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RISS 인기검색어
- 검색키워드
- 저자 : Nailia R. Rakhimova (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Calcined low-grade multimineral clays as supplementary cementitious materials: a feasibility study
Rakhimova Nailia R.,Rakhimov Ravil Z.,Bikmukhametov Artur R.,Morozov Vladimir P.,Eskin Aleksey A.,Gubaidullina Alfiya M. 한국자원공학회 2020 Geosystem engineering Vol.23 No.3
The relevance of calcined clays as sources with great potential for low-clinker blended Portland cements has significantly increased in recent decades. This article reports on a study to evaluate the potential of the two low-grade clays containing 9.37% of montmorillonite/chlorite and 12.26% of montmorillonite/kaolinite/chlorite accompanied with 29.73% and 32.79% of calcite, respectively, as supplementary cementitious materials. The clays after thermal treatment at 800°C demonstrated poor pozzolanic activity, slight increase in the C-(S)-H and decline in the CH contents, and decrease in the mechanical properties of the blended Portland cement pastes. The results showed that the investigated clays fall below the range of the clays suitable for pozzolan production.
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A review of calcined clays and ceramic wastes as sources for alkali-activated materials
Nailia R. Rakhimova 한국자원공학회 2020 Geosystem engineering Vol.23 No.5
Expanding and optimising the raw materials base in accordance with increasing ecological and technical requirements is one of the determining factors of a promising future for the constantly evolving alkali-activated materials (AAMs). Because of the development of the chemistry of the inorganic materials, the range of potentially suitable aluminosilicates has changed and expanded continuously throughout the history of AAMs. Relatively recently, efforts to find more types of adequate, alternative aluminosilicate sources, in addition to conventional granulated blast furnace slag, fly ash, and metakaolin, have led to extensive studies that have substantially increased understanding around the suitability of various natural sources and wastes for production of AAMs. In recent decades, calcined clays and ceramic wastes have become significant as an alumino-silicate sources for AAMs. Extensive research forms the theoretical and practical bases for the application of calcined clays, which are diverse in composition and structure, for effective cement production. This paper reviews recent developments in the field of alkali-activated cement-based systems using calcined clays containing different amounts of 1:1 and/or 2:1 type clay and secondary minerals, and ceramic wastes, including their suitability aspects, processing features, chemical reactivities, controlling factors, potential for application.
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Influence of calcined medium grade clay on the properties of Portland cement pastes
Rakhimova Nailia R.,Morozov Vladimir P.,Eskin Aleksey A. 한국자원공학회 2022 Geosystem engineering Vol.25 No.6
In the recent decades, the composition of Portland cements has undergone significant changes related to an increase in the range and content of supplementary cementitious materials following development of composite and multicomposite cements. The development of these binders that meet the requirements of sustainability requires the expansion and adaptation of the mineral resource base of cement industry to the production of low-emission binders with a gradual decrease of resource and energy intensities. Efforts to find the widespread sources of pozzolans providing high reactivity and physical–chemical stability have led to intensive studies on thermally treated clays of various chemical–mineralogical composition and their industrial adoption. Due to scarcity and high cost of kaolin clays, great attention is given to medium- and low-grade clays. This article reports on a study to evaluate the effect of calcined clay with 52% of clay minerals on the properties of fresh and hardened pastes, in particular on the resistance to sodium sulfate and nitric acid attacks. The reaction products assemblage of the blended Portland cement pastes was investigated by XRD and thermal analyses. The hardened Portland cement pastes incorporated with thermally treated clay demonstrated better durability performance compared to reference ones.
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Rakhimova Nailia R.,Morozov Vladimir P.,Eskin Aleksey A. 한국자원공학회 2021 Geosystem engineering Vol.24 No.5
The relevance of calcined clays as sources with a great potential for non-clinker alkali-activated materials has significantly increased in recent decades. This article reports on a study to investigate how NaOH with concentrations in the 5–14 M range affects the mechanical properties, amorphouscrystalline phase transformations, and reaction product composition of alkali-activated calcined kaolinite/montmorillonite cements with reactive phases of 60% and 33%, and with the SiO2/Al2O3 ratios of 1.54 and 1.74. The hardened pastes based on both calcined clays exhibited the highest compressive strength up to 9.1 MPa following their activation with 8 M NaOH. The higher amorphous fraction in the calcined clay provided gradual zeolitisation/crystallisation at Na2O/ SiO2 and Na2O/Al2O3 molar ratios in the 0.36–0.63 and 0.56–0.98 ranges, respectively, accompanied by the deterioration of the mechanical characteristics of the samples. The zeolite content in the alkali-activated calcined clay cements with an amorphous fraction of 33% peaked for NaOH at 11 M, and the corresponding molar ratios of Na2O/SiO2 and Na2O/Al2O3 were 0.85 and 1.46, respectively. The main reaction products in the studied systems determined by XRD, TG/DSC, and FTIR spectroscopy analyses were N-A-S-H and zeolite A. The properties and reaction products obtained favor the use of proposed alkali-activated cements for controlled low-strength materials.
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Properties of Portland cement paste incorporated with loamy clay
Ravil Z. Rakhimov,Nailia R. Rakhimova,Albert R. Gaifullin,Vladimir P. Morozov 한국자원공학회 2017 Geosystem engineering Vol.20 No.6
Metakaolin which is calcined kaolin clay is being widely applied as supplementary cementitious materials for Portland cement. Due to their scarcity and high cost, calcined ubiquitous polymineral clays are actively studied as alternative to metakaolin. This article presents the study results of influence of calcined ground loamy clay on the properties of Portland cement paste. About 5–15% of loamy clay calcined at 400–600 °C and ground to 250–500 m2/kg were found to be more effective compared to metakaolin of specific surface area of 1200 m2/kg for improvement of compressive strength, water resistance, and increase in density of hardened Portland cement paste.
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