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
1, 1, 1, 1, 2 and 1
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.
The potential of timber-based buildings in terms of energy efficiency
and
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.
1, 1, 2, 2 and 2
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.
The impact of the curing process on the efflorescence and mechanical properties of basalt fibre reinforced fly ash-based geopolymer composites
1, 1, 2, 2, 3, 4 and 2
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.
Towards the sustainable use of granite powder waste for manufacturing of cementitious composites
1
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.
The hygrothermal performance of concrete with coarse aggregates made of recycled concrete pavements
1, 1, 1 and 2
1 Czech Technical University in Prague, Faculty of Civil Engineering, Department of Materials Engineering and Chemistry, Thákurova 7/2077, 166 29 Prague 6, Czech Republic
2 Cracow University of Technology, Faculty of Civil Engineering, Chair of Building Materials Engineering, 24 Warszawska St., 31-155 Cracow, Poland
Abstract
This paper deals with an investigation of the hygrothermal performance of concretes containing various amounts of recycled aggregates originating from crushed concrete pavements. The performance, which was obtained using computational modelling of coupled heat and moisture transport, is predicted on stand-alone samples as well as on built in samples in a real construction exposed to weather data of Ostrava, Czech Republic. The results revealed that the influence of recycled aggregates as substitution for natural stone does not negatively affect the hygrothermal performance of the concrete. The highest difference found was less than 1°C and 12% of RH in the case of stand-alone samples and only 2.2% of RH when built in. Therefore, the application of crushed concrete pavements as aggregates in concrete composition can be highly recommended as it brings other benefits such as economical and environmental.
Basic Physical, Mechanical, Thermal and Hygric Properties of Concrete with Coarse Aggregates Fabricated from Recycled Concrete Pavements
1, 1, 1, 2 and 3
1 Czech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7, 166 29 Prague, Czech Republic
2 National Ilan University, College of Engineering, Department of Civil Engineering, No.1, Sec. 1, Shennong Rd., I-Lan 260, Taiwan
3 Cracow University of Technology, Faculty of Civil Engineering, Institute of Building Materials and Engineering Structures, Warszawska 24, 31155 Kraków, Poland
Abstract
Concrete production unfavourably affects the environment due to high energy demands of cement production and consumption of limited natural resources. Therefore, waste utilization in fabrication of cementitious material is beneficial and legitimate. Significant reduction of environmental impact can be secured by utilization of various types of wastes or byproducts used for a partial substitution of cement binder or aggregates. However, the use of waste materials usually leads to deterioration of material properties of the designed composites. Therefore, it is very important to thoroughly investigate important materials properties to verify performance and practical usability of the newly designed materials. In this paper, three types of concrete mixes were designed. The reference concrete involved fine and coarse natural riverbed aggregates and two other mixes were designed using both, natural and recycled aggregates represented by crushed concrete paving cobbles. Concretes were tested in terms of basic physical properties (bulk density), mechanical properties (compressive strength), thermal properties (thermal conductivity, specific heat capacity, thermal diffusivity), and hygric properties (water vapour diffusion resistance factor, water vapour sorption at 97% RH, water absorption coefficient, moisture diffusivity) and experimentally determined data were compared and discussed. It was observed that materials properties of concretes with recycled aggregates are comparable with those of the reference concrete which is a promising fact from the environmental point of view.
The influence of alkaline activator concentration on the apparent activation energy of alkali-activated materials
1, 1 and 2
1 Cracow University of Technology, Institute of Materials Engineering, Faculty of MaterialsEngineering and Physics, Warszawska 24, 31-155 Kraków, Poland
2 SENVI Sustainability Consultants, Płocka 15, 01-231 Warszawa, Poland
Abstract
The aim of this article is to analyse the changes of apparent activation energy (Ea) of alkali-activated materials (AAM) at temperatures up to 100°C. Apparent activation energy (Ea) refers to the minimum amount of energy is required for the occurrence of reaction. The existing AAM research is based on assumptions about Portland cement (OPC). A number of studies have been conducted on the development of concrete strength depending on, inter alia, the duration of seasoning and the liquid to solid ratio (L/S). Based on the apparent activation energy and taking into account the effect of time and temperature at the same time, the physical and mechanical properties of OPC can also be predicted. The influence of the activator on the solidification process should also be taken into account for alkali-activated materials. This article shows the effect of changes in the concentration of the alkaline solution used in the AAM process on activation energy. The synthesized AAM material uses a solution based on water glass, sodium hydroxide, sand and volatile ash from the ‘Skawina’ coal-fired power plant (located in Skawina, Lesser Poland). The chemical composition of the material used is classified as class F ash. The concentration of the alkaline solution was 8M, 10M, 12M and 14M. The described research method was based on the use of thermistors with a negative temperature factor. It enabled prediction of the physical and mechanical properties of the materials tested. The results clearly indicate that this method can be used to determine the activation energy of the AAM. However, when determining apparent activation energy (Ea), the time and activation temperature of the binding processes of these types of materials should be taken into consideration.
Effect of limestone powder on strength and permeability of cementitious mortars
1, 1 and 2
1 National Ilan University,,Department of Civil Engineering, Shennong Rd., I-Lan 260, Taiwan
2 Czech Technical University in Prague, Faculty of Civil Engineering, Department of Materials Engineering and Chemistry, Thákurova 7, 166 29 Prague 6, Czech Republic
Abstract
This study investigated the mechanical properties and durability of mortar specimens containing various quantities of waste limestone powder (0%, 10%, 20%, and 30% of the weight of cement). The mechanical properties were evaluated in terms of flowability, compressive strength, and splitting tensile strength. Permeability was evaluated in terms of resistivity, absorption, and rapid chloride penetration (total charge- passed). Test results revealed that replacing 10% of the cement with limestone powder improves both mechanical performance and durability. However, reducing the cement content reduced the availability of hydration products to fill the pores in the microstructure. The hydration product of limestone powder was mainly calcium hydroxide, which undermines the development of strength in the paste. Nonetheless, our results indicate that waste limestone powder is suitable for the partial replacement of cement.
Application of the GPR and ERT methods for non-invasive examination of a flood dike
1, 2 and 1
1 Cracow University of Technology, Faculty of Environment and Power Engineering, Warszawska 24, 31-155 Cracow, Poland
2 Ecole Centrale de Lille, Institut d'électronique, Microélectronique & Nanotechnologies, Cité Scientifique, Avenue Henri Poincaré CS 60069, 59-652 Villeneuve d'AscqCedex, France
Abstract
As part of the NAWA-EMMAT project, geophysical surveys were carried out on selected sites in Poland, i.e. on the flood dike and in the surrounding of the concrete water dam. The goal of the surveys was the non- invasive detection of loose zones in the flood dike and fractured zones located in the subsoil of the water dam. Terrain geophysical measurements were conducted with the use of electrical and electromagnetic methods as well as applying seismic methods. Due to the limitations of the length of this paper, only selected results recorded on the flood dike using selected geophysical methods, i.e. electrical resistivity tomography (ERT) and ground penetrating radar (GPR) are presented. The presence of several higher hydraulic permeability zones in the dike was suggested by the results of the ERT method. The GPR method allowed, due to its high resolution, to identify small leakage zones in the body of the dike. An attempt at a quantitative interpretation of the geophysical data was made; for this purpose, the synthetic results obtained from numerical modelling of electrical and electromagnetic fields were applied. For proper construction of numerical models and further interpretation, the results of geotechnical sounding, geological drilling and the results of petrophysical measurements were also used.
