Key Engineering Materials Vol. 808

Abstract: The utilisation of a relatively high amount of hazardous waste such as neutralising sludge (NS), which is a by-product of galvanic metal plating, as filler in a mechanically resistant composite material with an epoxy matrix, appears to be a progressive approach for improving the environment aspects. Polymer composites containing a filler of pure finely-ground silica sand – silica flour (SF) and fine foam glass waste (FGW) with a particle size of less than 200 μm were used for comparison of the achieved mechanical parameters. Considering the required consistency of the composite, related to its intended application in practice, 40% of the epoxy resin fillings was tested. It was shown that the developed, mechanically-resistant composite exhibits very high impact and wear resistance. Based on the assessment of the results obtained, it was found that the composite containing pre-treated hazardous waste achieved only 20% lower compressive strength than the reference composite, which comprised only primary raw materials. It is thus claimed that specific pre-treated hazardous waste can be effectively used for the preparation of special repairing composite material, and also in areas with a significant mechanical load.

Abstract: The main focus of this paper is research and development of new adhesive materials which will be possible to apply and withstand conditions of environments with exposure to aggressive chemical compounds. These new materials will also be required to withstand high temperatures up to 100°C. Main application of developed adhesives will be during laying of non-absorbent tiles mainly made from cast basalt. Several secondary raw materials were considered during the development of new adhesive mixtures as possible replacement of silicate filler components of new materials. The goal is to develop a new adhesive material with properties as close as possible to the highly durable non-absorbent elements used in stressed environments, mainly because the material will be also used for pointing between individual elements.

Abstract: Gypsum, or sulphate, binders are inorganic powder binders, which are among the so-called aerial mortars. These, after mixing with water, form a material that is well-workable for a certain time, which solidifies, hardens and is stable only in the air. Gypsum as a building material is formed by heating a raw material called plaster stone - CaSO₄·2H₂O and can acquire various properties depending on how it is produced. Its resulting properties can be affected to some extent by the source from which the raw material for its production is obtained, whether it is plaster stone or whether it the source is a secondary product from industrial production. [1] Production and use result from the ability of the original raw material to release crystalline-bound water under elevated temperatures and to bind it again after it has been added thus recreating a solid structure.

Abstract: Focusing on heritage structures, various non-destructive tests (NDT) or minor-destructive techniques (MDT) can be applied while the application of destructive testing is limited. The probabilistic models for tensile and compressive strengths of historic cast iron are developed on the basis of destructive tests (DTs) and MDTs, respectively. NDT results are critically compared with DTs. It appears that numerous uncertainties affecting estimated resistance can be treated by statistical approaches along with the semi-probabilistic verification method. Non-destructive hardness tests can hardly be used to estimate strength of cast iron and must be supplemented by destructive tests.

Abstract: Development of new material is focused on modification of properties of materials with silicate binder so that these could be used for renovation of horizontal structures of high-temperature devices and at the same time contribute to reduction of heat transportation of constructions with higher surface temperature (in this case 200 and 500 °C). Main requirements for this material is low volume weight and low coefficient of thermal conductivity. This paper assesses influence of exposition to higher temperatures on microstructure.

Abstract: For the rehabilitation and renovation of sewerage and gutter networks, different methods and technologies have been introduced over the last half-century. The trenchless technologies are showing the greatest development. They are promoted for reasons of environmental friendliness, they do not restrict the space in the place of renovation and the implementation is fast. The paper focuses on specific material starting points for the use of trenchless methods. Trenchless methods do not generate waste from original pipelines. New pipes are installed in the existing pipeline, or a new pipeline pushes the old profile into the surrounding area. However, the new pipeline is not accessible for the traditional methodology of result control and product performance verification. Particularly for Cured-in-Place-Pipe (CIPP) methods, it is difficult to determine representative quantities for key features such as the thickness of the sanitary insets (sleeves) after curing, and it follows from practice that the measurements should be performed with a special spike gauge. CIPP products achieve all the final properties through the installation process in the existing pipeline. Simulation on semi-operative polygons is increasingly being used for research and verification of suitable representatives. Authors of the article began to address this issue in research, in collaboration with the company WOMBAT, s.r.o. when investigating the higher resistance of CIPP lining.

Abstract: Laminated glass is a structural element used extensively in a reconstruction of existing building structures because of its transparency and simplicity. When using laminated glass as a glass staircase, balustrades, transparent flooring, facades or other structural elements, it is advisable to consider the shear interaction of individual glass panes in the cross-section. A conservative approach where the glass panes shear interaction is not considered, is uneconomical. This interaction depends on the properties of polymeric interlayers used in lamination process. Various commercial products based on PVB (polyvinyl butyral), EVA (ethylene vinyl acetate), ionomer, or thermoplastic polyurethane (TPU) are used. Stiffness of polymers depends on temperature and duration of a load. Interlayers exhibit the viscoelastic properties and temperature dependency usually described by the generalized Maxwell model and WLF model (Williams-Landel-Ferry). Parameters of these models are the most effectively determined by Dynamic Mechanical Thermal Analysis (DMTA), where the material is cyclically loaded at different frequencies and temperatures. Material parameters were found by DMTA in shear for PVB type of interlayer Trosifol® BG R20. In addition, the experimental quasi-static loading tests in shear were performed at different loading rates and at various temperatures. These experimental stress-strain diagrams were compared to the theoretical stress-strain relations obtained from Maxwell model with material parameters based on DMTA testing. All tests were performed in Klokner Institute CTU in Prague.

Abstract: How to extend your lifetime before you start using it or more often during use is a matter for every investor. In this paper, we will try to assess whether the use of protective coatings on concrete floors has a positive effect on the service life. The referee in our case will be the highly abrasive test method Böhme, which determines abrasion resistance. For comparison, we chose coatings based on sodium silicate solution, ie water glass. The market for these protective coatings is very diverse, so we have chosen to select products of renowned and unknown producers in different price ranges to cover the widest possible market.

Abstract: This paper studies the fundamental research and development of sprayed cement-based mixture designed to withstand the chemically aggressive conditions. The aim of this paper is to verify the possibilities of usage of suitable secondary raw materials as a substitution of a binder and filler of the original mixture while preserving or improving the physical-mechanical properties. In this part of the research was studied the possibility to substitute the binder in rate of 20-60 wt.% by high temperature fly ash and the whole filler by foundry sand and slag. Test samples were made from nine recipes, in which was monitored the influence of secondary raw materials on the compressive strength and the water absorption after 28 days of curing. The results of this paper show, it is possible to successfully substitute part of the binder by high temperature fly ash and the filler wholly by foundry sand in the sprayed mixture. These optimized recipes showed positive influence mainly in the long-term on mechanical properties.

Abstract: The aim of the research was verification of influence of aeration and influence of aluminum powder on microstructure and physical mechanical properties of calcium silicate composite material. At the same time, influence of various dosages of alternative raw materials on porous structure of the composite was examined. Tested raw materials are not the ones commonly used in the technology of manufacture of calcium silicate composites, for example chamotte blocks, Lining of silica and foundry sand. It was found that influence of aeration of calcium silicate composite causes reduction of compressive strength by roughly 85%. At the same time, volume weight drops by 50%. As a consequence of the expansion, intensity of diffraction lines of tobermorite detected by X-ray diffraction analysis is reduced because of reaction of aluminum powder with calcium hydroxide. It was found that there is dependency between the amount of replacement of silica sand with foundry sand and silica, and intensity of tobermorite diffraction lines, where the intensity of the diffraction lines was reduced with increased amount of replacement.