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] Kovalčíková M. , Eštoková A. Leaching of calcium and silicon from cement composites in the aggressive environment , Pollack Periodica , Vol. 9 , No. 2 , 2014 , pp. 123 – 130 . [13

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This paper presents the results of basic research using sludge as a secondary material produced during the process of wet aggregates grading. The basic objective of this study was to identify important properties of sludge for the further use as substitute filler in the cement composites. Results of tests executed, like determination of particle size, bulk density, chemical composition (XRF method), mineralogical composition (XRD method) and both clay lumps and humus content were compared with those of natural aggregate (reference sample), as well as with standard criteria. For all tested properties, sludge shows satisfactory parameters, except the granularity. Here samples demonstrate high portions of fine particles in the 0/4 range. Thus can be concluded, sludge has a potential to be used as filler in cement composites requiring bigger amounts of fine particles, like self-compacting concretes.

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Eštoková A, Kovalcíková M., Sicáková A. Leaching of calcium and silicon from cement composites in sulphate environment, CEST 2013: Proceedings of the 13th International Conference on Environmental Science and Technology , 5–7 September 2013, Athens, Greece

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Slovakia denoted as kaolin sands [ 33 – 36 ]. The effect of cement substitution by burnt kaolin sand (with 36% of metakaolinite) on hydrated phases, pore structure development and mechanical properties in cement composites was evaluated and relevant

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Abstract  

Methods of thermal analysis are employed in a study of the high-temperature properties of three different types of glass fiber reinforced cement composites together with the measurements of their thermal and hygric parameters. First, basic TG and DTG measurements are carried out to get the first insight into the high-temperature behavior of the analyzed materials. Then, mercury porosimetry and scanning electron microscopy of specimens subjected to the temperatures of 600 and 800C are performed and compared to the reference specimens not exposed to any thermal load. Finally, measurements of thermal and hygric parameters of the studied materials are done and matched with the results of the material characterization experiments. Three main effects are found to influence the thermal and hygric properties of the analyzed materials. The first is the decomposition of the cement matrix, which is clearly a negative factor. The second is the positive effect of the presence of fibers that could partially keep the cement matrix together even after significant decomposition of cement hydration products. The third important factor affecting the thermal and hygric properties is the composition of the particular materials. The application of vermiculite aggregates instead of sand is found to be clearly positive because of its porous character leading to the bulk density decrease without worsening the other properties. Also, wollastonite aggregates are a better choice than sand because of its fibrous character that could partially magnify the effect of fiber reinforcement.

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Abstract  

Thermal conductivity, specific heat capacity, thermal diffusivity and linear thermal expansion coefficient of two types of carbon fiber reinforced cement composites are measured in the temperature range up to 800�C. Thermal conductivity and thermal diffusivity are also determined for the specimens exposed to thermal load up to 800�C before the measurement. Differential thermal analysis (DTA), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) are utilized for the assessment of thermal decomposition processes taking place in the high temperature range under consideration. The high temperature thermal properties of the studied materials are found to be positively affected by the application of the high alumina cement and in the case of the Portland cement based composite also by using the autoclaving procedure in the production process. Also, the randomly distributed carbon fibers that can reduce the damage of the pore structure by the thermal decomposition processes are identified as a positive factor in this respect. A comparison of thermal conductivity vs. temperature curves obtained for the specimens pre-heated to different temperatures is found to be a useful tool in the identification of major dynamic effects in the specimens due to the thermal decomposition reactions. The results are in a good agreement with the DTA, MIP, SEM and XRD analyses. The character of the thermal conductivity measurements that in fact includes the effects of convection and radiation into the thermal conductivity coefficient can be beneficial for a simple assessment of the influence of the fire on a dividing structure.

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Abstract  

Samples of the natural zeolites chabazite, clinoptilolite and a clinoptilolite-rich tuff, were loaded with the isotope 137Cs. Composites of these labeled materials were made with cement and blast furnace slag. Standard leaching experiments were carried out with synthetic sea, ground and "pond" waters, as well as distilled water. Rates of leaching were calculated and compared to similar systems.

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Abstract  

The uptake of137Cs and90Sr/90Y onto Syrian bentonite has been studed, using batch and column tracer techniques in order to investigate its utilization for aqueous radioactive effluent treatment. Parameters influencing the percent uptake considered and studied in this work are: nuclide concentration, pH of the aqueous phase, heat treatment and particle size. Leaching experiments using natural sea and ground waters were carried out on bentonite/cement composites. They demonstrated the effectiveness of calcination and cement containment.

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neuzeitliche Betonbewehrung 1994 Reinhardt H. W, Naaman A. E. (1992), High performance fiber reinforced cement composites

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Composite absorbers of inorganic ion-exchangers and polyacrylonitrile binding matrix

V. Influence of ionising radiation on the leachability of137Cs from cemented composite NiFC-PAN absorber

Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Motl, J. John, and F. Sebesta

Abstract  

Maximum attainable self-absorption dose for cemented composite ion-exchanger, consisting of nickel hexacyanoferrate and polyacrylonitrile binding matrix, loaded with137Cs up to repository acceptable level (1.1·1012 Bq·m–3) was calculated to be 105 Gy. The cemented absorber with sorbed caesium was irradiated by60Co source up to 1 MGy, and leach tests were performed to determine possible influence of self-irradiation on the caesium leachability. No radiation induced changes in caesium immobilisation in solidified ion-exchanger were observed.

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