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Zbyněk Keršner - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Fracture properties of concrete with lunar aggregate simulant
MATEC Web of Conferences, 2020Co-Authors: Stanislav Seitl, Zbyněk Keršner, Iva Rozsypalová, Petr Miarka, Katka Pokorná, Jacek Katzer, Paweł K. ZarzyckiAbstract:From the volumetric point of view, aggregate is the most important ingredient in any kind of concrete. It is impossible to use raw soil instead of aggregate to produce concrete. There are numerous reasons for not using soil for concrete production on Earth, and we should not use lunar soil for concrete production on the Moon for the same reasons. Nevertheless, almost all developed lunar concrete-like composites, such as sulphur or polymeric concretes, are based on raw lunar soil. In the research programme, cement composite based on lunar aggregate simulant was tested. The Mechanical Fracture properties of the composite were the key point of interest. It was proven that the tested lunar concrete is characterized by stable and uniform properties. The obtained results were compared with the properties of other ordinary cement composites.
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Change of Fatigue and Mechanical Fracture Properties of a Cement Composite due to Partial Replacement of Aggregate by Red Ceramic Waste
Periodica Polytechnica Civil Engineering, 2019Co-Authors: Stanislav Seitl, Zbyněk Keršner, Hana Simonova, Petr Miarka, Petr Frantík, Jacek Domski, Jacek KatzerAbstract:Fine-grained cement-based composites used in civil engineering and construction industry are usually made of cement-based matrix and natural aggregate (such as sand, gravel, crushed stone, etc.). Red ceramic waste aggregate is considered as a perspective replacement of a part of natural aggregate in modern environmentally oriented building materials. Fine-grained cement composite with natural aggregate partially replaced by ceramic waste aggregate usually show different Mechanical Fracture characteristics from ordinary fine-grained concrete. The specimens were tested at six different ages. This was the reason for conducting the research programme. Altogether, 6 fine-grained cement mixtures with various proportions of natural and red ceramic waste aggregate were prepared. The aim of this paper is to present and compare Mechanical Fracture properties obtained from static and fatigue tests. Bulk density, flexural and compressive cube strength, Fracture toughness and fatigue properties (S−N − Wöhler curve) were of special interest. All of these tests are important for a practical application of concrete with ceramic aggregate for structures. All the results were statistically analysed and they showed that the fatigue and Mechanical Fracture properties were improved or at least kept up with the increasing levels of red ceramic waste aggregate. Environmental impact of application in construction industry of composites in question is discussed.
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Fracture Response of Fine-Grained Cement-Based Composite Specimens with Special Inclusions
Solid State Phenomena, 2019Co-Authors: Michal Vyhlídal, Hana Simonova, Barbara Kucharczyková, Petr Daněk, Iva Rozsypalová, Tomáš Majda, Zbyněk KeršnerAbstract:This paper concerns research into the importance of the interfacial transition zone around inclusions of selected materials in fine-grained cement-based composite. Tests were performed on eight sets of prismatic test specimens. The sets differed in the inclusion materials used, which were placed at midspan above the initial central edge notch. The first was a reference set without any inclusion, the second contained a steel inclusion, four more contained different types of rock inclusion, the seventh contained an inclusion of extruded polystyrene, and the last contained a space of the same dimensions as that occupied by the inclusions in sets 2 to 7. The test specimens were subjected to three-point bending Fracture tests at the age of (usually) 28 days. The Fracture response was analysed by means of Fracture mechanics theory, and apparent Mechanical Fracture parameters (modulus of elasticity, Fracture toughness and Fracture energy) were evaluated. The conclusion shows that a possible relationship exists between the differences in the Mechanical Fracture parameters of specimens with/without an inclusion and the existence of the interfacial transition zone.
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Calculation of Mechanical Fracture Parameters of Chevron Notched Core Based Concrete Specimen: Software CheF
Solid State Phenomena, 2018Co-Authors: Barbora Svobodova, Hana Simonova, Zbyněk KeršnerAbstract:The structural concrete can be also characterized via parameters obtained by evaluation of Fracture tests. Therefore, this paper presents software CheF developed in Java programming language, designed for evaluation of three-point bending Fracture tests of core based concrete specimens with chevron type notch. The records of Fracture tests in form load vs. displacement and load vs. crack mouth opening displacement diagrams are analysed by software CheF to obtain values of selected Mechanical Fracture parameters: modulus of elasticity E, Fracture toughness KIc, and Fracture energy GF, determined based on the linear elastic Fracture mechanics approach and work-of-Fracture method.