The influence of microstructure on mechanical properties of 3D printable geopolymer composites
1, 1, 2 and 3
1 Cracow University of Technology, Faculty of Material Engineering and Physics, Institute of Materials Engineering, Warszawska 24, 31-155 Cracow, Poland
2 National Ilan University, Department of Civil Engineering, Shennong Rd., I-Lan 260, Taiwan
3 University of Technology Sydney, School of Civil and Environmental Engineering, 81 Broadway, Ultimo NSW 2007, Sydney, Australia
Abstract
The additive manufacturing technologies are fast-developing industrial sector and, potentially, a ground-breaking technology. They have many advantages such as the saving of resources and energy efficiency. However, the full exploitation of 3D printing technology for ceramic materials is currently limited; a lot of research is being conducted in this area. A promising solution seems to be geopolymers, but its application requires a better understanding of the behaviour this group of materials. This article analyses the influence of microstructure on mechanical properties whilst taking the production method into consideration. The paper is based on comparative analysis – the investigation is focused on the influence of material structure on the mechanical properties and fracture mechanism of these kinds of composites, including those reinforced with different kind of fibres. As a raw material for the matrix, fly ash from the Skawina coal power plant (located in: Skawina, Lesser Poland, Poland) was used. The investigation was made by SEM analysis. The results show that the microstructural analysis did not sufficiently explain the underlying reasons for the observed differences in the mechanical properties of the composites.
The influence of fibre pre-treatment on the mechanical properties of the geopolymer composites
1, 1, 2, 2, 3 and 1
1 Cracow University of Technology Institute of Material Engineering, Faculty of Material Engineering and Physics, Warszawska 24, 31-155 Cracow, Poland
2 Brno University of Technology, Faculty of Civil Engineering, Veveří 331/95, 602 00 Brno, the Czech Republic
3 Universidad Católica del Uruguay, B de Octubre 2738, CP 11600, Montevideo, Uruguay
Abstract
This article aims to analyse the long-term influence of the pre- treatment method on mechanical properties such as the compressive strength of geopolymer composites reinforced with short natural fibres (length of around 5 mm). This paper presents the behaviour of sodium activator-synthesised fly ash geopolymer containing natural fibres at ambient temperatures. Fly ash from the Skawina coal power plant (located in: Skawina, Lesser Poland, Poland) was used as a raw material. The chemical composition of the fly ash was typical for class F. The article evaluated the methods of pre-treatment of the fibres on the mechanical properties of the geopolymer composites. It compares the plain specimens and composites with fibres pre-treated in water and alkali solutions as well as with fibres without any pre-treatment. The fibres were added at the amount of 1% by weight. The investigation was made by visual analysis and the testing of mechanical properties (compressive and flexural strength at ambient temperature) after 6 months. The achieved results do not confirm the positive influence of the fibre pre-treatment on the mechanical properties of the composites.
Materials Selection and Tests for Precise Execution of Foundry Molds Designed to Geopolymer Casts
1, 1, 2 and 1
1 Cracow University of Technology, Faculty of Material Engineering and Physics, Institute of Materials Engineering, Warszawska 24, 31-155 Cracow, Poland
2 Malta College of Arts, Science and Technology, MCAST Energy Research Group, Triq Kordin, Raħal Ġdid, 2001, Paola, Malta
Abstract
The paper presents the results of research on the selection of material for molds intended for geopolymer castings as well as an appropriate technological process for the preparation of such castings. Three silicons with different elasticity and hardness of 30, 40 and 60Sh were tested. The above-mentioned rubbers were used to make one-piece open molds and test the performance of each material. A model having several details and a small flat surface was chosen for the replica. Based on this variation in the wall structure, it was possible to assess the accuracy of mapping, both small elements and straight cast planes. In the prepared forms 10 tests of geopolymer casting were carried out to develop the best technological process. The appropriate result was achieved when the molds covered with the divider were flooded with raw material by vibrating them on a vibrating table, and then allowed to react for an hour for free mass components and leaking gases to the surface. After a set time, the compaction was carried out again to more accurately eliminate the resulting air bubbles. The effect of this method is to obtain a cast with precisely mapped details and a smooth even surface, and almost complete elimination of air bubbles from representative surfaces.
The Use of Geopolymers for the Disposal of Asbestos-containing Materials
1, 1, 1, 2 and 1
1 Cracow University of Technology, Faculty of Material Engineering and Physics, Institute of Materials Engineering, Warszawska 24, 31-155 Cracow, Poland
2 National Ilan University, Department of Civil Engineering, Shennong Road, Yilan City, Yilan County, 260 Taiwan
Abstract
Asbestos is widely known as a hazardous material and can contribute to many diseases. Its removal and neutralization are complicated, it requires proper preparation and the use of appropriate technology. Immobilization of asbestos materials in geopolymers seems to be one of the alternatives to its storage in landfills. However, this requires several studies confirming the possibility of asbestos immobilization in geopolymers. Also, asbestos dust contains silicon and aluminum, which may prove useful in the production of geopolymers. The paper presents research results regarding the possibility of using geopolymers based on fly ashes for neutralizing asbestos. An up-to-date literature review on the technology of managing asbestos-containing products is presented. As a result of the research, partial usefulness of geopolymerization technology for binding and neutralizing waste with asbestos was found. The research was carried out using waste asbestos-cement composites. Mixtures based on geopolymers were made in which ground asbestos material was introduced in an amount of 30, 50 and 70% by weight. Compressive strength tests have shown that geopolymers with the addition of asbestos have compressive strength: over 34 MPa for a composition containing 30% of asbestos material and about 14 MPa for a composition containing 70% of asbestos material. SEM observations have shown that asbestos fibers do not dissolve in the geopolymer production process and they can still be a threat if the geopolymer matrix is damaged.
Non-traditional Approach to the Evaluation of the Freeze-thaw Resistance of Concrete based on the Fracture Tests
1, 1, 1 and 2
1 Brno University of Technology, FCE, Veveří 331/95, Brno, Czech Republic
2 Federal University of Rio de Janeiro, COPPE/PEC, Rio de Janeiro, Brazil
Abstract
The paper deals with a pilot study focused on the freeze-thaw (F-T) resistance of concrete. A non-traditional approach to the evaluation of the F-T resistance of concrete based on the determination of the fracture parameters is presented in the paper. Three types of specimens were used in the experimental program – prisms with edge and Chevron notch, and cylinders with the Chevron notch. Three sets of specimens of each shape were tested in total. The reference set was stored in the water until the time of testing. Another two sets of specimens were subjected to 50 and 100 freeze-thaw tests, respectively. One F-T cycle consisted of 4 hours freezing in the air at temperature -18 °C and 2 hours thawing in the water at temperature +20 °C. Based on the results, it can be stated that the values of fracture energy are proportional to the area of the ligament. This finding was observed for all tested sets – non-frost and frost attacked. The values of modulus of elasticity and fracture toughness are influenced more by the geometry and also by the changes of the specimens’ stiffness due to the exposition to the F-T cycles.
The Fly-Ash Based Geopolymer Composites as an Innovative Material for Circular
1, 2, 1, 1 and 3
1 Institute of Materials Engineering, Faculty of Material Engineering and Physics, Cracow University of Technology, Jana Pawła II 37, 31-864 Cracow, Poland
2 Department of Engineering and Water Management, Faculty of Environmental and Power Engineering, Cracow University of Technology, Warszawska 24, 31-155 Cracow, Poland
3 MCAST Energy Research Group, Malta College of Arts, Science and Technology, Triq Kordin, Raħal Ġdid, 2001, Paola, Malta
Abstract
A circular economy is the answer to the problem of wasting raw materials and increasing environmental pollution. It is based on the effective use of materials - from extraction, through use, to the way of managing waste. Analyzing the impact of particular industries on the production of pollution, it can be concluded that the construction is one of such industries. In order to reduce the negative impact of the construction on the environment resulting from energy consumption and large amounts of generated waste, various researches are carried out on modern and innovative materials production solutions. One of the possibilities is a production technology based on the alkaline-activated compositions and geopolymers. The advantage of this technology is that it has a much lower carbon footprint compared to the traditional production methods used in construction - during the synthesis of geopolymers the emission of CO2 is 4-8 times lower and also the energy consumption is reduced up to 2-3 times. This article shows the possibility of using the industrial and mining waste for creating new eco-friendly materials – geopolymers. The paper presents the results of studies on geopolymer composites reinforced with addition of 1% by weight of different types of natural fibers i.e.: short hemp fibres, raw flax fibres (shortened), long flax fibres (stannous) and linseed cotonin. The paper showed that geopolymer composites can be successfully produced with the addition of natural fibres (often waste) and have good strength parameters even after long-term use.
