Ústav technologie stavebních hmot a dílců

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    Optimizing Indoor Microclimate and Thermal Comfort Through Sorptive Active Elements: Stabilizing Humidity for Healthier Living Spaces
    (MDPI, 2024-11-29) Peterková, Jitka; Zach, Jiří; Novák, Vítězslav; Korjenic, Azra; Sulejmanovski, Abdulah; Sesto, Eldira
    This paper investigates the potential use of natural materials and elements for stabilizing indoor humidity levels, focusing on creating healthier living environments in buildings. Unstable indoor microclimates, particularly extreme humidity levels, can negatively affect human health by causing issues such as condensation, mold growth, or dry mucous membranes. In this work, we explore how sorptive materials can maintain indoor humidity within the optimal range of 40-50%. The aim is to identify optimal solutions for moisture control using passive elements, such as unfired ceramic components, which demonstrate high sorption activity within the 35-55% relative humidity range. These elements can effectively absorb moisture from, or release it back into, the indoor environment as needed. Five clay types based on different clay minerals were analyzed in the research in order to assess how their structures influence moisture adsorption behavior. These elements can be combined with green/active elements and standard measures, such as ventilation or targeted room air exchange, to improve indoor humidity regulation. The evaluation of the results so far indicates that the use of clay-based elements in the interior offers a sustainable and natural approach to maintaining optimal indoor microclimate conditions. The slab elements from all 5 clay formulations investigated effectively support indoor humidity stabilization.
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    Utilization of Alternative Fibres Manufactured from Recycled PET Bottles in Concrete Technology for the Improvement of Fire Resistance
    (MDPI, 2024-11-12) Sedlmajer, Martin; Zach, Jiří; Bubeník, Jan; Bydžovský, Jiří; Novák, Vítězslav
    This article addresses the potential use of secondary polymer fibres in the field of structural concrete as a replacement for primary polymer fibres (mainly polypropylene/PP/), which are used in concrete to enhance its resistance when exposed to high temperatures (especially in the case of fire). Research has shown that, in addition to PP fibres, polyethylene terephthalate/PET/fibres, produced by recycling packaging materials (mainly PET bottles), can also be used as an alternative. These fibres are industrially produced in similar dimensions as PP fibres and exhibit similar behaviour when added to fresh and hardened concrete. In terms of their effect on increasing resistance to extreme heat loads, it has been found that despite a higher melting point (Tm), concrete with these fibres demonstrates comparable fire resistance. Therefore, it can be concluded that secondary PET fibres represent an interesting alternative to primary PP fibres from the perspective of a circular economy, and their use in construction represents a potentially valuable application for PET obtained through the collection and recycling of PET packaging materials.
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    Study on the use of glass by-products for sustainable polymer-modified mortars
    (Springer Nature, 2024-11-09) Žižková, Nikol; Hodul, Jakub; Drochytka, Rostislav
    This investigation is focused on the observation of changes in the properties of polymer-modified cement mortars caused by the addition of recycled glass. The current requirements for reducing CO2 emissions in the production of cement composites, are also forcing the producers of polymer-modified mortars (PMMs) to use alternative materials, such as silica-rich supplementary materials. Selected types of recycled glass with pozzolanic behavior were specifically ground (particle size below 63 m) and used as a partial cement substitute (10wt.%, 20wt.% and 30 wt.% substitution of Portland cement). In order to explain the obtained results and garner new knowledge of the microstructure of the mixtures being studied, the following tests were performed: scanning electron microscopy (SEM) observation, differential thermal analysis (DTA) and high-pressure mercury intrusion porosimetry. The findings show that the finely ground recycled glass has high potential to be used as an effective cement replacement for PMM materials, that are currently used in large amounts, mainly in the rehabilitation of concrete structures.
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    Chemically resistant concrete coating systems with secondary raw materials
    (Springer Nature, 2024-11-09) Hodul, Jakub; Drochytka, Rostislav; Žlebek, Tomáš
    New types of highly chemically resistant coating systems, mainly developed for concrete and metal substrates were subject to experimental testing and evaluation within the project. Secondary raw materials, including solidified hazardous waste (neutralization sludge (NS)), were used as microfillers. The three-layer polymer coating systems, applied using spray technology, were tested at two quality levels – one with a high content of solidification products, and the other with a low content. The microstructure of the epoxy coatings, including an observation of the degree of contamination of the polymermatrix,was investigated using scanning electron microscopy (SEM). It was demonstrated that the substitution of some of the primary filler with a solidification product does not result in the deterioration of the properties of the coating system, such as its adhesion to concrete or chemical resistance.
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    Utilisation of hydrophobic agents for water-repellent cement screeds intended for external thermal insulation composite systems
    (Springer Nature, 2024-11-09) Hodul, Jakub; Mészárosová, Lenka; Žižková, Nikol
    The paper discusses the possibilities of hydrophobization of cement screeds intended primarily for external thermal insulation composite systems. The hydrophobic character of the mixtures both with and without the addition of hydrophobic agents was investigated. The following hydrophobic agents were used: zinc and magnesium stearate, sodium oleate, two types of mixed product of stearates and oleates, micronized wax and a silane hydrophobic agent. The mixture containing 0.6% zinc stearate and 0.6% silane showed the lowest water absorption and high flexural and compressive strength. The microstructure of the selected mixtures was also monitored using a scanning electron microscope,where the pores covered with the layer of polymer admixture were observed.