Ústav technologie stavebních hmot a dílců

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Formation, Stability, and Crystallinity of Various Tricalcium Aluminate Polymorphs
(MDPI, 2024-02-03) Ravaszová, Simona; Dvořák, Karel; Boháč, Martin; Všianský, Dalibor; Jančíková, Andrea
Tricalcium aluminate is an important phase of Portland clinker. In this paper, three polymorphs of C3A were prepared by means of the solid-state synthesis method using intensive milling of the raw material mixture which was doped with various amounts of Na2O and sintered at a temperature of 1300 °C for 2 h. The final products were evaluated through X-ray diffraction using Rietveld analysis. The effect of the Na dopant content on the change in the crystalline structure of tricalcium aluminate was studied. It was proven that the given preparation procedure, which differed from other studies, was close to the real conditions of the formation of Portland clinker, and it was possible to prepare a mixture of different polymorphs of calcium aluminate. Fundamental changes in the crystal structure occurred in the range of 3–4% Na, when the cubic structure changes to orthorhombic. At a dosage of Na dopant above 4%, the orthorhombic structure changes to a monoclinic structure. There are no clearly defined boundaries for the existence of individual C3A phases; these phases arise at the same time and overlap each other in the areas of their formation at different Na doses.
Comparison of Trenchless and Excavation Technologies in the Restoration of a Sewage Network and Their Carbon Footprints
(MDPI, 2024-01-15) Chorazy, Tomáš; Hlavínek, Petr; Raček, Jakub; Pietrucha-Urbanik, Katarzyna; Tchórzewska-Cieślak, Barbara; Keprdová, Šárka; Dufek, Zdeněk
The restoration of aging sewer networks is a fundamental remediation approach with the aim of renewing or improving existing systems. Remediation methods include repair, renovation, and replacement (renewal). The restoration of a sewer network itself can be performed using either excavation or trenchless technologies. While these technologies offer various advantages, they also present disadvantages. The choice of a restoration technology depends on numerous parameters, including economic factors and local conditions (such as the construction of the existing sewage network, available working space, traffic load, and environmental safety restrictions). In addition to the parameters influencing the choice of restoration technology, recent considerations have been given to constraints related to greenhouse gas emissions and the corresponding carbon footprint. Carbon footprint serves as an indicator of the restoration activity’s dependence on fossil fuels, both during implementation and operation. In the 21st century, concerns regarding carbon footprints have rapidly escalated. The reduction in carbon footprints is a crucial objective from both an economic and an ecological point of view. This article specifically addresses the prospects of monitoring the carbon footprint concerning the partial restoration of a sewer network within the historical core of the city of Brno, located in the Czech Republic.
Vacuum insulation panels: An overview of research literature with an emphasis on environmental and economic studies for building applications
(ELSEVIER, 2024-01-01) Božiček, David; Peterková, Jitka; Zach, Jiří; Košir, Mitja
The study provides an overview of the research focus on vacuum insulation panels (VIPs). Scientific literature published between 1960 and 2022 is identified, and a database covering 423 documents is amassed. In the first phase, research documents were categorised into three groups: product, other and buildings. In the second phase, data about the studied building applications and research topics were extracted and quantitatively evaluated. In the last phase, the studies evaluating VIPs' environmental and economic implications in buildings were analysed in detail. The study results show an increasing publication trend on VIPs, with almost 90% of the literature published from 2010 onwards. Building applications are the dominant research subject, representing 56% of identified documents. A detailed analysis of life cycle studies pointed to a consensus that in building applications, fumed silica VIPs exert a higher environmental impact and costs than conventional insulation materials if the comparison is based on an equivalent thermal transmittance value. However, several studies showed reasonable payback and environmental neutrality periods for retrofitting scenarios. Benefits could also be achieved if insulation layer thickness is limited. External wall insulation represents the vast majority of the applications analysed. Studies further showed that VIPs in external wall applications could be economically viable compared to conventional insulation if added useable floor space is considered. The characteristics of life cycle studies were analysed, research gaps and possibilities were identified, and research recommendations for environmental and economic studies of VIPs were provided.
Development of a Hydrophobic Polymer Coating in Polyurethane Organic–Mineral Base Containing Waste from Fibreglass Production
(MDPI, 2023-11-12) Hudec Jakubíková, Karolína; Hodul, Jakub; Hermann, Radek; Drochytka, Rostislav
In this study, the suitability of waste from glass fibre production as a secondary filler for a polymeric durable hydrophobic coating, based on an innovative polyurethane organic–mineral base, was experimentally verified. The main aim of this work was to develop a basic formulation for a polymeric hydrophobic coating designed primarily for usage in aggressive environments. For this purpose, a total of four formulations were tested with different weight percentages of waste glass fibre, i.e., from 30 to 60%. The basic properties in the fresh state, such as the coating workability and kinematic and dynamic viscosity, were verified, and an application test was performed. The formulations were also verified after the polymerisation of the coating. Adhesion on a concrete substrate and the tensile properties and hardness of the coating were tested. Chemical resistance to liquid aggressive media and the microstructure of the coating after exposure to SO2 were also tested, as these are critical properties. All the formulations showed better workability than the reference coating without a filler, and the formulation with the highest filling (60%) appeared to be optimal. The maximum adhesion on the concrete substrate (11.9 MPa) and tensile strength (21.6 MPa) were recorded for the formulation with 60% waste fibreglass. It can be concluded that with an increase in the waste glass content, there was a significant improvement in the properties of the coatings. Additionally, the waste fibreglass did not have a significant negative impact on chemical resistance.
The assessment and treatment of waste from glass fibre production for use as a filler in composites
(MATEC Web of Conferences, 2023-10-30) Hudec Jakubíková, Karolína; Hermann, Radek; Drochytka, Rostislav
Waste glass from fibreglass production is waste that is generated at various stages of production. In nature, it is a combination of glass fibres, fine dust, but also larger glass grains, for example also from leakages during production. This material is or may be contaminated by impregnation, lubricants or some impurities that prevent its recovery during production. The main objective of this study is to assess the suitability of glass fibre waste and to optimise the pre-treatment of the raw material for use in the composite. This paper describes the determination of chemical composition, mineralogical composition by X-ray diffraction analysis, determination of bulk density, water absorption and specific surface area. The results obtained are compared with the primary raw material - glass fibre. The results showed that the waste from glass fibre production is primarily composed of silica, calcium, alumina and boron. Minor components include magnesium oxide, sodium oxide, fluorine, iron oxide, strontium oxide, potassium oxide, titanium dioxide, sulphur dioxide and chromium oxide. The specific surface area of treated glass fibre waste correlates with the specific surface area of cement, which is a prerequisite for the use of this waste as a partial substitute for cement in the production of building materials.

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