The effect of fly ash and granulated blast furnace slag on slip and tensile adhesion strength of tile adhesives mortars
1
1Sieć Badawcza Łukasiewicz – Instytut Ceramiki i Materiałów Budowlanych, Oddział Szkła I Materiałów Budowlanych w Krakowie
Abstract
In the formulations of adhesive mortars for tiles almost exclusively CEM I Portland cements are used. Practically no CEM II - CEM V cements with additives are used, although they are often produced with strength classes 32.5 R and some even 42.5R. Relationship between strengths of tile adhesives in which cement was partially replaced with fly ash and granulated blast furnace slag was studied. A fly ash was used in three different replacement levels from 5% to 25% by weight of either cement. The tensile adhesion were determined at 28 and 90 days after various conditioning conditions of the samples. The influence on the flexibility of mortars was also assessed. In small substitution levels, fly ash replacement increased the tensile adhesion strength. The results indicate that the optimal amount of fly ash and granulated blast furnace slag additive replacing a given amount of cement allows to obtain adhesive mortars for tiles with high functional parameters.
Properties of geopolymers from conventional fly ash activated at increased temperature with sodium hydroxide containing glass powder obtained from the recycling of waste glass
1 and
1Opole University of Technology, Civil Engineering and Architecture Faculty, Katowicka St. 48, 45-061 Opole, Poland
Abstract
This paper presents test results of the physical and mechanical properties of geopolymers based on conventional fly ash activated at increased temperature with sodium hydroxide, containing glass powder obtained from the recycling of waste glass. Tests were performed on mortars of a geopolymer binder containing glass powder of various levels of fineness, at quantities ranging from 5 to 95% of the mass of the conventional fly ash. The properties of the geopolymer binder with and without the content of glass powder were determined on the basis of the heat of hydration. The suitability of the application of glass powder in geopolymers was confirmed by results of testing the following parameters using a scanning electron microscope (SEM) and analysis of micro areas (EDS) in geopolymer materials: particle size distribution, density, porosity, X-ray diffraction (XRD). Testing of the compressive strength of the geopolymer mortars was performed after: 1, 7, 14 and 28 days of curing in air-dry conditions. Results of microstructure tests confirm that the glass powder coming from recycled waste glass in presence of the geopolymer binder undergoes reactions of alkaline activation at increased temperature, the products of which are zeolite minerals and sodium silicate gel. On the basis of test results of physical and mechanical properties of the geopolymers, it was proven that the content of glass powder had a beneficial effect on the utility parameters of the obtained material. The aforementioned research confirms the possibility of using waste glass for the production of geopolymer materials applied in the construction industry.
Assessment of long-lived residual radioisotopes in cement induced by neutron radiation
1, 2, 2, 1 and 1
1 Institute of Fundamental Technological Research Polish Academy of Sciences, Pawińskiego 5b, 02-106 Warsaw, Poland
2 Nuclear Analysis and Radiography Department, Centre for Energy Research, 29-33 Konkoly Thege Miklós St. 1121, 29-33 Budapest, Hungary
Abstract
During the decommissioning of nuclear power plants, a significant amount of cement based composites should be disposed as radioactive waste. The use of material with low-activation constituents could effectively reduce radioactivity of concrete. The subject of the paper is the content of trace elements with large activation cross section in concrete constituents due to their ability to be activated in radiation shielding structures. Various Portland cement specimens were subjected to elemental analysis by neutron activation analysis and prompt gamma activation analysis to assess the dominant long-lived residual radioisotopes. Concentrations of the radionuclides, such as Europium-152, Cobalt-60 and Caesium-134 were assessed. Their half-life time is 13.5, 5.27, and 2.07 years, respectively. On the basis of the obtained results, recommendations for cement selection for low-activation concrete are proposed in order to economize decommissioning cost by reducing a radioactive concrete waste.
Abrasive water jet machining of fly ash and metakaolin based geo-polymers
1, 1, 2, 2 and 2
1 Faculty of Mechanical Engineering, Kalasalingam Academy of Research and Education, Krishnankoil - 626126, India
2 Institute of Materials Engineering, Faculty of Material Engineering and Physics, Cracow University of Technology, Jana Pawła II 37, 31-864 Cracow, Poland
Abstract
In the present study, the abrasive water jet machining (AWJM) of geopolymers prepared from fly ash, metakaolin and sand is discussed. The samples were prepared from sodium promoter, fly ash / metakaolin and sand. The process of activation was made using a 10M sodium hydroxide solution combined with a sodium silicate solution (the ratio of liquid glass - 1:2.5). To produce geopolymers, flakes of technical sodium hydroxide were used and an aqueous solution of sodium silicate (R-145) with a molar module of 2.5 and a density of around 1.45 g/cm3 the tap water. The alkaline solution was prepared by means of pouring the aqueous solution of sodium silicate over the solid sodium hydroxide. The solution was mixed and left until its temperature stablised and the concentrations equalised, which took around 2 hours. The fly ash, sand and alkaline solution were mixed for around 10 minutes using a low-speed mixing machine (in order to obtain a homogeneous paste). The paste was allowed to dry in the shade. The paper investigates the AWJM studies on the prepared geopolymer specimens with varyied input parameters such as standoff distance (1.2 and 3 mm), water pressure (120, 140 and 160 MPa) and feed rate (5, 10 and 15 mm/min). The output parameters such as kerf angle and material removal rate (MRR) were studied with the varying combination of input parameters. From the results, the optimal parameters for machining the geopolymer composites were interpreted.
Ecological and technological effects of using concretes with low Portland clinker
1, 2 and 3
1 Sieć BadawczaŁukasiewicz – ICIMB Kraków
2 Sieć BadawczaŁukasiewicz – ICIMB Warszawa
3 Akademia WSB – DąbrowaGórnicza
Abstract
Concrete with a low Portland clinker content involves the use of mineral additives as a cement component or as a additive in a concrete mix. The main factors influencing the increasing use of mineral additives in concrete technology are the advantageous development of the functional properties of the concrete mix, hardened concrete and a large impact on the ecological effects, including reduction of CO2 emissions. The use of concrete with a low Portland clinker content is part of the strategy for sustainable development of the economy. This paper describes the technological and ecological effects of using silica fly ash and granulated blast furnace slag additives in concretes with a low Portland clinker content. The cement and concrete additives used were mechanically activated, which allowed to reduce the content of Portland clinker in concrete. A new generation superplasticizer was used in the research, enabling a low water-cement ratio to be obtained. The mechanical properties and ecological effects of the production and use of concretes with a low content of Portland clinker were determined, including the reduction of CO2 emissions. Test results confirmed the very good mechanical properties of concrete with a high content of mechanically activated mineral additives. The research also showed an average of 3 times lower CO2 emissions compared to reference concretes made of CEM I Portland cement without additives.
