• Title/Summary/Keyword: cement substitute

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Strength behaviour and hardening mechanism of alkali activated fly ash Mortars (알카리 활성화에 의한 fly ash 경화체의 강도 발현 메카니즘에 관한 연구)

  • Jo Byung Wan;Moon Rin Gon;Park Seung Kook;Lim Sang Hun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.321-324
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    • 2004
  • The discharge of fly ash that is produced by coal-fired electric power plants is rapidly increasing in Korea. The utilization of fly ash in the raw materials would contribute to the elimination of an environmental problem and to the development of new high-performance materials. So it is needed to study the binder obtained by chemically activation of pozzolanic materials by means of a substitute for the exiting cement. This paper concentrated on the strength development according to the kind of chemical activators, the curing temperature, the heat curing time. Also Scanning electron microscopy and X-Ray diffraction analysis show what the reaction products of the alkali activated fly ash are.

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An Experimental Study on the Physical Properties of Foamed Concrete Using Bottom Ash (바텀 애쉬를 이용한 기포콘크리트의 물리적 특성에 관한 실험적 연구)

  • Kang Ki Woong;Kang Chul;Kwag Eun goo;Shin hong cheol;Kwon Ki Joo;Kim Jin Man
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.525-528
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    • 2004
  • The annual consumption of coal by coal-fired power plants is increasing. Also a large amount of ash is produced. The disposal of this large amount of ash makes the serious environmental problems and economical loss. Fly ash among the ash produced is used in building industries as a substitute to cement in concrete. But bottom ash is not used because of its poor properties. This study is aimed at the production of foamed concrete using bottom ash, to examine the physical properties of foamed concrete is manufactured by autoc1aving, and to exhibit the fundamental data to use it in site.

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A Study on Using Possibility of Talc Powder as Concrete Admixture (활석 미분말의 콘크리트용 혼화재료로써 활용가능성에 관한 연구)

  • Woo, Jong-Kwon;Ryu, Hyun-Gi
    • Journal of the Korea Institute of Building Construction
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    • v.6 no.4 s.22
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    • pp.93-98
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    • 2006
  • Admixture materials are used in mixing concrete or mortar to improve quality and performance of the concrete. This study examines the potential use of talc as a substitute for cement, the benefits of recycling waste resources for economical efficiency and quality improvement of concrete. The test was carried out by replacing the plain mix with fine grains of talc at the rate of 10%, 20%, and 30%. Talc was divided into three groups depending on the degree of pulverizing. For wet concrete, porosity, slump, bleeding per unit, and setting time by penetration resistance were measured; similarly, for dry concrete, strength and watertight Property were tested. Test results showed that the amount of bleeding and setting time could be shortened, but the strength and watertight proofing severely deteriorated. However, at the replacement rate of 10%, talc showed equal performance with the plain at all degrees of pulverization, which suggests its potential use as admixture material.

Evaluation of Resistance to Freezing and Thawing of Concrete using Industrial by-products Aggregate (산업부산물 골재를 사용한 콘크리트의 내동해성 평가)

  • Choi, Sung-Woo;Ryu, Deug-Hyun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.226-227
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    • 2021
  • Various attempts are being made to reduce carbon emissions through recycling of industrial by-products in the construction materials industry to reduce carbon emissions, and cement substitutes such as blast furnace slag and fly ash are widely used. Although it is suggested that the use of industrial by-product aggregate is possible in 'Aggregate', the use case of industrial by-product aggregate is very rare in the actual field. In this study, as an industrial by-product, fine slag aggregate is used as fine aggregate among aggregates that can be used as aggregate for concrete, and coarse aggregate is used as a substitute for natural aggregate. WWe tried to suggest various ways to expand the use of industrial by-product aggregates.

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Properties of Mortar mixed with Lignocellulosic Combustion By-products (목질계 연소부산물 혼입 모르타르 물성 평가)

  • Jeong, Young-Dong;Kim, Min-Soo;Park, Won-Jun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.11a
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    • pp.77-78
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    • 2023
  • This paper experimentally examined the recycling of combustion by-products emitted from a combined heat and power plant using lignocellulosic biomass fuel. Physical and chemical analyzes were performed on Bio-SRF and three types of wood pellet combustion by-product samples (fly-ash, FA). As a result of the experiment, the compressive strength of mortar substituted with 5, 10, and 20% of FA compared to the cement weight was found to be excellent, and its recyclability was confirmed as a substitute for existing admixtures.

