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Abstract  

The influence of spent catalyst from catalytic cracking in fluidized bed on the hydration process of cement and the properties of cement mortars were studied. The spent catalyst was used as an additive to cement in the mortars (10 and 20% of cement). The samples of mortars kept in water for28 days, then they were placed in sulfate and chloride media for 2 months (the control samples were kept in water for 3 months). After this time they were subjected to bending strength and compressive strength determinations. Thermogravimetric and infrared absorption studies were performed and capillary elevation, capability of binding heavy metals, and changes in mass and apparent density were determined too. The studies disclosed the pozzolana nature of spent catalyst and its influence on cement mortars being in contact with corrosive media.

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Abstract  

The chemical corrosion and the mechanical strength were studied in cement mortars containing an additive of FBCC under conditions of long-term action of sodium sulphate solution or saturated brine. The observations have shown that saturated brine is a more aggressive agent, since it leaches Ca(OH)2 and contributes to the decomposition of the C-S-H phase thus worsening the compressive strength as compared with that of mortars kept in water. The addition of 20% FBCC inhibits the leaching process and counteracts the decrease of compressive strength in mortars kept in brine. On the other hand, sodium sulphate solution changes favourably the mortar microstructure, increases of the content of small pores and improves both the compressive and the flexural strengths, as compared with those of a mortar kept in water.

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Abstract  

The dried blends containing sodium and ammonium salts of lignite humic acids (humates, 0.5–10% w/w) in polyvinyl alcohol (PVA) were exposed to high dosage of γ-irradiation in the range of doses 127–806 kGy. Resulted products were then tested for their stability using thermogravimetrical analysis. As a reference the non-treated blends were used since the pure PVA exposed to γ-irradiation very quickly lost its stability and resulting consistence did not allow the stability tests. Stabilities showed a strong concentration and counterion dependency. While sodium counterion caused mostly destabilization with increasing dose, the ammonium counterion acted in an opposite way. The tests carried out in a moisturizing container revealed the changes in water absorbing capacity of irradiated samples and allowed partial explanation of humate stabilizing effect. Generally, at lower concentration of a humate the increase was observed with an increase in the γ-irradiation dose and vice versa. The results confirmed the antioxidant and stabilizing effect of humic acids added to some synthetic polymers and their applicability in materials exposed to γ-irradiation.

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Introduction Reactive elements, especially rare earths (RE) have been used to improve high-temperature oxidation resistance of chromium dioxide and alumina forming alloys. The improvements are in the form of reduced oxidation

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to specific antibodies and the selective lysis of the immobilised bacteria. A more straight way to detect bacterial resistance towards growth inhibiting agents is the measurement of the decrease of the metabolic heat production as an effect of

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carried out extensive studies on the APP IFR system in polyolefins [ 2 , 4 , 5 ] and have reviewed recent developments of IFR systems in great detail [ 11 ]. However, these systems are not durable due to the weak water resistance and low compatibility

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