Microstructure of autonomous self-healing concrete
1 and 2
1 Cracow University of Technology, Faculty of Civil Engineering, Chair of Construction Engineering and Building Physics, Warszawska St. 24, 31-155 Cracow, Poland
2 Cracow University of Technology, Faculty of Civil Engineering, Chair of Building Materials Engineering, Warszawska St. 24, 31-155 Cracow, Poland
Abstract
Over the past years, many research projects in the field of construction have been based on the concept of intelligent materials. One example of such materials is self-healing concrete. This material has the ability to repair the damage that occurs, which in concrete materials means filling/closing the cracks formed. This paper describes autonomous concrete that heals itself thanks to modifications with mineral additives. The study used the basic method of evaluating the effectiveness of the healing process, which is visual observation of the material. For this purpose, tests were performed using optical, digital and electron microscopes. In addition to the observations, a chemical analysis of the composition was performed using the EDS detector mounted on the SEM. The findings indicate the ability of filling cracks with accumulating products of reaction with water.
Microstructure of biopolymer-modified aerial lime mortars
, , and
1Brno University of Technology Faculty of Civil Engineering, Veveří 331/95, 602 00 Brno, Czech Republic
Abstract
Cellulose-based viscosity-modifying admixtures are used on daily basis in a wide range of building materials, dominantly in pre-mixed mortar systems. Lately, alternative admixtures such as different “gums” have emerged. In building materials, the gums have similar viscosity-enhancingeffects as cellulose ethers with different efficiency. Various ways of production, as well as diverse working mechanisms of the biopolymers are to be considered while choosing the most suitable admixture for the intended use. Influence of alternative admixtures in several doses on the microstructure of lime mortars was studied in this paper. Mortars were prepared with the same workability and the air content in fresh mortar was determined, for it can have notable impact on microstructure of hardened mortar. Hydroxypropyl derivative of chitosan showed air entraining ability, while the carboxymethyl derivative reported slight decrease in amount of air entrained into the mixture. In the case of diutan gum, the most water-demanding admixture, the percentage of entrained air dropped with growing dose. Admixture addition increased the volume of pores in diameter lower than 0.1 μm, and in region of pores around 10 μm. Only the diutan gum affected the distribution of capillary pores, which are typical for lime mortars. Hygric properties were in correlation with air content values.
Functionality and durability of anti - graffiti - systems on concrete
1,2, 2 and 1
1 University of Rostock, Agricultural and Environmental Sciences, Justus-von-Liebig-Weg 6, 18059 Rostock, Germany
2 Hochschule Wismar University of Applied Sciences Technology, Business and Design, Faculty of Engineering, Philipp-Müller-Straße 14, 23966 Wismar, Germany
Abstract
Property damage and vandalism through illegal graffiti can be found worldwide. As graffiti increased, so did the interest in proper removal and the possibilities of a high-quality protection system. Anti- graffiti systems (AGS) can be used to protect objects and buildings from damage caused by graffiti. At present, AGS is still recommended for use in unspecified areas for plastics, metal, wood, brick, concrete and natural stone. In practice, it has turned out that no AGS is suitable for all surfaces. A specific reference to surface quality and properties is missing. For graffiti protection, however, the surface properties are of particular importance. They influence the liability of the AGS on the one hand and the removability of the graffiti on the other. This study is intended to demonstrate the extent to which concrete types and surfaces influence the functionality and durability of permanent AGS. This paper presents first results of practical tests on 180 concrete test specimens after currently one year of outdoor weathering. The results from three years of weathering are to be used to conclude the study for the development of an evaluation concept. Matching surfaces and AGS, with focus on the surface properties should be defined.
Microscopic analysis of the alkali-silica reactivity of various origin fine aggregate
, , , and
Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawińskiego 5B, 02-106 Warsaw, Poland
Abstract
Alkali silica reaction (ASR) is a harmful phenomenon occurring as a result of chemical interactions between sodium and potassium hydroxides in the pore solution and reactive minerals contained in the aggregate. Reactive minerals like microcrystalline, cryptocrystalline or strained quartz dissolve in the alkaline solution and form an expansive gel product. Proper selection of concrete constituents is necessary to ensure the durability of concrete structures. The proper recognition of the aggregate mineralogical composition is a very important element in the process of selection of concrete components due to the risk of ASR occurrence. This paper presents the results of detailed microscopic analysis of alkali-silica reactivity of domestic fine aggregates of various origins. Six siliceous sands from different locations in Poland and one limestone sand were tested. Detailed petrographic analysis was performed on thin sections. In all siliceous sands micro- and cryptocrystalline quartz was recognized as a reactive mineral. Digital image analysis was performed for quantitative assessment of the potential of reactivity of sands. It revealed, that siliceous river sands were the most susceptible to an alkali-silica reaction, which was confirmed by mortar bar expansion test performed according to the standard test method.
The immobilisation of heavy metals from sewage sludge ash in geopolymer mortars
1, 1, 2, 2 and 1
1 Cracow University of Technology, Faculty of Civil Engineering, Chair of Building Materials, Warszawska 24, 31-155 Cracow, Poland
2 University Beira Interior, Department of Civil Engineering and Architecture, Convento de Sto. António. 6201-001 Covilhã, Portugal
Abstract
Sewage sludge is a semi-solid waste material created as a result of the sewage treatment of industrial or municipal wastewater. Because the laws and regulations of the European Union require not only a reduction in waste generation but also the preparation of waste for reuse and disposal, it is necessary to look for new methods of the application of sewage sludge as part of sustainable waste management. In this study, ash formed as a result of the combustion of sewage sludge from the sewage treatment plant in Płaszów, Krakow in a fluidised bed furnace at a temperature of around 800°C was used. Sewage sludge ash (SSA) contains over 30% SiO2 and approx. 10% Al2O3, which indicates potential applications in geopolymer materials. In this study, samples of geopolymer mortars with a binder containing sewage sludge ash as well as fly ash (FA) and ground granulated blast furnace slag (GGBFS) were prepared. The mechanical parameters were determined after 2, 7, 14, and 28 days. The results show that the sewage sludge ash-based geopolymer shows binding properties at ambient temperature and, depending on the presence of FA and/or GGBFS, the compressive strength varies from 5 to 45 MPa after 28 days. The aim of the research was also to determine the total content of heavy metals (Sb, As, Cr, Cd, Cu, Ni, Pb, Hg, Zn) in the raw materials used and their leachability from the structure of the hardened materials. Immobilisation of heavy metals is very promising. Based on the results of tests, it seems possible to use SSA in geopolymer materials, but not as the main component of the binder.
Influence of fly ash on the pore structure of mortar using a differential scanning calorimetry analysis
, and
Kielce University of Technology, Faculty of Civil Engineering and Architecture, Al. Tysiąclecia PaństwaPolskiego 7, 25-314 Kielce, Poland
Abstract
In the paper a low-temperature thermoporometry using differential scanning calorimetry (DSC) was employed for analyse of influence of siliceous fly ash (FA) on pore structure of non-air-entrained mortars (pore size, connectivity). A method of interpreting a heat flux differential scanning calorimetry records in pore structure was used for this purpose. The results demonstrated that the: (i) fly ash mortars have virtually no pores inaccessible to water, unlike the mortars with plain Portland cement in which inaccessible pores constitute a significant fraction, growing with the increase in w/b; (ii) with a decrease in w/b the ink-bottle volume decreases. Fraction of this pore type is relatively larger in fly ash mortars; (iii) Siliceous fly ash increased the volume of pores greater than 8 nm, in particular in the group with radii larger than 20 nm at all w/b ratios.
Lightweight cementitious composites containing cenospheres and polypropylene fibres after exposure to high temperatures
1 and 2
1 Institute of Structural Analysis, Poznan University of Technology, Poznań, Poland
2 Independent Researcher, Poznan University of Technology Alumnus, Poznań, Poland
Abstract
The paper presents the results of experimental investigation of lightweight cementitious composites with cenospheres (LCCC) exposed to high temperatures. We showed the positive effect of cenospheres on post- fire residual compressive strength in previous papers. This paper focuses on the LCCC with the addition of polypropylene (PP) fibres. Specimens are heated up to 400, 600, 800, 1000 and 1200 °C. Then they are cooled to ambient temperature and their residual flexural and compressive strength is tested. The results are compared with non-heated specimens with compressive strength above 50 MPa. For plain LCCC composites, the results show significant improvement of residual compressive strength in comparison with typical concretes. No significant changes of compressive strength are found after exposure to temperatures up to 600°C – more than 85 % of the residual compressive strength is retained after exposure to this temperature for both mixes. Polypropylene fibres are found to be a successful mean to mitigate spalling without significantly lowering neither ambient nor residual compressive strength. Moreover, designed composite has low density and low thermal conductivity at room temperature.