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Detailed Determination of Mechanical Fracture Parameters of Concrete after Fire Experiments
Solid State Phenomena, 2018Co-Authors: Hana Simonova, Petr Daněk, Tomáš Trčka, Michal Bejček, Iva Rozsypalová, Zbyněk KeršnerAbstract:The aim of this paper is to describe the procedure of determining the Mechanical Fracture parameters of selected concrete specimens taken from panels after the fire experiments. The records (in form load vs displacement diagrams) of three-point bending Fracture tests of these specimens with initial stress concentrators was first advanced corrected and subsequently evaluated using the Effective Crack Model and the work-of-Fracture method. The increasing temperatures during the fire experiments ranging between 550 to 1000 °C led to a decrease of modulus of elasticity and Fracture toughness values and to the increase of Fracture energy value. The 2D laser profile scanner was used to estimate the degree of complexity of Fracture surfaces; its statistical dependence on the Mechanical Fracture parameters proved to be moderate – the absolute value of the correlation coefficient was about 0.5°[–].
Hana Simonova - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Fracture and Fatigue Characteristics of Fine-Grained Composite Based on Sodium Hydroxide-Activated Slag Cured under High Relative Humidity
Applied Sciences, 2020Co-Authors: Hana Simonova, Barbara Kucharczyková, Vlastimil Bílek, Petr Miarka, Lucie Malíková, Martin LipowczanAbstract:A typical example of an alternative binder to commonly used Portland cement is alkali-activated binders that have high potential as a part of a toolkit for sustainable construction materials. One group of these materials is alkali-activated slag. There is a lack of information about its long-term properties. In addition, its Mechanical properties are characterized most often in terms of compressive strength; however, it is not sensitive enough to sufficiently cover the changes in microstructure such as microcracking, and thus, it poses a potential risk for practical utilization. Consequently, the present study deals with the determination of long-term Mechanical Fracture and fatigue parameters of the fine-grained composites based on this interesting binder. The Mechanical Fracture parameters are primarily obtained through the direct evaluation of Fracture test data via the effective crack model, the work-of-Fracture method, the double-K Fracture model, and complemented by parameter identification using the inverse analysis. The outcome of cyclic/fatigue Fracture tests is represented by a Wöhler curve. The results presented in this article represent the complex information about material behavior and valuable input parameters for material models used for numerical simulations of crack propagation in this quasi-brittle material.
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Complex multilevel Fracture tests of concrete: basic Mechanical Fracture parameters of standard size specimens
MATEC Web of Conferences, 2020Co-Authors: David Lehký, Hana Simonova, Barbara Kucharczyková, Petr DaněkAbstract:The aim of the current research is to develop a complex multilevel approach for the experimental–computational determination of Mechanical Fracture parameters of concrete as a typical quasi-brittle material. This includes testing, advanced evaluation and soft computing-based identification of specimens of multiple sizes in multiple test configurations and analyses of Fracture processes using multiscale modelling approaches. The evaluation of a part of an extensive experimental program is presented in this paper. The basic Mechanical Fracture parameters of the investigated concrete determined on standard test specimens with nominal dimensions of 100 × 100 × 400 mm subjected to the standard three-point bending Fracture test are introduced. The results of three different sets of specimens provided with different depths of the initial notch are compared in terms of absolute values of the selected Mechanical Fracture parameters. The results indicate different sensitivity of particular Mechanical Fracture parameters in relation to the depth of the initial notch.
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Change of Fatigue and Mechanical Fracture Properties of a Cement Composite due to Partial Replacement of Aggregate by Red Ceramic Waste
Periodica Polytechnica Civil Engineering, 2019Co-Authors: Stanislav Seitl, Zbyněk Keršner, Hana Simonova, Petr Miarka, Petr Frantík, Jacek Domski, Jacek KatzerAbstract:Fine-grained cement-based composites used in civil engineering and construction industry are usually made of cement-based matrix and natural aggregate (such as sand, gravel, crushed stone, etc.). Red ceramic waste aggregate is considered as a perspective replacement of a part of natural aggregate in modern environmentally oriented building materials. Fine-grained cement composite with natural aggregate partially replaced by ceramic waste aggregate usually show different Mechanical Fracture characteristics from ordinary fine-grained concrete. The specimens were tested at six different ages. This was the reason for conducting the research programme. Altogether, 6 fine-grained cement mixtures with various proportions of natural and red ceramic waste aggregate were prepared. The aim of this paper is to present and compare Mechanical Fracture properties obtained from static and fatigue tests. Bulk density, flexural and compressive cube strength, Fracture toughness and fatigue properties (S−N − Wöhler curve) were of special interest. All of these tests are important for a practical application of concrete with ceramic aggregate for structures. All the results were statistically analysed and they showed that the fatigue and Mechanical Fracture properties were improved or at least kept up with the increasing levels of red ceramic waste aggregate. Environmental impact of application in construction industry of composites in question is discussed.
