• Title/Summary/Keyword: 포졸란반응

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Air-Void Structure of Very-Early Strength Latex-Modified Concrete Using Ultra-Fine Fly Ash (울트라 파인 플라이 애시를 사용한 초속경 LMC의 공극구조 특성)

  • Choi, Pan-Gil;Park, Won-Il;Yun, Kyong-Ku;Lee, Bong-Hak
    • Journal of the Korean Society of Hazard Mitigation
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    • v.10 no.2
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    • pp.47-53
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    • 2010
  • Very-early strength latex-modified concrete (VES-LMC) was developed with a focus on workability, strength development and long-term durability that would allow for opening a bridge to traffic only 3 hours after concrete placement, which would be useful when repairing concrete bridge deck overlays. However, even though usage of latex in VES-LMC improves the durability, it has a disadvantage that it produces lots of entrained air. Therefore, specific plan is necessary since it is weak for freezing and thawing in air-void structure. In the present study ultra-fine fly ash (UFFA) was used. Test results are follows ; Air content of VES-LMC UFFA (VES-LMC using UFFA) concrete was decreased since major pozzolan reaction was happened in one day. It was also found that total air content of concrete was decreased with pozzolan reaction since air content in 28 days was the same with one day air content. The addition of calcium hydroxide increased entrained air which is smaller than size of 200 ${\mu}m$. It was effective to improve the air-void structure of VES-LMC since spacing factor can be confirmed as smaller than size of 200 ${\mu}m$ using more than 15% of UFFA.

Effect of Recycled Aggregates Powder on the Properties of Zero Cement Mortar Using the Recycled Fine Aggregates and Fly-Ash (순환잔골재와 플라이애시를 사용하는 무 시멘트 모르타르의 특성에 미치는 순환골재 미분말의 영향)

  • Park, Kyung-Taek;Son, Seok-Heon;Han, Cheon-Goo
    • Journal of the Korea Institute of Building Construction
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    • v.12 no.2
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    • pp.161-168
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    • 2012
  • The purpose of this study was to investigate the influence of recycled aggregates powder (RP) contents on recycled aggregates (RA) using fly-ash (FA) mortar in a condition of zero cement targeting earth filling materials, and the results can be summarized as follows. First, there was a tendency that as RP contents increased, W/B and air contents increased also. In the case of compressive strength, the strength was hardly developed at the early age, which was prior to 14 days; however, with the starting point of 14 days of age, strength of around 1.5~2.0 MPa was developed when it arrived at 28 days. At a curing temperature of $20^{\circ}C$, the more RP contents increased, the more the compressive strength increased in comparison with FA 100% at all levels except RP 100 %, showing the highest compressive strength at RP 25 %. At a curing temperature of $35^{\circ}C$, the temperature-dependence appeared to be large, as the RP contents were decreased compared to the curing temperature of $20^{\circ}C$. In addition, based on SEM analysis, this study was able to confirm that a pozzolanic reaction formed by an alkali stimulus of RA with the lapse of certain days even in 100 percent FA, causing the densification of tissues, and with RP 25%, hydrate was created the most densely by the hydration of unhydrated cement particles and pozzolanic reaction of FA.

Evaluation of Relationship between Strength and Resistance to Chloride in Concrete Containing Fly Ash with Ages (Fly Ash를 혼입한 콘크리트의 재령에 따른 강도와 염화물 저항능력간의 상관관계 평가)

  • Yoon, Yong-Sik;Park, Jae-Sung;Hwang, Chul-Sung;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.4
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    • pp.53-60
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    • 2017
  • Fly ash(FA) which is a byproduct in the coal combustion in thermal power plant contributes to pore structure densification due to pozzolanic reaction, and this leads to long-term strength development and excellent resistance to chloride penetration. In the work, compressive strength and chloride resistance in OPC(Ordinary Portland Cement) and FA-based concrete are evaluated, and the relationships are investigated considering ages. For the work, 3 different W/B (Water to Binder) ratios of 37%, 42%, and 47% are prepared, and 3 substitution ratio of fly ash(0%, 30%, and 50%) are considered as well. At the age of 28 days and 180 days, test results of compressive strength, diffusion coefficients based on Tang's method, and passed charges referred to ASTM C 1202 and KS F 2711 are obtained. With increasing replacement ratio of FA and decreasing W/B, the resistances to chlorides(diffusion coefficient and passed charge) are improved, and the results at the age of 180 days decrease to only 15% level at the age of 28 days due to pozzolanic reaction in FA 50 mixture, which shows that resistance to chloride is much dependent on age effect than strength development. After 180 days, more clear linear relationships are observed between strength and resistance to chloride.