The effect of temperature on the mechanical properties of hybrid FRP bars applicable for the reinforcing of concrete structures
, and
Warsaw University of Technology, Faculty of Civil Engineering, ul. ArmiiLudowej 16, 00-637 Warsaw, Poland
Abstract
One of the most common causes of the deterioration of concrete structures is the corrosion of steel reinforcement. Reinforcement made from fiber reinforced polymers (FRP) is considered to be an attractive substitution for traditional reinforcement. The most popular FRP reinforcing bars are made of glass fibers. Basalt fiber reinforced polymer (BFRP) is a relatively new material for reinforcing bars. The main drawback of BFRP bars is their low modulus of elasticity. A new type of bar made from hybrid fiber reinforced polymer (HFRP) in which a proportion of the basalt fibers are replaced with carbon fibers can be considered as a solution to this issue; such a bar is presented in this work. The HFRP bars might be treated as a relatively simple modification to previously produced BFRP bars. A different technical characteristic of the fibre reinforced polymer makes the designing of structures with FRP reinforcement differ from conventional reinforced concrete design. Therefore, it is necessary to identify the differences and limitations of their use in concrete structures, taking into account their material and geometric features. Despite the predominance of FRP composites in such aspects as corrosion resistance, high tensile strength, and significant weight reductions of structures – it is necessary to consider the behavior of FRP composites at elevated temperatures. In this paper, the effect of temperature on the mechanical properties of FRP bars was investigated. Three types of FRP bar were tested: BFRP, HFRP in which 25% of basalt fibers were replaced with carbon fibers and nHFRP in which epoxy resin was additionally modified with a nanosilica admixture. The mechanical properties were determined using ASTM standard testing for transverse shear strength. The tests were performed at -20°C, +20°C, +80°C for three diameters of each types of bar.
Impact of admixtures used in underwater concrete on cement hydration process and rheological properties
, , and
Opole University of Technology, Faculty of Civil Engineering and Architecture, Department of Building Materials Engineering, 45-061 Opole, Poland
Abstract
This paper presents test results of the impact of chemical admixtures used in the underwater concrete technology, i.e. a superplasticizer (SP), an anti-wash admixture (AWA) and SiO2 nano- particles (NP) on the cement hydration process, rheological properties and the setting time. The impact of admixtures was tested in combination and separately, with the use of microcalimetry, X-ray diffraction (XRD) and rheology. It was demonstrated that AWA and SP admixtures caused a delay of the hydration process, while the impact of SP was much greater. The above statement was also confirmed by results of rheological tests. Combined application of AWA, SP and NP causes even a larger delay of the hydration process and the increase of paste rheological parameters, with the impact of the superplasticizer particularly visible.
Efficiency of night ventilation in limiting the overheating of passive sports hall
and
Cracow University of Technology, Chair of Building Design and Building Physics, Faculty of Civil Engineering, Warszawska 24, 31-155 Cracow, Poland
Abstract
It is especially difficult to provide optimal microclimatic conditions in sports facilities during summer time. The internal heat gains and an airtight building insulation, combined with high external temperature can easily lead to overheating and upsetting of the body's thermal balance. This article focuses primarily on the effect of natural night ventilation on the thermal comfort in a passive sports hall building. Based on experimental studies of thermal conditions in the hall, a simulation model was made using the Design Builder program. Through simulation analysis, the program considered thermal conditions that arise in various scenarios of natural and mechanical ventilation. Results presented in this article show that the natural ventilation at night in a large volume building is the most effective and the easiest way to reduce overheating in summer.
Effect of the amount of river sediment on the basic properties of cement mortars
, and
Cracow University of Technology, Faculty of Civil Engineering, Chair of Building Materials Engineering, Warszawska St. 24, 31-155 Cracow, Poland
Abstract
According to current legal regulations, bottom sediment in watercourses containing heavy metals are considered dangerous to the environment and should be properly managed after extraction. Due to the well-known excellent ability of the products of cement hydration to immobilize heavy metals, the possibility of utilizing this type of waste products in cement composites was preliminary tested. For this purpose, basic research was carried out on the technological and mechanical characteristics of binders containing sediment from one of the rivers located in Lesser Poland. Standard mortars made of Portland cement CEM I and river sediment dried at 105°C were used for the tests. This supplement replaced cement in the amount of 10%, 20%, 30% and 40% by weight. The technological properties such as: water demand, setting time, consistency and mechanical properties were verified. Compressive and tensile strength at bending of hardened mortars were tested at different curing periods, i.e. after 14, 28 and 90 days. The obtained test results confirm that the fraction of river sediment in the binder in the amount of 10% generally does not adversely affect the properties of mortars, however, its greater amount is reflected in changes in the technological features and in a clear reduction of mechanical properties of the tested mortars.
Composition and selected properties of low pH mortars and concretes for radioactive waste repositories
, , and
National Ilan University Department of Civil Engineering, No.1, Sec. 1, Shennong Rd., I-Lan 260, Taiwan
Abstract
Conventional cementitious materials as tunnel supporting materials are utilised in the construction of the final repository for spent nuclear fuel. However, the use of cementitious material releases alkaline ions from pH12 to pH13 plumed into groundwater. Such a high pH is detrimental to the performance of the bentonite functioning, which may possibly enhance the dissolution and alteration of the fracture buffer and filling materials. Instead, low-pH cementitious materials are being developed for use in geological repositories. This study is aimed at evaluating the usability of low-pH cementitious materials containing 40% silica fume or composites blended with 20% silica fume and 40% fly ash. Engineering properties were analysed and verified through experimental research using the flow, compressive strength, pH measurement and hydraulic conductivity. Test results show that the replacement level with 40% of silica fume or 20% of silica fume and 40% of fly ash was suitable for the mixture of low-pH cementitious. Compared to the compressive strength and water permeability of ordinary cementitious, those of low-pH cementitious enhanced better engineered performances at the age of 91 days. The information is contributed us to establish the long-term durability and environmental requirements of disposal repositories in Taiwan.
The application of optical methods for the assessment of the aesthetic compatibility of architectural concrete
and
Warsaw University of Technology, Faculty of Civil Engineering, Poland
Abstract
Architectural concrete is usually defined as concrete for with the requirements regarding aesthetics of its surface are formulated. The currently applied requirements regarding aesthetics compatibility are mostly based on subjective methods of concrete surface assessment. While it is relatively easy to apply quantitative criteria for components of surface analysis such as porosity, the quantitative assessment of colour compatibility could be problematic. In this paper, an optical method for the assessment of concrete surface colour is presented. The main goal of the investigation was to assess the effect of modifications of the aggregate used for preparation of architectural concrete mix on the surface colour. Optical test methods using a self-made DARK-BOX device were used. The obtained results confirmed the usefulness of the method used to assess the colour compatibility of architectural concrete surfaces.
