Ústav technologie stavebních hmot a dílců

Browse

Now showing 1 - 5 of 147

Utilization of alternative wood particles for modern thermal insulation products
(IOP PUBLISHING LTD, 2024-05-13) Zach, Jiří; Peterková, Jitka; Novák, Vítězslav; Korjenic, Azra
Thermal insulation materials play a vital role in minimising energy loss in building operation and also affect the amount of greenhouse gas emissions associated with heating and cooling. In this context, it is becoming an increasingly important milestone to find suitable thermal insulation materials that not only meet the technical requirements but also minimise their environmental impact. The trend towards the use of eco-friendly materials for thermal insulation reflects the construction industry's desire to contribute to environmental protection and the transition to more sustainable models of building construction and renovation. For more than 20 years, a number of research teams have been investigating the possibility of replacing synthetically produced materials such as mineral wool and polystyrene foam with natural fibre-based insulation materials. These alternatives include wood as a traditional, easily renewable raw material. This, together with the low energy intensity of processing and manufacturing wood materials, contributes to its low carbon footprint. Compared to traditional synthetic insulation materials, which are often energy intensive to produce, wood is a more environmentally friendly choice. However, with many European countries now facing a potential shortage of higher quality wood, it is necessary to look for alternative sources of wood, including in the field of thermal insulation materials, materials with a lower carbon footprint that can be produced from lower quality wood or from wood waste that would otherwise only have an energy use. The paper is devoted to the study and use of suitable wood waste and secondary raw materials from spruce wood (coarse wood chips, sawdust and wood flour) for the development of modern thermal insulations with the aim of an environmentally friendly and less energy-intensive production process compared to conventional insulants.
Production of concrete pavements using mixed cements
(Czech Technical University in Prague, 2024-05-16) Klobása, Jan; Hela, Rudolf
Currently, great importance is attached to the reduction of emissions in industrial production, especially in the production of cement, when it is indicated that during production 1 ton of cement produces approximately 0.6 ton of CO2. Reducing emissions is possible thanks to secondary raw materials, which are produced in large quantities in the Czech Republic volumes for which a suitable use is sought. Some secondary raw materials are suitable for use in concrete mixes, which are used to improve the rheology of the fresh concrete mixture as well as the properties hardened concrete. Currently, there is an effort to eliminate the production of cement, to which its partial replacement by admixtures could also contribute. Therefore it is necessary determine the optimal admixture that could be used to replace part of the cement in concrete mix. A large consumer of concrete mixes are transport structures, where it is possible for some of the cement used to be replaced by an admixture.
Characteristics of Fibres Based on Secondary Raw Materials and Their Use in Concrete Technology
(Czech Technical University in Prague, 2024-05-18) Sedlmajer, Martin; Bubeník, Jan; Zach, Jiří; Novák, Vítězslav
Different types of fibres in cementitious composites, particularly in concrete, are currently used for a number of reasons. Fibres are being added to improve mechanical properties (especially steel and glass fibres), to increase the durability – to reduce occurrence of microcracks during the concrete aging (mainly synthetic and cellulose fibres), or to increase the fire resistance (polypropylene fibres). Within the study, characterization of different types of alternative fibres (fibres generated during waste recycling that would otherwise end in incinerators or landfills) with possible use in cementitious composites. These were fibres from recycled PET bottles, paper, and mineral wool, whose properties were compared to the traditionally used cellulose and polypropylene fibres. In the experimental part, the thickness, length, shape, and surface of individual fibres were monitored by an optical microscope. Furthermore, the amount of heat of combustion was determined by the calorimetric method, and the differential thermal analysis (DTA) was carried out for determination of the impact of high temperature on monitored fibres. The microstructure of fibres was monitored using a scanning electron microscope. The focus of the experimental study was on fibres usable in concrete and capable of enduring high temperature stress.
Stabilization of the ammonia in SNCR fly ash - the influence of tannins presence on the preparation of an autoclaved aerated concrete
(IOP Publishing, 2019-08-14) Dlabajová, Lucie; Lédl, Matěj; Beranová, Denisa; Opravil, Tomáš
Thanks to the legislative regulations on NOx emissions, a selective non-catalytic reduction (SNCR) technology had been introduced to a coal combustion process in power plants. The valuable by-product, fly ash, contains ammonia in the form of soluble salts, e.g. NH4HSO4 and (NH4)2SO4. After mixing SNCR fly ash with cement, thanks to the rise of pH, the toxic ammonia releases and contaminates the working area, so the presence of these salts is undesirable in an autoclaved aerated concrete (AAC) manufacturing process. A possible solution is the conversion of soluble ammonium salts to an insoluble form. Tannins are a class of polyphenolic biomolecules, which react with the ammonium ions to form insoluble compounds. The AAC samples were mixed using SNCR fly ash and two different ammonium binding additives - pure tannic acid and the cost-effective animal food supplement containing chestnut tannins. The influence of additives on the hydration process of the starting mixture was studied by isoperibolic calorimetry. The results suggest that the cost-effective source of tannins retards the hydration. The presence of insoluble compounds was studied by the infrared spectroscopy.
Preparation and Characterization of Glass-Ceramic Foam from Clay-Rich Waste Diatomaceous Earth
(MDPI, 2022-02-13) Sedlačík, Martin; Nguyen, Martin; Opravil, Tomáš; Sokolář, Radomír
In this study, the potential of use of waste diatomaceous earth from production of diatomaceous earth for filtration purposes, as an alternative raw material for foam glass production, was explored. The Chemical and mineralogical composition, and the high temperature behavior of waste diatomite were studied to assess the suitability of this material for foam glass production. Glass-ceramic foams were prepared using NaOH solution as foaming agent, via hydrate mechanism. The Influence of different pretreatment and firing temperatures on the foam’ structure, bulk density and compressive strength was investigated. High temperature behavior was studied using TG/DTA analysis and high temperature microscopy. Phase composition was studied using X-ray diffraction analysis. Glass-ceramic foam samples of high porosity comparable to conventional foam glass products were fabricated. Both pretreatment temperature and foaming temperature were found to have a significant influence on foam properties. With increased pretreatment temperature pyrogenic carbon from thermal decomposition of organic matter contained in the raw material acted as an additional foaming agent and remained partially unoxidized in prepared foams. Bulk densities of prepared samples ranged from 150 kg/m3 to 510 kg/m3 and their compressive strength was between 140 and 1270 kPa.

Browse

Recent Submissions