Evaluation of Domestic CCPs(Coal Combustion Products) Quality by API Test Method (API시험법에 의한 국내 석탄회의 품질 평가)

  • Yoo, Sung-Won;Yu, Kyung-Geun;Cho, Young-Keun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.1 no.1
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    • pp.49-57
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    • 2013
  • Recently, recycling of industrial by-products and CO2 reduction have been important issues in the world. In this reason, applications and reuse of Fly ash as a binder for concrete, which is generated in thermoelectric power plant, have been one of the effective recycle methods. In order for Fly ash to be applied to concrete, Korean Standard(KS) has selected and managed quality such as $SiO_2$, fineness, specific gravity, ignition loss and activity index. However, there is a limits for activity index, whose test period required is at least 28 days or 91 days. Activity index is the critical indication standard to determine mechanical strength of concrete that contained Fly ash. To complement the disadvantage of test method, this research provided "API test method", which quickly measure Pozzolanic reaction of Fly ash can be considered as a alternative of activity index. Then, the adaptable API test method need to be investigated through comparative analysis with the test result of API, activity index and K-value. The test method can make evaluation of Fly ash quality faster and more accurate. As a result, most Fly ash produced in Korea has not been satisfied in the KS quality standard except water content and specific gravity, and especially fluidized bed boiler ash has its characteristics. Also, API, activity index and K-value have superior interrelationship. The interrelationship between API and activity index and K-value gets increased as the material age gets higher, so API test can be considered as very useful test method for Pozzolanic reaction evaluation of Fly ash.

A Study on the Pozzolan Reactivity and Mechanical Characteristic of Blended Portland Cements using CFBC Fly Ash (순환유동층 플라이 애시를 사용한 혼합시멘트의 포졸란 반응성과 역학적 성질에 관한 연구)

  • Park, JongTak;Oh, Hongseob
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.6 no.3
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    • pp.207-213
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    • 2018
  • Nowadays, circulating fluidized bed combustor(CFBC) boilers system that can reduce environmental pollution particles are widely used in electric power plants. But the fly ash generated from CFBC boilers has lower $SiO_2$ and higher MgO and $SO_3$ contents and also has free CaO inducing expansion and abrupt initial setting of concrete. Therefore, revised KSL5405 for CFBC fly-ash as well as pulverized coal combustion(PCC) is introduced in the concrete field. In this study, the chemical properties and mechanical properties of blended cements with PCC and CFBC fly-ash produced in Korea are analyzed. The blended cement with only CFBC fly ash shows a lower length change than OPC but a higher flow change ratio. The compressive strength of blended cement paste with PCC and CFBC fly ash is slightly greater than that of cement paste with only PCC fly-ash. Based on the results, CFBC flyash blended cement products should be used with PCC flyash to ensure the material stability and material properties.

Experimental Study on Physical Properties and Water Absorption Resistance Evaluation of Cement Mortar Incorporating Inorganic Metal Salt-based Water Repellent Powder (무기물 금속염계 발수분체를 혼입한 시멘트 모르타르의 물리적 특성 및 수분흡수저항성에 대한 실험적 연구)

  • Lee, Won Geun;Yoon, Chang Bok
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.4
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    • pp.609-616
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    • 2021
  • In this experimental, water-repellent powder, which is a metal salt-based inorganic substance, and natural zeolite powder, which is a pozzolan-based material, were mixed into cement mortar, and their physical properties and resistance to moisture were confirmed. It was confirmed that the test specimen using natural zeolite at the same time had excellent resistance in the water permeation test and the chloride penetration test as compared with the test specimen in which the inorganic metal salt-based water-repellent powder was mixed alone. When a metal salt-based water-repellent powder is used, it cannot be uniformly dispersed inside water due to its insoluble property, and is limited to the surface. When used at the same time as natural zeolite, the setting time at the initial stage of hydration is fast due to the pozzolan reaction, and the water-repellent powder adheres to the porous of the natural zeolite and is evenly distributed inside the test specimen to generate some water resistance.