The influence of moisture on the energy performance of retrofitted walls
1, 1, 2, 3 and 4
1 University of Porto, CONSTRUCT-LFC, Faculty of Engineering (FEUP), Portugal
2 University of Coimbra DEC-FCTUC, ADAI-LAETA, Itecons, Portugal
3 Cracow University of Technology, Poland
4 Ryerson University, Toronto, Canada
Abstract
The renovation of old building facades should be performed mainly considering the building energy demand reduction. For this purpose, it is necessary to select retrofitted solutions that should be able of minimizing heat losses through walls. However, it is not only the nominal thermal transmittance that influences the amount of heat transported through the wall, but also the moisture content within the walls under in- service conditions. The main objective of this paper is the evaluation of the influence of the moisture content on the energy performance of retrofitted walls. A numerical study using the software WUFI Pro was carried out to quantify the influence of wind driven rain on the thermal transmittance of different wall assemblies exposed to different climates and orientations. This study reports the transient thermal transmittance of different retrofitted wall solutions as a function of moisture content.
Assessment of environmental impact of coarse aggregates substitution by crushed pavements in concrete mixtures
1, 1, 1 and 2
1 Czech Technical University in Prague, Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Thákurova 7/2077, 166 29 Prague 6, Czech Republic
2 Cracow University of Technology, Building Materials Engineering, Faculty of Civil Engineering, 24 Warszawska St., 31-155 Cracow, Poland
Abstract
Inefficient use of end-of-life materials in combination with depletion of primary sources can be understood as a significant factor that motivates to effective waste material recycling and reuse. Since the construction industry produces millions of tons of building materials, which are continuously reaching their service life end, there is a great potential for their reuse instead of simple landfilling. In this light, concrete is a versatile building material that might incorporate lots of recycled building materials as it is demanding on primary sources. A substitution of coarse aggregates by recycled products is, therefore, one of the ways how to mitigate these environmental burdens. This paper aims at evaluation of environmental contributions of concrete with coarse aggregates being substituted by crushed concrete pavements. Various amounts of recycled aggregates were assumed (0%, 50%, and 100%) to reveal the environmental impacts. The analysis incorporates all inputs and outputs related to the production of concrete and recycling of concrete pavements (raw materials production, processing, transport emissions, energy production, etc.). The results indicate that substitution of coarse aggregates by recycled concrete pavements may bring significant mitigation of environmental impacts and hence it deserves further investigation.
Micromechanical modelling of damage induced by delayedettringite formation in concrete
, , and
GeM, UMR CNRS 6183, Université de Nantes, Ecole Centrale Nantes, 44600 Saint-Nazaire, France
Abstract
A multi-scale poromechanical model of damage induced by Delayed Ettringite Formation (DEF) as a consequence of progression of micro-cracks at the fine aggregate scale is developed. The aim is to link the DEF-induced expansion at both the microscopic and macroscopic scales to the loss of stiffness of the mortar and the increase of its diffusion coefficient. At the microscopic scale, mortar is assumed to be constituted of three phases: cement paste, sand and micro-cracks. Damage is assumed to be driven by a free expansion of cement paste due to ettringite crystallization pressures in small capillary pores, at a lower scale. The corresponding homogenised poroelastic properties are estimated along with the diffusion coefficient by resorting either to a Mori-Tanaka scheme or to a self-consistent scheme, as a function of paste and aggregate properties as well as on the density of micro-cracks. The latter is assumed to be an evolving internal variable in order to model DEF-induced damage in the mortar. As the DEF-induced expansive free strain in the cement paste is restrained by the sand particles, internal stresses arise in the mortar. The corresponding free energy can be partially released by an increase in the micro-cracks density by analogy with the energy restitution rate of linear elastic fracture mechanics. The role of the damage criterion adopted on the thermodynamic force associated with micro-cracks density increase is investigated.
The analysis of cracking risk by shrinkage restraint of an alkali-activated slag mortar
1,2, 3, 4, 1 and 2
1 Université Paris-Saclay, CEA, DEN-Service d’Etude du Comportement des Radionucléides (SECR), F-91191, Gif-sur-Yvette, France
2 Université Paris-Saclay, CNRS, ENS Paris-Saclay LMT, 94235 Cachan, France
3 INSA Rennes, 20 Avenue des Buttes de Coesmes, 35000, Rennes, France
4 Orano, NWM, Technical Department, 125 Rue de Paris, 92320 Chatillon, France
Abstract
Alkali-activated slag (AAS) binders show in general larger autogeneous shrinkage strains than ordinary Portland cement (OPC) based binders. However, AAS can be a relevant alternative to OPC, if, for example low hydration heat release and fine pores, are required. This study proposes an evaluation of the advantage of using AAS materials in small-sized or massive structures with regard to cracking risk by autogeneous shrinkage and thermal strains. A cracking risk index is calculated; this risk is defined as the ratio between stress generated by full restraint and tensile strength. All required experimental data were investigated in an OPC and AAS mortar, these are: heat release, autogeneous shrinkage, Young’s modulus, tensile strength and basic creep evolutions. The material parameters of a rate-dependent model developed in 1D were then identified. Numerical simulations were then performed for different thicknesses in full-restraint conditions. These show that, as expected, basic creep is a very important material parameter to assess. Indeed, basic creep enables the significant reduction of the generated stresses. Besides, it is found that the more the structure is large (and sensitive to cracking by risk by thermal strain), the more the AAS material is becoming appropriate compared to the OPC material.
1, 2 and 1,3
1 Federal Center for Technological Education CEFET/RJ, 20271-110, Rio de Janeiro, Brazil
2 University of Nantes, Research Institute of Civil and Mechanic Engineering, 44600, Saint Nazaire, France
3 GeM Institute, UMR 6183 CNRS, CESI, Saint-Nazaire, France
Abstract
Concrete is a major construction material that produces high levels of carbon dioxide in its manufacturing process. Hence the construction sector is responsible for relevant environmental impacts. This justifies the need to find materials as green and ecological alternatives to common Portland cement. Geopolymers represent the most promising alternative due to its proven durability, mechanical and thermal properties. This study investigates the effects of solid-to-liquid and alkali activator ratios on the synthesis of slag-based pure geopolymer and their relation to the geopolymerization process. Two activating solutions were used: a) a mixture of sodium hydroxide, sodium silicate, and water; and b) a mixture of potassium hydroxide solution, potassium silicate, and water. As precursor material, ground blast furnace slag was used. Precursors and activators were mixed with solid-to-liquid ratios in range of 1.5 to 2.2. In the first stage of the study, the mechanical properties were evaluated for each activating solution. In the following stage, different formulations, with variations in the water percentage and solid-to-liquid ratio were tested for mechanical properties and SEM observations. Test results indicate that the resulting geopolymer has the potential for high compressive strength and is directly affected by the composition of the activating solution. It can also be observed that compressive strength was affected by solid-to-liquid ratio and % of water added to the mixture, and strength increased with ageing day.
Silesian University of Technology, Faculty of Building Engineering, Department of Building Processes and Building Physics, Akademicka 5 str., 44-100 Gliwice, Poland
Abstract
Theoretically, high-performance concrete with w/c ratio about 0.30 and w/b about 0.28 should have low porosity, low water permeability and high strength. The purpose of this study was to examine the influence of the superplasticizers( with and without air-entraining effect) and shrinkage reducing admixture based on a high molecular weight basis alcohol amount on the air-content, compressive strength, shrink and resistance to water penetration of high-performance self-compacting concrete (HPSCC). The test results have shown that despite the low water content, concrete modified with inadequately selected SP and high amount of SRA has a high porosity and low strength and water permeability. The types of superplasticizers and amount of SRA are significant due to porosity parameters, compressive strength and water-permeability of HPSCC. The water permeability and compressive strength of HPSCC depending on the effects of amount of SRA admixtures on the volume of pores in HPSCC. Moreover, shrinkage of incidental air-entrained concrete, despite its lower endurance, after 28 days of hardening it is smaller than non-aerated concrete.
