• Title/Summary/Keyword: crystalline admixture

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Evaluation of Physical Properties of Liner and Cover Material Crystalline admixture (결정질혼화제를 함유한 광산차수재 물성평가)

  • Cho, Yong-Kwang;Kim, Jin-Sung;Kim, Chun-Sik;Jo, Sung-Hyun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.05a
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    • pp.227-228
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    • 2021
  • There are various problems caused by environmental pollution around the abandoned mines. In addition, they are exposed to the risk of safety accidents due to sinkholes caused by ground subsidence. Therefore, the ground is stabilized through the filling and construction of abandoned mines using industrial by-products. However, in the case of Backfill Material, secondary pollution caused by acidic drainage and leachate is not suppressed. To solve this problem, the liner and cover material is first installed. Therefore, in this study, the watertightness of the liner and cover material was improved by mixing crystalline admixtures by content.

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Applicability analysis of carbondioxide conversion capture materials produced by desulfurization gypsum for cement admixture (시멘트 혼합재로서 정유사 탈황석고를 활용하여 제조한 탄산화물의 적용성 분석)

  • Hye-Jin Yu;Young-Jun Lee;Sung-Kwan Seo;Yong-Sik Chu;Woo-Sung Yum
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.33 no.2
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    • pp.54-60
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    • 2023
  • In this study, microstructure and basic property analysis of DG (Desulfurization gypsum) and CCMs (Carbondioxide conversion capture materials) made by reacting CO2 with DG were conducted to analyze applicability as a cement admixture. The main crystalline phases of DG were CaO and CaSO4, and CCMs were CaSO4, CaCO3, Ca(OH)2 and CaSO4·H2O. As a result of particle size analysis, the difference in average particle sizes between the two materials was about 7 ㎛. No major heavy metals were detected in the CCMs, and as a result o f TGA, the CO2 decomposition of CCMs was more than twice as high as that of DG. Therefore, it was judged that CCMs could be used as a cement admixture through optimization of manufacturing conditions. As a results of measuring the strength behavior of DG and CCMs mixture ratios, the long-term strength of CCMs-mixed mortar was higher, and this is due to the filler effect of CaCO3 in CCMs.

The Study on the Pozzolanic Reactivity of Rice Straw Ash (소성볏짚의 포졸란 반응성에 관한 연구)

  • Kim, Sung-Hoon;Jeong, Euy-Chang;Kim, Young-Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2015.05a
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    • pp.36-37
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    • 2015
  • The purpose of this study is to investigate pozzolanic reactivity of the rice straw ash. This study focused on rice straw ash properties at various burning temperature and duration as a mineral admixture for mortar and concrete, and provide the crystalline state and molecular structure of rice straw ash. X.R.D and N.M.R were performed on rice straw ashes to identify pozzolanic reactivity.

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Investigation on the Self-Healing Performance of Cement Mortar Incorporating Inorganic Expansive Additives (무기질계 팽창재가 포함된 시멘트 모르타르의 자기치유성능에 관한 연구)

  • Shin, Jin-Wook;Her, Sung-Wun;Bae, Sung-Chul
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.4
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    • pp.404-412
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    • 2020
  • Herein, the properties and self-healing performance of cement mortar incorporating calcium sulfoaluminate(CSA), crystalline admixture(CA), and magnesium oxide(MgO) were investigated. Mortar strength test and water permeability experiments were conducted to analyze self-healing performance of the mortar. Also, variation in crack width were measured via digital optical microscope observation. The hydration products formed in the crack via self-healing were analyzed using x-ray diffraction(XRD), thermogravimetry(TG), and digital optical microscope. The analysis revealed that compressive strength and tensile strength increased as CA substitutional ratio increased. However, in the case of MgO replacement, the compressive strength and tensile strength decreased as the CA substitution ratio increased. The products in the recovered cracks are found to be mostly Ca(OH)2, MgCO3, and CaCO3. CaCO3 was shown to be the main healing product and had a higher portion than Ca(OH)2 and MgCO3 in the recovery products. Moreover, the optimal mix derived via water permeability and crack width results was 8% CSA + 1% CA + 2.5% MgO.

A Study for Improving Properties of Antiwashout Underwater Concrete Mixed with Mineral Admixtures (광물질 혼화재를 혼합한 수중불분리성 콘크리트의 물성 향상을 위한 연구)

  • 문한영;신국재;이창수
    • Journal of the Korea Concrete Institute
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    • v.14 no.3
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    • pp.409-419
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    • 2002
  • Nowadays, antiwashout underwater concrete is widely used for constructing underwater concrete structures but they, especially placed in marine environment, can be easily attacked by chemical ions such as SO$\^$2-/$\_$4/ Cl$\^$-/ and Mg$\^$2+/, so the quality and capability of concrete structures go down. In this paper, to solve and improve those matters, flyash and GGBFS(ground granulated blast furnace slag) were used as partial replacements for ordinary portland cement. As results of experiments for fundamental properties of antiwashout underwater concrete containing 10, 20, 30% of flyash and 40, 50, 60 % of GGBFS respectively, setting time, air contents, suspended solids and pH value were satisfied with the "Standard Specification of Antiwashout Admixtures for Concrete" prescribed by KSCE, and also slump flow, efflux time and elevation of head were more improved than that of control concrete. From the compressive strength test, it was revealed that the antiwashout underwater concrete containing mineral admixtures(flyash and GGBFS) is more effective for long term compressive strength than control concrete. An attempt to know how durable when they are under chemical attack has also been done by immersing in chemical solutions that were x2 artificial seawater, 5 % sulphuric acid solution, 10%, sodium sulfate solution and 10% calcium chloride solution. After immersion test for 91days, XRD analysis was carried out to investigate the reactants between cement hydrates and chemical ions and some crystalline such as gypsum ettringite and Fridel′s salt were confirmed.

Crack Self-Healing Performance According to Absorption Test of Fiber Reinforced Concrete (콘크리트의 흡수율에 따른 균열 자기치유 성능)

  • Woo, Hae Sik;Park, Byoung Sun;Yoo, Sung Won;Choi, Young Cheol
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.2
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    • pp.122-129
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    • 2019
  • Cracks in concrete structures are inevitable phenomena caused by shrinkage, hydration heat, and external loads. These cracks facilitate the penetration of external harmful ions into the concrete, which greatly reduces its durability. Recently, self-healing concrete has been actively studied. Also, self-healing fiber-reinforced concrete have been studied to control the crack in concrete and to maximize the shelf-healing capability. In this study, mortar specimens containing PVA fiber, fly ash and crystalline admixture were fabricated. The compressive and flexural strength were evaluated. Also, the self-healing performance was evaluated by the absorption test. From the results, it was confirmed that the amount of water absorbed by healing of the crack decreased as time increased. It was also found that PVA fiber is beneficial for the production of calcium carbonate, an additional healing product.