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Abstract  

The effect of calcium hydroxide (CH) on the properties of Portland–fly ash cement pastes, at up to high-volume fly ash mixes has been investigated using normal consistency, setting time, compressive strength, thermal analysis and scanning electron microscope. CH as an additive material (5 and 10 wt%), lignite fly ash (FA) up to 50 wt% was used to produce Portland cement (PC)–FA–CH pastes at w/PC + FA ratio of 0.5. Water requirement for normal consistency was found to increase with increasing CH content while a decrease in initial setting time was found. Furthermore, the compressive strengths of all FA mixes with CH were found to be higher than the mixes without CH. Thermal analysis and scanning electron microscope were used to study the hydration of PC–FA–CH system. The results showed that the first phase transition detected by thermal analyses was attributed to ettringite, calcium silicate hydrate, gehlenite hydrate and was found to be higher in PC–FA–CH mixes than in pure Portland–FA cement paste resulting in an increase in compressive strength. Moreover, the hydration phases were also found to increase with increasing curing time. Overall, the results show that the additional of 5 wt% CH in Portland–FA mixes especially at high-volume FA mixes was found to accelerate FA pozzolanic reaction at early ages (7 and 28 days), resulting to an increase in compressive strength.

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Összefoglalás

Kutatásaink során eltérő őszi búzafajták lisztjéből készült kenyerek sütőipari tulajdonságait vizsgáltuk. A búzalisztet 30%-ban helyettesítettük tritikáléliszttel, adalékanyagként guart és szejtánt alkalmaztunk. Mértük a kenyerek magasságát, sütési és száraz tömegét, elbíráltuk ízét.

Eredményeink alapján megállapítható, hogy az adalékanyagok a kenyérmagasságot és a kenyér száraz tömegét növelték, míg a sütési tömegre nem voltak hatással (98,72–103,23%). A kenyér magasságnál a szejtán hatása kifejezettebb. A száraz kenyértömeg esetében két fajtánál (Mező, Hajdúság) a szejtán, kettőnél (Árkus, Rárós) pedig a guar bizonyult hatásosabbnak.

A kenyerek között ízhatásban lényegi eltérést nem tapasztaltunk, az adalékanyagok használata az ízre nem volt kifejezett hatással. Az eredmények is azt mutatják, hogy az alkalmazott adalék anyagok alkalmasak a lisztkeverékből készült kenyér tetszetős megjelenésének fokozására.

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Summary  

The paper deals with the impact of nuclear plants and radioactive waste disposal on surface and ground water quality in their vicinity using various radiometric and radioanalytical methods. The impact of nuclear power plant Temelin on activation concentrations and fission products in hydrosphere, including tritium, was detected. The annual average tritium concentrations in Vltava River correspond to the previously calculated estimates for average and minimal quaranteed flow rates. The concentrations histories of 90Sr and 137Cs in surface water show a decreasing trend. This trend was not influenced by the nuclear power plant pilot operation. In the case of tritium, a concentration increase trend has been already observed since the startup of pilot operation. An attempt has made interpreting the sorption and diffusion data for radionuclides of cesium, strontium and tritium and technetium as representatives of multivalent elements. Sorption and diffusion data of 137Cs and 90Sr in contact with natural sorbent bentonite lead to the conclusion that both diffusion and batch sorption experiments can be simulated by an exchange model. Sorption of technetium on various bentonites plus additives materials is described. Retention of technetium on these solid phases is driven by sorption of reduced form of technetium Tc(IV).

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Abstract  

Powellite (calcium molybdate) is an essential industrial product used as additive material to steel and for smelting of ferromolybdenum. Powellite often occurs as a secondary mineral and as pseudomorph after molybdenite in the oxidation zone of molybdenite deposits. The present work reports a thermal analysis study of synthesis of powellite by sintering of molybdite (molybdenium oxide) with calcite or calcium oxide using a derivatograph. The reaction products were identified microscopically and by using a Siemens Crystalloflex diffractometer. The DTA curve of sintering of molybdite with calcite shows the beginning of the reaction at 480C with the formation of powellite. The intensive formation of powellite is represented by the medium and wide endothermic peak at 630C. This is followed by a small endothermic peak at 790C, representing the melting of unreacted molybdite. This is followed directly by large and sharp endothermic peak at 880C, representing the dissociation of unreacted calcite. The wide and large endothermic peak at 1155C represents the boiling of unreacted molybdite with appreciable vaporization. The DTA curve of sintering of molybdite with calcium oxide shows a medium and wide endothermic peak at 525C representing the intensive formation of powellite and also the dehydration of calcium oxide. The small endothermic peak at 730C represents the loss of carbon dioxide due to some carbonatization of calcium oxide with carbon dioxide from air. The medium endothermic at 790C represents the melting of unreacted molybdite. The produced powellite is yellow in thin sections, has indistinct cleavage, crystallizes in the tetragonal system in the form of tabular crystals and is optically positive.

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Abstract  

Thermoplastic masterbatches are a complex blend of the base thermoplastic resin, a pigment and a range of additive materials. End use applications of masterbatches include agricultural film, packaging film, injection moulding of small and large bottles, boxes and crates and extrusion of pipe and sheet. Thermal analysis is a very useful tool for the characterisation of the physical properties of both masterbatches and finished product. This report will show the use of differential scanning calorimetry (DSC) to identify the melt profiles of masterbatches and to determine oxidative stability. Thermogravimetric analysis (TG) is very useful for the determination of the composition of masterbatches, for the study of batch to batch variability and for a comparison of a material with competitive products. The use of High Resolution TGA (Hi-Res TGA) will be shown to give greater resolution between overlapping weight loss steps leading to better quantification of components within the masterbatch when compared to conventional TG.

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expansive binder and expansive sinter only were used to evaluate the content of ettringite. Taking into account the calcium hydroxide content and assuming that the rest of CaO entered the ettringite phase, the approximate percentage of initial additive

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benzoate, and potassium sorbate to assess the proliferative and apoptotic impacts of these food additives. Materials and Methods Substance tested and their characteristics Tartrazine (Sigma-Aldrich, Hungary

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-silica fume pastes are given in Table 2 . Fly ash was used as a Portland cement replacement at 10, 20 and 30 wt% to produce Portland-fly ash cement and silica fume was used as an additive material which was added at 5 and 10 wt% to Portland-fly ash cement

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