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The Feasibility Study for Utilization of Blended Cement as a Activator of Bottom Ash from Circulating Fluidized Bed Combuster Boiler (순환유동층 보일러 바텀애시의 혼합시멘트 자극제 활용을 위한 타당성 연구)

  • Park, JongTak;Jung, Gwon Soo;Kang, Chang Ho;Oh, Hongseob
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.3
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    • pp.255-262
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    • 2020
  • Blended cement with fly ash and bottom ash from Circulating Fluidized Bed Combustor boiler(CFBC) burned at a low temperature, can be high heat of hydration and abnormal setting caused by higher volumn contents of Fe2O3, free-CaO, SO3. In this study, the ground CFBC bottom ash powder mixed with blast furnace slag was used as substitute activator of gypsum and recycled iron slag was produced from mix and pulverized by ball mill to increase the recycling rate. The effect on compressive strength of cements with the mixture of original and hydrated bottom ash mixtures with BFS with small water, respectively, was analyzed, and it was found that the hydrated bottom ash activator was more effective in initial strength development. To improve the initial strength of blended cement, an activator mixed with a blast furnace slag and bottom ash mixing ratio of 5:95 and 10:90, respectively, the slag cement by about 6%, and it was analyzed to develop an initial strength similar to gypsum as a conventional activator.

CaO Optimal Classification Conditions for the Use of Waste Concrete Fine Powder as a Substitute for Limestone in Clinker Raw Materials (폐콘크리트 미분말을 클링커 원료의 석회석 대체재로 사용하기 위한 CaO 최적 분급 조건)

  • Ha-Seog Kim;Sang-Chul Shin
    • Land and Housing Review
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    • v.15 no.1
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    • pp.147-156
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    • 2024
  • This study aims to reduce CO2 generated during the manufacturing process by using limestone (CaCO3), a carbonate mineral used in the production of cement clinker, as a decarbonated raw material that does not contain CO2. Among various industrial by-products, we attempted to use cement paste attached to waste concrete. In general, limestone for cement must have a CaCO3 content of at least 80% (CaO, 44% or more) to ensure the quality of cement clinker. However, the CaO content of waste concrete fine powder is about 20% on average, so in order to use it as a cement clinker raw material, the CaO content must be increased to more than 35%. Therefore, by using the difference in hardness of the mineral composition of waste concrete fine powder to selectively crush CaO type minerals with relatively low hardness, classify and sieve, the CaO content can be increased by more than 35%. Accordingly, in this study, we experimentally and statistically reviewed and analyzed the optimal conditions for efficiently separating CaO and SiO2 and other components by selectively pulverizing minerals containing relatively low CaO through a grinding process. As a result of the optimal grinding conditions experiment, it was found that the optimal conditions were a grinding time of less than 5 minutes, a type of material to be crushed of 30 mm, and an amount of material to be crushed of 1.0 or more. However, it is judged that it is necessary to review pulverized materials of mixed particle sizes rather than pulverized products of single particle size.

A Study of the Characteristics of the High-Flowable Concrete (고유동콘크리트의 특성에 관한 실험적 연구)

  • Jeon, Hyun-Kyu;Kim, Dae-Hoi;Lee, Jong-Chan;Ji, Suk-Won;Yoo, Taek-Dong;Seo, Chee-Ho
    • Journal of the Korea Institute of Building Construction
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    • v.3 no.2
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    • pp.129-134
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    • 2003
  • In this research, we used fly-ash and blast-furnace slag as substitute material of cement and fine aggregate, and we, through experiments, researched and analyzed the features of high-flowable concrete added high efficiency AE water reduction agent. The results are below. 1. Liquefaction generally presented high-slump flow value; on the other hand, partial segregation was observed in case of mixing proportion with 65 cm slump flow and above. This segregation was partially improved in accordance with mixing admixture. 2. Compressive strength according to mixing admixture and increasing mixing ratio of fly-ash were subject to be declined when it was initially cast-in, but its gap was improved when time was fully passed. 3. After mixing blast-furnace slag and fly-ash as substitute material, the result showed that the modulus of elasticity against freezing & melting was improved according to mixing blast-furnace slag and also increased in accordance with increasing pulverulent-body volume. 4. According to increasing the mixing volume of fly-ash, the durability factor was deteriorated because compressive strength became lower as well as air content was decreased when it was initially case-in. 5. The minimum air content to secure durability was 3.7%, for that reason, we had better secure admixture such as air entraining agent when cast-in high-flowable concrete.