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Fracture Response of Fine-Grained Cement-Based Composite Specimens with Special Inclusions
Solid State Phenomena, 2019Co-Authors: Michal Vyhlídal, Hana Simonova, Barbara Kucharczyková, Petr Daněk, Iva Rozsypalová, Tomáš Majda, Zbyněk KeršnerAbstract:This paper concerns research into the importance of the interfacial transition zone around inclusions of selected materials in fine-grained cement-based composite. Tests were performed on eight sets of prismatic test specimens. The sets differed in the inclusion materials used, which were placed at midspan above the initial central edge notch. The first was a reference set without any inclusion, the second contained a steel inclusion, four more contained different types of rock inclusion, the seventh contained an inclusion of extruded polystyrene, and the last contained a space of the same dimensions as that occupied by the inclusions in sets 2 to 7. The test specimens were subjected to three-point bending Fracture tests at the age of (usually) 28 days. The Fracture response was analysed by means of Fracture mechanics theory, and apparent Mechanical Fracture parameters (modulus of elasticity, Fracture toughness and Fracture energy) were evaluated. The conclusion shows that a possible relationship exists between the differences in the Mechanical Fracture parameters of specimens with/without an inclusion and the existence of the interfacial transition zone.
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Calculation of Mechanical Fracture Parameters of Chevron Notched Core Based Concrete Specimen: Software CheF
Solid State Phenomena, 2018Co-Authors: Barbora Svobodova, Hana Simonova, Zbyněk KeršnerAbstract:The structural concrete can be also characterized via parameters obtained by evaluation of Fracture tests. Therefore, this paper presents software CheF developed in Java programming language, designed for evaluation of three-point bending Fracture tests of core based concrete specimens with chevron type notch. The records of Fracture tests in form load vs. displacement and load vs. crack mouth opening displacement diagrams are analysed by software CheF to obtain values of selected Mechanical Fracture parameters: modulus of elasticity E, Fracture toughness KIc, and Fracture energy GF, determined based on the linear elastic Fracture mechanics approach and work-of-Fracture method.
Pavla Rovnaníková - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Fracture Parameters of Cement Based Mortars with Waste Glass Powder
Procedia Engineering, 2017Co-Authors: Hana Simonova, Pavla Rovnaníková, Zbyněk Keršner, Jana Zahálková, Patrik Bayer, Pavel SchmidAbstract:Abstract Glass is an amorphous solid substance with pozzolanic properties that can be used as a partial substitute for ordinary Portland cement (OPC) in cement based composites. In the research conducted for this paper, the PC was partially replaced by fine-ground waste laboratory borosilicate glass (in mixtures where 5, 10, 15 and 20% by mass was substituted). Beam specimens with the dimensions 40 × 40 × 160 mm were prepared from each mixture. After demoulding, the specimens were kept under standard laboratory conditions. Basic tests were conducted at the age of 7, 28, 56, and 90 days: the compressive ( f c ) and flexural ( f f ) strengths were determined according to the CSN EN 1015-11 standard. Specimens were also subjected to Fracture testing at the age of 28 days. The beam specimens with an initial central edge notch were tested in three-point bending. Load vs. displacement diagrams were recorded and modulus of elasticity ( E ), Fracture toughness ( K Ic e ) and Fracture energy ( G F * ) were determined. It was found, that strength increased with specimen age: at the age 28 days this increase was 12–33% in case of f c , and 6–15% as regards f f . The values obtained for almost all the parameters decreased with the increasing dosage of glass as a replacement for cement: compared to a reference composite this decrease was 22–40% in the case of f c , 24–28% for f f , 3–5% for E , 9–29% for K Ic e , and 30–50% for G F * ; exceptions were recorded for glass replacement doses of 5 and 10%, where increases of 2–6% for f c and 8–10% for E were obtained.
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Effect of Amorphous Silicon Dioxide Amount on the Mechanical Fracture Parameters of Cement Mortars
Solid State Phenomena, 2016Co-Authors: Hana Simonova, Pavla Rovnaníková, Zbyněk Keršner, Jana Zahálková, Pavel SchmidAbstract:This paper presents selected results from a study concerning Mechanical Fracture parameters related to the formation of the solid structure of cement mortars. The tested mixtures were composed of an invariable quantity of cement (type CEM I 42.5 R) and an increasing amount of amorphous SiO2 (marked with a P), or a variable quantity of cement replaced by varied quantities of amorphous SiO2 (marked with an N). It was decided that the consistencies of the fresh mixtures should be identical: to ensure this, the water-cement ratio was increased as necessary. Quantification of the Mechanical Fracture parameters of the studied composites (Fracture toughness, Fracture energy, compressive strength, modulus of elasticity) was performed via the evaluation of Fracture tests performed on beam specimens with an initial stress concentrator loaded in three-point bending. Subsequently, the results of the experiments in the form of load versus displacement diagrams were processed using the effective crack Fracture model and the work of Fracture method.