Chilean Construction Institute: building consensus in coordinating common issues
University of Chile, Faculty of Architecture and Urbanism, AvenidaLibertador Bernardo O'Higgins 1058, Santiago, Chile
Abstract
The twenty years of research experience of the Chilean Construction Institute (IC) to promote “public and private efforts to improve quality, productivity and sustainability in construction” are presented in this paper. IC is a non-profit organisation formed by some public, private and academic actors: two ministries, two universities (Universidad de Chile and Universidad Católica de Chile) the Chilean Construction Chamber, three guilds (Architects, Builders and Engineers) and private industries (from the materials sector) formed this very atypical organisation back in the nineteen-nineties. The IC is a transverse association in which the actors meet freely to discuss issues that affect the construction sector, trying to find common proposals to contribute regarding the development of the country. Important actions have been developed, such as the Chilean isolation regulation; the social housing pathologies study; the National Construction Norms Council; the Chilean construction norms site; the public buildings case study; the CES - Chilean building certification system; the digitalisation of the building authorization system (on the municipal level); the Regional Seismic Code (for all Latin American and Caribbean countries) and others impossible to include here. This effort has proved to be effective and efficient in order to promote regulation upgrading and conduct studies that would otherwise be difficult to do. An interesting case is the thermal isolation regulation: with the support of the academic world, it was possible to agree a common starting point which, at the beginning, was strongly opposed by some actors. This updated regulation has proven that this public-private and academic joint venture is reliable and effective. Two cases are discussed in detail in this document.
Considerations on design, development and testing of Electrical Machines for automotive HVAC
, , and
Technical University of Cluj-Napoca, 400114 Memorandumului 28, Cluj-Napoca, Romania
Abstract
HVAC represents one of the highest energy consumer in a vehicle and for full electric vehicles, the design of HVAC and the dimensioning of its driving system is of utmost importance in order to avoid the limitation of driving range. Due to its advantages, especially when it comes to power density, PMSM is one of the most used electrical machines for a wide range of automotive applications, including HVAC systems. The paper presents the generation of the requirements, design, analysis and HiL testing of a PMSM for HVAC applications. The challenge is to develop a machine answering to the requirements for an electric vehicle HVAC at low- voltage. An experimental model of the machine was tested using a test- bench, based on HiL techniques.
Mechanical behaviour and permeability of geopolymer mortars
1, 2, 1 and 2
1 Cracow University of Technology, Faculty of Civil Engineering, Chair of Building Materials, Warszawska 24, 31-155 Cracow, Poland
2 Nantes University - IUT Saint-Nazaire, Research Institute in Civil and Mechanical Engineering GeM – UMR CNRS 6183, 58, rue Michel Ange, 44 600 Saint Nazaire, France
Abstract
Geopolymers may be considered as an alternative materials to Portland cement ones, providing an opportunity to exploit industrial wastes or co-products with promising short and long-term performances in the construction field, f.ex. for reparation issues. However, these materials are porous and consequently their durability depends on the risk of intrusion of aggressive agents. In order to assess their durability, we propose to investigate in this study gas permeability of sound and mechanically loaded specimens. Loading is performed using a splitting tensile test driven by a crack opening displacement up to a level of 50 microns. Tests are performed on four types of blended fly-ash (FA) and ground granulated blast furnace slag (GGBFS) geopolymer mortars, containing four different levels of GGGBF slag in the binder: 0%, 10%, 30% and 50% wt. Results show a positive effect of blending with slag in terms of modulus of elasticity and tensile and compressive strength, as well as the permeability. However, permeability recovery after cracking is the lowest when blending is the highest.
Hydrogen diffusion through polymer membranes
1, 1, 1, 2 and 1
1 Univ Lille, CNRS, Centrale Lille, LamCube FRE 2016, F-59000, Lille, France
2 Univ Lille, CNRS, Centrale Lille, ENSCL, Univ Artois, UCCS UMR 8181, F-59000 Lille, France
Abstract
This experimental study determines H2 transfer properties of High Density PolyEthylene (HDPE) or epoxy membranes. Two different techniques are compared. The pressure gradient technique is analyzed for permeability or diffusion. Results show that the main phenomenon involved is diffusion. The second technique involves a gas concentration gradient. Although implying significantly slower kinetics, this classical technique is consistent with results obtained with the faster pressure gradient technique.
Drying Shrinkage and Cracking Tendency of Concrete Pavement Mixtures with Variable Packing Densities of Aggregates and Paste Contents
1 and 2
1 Purdue University, Lyles School of Civil Engineering, West Lafayette, IN 47907, USA
2 LafargeHolcim Innovation Center, 38291 Saint-Quentin Fallavier, France
Abstract
Excessive drying shrinkage, and associated cracking, can lead to serious durability problem in concrete pavements and bridges. In the course of this study, the magnitude of drying shrinkage and cracking potential was evaluated for several concrete pavement mixtures as a function of packing density of the aggregate and paste contents. The results indicated that both, the shrinkage and the cracking potential depend on the volume of voids between aggregate particles (packing density), paste content of concrete mixture, and the paste-aggregate void saturation ratio.
The particularities of near-critical flows formation in open channels
, , and
National University of Water and Environmental Engineering, Rivne, Soborna St. 11, 33028, Ukraine
Abstract
This article considers the current problems of near-critical flows. It provides short characteristics of each phenomenon and describes the cases of near-critical flow formation during the operation of the different hydraulic structures. Each of the considered phenomena has a number of characteristic features which distinguish them from the usual subcritical and supercritical flows with smooth or slowly varied movement. Such properties include the wave-like or roller nature of free-surface curves, the presence of a streamline inclination and curvature, and also a non-hydrostatic pressure distribution in depth mainly in the vertical cross-section of these phenomena. Therefore, during mathematical and numerical simulations at the designing stage of hydraulic structures it is necessary to take into account the additional parameters which characterise the particularities of near-critical flows. In cases in which these moments are neglected, there are many cases of accidents and damage being caused to structures which are operated in conditions of near-critical flow formation. An objective of this work is to provide a detailed analysis of the particularities of near-critical flows and show their negative consequences on hydraulic structures. The article presents the results of the mathematical and hydraulic simulation of wavelike near-critical flows and a comparison of the full-scale measurement and a mathematical model of translation waves.
The prognostic modelling of piezometric levels based on seepage monitoring in earthen dams
1* and 1,2
1 National University of Water and Environmental Engineering, Hydraulic construction andHydraulics Department, 33028 Rivne, Ukraine
2 Institute of Telecommunications and Global Information Space, 03186 Kyiv, Ukraine
Abstract
This paper presents an innovative approach to the prognostic modelling of piezometric levels in earthen dams equipped with automated monitoring systems. The main idea of the approach and the expected prognostic results are illustrated with the example of prediction of piezometric levels in the earthen dam of the Kyiv hydropower plant. This usually complex prediction task is simplified in this approach by means of simple regression models and combined situational and inductive modelling which enables overcoming the excessive uncertainty in time series. To calibrate the interpretation and prognostic models, daily monitoring data of the piezometric levels over a period of eight years was used. To verify the prediction results, monitoring data collected in the three years following this eight-year period was used. The goodness of fit of interpretation models was performed by R2 testing. To assess the goodness of the prediction fit, mean absolute and relative error estimators, as well as the Nash-Sutcliffe efficiency coefficient, were employed.
Hybrid imaging-AI approach for handling critical situations in a fast-changing environment: preliminary study
Cracow University of Technology, Warszawska 24, 31-155 Cracow, Poland
Abstract
The purpose of this study is to explore the possibility of using selected imaging technologies in automated video surveillance systems. The main goal of this project is to handle events that may lead to security risks, injuries, etc in various environments without relaying on more conventional sensors such as infrared photocells. For this purpose it is necessary to perform a thorough analysis of the events to be interpreted as situations of interest. It is also important to consider the hardware requirements and restrictions for developing such system. The project requires defining a hardware as well as software platform(s) and their integration into an automated tool. This paper describes the implementation of the famous Microsoft Kinect 2.0 depth sensor (well known in gaming and recreational applications) for shape/skeleton detection, and its integration into an artificial intelligence based platform utilizing selected machine learning methods. The author reveals the system implementation details, and then demonstrates its shape detection capabilities while in operation.