Properties of carbonated green construction materials by changes in processing conditions (공정조건 변화에 따른 탄산화 녹색건자재의 물성)

  • Kim, Yootaek
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.23 no.3
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    • pp.152-160
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    • 2013
  • The purpose of this study is to enhance the mechanical strength of specimens containing fly ash from fluidized bed type boiler, which the recycling rate will be eventually increased. Specimens containing fly ash in a certain portion were made and aged for 3, 14, and 28 days. Specimens were carbonated under the supercritical condition at $40^{\circ}C$. The carbonation process under the supercritical condition was performed to enhance the mechanical property of specimens by filling the voids and cracks existing inside cement specimen with $CaCO_3$ reactants. The additional aging effect after the supercritical carbonation process on mechanical strength of specimens was also investigated by comparing the compressive strength with and without 7 day extra aging. Under the supercritical condition and additional 7 day aging specimens were very effective for enhancement of mechanical strength and compressive strength increased by 44 %.

Performance Evaluation of Admixture for Durability Improvement of Shielding Materials Used Waste Glass as Fine Aggregate (폐유리를 잔골재로 사용한 차폐채움재의 내구성 개선을 위한 혼화재료의 성능평가)

  • Hwang, Byoung-Il;Kim, Hyo-Jung;Song, Yong-Soon;Yi, Seong-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.2
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    • pp.20-27
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    • 2019
  • Compared to the development and manufacturing technology of electronic goods, the development of waste glass recycling technology is relatively insufficient, leading to the acceleration of waste of resources and environmental pollution. Although waste glass recycling technology is being actively developed overseas, waste glass recycling technology is insufficient in Korea, leading to the illegal dumping or burial of waste glass. Waste glass has been confirmed to have pozzolan reaction potential when having hydration reaction with cement. Waste glass is also reported to be effective in reducing bleeding and inhibiting the development of hydration heat by improving the physical properties of concrete and the rheology properties of fresh concrete. Therefore, this paper analyzed the strength characteristics and the effect of alkalic-silica reaction on the expansion of shielding concrete that used waste glass as fine aggregate. Where, suitable admixture materials were used as a measure to suppress the expansion.

Reactivity Improvement Characteristics of Weathered Feldspar through Activation Technique (활성기법을 통한 풍화된 장석의 반응성 개선 특성)

  • Cho, Jinwoo
    • Journal of the Korean Geosynthetics Society
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    • v.20 no.4
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    • pp.33-41
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    • 2021
  • Feldspar, along with Quartz, are the most frequently produced minerals in Korea; however, the potential value is estimated to be significantly low because of the scarce research on the development and application of material properties, except for their limited use in manufacturing minerals, glass, and paints. In this study, we analyzed the eco-friendly material and reactivity improvement characteristics of weathered feldspar through activation technique. The joint structural features observed on the surface of the weathered feldspar show that the joint arrangements are irregularly distributed, and the cavities are interconnected. Due to the irregularly connected cavities on the surface of weathered feldspar, the reaction area of the weathered feldspar is increased; hence the weathered feldspar is considered as a highly reactive pozzolan material when combined with cement. As a result of applying the thermal, mechanical, and chemical activation techniques to improve the functionality of the weathered feldspar, the cation exchange capacity, density, and uniaxial compression strength characteristics were improved. It is considered that weathered feldspar by these porous characteristics can be used as an eco-friendly construction material with excellent physical and chemical properties.

A Study on the Effect of Initial Strength of Cement Paste Containing Fly Ash or Blast Furnace Slag on CO2 Curing Period (플라이 애쉬 및 고로슬래그 혼입 시멘트 페이스트의 CO2 양생 기간에 따른 초기강도의 영향에 대한 연구)

  • Han, Jae-Do;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2018.11a
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    • pp.83-84
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    • 2018
  • As the concentration of greenhouse gases in the atmosphere increases, the reduction of CO2 is gaining worldwide attention. In the construction industry, cement replacement materials such as fly ash and blast furnace slag were investigated to reduce CO2 emissions in cement production process. Precast concrete is used in the field after manufacturing in the factory in the form of pipes and bricks because of shortening construction period and cutting construction cost. According to the results of previous research, it is known that early CO2 curing in concrete using OPC or fly ash has an initial strength enhancement effect and can be used for precast concrete production. Therefore, the purpose of this study is to evaluate the strength improvement effect by confirming the initial strength improvement effect when blast furnace slag is mixed.

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