MATBUD’2020 – Scientific-Technical Conference: E-mobility, Sustainable Materials and Technologies

Cracow, Poland, October 19-21, 2020
T. Tracz, K. Mróz and T. Zdeb (Eds.)

ISBN: 978-2-7598-9108-5

Basic physical and mechanical properties of cement composites after temperature exposure

Dana Konakova1Eva Vejmelkova1Lenka Scheinherrova1Martin Keppert1An Cheng2 and Robert Cerny1

1 Czech Technical University in Prague, Faculty of Civil Engineering, Department of Materials Engineering and Chemistry, Thákurova 7, 166 29 Prague 6, Czech Republic
2 National Ilan University, Department of Civil Engineering, Shennong Rd., I-Lan 260, Taiwan

Abstract

Basic physical and mechanical properties of several cement composites are determined as functions of thermal load and the results are compared with reference materials. Bulk density, matrix density, and open porosity are measured using the water vacuum saturation method. Compressive and bending strengths are determined according to the European standard. High-temperature coefficient of thermal expansion is obtained using a comparative measurement. Experimental results show that composites based on Portland cement do not resist high temperatures well. Their applicability is limited to 400 °C, due to the damage caused by hydrates decomposition. On the other hand, composites based on calcium aluminate cement exhibit a better thermal stability and retain residual strength even after being exposed to 1000 °C.

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The potential of timber-based buildings in terms of energy efficiency

Jozef Švajlenka and Mária Kozlovská

Technical University of Košice, Faculty of Civil Engineering, Department of Construction Technology, Economy and Management, Vysokoškolská 4, 040 01 Košice, Slovakia

Abstract

The topic of energy efficiency is currently under discussion. One of the areas of energy efficiency is the energy efficiency of buildings. The thermo-technical requirements for building envelope structures are gaining increasing importance due to new legislation and technical regulations regarding the reduction of heating and energy demands of buildings over time and because of continuously increasing energy prices. Building construction and the operational costs of buildings are among the largest consumers of material and energy resources and environmental pollutants. Ecological constructions are a response to the current state of the environment. A suitable solution that represents ecological construction, operation and comfortable living is the construction of low-energy and passive houses based on wood. Wood-based buildings have many benefits that are particularly timely in the context of sustainability today. The aim of this paper is to introduce selected aspects of wood-based buildings in the context of energy efficiency and thus to reduce the adverse effects of construction on the surrounding environment.

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The binding properties of cementitious materials using circulating fluidized bed co-fired fly ash and pulverised coal fly ash

Wei-Ting Lin1An Cheng1Michał Łach2Krzysztof Miernik2 and Kinga Korniejenko2

1 National Ilan University, Department of Civil Engineering, Shennong Rd., I-Lan 260, Taiwan
2 Cracow University of Technology, Faculty of Materials Engineering and Physics, Institute of Materials Engineering, Warszawska 24, 31-155 Cracow, Poland

Abstract

This study aims to investigate the binding properties of co-fired fly ash (CFFA) in paste and mortar specimens. Paste specimens containing various CFFA proportions (25%, 50%, 75%, 100% by weight of cement) were conducted and evaluated using setting time tests, water demand tests and compressive strength tests. Mortar specimens containing various CFFA and Pulverised coal fly ash (PCFA) proportions (10%, 20%, 30% by weight of cement) were also conducted and compared with regard to flowability and compressive strength. The test results indicated that the water demand increased as the amount of CFFA replacement increased on the flow level at 110±3%; this is due to the higher ignition loss (L.O.I.). Higher L.O.I. values mean that there are more unburned carbon particles in the CFFA and that most of these carbon particles are porous. The compressive strength of mortar specimens decreased as the amount of CFFA replacement increased. Compared to the chemical compositions of cement (C3S, C2S), the main components of CFFA (Ca(OH)2, CaCO3, CaO) have lower crystalline strength and compactness. Therefore, the higher amount of CFFA replacement would inevitably cause a reduction of the cement contents of specimens, thereby reducing the compressive strength of the mortar specimens. Thus, an appropriate amount of superplasticiser and CFFA replacement in the mixture is useful with regard to the binding properties of cementitious materials.

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The impact of the curing process on the efflorescence and mechanical properties of basalt fibre reinforced fly ash-based geopolymer composites

Kinga Korniejenko1Dariusz Mierzwiński1Roland Szabó2Nóra Papné Halyag2Petr Louda3Eythor Rafn Thorhallsson4 and Gábor Mucsi2

1 Cracow University of Technology, Institute of Material Engineering, Faculty of Material Engineering and Physics,, Warszawska 24, 31-155, Cracow, Poland
2 University of Miskolc, Institute of Raw Material Preparation and Environmental Processing, 3515, Miskolc, Egyetemváros, Hungary
3 Technical University of Liberec, Faculty of Mechanical Engineering, Department of Material Science, Studentska 2, Liberec, 461 17, the Czech Republic
4 Reykjavik University, Civil Engineering, Menntavegur 1, IS-101, Reykjavik, Iceland

Abstract

Efflorescence is one of the limitations of the widespread use of geopolymers. This problem is caused by excess unreacted sodium oxide remaining inside materials. Unreacted sodium oxide creates white efflorescence on the surface of the produced material in the form of sodium carbonate heptahydrate Na2CO3∙ 7H2O. It decreases not only the aesthetic value of the final products, but also the mechanical properties of the material. The aim of this article is to analyse the influence of the curing method on the appearance of efflorescence on geopolymer composites reinforced by short basalt, especially on mechanical properties. Class F fly ash from the ‘Skawina’ coal-fired power plant (located in Skawina, Lesser Poland, Poland) was used as raw material for the geopolymerization process. The article compares two methods of curing: typical laboratory conditions (in the air) and samples submerged in water. Three series of fly ash-based geopolymer were cast: basalt fibres were added as 1% and 2% by weight of fly ash and one control series without any fibres. The investigation was performed using visual analysis, including microstructure investigation, and the testing of mechanical properties (compressive strength at ambient temperature) after 28 days.

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Towards the sustainable use of granite powder waste for manufacturing of cementitious composites

Adrian Chajec1

1Wrocław University of Science and Technology, Faculty of Civil Engineering, pl. Wyspiańskiego 37 50-370 Wrocław, Poland

Abstract

The article is devoted to the description of the current state of knowledge about the possibilities of sustainable use of granite powder waste for manufacturing of cementitious composites. Granite powder waste is waste material resulting from the treatment of granite stone. In dry form, it is harmful to the environment and causes its degradation. One way to reduce its harmful effects is to use it for the sustainable production of cement composites and to use it as supplementary cementitious material (SCM). The results of researches carried out so far related to the impact of granite powder waste on the properties of fresh and hardened cementitious mixes are described. These results were compared and research gaps related to these studies were indicated. In summary, conclusions have been pointed out that indicate that granite powder waste can potentially be used as supplementary cementitious material, but comprehensive, comprehensive research related to this additive should also be carried out.

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