The magnetic circuit dynamics of a magnetorheological valve with a permanent magnet
*, and
Brno University of Technology, Institute of Machine and Industrial Design, Technická 2, Brno, Czech Republic
Abstract
The magnetorheological (MR) damper uses magnetorheological fluid which, when subjected to magnetic stimuli, generates an increase of damping forces. A significant problem of these dampers is their poor failsafe ability due to power supply interruption. In the case of faults, the damper remains in a low damping state, which is dangerous. This problem can be solved by accommodating a permanent magnet in the magnetic circuit of the damper. However, the magnetic circuit dynamic of this type of damper has rarely been studied. The main aim of this paper is to introduce the magnetic circuit dynamics of the magnetorheological damper/control valve with a permanent magnet. Firstly, the design of the magnetorheological valve with NdFe42 permanent magnet in the magnetic circuit is introduced. The response time of the magnetic field on the unit step of the control signal was calculated by transient magnetic simulation in Ansys Electronics software. The response time of the magnetic field was simulated in the range of 1.2 to 5 ms depending on the electric current magnitude and orientation. The presented MR damper was manufactured and tested. The experiments prove that the permanent magnet significantly affects the dynamics of the magnetic circuit.
State of the art of soft robotic applications based on magneto-rheological materials
Cracow University of Technology, Warszawska 24, 31-155 Cracow, Poland
Abstract
Soft robotics is a new and exciting field of robotics which heavily relies on compliant materials. Soft robots attempt to copy the motion of living organisms and their adaptation mechanisms to the environment. New efforts in this field have paved way for the use of specific materials, e.g. electroactive polymers and/or magnetoactive (magnetorheological) MR elastomers. In this paper the author discusses the fundamental characteristics of MR fluids and elastomers, that allow them to be used as elements/components of soft robots. The advantages of using soft robots and the scope of applications for such robots are presented. The advantages and disadvantages of using MR fluids and elastomers in such soft robots are also considered. The history of the development of the idea of using MR fluids and elastomers in soft robots is presented, too. Possible applications for soft robots based on MR fluids and elastomers are considered. Various solutions for constructing a robotic gripper using MR fluids and elastomers are presented. Based on the above solutions, an analysis is made of the development of such technologies and the main problems are identified that will be the goal of solving them in the near future.
Sprung mass positioning by semi-actively controlled damper
and
Institute of Machine and Industrial Design, Brno University of Technology, Technická 2898/2, 616 69 Brno
Abstract
Recently, the intensive wear of rails, especially in curves of small radii and at switches, has been studied. The wear is caused by the high lateral force peak of the wheel against the rail when entering the curves. An effective solution for reducing undesirable lateral forces on the rail is to rotate the vehicle bogie in the direction of the rail curve, which influences the distribution of lateral force over the first and second wheelset. This reduces the force peak and thus the track wear. The bogie rotation is nowadays realized by actuators, which replace the yaw dampers. However, actuator implementation is complicated, expensive, energyintensive and demanding for the performance of a fail-safe system. From this point of view, a semi-actively controlled yaw damper appears to be a better candidate. An algorithm such as Skyhook can hold the sprung mass in the desired position. It is believed to be possible to rotate the vehicle bogie by the special S/A control strategy of a yaw damper. This paper deals with the possibilities and limits of the positioning of the sprung mass by the semi-actively controlled damper. It has been shown that the system relative attenuation and the damper response time have the greatest influence on the mass positioning efficiency.
Coupled Electromagnetic and Thermal Analysis of Electric Machines
1,2, 1 and 2
1 Research Centre in Digitalization and Intelligent Robotics (CeDRI), InstitutoPolitécnico de Bragança, Portugal
2 Federal University of Technology – Parana (UTFPR), Toledo, Brazil
Abstract
This paper deals with the design process of electric machines, proposing a design flowchart which couples the electromagnetic and thermal models of the machine, assisted by finite element techniques. The optimization of an electrical machine, in terms of the energy efficiency and cost reduction requirements, benefits from the coupling design of the electromagnetic and thermal models. It allows the maximization of the current density and, consequently, the torque/power density within thermal limits of the active materials. The proposed coupled electromagneticthermal analysis is demonstrated using a single-phase transformer of 1 kVA. Finite element analysis is carried out via ANSYS Workbench, using Maxwell 3D for the electromagnetic design, with resistive and iron losses directly coupled to a steady-state thermal simulation, in order to determine the temperature rise which, in turn, returns to electromagnetic model for material properties update.
The modelling of the measuring point reproduction error for optical coordinate measuring machines
1, 2, 1, 1 and 1
1 Cracow University of Technology, Laboratory of Coordinate Metrology, al. Jana Pawla II 37, 31-864 Cracow, Poland
2 NTB Interstate University of Applied Science, Werdenbergstrasse 4, CH-9471 Buchs, Switzerland
Abstract
Coordinate measuring machines (CMMs) are the most common measuring systems used for assessing the compliance of manufactured components with their geometrical specifications. Optical CMMs are currently gaining popularity as they enable fast and contactless measurement with accuracy almost as high as in case of tactile measurement. During the performing of measurement, the points at which the measurement is conducted are usually not exactly at the intended location, but due to different impacts (error sources), they are in the area surrounding this location. This paper presents a method for modelling the reproduction of point coordinates as probability ellipses geometrically limiting the area in which the actual measurement points may lie. Different mathematical algorithms for the description of these ellipses were examined and a discussion on the selection of the best method is presented in this paper.
Stator Winding Fault Detection Using External Search Coil and Artificial Neural Network
1,2, 2*, 1, 2 and 1
1 Federal Technological University of Paraná, CornélioProcópio, Paraná, Brazil
2 Research Centre in Digitalization and Intelligent Robotics (CeDRI), InstitutoPolitécnico deBragança, Portugal
Abstract
This paper presents a methodology for winding stator fault detection of induction motors, using an external search coil, which is a noninvasive technique and can be applied during motor operation. The dispersion magnetic flux of the motor operating in abnormal conditions induces a voltage in the search coil that differs from a reference pattern corresponding to the healthy stator winding. Experimental data were obtained in a test bench using a 0.75 kW three-phase squirrel-cage induction motor with the stator winding modified to allow the introduction of short circuits. This work considered short circuits in one phase, involving 1%, 3%, 5% and 10% of the turns, with the motor loaded with a varying torque. Fault diagnosis is obtained through two models of artificial neural networks, implemented with the signals in the time domain. The obtained results demonstrated that the developed methodology presents difficulties in predicting short circuits in incipient stages, but for short circuits of higher severity, the behaviour improved substantially, being 100% successful for faults with 10% turns short-circuited.
Adverse impact of municipal solid waste transportation on collected stormwater biosolids quality
1 and 2
1 Cracow University of Technology, Faculty of Environmental Engineering and Energetics, Warszawska 24, 31-155 Krakow,
2 Technical University of Berlin
Abstract
The objective of this paper was to identify possible specific contamination of stormwater biosolids, with a special emphasis on pollution associated with transportation of municipal solid wastes to the waste utilization plant. The study area for sampling includes two selected points of separate stormwater collection system in Cracow. Samples of stormwater and biosolids were collected during spring-summer-autumn season addressed towards rainy days to check the scope of the problem The results led to conclusion, whether the waste utilization plant impacts the stormwater quality, compared to the high-traffic road. The largest pollutants found in stormwater near the plant were nutrients (nitrogen, phosphorus) however general content of organic matter in biosolids collected in separated stormwater system also confirmed adverse impact of solid waste transportation on stormwater sludge (biosolids) quality.