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Mechanical Fracture Properties of Cement Mortars with Diatomite in Relation to their Microstructure
Advanced Materials Research, 2015Co-Authors: Pavla Rovnaníková, Hana Simonova, Pavel Schmid, Ivana Havlíková, Jana Zahálková, Patrik Bayer, Zbyněk KeršnerAbstract:The paper is focused on the Mechanical Fracture properties of hardened cement mortars in which Portland cement is partially replaced by reactive admixtures. These properties are evaluated in relation to the mortars’ microstructure through the size and content of pores. The cement in the mortars was partially replaced by a diatomite that contains amorphous SiO2. The three-point bending Fracture tests were performed on beams with a central edge notch. The investigated Mechanical Fracture properties of the aforementioned cement-based composites included flexural strength, compressive strength, elasticity modulus, effective Fracture toughness and specific Fracture energy.
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Mechanical Fracture parameters of fine grain concretes with zeolite effect of composition and origin of cements
Advanced Materials Research, 2014Co-Authors: Hana Simonova, Zbyněk Keršner, Pavel Schmid, Pavla RovnaníkováAbstract:This paper introduces results of Fracture experiments on fine-grain concrete specimens prepared from CEM 42.5 R Portland cement of different origin (five Czech Republic localities: Mokra, Hranice, Radotin, Prachovice, Cizkovice), with natural zeolite admixture. Although the specimens were produced using the same type of cement, this paper shows that even small differences in chemical and mineralogical composition (caused by different origin) can result in changes of Mechanical Fracture parameter values.
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Effect of Cement Replacement by Zeolite on the Basic Mechanical Fracture Properties of Concrete: A Parametric Study
Advanced Materials Research, 2014Co-Authors: Pavla Rovnaníková, Pavel Schmid, Zbyněk KeršnerAbstract:This paper introduces the results of Fracture experiments on concrete specimens of different composition modified by zeolite (7.5 to 30 % by weight of cement dosage). It presents the determination and comparison of basic Mechanical/Fracture parameter values such as volume density, compressive strength, elasticity modulus, effective Fracture toughness and Fracture energy.
Feng Ren - One of the best experts on this subject based on the ideXlab platform.
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Implementation of the numerical manifold method for thermo-Mechanical Fracture of planar solids
Engineering Analysis with Boundary Elements, 2014Co-Authors: Huihua Zhang, Feng RenAbstract:Abstract The numerical manifold method (NMM) is developed to solve thermo-Mechanical Fracture problems in two-dimensional setting. The temperature fields are firstly determined through steady heat conduction analysis and then imported into the Mechanical simulation. The temperature and displacement discontinuities across crack faces are essentially captured due to the dual cover systems in the NMM. To account for the singularity of thermal flux and stresses at the crack tip, the associated asymptotic basis is adopted in the cover functions for thermal and Mechanical computation, respectively. The stress intensity factors are calculated with the domain-independent interaction integral. The accuracy of the proposed method is tested through several numerical examples including single, double and multiple-branched cracks and the results agree well the available solutions from the literature. The superiority of the NMM in the multi-field discontinuity modeling is preliminarily verified through the present work.
Pavel Schmid - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Fracture Parameters of Cement Based Mortars with Waste Glass Powder
Procedia Engineering, 2017Co-Authors: Hana Simonova, Pavla Rovnaníková, Zbyněk Keršner, Jana Zahálková, Patrik Bayer, Pavel SchmidAbstract:Abstract Glass is an amorphous solid substance with pozzolanic properties that can be used as a partial substitute for ordinary Portland cement (OPC) in cement based composites. In the research conducted for this paper, the PC was partially replaced by fine-ground waste laboratory borosilicate glass (in mixtures where 5, 10, 15 and 20% by mass was substituted). Beam specimens with the dimensions 40 × 40 × 160 mm were prepared from each mixture. After demoulding, the specimens were kept under standard laboratory conditions. Basic tests were conducted at the age of 7, 28, 56, and 90 days: the compressive ( f c ) and flexural ( f f ) strengths were determined according to the CSN EN 1015-11 standard. Specimens were also subjected to Fracture testing at the age of 28 days. The beam specimens with an initial central edge notch were tested in three-point bending. Load vs. displacement diagrams were recorded and modulus of elasticity ( E ), Fracture toughness ( K Ic e ) and Fracture energy ( G F * ) were determined. It was found, that strength increased with specimen age: at the age 28 days this increase was 12–33% in case of f c , and 6–15% as regards f f . The values obtained for almost all the parameters decreased with the increasing dosage of glass as a replacement for cement: compared to a reference composite this decrease was 22–40% in the case of f c , 24–28% for f f , 3–5% for E , 9–29% for K Ic e , and 30–50% for G F * ; exceptions were recorded for glass replacement doses of 5 and 10%, where increases of 2–6% for f c and 8–10% for E were obtained.