Mechanical, rheological, and durability analysis of self-consolidating concretes containing recycled aggregates

  • Hiwa Mollaei;Taleb Moradi Shaghaghi;Hasan Afshin;Reza Saleh Ahari;Seyed Saeed Mirrezaei
    • Structural Engineering and Mechanics
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    • v.88 no.2
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    • pp.141-157
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    • 2023
  • In the present paper, the effect of recycled aggregates on the rheological and mechanical properties of self-consolidating concrete is investigated experimentally and numerically. Hence, the specimen with two types of recycled aggregates, i.e., known and unknown resistance origins, are utilized for the studied specimens. The experiments in this study are designed using the Box-Behnken method, which is one of the response surface methods. Input variables in mixtures include silica fume in the range of 5-15% as a percentage substitute for cement weight and recycled coarse and fine aggregates in the range of 0-50% for both series of recycled materials as a substitute for natural materials. The studied responses are slump flow, V funnel, compressive strength, tensile strength, and durability. The results indicate that the increase in the amount of recycled aggregates reduces the rheological and mechanical properties of the mixtures, while silica fume effectively improves the mechanical properties. In addition, the results demonstrate that the fine recycled aggregates affect the total response of the concrete significantly. The results of tensile and compressive strengths indicate that the mixtures including 50% recycled materials with known resistance origin demonstrate better responses up to 8 and 10% compared to the materials with unknown resistance origins, respectively. Recycled materials with a specific resistance origin also show better results than recycled materials with an unknown resistance origin. Durability test results represent those concretes containing recycled coarse aggregates have lower strength compared to recycled fine aggregates. Also, a series of mathematical relationships for all the responses are presented using variance analysis to predict mixtures' rheological and mechanical properties.

Mineralogical Analysis of Calcium Silicate Cement according to the Mixing Rate of Waste Concrete Powder (폐콘크리트 미분말 치환율에 따른 이산화탄소 반응경화 시멘트의 광물상 분석)

  • Lee, Hyang-Sun;Song, Hun
    • Journal of the Korea Institute of Building Construction
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    • v.24 no.2
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    • pp.181-191
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    • 2024
  • In the realm of cement manufacturing, concerted efforts are underway to mitigate the emission of greenhouse gases. A significant portion, approximately 60%, of these emissions during the cement clinker sintering process is attributed to the decarbonation of limestone, which serves as a fundamental ingredient in cement production. Prompted by these environmental concerns, there is an active pursuit of alternative technologies and admixtures for cement that can substitute for limestone. Concurrently, initiatives are being explored to harness technology within the cement industry for the capture of carbon dioxide from industrial emissions, facilitating its conversion into carbonate minerals via chemical processes. Parallel to these technological advances, economic growth has precipitated a surge in construction activities, culminating in a steady escalation of construction waste, notably waste concrete. This study is anchored in the innovative production of calcium silicate cement clinkers, utilizing finely powdered waste concrete, followed by a thorough analysis of their mineral phases. Through X-ray diffraction(XRD) analysis, it was observed that increasing the substitution level of waste concrete powder and the molar ratio of SiO2 to (CaO+SiO2) leads to a decrease in Belite and γ-Belite, whereas minerals associated with carbonation, such as wollastonite and rankinite, exhibited an upsurge. Furthermore, the formation of gehlenite in cement clinkers, especially at higher substitution levels of waste concrete powder and the aforementioned molar ratio, is attributed to a synthetic reaction with Al2O3 present in the waste concrete powder. Analysis of free-CaO content revealed a decrement with increasing substitution rate of waste concrete powder and the molar ratio of SiO2/(CaO+SiO2). The outcomes of this study substantiate the viability of fabricating calcium silicate cement clinkers employing waste concrete powder.