Wyniki wyszukiwania - BazTech

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Mikrostruktura i właściwości geopolimerów powstających w procesie alkalicznej aktywacji popiołu lotnego

Rajczyk Krystyna, Janus Grzegorz

Cement Wapno Beton

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2021

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R. 26, nr 4

279--293

PL

W pracy przedstawiono wyniki badań możliwości otrzymania trwałego betonu geopolimerowego o dużej wytrzymałości, którego podstawowym składnikiem jest popiół lotny. W wyniku przeprowadzonych badań ustalono, że największą możliwość uzyskania betonu geopolimerowego o dużej wytrzymałości wykazały drobnoziarniste, specjalnie wyselekcjonowane popioły krzemionkowe ze spalania węgla kamiennego, nazywane ultra drobnymi popiołami. Jednak beton geopolimerowy, otrzymany przez alkaliczną aktywację tych popiołów 8M roztworem NaOH, nie jest odporny na cykliczne zamrażanie i rozmrażanie. Zastąpienie 15% popiołu lotnego prażoną odpadową gliną oraz stosowanie aktywatora, stanowiącego mieszaninę roztworu NaOH i szkła wodnego, znacznie zwiększyły trwałość tego betonu. Ta modyfikacja składu betonu wpłynęła na zmianę mikrostruktury matrycy w betonie, w której między innymi stwierdzono w badaniach, występowanie krystalicznego kankrynitu.

EN

The paper presents the results of the study on the possibility of obtaining high-strength durable geopolymer concrete with fly ash as the basic component. As a result of the research conducted, it was found that the highest potential to obtain geopolymer concrete with high strength was shown for fine-grained, specially selected siliceous ashes from coal combustion. However, the geopolymer concrete obtained by alkaline activation of these ashes with the 8M NaOH solution was not resistant to freeze-thaw cycles. Replacement of 15% fly ash with calcined waste clay and the use of the mixture of NaOH solution and water glass as an activator substantially increased the durability of this concrete. This modification of the concrete composition changed the microstructure of the matrix in the hardened concrete, since the cancrinite was found in the study.

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Hydrothermal synthesis of zeolites from green container glass

Maisuria Jenika, Elmes Victoria K., Hurt Andrew P., Coleman Aimee A., Coleman Nichola J.

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 5

784--796

EN

Landfilling and stockpiling unrecycled colored container glass represents a considerable failure in sustainability with respect to the conservation of energy and mineral resources. In this study, the single-step hydrothermal synthesis of low-silica zeolites from a mixture of waste green container glass and aluminum foil (Al:Si = 1) in 4 M NaOH(aq) at 125 °C was followed at 1, 3, 7 and 14 days. The principal phases, sodalite and cancrinite, appeared within 1 day accompanied by minor quantities of hydrogarnet and tobermorite arising from a stoichiometric excess of calcium ions in the parent glass. Products of 63, 67, 71 and 72% crystallinity were obtained at 1, 3, 7 and 14 days, respectively, with partial successive conversion of sodalite to cancrinite over time. Ion-exchange and catalytic applications of sodalite and cancrinite arise from the high anionic charge of the 1:1 ratio of alternating SiO44- and AlO45units within their aluminosilicate frameworks. In this respect, the uptake capacity of the 14-day zeolitic product for Cu2+ and Cd2+ ions (1.58 meq g-1 and 1.66 meq g-1, respectively) was within the expected range for zeolites and compared favorably with those reported for other inorganic sorbents derived from industrial and municipal wastes. The 14-day product was also found to be an effective basic heterogeneous catalyst for the Knoevenagel condensation reaction.

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Indicative significance of water environment in zeolitic structure - a study using experimentally grown cancrinite and analcime

Słaby E.

Acta Geologica Polonica

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1999

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Vol. 49, no. 1

25-65

EN

Cancrinite and analcime were synthesized in the two hydrothermal systems: acid plagioclase - Na2CO3 - H2O and basic plagioclase - Na2CO3 - H2O under widely varying temperatures and salt concentrations in the solution. The IR 1^H MAS NMR DTG/TG analyses were carried out to determine water position in the crystals. Additionally IR spectra were recorded during subsequent dehydration and rehydration processes. The results of the investigations indicate that the water environment in both minerals is sensitive to the conditions of crystal formation. Crystallization temperature is the most important factor influencing water position. The water sites in the analcime and cancrinite crystals depend on structure modifications. Variations of the structure result from different chemical composition of the source material, structure of the substrates and the salt concentration in the solution. The structures formed under lower temperatures incorporate more water than those formed at high temperatures. In the cancrinite and analcime two main types of water, H2O(I) and H2O(II) appear. Other OH[m] groups can also be recognized. The position of water H2O(II) is better defined than that of H2O(I). H2O(II)is the most sensitive indicator of thermal conditions of the formation of cancrinite as well analcime. The amount of H2O(II) equals thatof H2O(I) in the products of low temperature (300 stopni C) syntheses. In crystals synthesized at high temperature (550 stopni C) the presence of H2)(II) is very limited.