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Effect of Amorphous Silicon Dioxide Amount on the Mechanical Fracture Parameters of Cement Mortars
Solid State Phenomena, 2016Co-Authors: Hana Simonova, Pavla Rovnaníková, Zbyněk Keršner, Jana Zahálková, Pavel SchmidAbstract:This paper presents selected results from a study concerning Mechanical Fracture parameters related to the formation of the solid structure of cement mortars. The tested mixtures were composed of an invariable quantity of cement (type CEM I 42.5 R) and an increasing amount of amorphous SiO2 (marked with a P), or a variable quantity of cement replaced by varied quantities of amorphous SiO2 (marked with an N). It was decided that the consistencies of the fresh mixtures should be identical: to ensure this, the water-cement ratio was increased as necessary. Quantification of the Mechanical Fracture parameters of the studied composites (Fracture toughness, Fracture energy, compressive strength, modulus of elasticity) was performed via the evaluation of Fracture tests performed on beam specimens with an initial stress concentrator loaded in three-point bending. Subsequently, the results of the experiments in the form of load versus displacement diagrams were processed using the effective crack Fracture model and the work of Fracture method.
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Effect of Carbon Nanotubes on the Mechanical Fracture Properties of Fly Ash Geopolymer
Procedia Engineering, 2016Co-Authors: Pavel Rovnaník, Pavel Schmid, Hana Simonova, Libor Topolář, Zbyněk KeršnerAbstract:Abstract Fly ash geopolymer is amorphous aluminosilicate material which is considered as alternative to Portland cement concrete. One of the limiting factors of its utilization is an increased shrinkage and related deterioration of Fracture properties. This paper reports on a study of the application of multi-walled carbon nanotubes (MWCNTs) to improve the Fracture properties of fly ash geopolymer. The amount of MWCNTs added varied in the range of 0.05–0.2% of the mass of fly ash. Mechanical Fracture properties were determined via evaluation of three-point bending Fracture tests. Specimen response during Fracture tests was also monitored by means of acoustic emission, and this method was also used for the determination of cracking tendency occurring during the hardening process. Results show that the addition of MWCNTs increases the elastic modulus and compressive strength of fly ash geopolymer. However, basic Fracture parameters (Fracture toughness, Fracture energy) firstly decreased with very small addition of MWCNTs and were regained or slightly exceeded the reference values with higher amount of MWCNTs.
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Mechanical Fracture Properties of Cement Mortars with Diatomite in Relation to their Microstructure
Advanced Materials Research, 2015Co-Authors: Pavla Rovnaníková, Hana Simonova, Pavel Schmid, Ivana Havlíková, Jana Zahálková, Patrik Bayer, Zbyněk KeršnerAbstract:The paper is focused on the Mechanical Fracture properties of hardened cement mortars in which Portland cement is partially replaced by reactive admixtures. These properties are evaluated in relation to the mortars’ microstructure through the size and content of pores. The cement in the mortars was partially replaced by a diatomite that contains amorphous SiO2. The three-point bending Fracture tests were performed on beams with a central edge notch. The investigated Mechanical Fracture properties of the aforementioned cement-based composites included flexural strength, compressive strength, elasticity modulus, effective Fracture toughness and specific Fracture energy.
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Mechanical Fracture parameters of fine grain concretes with zeolite effect of composition and origin of cements
Advanced Materials Research, 2014Co-Authors: Hana Simonova, Zbyněk Keršner, Pavel Schmid, Pavla RovnaníkováAbstract:This paper introduces results of Fracture experiments on fine-grain concrete specimens prepared from CEM 42.5 R Portland cement of different origin (five Czech Republic localities: Mokra, Hranice, Radotin, Prachovice, Cizkovice), with natural zeolite admixture. Although the specimens were produced using the same type of cement, this paper shows that even small differences in chemical and mineralogical composition (caused by different origin) can result in changes of Mechanical Fracture parameter values.