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    Immobilization of Heavy Metals in Natural Zeolite-blended Cement Pastes
    (Elsevier, 2016-09-26) Vyšvařil, Martin; Bayer, Patrik
    This paper deals with the investigation of efficiency of natural zeolite-blended cement pastes for the immobilization of heavy metals. Natural zeolite was used to partially replace ordinary Portland cement (OPC) at rates of 0% and 20% by weight of a binder and soluble heavy metal salts were added to a mixing water in an amount of 1% and 5% by weight of the binder. The flexural and compressive strength of the cement pastes were investigated, while the leachability of the heavy metals was determined. Additionally, scanning electron microscopy was performed to investigate the microstructure of the cement pastes, while the pore size distribution was analyzed with mercury intrusion porosimetry. The results indicated that the flexural and compressive strengths of the pastes containing 20 wt.% of natural zeolite were higher than those with OPC alone. It was also found out that the effectiveness in reducing the leachability of Ba, Cd, Cu, Ni and Pb was better for the natural zeolite-blended cement pastes.
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    Electrical and Self-Sensing Properties of Alkali-Activated Slag Composite with Graphite Filler
    (MDPI, 2019-05-16) Rovnaník, Pavel; Kusák, Ivo; Bayer, Patrik; Schmid, Pavel; Fiala, Lukáš
    The electrical properties of concrete are gaining their importance for the application in building construction. In this study, graphite powder was added to alkali-activated slag mortar as an electrically conductive filler in order to enhance the mortar’s conductive properties. The amount of graphite ranged from 1% to 30% of the slag mass. The effect of the graphite powder on the resistivity, capacitance, mechanical properties, and microstructure of the composite was investigated. Selected mixtures were then used for the testing of self-sensing properties under compressive loading. The results show that the addition of an amount of graphite equal to up to 10% of the slag mass improved the electrical properties of the alkali-activated slag. Higher amounts of filler did not provide any further improvement in electrical properties at lower AC frequencies but caused a strong deterioration in mechanical properties. The best self-sensing properties were achieved for the mixture with 10wt% of graphite, but only at low compressive stresses of up to 6 MPa.
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    Variability in cement properties - influence on bleeding of cement paste
    (IOP Publishing, 2018-06-15) Jančaříková, Denisa; Hela, Rudolf; Netsvet, Daria Dmitrievna; Peřina, Tomáš
    The aim of this study is to find relation between cement properties and tendency of cement paste (concrete) to bleeding. We tested 19 cement samples collected from different batches.
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    The mechanical activation of fly ash
    (Elsevier, 2013-09-03) Hela, Rudolf; Jančaříková, Denisa
    One of the main options in looking for the new building materials is using of wastes from an industry as a replacement of the existing ingredient. This way is used in the concrete production too. Basic effort is to find a suitable replacement for economically and ecologically unfavorable cement by another component or components. As one of these components can be used fly ash – by-product of coal-fired electric power stations. The using of the fly ash as an additive into concrete is quite old, nevertheless this component offers a lot of new possibilities today too. Mechanical activation is one of them. As mechanical activation is known sorting or grinding of fly ash. Activation by sorting brings some disadvantages as is not using of all production and the high price for rebuilding the plants. Much more effective option provides grinding of the fly ash. This practice also comes to Czech Republic and submitted publication summarizes existing knowledge and presents result from first tests done on Czech fly ashes.
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    Development of Vacuum Insulation Panels with Utilization of Organic By-Products
    (MDPI, 2020-03-04) Zach, Jiří; Novák, Vítězslav; Peterková, Jitka; Bubeník, Jan
    The need for the development of new, advanced building materials increases every year, especially due to the necessary diminution of energy performance for building structures and for building production itself (including the production of building materials). Along with the energy performance problems in construction, the issue of CO2 emission associated with building and the production of building materials is also important. In the field of advanced thermal insulation materials, vacuum insulation panels (VIPs) give the best results. However, their high-energy performance and material consumption present a problem. This work represents an initial part of the development of alternative insulators, based on agricultural and textile industry waste usable in the production of VIP. This article recapitulates basic knowledge regarding key thermal insulation properties of developed insulators and their fire reactions, which impact possible usage in building structures