Synthesized tobermorite

The carbonation effect on synthesized tobermorite has been examined by XRD / DTA.I ] An endothermal effect at about 180°C indicated the dehydration of tobermorite and an exothermal effect at about 800°C was caused by the formation of wollastonite. The carbonated samples exhibited a broad endothermal effect in the range of 450-600°C and a sharp peak at about 600-650°C. The former indicated the presence of vaterite and the latter, calcite. The carbonation decreased the peak due to wollastonite. Thermal methods can also be used to estimate the amount of carbonation that has occurred at different depths in concrete. These techniques estimate the amount of calcium carbonate formed and also the amount of calcium hydroxide remaining in an uncarbonated form. 

The C-S-H-type phases formed in these experiments are highly aluminous (8-24 mol%), suggesting Al for Si substitution from 19 to 37 mol% - significantly more than has been recorded for crystalline C-S-Hs such as tober-morite (e.g. Kalousek 1957 Komarneni et al. 1982, who synthesized tobermorites with up to 20% Al for Si substitution). The product of the muscovite experiments contains so much Al that it lies almost within the zeolite compositional field. 

Diamond,S.,White,J.L. and Dolch,W.L., Effects of isomorphous substitution in hydrothermal-synthesized tobermorite, Amer. Mineral.,1966,51,pp.388-401. 

Attempts to synthesize 1.4-nm tobermorite or jennite from aqueous suspensions at ordinary temperatures normally yield semicrystalline products. 

Calcium hydrosilicates compose a wide range of different compounds [26], One of them is tobermorite, Cas(0H)2Si60i5-4H20. It is an important material, since it has brilliant physicochemical properties, for example low density 0.5 g/cm, good ion exchange characteristics. In [27], tobermorite was synthesized by mechanical activation of a mixture of calcium hydroxide and silica in the presence of water at room temperature ... 

It was stated that weakly crystallized tobermorite was synthesized in a mixture of calcium hydroxide and silica gel. The reaction is most efficient at the reagent ratio CaO Si02=5/6 and water-to-solid ratio 4 1. At short activation time, the formation of poor crystallized calcium silicates of B type with tobermorite-like structure was observed, Mechanochemically obtained tobermorite is stable till 800°C. Above this temperature, it... 

The Tobermorite-like CSH samples were synthesized in hydrothermal conditions an aqueous reaction between CaO and silicic acid with different Ca/Si ratios. CaO was calcinated from CaCOs at 1100°C while silicic acid was calcinated at 150°C for 2 hours in order to remove adsorbed vapours. The water/solid ratio was fixed at 20. Plastic bottles containing the samples were placed in autoclave at 60°C with a permanent rotation system for 100 days. The samples were then rinsed with pure water and stored at 30% of relative humidity. Here, we report results for synthetic Tobermorite material with Ca/Si=0.9. 

Bonding occurs when fly ash and lime are hydrothermally treated. The products formed in such mixtures are advantageously identified by DTA. Thermal analysis indicates that initially C-S-H (I) forms and is then converted to 11 A tobermorite. Carbonation also can be followed by DTA. By a hydrothermal process, a cementing material was synthesized from a mixture of fly ash, lime, and water. The resulting product was analyzed by DTA, TG, and XRD.l l... 

With a CaO/SiO ratio of 0.5, the products were tobermorite gel, hydrogarnet and y-AlO(OH), and also anhydrite appeared with the CaSO 2H20 addition. With a CaO/SiO ratio of 1.0, the products were tobermorite gel, tobermorite solid solution, CSH(I), xonotlite, hydrogarnet and T-A10(0H). With a CaO/SiO ratio of 2.0, por t landi te, c L.or -C2Shydrate, xonotlite and tobermorite solid solution were synthesized. 

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