability.

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