Current knowledge of geopolymers and AAMs network

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EFFECT OF FORMING PRESSURE ON THE REACTIVITY AND MICROSTRUCTURE OF ZIRCON POWDER COMPACTS

Preliminary results of a study on the effects of the forming pressure on the reactivity, sintering and microstructure of very fine natural zircon powder compacts. The effects of compaction pressure on the green densities and sintered densities are also discussed. The relationship between the density and the compaction pressure governs the mechanism that occurs in the consolidation process. The investigation has demonstrated changing the compaction pressure in the range 45-180MPa does not influence the onset temperature of sintering of powdered zircon (1150-1170 °C) but does influence the apparent density of the green compacts and consequently the porosity of the sintered specimens. Low relative density values were obtained in these sintering conditions

Alkali activation for management of construction and demolition wastes coming from earthquake

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Addition of WEEE glass to metakaolin based geopolymeric binder: a cytotoxicity study

Waste Electrical and Electronic Equipment (WEEE) types of glass, including Cathode Ray Tube (CRT) glass, are now separately collected in European Union 28 (EU28) zone. Due to the high level of Pb and Ba in their compositions, this type of waste finds its way to the disposal. In the present research, a geopolymer matrix based on metakaolin is used to blend in fine powder panel and funnel glass from personal computer (PC) and television (TV) monitors. Such waste glass, which cannot be directed to glass melting furnaces, is safely incorporated into a geopolymer matrix. The consolidation of the geopolymeric matrix containing the waste glass was followed by pH and conductibility up to 28 days of curing. Scanning electron microscope equipped with energy dispersive spectroscopy (SEM/EDS) was used to obtain information on the microstructure of the consolidated products. Cytotoxicity tests helped the environmental evaluation of these materials

Cork powdery industrial waste in metakaolin–geopolymer matrix

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Acid attacks on metakaolin based-geopolymers with recycled corundum: A study focused on the role of anions by NMR characterization

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Materie prime di origine naturale nel processo di geopolimerizzazione

Geopolymers are inorganic materials prepared via a room temperature treatment (25-120?C) with alkali activation. The main applications of these materials is in the field of building materials, recycle and inertization of waste, restoration. The production and final product is optimised by a careful selection of starting materials, i.e. aluminosilicate powders. In this paper are presented aluminosilicates from natural source, as an example kaolin, clays or volcanic ash. Metakaolin is the most reactive due to its amorphous structure and aluminium coordination; its reactivity is also influenced by its mineralogical origin, morphology of grains, and calcinations method. Volcanic ash present lower reactivity and the better consolidation temperature to obtain mechanically strong materials appears to be around 400?CI materiali geopolimerici sono materiali inorganici ottenuti con consolidamento a bassa temperatura (25-120?C) mediante una reazione chimica in ambiente alcalino. Sono utilizzati per applicazioni ad alta temperatura e strutturali in edilizia, per il riciclo e /o l?inertizzazione di scorie industriali, per il restauro. L?opportuna selezione di materie prime alluminosilicatiche ? alla base dell?ottimizzazione del ciclo produttivo e del prodotto finale. Vengono presentate materie prime di origine naturale, quali il metacaolino, derivato dalla calcinazione del caolino, e le ceneri vulcaniche. Il metacaolino ? la materia prima pi? reattiva grazie alla struttura amorfa e alla coordinazione dell?alluminio: sulla reattivit? influiscono sia la morfologia e le caratteristiche del caolino di origine, sia la metodologia di calcinazione. Le ceneri vulcaniche hanno una minore reattivit? che pu? esser ovviata tramite un consolidamento a circa 400?C portando a prodotti geopolimerici con buone prestazioni meccanich

Efficient Addition of Waste Glass in MK-Based Geopolymers: Microstructure, Antibacterial and Cytotoxicity Investigation

Reuse of waste glass can significantly decrease the quantity of waste to be treated or disposed of in landfills, allowing to both diminish the ecological damage and to reduce the costs of transportation for removal. Geopolymer mixes with diverse percentages (20, 50 and 60 wt%) and with different grain size ranges (37 µm < diam < 53 µm; 75 µm < diam < 105 µm) of waste glass and the residual part of pure metakaolin were prepared by addition of NaOH and sodium silicate as alkaline activator solutions. The effect of waste glass on the mechanical and microstructure of new geopolymers has been explored in this study. Fourier transform infrared spectroscopy (FTIR) evidenced the reactivity of waste glass in terms of Si–O and Si–O–Al bonds, more evident for the finer waste glass powder. The consolidation of the materials has been established by reduced weight loss in water and decreased pH and ionic conductivity of the eluate after 7, 14 and 28 days of curing at room temperature. The decrease of the mechanical properties with waste glass content was less evident for the finer glassy powders, yet the value of about 4-5 MPa indicates their potential use as non-structural materials. The consolidated final materials were tested for their effects on the microbial growth of Escherichia coli and Enterococcus faecalis after 24 and 48 h, respectively. The samples showed a very limited and absent inhibition zone, for fine and coarse grain size ranges, respectively. Finally, the cytotoxicity tests accomplished the ecological valuation of the final consolidated products

Effects of nucleating agents on diopside crystallization in new glass-ceramics for tile-glaze application

The effect of crystallization produced by addition of TiO2, ZrO2 and P2O5 oxides to glass-ceramic of the system CaO-MgO-SiO2 was studied using structural and thermal techniques. The devitrification process was independent of thermal treatment. X-ray diffraction studies performed on the glass-ceramic system indicated that diopside crystalline phase was more thermodynamically favourable than other phases. The effect of the nucleating agent depends on its nature: TiO2 decreased the activation energy while P2O5 and ZrO2 did not. SEM analysis of the doped glass-ceramics showed randomly distributed crystals with significant dimensional variations from those of the undoped system. All these formulations, showing a high crystallization rate, and a fast heating rate, can be used as tile glazes and/or tile-glaze components